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The Standard Unit Work Hours also provide a consistent base of reference so that estimators of every sector and office can communicate intelligently and effectively.

For excess excavated material haul, see Load, Haul and Dump activity Structures 0. It is a combination of machine and hand work Finish Grading for Process Areas – 0. Load, Haul and Dump — excess excavation 0. All unit work hours are based on average crew mixes and equipment types and sizes. For more definitive estimates, refer to Means, Richardson or other recognized estimating publications.

Unit work hours include time for equipment operators, laborers, Foreman and General Foreman. For medium soil common earth and loam , use work hour units as shown. For the cubic yardage of excavation that has a high water content, use a 1. This allows for excavated material that falls back into excavated site. Make appropriate adjustments to base work hour units when soil conditions become more densely filled with boulder material.

All sitework clearing based on onsite disposal see various categories for allowable distances. For any activities required which are not included in this section, see Means, Richardson or other recognized estimating publications. Block Outs 2.

Dowels For Construction Joints 0. Pipe Sleeves 0. All work hour units include unload, storage and handling to erection site. Any requirements for cribbing are not included. Formwork base unit work hours include fabrication, installation, stripping, oiling and cleaning.

All accessory labor is included in formwork and embedded item units. Formwork base unit work hours do not include any reuse of forms. Place and finish base unit work hours include a normal float finish.

Steel Trowel 0. Place and finish base unit work hours include normal pour methods. Special pour methods will require the addition of the following work hour units: Buggy Multiply standard units times 3. Install base unit work hours for grout includes the three main categories — cement, non-shrink and epoxy. Cement grout is basically cement, sand and water and is typically flowable, requiring formwork. Non-shrink grout is usually a dry pack type, non-flowable, requiring no formwork.

Epoxy grout is technically non-shrink but is flowable, requiring formwork. Trench Grating, The structural steel unit work hours are based on shop fabricated steel and field bolted connections. They include unload, storage and handling to erection site. For shop fireproofed steel, include weight of fireproofing with steel, to calculate total installed weight.

Anchor bolts and other embedded items are covered in the Concrete account. Take off handrails, ladders, stairways, grating and checkered plate separately from structural shapes.

Pipe rack steel must be taken off by weight category, separately from steel structures. For ladder takeoffs, need to add 3 LF for elevation level to be accessed. Primary and secondary members and bracing in a steel structure are to be a part of the takeoff. The unit of weight used in the charts is the 2, pound ton. Steel Sump Covers, etc. Fraser Drive P. Box Mesa, AZ or other recognized estimating publications. PUMPS Be sure to define mechanical completion. Work hours do not include maintenance required during storage, prior to erection.

Typically this is included in the Construction Indirects account, however some special cases may require direct work hours. If so, consult with a Fluor Daniel Construction representative. Grout work hours not included. Must be added to the appropriate Concrete account.

Sole plates not included. Must be added to the appropriate Concrete account Embeds. Work hour units include receiving, unloading shop fabricated sections of sizes within shipping limits, retrieval, hauling, rigging to position, shimming to elevation, leveling and aligning. Work hour units include field-engineering time to establish centerlines and bench marks.

Work hour units for Unlined category are based on fixed cone roofs. Work hour units for Glass Lined category include holiday testing. Work hour units for Buried category do not include excavation, backfill or concrete work as required. Work hour units do not include installation of foundation or anchoring system, support steel, piping, instrumentation or their connections. Field fabricated tanks are typically a subcontracted item.

For any activities required which are not included in this section, see Page, Richardson or other recognized estimating publications. Work hour units include receiving, unloading, retrieval, hauling, rigging to position, shimming to elevation, leveling and aligning.

Work hour units include time for opening manways and clean out. Work hour units are based on reasonable access to erection site. If erection is to be in a congested area, this should be evaluated separately and the work hours adjusted. Erection and dismantling time must be added for gin poles, if required. Work hour units do not include erection of ladders or platforms. Work hour units do not include field installation of trays, internals, packing or inspection.

Work hour units do not include crane set-up and removal time. Work hour units include receiving, unloading, retrieval, hauling, rigging, picking, setting, fastening and aligning of trays passed through manway. Work hour units include an allowance for installation of seal pan under bottom tray.

Work hour units do not include installation of vessel or other internals. Work hour units do not include time for opening manways and clean out. On new vessels, this time is included in the erection hours. On existing vessels, work hours must be added to cover these activities.

Work hour units do not include installation of scrubber or mist eliminator trayed sections. Hours for these applications should be calculated on a crew basis.

For tray adjustment, leveling and checking in the field, including tightening bolts and nuts, lost bolt replacement, etc. Hours for inspection include ease of access and required lighting. Catalyst loading is a critical activity that varies by process systems and by licensors. Clients typically handle this themselves but may delegate it to Fluor Daniel. When it becomes a part of our scope of work, consult with Process Engineering about any specific licensor requirements.

Work hour units include receiving, unloading, retrieval, hauling, assembling, erecting, aligning and anchoring. Work hours for Packaged Units include erection of prefabricated sections, shipped knocked-down, of sizes within shipping limits, inclusive of steel or fiberglass construction, fans, fan motors, controls, fill material, ladders and platforms, as required for a complete package.

Work hours for Field Erected include wood, steel or fiberglass frame, corrugated casing, grillage, fiberglass fan stacks, fiberglass fans, fan motors, controls, polyvinylchloride PVC plastic fill and stairs or ladders, as required for a complete assembly. Caution should be used when estimating field erection in this category. These work hours are not for detailed estimating but are instead provided as a general guideline and an aid for scheduling purposes.

For a detailed estimate, specific components, materials of construction and process requirements must be identified and labored accordingly. See note 9 for other sources. Work hour units do not include installation of concrete basin, support steel, piping, instrumentation, electrical power wiring or their connections.

Work hour units do not include installation of circulating water pumps. Work hour units do not include installation of water treatment system. Field erected cooling towers are typically a subcontracted item. Work hour units include receiving, unloading, retrieval, hauling, rigging to position, shimming to elevation, leveling, aligning and checking out of exchanger as required.

Work hour units in all categories are based on complete shop assembly. If field assembly is required, work hours should be calculated on a crew basis. Maximum range given for square feet of bare tube surface area within each category is based on industry standards. Work hours for Air Cooled Exchangers include shop-fabricated platforms and walkways for access to manifolds and motors. Work hour units do not include installation of foundation or anchoring system, support steel, piping, instrumentation, electrical power wiring or their connections.

Work hour units include receiving, unloading, retrieval, hauling, rigging to position, shimming to elevation, leveling, aligning, lubricating, bumping for rotation check and installing guards. Work hour units include receiving, unloading, retrieval, hauling, rigging to position, shimming to elevation, leveling, aligning and checking out of boiler as required.

Work hour units are based on saturated steam — to 1, PSIG. Work hours for Packaged Units include erection of prefabricated skids, of sizes within shipping limits, inclusive of boiler and trim; burner for either oil, natural gas or combination of both; windbox; forced draft fan assembly; firing and control system electric or pneumatic, single point ; flame safety system; stack; feed water pumps; ladders and platforms; insulation; and refractory, as required for a complete package.

