The present invention relates to incineration systems, particularly those burning municipal garbage and waste, refuse-derived fuels, biomass, coal and petroleum coke, and/or chlorinated hydrocarbons. The present incineration systems are operated in a manner in which there is substantially zero release of toxic pollutants, such as dioxins and furans, into the environment. One preferred embodiment relates to a non-polluting method for burning fuel derived from typical municipal garbage and waste eliminating, or at least significantly reducing, the need for landfill disposal.
Coping with garbage generated by modern living is a serious global problem. In the United States municipal garbage is disposed of mainly into landfills that use up valuable land at a disturbing rate. The property value of land used in this manner depreciates tremendously and the land becomes practically useless. Furthermore, landfills are often criticized as being a health and an environmental hazard to those who live near them.
Much of the garbage taken to landfills is combustible and can be used to produce refuse-derived fuel (RDF). If certain types of materials, such as chlorinated plastics normally present in municipal waste, are not removed then toxic substances, such as dioxins and furans, can be formed and released into the environment if the RDF is burned in conventional waste-incinerating systems. This is the major reason for sending municipal waste to a landfill rather than converting it to RDF and utilizing it as fuel for producing electricity. Therefore, a practical and affordable method that will permit clean, non-polluting combustion of fuel derived from typical municipal waste is needed.
The burning of coal produces a significant portion of the world""s electricity. Also, large amounts of petroleum coke are burned to produce electricity. In North America, coal reserves are abundant and in North, Central and South America the production of petroleum coke continues to grow. Yet the U.S. continues to increase its crude oil imports. Presently, greater than fifty (50%) percent of the United States"" oil consumption is imported and much of that is used as fuel oil.
The technologies in use today to produce electricity, fuel and petrochemicals from coal and petroleum, create serious environmental problems. The burning of coal releases more of the greenhouse gas, carbon dioxide (CO2), into the atmosphere, per unit of electricity produced, than any other method for producing electricity. Burning coal to produce electricity also releases vast amounts of nitrogen oxides (NOx) into the atmosphere. New, affordable technology that will permit the burning of coal without releasing such large amounts of CO2 and NOx into the atmosphere is desperately needed.
There is also a need for modifying, or constructing, new incineration systems and valorization of chlorinated residual process units so that there is substantially zero discharge of toxic substances, such as dioxins, into the environment. While various technologies have met with some commercial success, there is still a need in the art for improved methods of incinerating materials, such as municipal waste with substantially zero emissions of environmental harmful substances.
In accordance with the present invention there is provided a process for incinerating combustible material in a process unit containing an incinerating zone, and a sorption zone containing a sorbent material. The combustible material is capable of producing an effluent stream containing environmentally hazardous components such as dioxins. The process comprises:
a) incinerating said combustible waste material in said incineration zone, thereby resulting in a high temperature gaseous effluent stream containing said environmentally hazardous materials;
b) reducing the temperature of said effluent steam to a temperature below that which will be deleterious to said sorbent material;
c) conducting said lowered temperature effluent stream to said sorption zone comprised of at least one bed of sorbent material capable of sorbing substantially all of said environmentally hazardous material from said effluent stream which sorption bed has a sorption capacity;
d) collecting or venting said effluent stream which is substantially free of environmentally hazardous material;
e) reactivating said one or more sorbent beds with a reactivating agent when said one or more sorption beds reaches a predetermined capacity for sorbing said environmentally hazardous material; and
f) conducting said reactivating agent, containing said environmentally hazardous material, to said incineration zone of step (a) above, wherein said environmentally hazardous material is decomposed by combustion.
In a preferred embodiment of the present invention the combustible material is selected from the group consisting of municipal waste, refuse derived fuel, biomass, and a waste material containing chlorinated hydrocarbons.
In another preferred embodiment of the present invention the effluent stream leaving the heat exchanger contains particulate matter which stream is passed to a particulate separation unit wherein at least a portion of said particulate matter is removed from said effluent stream.
In yet another preferred embodiment of the present invention the sorbent beds are comprised of at least one adsorbent selected from the group consisting of activated carbon, charcoal, molecular sieves (zeolitic materials), aluminas, silicas, and both graphitic and non-graphitic carbon nanostructures.