GB2150592A

GB2150592A - Method and plant for reducing oxidic material

Info

Publication number: GB2150592A
Application number: GB08427968A
Authority: GB
Inventors: Sven Santen; Bjorn Hammarskog; Goran Mathisson
Original assignee: SKF Steel Engineering AB
Current assignee: SKF Steel Engineering AB
Priority date: 1983-12-02
Filing date: 1984-11-05
Publication date: 1985-07-03
Also published as: BE901158A; IT8423370A1; FR2556002B1; NO844799L; GB8427968D0; DE3441362A1; AU3525184A; DE3441362C2; IT8423370A0; FR2556002A1; BR8406065A; IT1177077B

Abstract

The invention relates to a method and a plant for reducing oxide-containing material while simultaneously generating a gas suitable as fuel gas. In this regard, there is produced from carbonaceous and/or hydrocarbon material a reduction gas (16) containing mainly carbon monoxide and hydrogen gas, obtained by partial combustion (at 12) and further treatment with carbon in a separate gas generating shaft (14). The temperature of said thus prepared reduction gas is then regulated (20) and said gas introduced into a reduction shaft (1) containing the oxidic material optionally subsequent to desulphurizing (17) said gas. Thereafter the partially spent reduction gas withdrawn from said reduction shaft is freed from water and solids (5), whereafter a part-flow of said spent gas may be used as fuel gas (6), while optionally a further part-flow is returned to the process (via 7 and 23). <IMAGE>

Description

SPECIFICATION A method and plant for reducing oxidic material while simultaneously generating a gas suitable as fuel gas The present invention relates to a method and a plant for reducing oxidic material while generating at the same time a gas suitable as fuel gas.

One object of the present invention is to provide an optimal reduction process, which means optimal regarding process-technology as well as energy consumption with a particularly readily controlled gas-generating system for generating reduction gas of suitable analysis, pressure and temperature.

A further object of the invention is to provide a process which at the same time makes it possible to withdraw desired quantities of fuel gas from the system.

Another object of the invention is to provide a process of such flexibility that a suitable part of the spent reduction gas withdrawn from the shaft furnace may be re-used in the process.

The invention is directed to a method and a plant for reducing oxidic material while generating at the same time a gas suitable as fuel gas and comprises the steps of a) producing from a carbonaceous and/or hydrocarbon containing starting material a reduction gas mainly containing carbon monoxide, hydrogen, carbon dioxide and water, wherein said starting material, together with an oxidizing agent and optionally also a slagforming flux, is introduced into a gasification chamber while simultaneously generating thermal energy through partial combustion; b) reforming the thus produced gas, leaving said gasification chamber at a temperature above the ash melting point, in a subsequent shaft filled with solid carbonaceous lump material to a reduction gas containing mainly carbon monoxide and hydrogen;; c) bringing the thus produced reduction gas to a temperature suitable for the subsequent reduction process, introducing said reduction gas into a shaft furnace containing the oxidic material to be chemically reduced, said reduction gas being caused to flow in countercurrent to said oxidic material in said shaft furnace; and d) removing from the partially spent reduction gas, withdrawn from said shaft furnace, substantially all water and dust-like solids and utilizing the main part of said treated spent gas as fuel gas.

According to an other embodiment of the invention said reforming step is carried out in such a way that said reduction gas is containing mainly carbon monoxide and hydrogen with an amount of carbon dioxide and water vapour of less than 10 per cent.

According to a further embodiment of the present invention oxygen gas and maximum 20 per cent H2O is used as oxidizing agent in said gas generating process and said oxidizing agent mixed with at least part of said carbonaceous and/or hydrocarbon containing material is introduced into the gasification chamber through a burner. Said oxidizing agent may be preheated before being fed through said burner.

As shaft filling material coke may preferably be used eventually mixed with sulphur acceptors. Alternatively pulverulent flux together with optional sulphur acceptors may be injected into the system in the immediate vicinity of said burner.

According to a further embodiment of the present invention the reduction gas generated in said gasification chamber is preferably desulphurized in a subsequent sulphur filter prior to cooling said reduction gas. Normally said generated reduction gas leaves the shaft at a temperature of between 1000-1 500 C, whereafter the temperature of said generated reduction gas is regulated to between 700-1 000'C, preferably 825'C, prior to reducing said reduction gas into said reduction shaft furnace.

