U.S. patent application number 12/275041 was filed with the patent office on 2009-05-28 for process for production of elemental iron.
Invention is credited to Cornelis Jacobus SMIT, Hendrik Jan VAN DER PLOEG, Gijsbert Jan VAN HEERINGEN.
Application Number | 20090133535 12/275041 |
Document ID | / |
Family ID | 39271080 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090133535 |
Kind Code |
A1 |
VAN HEERINGEN; Gijsbert Jan ;
et al. |
May 28, 2009 |
PROCESS FOR PRODUCTION OF ELEMENTAL IRON
Abstract
The invention is directed to a process to prepare elemental iron
by contacting an iron ore feed with a reducing gas to obtain iron
and an off-gas. The reducing gas is prepared by performing the
following steps (a) partially oxidizing a mixture comprising a
sulphur containing solid carbonaceous fuel and gaseous CO.sub.2 as
carrier medium with oxygen, by supplying an oxygen containing gas
and the solid carbonaceous fuel to a burner, thereby obtaining a
gas comprising H.sub.2, CO, CO.sub.2 and H.sub.2S; (b) removing
CO.sub.2 and H.sub.2S from the gas obtained in step (a) to obtain
the reducing gas comprising H.sub.2 and CO and a first stream
comprising CO.sub.2 and H.sub.2S; (c) reducing the content of
H.sub.2S in the first stream comprising CO.sub.2 and H.sub.2S
obtained in step (b) in a liquid redox type process and (d)
recycling at least part of the CO.sub.2 obtained in step (c) to
step (a).
Inventors: |
VAN HEERINGEN; Gijsbert Jan;
(Amsterdam, NL) ; VAN DER PLOEG; Hendrik Jan;
(Amsterdam, NL) ; SMIT; Cornelis Jacobus;
(Amsterdam, NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
39271080 |
Appl. No.: |
12/275041 |
Filed: |
November 20, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60991162 |
Nov 29, 2007 |
|
|
|
Current U.S.
Class: |
75/392 |
Current CPC
Class: |
C10J 3/00 20130101; C21B
13/0073 20130101; Y02P 30/30 20151101; Y02P 30/00 20151101; C01B
2203/0465 20130101; C10K 1/34 20130101; Y02P 10/136 20151101; Y02P
10/212 20151101; C01B 2203/0475 20130101; Y02P 10/122 20151101;
C01B 2203/0495 20130101; C21B 2100/62 20170501; C10J 2300/0959
20130101; Y02P 10/134 20151101; Y02P 10/20 20151101; Y02P 10/126
20151101; C01B 2203/0485 20130101; C21C 2100/06 20130101; C01B
2203/0415 20130101; C01B 3/54 20130101; C10J 2300/0969 20130101;
C21B 2100/42 20170501; C01B 3/52 20130101; C01B 2203/86 20130101;
C21B 2100/282 20170501; Y02P 10/132 20151101 |
Class at
Publication: |
75/392 |
International
Class: |
C22B 9/05 20060101
C22B009/05 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2007 |
EP |
07121142.9 |
Claims
1. A process to prepare elemental iron by contacting an iron ore
feed with a reducing gas to obtain iron and an off-gas, wherein the
reducing gas is prepared by performing the following steps (a)
partially oxidizing a mixture comprising a sulphur containing solid
carbonaceous fuel and gaseous CO.sub.2 as carrier medium with
oxygen, by supplying an oxygen containing gas and the solid
carbonaceous fuel to a burner, thereby obtaining a gas comprising
H.sub.2, CO, CO.sub.2 and H.sub.2S; (b) removing CO.sub.2 and
H.sub.2S from the gas obtained in step (a) to obtain the reducing
gas comprising H.sub.2 and CO and a first stream comprising
CO.sub.2 and H.sub.2S; (c) reducing the content of H.sub.2S in the
first stream comprising CO.sub.2 and H.sub.2S obtained in step (b)
in a liquid redox type process and (d) recycling at least part of
the CO.sub.2 obtained in step (c) to step (a).
2. The process according to claim 1, wherein the off-gas comprises
CO.sub.2 and H.sub.2S, and wherein CO.sub.2 and H.sub.2S are
removed from the off-gas to obtain a recycle reducing gas
comprising CO and H.sub.2 and a second stream comprising CO.sub.2
and H.sub.2S, and wherein the recycle reducing gas is used as
reducing gas, and wherein the first and second stream comprising
CO.sub.2 and H.sub.2S are mixed and a mixture of the first and
second stream comprising CO.sub.2 and H.sub.2S is subjected to step
(c).
