FI75792B - FOERFARANDE FOER FRAMSTAELLNING AV SVAVELDIOXID. - Google Patents

Description

1 75792

The present invention relates to a process for the production of sulfur dioxide by roasting sulfur pyrite in a fluidized bed reactor and cooling and optionally drying the reaction gases.

It is known to produce sulfur dioxide by roasting finely divided coals with a particle size of 0.1-5 mm in Lei fluidized bed reactors. There are no specific problems in this process. The heat of reaction must be partially conducted away from the fluidized bed. This can be done either by means of cooling pipes, producing steam, or by separately feeding metal sulphates or spent sulfuric acid to the fluidized bed, the thermal decomposition of which into sulfur dioxide, water, oxygen and metal oxides is highly endothermic.

Since finely divided coals with a low level of heavy metal impurity are hardly available anymore, flotation coils with a particle size of less than 0.1 mm must be increasingly used for roasting.

20 The disadvantages associated with the use of flotation nozzles are two in particular: flotation nozzles with a water content of 4-8% tend to adhere to sloping surfaces, which can lead to blockages in tanks, feeders and reactor feeders and thus downtime. This gluing can be avoided by using drier flotation strips, but excessive dusting will occur.

In addition, flotation guns fly easily away from the fluidized beds. In this case, the particles burning at the top of the reactor can chase oxides into the sintering outlet of the reactor.

Finally, as a result of the high solids removal, too little coarse-grained layer material is formed during the sintering of the formed metal oxide particles. However, this is necessary to maintain a steady supply of air to the furnace and mixing of both the flotation cap and possibly the sulphates 2 75792 and the acid used. This problem can be partially reduced by reducing the air supply to the reactor. In this case, however, the capacity is reduced and new problems also arise due to the weakening of the mixing.

5 The problems described are combated by moistening flotation gels with water. However, this operation greatly degrades the economics of the process, as the heat of vaporization of this additional feed water is lost to process steam generation or sulfate / sulfur-10 acid decomposition.

It is therefore an object of the present invention to provide an economical method which does not have the disadvantages described above.

It has now been found that the disadvantages described can be eliminated by feeding sulfur reactor into the reactor as a suspension consisting of flotation fuel and sulfuric acid.

The present invention thus relates to a process for the production of sulfur dioxide by roasting sulfur pyrite in fluidized bed reactors and cooling and optionally drying the reaction gases, in which process the sulfur pyrite is fed to the fluidized bed tractor as a suspension consisting of flotation pyrite and sulfuric acid.

The weight ratio of flotation gel to sulfuric acid in this suspension should be 5: 1 to 1: 5, especially preferably 3: 1 to 1: 1.

The sulfuric acid used in the present invention should have an H2SO4 content of at least 20%, preferably 40-90%. Sulfuric acid may contain metal sulphates and / or organic compounds.

Thus, spent sulfuric acid can be used. Thus, the preparation of its suspension was subject to reservations due to the fineness of the flotation or the corrosivity of sulfuric acid. In a preferred embodiment, the flotation solids are mixed with sulfuric acid immediately before being fed to the reactor. Thus, the flotation ore taken from the tank, possibly together with preferred other substances, carbonaceous fuels, sulfur or other raw materials, can be transferred to a plastic-lined shaft.

The walls of this shaft are rinsed with spent sulfuric acid, thus avoiding the adhesion of the cat. The lower part 5 of the shaft communicates with the funnel of the injector, through which the ore together with the acid is blown with compressed air into the fluidized bed reactor.

The metal sulphate content of the sulfuric acid used is irrelevant, as long as the high viscosity does not impede the injection.

The advantages of the process according to the invention compared to the known processes can be seen in that the process energy is not used for the evaporation of "kite feed water". In addition, the need for cooling water in the cooling of the process gases is lower, because the "kite feed water" does not need to be condensed. The capacity to decompose metal sulfates or spent sulfuric acid will increase significantly. The production capacity of SC ^ s increases relatively even more, because the decomposition of the "pyrite feed acid" also generates C> 2 for SC ^ li-20, which can still react with sulfur pyrite.

