WOOD CHARCOAL

Wood charcoal which is called simply charcoal is made by carbonization (destructive distillation, i.e. heating in absence of air) of wood at 600C.
Physico-chemical changes during wood carbonization
Following four stages are involved in the carbonization of wood:
- When the temperature reaches 100-120C, initial decomposition of wood takes place resulting in the formation of little distillate gas containing acetic acid and water.
- Active distillation of wood takes place upto 350C till the process is exothermic producing liquid products (like acetic acid, methyl alcohol, pyroligneous acid, tar etc.) and gaseous products containing Carbon monoxide, carbon dioxide, nitrogen, hydrogen, hydrocarbons etc.
- From 350 to 600C, slow evolution of residual volatile matters (i.e. gases) from the wood/charcoal left in 3rd stage.
Products in wood carbonization
Charcoal is the solid product left after the carbonization of wood. Hot gases are cooled to separate wood gas and liquid into two layers. Upper layer of the liquid is prodigious acid and the lower level is wood tar. Pyroligneous acid is an aqueous solution of acetone, methyl alcohol, and acetone and wood spirit mainly. Wood tar can be fractionated to separate many chemicals. Besides it is used as a supplementary plant fuel. Normally matured dense wood gives dense charcoal on carbonization.
Typical product yields in wood carbonization
Product Yield % air dried
Charcoal 30
Pyrolignious acid 38
- Acetic acid 8
- Wood spirit 15
- Water 15
Wood tar 10
Wood gas 22
Scheme of wood carbonization
Carbonization of wood is done in open pit (primitive method, now obsolete), kilns or metal retorts. Pits and kiln are located in forests and retorts in factories.
In open pit carbonization wood is burned in large heaps with restricted air. Yield of charcoal is 20%, which is of inferior quality. Besides, gas and liquid by-products are lost to the atmosphere, as they cannot be recovered. Even the charcoal that we get from domestic wood burning ovens also comes in this category.
In charcoal kiln also, charcoal (of better yield and quality) is the only product as gases and liquid by-products are not recovered. Kiln is parabolic in shape having typical dimension, radius=3 meters, height=2.5 meters and capacity=30m3 of stocked wood.
Wood is stacked on the ground with one verticals central passage acting s the chimney and a horizontal passage at the bottom for introducing fire to the center. The kiln is covered with thick layers of grass, leaves etc. and then plastered with a mixture of earth soil and charcoal dust. Initial firing is done with grass and twigs and then the wood is partly burned to supply heat for the process. Carbonization time is 7-10 days. After that fire is extinguished with water and the kiln is allowed to cool for a week are least before the charcoal is taken out.
Carbonization in metal retorts is done at a low temperature of 350C. Retorts may be of four types namely:
-Externally fired (heated) batch retorts
-Externally fire continuous vertical retorts
-Internally heated batch vertical r retorts
-Internally heated continuous vertical retorts.
Most recent design is internally heated retorts which use-forced recalculation of heated inert gases evolved during carbonization. Besides, it employs efficient mechanical handling of wood and charcoal and has high thermal efficiency.
Characteristics of products of low temperature carbonization of wood are:
- Charcoal yield is high (35%)
- Ash content of charcoal is low (below 2.5%)
- Volatile matter in charcoal is high (up to 15%); hence it can be easily ignited and burns at low rates.
- Heating value of charcoal is high (7500Kcal/kg)
- Charcoals produced have high vapor adsorption capacity.
High temperature carbonization of wood.
It is mainly carried out for the production of town gas and chemicals besides for charcoal. Carbonization temperature is 1000-1200C. Besides, town gas (which can be used for heating of domestic ovens) the valuable liquid chemicals like creosote (used as a wood preservative), turpentine, light & heavy oils are produced. Product characteristics are:
- Charcoal yield= 25%
- Heating value of charcoal = 8000 kcal/kg
- Gas yield=850 Nm3 gas/ton dry wood
- Gross heating value of gas = 3000kcal/Nm3
- Composition of gas: CO2 =13% CmHn (unsaturated hydrocarbons) =2%
CO=24%, CH4=15%, N2 =1%, H2=45%.
Uses of charcoal
- Because of its large specific surface area (150-450 m2 /gm) and light and porous nature, it is used for removal of obnoxious and coloring materials from solutions, gases, vapors, petroleum products etc. By adsorption on its surface.
- It can be used as a feedstock for gasification to make producer gas, which is used for domestic and industrial heating. During Second World War, this producer gas was used as a fuel in road vehicles in many countries.
- It is used as a clean and smooth burning fuel in domestic heating ovens but it is a costly fuel.
- Previously it was being used for metallurgical furnaces but now it has been replaced by coke. In blast furnace using charcoal instead of coke, the charcoal consumption can be upto 1-ton charcoal/ton pig iron for capacity of the blast furnaces of,000 tons pig iron per year.
- It is used very widely as fuel for blacksmith’s and metalworker forge furnaces/ovens.
- It is raw material for the manufacture of carbon disulphide.
- It is mainly used as a domestic fuel in developing countries.
Composition of charcoal.
A typical composition of charcoal is given below:
C=80% O2&N2=15%,H2=2% and Ash =3%
Merits of charcoal as a fuel
- It has a very high specific surface area compared to coal (20-200m2/gm coal)
- Its ash content is very low (below 3%)
- Its calorific value is high (6500-8000 kcal/kg).
Demerits of charcoal as a fuel
Its mechanical strength is very poor, hence it gets crushed to powder in operation, which is easily swept away in a current of gases, and also it may prevent the proper flow of gases in the furnace.

