Gasification

What is Gasification?

Gasification is a process that uses heat, pressure and steam to convert materials directly into a gas composed primarily of carbon monoxide and hydrogen. Typical raw materials used in gasification are coal, petroleum-based materials, and organic materials (e.g., food waste, agricultural waste, wood). The feedstock is prepared and fed, in either dry or slurried form, into a sealed reactor chamber called a gasifier. The feedstock is subjected to high heat, pressure and either an oxygen-rich or oxygen-starved environment within the gasifier.

Gasification is a flexible, reliable and clean energy technology that can turn a variety of feedstocks into high-value products, help reduce dependence on oil and gas, and can provide a clean alternative source of electricity, fertilizers, fuels, and chemicals.

The process of gasification converts carbonaceous materials into carbon monoxide and hydrogen by reacting raw materials at high temperatures with a controlled amount of oxygen. The resulting mixture is called synthesis gas or syngas. Syngas can be used to generate electricity and heat or transformed into a diesel-like synthetic fuel via the Fischer Tropsch process.

According to the Gasification Technology Council in the United States, gasification has been reliably used on a commercial scale worldwide for more than 50 years in the refining, fertilizer and chemical industries, and for more than 35 years in the electric power industry.

Process of Gasification

In simple terms, a typical process of gasification works as follows: the feedstock material (e.g., biomass, such as wood) is fed into a grinder from where the material is fed into the pre-pyroliser for preheating. Next, the material flows into the pyroliser where the temperature is much higher and where the structure of the material changes from solid to liquid to gas within a few seconds; this is how the syngas is produced. The carbon-rich

residue is then transformed to hydrogen by injecting superheated steam. The resulting biogas undergoes a cleaning process: first, the solid particles are taken out, then the remaining very light particles are removed, and finally tars and oils are removed in the liquid condensing section of the equipment. After this cleaning process, the biogas goes through a final metallic filter, resulting in clean syngas which is used to power the generators to produce clean, green electricity. Any minor residue from this process is returned to the start and undergoes the same procedure again. The majority of the residue is then converted into syngas; when returned to the start of the process, it turns into semiliquid gas and converts into syngas during its second passage through the gasification process. The remaining approximately 4% of residue is dust that can be mixed with compost and used as agricultural fertilizer. Thus, using biomass for the gasification process is a clean, green, environmentally friendly method of producing electricity in a sustainable manner. It is for this reason that power generation via gasification is eligible for ROCs (Renewable Obligations Certificates) in the United Kingdom and REC (Renewable Energy Certificates) or CERs (Certified Emissions Reductions) in other parts of the world.