Coke oven alternative fuel gas and method for maintaining the temperature of a coke oven

Abstract

To provide a coke oven alternative fuel gas capable of suppressing coking and a heat insulation method for a coke oven using the same.SOLUTION: A coke oven alternative fuel gas comprises a first gas with a lower heating value of 6,000 to 25,000 kcal / Nm3 and at least one of inert gas and a second gas with a lower heating value of 500 to 3,000 kcal / Nm3, where a lower heating value is 500 to 3,000 kcal / Nm3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application relates to a coke oven alternative fuel gas and a method for maintaining the temperature of a coke oven. [Background technology]

[0002] In integrated steel mills, by-product gases generated during the steelmaking process are recovered and utilized. By-product gases in steel mills are typically represented by coke oven gas (hereinafter sometimes referred to as "COG"), blast furnace gas (hereinafter sometimes referred to as "BFG"), converter gas (hereinafter sometimes referred to as "LDG"), etc., and the gas composition, calorific value, and amount of gas generated per unit time differ for each process. Generally, BFG discharged from the top of the blast furnace is effectively utilized as fuel gas for power generation, hot blast furnace fuel gas, and as part of the coke oven fuel gas. On the other hand, BFG has a calorific value of 680-850 kcal / Nm³. 3 Because of its extremely low calorific value, when used as a fuel gas, it is practically mixed with high-calorie gases such as COG or LDG to achieve a calorific value of 1000 kcal / Nm³. 3 It is used as the gas described above.

[0003] If the gases mixed here are COG or LDG, they are economical because they are by-product gases generated within the steelworks. These also have a high calorific value and are easy to handle, so they are widely used as fuel in steelmaking processes such as steel heating furnaces, heat treatment furnaces, and annealing furnaces. Therefore, depending on fluctuations in the energy supply and demand of the steelworks, natural gas (hereinafter referred to as "L") may be selectively used after considering the gas balance to supplement COG, which is a high-calorific gas that tends to be in short supply, or to supply the optimal by-product gas according to the production process within the plant. N It is also conceivable that high-calorie gases such as "G" (or liquefied petroleum gas, hereinafter sometimes referred to as "LPG") may be purchased and used.

[0004] Even in coke ovens, which are listed here as a use for BFG, in practice, a mixed gas (hereinafter sometimes referred to as "MG") made by mixing BFG with a small amount of COG is commonly used as fuel. Coke ovens can be classified into single-stage ovens that use only COG (rich gas) as fuel (with the exception of single-stage ovens that use poor gas), and double-stage ovens that can use either BFG / MG (poor gas) or COG. The latter is more commonly used in coke ovens at integrated steelworks. In most chamber-type coke ovens, a heat storage chamber is installed at the bottom of the furnace body, with combustion chambers and carbonization chambers arranged alternately above it. Poor gas and air are preheated in the heat storage chamber, and after combustion, they are guided to an adjacent heat storage chamber for heat recovery before being discharged through the flue. Therefore, the flow path supplied to the coke oven combustion chamber differs depending on whether MG or COG is used as fuel, and low-calorie MG is preheated in the heat storage chamber before being supplied for combustion.

[0005] Normally, coke oven fuel gas is increased in calorific value by mixing low-calorie BFG with domestically produced COG, and the mixing ratio is adjusted as needed to create a mixed gas (MG) that maintains an optimal constant calorific value. On the other hand, when the blast furnace is shut down, the supply of BFG is stopped, and in this case, only COG is available. COG continues to be generated as long as coke oven operation (coal charging) continues, but if coke oven operation is stopped for a long period due to unexpected natural disasters or large-scale troubles, such as delays in coal transport or the shutdown of the mobile equipment responsible for coke oven operation, the amount of COG generated will gradually decrease. In such cases, it may become difficult to continue using only COG (although it is considered extremely rare for total COG generation to be zero, as mentioned above, steel mills use it as fuel gas in steelmaking processes such as product manufacturing, so depending on the supply and demand balance, it is possible that the COG consumed on-site in the coke oven may be depleted). Furthermore, since it may be possible to selectively use the finite by-product gas within the plant according to its characteristics, it can be said that it is beneficial to have an elastic structure that utilizes external energy. Against this backdrop, it is important to provide redundancy (broaden the range of options) for the fuel gas in coke ovens, which use large amounts of gas.

