Method for operating a direct reduction plant and corresponding direct reduction plant

Abstract

The invention relates to a method for operating a direct reduction plant (10) comprising: a reactor (12) for the direct reduction of the iron ore in a reduction zone formed in the interior of the reactor; and a line system (40), which has a first line path (38) for introducing at least one gas, in particular process gas for the direct reduction, into the reduction zone of the reactor (12), wherein a compressor (50) for compressing the at least one gas is fluidically connected in said line path (38). According to the invention, at least three gases can be introduced into the interior of the reactor (12) by means of the first line path (38) with the compressor (50) connected therein, and one of the gases is metered, as an additional gas, to at least one other gas upstream of the compressor (50) in order to adapt the gas properties of the resulting gas mixture. The invention also relates to a computer program product comprising commands which, when executed by a processor, cause the processor to carry out such a method, and to a corresponding direct reduction plant (10).

Description

[0001] Method for operating a direct reduction plant and corresponding direct reduction plant

[0002] The invention relates to a method for operating a direct reduction plant, which comprises a reactor for the direct reduction of iron ore in a reduction zone formed inside it and a piping system, which has a first piping path for introducing at least one gas, in particular process gas for the direct reduction, into the reduction zone of the reactor, wherein a compressor for compressing the at least one gas is fluidically connected in this piping path.

[0003] The invention further relates to a direct reduction plant for the production of sponge iron from iron ore-containing material, comprising a reactor for the direct reduction of the iron ore in a reduction zone formed inside it and a piping system which has a first piping path for introducing at least one gas, in particular process gases for the direct reduction, into the reduction zone of the reactor, wherein a compressor for compressing the at least one gas is fluidically connected in this piping path.

[0004] The production of sponge iron in the reactor of the direct reduction plant comprises two basic steps: In a first step, the iron ore is reduced to sponge iron in one or more reduction zones using a suitable hot reducing gas. In a subsequent second step, the produced sponge iron is cooled to significantly lower temperatures in a cooling zone using a cooling gas.

[0005] The operation of the direct reduction plant requires at least one process gas, which is supplied via a piping system either to the reduction zone of the reactor or to a unit upstream of the reactor to provide the reactor interior with a reducing gas. This process gas is, for example, natural gas or methane (CH4). If the supplied process gas does not itself function as a reducing gas (as in the case of natural gas / methane), it is first reformed to become the reducing gas. This can take place in-situ within the reactor or in a reformer as an upstream unit. In the case of methane, the reforming results in a reducing gas composed of hydrogen (H2) and carbon monoxide (CO).

[0006] In the reactor's reduction zone, the reducing gas is exposed to temperatures ranging from 850 °C to 1100 °C. As mentioned previously, the process gas methane (CH4) in combination with oxygen (O2) is often used as the basis for the formation of the reducing gas. This gas reacts with hydrogen and carbon monoxide, as well as carbon dioxide (CO2) and water (H2O), through a catalytic process in the reduction zone or as a preliminary process. The carbon monoxide causes a slight carburization of the sponge iron. The carbon content in the sponge iron can thus reach approximately 1 to 1.5 wt%. By using methane as a cooling gas in the cooling zone, the sponge iron can be further carburized, so that it can have a carbon content of up to 6 wt% when it leaves the cooling zone.

[0007] Document WO 2022 / 271064 A describes a method for operating a direct reduction plant comprising a reactor for the direct reduction of iron ore in a reduction zone formed within it and a piping system. This system includes a first piping path for introducing a process gas for direct reduction, namely hydrogen (H2) from a gas source, into the reactor's reduction zone. A compressor for compressing the gas is fluidically integrated into this first piping path. In this case, this is a hydrogen compressor specifically designed for the gas properties of hydrogen.

[0008] In the gradual conversion of steel production to low-CO2 or CO2-neutral production, it is often planned that a direct reduction plant will initially be operated with hydrocarbon gas and then later with increasing amounts of hydrogen as the process gas. However, for a corresponding direct reduction plant that is intended to be operable with both a primary process gas, such as hydrogen, and another process gas, such as natural gas / methane, the problem arises that the compressor can only be designed for one of these two gases.

