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Biomass Gasifier

The Gasifier unit is essentially a chemical reactor, where several thermo-chemical processes such as pyrolysis, combustion, and reduction take place.

Most biomass materials like Wood , Charcoal , Rice Husk etc can be converted into a gaseous fuel known as producer gas, which comprises carbon monoxide, hydrogen, carbon dioxide, methane, and nitrogen. This gas has a lower calorific value (10001200 kcal/nm3) compared to natural gas or liquefied petroleum gas, but can be burnt directly with high efficiency and good degree of control without emitting smoke. The producer gas flame temperature can be as high as 1100 oC. Each kilogram of air-dry biomass (10% moisture content) yields about 2.5 nm3 of producer gas. In energy terms, the conversion efficiency of the biomass gasifier process is in the range of 80%90%.

What is Biomass Gasification?

The Old Method: Conventional Combustion

We know very well that the direct burning/ combustion of wood / biomass, is a complete oxidation process, which primarily produces heat (thermal energy). The by-products are solid waste, and carbon dioxide (CO2), NOx, CO, and particulate emissions most of which are potentially hazardous to the environment..

Combustion is an inefficient conversion process when generating power alone-some advanced designs are improving efficiency. It requires water if generating power with a steam turbine

Combustion is of limited value, it's dirty, and it makes the control and capture of CO2 very difficult, if not impossible.

Because of the relentless rise in oil and gas prices worldwide, We believe that gasification offers significant economic and environmental advantages as an unconventional source of energy in a carbon constrained world.

The New Technology: Gasification

Gasification is a flexible, reliable, and commercial technology that can turn a variety of low-value feedstocks into high-value products, help reduce a country's dependence on imported oil and natural gas, and can provide a clean alternative source of energy.

The gasification process renders the use of biomass relatively clean and acceptable in environmental terms. The gasifier does not generate emissions: engines exhaust gas is cleaned in a catalytic converter and then, in case that the concerning heat is used for biomass conditioning, sent to the dryer where it is further bio-filtered.

In this process organic or fossil fuel based carbonaceous materials converted into producer gas ,a low calorific power (1000-1200 kCal/m3 ) mix of Carbon monoxide 18%-20%, Hydrogen 15%-20% Methane 1%-5%, Carbon dioxide 9%-12%, Nitrogen 45%-55%.

This is achieved by reacting the material at high temperatures (>700 C), without combustion, with a controlled amount of air/ oxygen.

Gasification process

It includes four stages, each occurring in one of the four separate zones within the gasifier: drying, pyrolysis, oxidation and reduction zone.


In the drying zone, moisture in the feedstock is evaporated by the heat from the lower zones at a temperature of 150-200 degrees C. Vapours move down and mix with vapours originating in the oxidation zone. A part of the vapours is converted into oxygen under the following chemical reaction: ? + H2 O <=> CO +H2 with the remainder being retained in the producer gas.


Located below the Drying Zone, temperatures here reach 400 to 650 degrees C. Pyrolysis reactions occurt temperatures above 250 degrees C. During pyrolysis, large molecules such as cellulose, polycellulose and lignin, are broken down into medium-chain hydrocarbons and carbon (charcoal). Pyrolysis products then move down towards hotter areas within the gasifier, some of these burn while the others break down further into smaller molecules and atoms such as hydrogen, methane, carbon monoxide, ethane, ethylene, and others.


At this level, air is injected into the gasifier, leading to the following chemical reactions:

C + O2<=> CO2

H + 1/2O2<=> H2 O

These reactions release large amounts of heat (401.9KJ/mol and 241.1 KJ/mol) that increase the temperature inside the gasifier to 900 - 1,200 degrees C. This assists with burning off a substantial part of tars that would otherwise condense further downstream.


In the reduction zone, the thermal energy generated in the Oxidation zone is converted into chemical energy in the following reactions:

C + CO2<=> 2CO C + H2 O <=> CO + H2

CO + H2<=> CO + H2 O

C + 2H2<=> CH4

CO + 3H2<=> CH4 + H2 O

These reactions are endothermic and reduce the temperature of gas exiting the Oxidation zone as it passes through the bed of charcoal at the bottom of the gasifier. Producer gas in its final chemical composition is formed in this zone. Upon leaving the gasifier this gas has temperatures of 250-500 degrees C and can be fed to burners or, after additional cleaning and cooling, fired in internal combustion engines.

Advantage of Gasification

Biomass gasification plants offer several advantages relative to conventional combustion , solar and wind plants:

1.Opportunity to utilize wood and agricultural waste for energy generation and cut disposal cost

2.Cogeneration of heat and/or provision of cooling along with electricity

3.High efficiency, including small size facilities; Potential for more efficient conversion process when generating power

4.Weather independent

5.Producer gas can be used as a fuel in place of diesel in suitably designed/ adopted IC (internal combustion) engines coupled with generators for electricity generation or in many heating applications in the industry

6.large monetary savings can accrue through even partial substitution of diesel in existing DG (diesel generator) sets in dual fuel mode

7.Opportunity to substitute or co-fire natural gas, fuel oil and/or coal with low cost producer gas

8.Extended engine lifespan due to lower gas burning temperature relative to natural gas

9.Highly flexible - can be configured to cater for different feedstock types and energy requirements

10.Modular - a wide range of capacities; Can be applied over a range of output ratings (few to hundreds of kWs)

11.Low capital cost/investment & cost of power production

12.Lower NOx, CO, and particulate emissions

13.Virtual elimination of water needs if generating power without a steam turbine (close-coupled systems excluded)

14.Allows better process control and convenience

15.Elimination of all pollution related to Biomass use

16.Cleaner combustion in connected equipment