Patent Application
20100146982
This particular invention relates to enriching air supplied to a hydrocarbon-injected iron-making blast furnace and using the flue or top gas from the furnace to generate power. By “hydrocarbon” it is meant a fuel or reducing agent comprising oil, natural gas, petroleum coke, coal, among other materials and mixtures thereof.
Methods for combining iron production and power generation are described in “Oxygen blast furnace and combined cycle (OBF-CC)—an efficient iron-making and power generation process”, Y. Jianwei et al., Energy 28 (2003) 825-835.
Air Separation Units (ASUs) and methods for making oxygen therein are described in U.S. Pat. No. 5,268,019; hereby incorporated by reference. Methods for combining iron making process with an ASU are described in U.S. Pat. No. 5,582,029 and WO 9728284-A1.
Methods for combining an ASU and power generation are described in “Developments in iron making and opportunities for power generation”, 1999 Gasification Technologies Conference, San Francisco, Calif., Oct. 17-20, 1999. This publication also describes using coal in iron production in order to reduce the amount of coke that is required.
U.S. Pat. No. 6,216,441 B1 discloses removal of inert gases from flue or top gas prior to combustion of it in a gas turbine or combined cycle power plant.
The disclosure of the previously identified patents and patent applications is hereby incorporated by reference.
There is a need in this art for an integrated system that combines coal gasification and oxygen enriched iron production from a blast furnace with power generation, and, if desired, carbon dioxide removal and sequestration.
The instant invention solves problems associated with combining conventional iron production methods with higher efficiency combined cycle power production from combustion of the top gas by providing an integrated system based upon maximizing the caloric or heat value in the top gas, and simultaneously increasing the productivity of the furnace hot metal production. The integrated system includes operating the blast furnace in a manner wherein at least one of the following is achieved: a) pulverized coal injection (PCI) rate is maximized and combined with b) “super-enrichment” of air supplied to the blast furnace with oxygen (e.g., via an ASU, a membrane, among other suitable means for generating oxygen) wherein “super-enrichment” of the blast air with oxygen means enriching the blast to an oxygen concentration above about 32% and up to about 70% by molar volume (e.g., at least 40% to about 60% by molar volume), c) steam is added to the oxygen enriched blast to enhance production of hydrogen as well as control temperature in the lower part of the blast furnace (e.g., steam can be extracted from the combined cycle (CC) steam turbine), and d) coke consumption rate is minimized to the extent that it is sufficient to provide support and gas permeability during the ore reduction process. The super enriched air (and if desired steam) enhance the coal gasification in the furnace to produce reducing gases of CO and H2, thus replacing more expensive metallurgical coke. The super-enriched air also permits at least one of: a) increasing in the amount of coal used in the furnace, b) more complete gasification, c) improving the iron-making productivity of the given furnace, and d) generating a higher calorific value, or fuel-containing top gas that can be matched to a downstream process for maximum efficiency of downstream process operation (e.g., in some cases, with little or no supplemental fuel).
Maximizing the PCI injection leverages the efficient desulfurizing and energy converting characteristics of the blast furnace to produce in combination with downstream top gas treatment and conversion processes and equipment at least one of power, syngas, steam, among other benefits. Operation of a blast furnace with PCI injection can be combined with super-enriched air that can obviate the need for conventional hot blast stoves.
One aspect of the invention relates to iron production and coal gasification that is integrated with combined cycle power generation.
Another aspect of the invention relates to iron production and coal gasification where oxygen injected into the blast furnace is generated from an ASU that is also integrated into the combined cycle gas turbine to provide nitrogen for cooling and mass enhancing, and any excess compressed air from the compressor supplying combustion air to the gas turbine is supplied to the ASU.
Another aspect of the invention relates to iron production and coal gasification that is integrated with combined cycle power generation and carbon dioxide capture for possible sequestration both of which are enabled and enhanced by the reduced concentration of N2 in the topgas resulting from the use of super enriched oxygen blast. Capturing or removing carbon dioxide can increase the fuel value of the topgas, reduce or eliminate the amount of carbon dioxide supplied to the furnace in an optional recycle loop, among other benefits.