Calorific value

Calorific value

The quantity of heat (Kcal) liberated by the combustion of unit quantity of fuel is called its calorific value. Unit of calorific value is Kcal/kg for solid and liquid fuels and Kcal/Nm3 for gaseous fuels. Nm3 means volume of gas in M3 at Normal Temperature and Pressure (NTP) which is zero deg0 C and 760 mmHg. Since the volume of gases varies sensitively with pressure (Boyle’s Law) and temperature (Charle’s Law) hence their volume is expressed at NTP in Nm3 to have a standard measurement.
Gross calorific value or higher heating value at constant volume is the quantity of heat liberated by combusting the fuel at constant volume in oxygen saturated with water vapour, the original material and final products of combustion being at a reference temperature (25degC) and the water obtained from the fuel being in the liquid state.
Gross calorific value at constant pressure implies that the combustion takes place at constant pressure and not at constant volume. In the laboratory determinations, solid and liquid fuels are burnt at constant volume and gaseous fuels are burnt at constant pressure. In the ovens and furnaces, however, the combustion takes place at constant pressure. The difference in the two corresponding values is small. For coal, the calorific value at constant pressure exceeds the calorific value at constant volume by about 5.5 Kcal/kg
Net calorific value or lower heating value at constant volume is the quantity of heat evolved when unit quantity of fuel is burnt at constant volume in oxygen saturated with water vapour, the originals material and final products of combustion being at a reference temperature (25degC) and the water obtained from the fuel being in the vapour state. The net calorific value is therefore less than the gross calorific value by the amount of the heat of condensation of water vapours, which at 25deg C is 583.5 kcal/kg of water. On the basis of hydrogen of water, this is equal to 5,252 kcal/kg 468.9 kcal/Nm3 of hydrogen. The following formula is used in calculating the net calorific value from gross calorific value of solid and liquid fuels approximately.
CN=CG-53 H
where CN and CG = net and gross calorific value in kcal/kg, respectively, and H= percentage of hydrogen of coal, including hydrogen of moisture and of water of hydration of minerals.
For a gaseous fuel, the formula is:
CN=CG-4.7V
where CN and CG = net and gross calorific values in kcal/Nm3, respectively, V= volume percentage (as H2) of total hydrogen of the gaseous fuel, including the hydrogen obtainable from other combustible components.
Net calorific value at constant pressure implies that the combustion takes place at constant pressure and not at constant volume.

Energy costing methods

There are two definite considerations to the study of energy costing:
a) cost of providing the energy service;
b) expenditure on energy by the user.
Both aspects must be considered since wastage can occur in either area. Furthermore, it must be decided if the user department is to be designated a portion of the fixed costs or if they are to be absorbed into the same manner, the method of allocation dose not matter. Controlling these costs should be undertaken using management accountancy techniques, and two methods useful for the control of future energy costs are budgeting and standard costing.
Budgeting
Budgeting is simply estimating future energy demand, in terms of steam, electricity, oil, gas, by the various departments. This may be done in terms of energy units, such as terms, kWh, Btu, or in monetary units. Controlling the system is exercised by comparing the budgeted unit costs with actual costs and accounting for any variation. The process of accounting for variation is called variance analysis and variations from the budget can be caused by:
a) different production volume (volume variance);
b) different energy consumption per unit (energy efficiency variance);
c) different cost of energy to firm (price variance).
The total variance is obtained from the sum of the three component variances. A sophisticated budget would project energy costs for various levels of output and is termed a flexible budget.
Standard costing
Standard costs are the expected costs of the various energy-related inputs into the plant (oil, gas, electricity, wages etc.). These standards costs divided by budgeted consumption by the user/departments gives the standard unit cost.

