FI68084C - REFERENCE TO A FRAME RELEASE - Google Patents

Description

1 68084

This invention relates to a method and apparatus for producing an iron sponge.

5 Despite the fact that coal is one of the largest and also the cheapest energy raw materials, its use as a reducing agent in the manufacture of iron mushrooms has been very limited, i.e. despite the favorable price-to-energy ratio.

10 The processes known hitherto for the production of iron sponge, in which coal is used as a reducing agent, are essentially the following: (a) A rotary kiln process in which coal, together with the ore to be reduced, is used in inclined rotary kilns. The difficulty with this method is that, above all, due to the kinetics, it is necessary to work at a relatively high temperature, preferably above 1000 ° C, whereby great difficulties are encountered in the adhesion and accumulation of the material in the reaction space.

20 (b) Operation of a shaft furnace in combination with a coal gas plant based on partial combustion. The disadvantages of this known method are, above all, the very high investment costs of the gas plant and the particularly high energy consumption.

(C) According to Swedish Patent 7,304,332-5, a method for gasifying coal directly in solid form using a plasma generator is known. The disadvantage of this method is that it places very high demands on the accuracy and control of the carbon feed and that there are difficulties in handling coal ash for several grades of coal.

In addition, the hydrogen content of the generated gas is lower than what is optimal for the reduction.

It has now surprisingly been found that the above difficulties and disadvantages associated with the hitherto known procedures can be eliminated by the method according to the invention.

2 68084

The invention relates to a process for the production of iron sponge by continuously reducing iron oxides in a shaft furnace with a reduction gas directed countercurrent to the iron oxides, containing mainly CO and: such as coal, preferably coal. The process is characterized in that the recycle gas is washed in a CCl 4 -10 scrubber, the washed gas is fed in the form of a first partial stream to the plasma generator, the mixture in the form of reducing agent and water slurry is injected into the hot gas stream leaving the plasma generator, the outlet gas temperature is maintained between 1 ° C and 1500 ° C, that the ash portions contained in the solid reducing agent form slag, and the partial stream treated in the plasma generator is mixed with at least one other partial stream of scrubbed gas in such proportions that the temperature of the resulting final gas mixture is suitable for the reduction process.

700-1000 ° C, preferably 825 ° C, after which the remaining gas mixture is led to the bottom of the shaft furnace.

The invention also relates to an apparatus for use in the process described above, comprising a reaction space for an iron oxide-containing starting material and a reduction gas generation system. The apparatus is characterized in that the reduction gas generating system comprises a CO 2 scrubber for the reaction gas leaving the reaction space and a gas generation shaft connected thereto. for mixing the first substream into the second, untreated substream for the purified reduction gas and the final gas mixture obtained by the blowing member at the bottom of the reaction space.

Il 3 68084

According to one embodiment of the invention, the recycled gas is purified in a scrubber until its CO 2 content is suitably less than 2%.

The invention is described in more detail below with reference to an embodiment shown in the accompanying drawing.

The reduction of lump iron oxide takes place in the reduction shaft 1 by feeding the lump iron oxide 2 through the shut-off valve 3 in the shaft 1 and treating it countercurrently with a warm reduction gas consisting mainly of carbon monoxide and hydrogen gas. 5 using. The 30-50% used reduction gas is removed from the top of the shaft 1 via a gas outlet pipe 6. The gas removed from shaft 1 contains, in addition to the remaining CO and H 2 (50-70%), the reaction products CO 2 and H 2 O. Because this gas consistently contains relatively high concentrations of CO and ^, it is reused in the process. However, in order to be re-used as a reducing gas, the CO 2 and H 2 O content must be reduced to less than 5%. This is done by allowing the gas to pass through scrubber 7 (CCl 4 / H 2 O scrubbing). As the gas passes through this scrubbing, not only is the gas released from the reaction products CC> 2 and H 2 O, but said scrubbing procedure also makes it possible to balance the amount of gas, thus avoiding exhaustion of the gas.

After washing 7, the gas passes through the compressor 8 to achieve the pressure increase required by the process and is then divided into at least two substreams 9 and 10. The substream 9 at room temperature is fed to a gas generator 11 where the required additional gas is generated from a solid reducing agent, preferably coal and water. 35 days. The gas stream 9 is used in the gas generator 11 as plasma gas and is fed to the plasma generator 12 for the amount of energy required for the gas development process 4808084. to the hot gas stream flowing out of the plasma generator 12 in such a way that the carbon powder and the oxidizing agent are reacted to form CO and roads. The supply of energy to the gas generator 11 is regulated so that the ash present in the coal powder melts into slag 14, which can be removed 10 from the lower part of the gas generator 11 in liquid or solid form. Based on the composition of the ash, the temperature is suitably selected between 1300-1500 ° C. The reduction gas thus produced contains, in addition to CO and I 2, the sulfur contained in the reducing agent and is therefore passed through a sulfur filter 15, for example a dolomite filter, the sulfur content of which is reduced to an acceptable level in the iron sponge process, preferably below 75 ppm. cent.