3. The process according to claim 1, wherein the weight ratio of
CO.sub.2 to the carbonaceous fuel in step (a) is less than 0.5 on a
dry basis.
4. The process according to claim 1, wherein the sulfur containing
solid carbonaceous fuel is chosen from the group consisting of
coal, petroleum coke, peat and solid biomass.
5. The process according to claim 1, wherein the gas obtained in
step (a) also comprises HCN and COS and wherein step (b) is
performed by (i) contacting the gas as obtained in step (a) with a
HCN/COS hydrolysis catalyst to convert HCN to NH.sub.3 and COS to
H.sub.2S, followed by removal of water and ammonia from the gas by
cooling and/or scrubbing; (ii) contacting the gas obtained in step
(i) with a solvent, which is selective for absorbing CO.sub.2 and
H.sub.2S.
6. The process according to claim 5, wherein the solvent comprises
one or more compounds selected from the group consisting of
N-methylpyrrolidone (NMP), dimethyl ether of polyethylene glycol
(DMPEG), methanol, an amine and mixtures of amines with
sulfolane.
7. The process according to claim 6, wherein the solvent comprises
di-isopropanol amine (DIPA)
8. The process according to claim 6 wherein the solvent comprises
an amine and sulfolane.
9. The process according to claim 1, wherein step (c) is performed
by liquid redox type process by contacting the stream of CO.sub.2
and H.sub.2S obtained in step (b) with an aqueous reactant solution
comprising an iron (III) chelate of an organic acid or complex
reactant system to produce elemental sulphur which is recovered as
a by-product of the process either prior to or subsequent to
regeneration of the reactant.
10. The process according to claim 1, wherein a part of the
CO.sub.2 as obtained in step (c) is used for enhanced oil recovery,
CO.sub.2 sequestration or coal bed methane extraction.
11. The process according to claim 1, wherein a part of the
CO.sub.2 as obtained in step (c) is injected into a subterranean
zone to obtain a desired pressure in the subterranean zone to
enhance the recovery of a hydrocarbon containing stream as produced
from the subterranean zone.
12. The process according to claim 1, wherein part of the reducing
gas obtained in step (b) is used as a fuel in a gas turbine to
generate power.
Description
[0001] This patent application claims the benefit of European
patent application No. 07121142.9, filed Nov. 20, 2007 and U.S.
Provisional Application 60/991,162, filed Nov. 29, 2007, both of
which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention is directed to a process to prepare elemental
iron by contacting an iron ore feed with a reducing gas comprising
synthesis gas, wherein the reducing gas is prepared by a partial
oxidation process.
BACKGROUND OF THE INVENTION
[0003] Direct reduction of iron (DRI) generates metallic iron in a
solid form by removing oxygen from the iron ore by using a
reduction gas that can be provided from the synthesis gas obtained
by gasification of carbonaceous feedstock. Industrially applied DRI
processes include MIDREX, HyL and FINMET, as described in
"Development of Reduction Process for the Steel Production" by M.
Gojic and S. Kozuh, Kem. Ind. 55 (1) 1-10 (2006).
[0004] EP-A-0916739 describes a process wherein the reducing gas
for the DRI process is obtained by gasification of a coal slurry.
The reducing gas fed to the DRI includes a recycle gas stream that
has exited the DRI, and wherein acid gases have been removed from
the recycle gas stream.
[0005] U.S. Pat. No. 5,871,560 describes a process wherein
synthesis gas is mixed with an off-gas produced in a DRI process to
be used as a reduction gas and wherein H.sub.2S is fed to the
reducing gas.
[0006] U.S. Pat. No. 2,740,706, as filed in 1951, describes a
process for reducing metal oxides by contacting with a reducing
gas. In its examples the reducing gas is prepared by partial
oxidation of natural gas in admixture with carbon dioxide to obtain
a reducing gas having two to three times as much volume of carbon
monoxide for each volume of hydrogen. The reason, according to this
publication, to add carbon dioxide to the natural gas is to achieve
such high contents of carbon monoxide. Coal is mentioned as a
possible feedstock instead of natural gas. In this process sulphur
is removed from the reducing gas by contacting the gas with sponge
iron.