A further aspect of the invention relates to iron production and coal gasification that is integrated with combined cycle power generation and carbon dioxide capture, with the additional inclusion of a shift reactor prior, to the carbon dioxide removal and capture step, so as to enable greater proportions of carbon dioxide to be removed and captured.
Another aspect of the invention relates to iron production and coal gasification that is integrated with combined cycle power generation and CO2 capture, taking advantage of the steam generated from the heat contained in the exhaust from the gas turbine or the nitrogen from the ASU to drive the shift reactor or a CO2 removal (e.g., sequestration) process.
A further aspect of the invention relates to iron production and coal gasification that is integrated with top gas cleanup and/or CO2 removal for production of syngas.
One aspect of the invention relates to a method for producing iron comprising:
introducing iron ore, coke and coal into a blast furnace, whereby the coal is gasified by introducing super-enriched air into a blast furnace, and recovering from the blast furnace a top gas, using the top gas to generate power; and, recovering hot metal from the blast furnace.
Another aspect of the invention relates to a method for generating power comprising:
providing a top gas, or portion of top gas, from a blast furnace comprising carbon monoxide, carbon dioxide, hydrogen, nitrogen in concentration such that it has a calorific value matched, without supplemental fuel, to fall within the required fuel value operating range of a downstream gas turbine,
introducing the gas into a gas turbine under conditions sufficient to generate power, and;
introducing the exhaust from the gas turbine into a heat recovery steam generator under conditions sufficient to generate power.
A further aspect of the invention relates to a method for gasifying coal and producing iron comprising:
The apparatus, components, systems and methods illustrated in these Figures can be employed individually or in combination to obtain additional aspects of the invention that are not illustrated by the Figures.
The instant invention relates to apparatus, processes and compositions for providing an integrated system that utilizes oxygen enrichment of air supplied to a blast furnace (e.g., via an ASU) to efficiently combine coal gasification and blast furnace iron production. The integrated system gasifies coal in situ within the iron blast furnace and produces a flue or furnace top-gas having improved utility for power generation and, if desired, from which carbon dioxide can be removed and sequestered.
Additional oxygen beyond that which is normally supplied to the air blast is either directly injected or combined with the blast air being supplied to the blast furnace to enhance the effectiveness of the blast furnace to accept a relatively large amount of injected hydrocarbons or fossil fuels, for example coal from a pulverized coal injection system (PCI), and/or to enable more pulverized coal to be injected. Such a PCI system reduces the amount of coke that is required for iron production in a blast furnace. In addition, supplying oxygen enriched air to the blast furnace can produce: 1) a flue or top-gas that has reduced nitrogen content and increased fuel or calorific value, 2) a top gas that has enhanced value for power generation, 3) a top gas that is compatible with gas turbine power generators, 4) a top gas obtained by in situ coal gasification within the blast furnace, among other benefits. In a marked improvement over conventional methods, the integrated system of the instant invention obtains a top gas that can have an increased concentration of hydrogen and carbon monoxide and, in some cases, a reduced amount of nitrogen.
In one aspect of the invention, coal can be combined or separately co-injected with other hydrocarbons.
The instant invention permits controlling and selecting a desired economic base of operation that is achieved by valuing the benefit and cost of the following variables: coke, coal, iron, oxygen, power and stove utilization (i.e., hot blast). For a given cost of coke, oxygen and coal, the optimum value of iron and power can be selected. Generally, increasing the amount of coal introduced into the blast furnace will allow to increase the amount of oxygen used, but reduce the amount of coke employed and in turn reduce the cost of iron production. Similarly, increasing the amount of coal will also allow to increase the amount of oxygen used and allow to lower the hot blast temperature (e.g., the amount of heat supplied from the stoves can be reduced), and increase the amount of power that can be generated. Depending upon the relative economic value of the foregoing variables, it may be possible to eliminate the hot blast (stoves) and hence use the energy previously consumed by the stoves to generate power, or for operating a water shift reactor, carbon dioxide removal, among other systems.
