KR850001632B1 - Method for manufacturing sponge iron - Google Patents

Abstract

Disclosed are a method and apparatus for manufacturing sponge iron by the continuous reduction of iron oxides in a shaft utilizing recirculation gases. A reducing agent such as pit coal is injected together with an oxidant into the hot gas from the plasma burner in order to form a gas mixture comprised primarily of CO and H2, which gas mixture is then mixed with the other flow portion of the cleaned reaction gas in such proportion that the temperature of the resulting reduction gas is suitable for the reduction of iron oxides in the shaft furnace.

Description

Method for producing reducing gas required for the manufacture of sponge iron

Process schematic diagram illustrating the practice of the present invention.

The present invention relates to a method for producing spongy iron, and in particular, the present invention relates to a method for producing the reducing gas required for the production of spongy iron by continuously reducing the iron oxide in the furnace using a recycle gas. A conventional method for producing spongy iron using a solid reducing agent such as coke as the reducing agent is as follows.

1) The rotary furnace method used with the ore to reduce coal in the inclined rotary furnace, the difficulty of this method is that it is necessary to operate at a relatively high temperature, preferably 1000 ℃, mainly because of the kinetic energy, This causes various problems that can accumulate and block material in the reaction chamber.

2) The method of using a shaft combined with a coal gasifier based on partial combustion. The disadvantages of this method are firstly very high facility costs for the gasifier and exceptionally high energy consumption.

3) Method of directly gasifying coal in solid form using a plasma generator (refer to Kingdom Patent No. 73 04 332-5, the disadvantage of this method is that the supply of coal must be controlled very precisely, Is problematic in handling ash, and the resulting gas has a lower hydrogen content than ideal for the purpose of reduction.

Disadvantages and other problems in the above various methods can be almost solved and supplemented by the method of the present invention. That is, the method according to the present invention removes the reactant gas from the shaft, removes almost all CO ₂ and H ₂ O from the reactant gas above, and divides the reactant gas into at least two flows; One of the two flow sections is sent to a gas generator consisting of a gas generating shaft almost filled with a solid reducing agent, a plasma burner mounted on the lower portion of the gas generating shaft, and an oxidant injecting mechanism, and the reaction gas is heated by a plasma burner. The oxidant is then injected into the heated gas exiting the plasma burner to form an intermediate gas mixture consisting primarily of CO and H ₂ , and maintaining the above intermediate gas mixture at a temperature at which ash contained in the solid reducing agent can form slag. And mix the intermediate gas with at least one of the two flows at a rate such that the temperature of the reducing gas formed is suitable for the reduction of the iron oxide in the shaft, and the reaction gas is injected into the bottom of the shaft and then Sent to the upper part to reduce the iron oxide contained in the shaft, and reduced iron in the shaft By continuously reducing the iron oxide in the shaft tunnel, characterized by a collection box manufacturing method of the reducing gas required for the sponge iron produced.

In this process, the reducing gas consists mainly of CO and H ₂ and is sent countercurrent to the iron oxide and is produced with the aid of the plasma generator from a recycle gas such as the extra gas produced from the solid reducing agent in addition to the reaction gas from the shaft. . The recycle gas is first washed almost from CO ₂ and H ₂ O and then the cleaned gas is divided into two parts, one of which is sent to the plasma generator. The plasma generator is composed of a gas generating shaft which is almost filled with a solid reducing agent such as coke or the like. The plasma burner is mounted at the bottom of the gas generating shaft and water and / or oxygen gas is injected into the hot gas stream from the plasma burner to cause a reaction with a reducing agent, thereby forming a mixture mainly consisting of CO and H ₂ . The temperature of the produced gas is kept within a range in which ash contained in the solid reducing agent can be formed into slag. The hot CO-H ₂ mixture exiting the gas generator is mixed with at least another stream of cleaned recycle gas at a rate such that the temperature of the final gas mixture may be suitable for the reduction process.

One feature of the present invention is to control the temperature of the gas produced in the gas generator in the range of 1300 to 1500 ° C. It is also preferred to mix the final gas mixture with the second stream before feeding it to the bottom of the shaft to bring its temperature within the range of 700 to 1000 ° C. Another feature of the present invention is to recycle the recycle gas in a gas scrubber until the content of CO ₂ is preferably 2% or less.

The implementation method of the present invention will be described with reference to the following drawings. The reduction of the iron oxide mass is carried out in the shaft 1. The iron oxide mass is fed into the shaft 1 through a sluice valve 3 and is treated by a countercurrent flow of hot reducing gas consisting primarily of carbon monoxide and hydrogen gas supplied from the bottom 4 of the shaft 1. . The sponge iron product is discharged through the outlet 5 at the lower part 4 of the shaft 1, and the reducing gas reacted with about 30 to 50% is discharged through the outlet 6 at the upper part of the shaft 1. do.

In this way, the gas discharged from the reactor 1 contained not only 50 to 70% of unreacted CO and H ₂ but also reaction products CO ₂ and H ₂ O. Such gases can still be reused because of their relatively high CO and H ₂ content, but the content of CO ₂ and H ₂ O must be reduced to 5% or less to be reused as reducing gas. This can be accomplished by sending gas to scrubber 7. (CO ₂ / H ₂ O wash). When the gas passes through this scrubber, the reaction products CO ₂ and H ₂ O are removed, and the amount of gas in the actual cleaning is balanced, thereby avoiding ignition of the gas. In addition, the scrubber 7 may contain mono ethanolamine as the active substance, and the CO ₂ content in the gas may be appropriately reduced to 2% or less when passing through the scrubber.