According to a further embodiment of the present invention said hot reduction gas exiting from the gas generator is a) mixed optionally after being desulphurized with a certain quantity of partially spent reduction gas withdrawn from the reduction shaft and/or b) fed through a cooling means in order to achieve said desired final gas temperature between 700-1000"C, preferably 825'C, prior to introducing said reduction gas into said reduction shaft furnace.

The present invention also refers to a plant for reducing oxidic material while simultaneously generating a gas suitable as fuel gas, which plant comprises a reduction gas generating means including at least one gasification chamber with at least one burner, a shaft filled with solid carbonaceous material in lump form, a shaft furnace connected to said gas generating means, optionally via a sulphur filter, said shaft furnace containing said oxidic material to be reduced, a first gas outlet means arranged in the upper part of said shaft furnace, a separator means located adjacent said first gas outlet means and arranged to remove from the exiting gas-flow water and dust-like solids contained therein, and a subsequent second gas outlet means for discharging gas suitable as fuel gas and a main supply line for recycling at least a part-flow of said exiting gas flow for regulating the temperature of said reduction gas produced in said gas generating means.

Further characteristics of the invention are set forth in the accompanying claims.

For a better understanding of the invention, reference is made to the following description with the single Figure of the accompanying drawing which illustrates schematically a mode of carrying out the invention.

In the drawing 1 identifies a reduction shaft furnace intended for reducing oxidic lump material. Said shaft furnace 1 is provided with means 2 for introducing the oxidic lump material to be reduced into said shaft furnace.

Arranged at the bottom of said shaft furnace 1 is an inlet pipe means 3 for supplying hot reduction gas to the shaft furnace 1, said gas comprising substantially carbon monoxide and hydrogen and said gas being caused to pass through said shaft furnace 1 in counter-flow to the lump material and is intended to be removed thereafter through a first gas outlet 4 in the upper region of the shaft furnace 1.

Said outlet line 4 is connected to a separator means 5, a so called scrubber, in which dustlike solids and water are removed from the spent gas withdrawn from said shaft furnace 1. Water and dust-like solids are thus removed from said spent gas or top gas in said separator 5 and during this operation, the gas is simultaneously cooled and any desired quantity of the spent gas may thereafter be withdrawn from the system as fuel gas by an outlet means 6. A part of this spent gas is passed back in the process for re-use through a line or conduit 7, as described in more detail below. Said line is provided with at least one compressor 8.

At least one burner means 11 is arranged in the lower part of the gasification chamber 1 3.

1 2 identifies a lance for feeding slag-forming flux to said gasification chamber 1 3 together with sulphur acceptors if necessary. 1 5 identifies a slag outlet means arranged in said gasification chamber 1 3. Said gasification chamber 1 3 is connected to the bottom of a coke-filled shaft 1 4. Said shaft 1 4 is at its upper end provided with a gas outlet means, which by a conduit 16 is connected to a sulphur filter 1 7. The conduit 16 is provided with an outlet means 22 for withdrawal of gas intended for use as fuel gas.A further outlet means 22a for the same purpose may be provided in a conduit 18, immediately after said filter 17; said conduit 1 8 connects said filter 1 7 with said inlet means 3. In order to achieve a cooling of said generated reduction gas at least a part of said reduction gas can be passed through a cooling device 20 via a by-pass connection 19, 21 to said conduit 18.

The gas line 7 includes a branch line 23 which is connected to the conduit 1 8 immediately before said gas inlet means 3. Said conduit 1 8 is, immediately before said gas inlet means 3, also connected to a supply conduit 24 for H2S and a further supply conduit 25 for carbon carrier, such as methane, methanol and/or propanol. In this manner it is possible to further control the carbon content of the generated reduction gas before it is fed into the shaft 1. The supply of H2S already in a minor quantity reduces the risk for the formation of soot in the system.

A supply line 9 for transporting oxygen gas and a supply line 10 for transporting the carbonaceous and/or hydrocarbon containing material is connected directly to said burner 11 for feeding said materials through said burner and into said gasification chamber 1 3.

The oxidizing agent may optionally be heated prior to passing said burner 11.

The plant illustrated in the drawing has the following principal mode of operation: The reduction gas intended for chemically reducing the oxidic material in said shaft furnace 1 and introduced into the bottom of said shaft 1 via the gas inlet means 3 is principally prepared in the gas generator 1 4 by introducing a carbonaceous and/or hydrocarbon-containing starting material, together with an oxidizing agent and optionally a flux, into the gasification chamber 1 3 connected to the bottom part of the coke-filled shaft 1 4.