[0006] To address the problems described above, it is conceivable to dilute high-calorie externally purchased gases with inert gases such as air or nitrogen, or low-calorie by-product gases, and use them as alternative fuel gases. However, the following prior art has been proposed.

[0007] Patent Document 1 discloses a mixing control method for mixing and diluting high-calorie gases such as LNG and LPG with low-calorie by-product gases of a steel mill, and a manufacturing method characterized by connecting the adjusted COG produced by the aforementioned method to a coke oven gas pipe to be used as fuel gas within the steel mill. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-254753 [Overview of the project] [Problems that the invention aims to solve]

[0009] Patent Document 1 states that COG substitute fuels having combustion characteristics equivalent to COG can be prepared and supplied to each fuel-using plant as prepared COG. Commercially available LNG and LPG used as high-calorie gases in this context are known to contain hydrocarbons with larger molecular weights than the by-product gases generated at steel mills. In addition, these hydrocarbon gases generally undergo thermal decomposition in high-temperature environments, resulting in carbon deposition (coking). Therefore, if the prepared COG described in Patent Document 1 is supplied to equipment that may circulate in high-temperature environments, it will cause coking. If this phenomenon occurs in equipment or piping, it can lead to problems such as blockage of the gas flow path and increased pressure loss. Furthermore, if it occurs in a heat exchanger, it can lead not only to increased pressure loss but also to a decrease in heat transfer efficiency. Thus, coking can make it difficult to maintain the integrity of equipment and ensure stable operation.

[0010] Therefore, the main purpose of this disclosure is to provide a coke oven alternative fuel gas that can suppress coking and a method for maintaining the temperature of a coke oven using the same, in view of the above circumstances. [Means for solving the problem]

[0011] This disclosure, as one embodiment for solving the above problem, provides a lower heating value of 6000 to 25000 kcal / Nm 3 The first gas, an inert gas, and a lower heating value of 500-3000 kcal / Nm 3 It contains at least one of the second gases and has a lower heating value of 500-3000 kcal / Nm³ 3 It provides a coke oven alternative fuel gas.

[0012] Furthermore, as one embodiment for solving the above-mentioned problems, this disclosure provides a method for maintaining the temperature of a coke oven, in which the coke oven alternative fuel gas is introduced into the combustion chamber via a heat storage chamber and burned at an air ratio such that the residual oxygen in the exhaust gas is 5 vol.% or more and 15 vol.% or less.

[0013] In the above method for maintaining the temperature of a coke oven, the coke oven alternative fuel gas, which is produced by pre-mixing the gases constituting the coke oven alternative fuel gas, may be directly supplied to the coke oven fuel gas supply piping and introduced into the heat storage chamber. Alternatively, each of the gases constituting the coke oven alternative fuel gas may be directly supplied to the coke oven fuel gas supply piping, and the coke oven alternative fuel gas obtained by mixing in the coke oven fuel gas supply piping may be introduced into the heat storage chamber. [Effects of the Invention]

[0014] The coke oven alternative fuel gas of this disclosure can suppress coking. Furthermore, the coke oven heating method of this disclosure can maintain the temperature of the coke oven while suppressing coking. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view of coke oven 100, as seen from the direction of the furnace leader. [Figure 2] It is a schematic diagram of the test system used in Example (1). [Figure 3] It is the result of the weight change of the SUS test piece in Example (1). [Figure 4] It is the result of the carbon incineration test in Example (2). [Figure 5] It is the result showing the influence of the residual oxygen concentration in the exhaust gas on the incineration rate of the blockage in Example (2). [Figure 6] It is a graph showing the mixing ratio of LNG and the supply situation of the alternative MG in the coke oven operation of Example (3). [Figure 7] It is the time history of the residual oxygen in the exhaust gas in the coke oven operation of Example (3). [Figure 8] It is a photograph showing the incineration situation of the test piece in Example (3).