After the gas has passed through the scrubber 7, it enters the compressor 8 and its pressure is increased to the extent necessary to carry out the process and divided into at least two flow sections 9 and 10. The flow 9 is at room temperature and enters the gas generator 11 where extra gas is generated from a solid reducing agent, preferably coke and water / or oxygen gas. The gas flow 9 is used as the plasma gas in the gas generator 11, and the amount of energy required in the gas generating process is supplied by the plasma burner 12. The gas generator 11 is almost filled with a solid reducing agent, preferably coke. The oxidant, preferably water and / or oxygen gas, is fed to the gas generator 11 via a jet 13 and then permeated into a hot gas stream exiting the plasma burner 12. In addition, the reducing agent may be added in the form of powder through the injector 13a from the outside.

Such supplemental reducing agent is preferably coal powder having a particle size of 20 mesh or less, preferably 100 mesh or less. The hot gas stream from the plasma burner therefore acts on the reduction to form CO and H ₂ . When supplying energy into the gas generator 11, the amount of ash so that the ash present in the coal dust melts the slag 14, which can be removed through the discharge mechanism 16 in liquid or solid form at the bottom of the gas generator 11. Adjust On the other hand, since the presence of ash, the temperature range is preferably selected to 1300 ~ 1500 ℃. The reducing gas generated in the apparatus may contain sulfur contained in coal except that it contains CO and H ₂ .

This intermediate gas mixture is therefore passed through a sulfur filter 15 (eg dolomite filter) which reduces the sulfur content to a level suitable for the production of sponge iron, preferably below 75 ppm.

As another specific example of the present invention, the sulfur filter 15 can be installed in the gas generator itself by preparing a coke bed containing a suitable material for filtration purposes. Since the gas coming out of the sulfur filter 15 is substantially higher than the temperature required for the production of sponge iron, the temperature is mixed with a suitable proportion of the gas cooled and cleaned in the flow section 10, namely, It is adjusted to 750-1000 degreeC, Preferably it is 825 degreeC. On the other hand, a separate mixing mechanism may be used to mix the gas coming from the gas generator and the flow section 10, and the upper portion of the gas generator 11 so that some or all of the flow section 10 can be used as the mixing chamber. Can be introduced.

Substantial technical advantages are obtained by using the method according to the invention. In this regard, gas evolution can occur at temperatures at which ash is easy to handle and can form slag that can be taken out without causing an interruption of the process. The hydrogen content in the reducing gas can be adjusted to an amount suitable for the reduction process by continuing to inject water and / or oxygen into the gas generator.

In addition, the combination of scrubbing and gas evolution at increased temperatures offers a high possibility of balancing the amount of gas in the system and controlling the reduction temperature. At the same time, the energy efficiency is satisfactory because the energy supplied by the plasma generator is used almost completely in the process. (Ie, temperature control is performed by adding a cooled recycle reducing gas rather than removing heat from the system).

The consumption value per tonne of sponge iron produced in the experiments of the test scale is as follows: electrical energy: 820 kwh, coal powder: 172 kg; the process according to the invention is also very simple to control. A simpler and more efficient control of the whole process can be achieved by the generation of plasma gas by premixing the coal dust and the added water in the correct proportion, preferably in the stoichiometric ratio. This preliminary mixing of coal dust and water makes it easy to inject the mixture in the form of a coal-water emulsion. If there is a difficulty in combining ash from the solid sulfur source in the slag layer, additives such as alkali metals and chokes may be used that affect the properties of the slag (ie melting point, sulfur absorption, etc.).

Such additives are preferably mixed with a solid reducing agent. On the other hand, an appropriate gel former may be added to stabilize the coal-water mixture, and oxygen may be supplied to the gas generator 11 in the form of oxygen gas instead of water.

Claims (1)

In order to produce iron sponge by continuously reducing the iron oxide, the step of removing the reaction gas at the top of the shaft (1), the step of removing almost all CO ₂ and H ₂ O from the reaction gas, and the reaction gas Is divided into two flow sections (9, 10), a gas generating shaft filled with coke as a solid reducing agent, a plasma burner (12) installed under the gas generating shaft and means (13) and an auxiliary means for injecting an oxidant The gas generator 11 composed of means 13a for injecting a reducing agent causes one of the flow portions 9 and 10 to flow therein, thereby heating the reaction gas of the flow portion with a plasma burner and at the same time water and / or an oxidant. and generating an intermediate gas mixture consisting mainly of CO and H ₂ by spraying the coal minutes to the heated reaction gas as an oxygen gas and an auxiliary reducing agents, the solid reducing agent Maintaining the intermediate gas mixture at a temperature of about 1300 to 1500 ° C. such that the ash contained therein forms slag, passing the intermediate gas mixture through a sulfur filter 15, and the temperature of the final reducing gas Mixing the reactant gas and the intermediate gas mixture of the remaining one of the two flow parts 9 and 10 so as to be suitable for reducing the iron oxide in the furnace 1, and injecting the reducing gas into the lower part of the furnace 1. By the flow of the reducing gas injected upward in the furnace 1 to reduce the iron oxide (2) in the furnace and the step of removing the reduced iron in the furnace (1) characterized in that it is continuously repeated Method of producing sponge iron.

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