DESCRIPTION
Title of Invention: Method for Operation of Blast Furnace
5 Technical Field
[OOOlI The present invention relates to a method for
operation of a blast furnace. In particular, it relates
to a method for operation of a blast furnace relating to
(1) blowing a gas with a high hydrogen content from a
10 usual tuyere, (2) blowing a top gas from the usual tuyere
or a tuyere provided at a middle stage of the furnace,
and (3) blowing a gas with a high hydrogen content and a
top gas from the usual tuyere during which making an
oxygen enrichment of the blown gas 10% to 40%.
15 Background Art
[0002] Production of hot metal in a blast furnace
requires a carbonaceous material such as coke, but
reduction of the amount of consumption of the
carbonaceous material per ton of hot metal (below, called
2 0 the "reducing agent rate") is a major objective for
reducing manufacturing costs and has been pursued in the
past.
[0003] For example, PLT 1 has the objective of
reducing costs by increasing as much as possible the
25 amount of consumption of small coal r~rhich was unable to
be used in conventional blast furnace operations. PLT 1
discloses a method for operation of a blast furnace
comprising blowing gas with an oxygen concentration of
40% or more from a tuyere at ordinary temperature, and
3 0 the method comprises blowing the part of the pulverized
coal containing +2 mm coarse grain coal in 5 to 30% and
having a maximum grain size of 5 mm in the pulverized
coal from the tuyere or near the tuyere into the furnace.
Further, PLT 2 adjusts the ratio of the top gas blown
35 from the blast furnace shaft tuyere and the top gas blown
from the bottom tuyere to thereby match the amount of
heat demand to the amount of heat supply of the blast
furnace in the optimal state and enables remarkable
improvement of the coke consumption and the charging
efficiency over the known values. Further, PLT 3
discloses a method for operation of a blast furnace
5 blowing fuel gas together with pulverized coal from a
tuyere of the blast furnace to thereby secure the
combustibility of the pulverized coal and improve the
productivity and reduce the fuel cost (synonymous with'
reducing agent rate). Further, PLT 4 has the objective of
10 stable, high productivity blast furnace operation and
discloses a method for operation of a blast furnace
blowing a gas with an oxygen concentration of 30% to less
than 100% from the tuyere and blowing preheated gas from
a shaft part at a middle stage of the blast furnace so
15 thereby enable use of a large amount of pulverized coal.
[0004] Various technical innovations such as those
explained above have enabled a remarkable improvement in
the operating efficiency and led to the consumption of
carbonaceous materials per ton of hot metal of a level
20 below 500 kg.
[0005] In addition to such reduction of the reducing
agent rate in blast furnace operation and other
improvements of the manufacturing cost, in recent years,
reduction of emissions of carbon dioxide (C02), one of the
25 hothouse gases mainly causing global warming, has become
widely sought. The steel industry, one of the main
industries related to COz emissions, has to respond to
such social demands. Further reduction at blast furnace
operations, which use large amounts of carbonaceous
30 materials for iron and steel manufacture, is becoming
urgent. The Japanese steel industry has established
voluntary action targets to tackle reduction of C02
emissions, but is being pressed to develop new
technologies with eye to the future.
35 [00061 However, none of PLTs 1 to 4 has reduction of
COz emissions as their main objectives. They do not
sufficiently function to fundamentally cut the amount of
generation of COz. In this way, so long as based on
existing operating methods, even if viewed in terms of
heat efficiency, the situation now is that no further
room can be found for major reduction in the carbon
5 consumption.
[00071 In view of such a situation, work on developing
technology aiming at a major reduction in the carbon
consumption in a blast furnace operations has been
proceeding in Europe. That is, in the so-called "ULCOS"
10 project, a blast furnace process based on an oxygen blast
furnace combining C02 separation and recovery techniques,
separating COZ from the top gas, reheating it, and reblowing
it into the furnace from a tuyere newly provided
at the side wall of the furnace body at the middle stage
15 of the blast furnace or from the usual tuyere is being
developed (NPLT 1).
[OOOE] FIG. 1 shows the flow of the above ULCOS blast
furnace process. It is a process flow considered to be
the highest for the effect of reduction of the carbon
20 consumption of a blast furnace. The most different
features from ordinary blast furnace operation are (1)
the point of not using hot air for blast from the usual
tuyere but blowing oxygen and pulverized coal at room
temperature, (2) blowing top gas into the blast furnace
25 after separating COz from all of the top gas to create
"closed gas recycling", and (3) heating recycled gas of
the top gas to a high temperature at a time when blorsring
it from the usual tuyere. Further, in the flow of the
blast furnace process of FIG. 1, the indirect reduction
3 0 degree of ore is a high 89.7%. A 28% reduction ratio of
carbon is achieved for the 289 kg/tHM of the amount of
carbon (C) charged per ton of hot metal (1 tHM) at the
time of normal operation. Further, the C02 is separated
from the top gas by the vacuum pressure swing adsorption
35 method. The "vol" in FIG. 1 shows the amount of gas in
the standard state.
[00091 These features pose serious risks when applied
to commercial blast furnaces. That is, the above (1)
requires that a large amount of pulverized coal is
injected in so as to maintain the temperature of the
combustion zone in front of the tuyere at a suitable
5 value. According to a report of the ULCOS project, the
pulverized coal rate (consumption of pulverized coal per
ton of hot metal) has reached 300 kg/tHM and, as a
result, the coke rate has fallen to 200 kg/tHM to less.
With the current level of art of blast furnace operations
10 which are only demonstrated at a generally 270 kg/tHM or
more coke rate, it is not possible to easily create a
stable operating state. In addition, since the oxygen is
blown at room temperature, no sensible heat is input by
the blown gas. Therefore, even if trouble occurs in
15 operation causing the furnace to cool, the inside of the
furnace cannot be quickly heated and it is difficult to
restore operation. Further, the "closed gas recycling"
operation of (2) has the risk of trace elements contained
in the gas phase (for example, sulfur content etc.) being
2 0 recycled and concentrating in the blast furnace process.
There is a question as to whether stable operation can be
maintained over a long period of time.