[0007] The so-called entrained-flow gasification process for coal
as described in "Gasification" by C. Higman and M. van der Burgt,
2003, Elsevier Science, Chapter 5.3, pages 109-128 was developed
after 1970 (see page 5 of this reference).
[0008] It would be an advancement in the art to provide a process
that has a higher efficiency than the above-described
processes.
SUMMARY OF THE INVENTION
[0009] The above is achieved by the following process. Process to
prepare elemental iron by contacting an iron ore feed with a
reducing gas to obtain iron and an off-gas, wherein the reducing
gas is prepared by performing the following steps
(a) partially oxidizing a mixture comprising a sulphur containing
solid carbonaceous fuel and gaseous CO.sub.2 as carrier medium with
oxygen, by supplying an oxygen containing gas and the solid
carbonaceous fuel to a burner, thereby obtaining a gas comprising
H.sub.2, CO, CO.sub.2 and H.sub.2S; (b) removing CO.sub.2 and
H.sub.2S from the gas obtained in step (a) to obtain the reducing
gas comprising H.sub.2 and CO and a first stream comprising
CO.sub.2 and H.sub.2S; (c) reducing the content of H.sub.2S in the
first stream comprising CO.sub.2 and H.sub.2S obtained in step (b)
in a liquid redox type process and (d) recycling at least part of
the CO.sub.2 obtained in step (c) to step (a).
[0010] Applicants found that by recycling part of the CO.sub.2 to
step (a) a more efficient process is obtained. A further advantage
of the present invention is that, for a given amount of
carbonaceous fuel to be partially oxidised in the gasification
reactor, a smaller reactor volume can be used, resulting in lower
equipment expenses, as compared to a situation wherein no CO.sub.2
is present in step (a). A further advantage is that the removal of
CO.sub.2 and H.sub.2S is performed in one step, namely step (b),
while in the process of U.S. Pat. No. 2,740,706 this removal takes
place in two steps. The separation of H.sub.2S from the first
stream comprising CO.sub.2 and H.sub.2S by means of a liquid redox
process is much more efficient than removing H.sub.2S from the
entire effluent of step (a) as in the process of U.S. Pat. No.
2,740,706.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 schematically shows a process scheme for a process
according to the present invention.
DETAILED DESCRIPTION
[0012] In the DRI process an iron ore feed is contacted with the
reducing gas comprising H.sub.2 and CO to obtain elemental iron and
an off-gas. Exemplary DRI processes are those mentioned
earlier.
[0013] In a typical DRI process the iron ore feed is usually in the
form of pellets or in the lump form or a combination of the two.
The iron ore is supplied to a heated furnace or to a set of
reactors through which it descends by gravity at superatmospheric
pressure, e.g., 1.5-12 bar. Iron ore feed is reduced in the said
furnace or set of reactors by the action of counterflowing reducing
gas that has high H.sub.2 and CO contents. Process specifics of the
DRI processes are described for example in "Kirk-Othmer
Encyclopedia of Chemical Technology", fourth edition, volume 14,
John Wiley & Sons, 1985, pages 855-872.
[0014] The reducing gas is used to remove oxygen from the iron
oxide comprised within the iron ore feed. The reducing process can
be illustrated by the following reaction, where H.sub.2O and
CO.sub.2 are obtained as by-products:
Fe.sub.2O.sub.3+H.sub.2.fwdarw.2Fe+3H.sub.2O
Fe.sub.2O.sub.3+CO.fwdarw.2Fe+CO.sub.2
Preferably the reducing gas has H.sub.2/CO ratio of at least 0.5.
It is also preferred that the reducing gas has a "gas quality" of
at least 10. The gas quality is defined as a ratio of reductants to
oxidants, as demonstrated by the following equation:
Gas quality=(mol % H.sub.2+mol % CO)/(mol % H.sub.2O+mol %
CO.sub.2)
[0015] Iron obtained from the DRI process is cooled and carbonized
by means of the counterflowing gasses in the lower portion of a
shaft furnace according to the following reaction:
3Fe+CO+H.sub.2.fwdarw.Fe.sub.3C+H.sub.2O
3Fe+CH.sub.4.fwdarw.Fe.sub.3C+2H.sub.2
By means of this process it is possible to manufacture for example
so-called cold DRI products, hot briquetted iron, or hot direct
reduction iron.