Mode for Carrying Out the Invention

[0016] [Coke Oven Alternative Fuel Gas] The coke oven alternative fuel gas of the present disclosure has a low calorific value of 6000 - 25000 kcal / Nm 3 of the first gas, and at least one of an inert gas and a second gas having a low calorific value of 500 - 3000 kcal / Nm 3 and has a low calorific value of 500 - 3000 kcal / Nm 3 as such.

[0017] The calorific value is the amount of heat generated when a unit amount of fuel is adiabatically and completely burned and cooled to its original temperature. When the temperature before combustion is normal temperature, the latent heat of vaporization of the water vapor generated during the combustion process is also released. The calorific value including the latent heat of vaporization is called the higher calorific value (high calorific value, gross calorific value), and the one excluding it is called the lower calorific value (low calorific value, net calorific value). Usually, since the latent heat of vaporization of water vapor cannot be utilized, the latter is used, but there are also cases where the former is used. In the coke oven alternative fuel gas of the present disclosure, the lower calorific value is used to define the calorific value of the gas. The lower calorific value can be theoretically calculated from the composition of the obtained gas by analyzing the constituent components of each gas using gas chromatography.

[0018] <First Gas> The first gas is not particularly limited as long as it is a gas with a lower calorific value of 6000 - 25000 kcal / Nm 3 Typically, it mainly contains hydrocarbons having 1 to 4 carbon atoms. The hydrocarbons having 1 to 4 carbon atoms may contain only a single species or may contain a plurality of species as the main components. "Main component" refers to a component that occupies 50% or more, preferably 80% or more, more preferably 90% or more of the constituent components of the first gas on a volume basis. Therefore, "containing hydrocarbons having 1 to 4 carbon atoms as the main components" means that, on a volume basis, the proportion of hydrocarbons having 1 to 4 carbon atoms among the constituent components of the first gas is 50% or more, preferably 80% or more, more preferably 90% or more. Specifically, examples of the first gas include natural gas (LNG) and liquefied petroleum gas (LPG). These may be used alone or in combination. From the perspective of further suppressing coking, LNG may be used as the first gas. This is because there are reports that LPG has a higher propane content and is more likely to decompose compared to LNG.

[0019] The first gas has a high lower calorific value and high combustion characteristics. Since the first gas typically contains hydrocarbons, there is a risk of thermal decomposition and carbon deposition (coking) occurring in a high-temperature environment. Therefore, in the present disclosure, the first gas is diluted with an inert gas and / or a second gas, and a coke oven alternative fuel gas adjusted to a predetermined lower calorific value is used.

[0020] <Inert gas, second gas> The inert gas and / or second gas serve to dilute the first gas. The inert gas is N2, Ar, etc. The second gas has a lower heating value of 500-3000 kcal / Nm³. 3 Therefore, it is not particularly limited. For example, gases that are generated as by-products within a steel mill, such as converter gas, coke oven exhaust gas, BFG, LDG, and combustion exhaust gas, may also be included. In the case of coke oven alternative fuel gas, it is sufficient that at least one of the inert gas and the second gas is included, and both may be included.

[0021] <Coke oven alternative fuel gas> The coke oven alternative fuel gas is a first gas diluted with an inert gas and / or a second gas. This means that it may contain components other than the first gas, the inert gas, and the second gas, to the extent that it is effective. On the other hand, the coke oven alternative fuel gas may consist of the first gas and at least one of the inert gas and the second gas. However, even in this case, it means that inevitably contained components (e.g., air) may be present in trace amounts (e.g., 1% or less).

