Incineration as a fuel source
Friday, 21 July, 2006
Domestic waste, old car wheel casings, industrial wastes and even silt that remain after cleaning sewage outflows can successfully be turned into light and heat when incinerated, under methodology developed by scientists from Chernogolovka in the Moscow Region and staff from the Institute of Problems of Chemical Physics RAS. The scientists were aided by the International Science and Technology Centre and the Russian Fund for Fundamental Research. The research is headed by RAS Corresponding Member Georgi Manelis.
This technology has a rather complicated name - filtration combustion with superadiabatic warm-up. The essence of the development lies in the fact that all of the so-called pseudo-fuel is first transformed to gas in an airflow, then this gas is combusted. As a result we get the same light and heat for which to date it has been necessary to literally let natural gas, coal and oil go up in smoke - fuel reserves which are far from endless in supply.
Externally the main part of the installation is a vertical shaft furnace, filled with these waste products that have to be processed. From below, the pipe is blasted with air. This is where the ash is poured in - the mineral residue that does not burn at all. From above, as necessary, new portions of what in a domestic sense you would not call fuel are added into the pipe; these include poor coal, for example, in which there is so little carbon that you cannot make them burn easily.
The particular feature of the installation is that the walls of the shaft furnace, the gasifier, do not allow even a little of the heat obtained from the combustion of the waste to disperse into the surrounding space. From below the front of smouldering rather than burning, air blows heated ash onto the lower sections of the pipe. As a result the temperature of the process becomes pretty high, superadiabatic, meaning it is greater than under regular heating in a closed space. And now it is sufficient for all the compounds which contain carbon atoms to either burn or be subjected to pyrolysis, as if splitting into pieces, which is what happens if there is insufficient oxygen for combustion. The soot from burning car wheel casings that we all know well is indeed the very same product of this pyrolysis, only in the installation devised by the scientists, they enter at the second stage of the reprocessing.
Thus, at the first stage gasification takes place in superadiabatic regime; in other words, the transformation of carbon-containing wastes into so-called generating gas. The molecules that make it up store a fair amount of heat and the non-combustible slag has already poured into the bottom of the furnace. A gas like this will combust wonderfully in a power-generating installation, giving the much needed heat and electricity.
"Our method has very high performance efficiency, almost 95%, and a record high ecological cleanliness," explains candidate of physics and mathematics Valery Steinberg, head of department of combustion and detonation of the Institute Problems of Chemical Physics RAS, where the basis of the technology was created. Such incineration, performed in phases, and the high temperatures facilitate the practical suppression of the formation of dioxins. Their content in the furnace gases, without any additional purification, amounts to ten-thousandths of a microgram per cubic metre of smoke; an excellent figure."
What is also surprising is that the method is non-demanding in terms of the primary fuel. Naturally, the air supply regime and certain other parameters have to be selected for each specific type of waste that predominates in the combustible mass. However, under the new technology, almost everything burns: domestic rubbish, oil slime and oil-refinery wastes, wheel casings, plastic, just as wastes from the coal mining and coal refinery, pulp and paper, chemical and paint-varnish industries, providing us with heat and with light.
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