[0016] The off-gas obtained by the DRI process is the spent
reducing gas exiting the furnace. The off-gas can be cleaned by
scrubbing and CO.sub.2 removal and is preferably recycled to be
used as the reducing gas. Preferably the off-gas is treated before
the re-use as reducing gas to satisfy the requirement for reducing
gas as described above.
[0017] In step (a) of the process according to the invention a
mixture comprising a sulphur containing solid carbonaceous fuel and
CO.sub.2 with oxygen containing gas is partially oxidized, thereby
obtaining a gas comprising H.sub.2, CO, CO.sub.2 and H.sub.2S.
[0018] The partial oxidation may be performed by any process known.
Preferably the partial oxidation is performed by means of the
so-called entrained-flow gasification process as described in
"Gasification" by C. Higman and M. van der Burgt, 2003, Elsevier
Science, Chapter 5.3, pages 109-128. More preferably step (a) is
performed in an entrained-flow gasifier process wherein the
reaction between the mixture of carbonaceous fuel and CO.sub.2 with
oxygen containing gas takes place in a gasification reactor
provided with one or more burners. In such a process an oxygen
containing gas and a solid carbonaceous fuel are supplied to a
burner. CO.sub.2 is used as carrier medium to transport the fuel to
the burner. One or more burners can be provided in the gasification
reactor. The burner can be a single burner directed downward at the
top of a vertically elongated reactor. Preferably the gasification
reactor will have substantially horizontal firing burners in
diametrically opposing positions. The burner is preferably a
co-annular burner with a passage for an oxygen containing gas and a
passage for the fuel and the carrier gas. Partial oxidation of the
carbonaceous fuel occurs at a relatively high temperature in the
range of 1000.degree. C. to 2000.degree. C. and at a pressure in a
range of from about 1-70 bar. Preferably the pressure is between 10
and 70 bar, more preferably between 30 and 60 bar. The gas is
cooled with either direct quenching with water, direct quenching
with the off-gas, direct quenching with the part of the gas
obtained in either steps (a) or (b), by indirect heat exchange
against evaporating water or combination of such cooling steps.
Slag and other molten solids are suitably discharged from the
gasification reactor at the lower end of the said reactor.
[0019] The term solid carbonaceous fuel may be any carbonaceous
fuel in solid form. Examples of solid carbonaceous fuels are coal,
coke from coal, petroleum coke, soot, biomass and particulate
solids derived from oil shale, tar sands and pitch. Preferably the
solid carbonaceous fuel is chosen from the group of coal, petroleum
coke, peat and solid biomass. Coal is particularly preferred, and
may be of any type and sulphur content, including lignite,
sub-bituminous, bituminous and anthracite. Although in many DRI
processes natural gas is used as a fuel, coal is an interesting
choice for a fuel source because of its abundance. Coal is
preferably supplied to the burner in form of fine particulates. The
term fine particulates is intended to include at least pulverized
particulates having a particle size distribution so that at least
about 90% by weight of the material is less than 90 .mu.m and
moisture content is typically between 2 and 12% by weight, and
preferably less than about 8%, more preferably less than 5% by
weight. Preferably coal is supplied in admixture with CO.sub.2 as a
carrier medium.
[0020] Gaseous CO.sub.2 containing carrier medium contains
preferably at least 80%, more preferably at least 95% CO.sub.2.
CO.sub.2 can be separated from the reducing gas and from the
off-gas of the DRI process. It has been found that by using
CO.sub.2 as obtained in step (c) in step (a), as the carrier
medium, a more efficient process is obtained.
[0021] Preferably, the CO.sub.2 containing carrier gas supplied in
step (a) is supplied to the burner at a velocity of less than 20
m/s, preferably from 5 to 15 m/s, more preferably from 7 to 12 m/s.
Further it is preferred that the CO.sub.2 and the carbonaceous fuel
are supplied at a density of from 300 to 600 kg/m.sup.3, preferably
from 350 to 500 kg/m.sup.3, more preferably from 375 to 475
kg/m.sup.3.
