Coke Oven Plant Operation Method

Abstract

(a) providing a blast furnace gas stream (B) and a coke oven gas stream (C); (b) treating a portion (B1) of the blast furnace gas stream (B) in a CO conversion unit (30) to obtain a treated blast furnace gas stream; (c) subjecting the treated blast furnace gas stream to treatment in a CO2-depletion unit (40) to obtain a primary CO2-depleted blast furnace gas stream (D); (d) reacting the primary CO2-depleted blast furnace gas stream (D) and a proportion (B2) of the blast furnace gas stream (B) with a first (d) mixing the secondary CO2-depleted blast furnace gas stream (E) with a proportion of the coke oven gas stream (C) in a second mixing unit (70) to obtain a tertiary CO2-depleted gas stream (F); (e) feeding said tertiary CO2-depleted gas stream (F) from a coke oven plant to an underfire system of a coke oven (80) to convert coal into coke, a second CO2-depleted blast furnace gas stream (E) having characteristics determined by a first analyzer (65) downstream of the first mixing unit (60) and a third CO2-depleted gas stream (F) having characteristics determined by a second analyzer (75) downstream of the second mixing unit (70); a fixed proportion (B2) of the blast furnace gas stream (B) and a fixed proportion (C) of the coke oven gas stream (C) are controlled to adjust at least one of the CO2 content, the CO content, the H2 content, the Wobbe index, the stoichiometric combustion air requirement, and the lower heating value in the tertiary CO2-depleted gas stream (F) based on the characteristics determined by the first (65) and second (75) analyzers, thereby controlling the operation of an underfire system.

Description

[Technical Field]

[0001] The present invention generally relates to a method for operating a coke oven plant, and to a corresponding coke oven plant. [Background technology]

[0002] As is well known, modern coke production plants, or coke oven plants, are arranged in rows and can contain anywhere from as few as 10 to over 100 coke oven chambers. Due to the physical dimensions of the coking chambers (narrow, long, and tall), they are sometimes called slot ovens. The ovens are designed and operated to recover volatile products generated from the coal during the carbonization process. The carbonization process is typically operated cyclically, repeating the following main steps: loading; carbonization; and extrusion (emptying).

[0003] The heat required to operate the carbonization process is generally provided by the combustion of combustible gases. These gases can be of any suitable properties, but for economic reasons, blast furnace gas can be used if it is available in the coke oven plant.

[0004] Furthermore, blast furnace operation is complex, and many parameters and input variable modifications must always be considered in order to produce high-quality, high-yield pig iron. As a result, the composition of the resulting blast furnace gas fluctuates significantly over time.

[0005] Therefore, the operation of a coke oven heating / underfiring system using blast furnace gas is far from ideal, not only in terms of its lower heating value but also due to its highly variable composition. (Technical problem)

[0006] The object of the present invention is to provide a method for operating a coke oven plant that can be heated with blast furnace gas, and further, to provide better and more reliable heating in an underfire system by providing significantly enhanced and more flexible underfire gas control, particularly with the aim of maintaining the best combustion parameters and efficiency of the coke oven at all times. Preferably, this method should be applicable not only to new coke oven plants but also to existing plants. [Overview of the project]

[0007] To achieve this objective, in a first embodiment, the present invention provides a method for operating a coke oven plant: a) Provide a blast furnace gas stream containing carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2), and a coke oven gas stream containing hydrogen, carbon monoxide, and methane (CH4) (and other hydrocarbons); b) A CO conversion unit converts carbon monoxide to carbon dioxide to treat (at least) a portion of the blast furnace gas stream and obtain a treated blast furnace gas stream; c) The blast furnace gas stream processed from step b) is subjected to carbon dioxide removal in a CO2-depletion unit to obtain a primary CO2-depleted blast furnace gas stream; d) A certain proportion of the primary CO2-depleted blast furnace gas flow from step c) and the blast furnace gas flow are mixed in a first mixing unit to obtain a secondary CO2-depleted blast furnace gas flow; e) A certain proportion of the secondary CO2-depleted blast furnace gas flow and coke oven gas flow from step d) are mixed in a second mixing unit to obtain a tertiary CO2-depleted gas flow; f) We propose a method comprising the following steps: supplying the tertiary CO2-depleted gas flow from the coke oven plant to the underfire system of the coke oven to convert coal into coke, thereby generating coke oven gas and exhaust gas.

[0008] According to the present invention, one or more characteristics of the secondary CO2-depleted blast furnace gas flow are determined by a first analyzer downstream of a first mixing unit, and one or more characteristics of the tertiary CO2-depleted gas flow are determined by a second analyzer downstream of a second mixing unit. A certain proportion of the blast furnace gas flow and a certain proportion of the coke oven gas flow are controlled to adjust at least one of the one or more characteristics selected from the CO2 content (or CO2 concentration), CO content (or CO concentration), H2 content (or H2 concentration), Wobbe index, stoichiometric combustion air / oxygen demand, and lower heating value in the tertiary CO2-depleted gas flow, based on the characteristics determined by the first and second analyzers, thereby controlling the operation of the underfire system.

