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Development of a gas destructor.

The aim of the project is to develop, design and construct a
thermic destructor in which hazardous substances of type
pcdd, pcdf and pcb will be destroyed.

Plastic, cellulose and other wastes can be disposed of by various methods. The two most essential methods are represented by thermic, either high temperature or low temperature, destruction. High temperature disposal (combustion under approximately 1500 degrees C.) is a very demanding method in terms of energy which results into construction of large facilities with high investment cost (the combustion plant should contain a technology of separation of solid particles and chemical washing of gases, which means high demands both in terms of investment cost and appropriate operation). Operation of such facility is only possible at a place with a great amount of sorted wastes in a relatively small area. The collection of wastes from a distance over 50 km swallows up all funds for disposal. A low temperature pyrolysis at a temperature of about 600 degrees C. is almost sufficient in a point of view of energy consumption. Wastes are disposed at a temperature about 600 degrees C. in a rotary reactor, indirectly heated by waste gases, operating in moderate excess pressure. In the course of pyrolysis, thermal destruction of polymers occurs, releasing the gas, containing especially low temperature boiling hydrocarbons and water steam, and approx. 10% of steams of pyrolysis oil. The pyrolysis oil is discharged from the reactor to further processing and use. Solid pyrolysis rests consist of coke and impurities from wastes processed and these are discharged from the lower part of the reactor. Low operation cost enables the construction of small pyrolysis units where only wastes from the nearby surrounding are disposed (approximately 30 km). A shortage is generation of highly toxic substances (PCDD, PCDF, PCB) which have been disposed up to now using a very much more demanding technology of chemical washing of waste gases. The cost to purchase and operate subsequent facilities for disposal of harmful substances in waste gases following the respective pyrolysis is so high that the technology is not commercially usable. A technical solution for the Project is a high temperature destructor of waste gases which would reduce chemical washing to economically acceptable minimum, thus enabling construction of a commercially usable small incinerator of plastic and other wastes based on polymers. The appropriate thermic destructor consists of an excess pressure combustion chamber, two fuels burner and ceramic grid situated at the exit from the incineration chamber. In a simplified way, a principle of the technological process of thermic destruction of combustible substances can be expressed as follows: Combustible substances are led to a burner where they mix with combustion air and burn out (a form of direct combustion), or they are led in a mixture with the air to the incineration chamber as a secondary air lock. Due to induced reaction, they achieve high activation energy in a flame or in contact with the burner flame. Activated molecules initiate a development of energy chains of degradation. Following substances are generated: radicals CH*, CH2*, CH3*, CO, formaldehyde, acetaldehyde etc., followed by their oxidation. Hot waste gases containing activated molecules and radicals, following their not complete thermic disposal, enter the inner structure of porous ceramic mass of three-dimensional network and fibrous morphology. Hot waste gases come in contact with a developed porous microstructure of ceramic fibres causing a so-called 'wall effect', interruption of chains of destruction, completion of oxidation reactions and de-activation of active particles. The higher activation energy of an induced reaction and the lower the temperature, the higher the size of pores or channels permissible. Process stability increases while a diameter of pores or decreases or while porosity of the ceramics increases, i.e. while specific surface increases. The above stated method is supposed to be applicable also for a thermic destruction of substances classified as a sum of PCDD and PCDF, and, further, PCB. (PCDD - poly- chlordibenzendioxin PCDF -polychlordibenzene for any PCB -polychlorbifenyl). The efficiency of the thermic destruction of those substances should be verified. A construction of the destructor partially consists in a technical design of a designer, and partially in an experimental proving of the process. Thus, a procedure of construction will be divided into several steps, when a test facility will be proposed and produced, on which measurement will be made which will affect a further construction of the destructor. This process will be repeated several times. A heat exchanger which will enable to use the energy (technological steam, hot water steam or hot water heating) generated during destruction, should be a part of the destructor. Since the heat exchanger significantly influences passage of hot gases through the destructor, there is a supposition of significant changes also in its construction evoked by changes in the main combustion space of the destructor. The destructor should be provided by analysers of waste gases and temperature sensors. Their choice and location will be another technically demanding process. Outputs from sensors and analysers will be transmitted through appropriate interfaces to a control computer. The computer will communicate with a control system of the pyrolysis unit (regulation of quantity of input waste gases), then it will control the appropriate process of destruction in the thermic destructor (performance power and temperature of a stabilizing flame) and control any parameters of the heat exchanger. It is supposed that it will be necessary to create an independent and completely unique programme for controlling of the whole process. The programme should contain, in addition to control elements, graphic outputs for operation, recording of any conditions of the destructor in terms of time and operation of other safety functions. Constructional and production works related to the modification of gas washing as the last stage of disposal of harmful substances produced in the process specified will be a part of the destructor.
Acronym: 
DESTHERM
Project ID: 
2 717
Start date: 
01-03-2002
Project Duration: 
36months
Project costs: 
940 000.00€
Technological Area: 
Incineration and Pyrolysis
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.