Design of Gasifier for the Production of SYNGAS from Wood Biomass

19 | Page

Contents1-Abstract .. 22-Introduction[l]:-23-Process selection44-Equipment selection85-Mass balance on gasifier116-Design of the Circulating Fluidized Bed Reactor147-Fluidization208-Design of the Fluidized bed229-Conclusion:-2410-References:-25

1-Abstract Gasification of different fuels got attention in Pakistan due to fluctuation in natural gas supply. The production of synthetic natural gas, hydrogen production for ammonia synthesis from natural gas also affected. To maintain the production of these gases, there are different ways like pyrolysis, combustion, or gasification of Coal, biomass or wood. These methods are carried out in different reactors like fluidized bed, entrained bed and fixed bed reactor in which there are different medium such as by introducing the steam, air or oxygen. In this paper, we are going to gasify the wood by introducing the steam in the presence of Nickel-Olivine catalyst. We study the different types of reactor and will design the circulating fluidized bed which is, after making comparison of number of reactors, in the range of our desired capacity (20MW-100MW) at the temperature 9000 C and pressure 1 Bar for low heating value of wood rather than higher heating value and 90% of conversion. The main objective is the design of fluidized bed at superficial velocity and study of porosity and sphericity of wood and Nickel-Olivine catalyst.

2-Introduction[l]:-Gasification is such a chemical process that converts carbonaceous materials into chemical feed stock or gaseous fuel. Carbonaceous fuel may be any biomass. Basically gasification is a process of partial combustion of biomass resulting in the production of carbon monoxide, hydrogen and traces of methane which are combustible gases. . This mixture is called producer gas or syn gas or synthetic gas. The purpose of gasification in not just conversion, production of chemicals is also have main importance of gasification. In fact the first application of gasification was to produce charcoal for iron ore reduction and not for gaseous fuel in 4000 B.C.E.On the other hand the producer gas which is produced can be used in number of processes like,

1. Substitute for furnace oil2. Run internal combustion engines3. Chemical feedstock for industries4. In producingsynthetic petroleumvia the FischerTropsch process5. Used for the production of synthetic natural gas (SNG), ammonia and methanol

One also main application of gasification is that there is a problem of using solid fuel, like wood which is used in boiler, to produce heat by combustion but this equipment is very expensive and very low energy recovery. Hence it is very essential to convert wood into gaseous fuel by gasification. . Hence it is also a big application of gasification.

2.1-Historical Background[m]:-

First gasification process is investigated by Thomas Shirley. , who in 1659 experimented with carbureted hydrogen which was the previous name of methane. Then with the passage of gasification milestones different experiments and discoveries were made. First commercialGasification plant in United StatesRobert Gardner: First gasification patentFourcroy: Water gas shift reactionSiemens gasifier:First successful unitWinkler: Fluidized bedGasifier

1788 1801 1861 1926 AdvancedGasification &Renewable energyProjects

1997 2001In Pakistan energy crisis is very severe. In every year energy demand is increasing by 8%. From recent last twelve years, and this trend is continuous. Our 50% yearly export earning has been consumed in oil import bill. Federal minister of information Senator Pervez Rasheed said.

Small and medium enterprises (SMEs) and also other industries could use wood gasification to generate their own electricity and this would help them to avoid the negative impact of the power crisis,