[0009] In a second aspect, the present invention relates to a coke oven plant preferably configured for carrying out the coke oven plant operation method described herein, a) A blast furnace gas network configured to provide a blast furnace gas source, particularly a blast furnace gas stream containing carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2); and a coke oven gas network configured to provide a coke oven gas source, particularly a coke oven gas stream containing hydrogen (H2), carbon monoxide (CO), and methane (CH4) (and other hydrocarbons), or coke oven gas produced in the coke oven plant itself; b) A CO conversion unit that is fluidly connected to the blast furnace gas supply source and is configured to process (at least) a portion of the blast furnace gas flow by converting carbon monoxide to carbon dioxide in order to obtain a processed blast furnace gas flow; c) A CO2-depletion unit that is fluidly connected to the CO conversion unit and configured to remove carbon dioxide from the treated blast furnace gas flow in order to obtain a primary CO2-depleted blast furnace gas flow; d) A first mixing unit, controllably fluidly connected to the blast furnace gas supply source, including a controllable blast furnace bypass flow regulator, e.g., a first controllable valve, which is fluidly connected to the CO2-depletion unit, and the first mixing unit is configured to mix a primary CO2-depleted blast furnace gas flow from the CO2-depletion unit with a certain proportion of the blast furnace gas flow to obtain a secondary CO2-depleted blast furnace gas flow; e) A second mixing unit, fluidly connected to the first mixing unit and including a controllable coke oven gas flow regulator such as a second controllable valve, which is fluidly connected to the coke oven gas source, and is configured to mix a certain proportion of the secondary CO2-depleted blast furnace gas flow from the first mixing unit with the coke oven gas flow to obtain a tertiary CO2-depleted gas flow; and f) We propose a coke oven plant including a coke oven of a coke oven plant, which includes an underfire system configured to fluidly connect to the second mixing unit and to burn the tertiary CO2-depletion gas flow to convert coal into coke, thereby producing coke oven gas and exhaust gas.

[0010] The coke oven plant according to the present invention further includes a first analyzer downstream of a first mixing unit (and upstream of a second mixing unit) configured to determine one or more characteristics of a secondary CO2-depleted blast furnace gas flow, a second analyzer downstream of a second mixing unit (and upstream of an underfire system) configured to determine one or more characteristics of a tertiary CO2-depleted gas flow, and a control unit configured to control the operation of an underfire system by determining a certain percentage of blast furnace gas flow and a certain percentage of coke oven gas flow based on the characteristics provided by the first and second analyzers, and by controlling a controllable blast furnace bypass flow regulator and a controllable coke oven gas flow regulator to adjust at least one of the one or more characteristics selected from the tertiary CO2-depleted gas flow, including the CO2 content (or CO2 concentration), CO content (or CO concentration), H2 content (or H2 concentration), Wobbe index, stoichiometric combustion air / oxygen demand, and lower heating value.

[0011] Blast furnace gas (BFG), also known as top gas, is a byproduct of blast furnace operation, generated when iron ore is reduced to metallic iron with coke. Blast furnace gas is mainly composed of nitrogen, carbon dioxide, carbon monoxide, and some hydrogen. In conventional processes, blast furnace gas typically contains about 45-55% N2, about 15-25% CO, about 15-25% CO2, and about 1-10% H2. Depending on the operation and process of the blast furnace, for example, in a blast furnace injected with natural gas, the volume fraction of carbon monoxide can exceed 25%, while the volume fraction of hydrogen can exceed 10%, and H2 can reach 15%.

[0012] Blast furnace gas is generally not an ideal gas due to its relatively low calorific value, but it can be used in the underfire system of a coke oven (row). Its main drawbacks, aside from its generally low calorific value, are the unavoidable residues or by-products from the metallurgical process, which is operated to produce the best possible pig iron, regardless of the composition of these residues. Consequently, this composition can vary considerably over time based on the actual operating conditions of the blast furnace. Therefore, operating a coke oven requires not only a large amount of blast furnace gas, but, more importantly, it is extremely difficult to operate it stably and under controlled conditions.

[0013] While it is known that adding coke oven gas, i.e., the gas produced during the carbonization process, in a certain proportion can mitigate the problem of the low calorific value of blast furnace gas, this does not significantly reduce the variability of the blast furnace gas composition and, consequently, the variability of some of its properties related to its use in the coke oven's underfire system. On the contrary, coke oven gas is itself a byproduct, and its composition can change individually over time, potentially exacerbating the unstable operation of the underfire system.