If desired, the oxygen used for enriching air that is introduced into a blast furnace can be supplied from any suitable gas separation system such as cryogenic distillation including an ASU, a membrane (e.g., an ion transport membrane), pressure vacuum swing adsorption (PVSA), among other systems suitable for generating an oxygen containing stream that can be used for enriching air. As a result of employing higher levels of oxygen enrichment or super enrichment, the oxygen enriched blast may be supplied directly to a blast furnace at ambient temperature conditions thereby obviating, if desired, the need for hot blast stoves (e.g., stoves that use top gas to heat air prior to introduction to the blast furnace), and permitting the energy typically consumed by the hot blast stoves to become additionally available for generating power. Information relating to introducing oxygen enriched air into a PCI blast furnace can also be found in A. Poos and N. Pongis, “Potentials and problems of high coal injection rates”, 1990 Ironmaking Conference Proceedings.
While any suitable ASU can be employed, an example of suitable ASUs are those supplied commercially by Air Products And Chemicals, Inc., Allentown, Pa. Suitable ASUs are also described in U.S. Pat. No. 5,268,019; hereby incorporated by reference. A gas separation system such as an ASU can produce an oxygen containing stream which when combined with air in blast furnace air can have an oxygen concentration of from about 40 to less than about 100% by volume. An oxygen containing stream from the ASU can be blended or combined with air (either heated or ambient) to provide a predetermined concentration of oxygen to the blast furnace (e.g., from about 35 to up to nearly pure oxygen, but more typically between about 40 to about 70% oxygen). An oxygen containing stream from the ASU can also be supplied to the duct burner of the HRSG to enhance combustion of relatively low-calorific topgas (e.g. for improving steam generation). If desired, nitrogen produced from the ASU can be supplied to a gas turbine (e.g., as described below a gas turbine used to generate power from the blast furnace top gas), in order to increase the effectiveness of the turbine and to maintain proper combustion temperature and mass flow volume. Similarly, excess compressed air generated by the feed compressor to the gas turbine can be extracted and supplied to the ASU in order to increase the effectiveness of the ASU, or the compressed air can be used to supplement or supplant air that is supplied to the blast furnace stoves (e.g., air that is introduced into the stoves by an air blower). Power generated from a generator driven by a gas or steam turbine can in turn be supplied to the ASU
If desired, the oxygen enriched air being supplied to a fossil fuel injected (e.g., PCI), blast furnace can be modified by introducing steam (e.g., steam generated in connection with power generation described below). Steam can be combined with the oxygen enriched air or supplied separately to the PCI blast furnace. Introducing steam to the blast furnace can have two beneficial and simultaneous effects. First, it can be used to moderate the flame temperature in the lower part of the blast furnace which might otherwise be too high due to oxygen enrichment. Second, the reaction of steam with the injected pulverized coal and hot coke present in the lower part of the blast furnace will increase the amount of hydrogen (and in some cases carbon monoxide) in the gas produced within the blast furnace. This additional hydrogen gas specie can then participate in driving iron reduction while also enhancing the top gas calorific content which, in turn, makes the top gas more useful for power generation (e.g., in combined cycle power generation). While any suitable concentration of steam can be employed, typically the amount of steam ranges from about 10 up to about 250 grams/Nm3 of blast volume (e.g., from about 50 to about 150 grams/Nm3 and in some cases from about 20 to about 60 grams/Nm3 of blast volume).
In one aspect of the invention, the oxygen enriched air further comprises steam, at least one member selected from the group consisting of carbon monoxide, carbon dioxide and hydrogen. Oxygen can be obtained from an ASU and carbon monoxide, carbon dioxide and hydrogen obtained by recycling a portion of the top gas. As a result, a top gas that is substantially free of nitrogen can be produced. By “substantially free” it is meant that the top gas comprises less than about ten (10) volume percent nitrogen (e.g., less than about 8 volume percent).