[0022] In a preferred embodiment of the process according to the
present invention, the weight ratio of CO.sub.2 to the carbonaceous
fuel in step (a) is in the range from 0.12-0.49, preferably below
0.40, more preferably below 0.30, even more preferably below 0.20
and most preferably between 0.12-0.20 on a dry basis.
[0023] It has been found according to the present invention that
using the relatively low weight ratio of CO.sub.2 to the
carbonaceous fuel in step (a) less oxygen is consumed during
gasification.
[0024] In a preferred embodiment step a) comprises partially
oxidizing a mixture consisting of a sulphur containing solid
carbonaceous fuel and CO.sub.2 with oxygen containing gas.
[0025] The oxygen containing gas comprises substantially pure
O.sub.2 or air. Preferably it contains at least 90% by volume
oxygen, with nitrogen, carbon dioxide and argon being permissible
as impurities. Substantially pure oxygen is preferred, such as
prepared by an air separation unit (ASU). Steam may be present in
the oxygen containing gas as supplied to the burner to act as
moderator gas. The ratio between oxygen and steam is preferably
from 0 to 0.3 parts by volume of steam per part by volume of
oxygen. When the downstream DRI process requires a high CO to
H.sub.2 ratio it is advantageous to use CO.sub.2 instead of steam
as a moderator gas. This CO.sub.2 is preferably CO.sub.2 as
obtained in step (c). A mixture of the fuel and oxygen from the
oxygen containing stream is then reacted in a reaction zone in the
gasification reactor.
[0026] The gaseous stream obtained in step (a) comprises mainly
H.sub.2 and CO, which are the main components of the synthesis gas,
and can further comprise other components such as CO.sub.2,
H.sub.2S, HCN and COS. The gaseous stream obtained in step (a)
suitably comprises from 1 to 10 mol % CO.sub.2, preferably from 4.5
to 7.5 mol % CO.sub.2 on a dry basis when performing the process
according to the present invention.
[0027] The gaseous stream obtained in step (a) is preferably
subjected to a dry solids removal and wet scrubbing.
[0028] The dry solids removal unit may be of any type, including
the cyclone type. The dry solid material is discharged from the dry
solids removal unit to be further processed prior to disposal.
[0029] In order to remove the particulate matter, for example soot
particles, the gaseous stream obtained in step (a) is contacted
with a scrubbing liquid in a soot scrubber. The gaseous stream
exiting the gasifier is generally at elevated temperature and at
elevated pressure. To avoid additional cooling and/or
depressurising steps, the scrubbing step in the soot scrubber is
preferably performed at elevated temperature and/or at elevated
pressure. Preferably, the temperature at which the reducing gas is
contacted with scrubbing liquid is in the range of from 120 to
160.degree. C., more preferably from 130 to 150.degree. C.
Preferably, the pressure at which the gaseous stream obtained in
step (a) is contacted with scrubbing liquid is in the range of from
20 to 80 bara, more preferably from 20 to 60 bara.
[0030] The process further comprises step (b) of removing CO.sub.2
and H.sub.2S from the gas obtained in step (a) thereby obtaining
the reducing gas comprising H.sub.2 and CO and a first stream
comprising CO.sub.2 and H.sub.2S.
[0031] Removing CO.sub.2 and H.sub.2S is performed in a, hereafter
referred to, CO.sub.2 recovery system. The CO.sub.2 recovery system
is preferably a combined CO.sub.2/H.sub.2S removal system.
Preferably CO.sub.2/H.sub.2S removal is performed by absorption
using so-called physical and/or chemical solvent process. The
CO.sub.2 recovery is performed on the gaseous stream obtained in
step (a). The off-gas of the DRI contacting process is suitably
also subjected to the same or a different CO.sub.2 recovery system
to obtain a recycle reducing gas comprising CO and H.sub.2 and a
second stream comprising CO.sub.2 and possibly H.sub.2S. In case
the CO.sub.2 recovery system is the same, the second stream and the
first stream are the same and will be referred to as the first
stream.
[0032] It is preferred to remove at least 80 vol %, preferably at
least 90 vol %, more preferably at least 95 vol % and at most 99.5
vol %, of the CO.sub.2 present in the gaseous stream obtained in
step (a).
