AU2012228448B2

AU2012228448B2 - Metallurgical plant with efficient waste-heat utilization

Info

Publication number: AU2012228448B2
Application number: AU2012228448A
Authority: AU
Inventors: Robert Millner; Gerald Rosenfellner
Original assignee: Primetals Technologies Austria GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 2011-03-17
Filing date: 2012-03-08
Publication date: 2016-08-25
Anticipated expiration: 2032-03-08
Also published as: CN103842759B; UA113509C2; ZA201306954B; CN103842759A; RU2610999C2; US20140000535A1; RU2013146337A; AT511243A1; WO2012123320A1; AU2012228448A1; CA2830210A1; BR112013023472A2; AT511243B1; KR20140019389A

Abstract

A metallurgical plant has a plant (7) positioned upstream of a steel-generating plant (8) in the production process for steel and has a gas-generating plant (1) which generates an export gas (2). Carbon dioxide and/or water contained in the export gas (2) is at least partially removed from the export gas (2) in a separation device (3). A resulting product gas (4) is heated, before being supplied to the upstream plant (7), in a firing unit (6) through the combustion of a heating gas (11). The heating gas (11) is supplied to the firing unit (6) in quantities significantly greater than those required for heating the product gas (4). That thermal energy which is produced during the combustion of the heating gas (11) and which is not used for heating the product gas (4) is thermally utilized. The utilization may take place within the firing unit (6) through steam generation and/or downstream of the firing unit (6) in relation to the gas flow of the flue gas (12) produced during the combustion of the heating gas (11). In the latter case, the utilization may take place through pre-heating of the heating gas (11) and/or through pre-heating of an oxidation gas (10) used for the combustion of the heating gas (11) and/or through the pre-heating and/or drying of raw materials (20, 21) to be supplied to the upstream plant (7) and/or to the gas-generating plant (1).

Description

Metallurgical plant with efficient waste-heat utilization

The present invention relates to an operating method for a metallurgical plant that has a plant disposed upstream of a steelmaking plant in the production process for steel and a gas-generating plant which generates an export gas, - wherein carbon dioxide and/or water contained in the export gas are/is at least partially removed from the export gas in a separation device and a product gas resulting thereby is heated in a firing device through combustion of a heating gas before being supplied to the upstream plant.

The present invention further relates to a metallurgical plant which is embodied in such a way that it performs an operating method of the aforesaid kind during live operation.

Metallurgical plants and the associated operating methods are generally known.

In metallurgical plants, in particular in plants in the iron-and steelmaking industry, there is a requirement for large amounts of thermal energy at high temperatures. Large amounts of waste heat therefore accumulate in plants of said kind.

Part of the waste heat being generated is already utilized for preheating intermediate products - in particular process gases - accumulating or to be processed inside the metallurgical plant. Part of the waste heat is also utilized already for driving an electric generator in addition to a downstream turbine by way of a steam-generating device.

It is an object of the present invention to improve an operating method of a metallurgical plant and to provide an improved metallurgical plant. A preferred embodiment aims to provide possibilities for more efficient utilization of a metallurgical plant of the type cited in the introduction.

According to a first aspect, there is provided an operating method for a metallurgical plant that has a plant disposed upstream of a steelmaking plant in the production process for steel and a gas-generating plant which generates an export gas, wherein carbon dioxide and/or water contained in the export gas are/is at least partially removed from the export gas in a separation device and a product gas resulting thereby is heated in a firing device through combustion of a heating gas before being supplied to the upstream plant, wherein the heating gas is supplied to the firing device in quantities significantly greater than are required for heating the product gas, wherein the thermal energy produced during the combustion of the heating gas, insofar as it is not used for heating the product gas, is thermally utilized within the firing device for steam generation and/or in relation to the gas flow of the flue gas produced during the combustion of the heating gas downstream of the firing device for preheating the heating gas and/or for preheating an oxidation gas used for the combustion of the heating gas and/or for preheating and/or drying raw materials that are to be supplied to the upstream plant and/or to the gas-generating plant.

In a preferred embodiment of the present invention the flue gas resulting during the combustion of the heating gas is used for steam generation in the first instance, and only thereafter for heating the product gas.