3-Process selection3.1-Selection of fuel:-A biomass fuel is much closer to the hydrogen and oxygen corners compared to coal. It means, in biomass there is more hydrogen and more oxygen than in coal. Lignin have lower oxygen and higher carbon contents. Peat is in the direction towards the carbon corner, which means it is like a high-carbon biomass. Coal resides further towards the carbon corner and lies close to the oxygen, it is very low in oxygen and much richer in carbon. Anthracite resides furthest towards the carbon corner because it has the highest carbon contents. Carbonization or slow pyrolysis moves the product towards the carbon through the formation of solid char; fast pyrolysis moves it towards hydrogen and away from oxygen, which implies higher liquid product. Oxygen gasification moves the gas product toward the oxygen corner.Steam gasification takes the process away from the carbon corner. The hydrogenation process increases the hydrogen and thus moves the product towards the hydrogen.Here we want to produce syngas (CO+h2) so we need biomass for the production and naturel sources like crude oil, coal and natural going to be end.Biomass like municipal solids waste, cow dung for the production of methane are needs to be utilized for replacement of natural fuels. In Pakistan there is much necessary to install the technology for the production of biogas, biodiesel and bioethanol for the decomposition of biomass and also for the replacement of natural fuels.3.2-Biomass conversion:-There are two different routes of the conversion of bio mass

3.2.1-Biochemical route1) Digestion Anaerobic Aerobic 2) Fermentation 3.2.1.1-Digestion:- The major products of anaerobic digestion are methane and carbon dioxide.Aerobic digestion, is also a biochemical breakdown of biomass, it takes place in the presence of oxygen. It uses different types of microorganisms that access oxygen from the air, producing carbon dioxide, heat, and a solid digestate.3.2.1.2-Fermentation:- In fermentation, part of the biomass is converted into sugars using acid or enzymes. The sugar is then converted into ethanol or other chemicals with the help of yeasts. The lignin is not converted and is left either for combustion or for thermochemical conversion into chemicals. Unlike in anaerobic digestion, the product of fermentation is liquid.

3.2.2-Thermochemical routeThere are four different processes for the thermochemical conversion of biomass which are Pyrolysis Gasification Supercritical Water Oxygen Steam Combustion Liquefaction

3.2.1-Combustion:-Combustion represents perhaps the oldest utilization of biomass, given that Civilization began with the discovery of fire. The burning of forest wood taught humans how to cook and how to be warm. Chemically, combustion is an exothermic reaction between oxygen and the hydrocarbon in biomass. Here, the biomass is converted into two major stable compounds: H2O and CO2. The Reaction heat released is presently the largest source of human energy consumption, accounting for more than 90% of the energy from biomass.3.2.2Pyrolysis:-Unlike combustion, pyrolysis takes place in the total absence of oxygen, except in cases where partial combustion is allowed to provide the thermal energy needed for this process. Pyrolysis is a thermal decomposition of the biomass into gas, liquid, and solid. It has three variations: Torrefaction, or mild pyrolysis Slow pyrolysis Fast pyrolysisIn pyrolysis, large hydrocarbon molecules of biomass are broken down into smaller hydrocarbon molecules. Fast pyrolysis produces mainly liquid fuel, known as bio-oil; slow pyrolysis produces some gas and solid charcoal.Torrefaction, which is currently being considered for effective biomass utilization, is also a form of pyrolysis. In this process (named for the French word for roasting), the biomass is heated to 230 to 300 C without contact with oxygen. The chemical structure of the wood is altered, which produces carbon dioxide, carbon monoxide, water, acetic acid, and methanol. Torrefaction increases the energy density of the biomass. It also greatly reduces its weight as well as its hygroscopic nature, thus enhancing the commercial use of wood for energy production by reducing its transportation cost.3.2.3-Gasification:-Gasification converts fossil or non-fossil fuels (solid, liquid, or gaseous) into useful gases and chemicals. It requires a medium for reaction, which can be gas or supercritical water (not to be confused with ordinary water at subcritical condition). Gaseous mediums include air, oxygen, subcritical steam, or a mixture of these.There are three major motivations for such a transformation: To increase the heating value of the fuel by rejecting noncombustible components like nitrogen and water. To remove sulfur and nitrogen such that when burnt the gasified fuel does not release them into the atmosphere. To reduce the carbon-to-hydrogen (C/H) mass ratio in the fuel.3.2.4-Liquefaction:-Liquefaction of solid biomass into liquid fuel can be done through pyrolysis, gasification as well as through hydrothermal process. In the latter process, biomass is converted into an oily liquid by contacting the biomass with water at elevated temperatures (300350 C) with high (1220MPa) for a period of time.