[0014] The inventors concluded that even when blast furnace gas and coke oven gas are used in combination and controlled, it is not possible to reliably provide a gas whose properties are appropriate and sufficiently consistent for the optimal operation of an underfire system. However, the inventors found that both problems can be significantly reduced by removing a large proportion of CO2 from a portion of the blast furnace gas, although this reduces the overall processing capacity, leaving a larger proportion of calorific gases in the resulting flow. Furthermore, the inventors found that by processing in this manner, it is actually possible to benefit from a real and additional degree of freedom in controlling the properties of the underfire gas, thereby enabling independent and therefore more reliable control of the different properties of the resulting gases. In fact, the inventors found that not only is the variation in the composition of blast furnace gas primarily due to variations in its CO2 content, but removing it (at least partially) also produces gases with significantly different desirable properties. In fact, by (essentially) depleting all of the CO2 from the blast furnace gas, not only does the calorific value of the resulting gas increase, but the more important properties of the resulting CO2-depleted blast furnace gas are improved compared to the original blast furnace gas, for example, its Wobbe index increases. The Wobbe index is an important property of combustible gases, and burners used in underfire systems are generally set to function optimally when this property is kept within a reasonable range.

[0015] The fact that there are two gases with vastly different properties, yet derived from the same inexpensive blast furnace gas, provides a large and flexible spectrum of combinations that can achieve better combustion parameters and efficiencies in the coke oven. Most importantly, a further significant advantage of the present invention is that these advantages are obtained in conjunction with a substantial reduction in CO2 emissions in the coke oven's exhaust stack (chimney).

[0016] Furthermore, since the amount of CO contained in blast furnace gas fluctuates considerably, it is advantageous to remove (subtract) this gas from the blast furnace gas. However, in contrast to CO2, CO is highly toxic, and its removal requires far more stringent safety measures, thus presenting a greater problem. Therefore, the present invention provides a conversion of carbon monoxide to carbon dioxide by any suitable process. The original CO2 and the newly formed CO2 can then be removed in a single run by known methods, as will be further detailed below. On the other hand, in contrast to CO2, CO still provides a constant calorific value and can be usefully used in downstream underfire systems. As will be further described below, a conversion of CO to CO2 preferably used in beneficial embodiments is the so-called water-gas shift reaction. As will be understood by those skilled in the art, this further reduces CO2 emissions in the coke oven exhaust stack.

[0017] As a result, the present invention provides secondary CO2-depleted blast furnace gas obtained by adding a reasonable and controlled amount of original untreated blast furnace gas by determining the appropriate gas characteristics downstream of the first mixing unit, and by diverting an appropriate amount of untreated blast furnace gas to the first mixing unit, thereby enabling better control of calorific value fluctuations and other characteristics such as the Wobbe index, and improving flexibility and reliability in coke oven operation. Preferably, the corresponding characteristics of the blast furnace gas are already available through monitoring in the blast furnace gas network, or can be determined separately by a third analyzer and sent to the control unit to more accurately reduce fluctuations in the characteristics of the tertiary CO2-depleted flow.

[0018] Furthermore, it can be expected that a certain proportion of coke oven gas will be introduced into the now combined at least partially CO₂-depleted blast furnace gas stream (i.e., the secondary CO₂-depleted blast furnace gas), whereby at least the calorific value of the gas supplied to the underfire system is increased. In fact, coke oven gas is generally formed by heating coal to 1100°C in the absence of air / oxygen. The typical composition of coke oven gas includes, for example, hydrogen (H₂-55%), methane (CH₄-24%), carbon monoxide (CO-8%), other hydrocarbons (C n H m -1.5-3%). The corresponding properties of the coke oven gas are preferably already available, such as from monitoring in the coke oven gas network, or are separately determined by a fourth analyzer, and can be sent to the control unit to more accurately reduce fluctuations in the properties of the tertiary CO₂-depleted stream.

[0019] Overall monitoring and control of this method is achieved by continuously determining or monitoring one or more properties of the secondary CO₂-depleted blast furnace gas stream (i.e., CO₂-depleted blast furnace gas mixed with untreated blast furnace gas as needed) and the tertiary CO₂-depleted gas stream (i.e., CO₂-depleted blast furnace gas mixed with untreated blast furnace gas and coke oven gas as needed), and by controlling or commanding flow regulators such as controllable valves arranged in the blast furnace gas bypass and the coke oven gas supply line. Of course, additional monitoring and / or control points may be provided if deemed necessary or useful.

[0020] Advantageously, the proportion of the blast furnace gas stream and the proportion of the coke oven gas stream are controlled based on the properties determined by the first and second analyzers to adjust at least one of the Wobbe index and the lower heating value in the tertiary CO₂-depleted gas stream.

[0021] The Wobbe index (generally referred to as IW) is expressed as follows (in MJ / Nm 3 ) defined as: If JPEG0007915285000001.jpg1016VC is a higher heating value (or a higher calorific value) and GS is specific gravity, JPEG0007915285000002.jpg1031Here, ρ STP is the density of gas under standard conditions (0°C, 101.325 kPa), ρ air , STP is the density of air under standard conditions, M is the molar mass of the gas, and M air is the molar mass of air, which is approximately 28.96 kg / kmol.

