U.S. patent application number 14/428116 was filed with the patent office on 2015-09-17 for method for heating process gases for direct reduction systems.
The applicant listed for this patent is VOESTALPINE STAHL GMBH. Invention is credited to Thomas Burgler, Peter Schwab, Hermann Wolfmeir.
Application Number | 20150259759 14/428116 |
Document ID | / |
Family ID | 50277660 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150259759 |
Kind Code |
A1 |
Wolfmeir; Hermann ; et
al. |
September 17, 2015 |
METHOD FOR HEATING PROCESS GASES FOR DIRECT REDUCTION SYSTEMS
Abstract
A method for reducing iron ore in the direct reduction method,
in which the iron ore to be reduced is conveyed through a reduction
unit such as a reduction shaft and is brought into contact with a
reduction gas; the reduction gas is brought into the reduction unit
and flows through the unit; after flowing through the unit, it is
taken from the unit; after exiting the unit, the gas is prepared
and possibly enriched with new gas components and is fed back
again; and the generated gas is heated before entry into the
reduction unit, characterized in that the heating of the reduction
gas prior to the entry into the unit is carried out in an
electrical fashion.
Inventors: |
Wolfmeir; Hermann; (Linz,
AT) ; Burgler; Thomas; (Steyregg, AT) ;
Schwab; Peter; (Linz, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOESTALPINE STAHL GMBH |
Linz |
|
AT |
|
|
Family ID: |
50277660 |
Appl. No.: |
14/428116 |
Filed: |
September 10, 2013 |
PCT Filed: |
September 10, 2013 |
PCT NO: |
PCT/EP2013/068743 |
371 Date: |
March 13, 2015 |
Current U.S.
Class: |
75/490 |
Current CPC
Class: |
C21B 13/0086 20130101;
Y02P 10/122 20151101; C21B 13/004 20130101; C22C 38/00 20130101;
Y02E 70/10 20130101; C21B 13/02 20130101; Y02P 10/126 20151101;
Y02P 10/134 20151101; C25B 1/04 20130101; C22C 37/00 20130101; Y02P
10/128 20151101; C01B 3/02 20130101; Y02E 60/36 20130101; C21B
13/0073 20130101; Y02E 60/366 20130101; Y02P 10/138 20151101; Y02P
10/136 20151101; Y02P 20/133 20151101; C21B 13/14 20130101 |
International
Class: |
C21B 13/00 20060101
C21B013/00; C21B 13/02 20060101 C21B013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2012 |
DE |
10 2012 108 631.1 |
Sep 28, 2012 |
DE |
10 2012 109 284.2 |
Apr 19, 2013 |
DE |
10 2013 104 002.0 |
Claims
1. A method for reducing iron ore in a direct reduction method,
comprising: conveying the iron ore to be reduced through a
reduction unit such as a reduction shaft and bringing the iron ore
into contact with a reduction gas; bringing the reduction gas into
the reduction unit to flow through the unit; after flowing through
the unit, taking the reduction gas from the unit; after exiting the
unit, preparing the gas and possibly enriching the gas with new gas
components and feeding the gas back again into the reduction unit;
and heating the generated gas mixture or the reduction gas products
from the generated gas mixture to 700 to 1100 before entry into the
reduction unit, wherein the heating is carried out in a
predominantly electrical fashion.
2. The method according to claim 1, comprising using electrical
power from regenerative energy sources for the electric
heating.
3. The method according to claim 1, further comprising, after the
gas has exited the unit, enriching the gas with natural gas, coke
oven gas, or a synthesis gas from biomass or coal.
4. The method according to claim 1, comprising enriching the gas
mixture with oxygen.
5. The method according to claim 1, comprising enriching the gas
taken from the reduction shaft with natural gas, coke oven gas, or
a synthesis gas from biomass or coal and then heating the enriched
gas.
6. The method according to claim 1, comprising enriching the gas
taken from the reduction shaft with natural gas, coke oven gas, or
a synthesis gas from biomass or coal and then transforming the
enriched gas in a reformer.
7. The method according to claim 1, comprising ensuring a
cost-optimized use of energy sources through a continuous
evaluation of gas prices and electricity prices.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method for heating process gases
for direct reduction systems.
BACKGROUND OF THE INVENTION
[0002] Steel production is currently carried out in a variety of
ways. Classic steel production is carried out by producing pig iron
in the hot furnace process, primarily out of iron oxide carriers.