4-Equipment selection4.1-Gasifiers:-A reactor in which the reactions of gasification occur is called as gasifier. Gasifier/Equipments for the purpose of gasification exist in many forms, which are dependent upon the type and size of feed, operating pressure and temperature and the medium which is being used for gasification. Following are the technological options for Gasifiers that can be applied for the gasification purpose: - [5] [19]A. Fixed(Moving) bed Gasifiersi. Updraft/ Countercurrentii. Downdraft/ Co-current iii. Cross draftB. Fluidized bed GasifiersC. Entrained flow GasifiersD. Allothermal GasifierE. Supercritical Gasifier4.1.1-Fixed Bed Gasifier [18]:-The feed and the gasifying medium i.e. hot air or steam is entered into the gasifier from two different openings thus forming three types:

4.1.1.1-Updraft/Countercurrent Gasifier [6]:-In this type, the feed i.e. biomass, is introduced from top side opening and the medium of gasifying i.e. hot air or steam is entered from the lower side opening of the gasifier.[3][4] As the entering feeds are preheated by the outgoing hot SNG and hot ash, the efficiency is relatively high and the leaving temperature is lower. 1-2 hours residence time is required for this type of the gasifier. Gas

4.1.1.2-Downdraft/Co-current Gasifier [6]:- When the feed and the steam are entered in the gasifier from the same side and move in the same direction, the gasifier is known as co-current gasifier. Here the ash produced is also burned (cracked) as the SNG is being passing through the combustion zone.

4.1.1.3-Cross draft Gasifier:-Feed is entered from the top side while the gasifying medium is introduced from any other side other than lower and upper side. In this type the height of the gasifier is much reduced, While pressure drop is high than others.Mixing and heat transfer are poor in all these three types of gasifiers so that fuel, temperature and gas mixtures are not uniformly mixed. Agglomeration of fuel is also a drawback in these gasifiers.

4.1.2Fluidized Bed Gasifiers [6] [9] [18]:-This is the type in which the feed is fluidized by the help of gasifying medium. During the operation, the steam jet is injected which pushes up the biomass i.e. suspending the feed. A clean gas which is then nitrogen free is obtained. They are also known as CFBG (Circulating Fluidized Bed Gasifier) /FICBG (Fast Internally Circulating Fluidized Bed). [14][15] Velocity range for these gasifiers is 3-10m/s. When velocity is lower than this range but still high, then the bubbling fluidized bed is formed instead of the circulating fluidized bed.[11][12]

4.1.3-Entrained flow Gasifier [6] [18]:-These gasifiers are operated at relatively high temperatures and deal with small size particles close to 0.1 mm. Since particles are in small sizes and they are burned quickly hence residence time is lower for these gasifiers. Instant burning of small particles causes the formation of SNG and the methane is not produced in these gasifiers.