The reduction gas thus produced is then brought in principle to a temperature suitable for the subsequent reduction of the oxidic material in the shaft furnace 1, and is caused to flow through the shaft furnace 1 in counterflow with the material to be reduced therein.

The spent gas withdrawn from the shaft 1, which is partially spent with regard to its chemical reducing abilities and which, in the reduction of said oxidic material becomes laden with oxidizing constituents such as carbon dioxide and water, together with dust-like solids, is, after its removal from the reduction shaft 1 via the gas outlet means 4 arranged in the upper region of said shaft furnace 1, fed through a scrubber 5 arranged to remove water and dust-like solids present in said top or spent gas. By this treatment in the scrubber 5, said spent gas is also cooled and may then partly be removed from the system via the gas-outlet line 6, and used as fuel gas. Alternatively a controllable part-flow of said gas flow may be returned to the process over the lines 7 and 23.

The reduction gas generation may be effected in many alternative ways. For example, pulverulent and/or liquid carbonaceous and/ or hydrocarbon-containing starting material, together with an oxidizing agent, comprising 20 per cent H2O, may be injected through said burner 11 into the gasification chamber 1 3 connected to the lower part of the cokefilled shaft 14. The carbonaceous and/or hydrocarbon-containing starting material may also be in lump form, in which case it is introduced via the upper part of the shaft 14.

A suitable carbonaceous material in this respect is coke.

The reduction gas generated in said shaft 14 can also be freed from sulphur by incorporating a suitable sulphur acceptor in the shaft filling or injected into the gasification chamber, or by passing the gas produced in said shaft 14 to a sulphur-separating filter 17, via the outlet line 1 6. Alternatively, any remaining sulphuric compounds present may be absorbed by the reduced metal oxide, in the lower part of the reduction shaft 1.

Normally, the generated reduction gas leaving the shaft 14, is maintained at a temperature within a range of 1000-1 500 C. It is not possible, however, to use a reduction gas of such high temperature for the reduction process in the reduction shaft immediately, and consequently, the temperature of the reduction gas must be lowered before introducing said gs into the shaft furnace 1. This can be effected in many ways within the scope of the invention.

For example, the generated reduction gas taken from the coke-filled shaft 1 4 through the line 1 6 may after passing the filter 1 7 be admixed with a suitable part-flow of recycled spent gas from the shaft furnace 1 through line 23, such that the temperature of the gasmixture lies between about 700-1000"C.

The temperature of the generated reduction gas may also be regulated by passing a partflow of the generated gas through said cooling means arrangement 20.

The gas-generating process proposed in accordance with the present invention affords important advantages from the aspect of process technology. The gas-generating process can be effected at temperatures at which the ash forms a readily manageable slag, which can be tapped-off without creating problematic blockages in the process through tap-holes 1 5 located in the bottom of the gasification chamber and/or the coke-filled shaft 1 4.

Claims

1. A method for reducing oxidic material while simultaneously generating a gas suitable as fuel gas, comprising the steps of a) producing from a carbonaceous and/or hydrocarbon containing starting material a reduction gas mainly containing carbon monoxide, hydrogen, carbon dioxide and water, wherein said starting material, together with an oxidizing agent and optionally also a slagforming flux, is introduced into a gasification chamber while simultaneously generating thermal energy through partial combustion; b) reforming the thus produced gas, leaving said gasification chamber at a temperature above the ash melting point, in a subsequent shaft filled with solid carbonaceous lump material to a reduction gas containing mainly carbon monoxide and hydrogen;; c) bringing the thus produced reduction gas to a temperature suitable for the subsequent reduction process, introducing said reduction gas into a shaft furnace containing the oxidic material to be chemically reduced, said reduction gas being caused to flow in countercurrent to said oxidic material in said shaft furnace; and d) rernoving from the partially spent reduction gas, withdrawn from said shaft furnace, substantially all water and dust-like solids and utilizing the main part of said treated spent gas as fuel gas.

2. A method according to claim 1, wherein a part of said reduction gas generated in said coke-filled shaft is removed from the process and used as fuel gas.