[0022] The proportion of gases that make up the coke oven alternative fuel gas (mainly the first gas, inert gas, and second gas) is such that the lower heating value of the coke oven alternative fuel gas is 500-3000 kcal / Nm³. 3 The following is not particularly limited. For example, in a coke oven alternative fuel gas, the proportion of the first gas may be 10-20% by volume, and the proportion of the inert gas and / or second gas may be 80-90%.

[0023] As described above, the coke oven alternative fuel gas of this disclosure is obtained by diluting the first gas with an inert gas and / or a second gas and adjusting it to a predetermined lower heating value. This makes it possible to suppress the occurrence of coking compared to using only the first gas, which has high fuel characteristics. Furthermore, as explained in the coke oven heat retention method described later, the occurrence of coking can be further suppressed by burning the coke oven alternative fuel gas at an air ratio such that the residual oxygen in the exhaust gas is between 5 vol.% and 15 vol.%.

[0024] [Methods for maintaining the temperature of a coke oven] The method for maintaining the temperature of a coke oven according to this disclosure involves introducing the above-mentioned coke oven alternative fuel gas (hereinafter sometimes referred to as "alternative MG") into the combustion chamber via a heat storage chamber and burning it at an air ratio such that the residual oxygen in the exhaust gas is 5 vol.% or more and 15 vol.% or less.

[0025] In order to explain the coke oven heat retention method of this disclosure, the configuration of the coke oven will be described. Figure 1 shows a schematic cross-sectional view of coke oven 100, an example of a coke oven to which the coke oven heat retention method of this disclosure can be applied, as viewed from the direction of the oven length (front-to-back direction of the paper). In Figure 1, the right side of the upper half in the height direction is a cross-sectional view cut at the carbonization chamber 10, and the left side is a cross-sectional view cut at the combustion chamber 20.

[0026] The coke oven 100 has multiple carbonization chambers 10 and combustion chambers 20 arranged alternately in the direction of the oven chamber length. By introducing carbon material such as coal into the carbonization chambers 10 and burning coke oven fuel gas in the combustion chambers 20, the carbon material is carbonized by dry distillation and carbonization, thereby obtaining coke (and coke oven gas). At the bottom of the coke oven 100 is a heat storage chamber 30 formed by stacking heat storage bricks 31 with gaps between them, where the coke oven fuel gas introduced into the combustion chambers 20 is preheated. The upper temperature of the heat storage chamber 30 is generally around 800 to 1100°C. The heat storage chamber 30 is connected to a coke oven fuel gas supply pipe 40, and the coke oven fuel gas is introduced into the heat storage chamber 30 via the coke oven fuel gas supply pipe 40. Furthermore, the coke oven 100 is provided with a flue (not shown) for discharging exhaust gas generated by the combustion of coke oven fuel gas in the combustion chamber 20, and the exhaust gas is discharged to the outside through the chimney via the flue.

[0027] In Figure 1, either alternative MG, MG, or COG is used as the coke oven fuel gas. Alternative MG and MG are supplied directly to the coke oven fuel gas supply pipe 40 and introduced into the heat storage chamber 30 and the combustion chamber 20. COG is generally introduced directly into the combustion chamber 20 through a dedicated gas channel, bypassing the heat storage chamber 30. The reason for this will be explained later.

[0028] Normally, MG is used as the fuel gas for coke ovens. However, as mentioned above, if the blast furnace is shut down, or if coke oven operations are stopped for an extended period due to unexpected natural disasters or major problems, the supply of either BFG or COG, which are raw materials for MG, or both, will be stopped. In such cases, alternative MG is used to maintain the temperature of the coke oven. The following describes the method for maintaining the temperature of a coke oven when alternative MG is used (the method for maintaining the temperature of a coke oven as disclosed herein).

[0029] As described above, the alternative MG gas is supplied to the heat storage chamber 30 through the coke oven fuel gas supply pipe 40, where it is preheated and then sent to the combustion chamber 20. However, depending on the composition of the alternative MG, thermal decomposition may occur in the gas ports of the heat storage chamber 30 and the combustion chamber 20, resulting in coking.