[0009] The underlying problem will be illustrated here using the combination of the process gases hydrogen and natural gas / methane. In the field of (gas) compressors, a fundamental distinction is made between turbo compressors, i.e., turbomachines, and piston compressors, i.e., positive displacement machines. Comparing the basic properties of natural gas / methane and hydrogen, the differences in density and, in particular, the differences in sound velocity are striking. Compressing hydrogen with a turbo compressor designed for natural gas / methane is only possible if the sound velocity triangles at the impeller inlet and outlet remain the same (keyword: Mach similarity). For pure hydrogen, therefore, a four times greater flow rate and a four times higher rotational speed (peripheral velocity) would be required. This is hardly achievable with conventional turbo compressors.For this reason, piston compressors are favored when increasing the pressure of hydrogen. Compared to turbo compressors, the compression principle of piston compressors allows for operation that is almost independent of the pumped medium. Nevertheless, when switching to a different pumped medium, the compressor, pulsation dampers, and the piping or storage system are confronted with entirely different material properties. These have a significant influence on the pulsation behavior of the entire system and can therefore lead to altered vibration behavior, which causes problems.

[0010] The simplest solution involves connecting two compressors in parallel within the piping system, one designed for the first process gas (e.g., hydrogen) and the other for the second process gas (e.g., natural gas / methane). This simple solution is suitable if the system only switches between operation with one process gas and operation with the other. However, switching between process gases leads to process fluctuations due to different operating points in the reactor. For variable mixed operation, i.e., operation in which both process gases are used in a selectable composition, the two compressors must be precisely matched, which proves difficult in practice.

[0011] The object of the invention is to provide a method, a computer program product, and a direct reduction plant for the production of sponge iron by direct reduction, which overcomes the aforementioned difficulties in a comparatively simple manner. According to the invention, this object is achieved by the features of the independent claims. Preferred embodiments of the invention are specified in the dependent claims, each of which, individually or in combination, may represent an aspect of the invention.

[0012] In the inventive method for operating a direct reduction plant, which comprises a reactor for the direct reduction of iron ore in a reduction zone formed inside it and a piping system which has a first piping path for introducing at least one gas, in particular process gas for the direct reduction, into the reduction zone of the reactor, wherein a compressor for compressing the at least one gas is fluidically connected in this piping path, it is provided that at least three gases can be introduced into the interior of the reactor via the first piping path with the compressor connected therein and one of the gases is metered as an additive gas to at least one other gas upstream of the compressor to adjust the gas properties of the resulting gas mixture.By adding the additional gas to one of the other gases, the gas properties of the resulting gas mixture can be adapted to the gas properties of one of the other gases for which the compressor is actually designed.

[0013] The term "piping path" describes a route through the piping system, or a part of the piping system, that the gas takes during operation. In the case of the first piping path for introducing the gas(es) into the reactor's reduction zone, this is a path pointing towards the reactor's reduction zone. It is generally unbranched and therefore unambiguous, and it terminates in the reduction zone. Terms such as "upstream," "can be introduced / introduced via the first piping path with the compressor connected within it," "terminate," etc., then refer to this direction.

[0014] According to a preferred embodiment of the method according to the invention, the other gases, or at least two of the other gases, are process gases. The additional gas is mixed with one or both process gases (first process gas) so that the gas properties of the resulting gas mixture are adapted to the gas properties of the other process gas (second process gas) for which the compressor is actually designed. Furthermore, it is preferably provided that

[0015] (i) the additive gas that can be selectively mixed contains no or only an insignificant proportion of hydrogen, in particular CO2, CO or a blast furnace gas,

[0016] (ii) one of the other gases is hydrogen (H2) or consists substantially of hydrogen (H2),

[0017] (iii) a second of the other gases also contains no or only an insignificant proportion of molecular hydrogen, in particular natural gas and

[0018] (iv) the compressor is designed for the second of the other gases. In this case, molecular hydrogen is the first process gas. The second process gas is then, for example, natural gas or methane. The additive gas that can be selectively mixed is preferably a gas that is readily available in connection with a metallurgical process.

