Metallgesellschaft Aktiengesellschaft

Georg Schaub

Rainer Reimert

Hans Beisswenger

Johannes Loffler

Gebhard Bandel

Guenter Reiss

Alfred Karbach

Rolf Peters

The process purifies exhaust gas produced by combustion of waste materials including garbage, industrial wastes and/or sewage sludge. The exhaust gas is contaminated particularly with dust, SO.sub.2, HCl, HF, Hg, mercury compounds, and dioxins and furans and can be expected to have an oxygen content. In the process, the exhaust gas is treated in a spray absorber with a suspension of Ca(OH).sub.2 ; the exhaust gas is subsequently filtered in two successive filteration stages; the exhaust gas leaving the first filtering stage still has an SO.sub.2 content of from 20 to 500 mg/sm.sup.3 ; activated carbon, preferably hearth furnace coke, is introduced into the exhaust gas stream before the second filtering stage; and the exhaust gas is finally scrubbed with a mixture which contains water and NaOH, Na.sub.2 CO.sub.3, Ca(OH).sub.2 and CaCO.sub.3 in a dissolved or suspended state.

Process of purifying exhaust gases produced by combustion of waste

The waste materials are gasified in a circulating fluidized bed in a gasification reactor, which is supplied with oxygen-containing gas. A gas-solids mixture is withdrawn from the upper region of the gasification reactor and is fed to a separator. Dust-laden gas and separated solids are separately withdrawn from the separator and the separated solids are recycled at least in part to the lower region of the gasification reactor. Temperatures in the range from 700.degree. to 1000.degree. C. are maintained in the gasification reactor. The dust-laden gas which is withdrawn from the separator has a heating value of about 3000 to 6000 kJ/sm.sup.3 and is fed to a combustion chamber and is combusted therein at temperatures from 1200.degree. to 1900.degree. C. Liquid slag is withdrawn from the combustion chamber.

Process for gasifying waste materials which contain combustible

Granular coal is combusted in a circulating fluidized bed system comprising a combustion chamber, a separator and a recycle line for recycling solids from the separator to the combustion chamber. Gas from carbonization is added to the oxygen-containing combustion gas withdrawn from the combustion chamber and is at least partly combusted in said combustion gas to increase the temperature of the combustion gas to about 850.degree. to 1200.degree. C. The gas from carbonization is produced by the heating of granular coal.

Process of combusting coal in a circulating fluidized bed

The production of water vapor is controlled in a plant for combusting fine-grained and dustlike solid fuels together with air in a combustion zone of a heat exchanger in the upper region of the combustion zone, a water vapor accumulator, which communicates with the heat exchanger, and a water vapor feed line leading from the water vapor accumulator to a turbine. The rate at which water vapor is produced is continually calculated and is compared with the desired value which is required by the turbine and the rates at which fuel and combustion air are supplied to the combustion zone are adjusted in accordance therewith. The combustion plant may comprise a fluidized bed cooler for cooling a part of the part of the combustion residue. That cooler may comprise a plurality of chambers provided with heat exchangers for an evaporation of feed water or for a super heating of water vapor. Any water vapor which is produced from feed water in said chambers will also be taken into account in the calculation of the total rate at which water vapor is produced in the combustion plant.

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Oberursel, Germany

Georg Schaub