[0030] Therefore, in the coke oven heat retention method of this disclosure, the alternative MG is burned at an air ratio such that the residual oxygen in the exhaust gas is 5 vol.% or more and 15 vol.% or less. As a result, even if coking occurs in the gas port of the heat storage chamber 30 or the combustion chamber 20 due to the thermal decomposition of the alternative MG gas, the precipitated carbon can be incinerated by the residual oxygen in the exhaust gas, thereby suppressing the occurrence of coking.

[0031] When alternative MG is burned at an air ratio that results in less than 5 vol.% residual oxygen in the exhaust gas, the incineration efficiency of the precipitated carbon decreases. When alternative MG is burned at an air ratio that results in more than 15 vol.% residual oxygen in the exhaust gas, the amount of air supplied increases, leading to increased costs and concerns about changes in combustion rate and NOx generation. From this perspective, alternative MG may be burned at an air ratio that results in 10 vol.% or less residual oxygen in the exhaust gas.

[0032] Here, "exhaust gas residual oxygen of 5 vol.% or more and 15 vol.% or less" means that the average value of residual oxygen in the exhaust gas during operation (combustion) is in the range of 5 vol.% or more and 15 vol.% or less. Similarly, regarding the lower heating value of the coke oven alternative fuel gas, the average value of the lower heating value of the coke oven alternative fuel gas during operation (combustion) is 500 to 3000 kcal / Nm³. 3 This means it falls within a certain range.

[0033] The residual oxygen in the exhaust gas can be continuously measured by physical analysis methods such as electrochemical or magnetic methods. Furthermore, the air-to-air ratio at which the residual oxygen in the exhaust gas reaches a predetermined percentage can be calculated from combustion calculations. Here, the air-to-air ratio is the ratio indicating the amount of air required for the complete combustion of the fuel (e.g., alternative MG). The air is generally introduced into the combustion chamber 20 after heat exchange via the heat storage chamber 30.

[0034] <Method of supplying alternative MG> There are two methods for introducing the alternative MG into the heat storage chamber 30. First, the alternative MG, which is manufactured by pre-mixing the gases constituting the alternative MG, is directly supplied to the coke oven fuel gas supply pipe 40 and introduced into the heat storage chamber 30. Second, each of the gases constituting the alternative MG is directly supplied to the coke oven fuel gas supply pipe 40, and the alternative MG obtained by mixing in the coke oven fuel gas supply pipe 40 is introduced into the heat storage chamber 30. Figure 1 shows the introduction of the alternative MG into the heat storage chamber 30 using the former method.

[0035] From the viewpoint of uniformly mixing the gases constituting the alternative MG (reducing the concentration deviation of the gases constituting the alternative MG), a method may be used in which the alternative MG, manufactured by pre-mixing the gases constituting the alternative MG, is directly supplied to the coke oven fuel gas supply pipe 40 and introduced into the heat storage chamber 30. The method of pre-mixing the gases constituting the alternative MG is not particularly limited, but from the viewpoint of more uniform mixing, the gases may be mixed while disturbing the flow in a flow path via a porous plate. Such mixing can be carried out using a predetermined pre-mixing device.

[0036] The reasons for supplying the alternative MG or the gas constituting the alternative MG directly to the coke oven fuel gas supply piping 40 are as follows:

[0037] Typically, coke ovens have the challenge of not being able to quickly change the type of fuel due to their furnace structure. For example, when switching the fuel used from MG to COG, simply introducing COG into the coke oven fuel gas supply piping 40 is considered impossible for two main reasons: (1) If COG is introduced directly into the heat storage chamber 30, the contained hydrocarbon gases may cause thermal decomposition and carbon deposition, potentially clogging the heat storage bricks 31. (2) The stoichiometric air volume differs by about twice between MG and COG. For these reasons, the supply systems for MG and COG to the combustion chamber 20 are usually separate, and switching between these systems, as well as adjusting the air ratio, requires considerable time and effort. Therefore, the alternative MG used must be capable of operating at the same air ratio as the normally used MG and must be designed so as not to cause clogging when supplied to the heat storage chamber.