[0019] According to a further preferred embodiment of the method according to the invention, the compressor connected in the first line path is a turbo compressor, in particular a turbo compressor. A compressor of this type can be well designed for a process gas such as natural gas / methane.

[0020] According to yet another preferred embodiment of the method according to the invention, the addition of the supplementary gas is carried out by control or regulation, wherein, in addition to the aim of adapting the gas properties of the resulting gas mixture to the gas properties of the / another process gas for which the compressor is actually designed, preferably at least one of the following objectives is also pursued:

[0021] Adjusting the gas flow rate through the first pipeline path and / or

[0022] Setting a reduction potential that is as equivalent as possible to operation with the process gas for which the compressor is actually designed.

[0023] The invention further relates to a computer program product comprising instructions which, when executed by a processor of a control and / or regulating device, cause the latter to execute a aforementioned method. The computer program product controls, in particular, the addition of the additive gas. In the direct reduction plant according to the invention for the production of sponge iron from iron ore-containing material, comprising a reactor for the direct reduction of the iron ore in a reduction zone formed within it and a piping system having a first piping path for introducing at least one gas, in particular process gases for direct reduction, into the reduction zone of the reactor, wherein a compressor for compressing the at least one gas is fluidically connected in this piping path, it is provided that the piping system

[0024] (a) is designed in such a way that at least three gases can be introduced into the interior of the reactor via the first conduit path with the compressor connected therein, and

[0025] (b) The device comprises means for metered addition of one of the gases as an additive gas to at least one other of the gases upstream of the compressor in order to adjust the gas properties of the resulting gas mixture. By adding the additive gas to at least one of the other gases using said means, the gas properties of the resulting gas mixture can be adapted to the gas properties of one or more of the other gases for which the compressor is actually designed. The direct reduction plant is, in particular, a plant for carrying out the aforementioned process.

[0026] According to a preferred embodiment of the direct reduction plant according to the invention, the piping system comprises at least two gas supply lines to which corresponding gas sources for providing the gases can be connected, and which all lead into the first piping path upstream of the compressor. One of the gas supply lines is connectable to / connected to the gas source for the auxiliary gas, and the at least one further gas supply line is connected to the gas sources for the other gases.

[0027] According to a further preferred embodiment of the direct reduction plant according to the invention, the means for metered mixing of the additive gas with at least one of the other gases comprises a fitting for selectively changing the gas flow of the additive gas through the corresponding gas supply line. The fitting is fluidically connected in this corresponding gas supply line. It is also preferably provided with regard to the direct reduction plant according to the invention that

[0028] (i) the additive gas that can be selectively mixed contains no or only an insignificant proportion of hydrogen, in particular CO2, CO or a blast furnace gas,

[0029] (ii) one of the other gases is hydrogen or consists substantially of hydrogen,

[0030] (iii) a second of the other gases also contains no or only an insignificant proportion of molecular hydrogen, in particular natural gas and

[0031] (iv) the compressor is designed for the second of the other gases. In this case, molecular hydrogen is the first process gas. The second process gas is then, for example, natural gas or methane. The additive gas that can be selectively mixed is preferably a gas that is readily available in connection with the metallurgical process.

[0032] According to a further preferred embodiment of the invention, the direct reduction plant has a cooling circuit via which a cooling zone downstream of the reduction zone inside the reactor can be supplied with cooling gas or a cooling gas mixture.

[0033] According to a further preferred embodiment of the invention, the direct reduction system comprises a control and / or regulating device for controlling / regulating the means for metered mixing of one of the gases as an additive gas to at least one other gas upstream of the compressor. If regulation is provided, it can, for example, be based on the partial pressure ratios of the other gases. The control and / or regulating device is preferably computer-based and includes a processor.

[0034] In particular, it is intended that the control and / or regulating device is designed in such a way that, in addition to the goal of adapting the gas properties of the resulting gas mixture to the gas properties of another process gas for which the compressor is actually designed, at least one of the following goals can also be pursued:

[0035] Adjusting the gas flow rate through the first line path and / or setting a reduction potential as equivalent as possible to operation with the process gas for which the compressor is actually designed.

[0036] According to a further preferred embodiment of the direct reduction system according to the invention, the compressor connected in the first line path is a turbo compressor, in particular a turbo compressor. A compressor of this type is well suited for process gases such as natural gas / methane.