Fuel cell electrode fabrication

Fuel cell
There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons and electricity is produced through a chemical reaction with oxygen or another oxidizing agent.
Fuel cell consists of an anode (negative side), a cathode (positive side) and an electrolyte that allows charges to move between the two sides of the fuel cell. Electrons are drawn from the anode to the cathode through an external circuit, producing direct current electricity. The reactions that produce electricity take place at the electrodes. The first generation of polymer electrolyte membrane fuel cells (PEMFC) used PTFE-bound Pt black electro catalysts that exhibited excellent long-term performance.
There are two methods of preparing PTFE bonded fuel cell electrodes, namely dry and wet methods depending upon the form of PTFE used.
Wet Method
In this method, aqueous PTFE emulsion is used. The procedure used is as follows: The depyrophorised Raney-Ni powder is first mixed with promoters (e.g. Cu2O). This mixture is added to PTFE suspensions. Isopropanol is added to stabilize the rubber like resultant mixture. During this mixing the suspension of PTFE breaks and water is removed. This paste is heated in order to evaporate some water and isopropanol resulting into a plastisizable mass. Cold rolling of this mass is done to obtain a felt of 0.2 to 0.5 mm thickness. Finally this felt is rolled with a nickel net which also works as a current collector. The cold rolling results into more linkage of catalyst particles with PTFE strands.
D-1 PTFE suspension containing 60% of PTFE, mixed with the catalyst, is milled for one hour at 20±20C. The paste is calendar rolled into 0.1 to 0.2 mm thick sheet. The surfactants are removed by boiling the sheet in acetone. Thus obtained layer is used as catalyst layer. Gas side layers are prepared by using nickel black powder blended with PTFE dispersion. These two layers are rolled with a mesh of stainless steel to get the final electrodes. In later, use of dopants like chromium and titanium improves and stabilizes the polarization characteristics of Raney nickel electrodes.
Dry Method
Use of dry PTFE powder in making fuel cell electrodes is relatively new. Dry PTFE powder with Raney nickel catalyst is used to prepare fuel cell hydrogen electrodes. In this method 5-8 wt% of PTFE is added to catalyst. The blend is milled into a high speed machine with sharp blades. It formed a network of PTFE treads and lumps with catalyst grains in between. The high speed blade milling of the catalyst particles with PFE leads to PTFE coating on the catalyst grains. As a result of this process which is known as reactive mixing, a fluffy mass of the powder is produced. The next step is the rolling of this fluffy PTFE-catalyst mixture into a calendar to form a tape. This tape is further rolled on to a wire mesh of nickel.

Gas analysis

Gas analysis down to low concentrations

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Gas Analysers

Witt gas analysers are fast, precise and multifunctional. The gas analysers are used as stationary or portable units for sample or continuous gas analysis for almost any gas and application, for example in food (MAP) or steel industry.
Fuel gas analysers
WITT gas analysers for hydrogen are used for permanent or sample analysis of gas mixtures and provide high quality and safety in production processes, for example in thermal treatment applications. It is an analyser, available for integration with gas mixers or as a stand alone unit, for continuous analysis (in-line) of the gas concentration for a variety of industrial applications. Measuring range O2: 0 to 100%, CO2: 0 to 30 or 100%, CH4: 0 to 10 or 100%, H2: 0 to 10, 30 or 100%, and He: 0 to 30 or 100%.
See: http://www.wittgas.com/EN/gas_analysers.html

FTIR gas analyzers
Horiba has introduced FTIR gas analyzers enables the detection and measurement of a wide variety of substances, such as PFCs, greenhouse gases and semiconductor / flat panel display (FPD) process gases. Legislation / guidelines encourages industry to act to reduce these substances due to their contribution to global warming. The use of a cell with a long optical path length enables measurement of low-concentrations down to the sub-ppm level. See http://www.horiba.com/scientific/