[0038] As a result of sincere consideration of the technical problems, the inventors have found an operational method in which the first gas is diluted with an inert gas and / or a second gas to the equivalent of a normal MG to reduce its calorific value, supplied to the existing MG line (coke oven fuel gas supply piping 40), supplied to the combustion chamber 20 via the heat storage chamber 30, and the combustion is operated at a predetermined air ratio, thereby enabling the burning of trace amounts of precipitated carbon by residual oxygen in the exhaust gas. This makes it possible to easily introduce an alternative MG into the combustion chamber 20 without switching the gas supply system, and to quickly and safely heat and maintain the temperature of the coke oven 100.

[0039] The method for maintaining the temperature of a coke oven according to this disclosure has been described above. According to the method for maintaining the temperature of a coke oven according to this disclosure, it is possible to maintain the temperature of the coke oven while suppressing coking. [Examples]

[0040] The present disclosure will be further explained below using examples.

[0041] (1) Coking characteristics of by-product gases and alternative gases To evaluate the coking characteristics of the alternative gas, the test system shown in Figure 2 was constructed. The experimental conditions are shown in Table 1. The alternative MG used had a localized heating value of 9700 kcal / Nm³.3 Approximately 1050 kcal / Nm³ of natural gas 3 The gas used was diluted with nitrogen to a certain extent.

[0042] [Table 1]

[0043] As shown in Figure 2, the test gas is diluted with nitrogen according to the test requirements and supplied to the heating tube. The heating tube is made of SUS314 stainless steel, and the circulating gas and test specimens are heated to a predetermined test temperature using an electric resistance furnace. For coking characteristics, a test specimen (made of SUS stainless steel, 10 x 33 mm, t=2 mm) placed on the outlet side of the heating tube was exposed to the heated gas for a certain period of time, and the amount of coking was evaluated by the change in weight before and after the test.

[0044] Figure 3 shows the weight change of SUS test specimens after 3600 seconds of exposure at 100°C intervals within the range of 700 to 1000°C. As shown in Figure 3, the precipitate weight remained almost unchanged regardless of the gas type up to around 800°C, but a discrepancy in precipitate weight was observed above 900°C. From this, it is considered that the thermal decomposition start temperature for both MG and the alternative MG is around 800 to 900°C. Furthermore, the experiment suggests that a certain amount of precipitate may be generated when the alternative MG is preheated to a high temperature.

[0045] (2) Incineration of carbon produced as a by-product of caulking A magnetic tube (φ8.9; cross-sectional area 26.4 mm²) preheated to 900°C where caulking may occur. 2 ) with a localized heating capacity of 9700 kcal / Nm 3 Approximately 1050 kcal / Nm³ of natural gas 3 We attempted to incinerate carbon that had been intentionally precipitated by circulating a gas (alternative MG) diluted with nitrogen to a certain degree for a certain period of time. During this process, incineration was carried out at an air ratio that resulted in a residual oxygen content of 5.0 vol.% in the exhaust gas. The results are shown in Figure 4.

[0046] As shown in Figure 4, we confirmed that the precipitate after circulating the alternative MG for 24 hours (approximately 4% occlusion point) was incinerated in about 5 minutes. In addition, as a control test, we confirmed that the precipitate after circulating COG for 5 hours (approximately 60% occlusion point) was also incinerated in about 15 minutes.