Work hours for Field Erected include boiler pressure components; by-pass system; waterwall pressure components; downtake system; superheater pressure components; backpass system; reheater pressure components; economizer pressure components; soot blowers; inner casing; outer casing and framing; buckstays and trusses; monitor roof; weather roof; pressurized roof; all ductwork and hoppers; stacks; supports and guides; drip castings and furnace bottom seals; air preheaters; doors and mounting arrangements; ladders and platforms; pulverizers and feeders for coal fired ; burners and registers; seal and aspirating air; stokers; thermocouples; firing and operating controls; fans and drivers; postweld heat treating; insulation and insulation supports; and refractory, as required for a complete assembly.

See note 8 for other sources. Field erected boilers are typically a subcontracted item. Work hour units include receiving, unloading, retrieval, hauling, rigging to position, shimming to elevation, leveling, aligning and checking out of heater as required.

Work hours are applicable for gas, oil or dual-fired type. Work hour units do not include installation of ductwork, transition pieces, dampers, expansion joints or other related ancillary items, which may be purchased and shipped from the same vendor who supplies the Blower or Fan.

Work hours are applicable for either horizontal or vertical arrangement, as well as labyrinth, oil, contact or gas seals. Work hours for Centrifugal and Reciprocating Compressors include the installation of the compressor, base plate, couplings and driver. Work hours for Turbine Drives are applicable for either steam or gas.

Work hours for Packaged Units include erection of prefabricated skids, of sizes within shipping limits, inclusive of the compressor, driver, control panels, lube oil system, oil coolers, intercoolers, aftercoolers, etc.

Typically, 3, HP and below compressors can be delivered as a pre-assembled skid. Larger compressors would have to be delivered in multiple pieces, of sizes within shipping limits. Work hour units do not include installation of vendor furnished interconnecting piping, oil coolers, lube oil console, auxiliary pumps, filters, gear box, intercoolers, aftercoolers, intakes, mechanical silencers, acoustical barriers or other related ancillary items, which may be purchased and shipped from the same vendor who supplies the Compressor.

Enter the email address you signed up with and we’ll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Related Papers. Azania: Archaeological Research in Africa Cultural research management in Africa: challenges, dangers and opportunities.

The prehistory of the northern Mandara Mountains and surrounding plains. An ancient and common tradition: funerary rituals and society in Equatorial Guinea 1st – 12th century AD. African Archaeological Review Archaeological and ethnohistorical investigations along the southern fringes of Lake Chad, — Keywords: Central Africa, cultural heritage management, iron technology, food production, settlement systems. E-mail: smaceach bowdoin. Journal of African Archaeology Vol.

Lavachery, S. MacEachern, T. Bouimon, B. Gouem Gouem, P. Kinyock, J. Nkonkonda Introduction Heritage Management Considerations Over the last five years, archaeologists have car- The goals of the CEP heritage management pro- ried out a cultural heritage management programme in gramme have included: protection of the cultural Chad and Cameroon, as part of environmental manage- heritages of Cameroon and Chad; support for and de- ment work associated with the Chad Export Project. In too many cases, archaeological research on the continent is still carried out by Euro- This project has the potential for significant dam- peans and North Americans, with little African input or age to cultural resources in Cameroon and Chad, and control.

This situation can be traced in large part to a so has required a substantial cultural heritage manage- lack of resources available for the training of students ment programme, one of the largest archaeological ef- of archaeology, for control of national cultural heritage forts undertaken in this part of Africa to date.

Field- and for local programs of archaeological research and work along the pipeline right-of-way constituted a con- analysis, to be carried out in Africa by Africans. These tinuous archaeological transect across a large part of problems are compounded in regions where relatively Central Africa, allowing us to examine cultural variabil- little is known of the archaeological record in general, ity at a local scale over more than one thousand because that lack of background information makes kilometers in a variety of different environments, from very difficult the effective deployment of available ar- Sudano-Guinean woodland to tropical forest.

Prior chaeological resources. The transect also runs through the region impli- Cameroon and Chad, by providing training in cultural cated in the initial expansion of Bantu languages out of heritage management and by making possible research the core area of that language group in the Grassfields in regions unreachable without CEP logistical and tech- area of northwestern Cameroon, between Belabo and nical support.

This process, beginning perhaps years of active field research, as support for further post- ago, appears to have been of central importance to the graduate work will be provided for two of the African history of Africa south of the equator, but the linguis- archaeologists who have been involved on the project. This paper constitutes a complex, for a number of reasons. The project spanned preliminary report on the design and execution of the two countries, with construction and infrastructure de- CEP archaeological programme, as well as a brief de- velopment work carried out in parallel by three oversight scription of some of the results of our research to date.

Map of the pipeline right-of-way. Both countries legitimately wished to make archaeologists from Cameroon and from MacEachern. The national infrastructures with a number of Cameroonian archaeologists also em- available for cultural heritage management and archae- ployed and further trained by COTCO. MacEachern ology in the two countries are also quite different, with provided some initial support in Cameroon. One challenge for the archaeo- archaeological research to be undertaken oil fields logical programme as a whole has thus involved main- and km of pipeline in Chad, versus a variety of taining commonality in research design and method- support stations and approximately km of pipeline ologies across these national and bureaucratic bor- in Cameroon have led to somewhat different ap- ders, since the geographical scope of the research pro- proaches to cultural heritage management in the two gramme makes an integrated viewpoint particularly countries.

Initial archaeological research in Chad dur- valuable. Another challenge lays in ensuring the wid- ing and was undertaken by a Chadian ar- est possible involvement in the project of archaeolo- chaeologist Bouimon and an expatriate MacEachern gists from Chad and Cameroon, consistent with the working together. Bouimon and his students from the efficient and timely completion of project goals. Nkonkonda Research design were typically left for project archaeologists to study without interference by further pipeline construction The initial phases of cultural heritage manage- activities for several weeks, while sites uncovered by ment work for the CEP began along the pipeline right- trenching had to be examined and analysed much of-way in that country, through the period March — more quickly.

By the beginning of , monitoring was May, The main archaeological project has pro- exclusively associated with well-pad construction and ceeded in five phases, and was designed to comply with related activities in the OFDA in Chad. In addition, other elements of the Post-discovery site treatment was decided upon overall archaeological research effort have included: according to a prioritization system set up in collabo- a initial survey and mitigation work on fixed facility ration with the governments of Cameroon and Chad, sites in Cameroon that took place through late this prioritization then informing the Site Treatment OSLISLY et al.

Treatment vari- Pre-construction survey took place between ously involved no intervention that is, allowing sites March, , and February, , although not con- deemed not sufficiently significant to be impacted by tinuously through this period. This work began in along access routes in both countries. The terrain sur- October in Cameroon and is still continuing in veyed was in many areas exceptionally difficult, par- Chad.

This phase involved both a surface survey and an augering programme, with the latter adapted to Laboratory work and specialized analyses began local geomorphological conditions. There was no sys- in March , and is ongoing. This has included a tematic collection of artifacts during the pre-construc- substantial radiocarbon dating programme, with ap- tion survey; however, particularly significant objects proximately 90 dates obtained by the beginning of in imminent danger of destruction or disappearance The final stage of the CHM effort will be the were collected and catalogued.

This survey work con- preparation of a substantial publication on the ar- tinues periodically in the OFDA, as further oilfield de- chaeological programme. This is now in preparation. Archaeologists conducted construction monitor- Site distributions ing during all phases of project construction activities, including pipeline grading and trenching, between A total of archaeological sites have been lo- October, and the present.

Grading operations re- cated as a result of research between early and sulted in the removal of 20 to 50 cm of topsoil from the the end of Fig. Of these, have been found in ideal for the detection of archaeological sites and ar- Cameroon almost all on the pipeline right-of-way and tifacts.