[OOlO] In this way, the blast furnace process aimed at
by the ULCOS project would be hard to apply to a
25 commercial blast furnace wherein hot metal production is
required to be continued stably over a long period of
time even if realization were possible on a short time
test operation basis.
[OOll] On the other hand, there is the method for
30 cutting the carbon consumption by assigning hydrogen the
reducing capacity that is one of the roles of carbon in
blast furnace operation. That is, this is an operation
blowing natural gas or coke oven gas (below, called
"COG") or other reducing gas containing hydrogen into the
35 blast furnace. There are a large number of inventions
relating to such an operation method, but in particular
the method for modifying the mixed gas of COz and CO
separated from the top gas to methane (CH4) and again
blowing the modified gas to the blast furnace for the
purpose of reducing COZ emissions of blast furnaces has
been disclosed (PLT 5).
5 [00121 This method separates and recovers C02 (and/or
CO) from the top gas, adds Hz to this to convert it to
CH4, then again blows this into the blast furnace, but
there are issues such as the new need for a CH4 conversion
apparatus and the fact that if just blov~ing in CH4, carbon
10 consumption of the blast furnace cannot be sufficiently
reduced. It cannot be said that the social demand for
reduction of COz emissions explained at the start can be
sufficiently met.
Citation List
15 Patent Literature
[0013] PLT 1. Japanese Patent Publication No. H05-
86444B2
PLT 2. Japanese Patent Publication No. S52-32323B2
PLT 3. Japanese Patent Publication No. 805-179323A
2 0 PLT 4. Japanese Patent Publication No. 863-57704A
PLT 5. Japanese Patent Publication No. 2011-225969A
Nonpatent Literature
[0014] NPLT 1. "Final Evaluation of the Ulcos TGR-BF
Pilot Tests Performed at the LKAB Experimental Blast",
25 Pettrsson Mikael, Silkstrom Peter, Eklund Nicklas,
Proceedings of 6th ICSTI (20121, p. 960
Summary of Invention
Technical Problem
[0015] Greatly reducing the carbon consumption of a
3 0 blast furnace in the range of the existing operating
technology is important. Further, provision of a method
for operation of a blast furnace which can be quickly
restarted even if trouble occurs causing the furnace to
cool down and which enables stable production of hot
35 metal without the risk of trace elements being recycled
and condensed in the blast furnace process has become a
goal. An object of the present invention is to provide a
method for operation of a blast furnace able to greatly
reduce COz emissions and enabling production of hot metal
stably over a long period in a commercial blast furnace.
Solution to Problem
5 [00161 The inventors etc. discovered that by blowing
CH4-containing gas with a high hydrogen content from a
usual tuyere, blowing a top gas from which oxide
components and Hz0 have been removed from a tuyere
provided at a middle stage of the furnace (below,
10 referred to as a "shaft tuyere"), and blowing CH4-
containing gas with a high hydrogen content and top gas
from which oxide components and Hz0 have been removed from
the usual tuyere with making an oxygen enrichment of the
blast from the usual tuyere 10% to 40%, it is possible to
15 greatly reduce CO:! emissions and operate the blast furnace
stably over a long time. Further, the "usual tuyere" is
the tuyere provided at the lower stage of the furnace at
the side below the shaft tuyere to blow pulverized coal
or other auxiliary fuel together with hot air into the
20 blast furnace.
[0017] The present invention was made based on this
finding so as to solve the above problem and has as its
gist the following:
[00181 (1) A method for operation of a blast furnace
25 in which iron ore and coke are charged from a furnace top
and pulverized coal is injected from a usual tuyere,
comprising
blowing in a blast containing at least one of hydrogen
and hydrocarbon from the usual tuyere together with the
30 pulverized coal and
blowing a gas comprised of a top gas of the blast furnace
from which carbon dioxide and steam are removed from a
shaft tuyere into the blast furnace.
(2) The method for operation of a blast furnace
3 5 according to (1) further comprising blowing blast
comprised of top gas of the blast furnace from which
carbon dioxide and steam are removed from the usual
tuyere into the blast furnace.
(3) The method for operation of a blast furnace
according to (1) or (2) wherein the blast from the usual
tuyere is enriched with oxygen by an oxygen enrichment of
5 not less than 10% and not more than a Y% shown in the
following formula:
Y=O.O79xCH4+32
(where, CH4 indicates a vol% of methane in the gas blown
into from the usual tuyere)
10 (4) The method for operation of a blast furnace
according to any one of (1) to (3) wherein a blowing rate
of the gas containing at least one of hydrogen and
hydrocarbon is 30 Nrn3/t~o~r more.
(5) The method for operation of a blast furnace
15 according to any one of (1) to (4) wherein the top gas
blown into from the shaft tuyere is blown in from the
shaft tuyere and a blowing rate of 400 Nrn3/t~M or less at
a temperature of 600°C to 100O0C.
(6) The method for operation of a blast furnace
20 according to any one of (1) to (5) wherein the blowing
rate of top gas blown into from the shaft tuyere is 100
Nm3/t~M or more.
(7) The method for operation of a blast furnace
according to any one of (1) to (6) wherein the gas
25 containing at least one of hydrogen and hydrocarbon blown
in from the usual tuyere contains methane.
(8) The method for operation of a blast furnace
according to (7) wherein the gas containing methane
includes at least one of coke oven gas and natural gas.
30 Advantageous Effects of Invention
[0019] A method for operating a blast furnace to
greatly reduce COz emissions and to produce hot metal
stably over a long period in a commercial blast furnace
is provided.
3 5 Brief Description of Drawings
[00201 FIG. 1 is a view showing a flow of a ULCOS
blast furnace process.
FIG. 2 is a view showing the relationship between the
consumption of gas blown from a usual tuyere (COG and
natural gas) (Nm3/tHM) and the carbon consumption
(kg/tHM) .
5 FIG. 3 is a view showing a (Requirement A + Requirement
B) process in brief.