4.1.4-Allothermal Gasifiers:-Twin bed gasifier is a simple example of this type. When feed is not heated directly i.e. heat is provided either by another medium or by heating of the walls of the gasifier, then the indirect gasification occurs which is also known as the Allothermal gasification. Heat loss is greater in this type due to which thermal efficiency is also lower.4.1.5-Supercritical Gasifier:-When moisture contents are higher in the feed then super critical gasification is employed which is the result of supercritical properties of the water at extreme high pressure and temperature. Pressure may range between 30 MPa to 50 MPa and temperature may be up to 500 C. in this process, since water i.e. steam is being used in greater quantity so the resultant SNG gas contains Carbon Dioxide in large amount and methane and Carbon Monoxide are less in amount. 4.2-Selection of Gasifier for Gasification of wood:-Gasifiers are selected for their job according to the size of the feed. Entrained flow gasifier is used for very low size feed. Similarly fluidized bed reactor is used for larger size particles with range from 3-10 mm size. Moreover, temperature range for former is 1200-1500 C and for latter is 750-900 C. A graphical relationship between different types of beds and their capacity is shown here. [19]Since we are taking wood as feed and the capacity that we have selected is 100MW so according to above figure we have equal opportunity to select fluidized bed and entrained flow gasifier. Efficiencies based on LHV are 54%, 58% and 67% for entrained flow, CFB and Allothermal gasifiers respectively. [1]Fluidized bed is important because of its well mixing and uniformity in temperature. [16] This temperature uniformity is the property which don`t permit the fuel to agglomerate. Operating temperatures for the entrained flow gasifiers are relatively high and also they require very small size feed and our feed size comes in the range of the fluidized bed. Hence fluidized bed is chosen for this project.Fluidized bed depending on the velocity of the entering fuel, can be a bubbling fluidized and circulating fluidized bed gasifier. [12] Lower velocity causes fluidization but only bubbles are formed but within the range of 3-10m/s velocity, the circulation is involved i.e. circulating fluidized bed. Hence Fast Internally Circulating Fluidized Bed is chosen for this project.

5-Mass balance on gasifierCapacity 100 MW Low eating value of wood can be calculated by this formula 5.1-Low heating value:-LHV=HHV-Hg {9(fraction of hydrogen)-(fraction of moisture contents)} [a]5.2-Composition of elements:-Ultimate Analysis (Dry Basis) of Some Biomass [b]Fuel Percentages

Carbon

50.6

Hydrogen

6.0

Oxygen

0.3

Nitrogen

0

Sulfur

41.7

Ash

1.4

High heating value

19958kj/kg

5.3-Basic assumptions:-Parametersvalues

HHV19958KJ/kg

Hg(latent heat of steam)2260kj/kg

H(fraction of hydrogen)0.06

M(fraction of moisture contents)0.015

LHV= lower heating value of woodFraction of hydrogen in wood =6%Moisture contents = 15%So, we getLHV=17991kj/kg

For 100 MWWe know that1MW=106 jAnd for 100MW100x106 jouleBase; 1kg

Steam=3.8605kg

Reactor

Syngas =4.9635kgFeed=5.515kg

Ash=0.077kg

Lower heating value is 17991x103 for = 1kgFor 1x108 j feed is required = (1/17991x103) x1x108Which is Feed of wood=5.515 kg

Steam required for 1 kg of wood for gasification = 0.7 kg [c]Steam required for 5.515 kg of wood for gasification = 0.7 x 5.515=3.8605 kg of steam

1 kg of produced 0.662 kg of syngas[d] which that syngas production =0.662 x 5.515 =3.651 kg of syngas

5.4-Average density of syngas:-Average density=0.95kg/m35.5-Volumetric flow rate:-V=mas flow rate/average density =3.651/0.95 =3.84m3/s5.6-Ash contents:-Ash contents= (%age fraction of ash) (total mass of feed)= (1.4/100) x (5.515)=0.0772 kg of ash

6-Design of the Circulating Fluidized Bed Reactor

6.1-Methodology:-In order to design the circulating fluidized bed reactor, the design of the fluidized bed is of the main important. But for the design of fluidized bed, the physical properties of Catalyst such as nickel olivine and fuel (fine particles of wood) should be known. First of all internal diameter of the reactor is known in order to initiate the design of fluidized bed. 6.2-Design parameters:-The typical design parameters are Solid Volume Product Gas Volume Gasifier Volume Gasifier Diameter Wall thickness Residence time6.3-Calculation Procedure:-For the design considerations the whole reaction occurring in the Gasification process should be keep in mind6.4-Main Reaction[e]:-Three main reactions of the process are following:C+O2 CO2C+1/2 O2 COC+ H2O CO+ H26.5-Other Reactions in Gasifier[e]:-C+ CO2 2COH2O + CO H2+ CO2CO + 3H2 CH4+ H2 O N2 +3H2 2NH3

a) C+CO2 2CO + 164.9 kJ/Kmolb) C+H2O CO+H2 + 122.6 kJ/KmolEquations (a) and (b), which are the main reactions of reduction, shows that reduction requires heat. Therefore the gas temperature will decrease during reduction.