The pipeline trench was dug to a depth of 1. Approximately two-thirds sites of the 1. Mitigation activities varied according sites discovered are surface scatters of different arte- to the phase of construction in which sites were un- fact types, including ceramics, lithics and iron-working covered. Archaeological sites uncovered by grading debris Tab.

Sites along the pipeline route. Two possible small mega- surface sites were designated as low priority. Upon further examination, it was deter- a significant number of which were located in the mined that these latter were stone outcrops of natural course of construction monitoring. These sites make origin and unusual configuration.

They have thus up the majority of sites accorded medium and high pri- been eliminated from the site inventory. Most of these ority designations and the majority of excavated sites. Site treatments. Circumstances of site discovery.

The higher frequencies of iron-working sites in Chad, or by intentional backfilling of the construction and of grinding hollows and lithic sites in Cameroon, trench.

Different site evaluation practises account for are particularly noteworthy. These may in part reflect most of the greater proportion of sites excavated in real differences in prehistoric activities along the pipe- Chad compared to Cameroon. Excavations have taken line route, but the larger number of relatively older place on 32 sites in Cameroon and to the beginning lithic sites in Cameroon may also be a reflection of dif- of on 39 sites in Chad.

In some cases, these ex- ferent erosional contexts. In Chad, most of the area cavations consisted of small test pits: in other cases, surveyed consisted of flat plain mantled with relatively they were substantially larger. Table 2 Cameroon Tab. These treatments varied according to compared to the savanna-forest mosaic and tropical the characteristics of the sites.

Monitoring during con- forest regions to the south, but also appears to reflect struction was applied to medium-priority sites when real increases in site densities in the deciduous further treatment was not deemed to be necessary, wooded savanna. Chadian site densities are not di- given information available at the time of discovery. In rectly comparable to those in Cameroon, since the fig- some cases, monitoring resulted in a site being ures for the former country include sites located dur- redesignated as high priority, with further treatment ing pre-construction survey in the OFDA, as well as applied.

In particular cases, impacts to sites could be sites found along surveyed roads in Chad. Sites lo- limited by narrowing the right-of-way around the site cated during road surveys are not yet included in Journal of African Archaeology Vol.

Estimated ages of sites, at time of site discovery. Cameroonian totals. The difference in site density is, Stone Age, Neolithic and Iron Age — to categorise however, still significant when only savanna and for- sites located in the course of the CEP archaeological est zones in Cameroon are compared, thus avoiding programme.

It is also the reason for some overlap in the age Also notable are a number of regions where site categories in use see Tab. Many of the sites located densities are considerably reduced Fig. Siddhanta, et al. Mannan and xylan have been found in red and green algae [65]. Alginic acid together with fucinic acid has been found as the major constituents of the cell walls of brown algae [66]. The amorphous or continuous matrix in the ultrastructure of cell wall is dissolved partly as the water- soluble fraction and partly in KOH solution as the hemicellulose fraction.

Mucilages D- glucose, D-mannose, D- and L-galactose, L-rhamnose, D-xylose, L-arabinose, D- glucuronic acid, D-galacturonic acid, L-fucose, D- and L-3, 6-anhydrogalactose, and 6-O- methyl-D- and L-galactose, sulphuric acid and pyruvic acid are the mainly constituents of the continuous matrix of cell walls [62, 67].

Glucose is the principal sugar, while varying proportions of rhamnose, fucose, ribose, arabionose, xylose, mannose and galactose are detected [68]. OH Fig. While brown algae have laminarin and manitol [69] and red algae have floridean starch as their main storage products [70]. Lipids Lipid is another important component in algae cell. Non-polar lipid monoglycerides, diglycerides, triglycerides, and free fatty acids are available as storage products.

The polar lipid phospholipids and galactolipids , like those of chloroplast of higher plants, are largely surfactant molecules which function both as structural elements and as metabolites in the photosynthetic organelles. The fatty acids of algal storage occur in range from C12 to C24, thus the common saturated straight chain fatty acids of vegetable oils such as lauric C12 , myristic C14 , palmitic C16 and stearic C18 are found in algae. It is rare reported the appearance of branched-chain fatty acid.

For Chlorella vulgaris, the lipid compounds were found as Monogalactosyldiglyceride, Digalactosyldiglyceride, Phosphatidylethanolamine, Sulphoquinovosyldiglyceride, Phosphatidylglycerol, Phosphatidylcholine, and Phosphatidylinositol.

Yoo, Chan et al. The structure of some lipids and fatty acids available in Chlorella vulgaris are shown in Fig. The crude protein figure is obtained by hydrolysis of the algal biomass and estimation of the total nitrogen which results in an overestimation of the true protein content because proteins are not the only source of nitrogen. However, normally protein is the main component of nitrogen fraction. Other protein estimation procedures are the method after Lowry and Biuret method which based on colour reactions with defined protein content without reacting with other nitrogen-containing compounds [61].

Therefore, the mass cultivation of microalgae requires carefully controlled conditions to produce optimal yield. The large-scale cultures are practically maintained outdoor because they have the advantage of available sunlight. These conditions are more appropriate for countries or regions with high solar radiation [61]. As the light source is the limiting factor, the artificial light sources like fluorescent lamps can be used in the pilot scale of microalgal cultivation [77].

For an efficient and economical photo-bioreactor, the selection of a light source as a key design challenge needs to consider both its spectral quality and intensity. The ability to absorb the solar energy of microalgae in mass cultivation is governed by several factors, including cell density, the length of the optical path of the system, the optical properties of the microalgal cells and rate of culture mixing [78].

Carbon dioxide fixation of microalgae is one of important factors for algae cultivation. Besides microalgae absorb free carbon dioxide from the atmosphere as a carbon source for photosynthesis from atmosphere, they can gain benefit from the fixation of CO2 in discharge gases from industries and power plants [79]. Normally the ability of diffusion rate of CO2 from the air into the water is too slow to replace the CO2 assimilated by rapidly growing algae.

Thus, the additional CO2 must be applied to cultivation medium to ensure satisfactory growth [80]. Nutrients are another factor for natural growth of microalgae. The main nutrients are nitrogen, phosphorus, and also minor nutrients as silicon, potassium, sodium, iron, magnesium, calcium and some trace elements such as copper, manganese, zinc [50]. After carbon, nitrogen is the most important nutrient contributing to the biomass production. Some algae can fix nitrogen from the air in the form of nitrogen oxides [81].

Under nitrogen limitation or starvation, there is the discolouration of the cells because the decrease in chlorophylls and the increase in carotenoids, also there is the accumulation of organic carbon compounds such as lipids and carbohydrates depending on the algae species [83, 84]. Although phosphorus in algal biomass is in small amount, it plays an important role as a growth limiting factor.

Three main designs of mass cultivation of algae can be classified as the open system, the closed system and co-process system utilising the carbon source from industrial waste. The carbon dioxide fixation is mainly from the atmosphere but an external CO2 supply can be installed to enhance the productivity.

The advantages of open ponds over closed system are that they are easily to construct and are low cost. Also, they need less energy supply by using natural light energy from the sun [86]. However, open ponds have some limitations which influence the production. The low CO2 diffusion, poor light utilization, and inefficient mixing cause lower productivity compared to the closed system. Moreover, due to the possibility of contamination or pollution from other algae and heterotrophs in open pond, suitable algal species should able to grow under highly selective environments [87].