In certain cases it is necessary to keep the temperature of the product gas essentially constant at a setpoint temperature. If this is the case and the temperature of the flue gas is too high, cold-blast air may be added to the flue gas after its use for steam generation and before the product gas is heated in order to adjust the temperature of the flue gas heating the product gas.

In a particularly preferred embodiment of the present invention it is provided - that the heating of the product gas may be limited to an intermediate temperature below a reaction temperature required for the use of the product gas in the upstream plant, although the thermal energy necessary for this is generated during the combustion of the heating gas, and - that the heated product gas may be heated up from the intermediate temperature to the reaction temperature by means of a partial oxidation of the product gas.

If the thermal energy of the flue gas is sufficiently great, the thermal energy of the flue gas may be used downstream of the firing device for heating a thermal oil.

Preferably, some of the export gas generated by the gasgenerating plant may be used as heating gas. Alternatively or in addition it is possible to use a process gas produced during the removal of the carbon dioxide and the water from the export gas and enriched with carbon dioxide and water as heating gas. If the said process gas does not burn with sufficient stability or does not contain the necessary thermal energy, a further combustible gas can be mixed with the process gas or the process gas can be incinerated in conjunction with the further combustible gas.

The amount and/or the composition of the accumulating export gas and, associated therewith, also the amount and/or the composition of the accumulating process gas are often subject to severe fluctuations with time. In many cases it may therefore be beneficial to buffer the fraction of the export gas used as heating gas or the process gas in a low-pressure gas accumulator disposed upstream of the firing device.

In many cases a combustible gas is generated during the operation of the upstream plant. At least some of the combustible gas may be mixed with the export gas. Alternatively or in addition the combustible gas can be used as heating gas. In particular the last-cited combustible gas can be added where appropriate to the aforementioned process gas enriched with carbon dioxide and water, or incinerated together with said process gas.

It is furthermore possible for a hot top gas to accumulate during the operation of the upstream plant. In this case it is possible for the thermal energy contained in the top gas to be used for preheating the product gas before the latter is supplied to the firing device and/or for steam generation. Alternatively the hot top gas can be a combustible or a noncombustible gas.

The upstream plant can be embodied for example as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant. The gas-generating plant can be embodied for example as a coal gasification plant or as a metal smelting plant, in particular as an iron melting plant or as a smelting reduction plant.

According to a second aspect, there is provided a metallurgical plant which is embodied in such a way that it performs an operating method as claimed in one of the above embodiments during live operation, said metallurgical plant comprising a steelmaking plant, a plant disposed upstream of the steelmaking plant, a gas-generating plant generating export gas, a separation device for at least partially removing carbon dioxide and/or water contained in the export gas while generating a product gas, a firing device having a line for supplying the product gas from the separation device to the firing device and a line leading into the upstream plant for supplying the product gas heated in the firing device from the firing device to the upstream plant, a line for supplying heating gas to the firing device, a line for supplying oxidation gas to the firing device, wherein at least one from the following group of devices: evaporator inside the firing device for generating steam, heating gas heat exchanger for preheating the heating gas, oxidation gas heat exchanger for preheating the oxidation gas, raw materials processing devices for preheating and/or drying raw materials that are to be supplied to the upstream plant and/or to the gas-generating plant is present.

Further advantages and details will become apparent from the following description of exemplary embodiments taken in conjunction with the drawings, in which: FIG 1 is a schematic diagram representing a metallurgical plant, FIG 2 is a schematic diagram representing a detail of the metallurgical plant from FIG 1, and FIG 3 is a schematic diagram representing a possible embodiment of the metallurgical plant from FIG 1.

According to FIG 1, a metallurgical plant has a gasgenerating plant 1. The gas-generating plant 1 can be embodied for example as a coal gasification plant or as a metal smelting plant. In the case of an embodiment as a metal smelting plant this can be embodied in particular as an iron melting plant - also as a blast furnace, in particular an oxygen blast furnace - or as a smelting reduction plant. An oxygen blast furnace is a blast furnace in which technically pure oxygen is used as hot-blast air and the resulting stack gas can be returned to the blast furnace.

During operation the gas-generating plant 1 generates a gas 2, referred to hereinbelow as export gas 2. The export gas 2 contains combustible components as well as, in addition, carbon dioxide, water and typically also nitrogen. The presence of carbon dioxide and water is indicated in FIG 1 by the suffixes "C02" and "H20" appended to the export gas.