6.6-Considerations:-Low heating value (LHV) of wood = 17991.8 KJ/KgFlow rate of wood feed = 5.5158 Kg/sTemperature of Gasifier = T = 8500 C = 1123 KPressure of Gasifier = P = 1 bar = 101.325 pa = 1 atmConsider the behavior of Circulating Fluidized Bed Reactor as Plug Flow Reactor

There are three main reactions

C+O2 CO2C+1/2 O2 COC+ H2O CO+ H2Among these reaction (3) is slowest step according to thermodynamic study of these reactions.Hence considering the reaction 3, kinetics study shows that it is a 2nd order reaction soNow6.7-Performance Equation of Plug flow reactor [f]:-This equation is basically the relation between time, concentration, conversion and flow rate

Where = Initial Concentration of Carbon = Final Concentration of Carbon = Fractional Conversion of CaronSuppose Conversion of Carbon is 90%So = 0.90Mass flow rate of Carbon = 2.791 Kg/sAs1Kg of wood contains = 0.506Kg of Carbon2.791kg/sec x 1kmol/12kg = 0.2326 K mole/s of carbon=836.36 Kmol/hrTo convert it into volumetric flow rate, we divided it with density of carbon (graphite), that is Density of Carbon = 2000 Kg/m3As,Volumetric flow rate = Mass flow rate/ DensitySo,Volumetric flow rate of carbon = 2.791Kg/s / 2000Kg/m3 x3600s/1h= 5.0238 m3/hVolumetric flow of wood = 5.5158 Kg/sSo,Initial concentration of C = 836.36/5.0237= 166.67 Kmol/m3Final concentration =?

Where = fractional change in volume

We getFinal Concentration = 16.667 Kmol/m3Now rate equation for reaction

C+ H2O CO+ H2

Where[Cc] = final concentration of carbon[H2O] = concentration of H2OKc = rate constantSo,

We know the value of [C], but we do not know [H2O]The value of k comes out to be 0.11from literature[g]. Considering the rate equation in terms of concentration.As we knowPV = nRTN/V = P/RTconc. = P/RTSo of H2O,[H2O] = P/RTAs steam is entering atP = 101.325 kpaT = 300 C = 573 KSo by putting the values in above equation [H2O] = 101.325/8.314x573 = 0.021 Kmol/m3

So-rc=0.11x0.021x16.667-rc = 0.0385 kmol/m3 secNow6.8-Residence time = t[h]:-

t = 389 s = 6.49 min6.9-Volume of solid[h]:-To find the volume of solidFor plug flow reactor, we know that

= Flow rate of Carbon in feedV = Volume = initial Concentration of carbonV = 5.45 m36.10-Volume of Product Gas:-Flow rate of product gas outPV = nRTVg = nRT/Pn = flow rate of product gas out of gasifierFrom this, mass balance datan = 0.018 Kmol/sP = 101.325 KpaR = 8.314 Kpa m3/kmol.kT = 573.0 KPutting the values,Vg = nRT/P= (0.018 x 8.314 x 573)/101.325Vg= 17.33 m36.11-Volume of the Gasifier:-Total Volume = volume occupied by solid + volume occupied by product Gas= 5.45 + 17.33Total volume = 22.78 m36.12-Diameter of Gasifier:-Total Volume of Gasifier = 22.78 m3Area x length = 22.78 m3D2 /4 x L = 22.78 m3 Normally L/D ratio lies b/w 3 6 so,Assume L/D = 6.0[j]HenceL = 6D put in above equationD2 /4 x 6D = 22.786 /4 x D3 = 22.784.71 D3 = 22.78Diameter of gasifier = 1.68mLength of gasifier = 1.68 x 6Length of gasifier =10.08 m

A vessel must be designed to withstand the maximum pressure to which it is likely to be subjected in operation.