FIG. 4 is a view showing the change in the carbon
consumption (kg/tHM) associated with blowing a recycled
gas from a shaft tuyere at the time of making COG
10 consumption blown from a usual tuyere 95 ( N ~ ~ / ~iHnM t)h e
(Requirement A + Requirement B) process.
FIG. 5 is a view showing the carbon consumption (kg/tHM)
at the time of additionally blowing in any one of
pulverized coal, COG, or natural gas from a usual tuyere
15 into a blast furnace operating in a standard manner with
no Requirement B and the carbon consumption (kg/tHM) at
the time of additionally blowing in any one of pulverized
coal, COG, or natural gas from a usual tuyere in a
(Requirement A + Requirement 8) process.
2 0 FIG. 6 is a view showing a summary of a (Requirement A +
Requirement B + Requirement C) process.
FIGS. 7 are views showing the relationship among the
operation indices of a blast furnace in the case of
making the COG consumption blown from a usual tuyere a
25 value of 95 (Nrn3/t~~i)n the (Requirement A + Requirement
B + Requirement C) process. FIG. 7A shows the
relationship between the oxygen enrichment and carbon
consumption (kg/tHM). FIG. 78 shows the relationship
between the oxygen enrichment and coke rate (kg/tHM) and
30 the relationship between the oxygen enrichment ( % ) and
blowing rate of recycled gas from a usual tuyere
(Nm3/tHM). FIG. 7C shows the relationship between the
oxygen enrichment and the recycled gas ratio of top gas
( % ) .
3 5 FIGS. 8 are views showing the relationship among the
operation indices of a blast furnace in the case of
making the natural gas consumption blown from a usual
tuyere a value of 95 ( N ~ ~ / ~iHnM t)he (Requirement A +
Requirement B + Requirement C) process. FIG. 8A shows the
relationship between the oxygen enrichment and carbon
consumption (kg/tHM). FIG. 8B shows the relationship
5 between the oxygen enrichment and coke rate (kg/tHM) and
the relationship between the oxygen enrichment ( % ) and
blowing rate of recycled gas from a usual tuyere
( N ~ ~ / ~ H MFI)G.. 8C shows the relationship between the
oxygen enrichment and the recycled gas ratio of top gas
10 ( % ) .
F I G . 9 is a graph showing the relationship between the
COG amount and carbon consumption in the case of changing
the blowing rate of COG blown from a usual tuyere,
further blowing top gas from the usual tuyere without
15 heating the top gas in the Requirement C process, and
increasing the oxygen enrichment of blast from the usual
tuyere in the (Requirement A + Requirement B) process
FIG. 10 is a graph showing the relationship between the
rate of natural gas and carbon consumption in the case of
20 changing the amount of natural gas blown from a usual
tuyere, further blowing top gas from the usual tuyere
without heating the top gas in the the Requirement C
process, and increasing the oxygen enrichment of blast
from the usual tuyere in the (Requirement A + Requirement
25 B) process.
Description of Embodiments
[00211 In order to reduce COz emissions in the process
of production of hot metal, it is necessary to reduce the
carbon charge required for production of hot metal in a
30 blast furnace. As explained above, the main role of
carbon.in a blast furnace is the supply of the heat for
reducin'g and melting the iron ore (below, "iron ore" used
as a general term for sintered ore, pellets obtained by
agglomerating iron ore, or other iron source materials).
3 5 In the present invention, the carbon consumption is
reduced by replacing the carbon reducing agent with
hydrogen for part of the reduction.
COO221 However, in blast furnace operation which
reduces and melts iron ore at a high temperature field in
the furance which is autonomously formed by only charging
raw materials from the top and a blast operation from a
5 usual tuyere, with simply blowing gas having a high
hydrogen content from the usual tuyere, it is not easy to
maintain stable hot metal production. On top of this, it
is difficult to realize a fundamental cut in the carbon
consumption.
10 100231 Therefore, the inventors focused on adding the
following element technologies to existing blast furnace
operation technology so as to overcome the above
problems. That is, they focused on the following
requirements (A) to (C) :
15 (A) Blowing in gas containing at least one of hydrogen
and hydrocarbon from a usual tuyere.
In gas reduction rate of an ore, Hz gas is superior
to even CO gas. Gas containing at least one of CH4 or
other hydrocarbons containing a large amount of hydrogen
2 0 and hydrogen is blown into the blast furnace as much as
possible.
(B) Heating top gas from which CO;! and other oxide
components and steam (H20) have been removed and blowing
it from a shaft tuyere.
25 Top gas wherein a ratio of gas having a reduction
ability is high is produced by removing the oxide
components and steam from the top gas, and the produced
top gas is reutilized. By heating the produced top gas to
a suitable temperature and again blowing it from a shaft
3 0 tuyere into the inside of the blast furnace (below,
referred to as "top gas recycling"), it is possible to
improve the rate of utilization of the furnace reducing
gas.
Further,
35 (C) Blowing top gas from the usual tuyere without
heating the top gas and increasing the oxygen enrichment
of blast from the usual tuyere.
[00241 When blowing top gas from the usual tuyere, it
is important to maintain the theoretical temperature of
the gas generated due to the combustion in the combustion
zone in front of the tuyere (below, referred to simply as
5 the "flame temperature") in a suitable range. For this
reason, it is preferable to not heat the top gas and make
the oxygen enrichment of the blast from the usual tuyere
10% to 40%. As a result, it is possible to maintain the
flame temperature within a suitable range while
10 increasing the reducing gas component in the furnace gas.
Further, it is no longer necessary to increase the
injecting rate of pulverized coal for adjusting the flame
temperature and is possible to avoid an extreme drop in
the coke rate.
15 [00251 Note that, the value X of the oxygen enrichment
( % ) indicates the concentration of oxygen enriched from
the normal blast. For example, the amount of oxygen
concentration enriched from usual blast (air (oxygen
concentration approximately 21%)) is expressed by the
20 following formula:
X(%)=(0.21x~b/60+~o/60)/(~b+Vo/60)x100-21
where Vo: oxygen flow rate (~m~/h)
Vb: Total blowing rate from usual tuyere including flow
rate of top gas (~m~/min)
25 Here, productivity of a blast furvce directly depends on
the rate of oxygen blown into the blast furnace (referred
to as the "rate of blown oxygen"). When making the oxygen
enrichment rise under the condition that productivity is
kept constant, to make the rate of blown oxygen constant,
30 the general practice is to adjust the blowing rate
downward.