[0022] Lower Heating Value (LHV; net calorific value; NCV, or lower calorific value; LCV) is a measure of the available thermal energy generated by the combustion of fuel. It is measured as a unit of energy per unit mass or volume of a substance such as kJ / Nm 3 assuming that the water component in the combustion process remains in a vapor state at the end of combustion. Therefore, LHV is generally defined as the amount of heat released by combustion when the products are cooled to 150°C, which means that the latent heat of vaporization of water (and optionally other reaction products) is not recovered.

[0023] In short, the present invention enables significantly enhanced and reliable control of the operation of a coke oven underfire system by flexibly adjusting important characteristics of underfire gas such as the Wobbe index within a remarkably wide range through provision and controlled combination of two different gases from the same blast furnace gas, and further adjusting other characteristics of the underfire gas such as its lower heating value by adding coke oven gas when necessary or desirable. Furthermore, these advantages are achieved along with a significant reduction in the carbon emission of the overall carbonization process.

[0024] Preferably, the proportion of the blast furnace gas stream and the proportion of the coke oven gas stream are particularly or primarily controlled to reduce fluctuations in the operation of an underfiring system.

[0025] In an advantageous embodiment, fluctuations in one or more properties selected from the group consisting of CO₂ content, CO content, H₂ content, stoichiometric combustion air / oxygen requirement, Wobbe index and lower heating value of the tertiary CO₂-depleted stream are reduced by at least 5%, preferably at least 10%, more preferably at least 20%, compared to fluctuations in one or more of the same properties of blast furnace gas from a blast furnace gas supply source or network.

[0026] Alternatively or additionally, the proportion of the blast furnace gas stream and the proportion of the coke oven gas stream are particularly or primarily controlled to bring the Wobbe index close to a target value and / or to increase the lower heating value of the blast furnace gas.

[0027] In an advantageous embodiment, the Wobbe index of the tertiary CO₂-depleted stream is controlled to be within + / - 20%, preferably + / - 15%, more preferably + / - 10% of the preset / target value of the Wobbe index (specific to the underfiring system).

[0028] In a further advantageous embodiment, the lower heating value of the tertiary CO₂-depleted stream is increased by at least 10%, preferably at least 20%, more preferably at least 30% compared to the LHV of blast furnace gas from a blast furnace gas supply source or network. Accordingly, the LHV of the tertiary CO₂-depleted stream is generally 3700 to 5300kJ / Nm 3 , preferably within the range of 4100 to 5000kJ / Nm 3 adjusted to fall within the range of .

[0029] Alternatively or additionally, the proportion of the blast furnace gas stream and the proportion of the coke oven gas stream are particularly or primarily controlled to reduce the CO₂ content in the exhaust gas, that is, to reduce the carbon emission of the carbonization process.

[0030] In yet another advantageous embodiment, the CO2 emissions from the coke oven exhaust gas are reduced by at least 30%, preferably at least 60%, and more preferably at least 90%, compared to the CO2 emissions when operating without CO2 depletion under all other conditions (i.e., only blast furnace gas and coke oven gas from a blast furnace gas supply source via a bypass).

[0031] As briefly mentioned above, in a preferred embodiment, the method includes, in step b), processing of (at least) a portion of the blast furnace gas stream in a CO conversion unit in which a water-gas shift reaction is carried out and CO is converted to CO2 and hydrogen in the presence of water (steam). Therefore, in a coke oven plant, the CO conversion unit preferably includes a water-gas shift reactor. In this case, the calorific value of the resulting gas is further increased by the generation of hydrogen, while still allowing for the removal of CO which is converted to CO2.

[0032] Carbon dioxide removal in the CO2-depletion unit can be carried out using any known suitable method, such as chemical and / or physical absorption in one or more steps. The CO2-depletion steps preferably include one or more physical and / or chemical absorption methods, such as pressure swing absorption (PSA), vacuum pressure swing absorption (VPSA), and capture with a washing solution.

[0033] A CO2 depletion unit may include, for example, an absorption unit and a stripper unit. In the absorber, a cleaning solution (such as an aqueous amine solution) absorbs CO2 (and possibly other acidic gases such as H2S) from the blast furnace gas. The cleaning solution, enriched with the absorbed CO2, is sent to the stripper, where it is heated. This causes the cleaning solution to release the absorbed CO2, allowing it to be reused in the absorber. The released CO2 can be recovered and stored for use in other applications.

[0034] The cleaning solution can be any cleaning solution suitable for removing CO2 from the gas. For example, the cleaning may include a solution of monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), diisopropylamine (DIPA), and / or diglycolamine (DGA).

[0035] Pressure swing absorption (PSA) is a technique used to separate several gas species from a mixture of gases under pressure, depending on the molecular properties of the species and their affinity for the absorbent. It operates at temperatures close to ambient temperature. A selective absorbent (such as zeolite or activated carbon) is used as the trapping material, preferentially absorbing the target gas species under high pressure. The process then swings to low pressure to desorb the absorbed gases. Vacuum pressure swing absorption (VPSA) separates gases from a mixture of gases at near ambient pressure; the process then enters a vacuum state to regenerate the absorbent.