6.13-Minimum wall thickness:- t = PR/SE-0.6P + Tc[i]Wheret= reactor wall thickness in inchesP= design pressure difference between inside and outside of reactor, psigR= inside radius of steel vessel in inches= 1.68/2=0.84m=39.37x0.84=33.07inS= maximum allowable stress for the steel[k]. E= joint efficiency (0.9)Tc=corrosion allowance = 0.125 in.By using stainless steel pipeS=1200 PsiBy putting the values in above equation t = 14.7x33.07/(1200x0.9)-(0.6x14.7)+0.125 t = 486.13/ (1080-8.82) +0.125 t = 0.576 inches=25.4x0.576=14.63 mm

7-Fluidization[n]The phenomena in which bed of solid particle is fluidized, when the gas or liquid is pass through it with the velocity that will be able to make solid particles, to behave like fluid.The concept is depends upon the pressure drop and drag force. When the liquid or gas is pass through the bed of solid particles the pressure drop occur and the fluid exert drag force on the solid particles, the particles do not move but, if the velocity of the fluid steadily increased, the pressure drop and drag force on the particle increases till the point reach at which the particle starts to move and they become suspended in the fluid. This process is called fluidization. It has advantage for solid handling.The fluid velocity depends upon the density of suspended particles, its porosity and sphericity.

7.1-Conditions for fluidization:-The height and the pressure drop of the fluidized depends upon the velocity of the fluid entering the bed. If we draw the graph between pressure drop and bed height following graph occur. In the fluidized bed reactor upper portion is kept open or connected with cyclone separator. At the lower side of the bed the distributor plate is place to support the bed and to distribute the fluid to the entire bed. If the particle in the bed are small, the flow pattern of the fluid is laminar while passing through the channels of the bed and the pressure drop across the bed is directly proportional to the superficial velocity V0.When the fluid having the low velocity passes through the distributor plate, the solid particles will not move and bed height is remains same as shown in graph. But if we go on increase the velocity of the fluid, the particles will slight able to move and pressure drop increases, this is the point A in the figure. After that the particles shows minimum fluidization and height of the bed going to be change. When particles are fluidized the pressure drop across the bed remains constant. At the fluidization of the particles the bed height changes and that is the point BC on the graph. When the pressure drop remains constant at fluidization, if we go on decreasing the velocity of the fluid the bed height decreases that is the point BC on the graph.The point at which the particles begins to move is the minimum fluidization velocity V0M. The maximum velocity of fluid at which particles begins to entrain out of the reactor is called Terminal Fluidization Velocity VT. The fluidization velocity is selected between minimum and terminal Fluidization velocity.

8-Design of the Fluidized bed8.1-Parameter:- Bed Height Bed Area8.2-Assumptions:-Density of Steam [o] (850 0C, 1 atm) = s = 0.41 kg/m3Viscosity of Steam (850 C, 1 atm) = = 0.0000404 pa.sProperty[n][p][r]Nickel Olivine CatalystSawdust

Mean Particle Size (m)3501000

Apparent Density (kg/m3)1755215

Porosity ()0.480.7

Sphericity ()0.80.5

True Density (kg/m3)3250717

Apparent Density [r]

In order to find the area of the fluidized bed, following parameters should be known Minimum Fluidization Velocity Vmf Terminal Fluidization Velocity VT Fluidization velocityConsider the flow of fluid between the channels of particle is laminar for minimum Re.8.3-Minimum Fluidization velocity [q]:-

Ni/O CatalystSawdust

Minimum Fluidization Velocity (m/s)0.050.1

8.4-Terminal Fluidization Velocity [q]:-

Ni/OSawdust

Terminal Fluidization Velocity (m/s)3.12.91

To select the Fluidization Velocity the correlation is given in the (Chatterjee et al 1995) in the form of height. But if we select fluidization velocity 3 m/s by considering the minimum and maximum fluidization velocity of the particle we might able to find the ratio of Expanded Bed Height H and minimum Bed Height Hmf.