The instant invention can permit lowering the temperature of the blast (e.g., comprising oxygen enriched air), that is introduced into the furnace from a typical hot blast temperature of about 1100 to 1250 C, to 850 C and in some cases to about 600 C. Generally, a lower blast temperature will depend upon and employ an increased amount of oxygen. By “blast temperature” it is meant the equilibrated temperature of the oxygen enriched air stream as it enters the blast furnace at the tuyeres. If desired, a blast temperature can be prepared by mixing ambient temperature oxygen into ambient temperature air ahead of the stoves and then heating the entire mixture to the desired and equilibrated blast temperature. Alternatively, the ambient temperature air can be heated alone in the stoves to a temperature above that of the desired blast temperature, and the relatively cold ambient temperature oxygen can be added into the heated air blast downstream of the stoves to produce the mixture of oxygen enriched air blast at the desired concentration of oxygen and at the desired hot blast temperature. The temperature of components used to prepare the blast can vary and can be combined in any suitable manner to produce the hot air blast at the desired temperature and oxygen concentration. While the oxygen and air are normally combined prior to being introduced into the furnace, if desired, they can be introduced separately and an ‘equivalent’ hot blast temperature can be obtained which corresponds to the temperature of the oxygen enriched blast if the two streams had been mixed and equilibrated in temperature together.
The temperature of the oxygen enriched air blast, PCI rate, coke rate, hot metal flow or release rate, and oxygen/steam concentration can be controlled in order to obtain a top gas having a desired calorific value. Typically the calorific value of the top gas will range from about 110 to about 170 btu/scf (e.g., the calorific value can vary depending upon the concentration of oxygen used in the air blast such that the top gas calorific value may vary from about 110 to about 130 btu/scf when the oxygen enriched air comprises about 40 vol. % oxygen to about 135 to about 170 btu/scf when the enriched air comprises about 60 vol % oxygen).
One aspect of the invention relates to removing carbon dioxide from the top gas. Any suitable method can be employed for removing carbon dioxide from the top gas. In one aspect of the invention, the carbon dioxide is removed by using stripping absorbent beds such those as described in U.S. Pat. No. 5,582,029; hereby incorporated by reference. In another aspect of the invention, carbon dioxide is removed by being exposed to a solution comprising MEA (e.g., a solution comprising about 20% MEA), among other suitable solutions. By removing carbon dioxide from the top gas, the instant invention permits controlling the amount of carbon dioxide released into the environment as well as provides a top gas having improved fuel value for subsequent power generation, among other uses.
If desired, prior to removing the carbon dioxide from the top gas, carbon monoxide in the top gas can be converted to carbon dioxide by a shift reactor. That is, a reactor wherein carbon monoxide and water are converted into carbon dioxide and hydrogen (e.g., as described in U.S. Patent Application Publication No. US20060188435A1 and U.S. Pat. No. 4,725,381A; both hereby incorporated by reference). The carbon dioxide can be removed in the manner described above and the remaining hydrogen employed for generating power, purifying petroleum products, supplied to a fuel cell for generating power, among other uses. Alternatively, the top gas can be converted into ammonia, methanol, among other products, in addition to or instead of being used for generating power.
In another aspect of the invention, the top gas can be used for generating power. While the top gas can be used in any suitable power generation system, an example of a suitable combined cycle power generation system is disclosed in U.S. Pat. No. 6,216,441 B1 (hereby incorporated by reference). The top gas can be combusted in a gas turbine and/or a heat recovery steam generator in order to generate power. If desired, carbon dioxide can be removed (and, if desired, sequestered, used in subsequent chemical processes, among other uses), from the top gas prior to introducing the top gas to the power generation system. Capturing CO2 prior to combustion can be more desirable than capturing CO2 from the exhaust gas of the HRSG where the CO2 content of the gas would be more dilute and the exhaust gas would contain O2.
In one aspect of the invention, exhaust emitted from the power generation system is substantially free of carbon dioxide. By “substantially free” of carbon dioxide it is meant that the exhaust contains less than about five vol. % carbon dioxide. The exhaust can be substantially free of carbon dioxide and carbon monoxide by employing the previously described water shift reactor to convert carbon monoxide and water into carbon dioxide and hydrogen prior to the CO2 removal process (e.g., a water shift process is performed prior to CO2 removal such as illustrated in
In a further aspect of the invention, a series of gas and steam turbines can be employed for generating power. The number of turbines, calorific value of the top gas, ratios/rates of materials supplied to the turbines, and supplemental fuel gas can be controlled in order to maximize the economic value of the inventive method and system (e.g., in one aspect to maximize the amount of power generated).