[0037] The invention is explained below by way of example with reference to the accompanying drawing, using a preferred embodiment as an example, wherein the features shown below can represent an aspect of the invention, either individually or in combination. It shows:

[0038] Fig. 1 shows a direct reduction plant according to a preferred embodiment of the invention.

[0039] Figure 1 shows a direct reduction plant 10 in an exemplary, schematic representation. The direct reduction plant 10 is used for the production of direct reduced iron (DRI) and comprises a reactor 12 for the actual reaction, i.e., the direct reduction, and a feeding device 14 for feeding iron ore-containing material (arrow 16) into the reactor 12, this material being in bulk form. In the example shown, the feeding device 14 is arranged above the reactor 12 and has a locking device 18, which is connected to an associated feed inlet 20 into the reactor 12. The locking device 18 serves to introduce the bulk material into the reactor 12 in a gas-tight manner. The reactor 12 shown for the direct reduction is of the shaft furnace type, which is filled from above with the starting material containing the iron ore (arrow 16).

[0040] Reactor 12 extends vertically from a top surface 22 along its central longitudinal axis 24 to a lower end 26. It has a reactor vessel 28, in the interior of which—that is, the interior of reactor 12—the corresponding reactions take place. In an upper part 30 of reactor 12, there is a reduction zone where the iron is reduced from the iron ore, and in a lower part 32 of reactor 12, there is a cooling zone where the resulting sponge iron can be cooled / is cooled. The lower part 32 of reactor 12 is conically shaped and converges at the lower end 26 into an outlet 34 for the either still hot or cold sponge iron, which can be removed from reactor 12 there (arrow 36).

[0041] The direct reduction unit 10 has the following function: The iron ore-containing material (arrow 16) is fed into the reactor 12 via the airlock 18. The individual particles of the material fed in this way sink through the reduction zone of the reactor 12 and react at high temperature (850 °C to 1100 °C) in countercurrent contact with a reducing gas, which typically contains carbon monoxide (CO) and / or hydrogen (H2). This reducing gas is generated in situ in the reactor 12 from supplied process gas (for example, natural gas / methane, methanol, or ammonia). The process gas for the formation of this reducing gas is introduced into the reactor 12 via a first piping path 38 of a piping system 40, which opens into the lower part of the reduction zone located in the upper part 30 of the reactor 12.The direct reduction plant 10 shown in this example is suitable for the in-situ reforming of the process gas used to produce the reducing gas required for the reduction process in reactor 12. In other words, a process gas that cannot be used directly as a reducing gas can still be introduced directly into the reactor, since the reforming of the process gas to the reducing gas in reactor 12 takes place in-situ using provided catalyst material. A reforming unit connected in the piping system 40 (not shown) is therefore unnecessary.

[0042] On the other hand, gas is withdrawn from the interior of reactor 12 at an outlet in the upper part of the reduction zone via a second line path 42 of the piping system 40. A significant portion of this withdrawn gas retains its reducing potential and is then returned to the inlet of reactor 16 via the first line path 38 in a circuit formed by the piping system 40. A CO2 scrubber 44 is installed in this circuit, which extracts pure carbon dioxide from the piping system 40 of the direct reduction device 12 and discharges it in an exhaust gas stream 46. A heating device 48 is connected in a section of the first line path 38, which lies within the circuit formed by the piping system 40. This heating device brings the mixture of process gas and recirculated gas to the operating temperature for the reduction process in reactor 12.

[0043] In the first conduit path 38 of the conduit system 40, a compressor 50 is connected upstream of the circuit. The conduit system 40 is designed such that at least three gases can be introduced into the interior of the reactor 12 via the first conduit path 38 and the compressor 50 connected therein. For this purpose, the conduit system 40 has at least two gas supply lines 52, 54, to which corresponding gas sources 56, 58, 60 can be connected to supply the gases, and which all open into the first conduit path 38 upstream of the compressor 50. One of the gas supply lines (the first gas supply line) 52 is intended for connection to a gas source 56, the gas from which is intended as a mixing gas to at least one of the other gases in order to adapt the gas properties of the resulting gas mixture to the design of the compressor 50. Accordingly, the mixing takes place upstream of compressor 50.The other gas in question is, in this example, the process gas or reducing gas hydrogen (H2). Compressor 50 is preferably designed for the second other gas, which in this example is the process gas methane (CH4). The additional gas is then, for example, carbon dioxide (CO2), which is supplied – at least partially – from the exhaust gas stream 46.