So the bed height for both the particles isNi/O CatalystSawdust

Bed height ratio3.211.6

Hence with the allowance bed height ratio is selected

8.5-Area of the Fluidized Bed [r]:-To find the Cross Sectional area of the Fluidized Bed.

9-Conclusion:- Study of circulating fluidized bed (20MW-100MW) in the presence of Nickel-Olivine catalyst reveals that for 100 MW of wood, wood to steam ratio is 0.6-0.7 which further leads to make an estimate of the flow rate of feed. So, flow rate of wood is 5.515kg/s fed from the top of the reactor and steam required for the gasification of 5.515kg/s is 3.8605kg/s which after conversion of 90% of wood produces 4.9635kg/s of syngas with production of Ash 0.077kg/s. Here, the density of wood can be considered as a bulk or apparent to find out the volumetric flow rate for the reactor. The various parameters of circulating fluidized bed like volume of solids which is 5.45m3,volume of product gas Vg is 17.33m3 ,total volume of gasifier 22.78m3,diameter of gasifier is 1.68m, length of the reactor is 10.08m, wall thickness of reactor is 14.63mmand residence time for the reaction is 6.49 min designed from above discussed basis.in the design of fluidized bed we calculate the bed height and bed area also the minimum fluidized velocity for catalyst is 0.05 and for wood 0.1 and terminal velocity of catalyst is 3.1 and for wood it is 2.91. By the study of mean particle size of wood and catalyst, porosity of wood and catalyst and sphericity of both. The bed height is 3.21 for catalyst and for wood it is 1.6.

10-References:-1) http://www.sciencedirect.com/science/article/pii/S096195340900230X2) http://www.sciencedirect.com/science/article/pii/S09619534020010223) http://theurbanfarmingguys.com/wiki/Wood_Gasification4) http://www.fao.org/docrep/t0512e/t0512e0a.htm5) http://books.google.com.pk/books?id=2-G0SaWM80oC&pg=PA36&lpg=PA36&dq=difference+between+the+entrained+gasifier+and+draught+gasifier&source=bl&ots=8iYL6un9AN&sig=9EgwsIM-UsbrHeE-pz3R9XKAnP8&hl=en&sa=X&ei=KqXSUuyYKYyr0AWti4D4BA&ved=0CDkQ6AEwAw#v=onepage&q=difference%20between%20the%20entrained%20gasifier%20and%20draught%20gasifier&f=false6) http://en.wikipedia.org/wiki/Gasification#Co-current_fixed_bed_.28.22down_draft.22.29_gasifier7) http://en.wikipedia.org/wiki/Gasification8) http://www.nariphaltan.org/Gasifier.pdf9) http://www.gasification-freiberg.org/PortalData/1/Resources/documents/paper/IFC_2010/06-2-Pugsley-Mahinpey.pdf10) http://www.amracenter.com/doc/pubblicazioni/11i.flugas.pdf11) http://www.google.com.pk/patents?hl=en&lr=&vid=USPAT4183208&id=VTk0AAAAEBAJ&oi=fnd&dq=fluidized+bed+gasifier&printsec=abstract#v=onepage&q=fluidized%20bed%20gasifier&f=false12) http://books.google.com.pk/books?id=bFT204XDTQ0C&pg=PA1&lpg=PA1&dq=difference+between+bubbling+and+circulating+fluidized+bed+of+gasifier&source=bl&ots=CvCyyxLnia&sig=MX0TxOs0k48RC_KijZwA2YCyQs4&hl=en&sa=X&ei=FsLSUsbXDpCrhAfTn4CQBQ&ved=0CDIQ6AEwAg#v=onepage&q=difference%20between%20bubbling%20and%20circulating%20fluidized%20bed%20of%20gasifier&f=false13) https://www.google.com/search?site=imghp&tbm=isch&source=hp&biw=1280&bih=708&q=fixed+bed+gasifier&oq=fixed+bed&gs_l=img.3.3.0l10.1640.4688.0.8340.9.9.0.0.0.0.381.1476.3j2j3j1.9.0....0...1ac.1.32.img..2.7.892.wmUmKk5Tecw#q=fixed+bed+gasifier+for+wood&tbm=isch&facrc=_&imgdii=_&imgrc=7kG45g37_fynoM%253A%3BjfL02vsAxotFoM%3Bhttp%253A%252F%252F4.bp.blogspot.com%252F-tR3S_E9yUF0%252FURjzIG7xWpI%252FAAAAAAAAAEk%252F1QlgkBdPT-g%252Fs1600%252Fgasifier.jpg%3Bhttp%253A%252F%252Fmechentropy.blogspot.com%252F%3B578%3B30114) http://www.fao.org/docrep/t4470e/t4470e0m.htm15) http://www.eco-innovation.eu/index.php?option=com_content&view=article&id=624:bosio-doo&catid=73:slovenia16) http://www.ncbi.nlm.nih.gov/pubmed/1159073917) http://www.ficfb.at/18) http://www.netl.doe.gov/technologies/coalpower/turbines/refshelf/handbook/1.2.1.pdf19) Biomass Gasification and Pyrolysis, Practical Design and Theory by Prabir Bassu.