The photo-bioreactor Fig. For indoor closed system, the artificial light sources are chosen at a suitable intensity. Co-process with waste treatment This system is to combine the algal cultivation with the carbon dioxide emission mitigation and wastewater treatments.

The major driving forces of these designs are the removal of CO2 from the atmosphere, capturing or utilizing the CO2 from fossil fuel combustion, and reducing the cost of nutrients. This algal biomass can be converted efficiently into biofuels with high productivity and low-cost cultivation [90].

While the CO2 fixation from the atmosphere is limited by low CO2 concentration in air, the mitigation of CO2 emissions from power plants achieves higher yield because of the higher CO2 concentration [91].

The benefits from utilizing waste water treatment process to algae production are the saving of nutrients cost and the minimizing of the freshwater use for algae cultivation. Some preliminary growth studies indicated both fresh water and marine algae have a potential in waste waters treatment [92, 93]. Microalgae have potential to remove nitrogen, phosphorus, and metal ions from wastewater [79] and CO2 from industrial exhaust gases; however these applications can only be achieved with a limited range of algae which are tolerant of the extreme conditions.

It is difficult to directly compare the performance characteristics of each mass cultivation system because they have different advantages and disadvantages. The choice of system depends on the production costs, value of the desired products, location and production quantity.

Hence, the production yield of microalgae is higher in comparison to terrestrial plants [95]. Thus, they can be produced all year round [97]. Figure 2. Biodiesel from algae oil has main characteristics quite similar to petroleum diesel [98]. Therefore, they do not compete with food production [97]. This process demonstrates an improved method for thermal conversion of ash-rich biomass as microalgal biomass and this process also presents the combination of microalgae into the bioenergy area effectively.

It is the integration of different processes such as algal biomass production, biogas units, pyrolysis processes, gasification processes and heat and power generation plants. Pyrolysis vapours are high quality and highly energetic, dust and tar free which are suitable to combine with heat and power CHP use after a gasification step.

Char produced from intermediate pyrolysis in BtVB process is suitable for further applications such as combustion, carbon sequestration and soil re-fertilisation.

The varied sized feedstock can be applied into intermediate pyrolysis; char can be separated from vapour easily. Moreover, various types of biomass may be introduced to this process. Ash- rich biomass, like microalgae, is also possible for use in the intermediate reactor. Exhaust gases from biogas plants and from gas engines are transferred to algae plantation as a fertilizer.

Apart from the raw microalgae biomass, algae with high oil content can be extracted by mechanical or solvent extraction for biodiesel production.

Although microalgae biomass is main feed, other regional feedstocks can be used together with algae during the winter time, when algae production slows down.

The BtVB process offers closed loops of fertiliser recycling. Residues from the biogas units may be used as a fertilizer in algae plantation.

The high ash content microalgae are processed through thermal conversion techniques and yielded a by-product with high ash content solid phase. The mineral matter in pyrolysis char is used for the energy crops as fertilizer and at least part of char may be extracted with water to recover mineral elements such as potassium, phosphates, nitrates and silica and then feed this mineral solution into microalgae cultivation system as a growth fertilizer.

Moreover, the aqueous phase of two-phase liquid products which is rich in inorganic matter may be added as a fertilizer to algae plantation and it can be considered as the closed water loop as well. In addition, the exhausts gases from engines are taken to algae medium as another source of fertilizer. Chlorella vulgaris have a simple life cycle with high reproductively rate. Their cells are divided into two or four non-motile daughter cells and enclosed for a little while within the parent cell wall [].

When the parent cell wall breaks, daughter cells are released into the medium. For decades, Chlorella vulgaris has been widely available in the food industry. They also show great potential for bioenergy applications due to their high growth rate and high oil content. They can be cultured under autotrophic and heterotrophic conditions []. The carbon dioxide concentration, nitrogen depletion, harvesting time, and also the method of extraction are the influences to the lipid content and the lipid compositions.

The lipid content in Chlorella vulgaris increases when the nitrogen concentration decreases and the CO2 concentration increases [73, ]. These proposed bio-sorption potentials of Chlorella vulgaris lead to their biomass production for biofuels combined with wastewater treatment as well as their solvent tolerance, acid tolerance and high CO2 concentration tolerance [] support their application to water treatments and CO2 fixation. It mainly consists of combustion, gasification, and pyrolysis process.

Each gives a different range of products and uses different equipment configurations operating in different conditions. Combustion process is well-defined technology and generates environmental concerns. Pyrolysis becomes an interesting conversion technology because its efficient energy production, easily stored and transported products in the forms of liquid fuels and solid char, and the wide range of produced chemicals [43]. Pyrolysis is thermal degradation in the absence of oxygen and it is a fundamental step in combustion and gasification followed by total or partial oxidation of the primary products.

High temperatures and long residence times are suitable for gas formation. The carbonisation process at low temperature and long residence times are the preferred conditions for char formation, whereas pyrolysis promoting the liquid production occurs at medium temperature with short residence times []. Based on the operating conditions, the pyrolysis can practically be divided roughly into three groups as conventional pyrolysis or slow pyrolysis, intermediate pyrolysis, and fast pyrolysis.

The key parameter classifying them is the residence time of solid phase within the reactor. Gas phase residence time for fast and intermediate pyrolysis is kept below two seconds. The proportion of gas, liquid and char products are controlled by the heating temperature and vapour residence times. The process parameters as well as heating rate also influence the subsequent behaviour of the products by secondary reactions.

Conventional or slow pyrolysis is characterized by a slow heating rate which leads to significant portions of solid product.

The residence time may last longer up to days at low temperature for producing charcoal or char mainly and is referred to a carbonization [33]. The characteristics of fast pyrolysis which are described by Bridgwater, et al. Chemical reaction kinetics, heat and mass transfer processes and phase transition play important roles in this complex conversion. If the purpose of the pyrolysis process is to obtain high yield of liquid products, a fast pyrolysis is recommended.

However the fast pyrolytic liquid products present in one phase include water, acids and tars. In the case of non-woody biomass grasses, straws, industrial residues, and agricultural residues , their pyrolysis process and products are far more complicated than those of woody biomass.

In addition, feedstock has to be well prepared with low moisture content. To minimize the exposure period at low temperature, the fast pyrolysis technique uses small particle biomass in a fluidized bed and a very quick heating at the surface of the particle in ablative reactor [].

These lead to the difficulties for separation solid phase from liquid and gas phases. The importance of char transporting with the outer screw as a heat carrier is to improve heat transfer and char also acts as a reforming agent during pyrolysis process. The figure 2. They also proposed the advantages of intermediate pyrolysis process in [, , ] that: 1 Its operating conditions preventing the formation of high molecular tars and offer dry char which is suitable for fertilisation or combustion further applications.

The removal water from the pyrolysis liquids is easy and end up with low water content oily phase. It is suitable for various feedstocks with different optimal residence time. The vapour phase from intermediate pyrolytic reactor has low ash content without dependence on ash content of starting biomass. This advantage offers the suitability of combining with a gasifier and also the applicability for ash-rich biomass such as microalgae biomass.

Furthermore, the internal pressure in this reactor is above atmospheric pressure, typically at least 50 or mbar over atmospheric pressure. This allows pumping pyrolytic vapour effectively into the gasifier. However, basically the reaction products are often lumped into three groups: gas, pyrolytic liquid and char [] or into two groups: volatile and char.