[00261 Further, the upper limit value of the oxygen
enrichment is restricted by the presence or absence of
erosion of the lance and also changes by the composition
35 of the gas blown. That is, the composition of the gas
blown causes the upper limit (Y%) of the oxygen
enrichment leading to erosion of the lance due to a
temperature rise to differ. The fact that this is
generally proportional to the content of CH4 with respect
to the composition of gas of the cooling medium in the
gas and that this relationship is expressed by the
following formula was confirmed by the inventors etc.
Y=O.O79xCH4+32
where, Y: upper limit of oxygen enrichment (%)
CH4 in the formula: vol% of methane contained in the gas
blown into
Further, if making the oxygen enrichment excessive, not
only is there the possibility of erosion of the lance
liable to occur, but also the focus of combustion in the
raceway excessively moves to the wall side, insufficient
heat conduction to the deadman or increasing heat loss at
the wall side is invited, and the effect of the charged
material also becomes unstable. By applying the above
requirements, it is possible to achieve the object of the
present invention.
Examples
[00271 Next, examples of the present invention will be
explained, but the present invention is not limited to
these.
[00281 The blast furnace operation was simulated based
on blast furnace numerical analysis to study the effects
of the present invention. For such simulation, for
example, the so-called "blast furnace mathematical model"
shown in K. Takatani, T. Inada, and Y. Ujisawa, ISIJ
International, 39, (1999), p. 15 etc. was used.
[00291 Example 1
In Example 1, first, the inventors investigated in detail
the above Requirement A "blowing gas containing at least
one of hydrogen and a hydrocarbon from a usual tuyere".
[0030] Table 1 shows the standard parameters at the
time of operation of the blast furnace (furnace volume
5300 m3) wherein pulverized coal is injected from the
usual tuyere. Consider an operation of blowing CH4-
containing gas with a high hydirogen content. If making CH4
rise in temperature to 800°C or more, it breaks down under
the heat whereby hydrogen gas is generated and the
hydrogen gas functions as a reducing agent, so the effect
of cutting the carbon consumption is obtained.
5 [0031] The CH4-containing gas contains not only
hydrogen, but also a large amount of hydrogen in the
state of CH4 or other hydrocarbons, so it is possible to
provide it with the function of the reducing material. At
this time, the CH4 concentration is preferably 25% or
10 more. The reason is that if the CH4 concentration is less
than 25%, even if increasing the oxygen enrichment,
combustion in the tuyere-front combustion zone causes a
drop in the function of adjusting the flame temperature
and the effect of the Requirements (B) and (C) on raising
15 the rate of utilization of the furnace reducing gas
becomes insufficient.
[00321 As the CH4-containing gas, it is possible to
employ COG with a high hydrogen content, natural gas with
a high CH4 content, or city gas or shale gas and synthetic
20 gas containing any ratio thereof and other existing gases
containing CH4. The composition of COG changes depending
on the treatment of waste gas and the operating
conditions of the coke oven and differs with each steel
plant. The range of composition is generally CH4: 25 to
25 38% and Hz: 47 to 59%.
COO331 Table 1
Itemperature*
Carbon consumption 1419 kg/tHM I
(* marked items are treated as fixed values in subsequent
Production*
Hot metal
temperature*
Coke rate
Pulverized coal
rate*
Reducing agent rate
simulation of operation)
3 0 COO341 In this regard, to reduce and melt iron ore,
11350 t/d
152OoC
340 kg/tHM
146 k g / t ~ ~
486 kg/tHM
Blast volume
Blast
temperature*
Oxygen enrichment
Blast moisture
Flame
7650 ~m'/min
12OO0C
3.40%
25 g / ~ m ~
2155°C
the inside of the blast furnace is held at a high
temperature under a reducing atmosphere. If blowing COG
or natural gas or other CH4-containing gas into this, the
hydrocarbon content is pyrolyzed under heat and soot dust
5 is generated. There is a danger of the soot filling the
voids among the filler particles of the lumpy coke and
other carbon sources and sintered ore clumps and
therefore lowering the gas permeability inside the
furnace. Therefore, it is preferable to blow the above-
10 mentioned gases into the only region where an oxidizing
atmosphere is formed in the blast furnace, that is, the
combustion region in front of the usual tuyere. That is,
it is desirable to blow in COG or natural gas or other
CH4-containing gas from the usual tuyere along with hot
15 gas or pulverized coal.
roo351 The composition of COG or natural gas differs
somewhat depending on the starting material of coal or on
the production area, but in the simulation of operation,
the contents shown in Table 2-1 and Table 2-2 as typical
20 values were used. Further, the operating parameters were
predicted by calculation using the method of making the
pulverized coal rate constant and adjusting the coke rate
and blowing rate so as to give productivity and hot metal
temperatures shown in Table 1. Further, this is based on
25 the premise that the flame temperature, which is
considered to be important experience-wise in design of
operations, is maintained constant by adjusting the
oxygen enrichment.
[00361 Table 2-1
Composition of coke
oven gas (COG)
Composition of
natural gas
30
CH4
(~01%)
3 7
100
Hz
(~01%)
48
0
CO
(~01%)
12
0
Nz
(~01%)
3
0
- 15 -
Table 2-2
[0037] The relationship between the consumption of gas
(COG and natural gas) blown from the usual tuyere
( N ~ ~ / ~aHnMd )t he carbon consumption (kg/tHM) was obtained
by simulation of blast furnace operation under the
conditions of Table 2-1 and Table 2-2. This relation is
shown in FIG. 2. Here, the carbon consumption (kg/tHM)
means the specific consumption of the amount of carbon,
10 that is, the amount of carbon charged or blown through
coke, pulverized coal, COG, or natural gas per ton of hot
metal. It is an amount directly connected with the COz
emissions accompanying production of hot metal. According
to this figure, it will be understood that the carbon
15 consumption decreases in accordance with the increase in
COG consumption or natural gas consumption. This is
because the hydrogen contained in a large amount in COG
or natural gas contributes to reduction of the iron ore
and the required amount of carbon is kept down.