[0036] In certain embodiments, the water-gas shift reaction (step b)) can be combined with pressure swing absorption (step c)) in a so-called sorption-enhanced water-gas shift (SEWGS) reactor, for example, in a multi-bed pressure swing absorption (PSA) unit in which the vessel is filled with a water-gas shift catalyst and a CO2 absorbent. The SEWGS reactor combines a catalytic water-gas shift reaction with a solid absorbent-based CO2 separation (such as a K-enhanced hydrotalcite absorbent) to achieve both CO conversion and CO2 capture in a single unit.

[0037] In the context of the present invention, steps b) and / or c) may be combined into a single stage or apparatus, and each step may alternatively include multiple series or parallel processes of the same or different types, as needed or desired.

[0038] Furthermore, in another advantageous embodiment, the stoichiometric combustion air demand or requirement, or the stoichiometric combustion oxygen demand (i.e., the amount of air or oxygen required to achieve maximum combustion efficiency), is determined by at least the second analyzer so as to control the amount of oxygen or air supplied to the underfire system.

[0039] In the context of the present invention, the term "CO2-depleted" or "depletion" in the context of blast furnace gas is used to refer to gas (or the action of reducing such concentration) in which the CO2 concentration has been reduced compared to the original blast furnace gas supplied by a blast furnace gas source, such as blast furnace gas obtained directly from the blast furnace gas network or the top of the blast furnace. Even after CO2 removal, residual concentrations of CO2 may still remain in the blast furnace gas. Therefore, "CO2-depleted blast furnace gas" generally means "blast furnace gas with a low CO2 concentration." In particular, the removal of carbon dioxide in a CO2-depleted unit is such that the CO2 content or concentration in the primary CO2-depleted blast furnace gas stream is at most 10 volume-%, generally at most 7.5 volume-%, preferably at most 5 volume-%, and more preferably at most 2.5 volume-%.

[0040] Therefore, in yet another embodiment, the present invention proposes using the coke oven plant operating method described herein, or using the coke oven plant to reduce fluctuations in the operation of an underfire system heated by blast furnace gas.

[0041] Alternatively or additionally, the present invention proposes using the coke oven plant operating method described herein, or using such coke oven plant, in order to maintain the Wobbe index close to a predetermined or target value and to increase the lower heating value of the blast furnace gas.

[0042] Alternatively or additionally, the present invention proposes using the coke oven plant operating method described herein, or using such coke oven plant, in order to reduce the (non-renewable) CO2 content in the exhaust gas, i.e., to reduce CO2 emissions from the exhaust gas or the entire carbonization process.

[0043] The methods and coke oven plants according to one or more embodiments described herein achieve at least some of the following results and advantages:

[0044] CO2 emissions from the coke oven plant stack are reduced by 30% to 90% and beyond.

[0045] The final CO2 emissions can be adjusted according to the thermal control of the new or existing coke oven array, and the bypasses and adjustments described herein can maintain optimal combustion conditions for the heating flues and adjust the LHV and / or Wobbe index of the input gas to the coke oven gas.

[0046] A dedicated control unit / automation system (either integrated into an existing automation system or as a standalone module) can manage set points and target points to optimize combustion conditions and / or minimize CO2 emissions.

[0047] Standard instrumentation is generally sufficient to analyze and provide the data needed to calculate online the flow characteristics required to evaluate the optimal setting point of the tuning loop.

[0048] A dedicated automation module can be provided for continuously recording the heat gas input, and this dedicated automation module adjusts the setting point of the regulator valve to maintain the required heat input to the battery in order to adjust the LHV and Wobbe index of the coke oven gas relative to the input gas according to the combustion results. The flow rate of the CO2-depleted blast furnace gas stream is adjustable to achieve both minimizing CO2 emissions in the stack and efficient combustion while controlling the Wobbe index and minimum LHV in the regenerative heating system.

[0049] CO2-depleted blast furnace gas streams can be used as a substitute for conventional blast furnace gas that is only heated, but in all cases they have a higher LHV and a adjusted Wobbe index compared to upstream blast furnace gas, and produce less CO2 emissions than pure blast furnace gas or mixed gases.

[0050] Furthermore, even if the CO2 depletion unit is temporarily unavailable, it is not necessary to shut down the coke oven array; it can be supplied via the blast furnace gas bypass along with coke oven gas enrichment.

[0051] The method of the present invention can be implemented in both novel and existing coke oven plants, thereby providing a cost-effective way to upgrade existing plants, enabling novel operational flexibility, better control and efficiency of the underfire system, and / or reduction of CO2 emissions.

[0052] The coke plant operation method disclosed herein enables flexible management of different flows by an algorithm aimed at optimizing at least one of the following: at least one CO2 emission (by prioritizing the primary CO2-depleted BFG flow in the first mixing unit), the combustion parameters of the coke oven (by stabilizing the Wobbe index or adjusting the LHV in the tertiary CO2-depleted flow), and / or the heat input (by reducing fluctuations in one or more characteristics such as the Wobbe index and / or LHV in the tertiary CO2-depleted flow).

