Our Recycling Technology Combines Two Different Technologies into One
What Is Pyrolysis Recycling?
Pyrolysis is the thermal degradation of waste in an oxygen free environment, or in an environment in which the oxygen content is too low for combustion or gasification to take place. Pyrolysis recycling is a non combustion heat treatment that chemically decomposes waste material by applying heat (directly or indirectly) to the waste material in an oxygen free environment.
Pyrolysis is an endothermic reaction (unlike gasification and combustion, which are usually exothermic reactions) and requires an input of energy, which is typically applied indirectly through the walls of the reactor in which the waste material is placed for treatment.
Pyrolysis typically occurs under pressure and at operating temperatures above 430°C (800°F). The process generally produces char, oil and syn-gas, the ratios of each depending on the feedstock and the specific pyrolysis conditions (temperature, residence time, heating rate, pressure and degree of mixing) that are used.
There are a number of different kinds of pyrolysis processes which differ significantly with respect to residence time (for the waste material), heating rate, temperature and products produced. These range from carbonization, which can take up to 24 hours and produces coal from low temperatures, to flash pyrolysis, which takes less than a second and produces syn-gas at extremely high temperatures. A summary of the process conditions and products produced by the different pyrolysis processes is set out in the table below.
Kouei Industries offers several types of pyrolysis units, including the rotary kiln, rotary hearth unit, and the fluidized bed unit; some systems provide direct heat, others indirect, and both continuous feed and batch feed variations are available. Both the pyrolysis recycling and the gasification recycling processes turn waste into energy rich fuels by heating the waste under controlled conditions. By contrast to incineration, which fully converts the input waste into energy and ash, these processes deliberately limit the conversion process so that the waste products can be controlled, resulting in the waste material becoming valuable intermediate products that can be directly re-used in a variety of industries or processed further for more specific industrial application.
What Is Gasification Recycling?
Gasification is a process that uses heat, pressure, and steam to convert materials directly into gas. Gasification is a process that has been in use for many years and involves breaking down complex organic molecules and carbon, in both liquid and solid state, into simple gases.
Gasification is a thermal process but it is designed to produce a syn-gas as the main product, rather than the flue gas produced by a similar thermal process, combustion (i.e. incineration). The syn-gas largely comprises carbon dioxide and H2 and contains a large percentage of the inherent chemical energy of the input fuel.
Rather than treating waste in an oxygen free environment, as is the case when waste is pyrolysed, gasification occurs in the presence of a controlled amount of air, which is only sufficient to allow partial combustion of a small amount of the fuel input. The thermodynamics of the process are therefore very different from pyrolysis. Oxygen in the air aids the breakdown of the heavy organic compounds in the waste thereby optimizing the yield of syn-gas. Most of the gases produced are flammable and are therefore generally used as fuel in processes or applications where flammable gases are required. When mixed with air, syn-gas can be used in gasoline or diesel engines with minimal modifications required to the engine.
Our gasification technologies differ in several technical aspects but rely on four key engineering factors:
Typical raw materials used are coal, petroleum-based materials, and organic materials. 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. Most commercial gasification technologies do not use oxygen but all require an energy source to generate heat which starts the process.
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