Throat less gasifier design

Gasification
Thermo chemical gasification is the conversion of carbonaceous feedstock such as biomass or coal by partial oxidation at elevated temperature a into a gaseous energy carrier. Gasification occurs in sequential steps: drying to evaporate moisture, pyrolysis to give gas, vaporized tars or oils and a solid char residue, followed by gasification or partial oxidation of the solid char, pyrolysis tars and pyrolysis gases.
The gas obtained on gasification contains carbon monoxide, carbon dioxide, hydrogen, methane, trace amounts of higher hydrocarbons such as ethane and ethene, water, nitrogen (if air is used as the oxidizing agent) and various contaminants such as small char particles, ash, tars and oils. The partial oxidation can be carried out using air, oxygen, steam or a mixture of these.
Air gasification produces a poor-quality, low energy density gas (4-7 MJ/ cu.m, higher heating value) which is suitable for boiler, engine and turbine operation, but not for pipeline transportation. Oxygen gasification produces a better-quality gas (10-18 MJ/ cu.m, higher heating value) which is suitable for limited pipeline distribution and for use as sythesis gas for conversion to methanol and gasoline.
Open-core downdraft gasifier
This type of gasifier was first devised by the Chinese for rice husk gasification and further developed by Syngas Inc. from work carried out at the Solar Energy Research Institute (now the National Renewable Energy Laboratory - NREL).
This type of gasifier is called as static bed or open core or throat less gasifier and is a simple reactor technology developed principally for small-scale or remote applications requiring fuel gas for heat or power. This type of gasifier has been developed with no throat and the bed is supported on a grate.
The reactor generally consists of two concentric cylinders (one may be sufficient), in which a stationary fuel bed is converted by a reaction front propagated through the fuel bed. When under suction created at the intake of an engine, the reactor top can be left open for refueling without venting producer gas.
Specifc gasifcation rate
Specifc gasfication rate (SGR) is an important parameter which expresses the rate of fuel consumption per unit cross-sectional reactor area. An optimum value of this parameter is used for designing different capacity range of throatless gasifiers.
Calculation of air to be supplied
The equivalence ratio (ER) is defned as the ratio of actual air used in a run to stoichiometric air requirement for the run where ER= (Amount of air used in a run)/(Amount of stoichiometric air). Knowing the elemental composition of raw material, the stoichiometric air requirement can be estimated (for dry rice husk the value is 3.35 cu.m / kg). Optimum value of equivalence ratio for gasification can be taken as 0.40. The air fuel ratio can be estimated using the expression, A/F=Amount of air used (kg)/Amount of dry material (kg). This calculation helps to find the amount of air to be supplied for gasification (through engine suction or an external blower).
Determination of gas flow rate
The gas flow rate can be determined by installing a calibrated orifice meter in the producer gas line. But due to the presence of tar in the gas the orifice meter tend to get foulded and soon will result faulty gas flow readings. It is therefore preferred to measure the air flow to the gasifier and make a nitrogen balance to estimate the gas flow rate. For this, install a pre-calibrated orifice meter in the upstream section of the gasifier (just before the gasifier) to measure the air flow rate. Knowing the producer gas composition, elemental analysis of biomass, feed rate and air flow rate, nitrogen balance over the gasifier may be carried out using the following procedure for gas flow rate determination. For this computation assumptions are made that air has a molar composition of 0.79 Nitrogen and 0.21 Oxygen and all the nitrogen entering the gasifier leaves it in producer gas.
Nitrogen input = Flow rate of air (Nm3 / h)* 0.79 + Fuel feed rate into the gasifier (kg/h)* Weight fraction of nitrogen in the biomass * (22.416 / 28)
Nitrogen output = Flow rate of producer gas (Nm3 / h)*mole / volume fraction of nitrogen in the producer gas
By equating the above two statements we can solve for flow rate of producer gas
Reactor sizing
Previous works report a specific gasification rate of approximating 170 kg/sq.m.h, which is an intermediate value between two levels and a maximum thermal efficiency exists at this value. Using an optimal value the size of the reactor can be readily computed from the energy demand on the system.