a) Prabir Bassu, Biomass Gasification and Pyrolysis Practical Design and Theory, chapter 2, page 58b) Prabir Bassu, Biomass Gasification and Pyrolysis Practical Design and Theory, chapter 2, page 51 table 2.8c) The study of reactions influencing the biomass steam gasification process http://www.sciencedirect.com/science/article/pii/S0016236102003137d) http://www.gabrieljebb.com/media/whitepaper/week5/research/Chemistry%20of%20Wood%20Gasification.pdf]e) Theory of gasification http://www.fao.org/docrep/t0512e/t0512e09.htm (all reactions)f) Chemical Reaction Engineering by Levin spiel page 92 (PFR equation)g) Combustion and gasification in fluidized bed by prabir Bassu page 68 (Value of k)h) Chemical Reaction Engineering by Levin spiel Chapter 5 section 5.2 ( volume of solid & residence time)i) S,S&L Chapter 7 Terry A. Ring ChE (wall thickness equation)j) http://www.google.nl/patents/US4828581(h/d ratio)k) http://www.engineeringtoolbox.com/temperature-allowable-stresses-pipes d_1338.html(allowable stress ) l) http://www.researchgate.net/publication/256569410_Prospects_for_coal_gasification_in_Pakistanm) Biomass gasification By Anil K. Rajvanshin) McCabe, Smith, Harriott Unit Operation of Chemical Engineering,edition 7th , pg # 177o) M. Smith, Van Ness, Abott Introduction to Chemical Engineering Thermodynamics Edition 7th p) Perry Chemical Engineeringq) J.Ramirez, J. Martinez, L Petro, Basic Design of Fluidized Bed Gasifier For Rice Husk on Pilot Scaler) Prabir Basu Biomass Gasification and Pyrolysis, Practical Designs) D. Kunii, O. Levenspiel Fluidization Engineering,1991t) Gomez Barea, Campoy M, Ollero P. Fernandez C Pilot Plant Experiences with Fluidized bed Gasification of Orujillo and MBMu) http://books.google.com.pk/books?id=GzKmQnrdXm0C&pg=PA512&lpg=PA512&dq=olivine+porosity&source=bl&ots=ygTd9SYuK1&sig=jR7PFlBqvsxoIcNQDcm8ulRnXGQ&hl=en&sa=X&ei=aXfTUvzyGueZ0QXe5IHwBA&ved=0CEwQ6AEwBw#v=onepage&q=olivine%20porosity&f=falseGroup # 1Chemical 7th Date 15/01/2013