20 [0038] In Example 1, furthermore, the inventors
investigated in detail operation of a blast furnace
comprising the above Requirement A and further the above
Requirement B "heating top gas from which the oxide
components and steam have been removed and blowing it in
25 from the shaft tuyere".
[0039] -FIG. 3 shows the (Requirement A + Requirement
B) process in brief. The main components of the top gas
exhausted from the top of the blast furnace are CO, COz,
HZ, Nz, and Hz0 (steam), but the steam is removed by the
30 cooling in the existing process of the treatment for
cleaning the exhaust gas. On the other hand, C02 remains
in the top gas, but if removing this, the reduction
ability of the top gas on the ore is greatly restored.
Technology for separating and recovering COz from gas has
Composition of
pulverized coal
Carbon (wt%)
8 2
Hydrogen (wt%)
4
already been developed, so it is sufficient to introduce
the existing technology for separating and removing COz
into the blast furnace process system to thereby perform
the (Requirement A + Requirement B) process.
5 [00401 It is also possible to blow in high temperature
gas with a high hydrogen content from the shaft tuyere in
addition to the top gas from which the oxide components
and Hz0 have been removed. COG is readily available in
steel plants, so it is preferable to use COG. However, if
10 blowing CH4 from the shaft tuyere, soot precipitates and
reduction of the iron ore is inhibited, so it is
preferable to blow COG which has been modified in CH4
content etc. The composition of the modified COG is, for
example, HZ: 68%, CH4: 5%, C2H4: I%, CO: 17%, N2: 2%, and
15 HzO: 7%. In order to secure the reduction ability of top
gas blown from the shaft tuyere, the temperature of the
gas is preferably made 750°C or more. Furthermore, in
order to raise the ratio of the component having the
reduction ability, it is preferable to blow modified COG
2 0 after removing the moisture.
COO411 In order to investigate the advantageous effect
of the (Requirement A + Requirement B) process, the
inventors ran a simulation predicting the effect of
blowing top gas after removal of C02 and H20 from the
25 shaft tuyere under conditions of injecting pulverized
coal from the usual tuyere and blowing COG or natural
gas. Here, it is advantageous to set the position at
which the top ,gas after removal of C02 and HZO is blown
into the blast furnace to the location where gas
30 reduction progresses actively. This position was set to a
position corresponding to the furnace temperature llOO°C ,
calculated at the time of normal operation shown in Table
1. Existing blast furnaces do not have apertures which
gas is blown into at such that location, so a shaft
3 5 tuyere is newly provided.
[0042] The above simulation was performed by recycling
top gas under the conditions of Table 3. In Table 3,
"recycled gas" means recycled gas in the top gas
recycling that is used for simulation. The predicted
values of the parameters at the time of operation were
made the standard parameters in the same way as the case
5 of Table 1.
COO431 Table 3
100441 FIG. 4 is a graph obtained by simulation of an
operation of performing the top gas recycling under the
10 conditions of Table 3 and shows the change in the carbon
consumption (kg/tHM) accompanying an increase in the
blowing rate of recycled gas from the shaft tuyere when
fi xing..CQG.. cnnsllw@f;,i.o.nb lown from the usual tuyere at 95
(kg/tHM). As will be understood from FIG. 4, by
15 increasing the blowing rate of recycled gas from the
shaft tuyere, it is possible to cut the carbon
consumption (kg/tHM). That is, the carbon content
recharged into the furnace through the recycled gas is
not the carbon charged from outside the blast furnace
2 0 system, so the recycling of the top gas based on the
present invention can raise the efficiency of utilization
of the reducing gas and cut the carbon
consumpt*-on( kgl'tHM) .
[00451 However, the effect of reduction of the carbon
25 consumption of the blast furnace by the recycled gas
tends to be saturated~if the blowing rate of the recycled
gas from the shaft tuyere excessively increases. This is
understood to be due to the fact that even if increasing
gas reducing rate in the furnace more than necessary, the
30 speed of the reduction reaction of the iron ore cannot be
kept up with. On the other hand, even in terms of the
Recycling rate of top gas from
shaft tuyere
Blowing rate of recycled gas from
shaft tuyere
Blowing temperature of recycled gas
from shaft tuyere
Blowing rate of COG from usual tuyere
0 to 30%
100 to 600 Nm3/t~M
400 to 100O0C
95 Nrn3/t~M
flow of material in the furnace, excessive reducing gas
in the furnace raises the risk of fluidization of the
packed layer in the furnace or the increase in pressure
drop resulting in the phenomenon of channeling.
5 Therefore, to reliably obtain the effect of cutting the
carbon consumption of a blast furnace and to ensure
stable operation under the conditions for application of
the present invention, it is preferable to make the lorsrer
limit of the blowing rate of recycled gas 100 N~'/~HM and
10 make the upper limit of the recycled gas rate 400 Nrn3/t~M.
[0046] Furthermore, FIG. 4 shows the results of
investigation of the blowing .temperature of the recycled
gas blown from the shaft tuyere to the inside of the
furnace. According to FIG. 4, the higher the temperature
15 of the recycled gas blown from the shaft tuyere is made,
the higher the effect of reduction of the carbon
consumption (kg/tHM). This is due to not only the effect
of reutilization of the reducing gas, but also the effect .,...~..
of the increase of the amount of heat input to the blast
20 furnace thrbugh the sensible heat of the recycled gas.
However, what should be noted is the point that if the
temperature of the recycled gas falls below about 600°C,
almost no effect of reduction of the carbon consumption
(kg/tHM) appears. This phenomenon is due to the fact that
25 if excessively lowering the blowing temperature, the
detrimental effect of both the temperature distribution
in the blast furnace being remarkably lowered and the
progression..of the reduction reaction ending up being
blunted becomes remarkable.