In one aspect of the invention, the power generation system can be operated without supplying supplemental quantities of fuel gas from an external source (sometimes referred to as “trim fuel”). Typically, in this aspect of the invention the gas turbine and the HRSG will be operated with less than about ten percent (10%) of the calorific value of the gas being obtained from supplemental fuels or externally generated or supplied fuel gas (e.g., natural gas, carbon monoxide, among other fuels). While a desired aspect of the invention is to reduce or eliminate usage of supplemental fuels, all aspects of the instant invention do not preclude usage of supplemental fuels.
Certain aspects of the invention are illustrated by the drawings. Referring now to the drawings,
In the aspect of the invention illustrated in
In the event, the blast furnace is designed and operated with high top pressure, there may be an existing topgas pressure recovery let-down turbine (not shown in
The hot exhaust from the gas turbine is directed to a Heat Recovery Steam Generator (HRSG) to make steam and to produce more power via steam turbine (“Combined Cycle”).
To maximize the use of the topgas and accommodate with flow variations within the blast furnace, a gas collection and pressure management system is installed. This includes a gasholder, specialty controls, and trim gas mixing system (as required).
The technical effects of the system illustrated in
The following Examples are provided to illustrate certain aspects of the invention and shall not limit the scope of the claims appended hereto.
Example A illustrates the affect of increased coal injection and increased oxygen concentration in the blast on blast furnace performance. A blast furnace of 2,855 m3 working volume is normally operated according to the parameters of Table 1 column (a) (shown below). These parameters are used for purposes of comparison to illustrate certain desirable aspects of the instant invention by using a mass and energy balance computer model for the Blast Furnace. The computer model used in the instant Example is a conventional two-stage mass and heat balance model as described and employing the equations disclosed in “Principals of Blast Furnace Ironmaking” by Anil K. Biswas (1981 Cootha Publishing House, Brisbane, Australia). The computer model is used to illustrate the blast furnace operation at increasing amounts of pulverized coal injection and increased oxygen concentration in the hot air blast.
The composition of charge materials is held constant as well as the quantity (18 g/Nm3) of moisture in the hot blast. Next, coal and oxygen are introduced into the blast furnace operation according to the values shown in cases (b) through (i) of Table 1. These parameters include increasing the coal injection rate and the blast oxygen content. Depending on the hot blast temperature, the blast furnace operation could be balanced at different coke rates for each of the increase coal injection rates. The affect of these parameters on the production rate of both topgas and hot metal from the blast furnace are shown in Table 1.
This Example also illustrates the affect of using a portion of the topgas as fuel to fire the stoves. The portion employed as fuel is dependent upon amount of hot blast to be used in the process and its temperature. Subtracting the portion of topgas used for stove firing from the total topgas produced gives the remaining amount of topgas available to be used for other purposes such as downstream power production. Multiplying the quantity of remaining topgas available for other uses by its calorific content gives the amount of thermal energy available for conversion to electricity.
For an increase of pulverized coal injection (up to the operational maximum), it is possible to balance the operation across a spectrum of new operating parameters. Columns (b) and (c) of Table 1 show two different operating cases wherein the rate of pulverized coal injection was increased from the base case of 150 Kg/T of column (a) to 200 Kg/T.
In the case of operation shown in (b), the coal injection is increased to 200 Kg/T while the hot blast temperature is maintained at a constant 1250° C. For this case, the oxygen concentration in the blast is increased from 26.6% oxygen in the base case (a) to 30.1% oxygen in case (b). As shown in Table 1, the results of this balanced operation are:
In the case of the operation shown in (c), coal injection is increased to the same level as in case (b), i.e., 200 Kg/T, but the oxygen concentration in the air blast is further increased to 34.8% in balanced operation. The results of this operation are:
Comparing cases (b) and (c) against base operation (a) illustrates that the overall operation of the blast furnace can be improved and selectively adjusted to find an optimum in economical production depending on the costs of coke, coal, and oxygen; and the relative value of hot metal production, and the value of the topgas to downstream power production.