Theoretical modeling and experimental works have been done for moving bed open-core rice hull gasifier using a 45 cm diameter reactor. Results of their work showed an optimum gasification load or specific gasification rate of 125-175 kg/sq.m h, depending on bed height. According to another report the cold gas efficiency of 26 cm. reactor diameter gasifier reached a peak of between 50 and 60% at specific gasification rate of 200 kg/sq. m h.
Another report indicates an optimum value of specifc gasifcation rate for gasifcation of rice husk in throatless open core gasfier reactor as 192.5 kg/sq.m h. Optimum value of equivalence ratio was 0.40, the gas lower heating value of producer gas was about 4 MJ/N cu.m.and the cold gas efficiency was around 65%.
For determining the reactor diameter for a downdraft stratified gasifier , Reed has indicated an optimum value of specific heat rate as 390 kg/sq.m h for 8 to 75 cm diameter reactors. It is further reported that the maximum specific heat rate can go up to 580 kg/sq.m h with gasifier having mechanical ash removal unit. However it is reported that these figures were derived through experiments with a particular gasifier type and mode of operation. From the fore going it is clear that a preliminary value of 200 kg/sq.m h can be taken as a value for SGR for determining the reactor diameter.
Reactor construction
The reactor can be a batch fed type having constant diameter. It can be made from a minimum of 3 mm thick steel sheet. The gasifier consists of an inner reactor and a concentric containment tube. The containment tube and the reactor can be flanged together at the top. The top end of the reactor can remain open during the operation. Air entry into the reactor will be from the top and gas exit through preferably a stainless steel wire mesh grate, fitted at the bottom of the reactor. The bottom of the containment tube should be water sealed. The diameter of the containment tube can be selected in such a way that the producer gas velocity in the space between the reactor and the containment tube is around 0.6 m/s.
Starting a small gasifier
A small amount of char is placed over the grate followed by feedstock. The purpose of adding char over the grate was to protect the grate from high temperature damage. A suction blower can be connected in the down stream section of gasifier after the first filter to start the initial establishment of ignited charcoal. Then the feedstock is filled and the blower operated for some time to start the gasification. A flare burner may help find that combustible gas is generated from the gasifier.
Chinese gasifier design for rice husk
The gasifier consists of an inner tubular steel shell reactor of 25 cm diameter, open at the top and closed at the lower end by a stainless steel mesh screen. It was housed within a concentric 35 cm gas collector. The lengths of reactor and collector are 168 and 183 cm respectively for one hour continuous operation. Air enters the reactor at the open top and passes downward through the fuel column to the reaction zone when under suction from engine intake system. The gas from the reaction zone flows in the reverse direction to the hot outlet.
Raw gas is passed through a wet sieve plate (scrubber and particulates). The twin reactor design enables the engine to draw from one reactor while the other is being serviced.
The gasifier generates a nearly uniform reaction front propagating upwards at a velocity of 0.77-0.87m/h. With a temperature of the reaction front maintained at 950-1050°C.
Gas composition is as follows (Vol%): CO13.4%, H2 11.1%, CH422%, 0221.4%, N258.9%, H2O4.13%, lower heating value (LHV) 40223.8KJ/Nm3, Gas flow is 18.44 Nm³/h. Specific gas output is 2.39Nm³/kg rice husk. Specific gasification rate is 185 kg/m-h. Cold and raw gas efficiency was 52.4% and 72.2%.
Static bed 25 cm rice husk gasifier yielded an optimal value of specific gasification rate in the vicinity of 195 kg/m² -h. Cold gas efficiency (52.4%) and gas flow (18.44NM3/h) are favorable for selected duel-fuel engines.
Indian gasifier design for sugarcane leaf and bagasse
This is a low-density biomass gasification system for thermal applications. The gasifier can handle fuels like sugarcane leaves and bagasse, bajra stalks, sweet sorghum stalks and bagasse etc. The system delivered under laboratory conditions at 288-1080 MJ/h output levels. The HHV of the gas was 3.56-4.82 MJ/N cu.m. The system also produced char of about 24% by weight of the original fuel. It can be briquetted to form an excellent fuel for wood stoves or can be used as a soil conditioner. The system was retrofitted to a specialty ceramics baking LDO-fired furnace in a metallurgical company.