30 [0047] Therefore, in recycling top gas, the
temperature when blovring recycled gas from the sh.a. ft
tuyere to the inside of the blast furnace is preferably
at least 600°C. Further, the upper limit temperature is
preferably kept down to 1000°C or less where there is no
35 danger of the iron ore in the furnace softening-melting
and the progression of gas reduction being obstructed.
[0048l To further investigate the advantageous effect
of the (Requirement A + Requirement B) process, the
inventors investigated a change in the carbon consumption
(kg/tHM) in the case of blowing respectively sole
5 pulverized coal, COG and pulverized coal, and natural gas
and pulverized coal from the usual tuyere in the
(Requirement A + Requirement B) process. First, they
operated a blast furnace operated using a standard method
under the parameters shown in Table 1 so as to
10 respectively blow in COG, natural gas, and pulverized
coal from the usual tuyere under the conditions of Table
4 so that rate of the reducing matter charged from the
usual tuyere (total value of carbon C and hydrogen Hz)
becomes substantially constant. The inventors compared
15 the amount of reduction of the carbon consumption
(kg/tHM) when recirculating the top gas from the shaft
tuyere under conditions of 400 N ~ ~ / ~ H80M0°,C. At this
time, the inventors investigated the oxygen enrichment of
blast for blowing the COG, natural gas, and pulverized
20 coal from the usual tuyere into the inside of the blast
furnace so that the flame temperature becomes constant.
[00491 Table 4
kg/tHM of Table 1
25
[0050] The results of the above operation are shown in
FIG. 5. FIG. 5 shows the carbon consumption (kg/tHM) when
Pulverized
coal
COG
Natural
gas
additionally blowing any one of pulverized coal, COG, or
natural gas from the usual tuyere into a blast furnace
: Blowing rate added to pulverized coal rate of 146
Blowing
rate (*)
84 kg/tHM
95 N ~ ~ / ~ H M
50 N ~ ~ / ~ H M
3 0 which is operated in a standard manner without the
Blowing rate of
reducing matter
7.4 kmol/t~~
7.3 kmol/t~~
6.7 kmol/tHM
Hz content in
reducing
matter
23 mol%
71 mol%
67 mol%
Requirement B and the carbon consumption (kg/tHM) when
additionally blowing any one of pulverized coal, COG, or
natural gas from the usual tuyere into a blast furnace
which is operated in a standard manner in the
5 (Requirement A + Requirement B) process. In FIG. 5, by
combining the operation of blowing COG or natural gas of
a high hydrogen content from the usual tuyere with the
top gas recycling, the effect of reduction of the carbon
consumption (kg/tHM) clearly appears. This effect is due
10 to the characteristic that with respect to the reduction
of iron ore, Hz gas has a faster reaction speed than CO
gas. The Requirement B utilizing this characteristic is
shown to give rise to a special effect under the
Requirement A.
15 [0051] In this way, the top gas recycling in the
present invention exhibits special effects under the
(Requirement A + Requirement B). That is, in an operation
of blowing COG or natural gas with a high hydrogen
content from the usual tuyere, the top gas recycling from
20 the shaft tuyere is particularly effective for reducing
the carbon consumption (kg/tHM) .
[0052] Example 2
Next, the inventors studied the operation of a blast
furnace further adding to the above (Requirement A +
25 Requirement B) the Requirement C of "blowing top gas from
the usual tuyere without heating and increasing the
oxygen enrichment of blast".
roo531 FIG. 6 shows the (Requirement A + Requirement B
+ Requirement C) process in brief. The Requirement C of
30 the present invention further promotes the reduction of
the carbon consumption (kg/tHM) under the (Requirement A
+ Requirement B). By combining the Requirement C, it is
possible to maintain combustion conditions of the tuyerefront
combustion location of the blast furnace at a
3 5 suitable range and reach a coke rate at a level capable
of actual operation by existing operating technology.
roo541 As explained above, the upper limit value of
the oxygen enrichment is restricted by the presence of
erosion of the lance and changes due to the composition
of the blast gas. In the case of the present example of
only blowing COG containing CH4: 37% from the tuyere, if
5 the oxygen enrichment is 35%, the temperature of the
outside of the lance excessively rises and invites
erosion of the lance. On the other hand, in the case of
the later explained Example 3 of blowing natural gas
containing CH4: approximately 100% from the tuyere, if the
10 oxygen enrichment is 40%, erosion of the lance occurs. In
this way, the upper limit (Y%) of the oxygen enrichment
leading to erosion of the lance due to a temperature rise
differs depending on the composition of the gas blown
into. This is proportional to the content of CH4 in the
15 composition of the gas of the cooling medium in the gas.
The relationship is represented by the following formula:
Y=O.O79xCH4+32
where, Y: upper limit of oxygen enrichment (%)
CH4: vol% of CH4 contained in gas blown into
20 [00551 The inventors ran operations for blowing COGcontaining
gas from the usual tuyere under the conditions
shown in Table 5 and investigated the change in the
carbon consumption (kg/tHM) relating to the oxygen
enrichment (10% to 35%) under the condition that a flame
25 temperature is fixed. Further, a shaft tuyere was
provided at the middle stage of the blast furnace, the
blowing rate of recycled gas from the shaft tuyere was
made 200 N~~/LHaMnd 400 N ~ ~ / ~ aHnMd ,th e blowing
temperature of the recycled gas from the shaft tuyere was
3 0 made 800°C. Further, the injecting rate of pulverized coal
- from the usual tuyere in this example was set in the same
way as the value shown in Table 1.
- 22
[0056] Table 5
COO571 FIGS. 7 are views showing the relationship
among the operation indices of a blast furnace in the
5 case of making COG consumption blown from the usual
tuyere 95 ( N ~ ~ / ~ HinM t)h e (Requirement A + Requirement B
+ Requirement C) process under the conditions of Table 5.