All or part of the export gas 2 is supplied to a separation device 3. The export gas 2 - possibly only the fraction of the export gas 2 supplied to the separation device 3 - is conditioned in the separation device 3. In particular the carbon dioxide contained in the export gas 2 and/or the water contained in the export gas 2 are/is completely or partially removed from the export gas 2 in the separation device 3. This results on the one hand in a product gas 4 in which carbon dioxide and water are depleted in comparison with the export gas 2. This is indicated in FIG 1 by the suffixes "C02-" and "H20—". On the other hand a process gas 5 - often referred to as tail gas - is produced in which carbon dioxide and/or water are enriched. This is indicated in FIG 1 by the suffixes "C02+" and "H20+".

The product gas 4 is initially supplied to a firing device 6 and from there to an upstream plant 7. The upstream plant 7 is a plant which is disposed upstream of a steelmaking plant 8 in the steel production process. The upstream plant 7 can be embodied for example as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant.

In the firing device 6, the product gas 4 is heated in a product gas heat exchanger 9. In the process the chemical composition of the product gas 4 remains - at least substantially - unchanged. Only the temperature of the product gas 4 changes.

When the firing device 6 is fired, a heating gas 11 is incinerated into a flue gas 12 in the firing device 6 using an oxidation gas 10. Both gases 10, 11 are supplied to the firing device 6. The oxidation gas 10 can in particular be normal air.

The heating gas 11 is supplied to the firing device 6 in quantities significantly greater than are required for heating the product gas 4. For this reason a substantial amount of surplus thermal energy accumulates in the firing device 6. Insofar as it is superfluous, i.e. is not needed and utilized for heating the product gas 4, the resulting thermal energy can be used for example for generating steam inside the firing device 6 by means of an evaporator 13 and thus for driving a water-steam circuit. For example, the steam can drive a turbine 14 which in turn drives an electric generator 15. Alternatively, the steam can be utilized for other purposes.

If steam is generated, the evaporator 13 - seen particularly clearly in FIG 2 - is positioned upstream of the product gas heat exchanger 9 in relation to the gas flow of the flue gas 12. The flue gas 12 resulting from the combustion of the heating gas 11 is therefore utilized for steam generation in the first instance, and only thereafter for heating the product gas 4.

Where necessary, the generated steam can also be superheated by means of the flue gas 12. If present, a superheater (not shown in the FIGs) is in this case positioned upstream of the product gas heat exchanger 9, and possibly also the evaporator 13, in relation to the gas flow of the flue gas 12. In addition, the water that is to be vaporized can be preheated. A corresponding preheater (not shown in the FIGs) is in this case disposed downstream of the product gas heat exchanger 9 in relation to the gas flow of the flue gas 12.

Alternatively or in addition to its being utilized for steam generation it is possible for the flue gas 12 to be used in units 16 to 19 which are disposed downstream of the firing device 6 in relation to the gas flow of the flue gas 12.

For example, the heating gas 11 can be preheated in a heating gas heat exchanger 16. Alternatively or in addition to the preheating of the heating gas 11, the oxidation gas 10 can be preheated in an oxidation gas heat exchanger 17. The preheating of the heating gas 11 and/or of the oxidation gas 10 obviously takes place before the said gases 10, 11 are supplied to the firing device 6.

Furthermore - alternatively or in addition to the preheating of the heating gas 11 and/or of the oxidation gas 10 - raw materials 20 that are to be supplied to the upstream plant 7 can be dried and/or preheated in a raw materials processing device 18. Analogously, in addition or alternatively, raw materials 21 that are to be supplied to the gas-generating plant 1 can be dried and/or preheated in a further raw materials processing device 19. Iron ore or metallurgical grade coal in particular are considered suitable raw materials 21.

If surplus thermal energy of the flue gas 12 continues to be available, it is possible in addition to utilize the thermal energy of the flue gas 12 downstream of the firing device 6 in an oil heat exchanger 23 for the purpose of heating a thermal oil 24.

In some cases it can be beneficial to adjust the temperature of the flue gas 12 heating the product gas 4. For this purpose cold-blast air 25 can be added to the flue gas 12 as shown in FIG 2. In this case the admixing of the cold-blast air 25 takes place after the flue gas 12 has been used for steam generation, but - obviously - before the product gas 4 is heated.