[0053] Finally, a special advantage of the present invention is that it can be implemented in both new and existing coke oven plants. [Brief explanation of the drawing]

[0054] Preferred embodiments will be described, for example, with reference to the attached drawings. [Figure 1] This is a schematic diagram of an embodiment of a coke oven plant (part of it).

[0055] Further details and advantages of the present invention will become apparent from the following detailed description of some non-limiting embodiments with reference to the accompanying drawings. [Modes for carrying out the invention]

[0056] An embodiment of the operation method of a coke oven plant, or an embodiment of such a coke oven plant itself, is schematically shown in Figure 1.

[0057] The coke oven or coke oven row 80 is supplied with a coke oven supply flow, which is a so-called tertiary CO2-depleted flow F, and is generated by a certain proportion of coke oven gas (COG) flow C, which is mainly generated by using (initial) blast furnace gas (BFG) flow B from BFG supply sources such as the BFG network 10, and coke oven gas flow H directly from COG supply sources such as the COG network or from the coke oven.

[0058] As is clear from Figure 1, a portion of the BFG flow B, B1, i.e., the first portion, is first supplied to the CO conversion unit 30, where at least a portion, preferably essentially all, of the carbon monoxide CO contained in the BFG, for example, >90 mol-%, preferably >95 mol-%, and more preferably >99 mol-%, is converted to carbon dioxide. Advantageously, the CO conversion unit includes a water-gas shift reactor that converts CO to CO2 and H2 in the presence of water vapor. This CO conversion not only significantly reduces the content of toxic CO, but can also be removed in the next step along with the original CO2, and the energy still contained in the CO can be recovered by generating additional hydrogen.

[0059] The resulting treated BFG then enters the CO2-depletion unit 40, where it captures and removes most of the CO2 (original and generated by the CO conversion unit 30). Capture and removal can be achieved by any suitable technology, e.g., one or more physical and / or chemical absorption processes, such as pressure swing absorption (PSA), vacuum pressure swing absorption (VPSA), or capture by washing solution. The overall reduction of CO2 depends on the initial CO and CO2 content and the processes used in both the CO conversion unit and the CO2-depletion unit. However, a reduction of more than 85%, more preferably more than 90%, or even more than 95% of CO2 emissions compared to the original BFG B (or B1 or B2) can generally be achieved within the primary CO2-depleted BFG flow leaving the CO2-depletion unit.

[0060] The resulting primary CO2-depleted BFG flow D is then supplied to a first mixing unit 60, where it is mixed with a certain percentage B2 of the initial BFG, i.e., a second part, as needed, to adjust one or more of its properties, such as CO2 content, CO content, H2 content, Wobbe index, and lower heating value. The adjustment of these one or more properties is controlled by a control unit (not shown) based on measurements of these properties performed by a first analyzer 65 located downstream of the first mixing unit 60, and by operating a BFG bypass flow regulator 15, which may be a controllable valve, to control the amount of BFG B2 added to the first mixing unit 60 via the BFG bypass line. The sum of the BFG treated flow, i.e., part B1, and the BFG bypass flow, i.e., the certain percentage B2, is the total amount of BFG flow B.

[0061] The BFG bypass flow regulator 15 can be controlled to primarily use CO2-depleted BFG by prioritizing the use of primary CO2-depleted BFG flow D, thereby significantly reducing the overall CO2 content in exhaust G at the coke oven stack 90. ​​Alternatively, the BFG bypass flow regulator 15 can primarily reduce variations in one or more of the aforementioned characteristics by adjusting the flow through the bypass pipe to best linearize one or more of the aforementioned characteristics, as long as this is possible within the flow rates of the mixed flows B2 and D. The BFG bypass flow regulator 15 can, of course, also best compromise between reducing the overall CO2 content and variations in exhaust G.

[0062] Initially, by using at least several primary CO2-depleted BFG flows D instead of only BFG B2 flows, a reduction in the one or more of the aforementioned characteristic variations can be achieved. However, for the same reasons, namely to reduce variations and / or increase the calorific value of gas flows D, it is generally necessary or desirable to further controllably add a certain percentage of coke oven gas.

[0063] Therefore, the primary CO2-depleted BFG flow E leaving the first mixing unit 60 is supplied to the second mixing unit 70 along with a certain proportion of coke oven gas GOG flow C, the proportion of which can be controlled via the COG flow regulator 25. Here again, the control of the regulator is advantageously based on one or more of the aforementioned characteristics determined by the second analyzer 75 located downstream of the second mixing unit 70.

[0064] Similarly, by controlling the COG flow regulator 25, the secondary CO2-depleted BFG E can be used as the primary flow, thereby "maintaining" a reduction in the overall CO2 content in the exhaust G at the stack 90 of the coke oven 80. Alternatively, by controlling the COG flow regulator 25, the fluctuations of one or more of the aforementioned characteristics in the tertiary CO2-depleted flow can be reduced, primarily by adjusting the flow of COG flow C to best linearize the aforementioned characteristics(s), to the extent that this is possible within the flow rates of the mixed flows C and E. Here again, by controlling the COG flow regulator 25, it is also possible to best compromise between the reduction in the overall CO2 content in the exhaust G and the reduction of the aforementioned fluctuations.