Intermediate Temperature SOFC coupled gasifier

Fuel cell
Fuel cell is an energy conversion device (chemical energy is converted to electrical energy) that utilises a gaseous fuel and oxidising gas to produce electricity and heat, having less or no other emissions, when compared with other power generation technologies. It consists of three components (anode, cathode and electrolyte) and depending on type, can operate at a wide range of temperatures with relatively high electric efficiencies. Fuel cells are currently manufactured by a number of fabrication techniques, such as dry pressing, tape casting, screen printing, slurry coating, depending on the type of fuel cell.
Fuel cells are used also in many applications, either stationary (power generation) or traction. Currently, there are six major types of fuel cells that are developed. Among these, the Alkaline and Polymer Electrolyte fuel cells are operated at low temperature, the Phosphoric Acid at intermediate, while Molten Carbonate and Solid Oxide fuel cells are mainly high temperature fuel cells. Demonstration activities all over the world are trying to bring the manufacturing and commercialisation closer to reality.
Solid Oxide Fuel Cells
Interest in Solid Oxide Fuel Cells (SOFCs) capability to operate at intermediate temperature range had led scientists and engineers to focus the research and Development (R&D) efforts on the design and fabrication techniques. The capability to fabricate such fuel cells having thin electrode structures has been demonstrated by a number of groups worldwide. Additionally to this “Thin Film Technology”, material characteristics, especially solid-state ionic and proton conduction at low temperatures, has created a new research field that has attracted attention and interest in recent years.
Of the various types of FCs, the SOFC is the most demanding from a materials point of view. However, because it operates at relatively high temperature, it offers the significant advantage of simple fuel pre-treatment. This advantage creates opportunities for SOFCs where natural gas, biomass, diesel, military fuels, and gasoline are the abundant fuels. Applications where SOFCs may find dominant positions include distributed power, and, military transport applications, heat generation for the home and auxiliary power units. For various applications, the technology must reach a reliable level sufficient to allow the plants to operate unattended.
Operating constraints
SOFC’s must operate at high temperatures to enable diffusion of oxygen ions through the electrolyte made possible by reason of oxygen vacancies in the electrolyte crystalline structure. With conventional designs the anode is a composite of nickel and yttria-stabilised zirconia (YSZ). This composite is an electronic conductor (due to nickel) and also an ionic conductor (due to YSZ). Nickel, however, catalyses the formation of graphite from hydrocarbons, except for a narrow range of operating temperatures and only for methane, thus carbon formation with nickel based anodes is unavoidable for the wider range of hydrocarbon fuels available. Research reports suggest that anodes made from a composite of copper and ceria, or samaria-doped ceria, may remove this barrier in the future.
Cell geometry and construction
Currently, R&D is also focused on the fabrication of fuel cell units with different geometry, depending mainly on different specific requirements. Basically, three different designs are under development, which differ only in cell geometry.
• Tubular Design
• Planar Design
• Monolithic Design
Cell is the repetitive electrochemical building block that is connected either in series or in parallel, forming the “stack” or the “unit” of fabrication. The basic SOFC cell consists of the following common parts:
• The Anode
• The Electrolyte
• The Cathode
• The Interconnect (bipolar) plate
• The support tube (only in tubular design)
Intermediate Temperature SOFC
When the SOFC operates at intermediate temperature range (below 700 °C), some of the problems raised from high temperature operation can be overcome. Such problems include material high cost and efficiency losses. Additionally, several changes need to be made to cell and stack design, cell materials, reformer design and operation, and operating conditions in order to operate at intermediate temperatures. On the other hand, low temperature operation brings additional benefits, which include:
• Low cost metallic materials, such as ferritic stainless steels can be used as interconnect and construction materials. This makes both the stack and balance of plant cheaper and more robust
• More rapid start up and shut down procedures
• Corrosion rates are significantly reduced
Biomass Integrated Gasification Fuel Cell Systems
The combination of biomass gasification with a Fuel Cell Systems such as SOFCs is a highly promising approach to exploit the potential of biomass in combined heat and power generation.
In a first step the solid biomass is converted to a combustible gas mixture. The composition of the gas mixture depends on the employed reactor type, gasification agent, feedstock and operating conditions of the gasification process. It consists to a major extent of hydrogen and carbon monoxide, the rest being carbon dioxide, methane, other hydrocarbon species, water, diverse impurities (e.g. tars, alkali salts, sulfur, soot particles etc.) and nitrogen in case of air as gasification agent. The impurities are potentially performance degrading and have to be removed to some extent in order to meet the requirements of the employed fuel cell. The requirements depend on the specific fuel cell (FC) type and its design, catalyst materials and the operating conditions. The strong interactions between the composition of the gas mixture obtained from the gasification process and the fuel cell entail that optimal system integration is crucial for overall energy efficient and cost effective system.