[0033] Absorption processes are characterized by washing the
synthesis gas with a liquid solvent, which selectively removes the
acid components (mainly CO.sub.2 and H.sub.2S) from the gas. The
laden solvent is regenerated, releasing the acid components and
recirculated to the absorber. The washing or absorption process
takes place in a column, which is usually fitted with for example
packing or trays. On an industrial scale there are chiefly two
categories of absorbent solvents, depending on the mechanism to
absorb the acidic components: chemical solvents and physical
solvents. Reference is made to the absorption process as described
in chapters 8.2.1 and 8.2.2 of "Gasification" (already referred
to), page 298-309, and Perry, Chemical Engineerings' Handbook,
Chapter 14, Gas Absorption.
[0034] Chemical solvents which have proved to be industrially
useful are primary, secondary and/or tertiary alkanolamines. The
most frequently used amines are derived from ethanolamine,
especially monoethanol amine (MEA), diethanolamine (DEA),
triethanolamine (TEA), diisopropanolamine (DIPA) and
methyldiethanolamine (MDEA).
[0035] Physical solvents which have proved to be industrially
suitable are cyclo-tetramethylenesulfone and its derivatives,
aliphatic acid amides, N-methylpyrrolidone, N-alkylated
pyrrolidones and the corresponding piperidones, methanol, ethanol
and mixtures of dialkylethers of polyethylene glycols.
[0036] A well-known commercial process uses an aqueous mixture of a
chemical solvent, especially DIPA and/or MDEA, and a physical
solvent, especially cyclotetramethylene-sulfone also referred to as
sulfolane. Such systems show good absorption capacity and good
selectivity against moderate investment costs and operational
costs. They perform very well at high pressures, especially between
20 and 90 bara.
[0037] Preferably the solvent comprises one or more compounds
selected from the group of N-methylpyrrolidone (NMP), dimethyl
ether of polyethylene glycol (DMPEG), methanol or an amine such as
di-isopropanol amine (DIPA) or mixtures of amines with sulfolane.
More preferably, the solvent comprises an amine and sulfolane.
[0038] Preferably step (b) comprises one or more further removal
systems that may be guard or scrubbing units, either as back-up or
support to the CO.sub.2/H.sub.2S removal system. These further
removal systems are aimed at removing HCN and COS or other
contaminants such as NH.sub.3, H.sub.2S, metals, carbonyls,
hydrides or other trace contaminants which may be comprised in the
gas obtained in step (a).
[0039] Preferably step (b) is performed by at least two steps
wherein in a first step the gas obtained in step (a) is contacted
with the HCN/COS hydrolysis catalyst to convert HCN to NH.sub.3 and
COS to H.sub.2S, followed by removal of water and ammonia from the
gas by cooling and/or scrubbing, and in a second step the gas
obtained in said first step is contacted with a suitable solvent,
which is selective for absorbing CO.sub.2 and H.sub.2S as described
above.
[0040] The process of contacting the gas obtained in step (a) with
the HCN/COS hydrolysis catalyst to convert HCN to NH.sub.3 and COS
to H.sub.2S takes place by catalytic hydrolysis in the hydrolysis
unit. Examples of a suitable hydrolysis step are disclosed in
WO-A-04105922. The hydrolysis zone can be a gas/solid contactor,
preferably a fixed bed reactor. Catalysts for the hydrolysis of HCN
and COS are known to those skilled in the art and include for
example TiO.sub.2-based catalysts or catalysts based on alumina
and/or chromium-oxide. Preferred catalysts are TiO.sub.2-based
catalysts.
[0041] The process further comprises step (c) of reducing the
content of H.sub.2S in the first stream comprising CO.sub.2 and
H.sub.2S obtained in step (b). Preferably the CO.sub.2 as obtained
in step (c) has a sulphur content lower than 10 ppmv, more
preferably between 5 and 10 ppmv. Step (c) is performed by means of
a liquid redox type process. More preferably step (c) is performed
by liquid redox type process by contacting the stream of CO.sub.2
and H.sub.2S obtained in step (b) with an aqueous reactant solution
comprising iron (III) chelate of an organic acid or complex
reactant system to produce elemental sulphur which is recovered as
a by-product of the present process either prior to or subsequent
to regeneration of the reactant, as described in for example "Gas
Purification" by A. Kohl and R. Nielsen, Gulf Publishing Company,
fifth edition, pages 670-840, and more specifically pages
803-840.
[0042] The reduction of H.sub.2S content in step (c) can also be
performed on a mixture of the first and second stream comprising
CO.sub.2 and H.sub.2S.