FIG. 7A shows the relationship between the oxygen
enrichment (%) and carbon consumption (kg/tHM). The ratio
10 of the Nz (nitrogen) gas in the furnace gas falls along
with an increase in the oxygen enrichment, while the
concentration of the reducing components, that is, Hz and
CO increases, so the effect of the top gas recycling
operation of the Requirement B of the present invention
15 is amplified. FIG. 7B shows the relationship between the
oxygen enrichment (%) and coke rate (kg/tHM) and the
relationship between the oxygen enrichment ( % ) and
blowing rate rec-ycled gas from the usual tuyere (Nrn3/tH~)
By blowing part of the recycled gas at an ordinary
2 0 temperature from the usual tuyere in a suitable amount,
it is possible to maintain the flame temperature without
increasing the pulverized coal rate and possible to
attain a coke rate of actual range capable of stable
operation of 270 kg/tHM or more while cutting the carbon
25 consumption (kg/tHM) of the blast furnace to about 380
kg/tHM. This corresponds to a reduction of approximately
9% with respect to the time of normal operation of Table
Blowing rate of COG
(usual tuyere)
Blowing rate of recycled gas
(shaft tuyere)
Blowing rate of recycled gas
(usual tuyere)
Blowing temperature of recycled
gas (shaft tuyere)
Blowing temperature of recycled
gas (usual tuyere)
Oxygen enrichment
(usual tuyere)
COG 95 Nm3/tHM
200 N ~ ~ / ~ H40M0 ;N rn3/tH~
Rate required for
maintaining flame
temperature at 2155'C
800°C
Ordinary temperature
(25OC)
15 to 40%
1.
[0058] FIG. 7C shows the relationship between the
oxygen enrichment ( % ) and the recycled gas ratio of top
gas ( % ) . The recycled gas ratio ( % ) of the top gas means
5 the volume ratio (%) of the blowing rate of reduced gas
from the usual tuyere and shaft tuyere with respect to
the total rate of top gas. Along with the increase of the
oxygen enrichment, the blowing rate of reducing gas from
the usual tuyere increases and the flame temperature is
10 maintained constant (2155OC) . *Here, the present invention
is not restricted in the coke rate level of the blast
furnace operation.
[0059] Normally, in blast furnace operation, to secure
the heat generation at the bottom of the furnace, the
15 general practice is to adjust the blowing conditions so
that the combustion temperature in front of the tuyere
becomes a constant approximately 2155°C. If operating
under conditions where the flame temperature falls, a
drop in furnace heat and hot metal temperature is caused
20 over a long term and tapping problems, cooldown, and
other serious operational trouble will be induced. In the
operation for blowing COG or natural gas from the tuyere,
the gas sensible heat introduced falls due to the
endothermic reaction accompanying decomposition of the
25 main component CH4 and blowing of cooling air into the
blast furnace, and the flame temperature falls.
[00601 To compensate for this, oxygen enrichment of
blast is effeckive. Further, the main components of the
top gas are CO and Hz, SO the recycled gas of the top gas
30 does not burn in front of the tuyere and is blown in by
the cooling air, so the sensible heat of the introduced
gas falls and the flame temperature falls. In this case
as well, it is possible to raise the oxygen enrichment in
accordance with the blowing rate of recycled gas to
35 compensate for the heat. If raising the oxygen enrichment
, in order to make productivity constant, the blowing
rate is decreased and the charging rate of oxygen into
the furnace is adjusted to become constant. As a result,
along with the increase of the oxygen enrichment, the Nz
in the furnace gas is decreased and the concentration of
the CO, H2, or other reducing gas relatively rises. This
5 leads to amplification of the effect of the top gas
recycling operation of the Requirement B.
[0061] Example 3
F I G S . 8 show the relationship among the operation indices
of a blast furnace in the case of making natural gas
10 consumption blown from the usual tuyere 95 (Nrn3/t~M)i n
the (Requirement A t Requirement B + Requirement C)
process. Here, the operating conditions in the
(Requirement A t Requirement B + Requirement C) process
of F I G . 8 are shown in Table 6. Except for the blown gas
15 changing from COG to natural gas, making the blowing rate
of recycled gas from the shaft tuyere 400 N ~ ~ / ~anHd M
making the blowing temperature 800°C, the conditions are
the same as the conditions studied in Table 5.
[0062] Table 6
20
[0063] F I G . 8A show the relationship between the
oxygen enrichment and the carbon consumption (kg/tHM).
F I G . 8B shows the relationship between the oxygen
enrichment and coke rate (kg/tHM) and the relationship
25 between the oxygen enrichment ( % ) and blowing rate of
recycled gas from the usual tuyere (Nm3/t~M).FI G. 8C
Blowing rate of natural gas
(usual tuyere)
Blowing rate of recycled gas
(shaft tuyere)
Blowing rate of recycled gas
(usual tuyere)
Blowing temperature of recycled
gas (shaft tuyere)
Blowing temperature of recycied
gas (usual tuyere)
Oxygen enrichment
(usual tuyere)
95 N ~ ~ / ~ H M
400 Nm3/tHM
Rate required for
maintaining flame
temperature at 2155OC
8 0 O°C
Ordinary temperature
(25°C)
15 to 40%
shows the relationship between the oxygen enrichment and
the recycled gas ratio of top gas ( % ) . In this case, the
blast furnace has to be operated at a coke rate level of
250 kg/tHM or less, but by making the oxygen enrichment
5 up to 40%, it is possible to cut the carbon consumption
of the blast furnace down to about 350 kg/tHM. This
corresponds to a cut of approximately 15% with respect to
the time of normal operation of Table 1.
LO0641 Example 4
10 In Example 4, the inventors investigated the effect in
the case of changing the amount of COG or natural gas
blown from the usual tuyere in the (Requirement A +
Requirement B) process and further blowing top gas from
the usual tuyere without heating and increasing the
15 oxygen enrichment of blast from the usual tuyere in the
Requirement C process.