[0047] On the other hand, the inventors have found that incineration performance deteriorates under conditions where the O2 concentration falls below 3.0 vol.%. Tests were conducted to incinerate carbon precipitates with almost identical blockage origins at air ratios where the residual oxygen in the exhaust gas was 0.5 vol.%, 3 vol.%, or 5 vol.%. The incineration rate estimated from the flow path cross-sectional area after 20 minutes is shown in Figure 5. It was confirmed that the incineration characteristics deteriorate significantly when the residual oxygen in the exhaust gas falls below 3 vol.%. Therefore, since the actual thermal storage chamber is a high-temperature environment of 900°C or higher and gas preheating and exhaust gas heat storage are switched every 20-30 minutes, it was suggested that precipitated carbon can be incinerated to a reasonable extent by operating at an air ratio that results in a residual oxygen in the exhaust gas of 5.0 vol.% or higher.

[0048] (3) Actual machine testing The alternative MG was experimentally supplied to an operating coke oven, and the combustion state was confirmed. The coke oven used was the one shown in Figure 1. The gas used in the test had a fixed heating value of 9700 kcal / Nm³. 3 By controlling the mixing ratio of nitrogen to natural gas at approximately 90% and pre-mixing it in a channel through a porous plate while disrupting the flow, a yield of 1050 kcal / Nm³ is achieved. 3 A comparable substitute MG was manufactured, then depressurized to the equivalent of a normal MG and supplied to the coke oven's fuel gas supply piping, and introduced into the combustion chamber via the heat storage chamber.

[0049] Figure 6 shows the LNG mixing ratio and the supply status of the alternative MG. The gas calories calculated from the flow rate ratio control (solid line) and the calories calculated from the compositional analysis of the test gas by gas chromatography (●) are in general agreement, and it was determined that the specified gas was being manufactured and supplied. At this time, flame formation was observed in the combustion chamber, and the self-ignition and combustion of the alternative MG in the combustion chamber were visually confirmed using the proposed alternative gas and its supply method.

[0050] Furthermore, in this test, the aim was to suppress carbon deposition during the preheating process of the heat storage chamber by operating with a high air-to-air ratio so that the residual oxygen in the exhaust gas was 5 vol.% or higher. Figure 7 shows the time history of the residual oxygen concentration in the exhaust gas during the test. These results are measurement data from one combustion chamber row (heat storage and heat release are repeated by switching combustion approximately every 30 minutes), and focusing on the data during exhaust (heat storage), it was confirmed that operation was generally performed at a high air-to-air ratio of approximately 10 vol.%, which was the target, and no blockages occurred in the test section.

[0051] Furthermore, when chamotte brick pieces, which had carbon deposited on their surface due to the thermal decomposition of gas beforehand, were inserted into the upper space of the actual thermal storage chamber and exposed to exhaust gas at an oxygen concentration of 10 vol.% and a gas temperature of 900°C for 30 minutes, the burning of the carbon on the surface was visually observed as shown in Figure 8, and a weight reduction of about 2-3% was also confirmed, confirming the coking suppression effect. [Explanation of Symbols]

[0052] 10 Carbonization Chamber 20 Combustion chamber 30 Heat storage chamber 31 Heat-storing bricks 40 Coke oven fuel gas supply piping 100 coke ovens

Claims

1. Lower heating value: 6,000–25,000 kcal / Nm ３ The first gas, an inert gas, and a lower heating value of 500 to 3000 kcal / Nm ３ It includes at least one of the second gases, Lower heating value is 500-3000 kcal / Nm ３ Therefore, the alternative fuel gas for coke ovens is The fuel is introduced into the combustion chamber via a heat storage chamber, and combustion is performed at an air ratio such that the residual oxygen in the exhaust gas is between 5 vol.% and 15 vol.%. Methods for maintaining the temperature of a coke oven.

2. The coke oven substitute fuel gas, which is manufactured by pre-mixing the gases constituting the coke oven substitute fuel gas, is directly supplied to the coke oven fuel gas supply piping and introduced into the heat storage chamber, or, Each of the gases constituting the coke oven alternative fuel gas is directly supplied to the coke oven fuel gas supply pipe, and the coke oven alternative fuel gas obtained by mixing in the coke oven fuel gas supply pipe is introduced into the heat storage chamber. The method for maintaining the temperature of a coke oven according to claim 1.

Images