The weight loss of thermogravimetric analysis results from the overlapping of several reactions, thus they can be used for global mechanisms. The reaction mechanisms may be defined in three reactions which are 1 the primary pyrolysis or biomass devolatilization which is the main reaction to convert solid into permanent gas, condensable vapour and char; 2 secondary gas phase reaction of the release gas and tar species; and 3 heterogeneous reactions between solid and gas []. Moreover, typically the decomposition of lignocellulosic materials may be evaluated by two different models.

The first approach is to consider separated competitive reactions to describe the product distribution independent of the chemical compositions []. Each component decomposes at different rates and by different mechanisms. The volatile products from pyrolysis of biomass are mainly from the degradation of cellulose and hemicelluloses but lignin products dominate char yield [].

When the heating rate increases, the weight loss region of each component will be merged to each other and shift to higher temperature. At fast heating rate or high temperature, all component degradation occurs simultaneously.

In addition, the thermal behaviour of each component cannot be applied directly to biomass due to the difference of separation procedure, the presence of mineral matter, and component interaction.

Hosaya, et al. There were the significant interactions between cellulose and lignin. Lignin inhibited the thermal polymerization of levoglucosan but enhanced the formation of smaller molecules from cellulose. While cellulose reduced the secondary char formation from lignin and enhanced some lignin-derived product.

On the other hand, the interaction between cellulose and hemicelluloses was described as a weak interaction. Secondary reactions of primary tar vapours become active at high temperatures and sufficient long residence time.

Primary tar is the product from primary pyrolysis and after leaving from the solid phase, the primary tar vapour is subjected to secondary tar reactions [].

Tar is a very complex mixture of organic compounds such as phenolics, olefins and polyaromatic hydrocarbon PAH []. Tar formation can occur in the pores of the fuel particle as well as in the vapour phase and on surfaces of the fuel particles or other bed media. In addition primary volatiles may go through competitive pathways between char formation and cracking to form secondary volatiles []. Van de Velden, et al. Boroson, et al.

Main factors which need to be concerned for supporting secondary reactions are particle size, temperature, gas dilution, residence time and amount of fuel [, ]. Although there is numerous weight loss measurements of biomass pyrolysis, there is a difficulty to compare these results because thermal characteristics depend on the biomass species, the geographical origin, age, operating parameters, and the thermal analysis instrument.

Pyrolysis mechanism of cellulose Extensive studies on cellulose pyrolysis mechanism have been made over the past several decades. Another pathway is char and gas formation. Mamleev, et al. Thus, the gas formation competes with the char formation. Agrawal [] proposed a modified version of the Broido-Shafizadeh model, assuming that cellulose decomposes into gas, char and tar products. Although the Broido-Shafizadeh model and its modified models have been widely applied, they do not describe the details of decomposition.

Later, the recognition of hydraxyacetaldehyde or glycoaldehyde as a major product led to the extension in detail of the cellulose mechanism [, ].

Recently, cellulose decomposition models have been suggested to be more complicated pathways. Banyasz, et al. This model consists of two main pathways low temperature and high temperature pathway. Hydroxyacetaldehyde, formaldehyde and CO formation are token place at high temperature pathway involving an intermediate. While the formation of levoglucosan or tar at the low temperature pathway is reversible process.

Pyrolysis mechanism of Hemicellulose Compared to cellulose studies, there are considerably fewer papers dealing with the decomposition of the various hemicellulosic materials.

Due to the observed multi-peak of the derivative of the thermogram of hemicellulose decomposition, a three successive reaction chain model [27], a successive reactions model [], and a semi-global reaction mechanism model [] were proposed to describe the hemicellulose mechanism see figure 2.

From figure 2. The first stage is much faster than the second stage and the reaction time of these two stages decrease with temperature; while their ratio remains almost constant []. A large fraction of volatiles is produced in the first step due to the cleavage of the glycosidic bonds and the decomposition of side-chain structure. While the second slow degradation may be attributed to fragmentation of other depolymerised units [].

Pyrolysis mechanism of Lignin Due to the complexity of lignin and the difficulty in extraction, the study of pyrolysis mechanism of lignin is limited. Lignin pyrolysis is a radical process of the competition between initiation, propagation and termination reactions. The initiation reactions are strongly related to the bond energies of lignin structure. While the termination reactions need to be concerned the diffusive limitations to the effective radical collisions and recombinations [44]. Main products from lignin pyrolysis are phenol and its derivatives—methoxyphenol, guaiacol and cresol.

Also, methanol, formaldehyde, acetaldehyde, acetic acid and light hydrocarbons, as well as CO, CO2 and H2O are produced from pyrolysis of lignin []. The primary tar can occur the secondary cracking at the unsaturated side-chain and phenolic aromatic ring structure [] to produce CO, CH4, C2H4 and other light gaseous products [].

Both gauiacols and catechols can undergo secondary reactions with relatively independent of the presence of other molecular species and the residual polymeric material [, ].

Sharma, et al. The yield and characteristics of lignin chars depend on the pyrolysis conditions. The presence of inorganic matter, such as Na and K, lead to high char yield. As the pyrolysis temperature increases, the aromaticity and the carbonaceous mature of the char increases and hydrogen, as well as oxygen content of the char decrease. These products from the pyrolysis process can be used more readily and may be considerably more valuable than raw biomass.

The primary products can be used directly or can be converted further into even higher quality and valuable fuel or chemical products. The compositions and properties of the biomass-derived products depend on the pyrolysis conditions, i. Liquid products The present interest in liquid products from pyrolysis or other thermochemical conversion are driven by their high energy density which reduces the cost of storage and transport and their potential for further applications of heat and electricity generation and upgrading to premium-grade fuels.

The dark brown organic liquids from pyrolysis are called bio-oil, pyrolysis oils, bio-crude oil, wood oil, pyrolysis liquids, wood liquids, or wood distillates. The pyrolysis oil is composed of a very complex mixture of both aliphatic and aromatic hydrocarbons together with high amount of oxygenated hydrocarbon [, ]. Five broad categories of hydrocarbons detected in pyrolysis oil are hydroxyaldehydes, hydroxyketones, sugars and dehydrosugars, carboxylic acids, and phenolic compounds [33].

The complexity arises from the degradation of lignin which gives a broad spectrum of phenolic compounds. The properties of pyrolysis oil, such as poor volatility, high viscosity, coking, and corrosiveness are still the problems for using with the existing petroleum equipment and particularly in storage, there are some problems about phase separation, polymerization and corrosion of containers [].

The presence of a high content of oxygenated compounds in pyrolysis oil results in decreasing heating value, increasing uptake of water in the fuel, increasing the corrosiveness from acidic compounds [, ]. The moisture content of pyrolysis oil which is contributed from free water in original biomass and as a product of dehydration is much higher than that of fuel oil. This high water content causes the low heating value and affects viscosity and acidity as well as leading to phase separation and could affect subsequent upgrading processes.

To enable pyrolysis oil for industrial applications, the feedstock selection, pre-treatment, the improvement of pyrolysis unit, the upgrading of oil, the material selection and the ability to blend with other fuels should be taken into account [, ]. Solid products Bio-char is a pyrolytic product which is a carbon-rich solid with some hydrogen and oxygen, and also alkali and alkaline earth matter.