In this method, approx. 450 to 600 kg of reducing agent, usually
coke, is consumed per metric ton of pig iron; this method, both in
the production of coke from coal and in the production of the pig
iron, releases very significant quantities of CO.sub.2. In
addition, so-called "direct reduction methods" are known (methods
according to the brands MIDREX, FINMET, ENERGIRON/HYL, etc.), in
which the sponge iron is produced primarily from iron oxide
carriers in the form of HDRI (hot direct reduced iron), CDRI (cold
direct reduced iron), or so-called HBI (hot briquetted iron).
[0003] There are also so-called smelting reduction methods in which
the melting process, the production of reduction gas, and the
direct reduction are combined with one another, for example the
methods of the brands COREX, FINEX, HiSmelt, or HiSarna.
[0004] Sponge irons in the form of HDRI, CDRI, and HBI usually
undergo further processing in electric furnaces, which is
extraordinarily energy-intensive. The direct reduction is carried
out using hydrogen and carbon monoxide from natural gas (methane)
and possibly synthesis gas as well as coke oven gas. For example,
in the so-called MIDREX method, first methane is transformed
according to the following reaction:
CH.sub.4+CO.sub.2=2CO+2H.sub.2
[0005] and the iron oxide reacts with the reduction gas, for
example according to the following formula:
Fe.sub.2O.sub.3+6CO(H.sub.2)=2Fe+3CO.sub.2(H.sub.2O)+3
CO(H.sub.2).
[0006] This method also emits CO.sub.2.
[0007] DE 198 53 747 C1 has disclosed a combined process for the
direct reduction of fine ores in which the reduction is to be
carried out with hydrogen or another reduction gas in a horizontal
turbulence layer.
[0008] DE 197 14 512 A1 has disclosed a power station with solar
power generation, an electrolysis unit, and an industrial
metallurgical process; this industrial process relates either to
the power-intensive metal production of aluminum from bauxite or is
intended to be a metallurgical process with hydrogen as a reducing
agent in the production of nonferrous metals such as tungsten,
molybdenum, nickel, or the like or is intended to be a
metallurgical process with hydrogen as a reducing agent using the
direct reduction method in the production of ferrous metals. The
cited document, however, does not explain this in detail.
[0009] WO 2011/018124 has disclosed methods and systems for
producing storable and transportable carbon-based energy sources
using carbon dioxide and using regenerative electrical energy and
fossil fuels. In this case, a percentage of regeneratively produced
methanol is prepared together with a percentage of methanol that is
produced by means of non-regenerative electrical energy and/or by
means of direct reduction and/or by means of partial oxidation
and/or reforming.
[0010] In the direct reduction method, the gas emerging downstream
of the reduction shaft--after it is purified and the water has been
separated out and additional CO.sub.2 separation in the HYL method
or optional additional CO.sub.2 separation in the HYL MIDREX
method--is predominantly fed back into the process as recycling
gas. As a rule, this gas is in turn enriched with natural gas in
order to supply fresh reduction gas. In the HYL method, the gas,
which the gas purification has cooled from approximately
105.degree. C., is heated again to approximately 700 to
1100.degree. C. and then a partial oxidation with oxygen is
performed.
[0011] In the MIDREX method, CO.sub.2 and water are transformed
with natural gas into H.sub.2 and CO in a heated reformer in a
temperature range from approximately 700 to 1100.degree. C. Both
methods share the fact that a partial flow of the gas that has been
purified and is exiting the reduction shaft is introduced and is
enriched with natural gas.
[0012] The reduction process can be expressed with the following
equation:
Fe.sub.2O.sub.3+6CO(H.sub.2)=2Fe+3CO.sub.2(H.sub.2O)+3CO(H.sub.2)
(1)
[0013] In the MIDREX method, the following reactions take place in
the reformer:
CH.sub.4+CO.sub.2.fwdarw.2CO+2H.sub.2 (2)
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2 (3)
[0014] In the HYL method, the following reaction takes place:
CH.sub.4+1/2O.sub.2.fwdarw.CO+2H.sub.2 (4)
[0015] In both methods, the additionally used fossil fuel, namely
natural gas, is used to heat the process gases and to heat the
reformer.
[0016] One object of the invention is to create a method for
heating process gases for direct reduction systems with which the
heating of process gases can be better and more flexibly adapted to
and optimized for an overall process that is adapted to the energy
demand and to the available energy.
[0017] Another object of the invention is to reduce CO.sub.2
emissions.
SUMMARY OF THE INVENTION
[0018] In order to make the heating process more flexible,
according to the invention, the heating of the reduction gases and
of the reformer is changed to an electrical heating.