COO651 FIG. 9 shows an example of changing the rate of
COG blown from the usual tuyere into a blast furnace
adjusted in coke rate in the (Requirement A + Requirement
20 B) process so that the hot metal temperature does not
fall under 1520°C by the asterisked parameters of Table 1
so as to realize a stable operating state of the blast
furnace. As shown in FIG. 9, when making the blowing rate
of the top gas recycling from the shaft tuyere 400 Nm3/t~M
25 in the Requirement B, no large improvement was seen in
the carbon consumption with a rate of COG blown from the
usual tuyere of less than 30 N ~ ~ / ~ THhMis. i s due to the
fact that the rate of COG blown from the usual tuyere is
too small and the effect of amplification of Hz recycling
3 0 could not be sufficiently exhibited. On the other hand,
if making the blowing rate of COG from the usual tuyere
30 Nm3/tHM or more, the carbon consumption was greatly
improved along with an increase in the blowing rate of
COG.
35 100661 When making the oxygen enrichment of blast
from the usual tuyere increase up to 35% and
simultaneously making the rate of top gas blown from the
usual tuyere 225 Nrn3/tHM in the Requirement C, if the rate
of COG blown from the usual tuyere is less than 30
Nrn3/t~M, in the same way as the Requirement B, no large
improvement could be seen in the carbon consumption. This
5 is due to the blowing rate being too small and the effect
of amplification of Hz recycling not being sufficiently
exhibited. On the other hand, when a rate of COG blown
from the usual tuyere is 30 Nrn3/tHM or more, the carbon
consumption could be greatly improved over the
10 (Requirement A + Requirement B) process in accordance
with the increase in the blowing rate of COG. Note that,
in each requirement, the more the blowing rate is made to
increase, the more the carbon consumption can be lowered.
100671 FIG. 10 shows an example changing the blowing
15 rate of natural gas from the usual tuyere into a blast
furnace adjusted in coke rate in the (Requirement
A+Requirement'B) process so that the hot metal
temperature does not fall under 1520°C under the
asterisked parameters in Table 1 for realizing a stable
20 operating state. As with the case of blowing COG from the
usual tuyere, when making the blowing rate of top gas
recycling from the shaft tuyere 400 Nrn3/t~M in the
Requirement B, with a rate of natural gas blown from the
usual tuyere of less than 30 Nm3/t~M, no large improvement
25 is seen in the carbon consumption. Hor-rever, when
increasing the oxygen enrichment of blast from the usual
tuyere up to 40% and simultaneously making the rate of
top gas blown from the usual tuyere 175 Nm3/tHM in the
Requirement C, if making the rate of natural gas blown
30 from the usual tuyere 30 Nm3/tHM or more, the carbon
consumption vias greatly improved along with an increase
in the blowing rate. Note that, the rate of use of
natural gas is not limited, but a rise in manufacturing
cost is invited, so it is possible to set the rate of use
35 of natural gas in the range giving a predetermined
effect.
[0068] As explained above, in the future, if operating
technology is improved and the minimum coke rate level
which enables stable operation further falls, it will
become possible to more positively apply the present
invention (to a raise in the oxygen enrichment) and to
5 greatly reduce the carbon consumption of the blast
furnace. Note that, preferred embodiments of the present
invention were explained, but the present invention is
not limited to these examples. It is clear to a person
having ordinary skill in the technical field to which the
10 present invention belongs that various changes or
alterations could be made within the technical idea
described in the claims. These will also naturally be
understood as falling in the technical scope of the
present invention.
15 Industrial Applicability
[00691 According to the present invention, it is
possible to provide a method for operation of a blast
furnace able to reduce COz emissions and produce hot metal
in a commercial blast furnace stably over a long period.
CLAIMS
Claim 1. (Amended) A method f o r operation o f a b l a s t
furnace i n which i r o n ore and coke a-re charged from a
furnace top and pulverized coal is i n j e c t e d from a usual
tuyere, comprising
blowing a b l a s t containing a t l e a s t one of
hydrogen and hydrocarbon from said;Qsual tuyere together
with s a i d pulverized coal, -.. ,
blowing a gas comprised.$& a top gas of the
b l a s t furnace from which carbon d i w i d e and steam are
removed from a s h a f t tuyere i n t .~&e : b l a s t furnace, and
blowing s a i d top gas frofiii:the usual tuyere
without heating and r a i s i n g an'-oxg9en enrichment o f gas
blown f rom the usual tuyere. s -.. .r.;c: . .
Claim 2 . The method for opera.tion o f a b l a s t furnace
according t o claim 1 f u r t h e r comprising blowing b l a s t
comprised of top gas of the b l a s t ' + u r n a c e from which
carbon dioxide and steam are removed from the usual
tuyere i n t o the b l a s t furnace.
Claim 3 . The method f o r operation of a b l a s t furnace
according t o claim 1 or 2 wherein'said b l a s t from the
usual tuyere is enriched with.oxygen by an oxygen
enrichment of 10% not less than and not more than by a Y%
shown i n the following formula:. .ts:
(where, CH4 i n d i c a t e s a vol% of meQhane i n gas blown i n
from the usual t u y e r e )
. C l a i m 4 . The method f o r opera$titi'on of a b l a s t furnace
according t o any one of claims I. fxi:l3 where& a blowing ' '
r a t e of s a i d gas containing a.t.letmt one of hydrogen and
hydrocarbon is 30 Nm3/tHM or more.->:\!
Claim 5 . The method for operati'on of a b l a s t furnace
according t o any one of claims 1 t0:4 wherein s a i d top
gas blown from the s h a f t tuyere i s Mown from s a i d s h a f t
tuyere by a blowing r a t e of 400 N ~ . ~ / $ H Mo r less a t a- : . .
*. . temperature of 600°C t o 1000°C. . - ~:
Claim 6. The method for operatipn of a b l a s t furnace
. . .'. .j'. :'.
according t o any one of claims 1 t o 5 wherein the blovring ' ' ,
r a t e of the top gas blown from s a i d s h a f t tuyere is 100
N ~ I ~ / ~ HoMr more.
Claim 7 . The method f o r operation of a b l a s t furnace ;
5 according t o any one of claims 1 t o 6 wherein s a i d gas : '
containing a t l e a s t one of hydrogen and hydrocarbon blown
from s a i d usual tuyere contains methane.
Claim 8. The method f o r operation of a b l a s t furnace
according t o claim 7 wherein s a i d gas containing methane
10 includes a t l e a s t one of coke oven gas and n a t u r a l gas.