The operating conditions at a low temperature and low heating rate, the increasing particle size of the sample and the higher lignin content are promote the higher bio char yield []. Char can be activated by partial gasification with steam or CO2 to increase their porosity or by chemical activation with zinc chloride or phosphoric acid []. When the pore structure and surface area of char are appropriate, they can be prepared for activated carbon applications.

Activated carbon is widely used as an adsorbent in many applications such as toxic metal removal from water [], taste- and odour-causing compound removal [], removal or reduction of gaseous pollutants from the exhaust gas and removal of volatile organic compounds [].

Besides absorbent applications, char can be used for catalyst support and base material for fertilizers [] Gaseous products The main gases produced from pyrolysis are carbon monoxide, carbon dioxide and water.

Other products are methane, ethylene, ethane, propylene, propane and methanol. The product yields and gas composition depend on temperature, residence time, and heating rate []. However, most of bio gas production is focused on the gasification process whose operating conditions support gas formation.

The gaseous products with a low to medium heating value can be utilized into a combined heat and power CHP to produce electricity. Moreover, they can be upgraded to higher-value products such as methanol or gasoline but the conversion by gasification is more efficient. The study relates to following a reaction as a function of time with a suitable analytical technique by measuring the concentration of reactant or product during the progress of the reaction. The aims of chemical kinetics are not only to predict the rate of reaction from a function of state variables, but also to investigate reaction mechanism [].

For benefits to industries, the kinetic data of the main reactions have been used for plant design since the reaction rates control the productivity, the cost of the product, and the profit of the plant [].

During a chemical reaction, the concentration of reactants and products change in time. This relationship is based simply on the results of observation and experiment.

The powers in the concentration terms of equation above are called the partial orders of reaction. While the overall order of reaction or reaction order n is defined as the sum of p and q. Since Arrhenius discovered empirically that the rate constant is depending on temperature, the Arrhenius equation has been applied for kinetic studies [].

It is referred to a group of techniques in which some physical properties of the sample are continuously measured as a function of temperature, whilst the sample is subjected to a controlled temperature change.

By the nature of thermal analysis, the reactions are almost invariably heterogeneous reactions involving at least one initially solid reactant. For heterogeneous reaction, the concept of concentration of reactants or products does not play the significant role that it does in homogeneous reactions. Moreover thermal degradation kinetics of biomass can be carried out experimentally under either non-isothermal dynamic or isothermal static conditions [].

These different conditions are achieved by the controlled reaction temperature. In the non-isothermal analysis, biomass samples are heated with time according to an assigned heating rate. On the other hand, under static analysis, the experiments are carried on at constant temperatures. Practically the measurement is either under very slow heating rate to prevent from the gradients of temperature, or under a condition of very fast external heat transfer rates []. The measurement at high heating rate reduces the non-isothermal stage of heating-up phase but it is affected from heat transfer limitations when the sample temperature is not controlled accurately.

In the case of a slow-heating experiment, the weight loss during heating period cannot be neglected. However the non-stationary heat conduction causes the temperature gradient in the sample.

The difficulties to determine the real sample temperature in non-isothermal measurement influence the accuracy in formal kinetic parameters evaluation [28, 29]. Also, it is difficult to maintain the high heating rates that are achieved in pyrolysis reactor. In the last few decades non-isothermal methods have received more attention than isothermal methods. The main argument in favour of non-isothermal kinetic measurements compared with isothermal kinetic studies is their rapidity [32].

For fundamental studies, it was suggested that the non-isothermal kinetic data should be compared with the isothermal kinetic data for more accurate results [28]. The isothermal experiments are possible to separate unequivocally the temperature-dependent and concentration-dependent parts of a rate expression by experiments in which temperature and concentration are changing simultaneously.

To enhance the ability of isothermal analysis, the improvement of measurement apparatus to overcome the drawbacks of isothermal method need to be considered. Hence, substituting equation 3. They can be classified roughly into the differential method and the integral method. The differential method requires the derivative of the measured mass-temperature curve with high signal to noise ratio.

Smoothing can bias the calculation of kinetic parameters for a poor signal to noise ratio data. Integral methods overcome this disadvantage using the measured thermogravimetric data without differentiation.

Nevertheless, these methods are not applicable at very low or very high degrees of conversion [31]. Although thermal analytical methods provide valuable information on pyrolytic kinetics, they cannot provide the nature and amount of volatile products formed during the thermal degradation of materials. For this reason, Evolved Gas Analysis EGA has been combined with the thermal analysis techniques to get more information on thermal degradation. Obtained evolutions of volatile products lead to the prediction on product formation and product yield.

Apart from pyrolytic reactors in thermal analytic apparatus, several reactor designs have been developed for kinetic study at high heating rate and for eliminating the effects from operating condition and heat and mass transport phenomena. In principle, TG curve from one heating rates is sufficient for these calculations but in practice, the experiment should include three or more different heating rates measurements for an accurate statistical manipulation and solving the compensation effect [].

The feature of thermobalance should have the optimum position of a thermocouple to provide the actual temperature of the sample. Thus, its position should be located closed to sample. Also the temperature calibration is necessary to ensure that the equipment gives the actual temperature of the sample.

The feature of a horizontal thermogravimetric analyser is shown in figure 3. Conesa, et al. This could result in the apparent shift in biomass pyrolysis kinetics.

Due to the low heat transfer, kinetic has been measured at relatively low operation temperature instead of the heating time of a particle. If the heat transfer effects cannot be neglected, the chemical kinetic model should be considered together with the heat transfer equations []. The heat flow to or from the sample depend on whether the process is exothermic or endothermic. The integral or area of the DSC peak indicates the proportion of the transition heat for a particular reaction and the change in heat capacity involves the enthalpy change of the reaction [].

The apparent activation energy can obtain from the DSC data at different heating rates []. In the simultaneous analysis approach, two methods are employed to examine the materials at the same time. One of these methods can identify the volatile compound produced during the analysis simultaneously.

For combined analysis technique, more than one method is applied to analyse the sample and real time analysis is not possible. Radmanesh, et al. It was observed that the final total yield of gases increase but tar decrease by increasing the heating rate. Then they proposed a kinetic model which can predict the change of the gases yield at different heating rates.

Kinetic parameters were calculated based on parallel independent first-order reactions with a Gaussian distribution of activation energies. Each evolution peak was assumed to involve the respective precursor in the original biomass sample. Thus, each volatile species could evolve as one or more peaks independently. However, the model still needs further improvement by addressing the appropriate reaction mechanism, the mass influence, and the cross-linking competitive reactions.

Moreover, Banyasz, J. The kinetic analysis was based on the peak areas and the peak temperatures of calculated evolution profiles of main produced volatiles formaldehyde, hydroxyacetaldehyde, CO and CO2. Due to the difficulty to separate lignin from wood, they applied specific ion fragment range — u.

Bockhorn and co-workers [28, 30, ] researched the thermal decomposition of polymers under isothermal condition by similar technique applied in this work. The evolved gas analysis by means of on-line mass spectrometry provided the evolution data for calculating the formal kinetic parameters. A good agreement between the formal kinetic parameters from isothermal measurement and the ones from non-isothermal measurement by TG was reported [28]. In addition, an advantage from isothermal method is that the change in mechanism can be determined.

The Distributed Activation Energy Model DAEM has been used to model the evolution of individual pyrolysis product from different precursors in a set of simultaneous first- order reactions. Rostami, et al. Thermogravimetry is appropriate for thermal decomposition of biomass at low heating rate but under flash pyrolysis at high temperature, drop tube, tubular reactors, screen heater, radiant heating techniques, and fluidized bed reactors are more suitable than TG.