[0044] For the metered addition of the additive gas to the other gas (in this example, H2), a fitting 62 is installed in the first gas supply line 52 to selectively change the flow of the additive gas through the first gas supply line 52. The combination of gas supply line 52 and fitting 62 thus serves as a means 64 for metered addition of the additive gas to at least one of the other gases upstream of the compressor 50. The fitting 62 is preferably a metering valve 66. This metering valve 66 of the means 64 for metered addition of the additive gas is then controlled by a control and / or regulating device 68. This device 68 is therefore a control and / or regulating device 68 for controlling or regulating the means 64 for metered addition of one of the gases as an additive gas to at least one of the other gases in the first line path 38 upstream of the compressor 50.

[0045] To establish a control loop for the corresponding control system, at least one measuring unit (not shown here) for measuring a controlled variable is arranged in the piping system 40 and / or in the reactor 12. This measuring unit is then connected to the control and / or regulating device 68 via a signal. In this way, the controlled variable can be fed back to the control and / or regulating device 68 and compared there with a reference variable (control loop). The measuring unit is, for example, a flow meter for measuring the gas flow through the first piping path 38.

[0046] The cooling zone is located in the lower part 32 of the reactor 12. This lower part 32 is preferably conical in shape and converges to the outlet 34, through which the already reduced ore, i.e., the sponge iron or DRI, is discharged hot or cold. In the cooling zone of the lower part 32 of the reactor 12, a cooling gas stream (containing any non-oxidizing, inert, or reducing gas, for example, natural gas) is normally circulated countercurrently to, among other things, extract heat from the hot sponge iron / DRI. This cooling gas is introduced through a cooling gas line 70 into a lower section of the conical lower part 32 of the reactor 12 and, heated, is removed from an upper section of the lower part 32 of the reactor 12 through another cooling gas line 72 and then returned in a closed loop to line 70.In this resulting cooling circuit 74, the hot gas is purified and cooled before being reintroduced into reactor 12. For this purpose, cooling circuit 74 includes a cooler 76 and a compressor 78. If it is desired to discharge the sponge iron / DRI at high temperature, cooling circuit 74 is switched off, and the DRI undergoes no active cooling before being discharged from reactor 12 via outlet 34, for example, for hot coupling to the electric arc furnace (EAF).

[0047] Reference sign

[0048] 10 Direct Reduction Plant

[0049] 12 Reactor

[0050] 14 Feeding device

[0051] 16 Arrow (material containing iron ore)

[0052] 18 Lock equipment

[0053] 20 Feed access

[0054] 22 Top side (reactor)

[0055] 24 Longitudinal axis (reactor)

[0056] 26 lower end (reactor)

[0057] 28 reactor vessels

[0058] 30 upper part

[0059] 32 lower part

[0060] 34 Outlet

[0061] 36 Arrow (Iron sponge)

[0062] 38 first line path

[0063] 40 piping system

[0064] 42 second line path

[0065] 44 CO2 scrubbers

[0066] 46 Exhaust gas flow

[0067] 48 Heating system

[0068] 50 Compressor

[0069] 52, 54 Gas supply line

[0070] 56 Gas source (additional gas)

[0071] 58 Gas source (other gas: hydrogen)

[0072] 60 Gas source (other gas: methane)

[0073] 62 fitting

[0074] 64 means

[0075] 66 Metering valve

[0076] 68 Control and / or regulating device

[0077] 70 Cooling gas line

[0078] 62 additional cooling gas lines

[0079] 70 coolers

[0080] 72 Compressor (cooling circuit)

Claims

Patent claims 1. Method for operating a direct reduction plant (10) comprising a reactor (12) for the direct reduction of iron ore in a reduction zone formed inside it and a piping system (40) which has a first piping path (38) for introducing at least one gas, in particular process gas for the direct reduction, into the reduction zone of the reactor (12), wherein a compressor (50) for compressing the at least one gas is fluidically connected in this piping path (38), characterized in that at least three gases can be introduced into the interior of the reactor (12) via the first piping path (38) with the compressor (50) connected therein, and one of the gases is metered as an additive gas to at least one other of the gases upstream of the compressor (50) to adjust the gas properties of the resulting gas mixture.