[0043] The process according to the invention further includes step
(d) wherein at least part of the CO.sub.2 obtained in step (c) is
recycled to step (a). The CO.sub.2 that is recycled to step (a) is
isolated from the first and optional second stream comprising
CO.sub.2 and H.sub.2S.
[0044] The reducing gas obtained in step (b) is directed to an
expander wherein the pressure of the reducing gas is reduced and
power is generated. The reducing gas is then heated in a gas heater
before entering the furnace of the DRI process where it is
contacted with iron ore feed to produce iron and the off-gas.
[0045] The off-gas of the DRI contacting process can be subjected
to the CO.sub.2 recovery as described above, thereby obtaining a
recycle reducing gas comprising CO and H.sub.2 and a second stream
comprising CO.sub.2 and H.sub.2S. The recycle reducing gas
comprising CO and H.sub.2 can be recycled to the furnace of the DRI
process. The CO.sub.2 from the first and second streams comprising
CO.sub.2 and H.sub.2S is preferably used in step (a) as a carrier
medium to carry the coal to the burner. Excess CO.sub.2 is
preferably stored in subsurface reservoirs or more preferably a
part of the CO.sub.2 as obtained in step (c) is used for one of the
processes comprising enhanced oil recovery, CO.sub.2 sequestration
or coal bed methane extraction. A part of the CO.sub.2 can be
injected into the subterranean zone to obtain a desired pressure in
said subterranean zone such to enhance the recovery of a
hydrocarbon containing stream as produced from said subterranean
zone. A part of the reducing gas obtained in step (c) is preferably
used as a fuel in a gas turbine to generate power.
[0046] In the process scheme of FIG. 1 a sulphur containing solid
carbonaceous fuel (1), preferably coal as fine particulates, is
mixed with the CO.sub.2 containing carrier gas (2) and fed to a
burner of a gasification reactor (4) where it is contacted with an
oxygen containing gas (3) to obtain the reducing gas comprising
H.sub.2 and CO (5) and slag (4a). The reducing gas (5) is treated
in a dry solids removal unit (6). The dry solid material is
discharged from the dry-solids removal unit (6) via line (6a).
Stream (7), free of solids, enters a CO.sub.2/H.sub.2S removal
system (8) where the removal of acid gases such as CO.sub.2,
H.sub.2S, and any other contaminants as HCN, COS takes place. After
exiting the CO.sub.2/H.sub.2S removal system (8), the cleaned
reducing gas (13) is expanded in an expander (14) whereby power
(15) is produced to be used in the current process or in a separate
process. The reducing gas exiting the expander via line (16) is
further heated in a heater (17) and is directed as a stream (18) to
a DRI furnace (19) where it is used as a reducing gas to be
contacted with the iron ore (20). The resulting iron is discharged
via stream (21). The off-gas (22) of the DRI furnace (19) is
directed to a CO.sub.2 removal system (23) wherein CO.sub.2 is
separated thereby obtaining a second stream comprising CO.sub.2 and
H.sub.2S (24) and a recycle reducing gas comprising CO and H.sub.2
(35). The recycle reducing gas comprising CO and H.sub.2 (35) is
recycled to the DRI furnace (19) via heater (17), by combining
stream (35) with stream (16). In case the sulphur content of the
second stream comprising CO.sub.2 and H.sub.2S (24) is more than 10
ppmv, the said stream (24) is directed as stream (25) to a liquid
redox process type unit (10) where it joins the first stream
comprising CO.sub.2 and H.sub.2S (9) exiting the CO.sub.2/H.sub.2S
removal system (8). Gas treatment can take place in separate
systems (8) and (23), or it can take place in a single system. The
sulphur obtained in the liquid redox process type unit (10) is
discharged via stream (11) while the CO.sub.2 exits the liquid
redox process type unit (10) as stream (29). A part (30) of stream
(29) can be directed to any other suitable process where CO.sub.2
is used via the stream (32). Another part of the stream (29) is
used as carrier gas (2) for carrying the carbonaceous feed (1) to
the gasifier (4). In case that sulphur content of the stream (24)
is less than 10 ppmv, the gas stream (24) may by-pass the liquid
redox process type unit (10) as stream (31). This stream may also
find use as the above stream (32) or as carrier gas (2).
* * * * *