Washing 7 may contain, for example, monoethanolamine as active ingredient, and during the washing the CO2 content of the gas may be suitably reduced to less than 2%.

The gas leaving the sulfur filter 15 is at a temperature too high for the iron sponge process and therefore the temperature of the gas is lowered by mixing cold, scrubbed partial flow gas 10 to a temperature suitable for the process 25, preferably up to 750-1000 ° C, suitably 825 ° C.

According to the invention, the following process technical advantages are achieved in the proposed manner.

A. Gas regeneration can take place at a temperature such that the ash forms an easy-to-handle slag that is emptied without causing a re-clogging problem in the process. The hydrogen content of the reduction gas can be controlled by washing to a suitable concentration of the reduction and the subsequent gas injection step of the gas regeneration step. In addition, gas scrubbing combined with gas evolution at elevated temperature il 5 68084 provides excellent opportunities for balancing the amount of gas in the system as well as controlling the reduction temperature. In this way, an energy-optimal reduction process and an easily controllable gas regeneration system are simultaneously overcome.

In the experiments carried out on an experimental scale, the following consumption values have been achieved per action of iron mushroom produced.

Electrical energy: 820 kWH. Coal powder: 172 kg.

B. In addition, according to the invention, a particularly simple control of the process itself is achieved, whereby also by generating the plasma gas by premixing the carbon powder and the addition of water in the right proportions, preferably in stoichiometric ratios, a simpler and more efficient control of the whole process can be achieved. With this premix of carbon powder and water, the mixture can also be easily sprayed as an aqueous emulsion of carbon.

If there are difficulties in binding the ash of the solid reducing agent to the slag phase, additions can be made that affect the properties of the slag, such as melting point, desulfurization ability, etc .; for example, alkali compounds and lime can be used.

It is appropriate to mix these additions with a solid reducing agent.

Appropriate gelling agents may also be added to stabilize the carbon-water mixture.

Furthermore, the supply of oxygen to the gas generator 11 can also be provided by means of oxygen gas instead of water.

Claims (9)

6 68084 A process for producing an iron sponge by continuously reducing iron oxides in a shaft furnace with a countercurrent reducing gas to iron oxides, containing mainly CO and H 2, the reduction gas being prepared from recycled shaft gas from the recycle shaft furnace and additional plasma gas produced , such as coal, preferably 10 coal, characterized in that the recycled gas is washed in a CO 2 scrubber, the washed gas is fed in the form of a first partial stream to the gas generator, the mixture in the form of a reducing agent and water slurry is injected into the hot gas stream leaving the plasma generator. the temperature is maintained in a range, preferably between 1300 ° C and 1500 ° C, that the ash portions contained in the solid reducing agent form slag, and the sub-stream treated in the plasma generator is mixed with at least one other sub-stream of scrubbed gas such as that the temperature of the resulting final gas mixture is suitable for the reduction process, i.e. 700-1000 ° C, preferably 825 ° C, after which the remaining gas mixture is led to the bottom of the shaft furnace. Process according to Claim 1, characterized in that a carbon powder, preferably a coal powder having a particle size of less than 0.85 mm, preferably less than 0.15 mm, is used as the reducing agent. Method according to Claims 1 to 2, characterized in that the gas 30 leaving the gas generator is passed through a sulfur filter. 4. Apparatus for producing iron sponge by continuously reducing iron oxides in a shaft furnace with a reducing gas directed countercurrent to the iron oxides, containing mainly CO and H2, the reduction gas being produced from 35 recycled shaft furnace effluent reaction gas 80 and additional gas produced by plas solid reducing agents such as coal, preferably coal, for carrying out the process according to claim 1, which apparatus comprises a reaction space (1) for an iron oxide-containing starting material and a reducing gas generating system, characterized in that the reducing gas generating system comprises a CC reactions: for the reaction gas leaving the child (1) and for the partial stream of purified reduction gas obtained from the gas generation shaft (11) connected thereto, the shaft comprising a plasma generator (12) and supply means (13) for supplying the reducing agent and water to the to a controlled gas plasma, and an adjustable mixing device for mixing the treated first sub-stream with the second, untreated sub-stream for purified reducing gas and the final gas mixture obtained by the blowing means at the bottom of the reaction space (1). Apparatus according to Claim 4, characterized in that the CC 4 scrubber contains monoethanolamine as active ingredient. 20 6. Apparatus according to Claims 4 to 5, characterized in that the compressor (8) is connected downstream of the scrubber (7). Apparatus according to Claims 4 to 6, characterized in that the lower part of the gas generation shaft (11) is provided with a discharge device for the slag. Apparatus according to one of Claims 4 to 7, characterized in that the sulfur filter (15) is arranged immediately after the gas generation shaft (11). Apparatus according to one of Claims 4 to 8, characterized in that the distribution element for the solid reducing agent and the water extends in the region in front of the plasma generator (12). 8 68084