[0019] Preferably, the electrical energy can be produced from
renewable resources, thus replacing fossil fuels.
[0020] This advantageously increases the flexibility of the process
with regard to the energy sources used; this is achieved through
combined heating by means of a variable use of fossil fuels and
electrical energy.
[0021] In this regard, the invention has the advantage that
electrical current can be considered to be 100% energy so that it
can be completely converted into high temperature heat. The direct
convertibility of electrical energy into heat permits the addition
of a high degree of flexibility, particularly also with regard to
the use of current peaks that are inexpensively available on the
market.
[0022] It is also advantageous that current from renewable energy
sources such as hydroelectric, wind power, or solar energy does not
cause any CO.sub.2 emissions when it is produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention will be explained by way of example in
conjunction with the drawings. In the drawings:
[0024] FIG. 1 shows as an example the HYL Energiron method
according to the prior art, with a natural gas-powered process gas
heating;
[0025] FIG. 2 shows the HYL Energiron method according to the
invention, with an electrically-powered process gas heating;
[0026] FIG. 3 is a very schematic depiction of the MIDREX
method;
[0027] FIG. 4 is a very schematic depiction of an expensive and
complex CO.sub.2-optimized MIDREX method according to the prior
art, with a CO.sub.2-removal unit (e.g. VPSA--vacuum-pressure swing
adsorption).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The HYL method is shown by way of example in FIG. 2 on the
basis of a capacity of two million metric tons of direct reduced
iron (DRI) per year, including an electric arc furnace (EAF). The
process gas from the shaft in which the iron ore is reduced is
first conveyed through a water separation and then through a
CO.sub.2 separation. The circulating gas volume flow in this case
is approximately 500,000 m.sup.3 per hour. Approximately 72,000
m.sup.3 of natural gas per hour is added to this gas flow, 56,000
m.sup.3 of which is used for the reduction and approximately 16,000
m.sup.3 of which is diverted for heating the process gas from 105
to 970.degree. C. Next, oxygen is added to the heated process gas
and this is then fed back into the reduction shaft.
[0029] In a method according to the invention (FIG. 2), the
reduction gas is likewise taken from the shaft and conveyed through
a water separation and a CO.sub.2 separation. Thanks to the
electrical heating of the process gas heating, it is only necessary
to add a quantity of approximately 56,000 m.sup.3 of natural gas
per hour, which is split with oxygen into CO and hydrogen in
accordance with the above-mentioned formulas. The table in FIG. 2
shows that this achieves a 21% reduction in CO.sub.2 per ton of
reduced iron. In addition, because of the electric heating, the
process can be used in an exactly controllable and flexible
way.
[0030] FIG. 3 shows the MIDREX method in which the exhaust gas is
likewise withdrawn in the reduction shaft and divided into a
process gas flow and a heating gas flow. The process gas flow is
conveyed through a process gas compressor until natural gas is
added to it--particularly in a system that is likewise designed for
2 million metric tons of reduced iron per year--in a quantity of
approximately 63,000 m.sup.3 of natural gas per hour. This process
gas passes through a heat exchanger, in which it is preheated by
the exhaust gases from the reformer to 600.degree. C. and then
passes through the reformer and in so doing, is heated to
980.degree. C. and is conveyed back to the shaft as process gas,
which is enriched with additional natural gas and oxygen. The
heating gas is likewise taken from the shaft furnace, enriched with
natural gas, and conveyed into the reformer together with preheated
combustion air. The total required quantity of natural gas is
approximately 68,200 m.sup.3 per hour; by heating the reformer
electrically, it is possible to compensate for approximately 5,100
m.sup.3 of exhaust gas per hour with 52 Megawatts of electric
power. As a result of this, it is possible on the one hand to
achieve a 7.5% reduction of CO.sub.2 per metric ton of reduced iron
ore. In addition, this process can also be controlled in a more
flexible, precise fashion thanks to the electric heating.
[0031] The invention has the advantage of achieving a simple and
quickly implementable option for replacing fossil fuels with
electrical power from renewable energies. CO.sub.2 emissions from
direct reduction systems are also reduced. The invention also makes
it possible to successfully operate direct reduction systems in an
effective and flexible way. In particular, in a steel production
that is adapted to the availability of regenerative energies with
an electrically-powered preheating of process gas, particularly one
with heating based on renewable energies, it is possible to achieve
an improvement and reciprocal adaptation.
[0032] It is also advantageous that such a system can inexpensively
make use of available current peaks.
* * * * *