It is possible to heat up the product gas 4 in the firing device 6 to a reaction temperature T (of typically in excess of 800°C) that the product gas 4 must attain in order to be able to be used in the upstream plant 7. In many cases, however, it is advantageous to limit the heating of the product gas 4 to an intermediate temperature T' that lies below the reaction temperature T. This applies even though, during the combustion of the heating gas 11, the thermal energy necessary for this (i.e. for heating to the reaction temperature T) is present. The intermediate temperature T' can range from approx. 400°C to approx. 600°C, for example. If the product gas 4 in the firing device 6 is heated only up to the intermediate temperature T', the product gas 4 heated in the firing device 6 as shown in FIG 2 is heated by means of a partial oxidation of the product gas 4 in an oxidation device 26 from the intermediate temperature T' to the reaction temperature T. Normally, for this purpose, an oxidation gas 27, for example technically pure oxygen (oxygen content at least 90%) is supplied to the oxidation device 26 in addition to the product gas 4.

The heating gas 11 incinerated in the firing device 6 can in principle be selected arbitrarily. It is possible to supply the heating gas 11 to the metallurgical plant from outside. Alternatively, the heating gas 11 can be a gas generated within the metallurgical plant. For example, it is possible for some of the export gas 2 generated by the gas-generating plant 1 to be used as heating gas 11 according to FIG 3. Alternatively or in addition it is possible to use the process gas 5 as heating gas 11. If necessary, a further combustible gas 28 can be added to the process gas 5. Alternatively the further combustible gas 28 can, if necessary, be incinerated in a separate burner of the firing device 6 together with the process gas 5.

If part of the export gas 2 or the process gas 5 is used as heating gas 11, a low-pressure gas accumulator 29 is preferably disposed in the supply line of the corresponding gas 2, 5 to the firing device 6. The low-pressure gas accumulator 29 serves to compensate for fluctuations in quantity and/or composition which occur during the generation of the export gas 2 and/or the process gas 5. A gas pressure p which is marginally greater than atmospheric pressure prevails in the low-pressure gas accumulator 29. A gas 30 that is hot and/or combustible is produced in many cases during the operation of the upstream plant 7. This gas 30 is often referred to as top gas 30. If the top gas 30 is combustible, it is possible to admix the top gas 30 - in its entirety or in part - to the export gas 2. Alternatively or in addition it is possible to utilize the top gas 30 as heating gas 11. Where appropriate it can be used in combination with the export gas 2 and/or the process gas 5. In particular the top gas 30 can in this case be identical to that combustible gas 28 which is mixed with the process gas 5 or incinerated together with the latter.

If the top gas 30 is hot, it is possible to utilize the thermal energy contained in the top gas 30 for preheating the product gas 4 before it is supplied to the firing device 6 and/or for steam generation (including superheating, where necessary). This also is indicated by dashed lines in FIG 3.

The present invention has many advantages. In particular an efficient utilization of the thermal energy accumulating in the metallurgical plant and of the accumulating combustible gases is possible in a relatively simple manner. The above description serves only to explain the present invention. The scope of protection of the present invention, on the other hand, shall be determined solely by the appended claims. 1 Gas-generating plant 2 Export gas 3 Separation device 4 Product gas 5 Process gas 6 Firing device 7 Upstream plant 8 Steelmaking plant 9 Product gas heat exchanger 10, 27 Oxidation gases 11 Heating gas 12 Flue gas 13 Evaporator 14 Turbine 15 Generator 16 to 19 Units 16 Heating gas heat exchanger 17 Oxidation gas heat exchanger 18, 19 Raw materials processing devices 20, 21 Raw materials 23 Oil heat exchanger 24 Thermal oil 25 Cold-blast air 26 Oxidation device 28 Further combustible gas 29 Low-pressure gas accumulator 30 Top gas p Gas pressure T Reaction temperature

