Metallgesellschaft Aktiengesellschaft

Other

Lafarge Coppee

Creusot-loire Enterprises

Hans-Werner Schmidt

Martin Hirsch

Lothar Reh

Hans Beisswenger

Harald Sauer

Walter Koch

Yilmaz Yetmen

Karlheinz Rosenthal

Albert Folliot

Wolfram Schnabel

Wolfgang Fennemann

Ludolf Plass

Martin Rahn

Bernd Erkes

Marc Schnell

Horst Heisswolf

Maurice P Iard

Maurice Paliard

A process for adjusting a circulating fluidized bed, wherein a part of the carrier gas is recovered, mixed with a propellant and returned to the fluidized bed as a carrier gas.

Method of adjusting a circulating fluidized bed and use of the method

In a method of processing contaminated sodium oxalate which becomes available in a separating stage succeeding the digestion of bauxite in accordance with the Bayer process, chemicals used in the digesting process are recovered in that moist sodium oxalate which has been separated is dried with the hot exhaust gases from a rotary kiln jointly with aluminum hydroxide or aluminum oxide hydrate and/or reactive alumina at a mole ratio of aluminum to sodium of at least 0.8 and the dried product is decomposed in said rotary kiln at a temperature of 780.degree. to 1000.degree. C. to form sodium aluminate. Suitably drying is effected by spray drying in direct contact with the exhaust gases of the rotary kiln and decomposition is effected at a temperature in the range from 850.degree. to 950.degree. C. and with an Al:Na ratio not in excess of 1.2.

Method of processing sodium oxalate formed during the digestion of

In a method for processing contaminated sodium oxalate which becomes available in a separating stage succeeding the digestion of bauxite in accordance with the Bayer process, chemicals used in the digesting process are recovered in that the moist sodium oxalate which has been separated is dried with the hot exhaust gases from a fluidized bed, particularly a circulating fluidized bed, jointly with aluminum hydroxide or aluminum oxide hydrate and/or reactive alumina at a mole ratio of aluminum to sodium of at least 0.8 and the dried product is decomposed in said fluidized bed at a temperature of 780.degree. to 1000.degree. C. to form sodium aluminate. Suitably drying is effected by spray drying in direct contact with the exhaust gases of the fluidized bed and decomposition is effected at a temperature in the range from 850.degree. to 950.degree. C. and with an Al:Na mole ratio not in excess of 1.2.

A process of removing pollutants from exhaust gases in a circulating fluidized bed, in which solids are circulated through a fluidized bed reactor, separated in a separator and returned via a return line, to the reactor. The exhaust gas is introduced as a fluidizing gas into a fluidized bed which consists of two solid fractions differing in particle size, namely, a coarse-grained fraction having a particle size d.sub.p 50 in the range of 150 to 500 microns and a fine-grained fraction having a particle size d.sub.p 50 below 10 microns.

Process of removing pollutants from exhaust gases

A process for afterburning and purifying process exhaust gases, which contain combustible constituents, wherein the process exhaust gases and the oxygen-containing gases required for a combustion are separately supplied to a fluidized bed reactor of a circulating fluidized bed. In the fluidized bed reactor, the gas velocity is adjusted to 2 to 10 m/s (empty pipe velocity), the mean suspension density is adjusted to 0.1 to 10 kg/m.sup.3, the temperature is adjusted to 700.degree. to 1100.degree. C., and the stoichiometric ratio of gas-purifying agent having a particle size d.sub.p 50 of 30 to 200 .mu.m to pollutant contained in the process exhaust gas or formed by the combustion is adjusted to 1.2 to 3.0, calculated as Ca:S. The entrained solids in the gases from the fluidized-bed reactor are recycled to the reactor at a rate of at least 5 times the weight of solids contained in the fluidized bed reactor per hour.

Process of afterburning and purifying process exhaust gases

Cement clinker is produced in that raw cement powder is preheated in a suspension-type heat exchanger and is de-acidified in a fluidized bed and clinkered in a rotary kiln, and the clinker is subsequently cooled. A de-acidification of at least 95% is effected at a temperature above 850.degree. C. in a circulation system comprising a fluidized bed reactor, a cyclone separator and a recycling duct. The carbonaceous fuel required for the calcining and clinkering processes is fed in an amount of at least 65% (related to the total heat requirement) to the de-acidifying fluidized bed reactor and in an amount of at least 10% (related to the total heat requirement) to the clinkering rotary kiln. The fuel supplied to the de-acidifying fluidizing bed reactor is burnt near stoichiometrically in two stages with fluidizing gas and secondary gas. The ratios of the rates and volumes of fluidizing gas to secondary gas are so selected that a mean suspension density of 100 to 300 kg/m.sup.3 is maintained in the zone between the inlet for fluidizing gas and the inlet for secondary gas, and a mean suspension density of 5 to 30 kg/m.sup.3 is maintained above the inlet for secondary gas.

Method of producing cement clinker

Cement clinker is produced in that raw cement powder is preheated in a suspension-type heat exchanger and is de-acidified in a precalcining apparatus and clinkered in a fluidized bed and the clinker is subsequently cooled. An de-acidification of at least 95% is effected at a temperature above 85.degree. C. in a circulation system comprising a fluidized bed reactor, a cyclone separator and a recycling duct. The carbonaceous fuel required for the calcining and clinkering processes is fed in an amount of at least 65% (related to the total heat requirement) to the de-acidifying fluidized bed reactor and in an amount of at least 10% (related to the total heat requirement) to the clinkering fluidized bed reactor. The fuel supplied to the fluidizing bed reactor is burnt near stoichiometrically in two stages with fluidizing gas and secondary gas. The ratios of the rates and volumes of fluidizing gas to secondary gas are so selected that a means suspension density of 100 to 300 kg/m.sup.3 is maintained in the zone between the inlet for fluidizing gas and the inlet for fluidizing gas, and a mean suspension density of 5 to 30 kg/m.sup.3 is maintained above the inlet for secondary gas.

Process of producing cement clinker

Endothermic processes are carried out in a fluidized-bed reactor which is connected to a holding reactor, solids being recirculated between the two reactors. The primary fluidized-bed reactor uses a fast-fluidized bed system in which the solids concentration decreases continuously from the bottom to the top of the reactor. After the necessary residence time in the holding reactor, solids are discharged. Solids are entrained with the gas stream from the primary reactor and are separated therefrom to be delivered to the holding reactor. The reaction is controlled by regulating the rate of recirculation of solids from the holding reactor to the fast fluidized bed reactor.

Growing community of inventors

Frankfurt am Main, Germany

Hans-Werner Schmidt