Gasification Process
Gasification is a commercial, flexible and reliable technology. It turns a variety of low-value feedstock into a high-value product. It help to reduce a country's dependence on imported fossile fuels e.g. oil and natural gas and can provide a clean alternative source of electricity, fertilizers, fuels and chemicals.
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It is a process that converts any materials containing carbon - such as waste, biomass, coal, petcoke, ... - into a synthesis gas (Syngas). The Syngas can be used in a gas engine to produce electricity or heat or further processed to manufacture chemicals, fertilizers, liquid fuels, substitute natural gas (SNG), or hydrogen.
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The gasification process has been reliably used on a commercial scale worldwide for more than 60 years.
Gasification is not incineration!
Gasification is increasingly used to convert municipal solid waste (MSW) into high-value form of energy. For decades this type of waste has been burned or incinerated to create heat and electricity. The gasification process represents significant advances over incineration.
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To understand the advantages of gasification, it is important to understand the significant differences between the two processes.
Incineration:
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Incineration uses MSW as a fuel. The incineration process needs high volume of air to form carbon dioxide and heat. That heat is used in a waste-to-energy plant to make steam, which is then used to generate electricity.
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In addition, one of the concerns with incineration of MSW is the formation and reformation of toxic dioxins, furans and other harmful substances like nitrogen oxides and ammonia. Especially PVC-containing plastic and other materials that form dioxins and furans when they burn. These toxins end up in exhause steams by three pathways:
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By decomposition, as smaller parts of large molecules,
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By reforming when smaller molecules combine together and/or
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By simply passing through the incinerator without change.
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Incineration does not allow control of these processes and all clean-up occurs after combustion.
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Gasification:
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The gasification is generating a syngas. That is which makes gasification so different from incineration. The waste in the gasification process is not a fuel, it is a feedstock for a high temperature chemical conversion process.
In the gasifier, the MSW reacts with only a little oxygen (partial combustion) to generate the necessary energy for the chemical reactions. The energy is used to breaking down the feedstock into simple molecules and converting them into syngas. Instead of making just heat and electricity, as is done in a waste-to-energy plant using incineration, the syngas produced by gasification can be turned into high valuable commercial products as fuels and chemicals.
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Gasification converts MSW to a usable synthesis gas, or syngas.
Gasification is significantly different and cleaner than incineration
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In the high temperature environment of the IMRG gasification and the IMRG plasma treatment, larger molecules such as plastics and tars are completely broken down into the components of syngas, whitch can be cleaned and processed before any further use.
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Dioxins and furans need sufficient oxygen to form or reform. The oxygen-deficient atmosphere in a gasifier does not provide the environment needed for dioxins and furans to form or reform. In addition, the high temperatures in the IMRG plasma treatment (more than 1200°C) would destroy existing dioxins.
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In the IMRG gasification plant the syngas ist quickly cooled down, so that there is not sufficient residence time in the temperature range where dioxins or furans could reform.
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When the syngas is primarily used as a fuel for making heat, it can be cleaned as necessary before combustion. This cannot occur in incineration.
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The ash produced from IMRG gasification is different from what is produced from an incineration.
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While incinerator ash is considered safe for use only as alternative daily cover on landfills, there are concers with its use in commercial products.
In the high-temperature IMRG gasification, the ash actually flows from the gasifier in a molten form, where it is cooled and forms a glassy, vitrified, non-leachable slag that can be used for making cement, roofing shingles, or used as an asphalt filler or sandblasting. The IMRG gasifier is designed to recover melted metals, taking advantage of the ability of gasification technology to enhance recycling.