Heated-grid reactor has been used for studying pyrolysis kinetics of solid fuel materials at high heating rate []. The samples are placed on the wire mesh, which is electrically heated and is connected to a thermocouple for measuring its temperature.

The mass loss can be recorded by gas analysis [] or two measurements on a balance before and after the experiment []. Due to their operation at high heating rate, the weight loss during heating period can be minimized. Thus, the reactivity of sample is not changed before reaching a final temperature. The volatile products will be quenched at a cold gas phase to minimize secondary reactions. However this reactor needs to be used with some concerns.

A fine powder is typically suitable as the particle size of sample should be small enough to avoid the temperature gradient and the amount of sample for each run is limited because of the restriction of the thermal load on the grid. Also sample particles should be applied over the grid with the same small thickness layer evenly. Very small biomass particle about a few hundred micrometres are added together with inert gas stream or air to furnace at high temperatures.

Hence these small particles are heated up rapidly and this causes a short heat-up time compared to the reaction times which it can be determined as the isothermal during the degradation process. Downstream of the drop tube reactor is quenched with N2 and is collected and measured the weight [, , ]. This experiment is a time consuming procedure and introduces some errors from taking quenched products to the determination for the kinetic data. The large particle size of sample may cause a discontinuous feeding of the solid samples; while the small particle size may create a problematic pneumatic transport.

The thermal profile from this reactor is very narrow of isothermal conditions at only the centre of the reactor and lower temperature than the oven value due to the thermal dispersion from extremities effects. Also the gas flow rate may influences to the thermal profile. The residence time can be measured only with a rough precision and at room temperature []. Over the last five decades, the shock tubes have been applied to the study of aerodynamic and high temperature kinetic studies in both homogeneous and heterogeneous systems [].

The benefit on the kinetic study of the shock tube is the rate coefficient obtaining under diffusion free conditions because this reactor provides a nearly one-dimensional flow with instantaneous heating of reactants []. A shock tube consists of a uniform cross-section tube divided into a driver and driven sections. The driver section is high pressure with a low molecular weight gas and the driven section is filled with test gas at low pressure.

The particle is heated using the energy contained in pressurized gas. The mass loss is recorded using gas analysis []. A tubular reactor is a simple flow reactor operating at constant pressure. This reactor is a cylindrical pipe of constant cross-section where the feed enters at one end and the product stream leaves at the other end. The lack of providing of stirring prevents complete mixing of the fluid in the tube which is the opposite assumption from that of the ideal stirred tank reactor.

Composition is the same at all point in a given cross-section but changes along the axial coordinate of the tube. The literatures on using tubular or closed-tubular reactor [] for thermal degradation and kinetic studies have been published in bioenergy research []. The progress of reactions can be measured from the withdrawn sample from the bed at different times.

The feature of this reactor that biomass particles are mixing with bed material restricts the determination of decomposition rate at short residence times []. The produced gas flow can be analysed by evolved gas analysis connection, i.

In addition, there are other types of reactor which have been facilitated in the thermal degradation researches, such as laminar entrained flow reactor [], plasma pyrolysis [, ], closed loop-type reactor [28].

These factors on the thermal degradation kinetics are linked. At first in vaporization step, the flow of water vapour is controlled by diffusion and convective and diffusive transport. Then the chemical reactions of pyrolysis process occur. The heat changes from pyrolysis reactions and phase changes cause the temperature profile inside the particle. Volatile and gaseous products migrate from the solid across the heat-exposed surface and involve the heat transfer phenomena.

Three combined mechanisms of heat transmission inside the pyrolyzing solid are the conduction through the solid particle, the radiation from the pore walls, and the transmission through the gas phase inside the particle pores. After volatiles leave the solid phase, char is formed by the change of physical structure of the reacting solid to develop a network of cracks, particle volume shrinkage, surface regression, and swelling [20, 23, ]. Biagini, et al.

For all materials and using all methods, the activation energy at low heating rate was found higher than that at high heating rate with respect to overall values. Haykiri-Acma, et al. Obviously, the higher heating rate shifted the main peak of DTG profile to the higher temperatures.

It could be explained by the heat transfer inside the biomass particles. At low heating rate, a number of peaks can appear individually in small peaks. When heating rate go higher, some of them overlap and form a unique large peak. The induction period at the initial stage of the weight change data from isothermal measurements shows the low velocity of decomposition which is attributed to the heating of the particle.

The large particle size prolongs the induction period due to the longer time of heat transfer from outside to particles and within particles. For small sample size, the large surface area improves heat and mass transfer. Thus, its fast heating rate causes more light gases and less char and condensate formation [].

The uniform radial product distribution would result from the neglected temperature gradient between the surfaces and centres of the small biomass particle []. On the other hand, the large particle size prolong the resident time of volatile molecules from primary reactions inside the solid particles that enhances the secondary reaction [].

These inorganic elements are available as oxides, silicates, carbonates, sulphates, chlorides and phosphates []. Some of these inorganic elements act as a catalyst affecting the rate of degradation []. Results from studies on the effect of catalyst informed the enhanced formation of char and gaseous products and inhibited formation of the volatile products.

Also, inorganic contents promote secondary reactions which break down higher molecular compounds to smaller ones.

Several inorganic matter have been studied their catalytic effect on degradation. Potassium K was found to shift the pyrolysis to a lower temperature and lower activation energies []. In addition, sodium Na is another inorganic matter which was reported for its catalytic influence []. Blasi, et al. The potential role of varied systematic errors in temperature measurement among the various thermobalances and the compensation effect are the reported explanations of these disagreements.

It has been recognized that different sets of kinetic parameters can describe similar conversion degree curves once a kinetic model has been selected but it is not necessarily that all of them have the same grade of accuracy [].

Flynn [] reviewed that either the result of scatter of the experimental data, misapplication of kinetic equations, or errors in the experimental procedures can be the reasons for the presence of kinetic compensation effect when studying identical specimens under the same conditions. Agrawal [] also concluded that the inaccurate temperature measurement and large temperature gradients within the sample cause the compensation behaviour in the pyrolysis of cellulosic materials.

Recently, Wang, et al. Moreover, [], [] and [] reported evidence of compensation effect on their studies. There is the competition between the reaction heat demand and the heat demand for the limited heat supply. The factors affect to the thermal lag problem are heating rate, the placement of the thermocouple, the size of the sample, the composition of the carrier gas, and the endothermicity of the reaction [, ].

As external heating rate increases or low heat-transfer coefficients, the measured temperature may slightly higher than actual temperature and the effect on thermal lag increases []. Thermogravimetric analysis is the most widely used technique for the study of cellulose pyrolysis. The understanding of total mass loss for global pyrolytic kinetics is generally intended to predict the overall rate of volatiles release from the solid and it can be applied to mechanism study.

The isothermal kinetic studies and high heating rate experiments showed the lower activation energy than the experiments with slow heating rates. Serious heat transfer limitations and associated temperature measurement problems were identified as the cause of this variation of kinetic parameters. The decrease of Ea and log A values at higher heating rate was attributed to the higher impact on thermal lag. Table 3. More recently, Carpart, et al. From isothermal measurements, it showed the kinetics of nuclei-growth which was represented by the models of Avrami-Erofeev A-E and of Prout-Tompkins P-T type.