2. The method according to claim 1, characterized in that the other gases or at least two of the other gases are process gases.

3. Method according to claim 1 or 2, characterized in that (i) the additive gas that can be selectively mixed contains no or only an insignificant proportion of hydrogen, in particular CO2, CO or a blast furnace gas, (ii) one of the other gases is molecular hydrogen or consists substantially of molecular hydrogen, (iii) a second of the other gases also contains no or only an insignificant proportion of molecular hydrogen, in particular natural gas and (iv) the compressor (50) is a compressor (50) designed for the second of the other gases.

4. Method according to one of claims 1 to 3, characterized in that the compressor (50) connected in the first line path (38) is a compressor (50) of the type turbo machine, in particular a turbo compressor.

5. Method according to one of claims 1 to 4, characterized in that the addition of the supplementary gas is carried out by control or regulation, wherein the control / regulation preferably also pursues at least one of the following objectives. becomes: Adjusting the gas flow rate through the first pipeline path (38) and / or Setting a reduction potential as equivalent as possible to operation with the process gas for which the compressor (50) is actually designed.

6. Computer program product comprising instructions which, when executed by a processor of a control and / or regulating device (68), cause it to execute a method according to any one of claims 1 to 5.

7. Direct reduction plant (10) for the production of sponge iron from iron ore-containing material, comprising a reactor (12) for the direct reduction of the iron ore in a reduction zone formed inside it and a piping system (40) which has a first piping path (38) for introducing at least one gas, in particular process gases for the direct reduction, into the reduction zone of the reactor (12), wherein a compressor (50) for compressing the at least one gas is fluidically connected in this first piping path (38), characterized in that the piping system (40) is designed such that at least three gases can be introduced into the interior of the reactor (12) via the first piping path (38) with the compressor (50) connected therein, and Means (64) for metered addition of one of the gases as an additive gas to at least one other of the gases upstream of the compressor (50) to adjust the gas properties of the resulting gas mixture.

8. Direct reduction plant according to claim 7, characterized in that the piping system (40) has at least two gas supply lines (52, 54) which can be connected to corresponding gas sources (56, 58, 60) for providing the gases and which all lead into the first piping path (38) before the compressor (50).

9. Direct reduction plant according to claim 7 or 8, characterized in that the means (64) for metered addition of the additive gas to at least one of the other gases includes a fitting (62) for targeted modification of the gas flow of the Additional gas is supplied through the corresponding gas supply line (52).

10. Direct reduction plant according to one of claims 7 to 9, characterized in that the additive gas that can be selectively mixed has no or only an insignificant proportion of hydrogen, in particular CO2, CO or a blast furnace gas, a first of the other gases is hydrogen or consists substantially of hydrogen, a second of the other gases also has no or only an insignificant proportion of molecular hydrogen, in particular is natural gas and the compressor (50) is a compressor designed for the second of the other gases. 1 1 . Direct reduction plant according to one of claims 7 to 10, characterized by a control and / or regulating device (68) for controlling / regulating the means (64) for metered mixing of one of the gases as an additive gas to at least one other of the gases upstream of the compressor (50).

12. Direct reduction plant according to claim 1 1 , characterized in that the control and / or regulating device (68) is configured such that, in addition to the objective of adapting the gas properties of the resulting gas mixture to the gas properties of the / another process gas for which the compressor (50) is actually designed, at least one of the following further objectives can also be pursued: - Adjusting the gas flow rate through the first pipeline path (38) and / or - Setting a reduction potential as equivalent as possible to operation with the process gas for which the compressor (50) is actually designed.

13. Direct reduction plant according to one of claims 7 to 12, characterized in that the compressor (50) connected in the first line path (38) is a compressor (50) of the type turbo machine, in particular a turbo compressor.

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