Referring now to cases (d), (e) and (f), these cases illustrate increasing the coal injection rate to 240 Kg/T. Each of these three cases are achieved with increased oxygen percentages in the blast. However, depending on the percentage of oxygen added to the blast, the hot blast temperature employed for balanced operation changes for the given coal injection rate. As before, the highest amount of topgas and topgas energy for power production occurs when the percentage of oxygen in the air blast is maximized, the hot blast temperature is lowered, and production of iron is restrained at the fixed coal injection rate.
Among the three cases (d), (e) and (f), the lowest coke rate occurs at the highest hot blast temperature case (d). As the coke introduction rate in the blast furnace reduces, effective operation of the blast furnace may become difficult due to complications associated with even distribution of the coke. Accordingly, these examples illustrate operations employing at least 262 Kg (or more) of coke per Ton of hot metal (i.e., 262 Kg of coke per Ton of hot metal has been demonstrated to be effective).
Coal Injection is increased further to 280 Kg/T shown in cases (g) and (h). In these two cases, the hot blast temperature is reduced in order to maintain balanced operation while increasing oxygen enrichment of the air blast in order to maintain at least 262 Kg/T of coke in the charge mix. The results of cases (g) and (h) are:
i.) even greater production of hot metal, and
ii.) topgas with increased thermal energy for downstream power production, over all of the previous cases.
Further increase coal injection to 320 Kg/T in case (i) of Table 1 while holding hot blast temperature equivalent to the 600° C. of previous case (h) results in a coke rate requirement of only 239 Kg/T. To allow for balanced operation at a level of (320 Kg/T) of coal injection and with the level of oxygen enrichment shown, further decreases in the hot blast temperature would be appropriate to allow for more coke in the charge while maintaining a balanced operation.
At some threshold level of calorific value (e.g., a calorific value greater than 4,700 kJ/Nm3), the topgas becomes amenable for conversion into electricity at improved efficiency by burning directly in a Gas Turbine without the need for supplemental fuels. Thus, producing topgas of higher calorific value gives advantage to downstream power production from this topgas.
Operating the BF in the regime of increased oxygen content in the blast, together with increased coal injection, shows benefits of:
This Example illustrates modifying conventional blast furnace operation to cold (ambient temperature) blast operation. The operating parameters for a conventional blast furnace operated to achieve high rate of coal injection with high hot blast temperature and oxygen enrichment to drive it to the lowest practical amount of coke in the charge for stable operation and are shown in column (a) of Table 2 shown below (e.g., the hot blast temperature is 1250° C.; the coal injection rate is 240 Kg/T; the elevated temperature blast is enriched with oxygen to the level of 33.5%; and the coke rate is 262 Kg/T [base case (a) of Table 2 corresponds approximately to case (d) of Table 1]). The computer model described in Example A is also used in Example B.
One constraint to any modified Blast Furnace operation is satisfying the thermal requirements in the lower part of the furnace indicated as the Raceway Adiabatic Flame Temperature (RAFT). The RAFT preferably falls within a range of about 1950 to 2300° C. when the conventional operating parameters are being satisfied.
Case (b) in Table 2 shows the results from operating the conventional blast furnace of case (a), with the following modifications:
i.) increased coal injection,
ii.) increased air blast oxygen, and
iii.) blast temperature reduced to ambient (25° C.)
while satisfying the thermal conditions in the lower part of the furnace (as illustrated by a calculated RAFT of 1996° C.). In this case (b), the Blast Furnace is operated with an ambient temperature blast that is enriched to 55.5% oxygen with the same coke rate as in the base case (a) when the coal injection rate is 335 Kg/T.
