SYNGAS GENERATOR FOR BLAST FURNACE

Abstract

A method for producing a syngas stream for use in a blast furnace, including providing a hot air stream to an ion transport membrane, thereby producing a hot nitrogen rich stream and a hot oxygen rich stream, providing a methane stream to the ion transport membrane, wherein the methane reacts with the hot oxygen rich stream thereby producing a syngas containing stream, introducing the syngas containing stream into a CO2 removal unit, thereby producing a carbon dioxide rich stream, and a hydrogen rich stream, and introducing the hydrogen rich stream into a blast furnace, thereby replacing at least a portion of the natural gas fuel required therein.

Description

BACKGROUND

The blast furnace is a tall shaft-type furnace with a vertical stack superimposed over a crucible-like hearth. Iron-bearing materials (iron ore, sinter, pellets, mill scale, steelmaking slag, scrap, etc.), coke and flux (limestone and dolomite) are charged into the top of the shaft. A blast of heated air and also, in most instances, a gaseous, liquid or powdered fuel are introduced through openings at the bottom of the shaft just above the hearth crucible. The heated air burns the injected fuel and much of the coke charged in from the top to produce the heat required by the process and to provide reducing gas that removes oxygen from the ore. The reduced iron melts and runs down to the bottom of the hearth. The flux combines with the impurities in the ore to produce a slag which also melts and accumulates on top of the liquid iron in the hearth. The iron and slag are drained out of the furnace through tapholes.

The top pressure that is controlled by the top gas handling equipment can be as high as (40-50 psig) for very large furnaces, and the blast air has been enriched with oxygen as high as 40% total oxygen in the blast. Pressure at the inlet of the tuyeres depends on the controlled top pressure and the quality of the raw materials, but can be as high as 60 psig for a very large blast furnace. Oxygen enrichment reduces the amount of air needed per tonne of iron and therefore, the resulting quantities of BF Top Gas are reduced.

Ion transport membranes (ITMs) consist of ionic and mixed-conducting ceramic oxides that conduct oxygen ions at elevated temperatures of 1475-1650 F. Air is compressed, heated to 1650 F, and fed to ITM. Hot oxygen permeates through the membranes. The permeate pressure has to be kept low to provide oxygen partial pressure driving force across the membrane. Typically, 50% to 80% oxygen recovery seems possible.

SUMMARY

A method for producing a syngas stream for use in a blast furnace, including providing a hot air stream to an ion transport membrane, thereby producing a hot nitrogen rich stream and a hot oxygen rich stream, providing a methane stream to the ion transport membrane, wherein the methane reacts with the hot oxygen rich stream thereby producing a syngas containing stream, introducing the syngas containing stream into a CO2 removal unit, thereby producing a carbon dioxide rich stream, and a hydrogen rich stream, and introducing the hydrogen rich stream into a blast furnace, thereby replacing at least a portion of the fuel required therein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of one embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In typical operation, coal, natural gas and steam are added to the blast furnace along with hot blast air. CH4 burns in the tuyeres to make H2O and CO2 (CH4+2O2→CO2+2H2O) which then get reformed into H2 and CO (by reaction with hot coke, C+CO2→2CO, C+H2O→CO+H2) at high temperature (typically about 2000-2300° C.) found in the bottom of the blast furnace. Additional steam also reacts with carbon in the coke to produce CO and H2. Part of H2 and CO reacts with iron ore in the upper shaft of the furnace, establishing a chemical equilibrium. Excess H2 and CO are found in the top gas. Replacing H2 for natural gas and part of steam will reduce the carbon requirement of the blast furnace. It will reduce the carbon requirement of the blast furnace thereby reducing the amount of CO and CO2 in the top gas, further improving the thermal efficiency of blast furnace.

Ion Transport Membranes (ITM's) produce pure O2 from the hot air at about 750-1000C. ITM Reactor has steam reforming catalyst such as Ni deposited on the permeate side of the ITM membranes. If natural gas (CH4) and steam mixture is injected on the permeate side of ITM reactor, H2/CO rich syngas is produced. The syngas can be shifted to CO2 and H2. The shifted syngas is processed in a CO2 removal unit to produce pure H2 and CO2 rich tail gas.

As shown in FIG. 1, the ITM syngas reactor is integrated into a blast furnace design. The air pressure required for an ITM is typically less than 2 bara, and can be drawn from the first stage of the blast furnace air compressor. The air is heated with oxygen-depleted effluent from the ITM which has been combusted and expanded in a gas turbine for power recovery. There may be other ways to preheat the air such as x-exchange with part of hot blast air from the stove. The natural gas and steam mixture is injected into ITM reactor at the desired pressure of syngas, which may be in the range of 10-15 bar. The syngas from the ITM reactor is cooled and mixed with steam, sent to water gas shift reactor. The heat in the shifted gas can be used to generate steam. The shifted gas is further cooled and processed in a CO2 removal unit to produce H2 rich stream which is fed to the blast furnace. The H2 rich stream contains unconverted CO and CH4 The CO2 removal unit may be an amine wash unit, or any other system known to one skilled in the art.