From non-isothermal measurement, they simulated a model with two parallel reactions, one was related to the bulk decomposition of cellulose and another was related to the slower residual decomposition.

Approximately the activation energy for the decomposition of hemicelluloses is lower than that of cellulose but it is higher than the activation energy of lignin []. Most of kinetic studies on hemicellulose pyrolysis carried on the non-isothermal condition by thermogravimetric analyser. The two-step process from TGA curves has been observed [, ]. Hemicellulose presented two steps of decomposition.

The difference in kinetic parameter values from different wood influences from the compositions of wood. The reported kinetic parameters of hemicelluloses as a main component in wood have been published from several researchers. Some published kinetic parameters of hemicellulose are presented in table 3. Cozzani, et al. A simple first-order kinetic model was applied to calculate its activation energy The majority of the available kinetic studies point to a poor fit of simple reaction models in the whole range of conversion and the change in mechanism cannot be detected.

The discrepancy in the reported activation energies of hemicelluloses can be explained by the difference in sample composition, experimental setting, the mathematical method to analyse data, and the possible interference of the lignin decomposition []. The kinetic parameters obtained from simple model tend to be lower than those from the complex models.

In the review of Ferdous, et al. Recently, Murugan, et al. The causes of this wide range of reported activation energy are operating conditions temperature, heating rate, and the nature of carrier gas and the nature of lignin composition, functional groups, and separation method [49, ].

In addition, Jiang, et al. They found activation energies of lignins were in the range of Ferdous, et al. The complex process of lignin pyrolysis was analysed by the distributed activation energy model DAEM. The small activation energy obtained from the fixed- bed reactor indicated the presence of mass and heat transfers effect. The proper understanding of their thermal properties and reaction kinetics are crucial for the efficient design, operation, and modelling of the pyrolysis, and related thermochemical conversion systems for algae.

Like the kinetic studies of lignocellulosic materials, most of kinetic studies in algae are based on the non-isothermal condition assessed by thermogravimetric analysers. Peng, et al. They observed that the devolatilization consists of two main temperature zones, lipid decomposition and other main components i.

The microalgae were devolatilized at lower temperature range than those of lignocellulosic materials, which was economically feasible.

Also, Peng, et al [] compared the kinetics of Spirulina platensis and Chlorella protothecoides microalgae. As the heating rate increased, the reaction rate in the devolatilization stage increased but the activation energy decreased.

The reported activation energy for Chlorella protothecoides was Shuping, et al. The iso-conversional method and the master-plots method were used for kinetic analysis.

The master-plots method gave an Fn model nth-order as the most probable reaction mechanism. While Li, et al. In both of these articles, researchers suggested that the thermal behaviour was influenced by compositions of biomass.

The relationship between the apparent activation energy and pre-exponential factor could be explained by the kinetic compensation effect. It is often expected to describe a solid state decomposition by a single set of kinetic parameters and the isothermal and non-isothermal values are expected to be equal. However, the nature of solid state processes is the multi-step reactions which contribute to the overall reaction rate that can be measured in thermal analysis.

The complexity of thermal decomposition in solid samples is a cause of the variation in reported data. Moreover, there are several approaches to evaluate kinetic data. The model-fitting approach from a single heating rate is considered to give highly uncertain values due to its dependence on both the temperature and the reaction model.

Apart from the difference in computational methods, the kinetic parameter depends strongly on the experimental conditions, such as the inert flow rate, temperatures, atmosphere, and sample size. The difficulty to measure a real sample temperatures and heating rates also cause the discrepancy in kinetic values. Thus, the kinetic study should be carried out at kinetically controlled conditions to minimize the uncertainty from experimental conditions and also the evaluation should be taken into account the multi-step mechanisms of the solid state decomposition.

Proximate and ultimate analysis together with the thermal behaviour analysed by thermogravimetric technique of these three materials are given and discussed based on their application in thermo-chemical conversion process.

Whatman No. It is difficult to obtain a commercial hemicelluloses sample, thus xylan has been widely used as a representative of hemicelluloses of hardwood in pyrolysis study [, , , ]; although different physical and chemical properties have been found depending on the source material and production method.

An alkali lignin powder Sigma Chemical Co. All samples without further treatments were stored in desiccators until use. Ten milligrams of sample were used for each measurement. Each measurement was repeated three times to check the reproducibility. The results of proximate and ultimate analyses of three lignocellulose derived materials are given in table 4. This lignin sample was identified as alkali lignin which was isolated with alkali and precipitated by mean of mineral acids.

Thus, ash content in this kind of lignin is at high level. From elemental analysis, the lignin structure consists of a high level of carbon and low oxygen content compared to those of cellulose and hemicelluloses. All samples contain very low nitrogen content which leads to low nitrogen oxide gases produced. Lignin was the only material showing the sulphur content which was considered from the production process. Sample and furnace temperature detectors of TG were calibrated by three standard metals Indium, Zinc and Aluminium before starting experiment to minimize the error from thermal lag.

The measurements of each sample were checked for the reproducibility by repeating three times. The thermogravimetric data of cellulose, hemicelluloses and lignin obtained by recording the history of weight loss of the samples as well as their derivative curves at different heating rates are presented in Fig.

Moreover, Fig. This effect is mostly related to the difference in heat and mass transfer of the sample particles externally and internally.

At lower heating rates, sample particles were heated slowly, leading to a better and more effective heat transfer to the inside of the particles.

As a result of the more effective heat transfer, the sample decomposes promptly, enhancing the weight loss. Hence, at lower heating rates, more volatiles were produced than at higher heating rates. On the other hand, at higher heating rates, the temperature difference inside a sample particle is enhanced and then the residue at the end of the pyrolysis increased. The shift of thermograms toward high temperature as the heating rate increases can be observed clearly in every sample.

Table 4. The increase of reaction rates were at the same ratio with the increase of heating rates. The reason for this shift is also from heat transfer effect at high heating rate, the minimum heat required for depolymerisation is reached at higher temperature because of the less effective heat transfer than the low heating rate does.

Hemicellulose started decomposing at a lower temperature but the temperature range on decomposition was wider than did cellulose. Hemicellulose has the highest reactivity for thermal decomposition because its structure is random and amorphous with less strength.

In contrast, cellulose is a crystalline, long chain polymer of glucose units without any branches supporting the hydrogen bonding. Thus, more energy is required for depolymerisation of cellulose polymer as the main mass loss stage of cellulose comes later than that of hemicellulose.

Lignin has heavily cross-linked structure of three basic kinds of benzene-propane units. Hence, the structure of lignin results in high thermal stability and is difficult to decompose. Volatiles produced from lignin occurred from the breaking down of different functional groups with different thermal stabilities. This difference leaded to a broad range of decomposition in lignin []. Alkali lignin had a high ash content which influences its pyrolytic behaviour.

This difference is influenced from their different chemical structures. The thermal decomposition characters of each sample can explain the multi-step decomposition in biomass.

Characteristics of these basic materials influence the mechanisms and kinetics of biomass decomposition. To understand the very complex pyrolytic behaviour of biomass, those of cellulose, hemicellulose and lignin are fundamental and important. Further in this present study, these promising representatives of lignocellulosic main components will be used to analyse their formal kinetic parameter of pyrolysis process in Chapter 7.

It is well-established that the main components lignocellulosic biomass are cellulose, hemicelluloses and lignin, while those of algae can be classified simply as protein, carbohydrate and lipid which present at various proportion depending on species, cultivation condition and harvesting process.