Case (b) illustrates operation of the blast furnace wherein:
The previously identified computer model is used to illustrate other modified operating schemes and arrangements for the Blast Furnace of case (a). Case (c) illustrates the affects to furnace operation if some of the topgas is subjected to a CO2 stripping operation, and the remaining CO/H2-enriched topgas stream is recycled and reinjected into the blast furnace through the tuyeres along with the oxygen-enriched ambient temperature air. In case (c), 46 Nm3/T of CO2-stripped and recycled topgas is prepared and injected through the Blast Furnace tuyeres along with the required oxygen-enriched cold blast for a balance operation. The results for this example case (c) in Table 2 show that:
iv.) there is a relatively small production increase from 8990 to 9010 T/day.
Case (d) illustrates a modified blast furnace operation wherein 002 is stripped and recycled topgas is injected at the rate of 73 Nm3/T to the mid-stack region of the furnace. Mid-stack injection of additional reducing gases is used in order to enhance the reducing potential in that region of the furnace. The results of this operational case (d) reveal no benefit over case (b) in terms of coke savings or topgas thermal energy production. There is a production increase from 8,990 to 9,407 T/day.
Case (e) illustrates a modified blast furnace wherein the quantity of mid-stack injected recycle gas was doubled in comparison to case (d). The results of case (e) are:
Case (f) illustrates a modified blast furnace wherein the mid-stack injection of stripped and recycled topgas is increased to the rate of 216 Nm3/T. The results of case (f) are:
Case (g) illustrates a modified blast furnace wherein 100% O2 is used as the cold blast.
Case (g) employs CO2 removal from the topgas and recycle/reinjection of some of the CO2-stripped topgas to the bosh of the furnace and some of the CO2-stripped topgas to the mid-stack region of the furnace. The results of case (g) are:
Case (h) illustrates a modified blast furnace that uses 100% cold blast injection without recycling of CO2-stripped topgas to the tuyeres. This scheme cannot be employed because the RAFT is unacceptable.
Example B illustrates that case (b) has the affect of:
Example C illustrates the affect of blast furnace process changes on the ability to produce power. A nominally-sized 2.3-million-ton-per-year Blast Furnace is operated according to the parameters shown in case (a) of Table 3—shown below (e.g., a coal injection at the rate of 150 Kg/T, a hot blast enriched with oxygen to the level of 26.6% by volume, and a corresponding coke rate of 339 Kg/T). Cases (b), (c), and (d) illustrate the affects which occur within this particular operation as the percentage of oxygen in the blast is increased from 26.6% to the progressively higher percentages of 33.3, 40, and 61%. These affects include:
This Example illustrates an affect of a threefold increase in the amount of energy available for power production by raising the oxygen level in the air blast from 26.6% to 61% for this example Blast Furnace.
Referring now to Table 3, Table 3 illustrates the amount of “Net Power” (in kWe) that is produced for each of the Blast Furnace operational cases. For each of the Blast Furnace operating cases, the topgas is used in power production by one of two methods:
Table 3 illustrates that the amount of electrical power that is generated raises dramatically as the Blast Furnace is additionally oxygen enriched, and a higher calorific value topgas is produced. Table 3 also illustrates the desirability of using combined cycle power production in order to increase the efficiency and raise the total amount of power than can be generated at each of the given blast furnace cases wherein the:
While this example shows Blast Furnace operation and power generation efficiency at four specifically chosen points (or set of operating parameters), it is to be understood that a Blast Furnace can be operated at any suitable point along the disclosed range of oxygen concentration. For example, it might be desirable to operate at 52% oxygen if the projected quantity and calorific value of the topgas is most suitably matched to commercial availability of a specifically-sized gas turbine.
While the invention has been described in certain aspects, it is understood that the invention is not limited to such aspects and the invention covers various modifications and equivalents included within the scope of the appended claims.
This application is a continuation in part of application Ser. No. 12/329,010, filed on Dec. 5, 2008; the disclosure of which is hereby incorporated by reference. Application Ser. No. 12/329,010 claims the benefit of Provisional Application No. 60/992,754, filed Dec. 6, 2007, and No. 61/086,237, filed on Aug. 5, 2008. The disclosure of these provisional applications is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61086237 | Aug 2008 | US | |
| 60992754 | Dec 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12329010 | Dec 2008 | US |
| Child | 12630256 | US |