A part of top gas can be compressed and mixed with syngas to the shift reactor. This will recycle H2 and CO present in the top gas, while capturing more CO2.

Turning to FIG. 1, a syngas generator for a blast furnace is provided. An air stream 101 is compressed in compressor 102, thus creating a compressed, air stream 103. The compressed, air stream 103 is divided into a blast furnace air stream 104 and an ITM air stream 105. Compressed air stream 103 may have a pressure of about 25-35 psia. Blast furnace air stream 104 may be further compressed in compressor 109. The blast furnace air stream 104 is introduced into blast furnace stove 105, wherein it is heated, thereby producing heated blast furnace air stream 106. Blast furnace stove 105 is heated by the combustion of at least a portion of blast furnace top gas stream 107. First combustion product stream 108 is then exhausted from the stove. Heated blast furnace air stream 106 may have a temperature of between 1800 and 2200 F.

ITM air stream 105, is introduced into a heat exchanger 112, wherein it exchanges heat with reduced pressure combustion stream 118, thereby producing cooled combustion stream 121 and heated ITM air stream 113.

Heated ITM air stream 113 is introduced to an ion transfer membrane reactor 114, Heated ITM air stream 122 may have a temperature of about 1400 to 1830 F. Methane and steam mixture stream 135 is introduced into the permeate side of the ITM reactor 114 at desired pressure of about 50-150 psia. The stream 135 may be preheated (not shown). The ITM reactor produces a syngas stream 115 and a N2 rich retentate stream 116. The retentate stream 116 is then introduced into combustion unit 117, thereby producing combustion stream 118. Stream 134 reacts with O2 permeating in ITM , generating syngas stream 115 containing H2, CO, and CO2.

The syngas stream 115 is introduced into water gas shift reactor 123 therein producing shifted syngas stream 124. Shifted permeate stream 124 is then introduced into steam generator 125 along with feed water stream 126, thereby producing steam stream 128, and cooled shifted permeate stream 127. Cooled shifted permeate stream 127 may be introduced into CO2 removal unit 129, thereby producing CO2 rich stream 130 and hydrogen stream 131. The hydrogen stream 131 may contain unconverted CO and CH4, and residual CO2. Hydrogen stream 131 may then be introduced into blast furnace 132, to be used as reductant to process iron ore, and coke 133. Coal is typically injected in the bottom part of the blast furnace, through the tuyeres. Hydrogen stream 131 may be preheated to a temperature of at least 900 C (1667 F) before being injected into blast furnace 132. Stream 131 may be heat exchanged(not shown) with other hot streams such as stream 116 or a supplemental heater (not shown) may be used to further heat syngas stream 131 if necessary.

Claims

1. A method for producing a hydrogen rich stream for use in a blast furnace, comprising;

a. providing a hot air stream to an ion transport membrane, thereby producing a hot nitrogen rich stream and a hot oxygen rich stream,

b. providing a methane and steam mixture stream to the ion transport membrane on the permeate side, wherein the methane reacts with the hot oxygen rich stream over a catalyst thereby producing a syngas stream,

c. introducing the syngas containing stream into a CO2 removal unit, thereby producing a carbon dioxide rich stream, and a hydrogen rich stream, and

d. introducing the hydrogen rich stream into a blast furnace, thereby replacing at least a portion of the coke and/or injected fuel required therein.

2. The method of claim 1, wherein said hot air stream has a temperature greater than 750C.

3. The method of claim 2, wherein said hot air stream has a temperature between 750C and 1000 C.

4. The method of claim 1, further comprising introducing the syngas containing stream into a heat recovery steam generator prior to introduction into the CO2 removal unit, thereby producing steam.

5. The method of claim 1, further comprising introducing the syngas containing stream into a water-gas shift reaction prior to introduction into the CO2 removal unit.

6. The method of claim 1, wherein the hydrogen rich stream displaces a significant portion of the fuel required in the blast furnace.

7. The method of claim 1, wherein the hot nitrogen rich stream provides at least a portion of the heat required to produce the hot air stream.

8. The method of claim 1, wherein at least a portion of the hot air stream is provided by a blast furnace air compressor.

9. The method of claim 1, wherein a part of the top gas stream is compressed and mixed with ITM syngas upstream of shift reactor, and thus part of the hydrogen and carbon monoxide present in the top gas stream is recovered and recycled to the blast furnace.