Claims

Claims

1. An operating method for a metallurgical plant that has a plant disposed upstream of a steelmaking plant in the production process for steel and a gas-generating plant which generates an export gas, - wherein carbon dioxide and/or water contained in the export gas are/is at least partially removed from the export gas in a separation device and a product gas resulting thereby is heated in a firing device through combustion of a heating gas before being supplied to the upstream plant, - wherein the heating gas is supplied to the firing device in quantities significantly greater than are required for heating the product gas, - wherein the thermal energy produced during the combustion of the heating gas, insofar as it is not used for heating the product gas, is thermally utilized within the firing device for steam generation and/or in relation to the gas flow of the flue gas produced during the combustion of the heating gas downstream of the firing device for preheating the heating gas and/or for preheating an oxidation gas used for the combustion of the heating gas and/or for preheating and/or drying raw materials that are to be supplied to the upstream plant and/or to the gasgenerating plant.
2. The operating method as claimed in claim 1, wherein the flue gas resulting from the combustion of the heating gas is utilized for steam generation in the first instance, and only thereafter for heating the product gas.
3. The operating method as claimed in claim 2, wherein cold-blast air is added to the flue gas after its use for steam generation and before the product gas is heated in order to adjust the temperature of the flue gas heating the product gas.
4. The operating method as claimed in any one of claims 1, 2 or 3, wherein - the heating of the product gas is limited to an intermediate temperature below a reaction temperature required for the use of the product gas in the upstream plant, although the thermal energy necessary for this is generated during the combustion of the heating gas, and - the heated product gas is heated up from the intermediate temperature to the reaction temperature by means of a partial oxidation of the product gas.
5. The operating method as claimed in any one of the above claims, wherein the thermal energy of the flue gas downstream of the firing device is used for heating a thermal oil.
6. The operating method as claimed in any one of the above claims, wherein some of the export gas generated by the gas-generating plant and/or a process gas produced during the removal of the carbon dioxide and the water from the export gas and enriched with carbon dioxide and water - the process gas possibly being mixed with a further combustible gas or being incinerated in conjunction with the further combustible gas - is used as heating gas.
7. The operating method as claimed in claim 6, wherein the fraction of the export gas used as heating gas or the process gas is buffered in a low-pressure gas accumulator disposed upstream of the firing device .
8. The operating method as claimed in any one of the above claims, wherein a combustible top gas accumulates during the operation of the upstream plant and in that at least some of the combustible top gas is admixed to the export gas (2) and/or used as heating gas.
9. The operating method as claimed in any one of claims 1 to 7, wherein a hot top gas accumulates during the operation of the upstream plant and in that the thermal energy contained in the top gas is used for preheating the product gas before it is supplied to the firing device and/or for steam generation.
10. The operating method as claimed in any one of the above claims, wherein the upstream plant is embodied as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant.
11. The operating method as claimed in any one of the above claims, wherein the gas-generating plant is embodied as a coal gasification plant or as a metal smelting plant, in particular as an iron melting plant or as a smelting reduction plant.
12. A metallurgical plant which is embodied in such a way that it performs an operating method as claimed in any one of the above claims during live operation, said metallurgical plant comprising - a steelmaking plant, - a plant disposed upstream of the steelmaking plant Г - a gas-generating plant generating export gas, - a separation device for at least partially removing carbon dioxide and/or water contained in the export gas while generating a product gas , - a firing device having a line for supplying the product gas from the separation device to the firing device and a line leading into the upstream plant for supplying the product gas heated in the firing device from the firing device to the upstream plant, - a line for supplying heating gas to the firing device, - a line for supplying oxidation gas to the firing device, wherein at least one from the following group of devices: - evaporator inside the firing device for generating steam, - heating gas heat exchanger for preheating the heating gas, - oxidation gas heat exchanger for preheating the oxidation gas, - raw materials processing devices for preheating and/or drying raw materials that are to be supplied to the upstream plant and/or to the gas- generating plant is present.
13. The metallurgical plant as claimed in claim 12, wherein a line for supplying cold-blast air to flue gas is present.
14. The metallurgical plant as claimed in any one of claims 12 or 13, wherein a low-pressure gas accumulator for buffering the export gas or the process gas is present, the low-pressure gas accumulator being disposed upstream of the firing device.
15. The metallurgical plant as claimed in any one of claims 12 to 14, wherein the upstream plant is a blast furnace, a smelting reduction plant, a smelter unit or a direct reduction plant.
16. The metallurgical plant as claimed in any one of claims 12 to 15, wherein the gas-generating plant is a coal gasification plant, a metal smelting plant, in particular an iron melting plant or a smelting reduction plant.