3. A method according to claim 1 or claim 2, wherein said reforming step is carried out in such a way that said reduction gas contains mainly carbon monoxide and hydrogen with an amount of carbon dioxide and water vapour of less than 10 per cent.

4. A method according to any one of claims 1 to 3, wherein oxygen gas and maximum 20 per cent H20 is used as oxidizing agent in said gas generating process, and said oxidizing agent mixed with at least part of said carbonaceous and/or hydrocarbon-containing material, is introduced into the gasification chamber through a burner.

5. A method according to claim 4, wherein said oxidizing agent is preheated before being fed through said burner.

6. A method according to any one of claims 1 to 5, wherein said carbonaceous and/or hydrocarbon-containing starting material used to generate said reduction gas is present in pulverulent form and/or liquid form and/or in lump form.

7. A method according to any one of claims 1 to 6, wherein said gasification chamber is connected to the lower part of a shaft filled with solid, carbonaceous lump material.

8. A method according to any one of claims 1 to 7, wherein coke is used as the carbonaceous filling of said shaft.

9. A method according to any one of claims 4 to 8, wherein pulverulent flux, together with optional sulphur acceptors are injected into the system in the immediate vicinity of said burner.

10. A method according to any one of claims 1 to 9, wherein a mixture of carbonaceous lump material and a suitable sulphur acceptor is used as said shaft filling.

11. A method according to any one of claims 1 to 10, wherein the reduction gas generated in said gasification chamber is desulphurized prior to cooling said reduction gas.

1 2. A method according to any one of claims 1 to 11, wherein said generated reduction gas leaving the shaft has a temperature of between 1000-1500"C.

1 3. A method according to any one of claims 1 to 12, wherein the temperature of said generated reduction gas leaving said shaft is regulated to between 700-1000"C, preferably 825"C, prior to introducing said reduction gas into said reduction shaft furnace.

14. A method according to claim 12, wherein said hot generated reduction gas leaving said shaft is a) mixed, optionally after being desulphurized, with a quantity of partially spent reduction gas withdrawn from the reduction shaft and/or b) fed through a cooling means in order to achieve said desired final gas temperature between 700-1000"C. preferably 825"C, prior to introducing said reduction gas into said reduction shaft furnace.

1 5. A method according to claim 14, wherein the recycled part-flow of said partially spent reduction gas from said reduction shaft is brought to the requisite process pressure, for example by means of at least one compressor.

16. A plant for reducing oxidic material while simultaneously generating a gas suitable as fuel for carrying out the method according to claim 1, comprising a reduction gas generating means including at least one gasification chamber with at least one burner, a shaft, a shaft furnace connected to said gas generating means, optionally via a sulphur-filter; said shaft furnace containing said oxidic material to be reduced; a first gas outlet means arranged in the upper part of the said shaft furnace; a separator means located adjacent said gas outlet means and arranged to remove from the exiting gas flow water and dust-like solids contained therein; and a subsequent gas outlet means for discharging gas suitable as fuel gas and a main suppiy line for recycling at least a part-flow of said exiting gas flow for regulating the temperature of said reduction gas produced in said gas generating means.

1 7. A plant according to claim 16, wherein said main supply line is provided with at least one compressor means.

1 8. A plant according to claim 1 6 or claim 17, wherein said burner is connected to an oxidizing agent supply means for direct passage of the optionally pre-heated oxidizing agent through said burner and to a reaction zone.

1 9. A plant according to any one of claims 1 6 to 18, wherein said gas generating means is provided with at least one bottom outlet means.

20. A plant according to any one of claims 16 to 19, wherein said gas generating shaft accomodates a filling of carbonaceous lump material, optionally containing sulphur acceptors.

21. A plant according to any one of claims 1 6 to 20, wherein a reduction-gas line between said sulphur generator and a gas inlet of said reduction shaft by a line is connectable to a temperature-regulating partflow of spent gas.

22. A plant according to claim 21, wherein said reduction gas line between said sulphur separator and said gas inlet of said reduction shaft is connected to a carbon carrier supply line means and further supply line means for the addition of H2S.

23. A plant according to claim 21 or claim 22, wherein said reduction gas line is connectable to said gas inlet via a cooler by lines.

24. A method for reducing oxidic material according to claim 1 and substantially as herein described with reference to the drawings.

25. A plant for reducing oxidic material according to claim 1 6 and substantially as herein described with reference to the drawings.