[0065] Where necessary or desirable, further analyzers may be provided, such as a third analyzer 10.5 for determining one or more properties of the BFG flow B and / or a fourth analyzer 20.5 for determining one or more properties of the COG flow C. The determined property values ​​can be supplied to a control unit to further improve the control of the composition and therefore properties of the tertiary CO2-depletion flow supplied to the underfire system of the coke oven 80.

[0066] In the coke oven (row), coal is converted into coke by the heat generated by an underfire system that burns the tertiary CO2-depletion flow F. Combustion generates an exhaust flow G, and carbonization operation generates coke oven gas H, which, as mentioned earlier, can be used as a source of COG for the COG flow C.

[0067] As an example of what can be achieved with the present invention, refer to the table below which shows some improvements when operating with the present invention (tertiary CO2-depleted gas) compared to operating with a mixed BFG (a conventional mixture of blast furnace gas and coke oven gas) and COG that do not deplete CO2: while moderately increasing the LHV and significantly reducing CO2 emissions in the stack.

[0068] [Table 1] [Explanation of Symbols]

[0069] 10. Blast Furnace Gas (BFG) Network 10.5 The third analyzer 15 BFG Bypass Flow Regulator B Initially BFG style B1 BFG processing flow, part of the so-called initial BFG flow B2 BFG bypass flow, a certain percentage of the so-called initial BFG flow 20 Coke Oven Gas (COG) Network 20.5 The fourth analyzer 25 COG flow regulator C COG style 30 CO2 Conversion Unit 40 CO2-Depletion Units D Primary CO2-Depleted BFG Flow 60 First mixing unit 65 First analyzer E Secondary CO2-Depleted BFG Flow 70 Second Mixing Unit 75 Second analyzer F 3rd CO2-Depleted BFG Flow 80 coke ovens, rows of coke ovens G Coke oven exhaust flow, exhaust flow 90 Exhaust Stack H Coke oven gas produced in a coke oven

Claims

1. a) Carbon monoxide (CO), carbon dioxide (CO) ２ and hydrogen H ２ Blast furnace gas stream (B) containing hydrogen H ２ , carbon monoxide (CO) and methane (CH) ４ The coke oven gas flow (C) includes; b) A CO conversion unit (30) converts carbon monoxide into carbon dioxide to treat a portion (B1) of the blast furnace gas flow (B) and obtain a treated blast furnace gas flow; c) CO ２ - Carbon dioxide is removed in the depletion unit (40), and the primary CO2 ２ - Obtain depleted blast furnace gas flow (D); d) Primary CO from process c) ２ - A certain ratio (B2) of depleted blast furnace gas flow (D) and blast furnace gas flow (B) is mixed in the first mixing unit (60) to produce secondary CO ２ - Obtain depleted blast furnace gas flow (E); e) Secondary CO from step d) ２ - mixing a certain proportion of the CO-depleted blast furnace gas stream (E) and the coke oven gas stream (C) in a second mixing unit (70) to obtain tertiary CO ２ -depleted gas stream (F); f) The tertiary CO ２ - Depleted gas stream (F) is supplied from the coke oven plant to the underfire system of the coke oven (80) to convert coal into coke, thereby generating coke oven gas (H) and exhaust gas (G); A method for operating a coke oven plant, including each process, Secondary CO ２ - The characteristics of the depleted blast furnace gas flow (E) are determined by the first analyzer (65) downstream of the first mixing unit (60), and the tertiary CO ２ - The characteristics of the depleted gas flow (F) are determined by a second analyzer (75) downstream of the second mixing unit (70); A certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage of the coke oven gas flow (C) are determined based on the characteristics determined by the first (65) and second (75) analyzers, the tertiary CO ２ - CO in depleted gas flow (F) ２ content, CO content, H ２ A method for operating a coke oven plant, which controls the operation of the underfire system by adjusting at least one of the coke content, Wobbe index, stoichiometric combustion air demand, and lower heating value.

2. A certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage (C) of the coke oven gas flow are the tertiary CO2 ２ The method according to claim 1, which is controlled based on the characteristics determined by the first (65) and second (75) analyzers for adjusting at least one of the Wobbe index and lower heating value in the depleted gas stream (F).

3. The method according to claim 1 or 2, wherein a certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage of the coke oven gas flow (C) are controlled to reduce fluctuations in the operation of the underfire system.

4. A certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage (C) of the coke oven gas flow (C) are the CO2 in the exhaust gas (G). ２ CO content and / or exhaust gas (G) ２ The method according to claim 1 or 2, which is controlled to reduce emissions.