Roasting of sulfur pyrite takes place substantially more strongly in the fluidized bed than when feeding the pyrite with water. This results in a marked increase in the formation of coarse layer-25 material, a uniform temperature distribution in the layer, and a relative increase in the temperature of the fluidized bed relative to the gas space.

The capacity of fluidized bed reactors can be further increased by mixing oxygen into the roasting air. The thermal decomposition capacity of metal sulfates or sulfuric acid can be increased by using carbonaceous fuels that can be fed to the reactor together with the sulfur pyrite or separately.

The advantages of the invention will become apparent from the following examples, which are not intended to limit the invention.

4,75792

Example 1 (comparative example) 2

A fluidized bed reactor with a 12 m grate surface was fed with 7.5 t / h flotation strip containing 5% moisture. In this case, the cat was taken from the tank with an adjustable traction belt-5a and transferred downwards into a conically converging shaft. From the shaft, the kitten fell into the injector funnel and was blown into the fluidized bed reactor at 500 nf * n / h air. In order to avoid interference and interference caused by the cat falling irregularly from the shaft, 800 1 / h of water had to be sprayed into the shaft 10. 3 18,000 m n / h air was fed to the fluidized bed reactor; from the side, 0.65 t / h of metal sulfates were fed to the fluidized bed at 2.6 t / h of 65% sulfuric acid.

The temperature of the strongly pulsating fluidized bed was 0.3 m above the grate at 800-850 ° C. The temperature at the reactor outlet-15 sa was measured at 1050 ° C. The reaction gas contained 20% SO 2 and 1% C> 2 (v / v dry gas).

With a pressure drop in the grate and the fluidized bed of 0.15 bar, an average of 20 kg / h of bed material left the reactor. 6 t / h of fine combustion waste was removed from the waste heat boiler and the gas cleaning equipment.

SO2 production was 10.7 t / h.

Example 2

According to Example 1, a 7.5 t / h flotation jet with a moisture content of 25% was fed to the fluidized bed reactor. Instead of rinsing the shaft walls with water (800 l / h), they were rinsed with 90% sulfuric acid containing organic impurities (2 t / h). 18,000 m n / h air was fed to the fluidized bed reactor; 1 t / h of molten sulfur and the same amount as in Example 1 of a metal sulfate-sulfuric acid suspension were fed to the bed from the side.

The reaction gas contained 23% by volume of SC> 2 and 1% by volume of O 2. The SO 2 production was 12.4 t / h. The temperature was 900-920 ° C above the grate and 950 ° C at the reactor outlet.

With a pressure drop of 0.17 bar, an average of 450 kg / h of coarse combustion waste 5,75792 and 5.5 t / h of finer combustion waste were removed from the fluidized bed 35 reactor and from the waste heat boiler and gas cleaning equipment.

Example 3

The following changes were made to Example 2; 5 In the stripping step, 90% sulfuric acid was replaced by a metal sulfate-sulfuric acid suspension. This suspension was fed a total of 7.3 t / h with the addition of 1.5 to 3 t / h. Except that the temperature at the reactor outlet.

10 decreased from 950 ° C to 930 ° C, no significant changes in operating conditions were observed compared to Example 2.

Claims (8)

Process for the production of sulfur dioxide by roasting sulfur pyrite in fluidized-bed reactors and cooling and optionally drying the reaction gases, characterized in that the sulfur pyrite is fed to the fluidized-bed reactor as a suspension consisting of flotation flux having a particle size of less than 0.1 mm and sulfuric acid. Process according to Claim 1, characterized in that the weight ratio between the flotation strip and the sulfuric acid is 5: 1 to 1: 5, particularly preferably 3: 1 to 1: 1. Process according to Claim 1 or 2, characterized in that the sulfuric acid content is at least 20%. Process according to one of Claims 1 to 3, characterized in that the sulfuric acid content is 40 to 90%. Process according to one of Claims 1 to 4, characterized in that the sulfuric acid contains metal sulphates. Process according to one of Claims 1 to 5, characterized in that the sulfuric acid contains 25 organic compounds. 6 75792 Method according to one of Claims 1 to 6, characterized in that carbonaceous fuels are mixed with the sulfur fuel. Process according to one of Claims 1 to 7, characterized in that the sulfuric acid-sulfur fiber suspension is fed to the fluidized-bed reactor by means of air blowing.