5. A certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage (C) of the coke oven gas flow (C) are required to achieve the target value of the Wobbe index and / or tertiary CO2 ２ - The method according to claim 1 or 2, wherein the lower heating value of the depleted gas flow (F) is controlled to increase.

6. Tertiary CO ２ The method according to claim 5, wherein the Wobbe index of the depleted flow is controlled to be within a range of + / - 20% of a pre-set target value of the Wobbe index.

7. Tertiary CO ２ - The Wobbe index for depleted flow is 3.5–7 MJ / Nm ３ The method according to claim 5, which is adjusted to within the range.

8. Tertiary CO ２ - The method according to claim 5, wherein the lower heating value of the depleted flow is increased by at least 10% compared to the lower heating value of blast furnace gas from a blast furnace gas supply source.

9. Tertiary CO ２ - The lower heating value of depleted flow is 3700–5300 kJ / Nm³ ３ The method according to claim 5, which is controlled to be within a certain range.

10. The method according to claim 1 or 2, wherein in step b), the treatment of a certain percentage (B1) of the blast furnace gas flow (B) in the CO conversion unit (30) includes a water-gas shift reaction.

11. In step c), CO ２ - The method according to claim 1 or 2, wherein the removal of carbon dioxide in the depletion unit comprises one or more of physical absorption and chemical absorption.

12. The method according to claim 1 or 2, wherein steps b) and c) are carried out in an absorption-enhanced water-gas shift reactor.

13. In step c), CO ２ - Carbon dioxide removal in depletion units is primary CO2 ２ - CO in depleted blast furnace gas stream (D) ２ The method according to claim 1 or 2, wherein the content is such that it is a maximum of 7.5% by volume.

14. a) Carbon monoxide (CO), carbon dioxide (CO) ２ and hydrogen H ２ A blast furnace gas source configured to provide a blast furnace gas stream (B) containing hydrogen H ２ , carbon monoxide (CO) and methane (CH) ４ A coke oven gas source configured to provide a coke oven gas flow (C) including; b) A CO conversion unit (30) connected to the blast furnace gas supply source and configured to process a portion (B1) of the blast furnace gas flow (B) by converting carbon monoxide to carbon dioxide, thereby obtaining a processed blast furnace gas flow; c) Connected to the CO conversion unit (30), and the primary CO ２ - To obtain a depleted blast furnace gas stream (D), a CO2-750 ２ - Depletion units (40); d) The CO ２ - A first mixing unit (60) controllably connected to the blast furnace gas supply source, including a depletion unit (40) and a controllable blast furnace bypass flow regulator (15), wherein the CO ２ - Primary CO2 from depletion unit (40) ２ - Mixing the depleted blast furnace gas stream (D) with a certain proportion (B2) of the blast furnace gas stream (B) to produce secondary CO2 ２ - The first mixing unit (70) configured to obtain a depleted blast furnace gas flow (E); e) A second mixing unit (70) controllably connected to the coke oven gas supply source, including a controllable coke oven gas flow regulator (25) connected to the first mixing unit (60), wherein secondary CO2 from the first mixing unit (60) ２ - A certain ratio of depleted blast furnace gas flow (E) and coke oven gas flow (C) is mixed to produce tertiary CO2. ２ - The second mixing unit (70) configured to obtain a depleted gas flow (F); f) Connected to the second mixing unit (70) and for converting coal to coke, the tertiary CO ２ - A coke oven (80) of a coke oven plant, including an underfire system configured to burn a depleted gas stream (F) to thereby produce coke oven gas (H) and exhaust gas (G); A coke oven plant including, Secondary CO ２ - A first analyzer (65) downstream of a first mixing unit (60) configured to determine the characteristics of the depleted blast furnace gas flow (E), and tertiary CO ２ - A second analyzer (75) downstream of the second mixing unit (70) configured to determine the characteristics of the depleted gas flow (F); a certain percentage (B2) of the blast furnace gas flow (B) and a certain percentage of the coke oven gas flow (C) based on the characteristics provided by the first (65) and second (75) analyzers, and a controllable blast furnace bypass flow regulator (15) and a controllable coke oven gas flow regulator (25) of the tertiary CO ２ - CO in depleted gas flow (F) ２ content, CO content, H ２ The control unit further includes a control unit configured to control the operation of the underfire system by controlling to adjust at least one of the content, Wobbe index, stoichiometric combustion air demand, and lower heating value. Coke oven plant.

15. The coke oven plant according to claim 14, wherein the CO conversion unit (30) includes a water-gas shift reactor.

16. CO ２ - The depletion unit comprises one or more physical and chemical absorbers, as described in claim 14 or 15, in the coke oven plant.

17. CO conversion unit (30) and CO ２ - The coke oven plant according to claim 14, wherein each depletion unit (40) is formed by an absorption-enhanced water-gas shift reactor.

18. CO ２ - Depletion units are primary CO2 ２ - CO in depleted blast furnace gas stream (D) ２ A coke oven plant according to claim 14 or 15, which is operated so that the content is a maximum of 7.5% by volume.

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