Cement plant exhaust heat recovery system

Abstract

To provide a cement plant exhaust heat recovery system that can effectively utilize exhaust heat generated in a cement plant.SOLUTION: A cement plant exhaust heat recovery system is configured to recover exhaust heat in a cement plant, and comprises: a PH boiler for generating steam by using exhaust gas exhausted from a preheater of the cement plant, as a heat source; an exhaust gas line for guiding the exhaust gas exhausted from the PH boiler, as a heat source for drying a cement raw material, to a cement raw material mill of the cement plant; an exhaust gas damper arranged in the exhaust gas line; and a branch exhaust gas line branching from the exhaust gas line upstream of the exhaust gas damper.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a cement plant exhaust heat recovery system that recovers exhaust heat from a cement plant. [Background technology]

[0002] A cement plant is equipped with a preheater that preliminarily heats the cement raw materials, a kiln (calciner) that further heats the cement raw materials discharged from the preheater, and an air quenching cooler (AQC) that sends cooling air to the calcined product produced in the kiln. The preheater heats the cement raw materials using exhaust gas generated in the calciner (auxiliary combustion furnace) as a heat source.

[0003] Exhaust heat generated in a cement plant is used to generate steam by a heat recovery boiler, and the generated steam is supplied to a steam turbine to generate electricity (see, for example, Patent Document 1). Exhaust heat recovery boilers include air quenching boilers (AQC boilers) that use the AQC exhaust gas discharged from an air quenching cooler as a heat source, and preheater boilers (PH boilers) that use the exhaust gas discharged from a preheater as a heat source. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4478674 Summary of the Invention [Problem to be solved by the invention]

[0005] It is preferable to reuse as much of the waste heat generated in the cement plant as possible.

[0006] An object of the present disclosure is to provide a cement plant exhaust heat recovery system that can effectively utilize exhaust heat generated in a cement plant. [Means for solving the problem]

[0007] A cement plant exhaust heat recovery system according to at least one embodiment of the present disclosure includes: A cement plant exhaust heat recovery system for recovering exhaust heat from a cement plant, comprising: a PH boiler for generating steam using exhaust gas discharged from a preheater of the cement plant as a heat source; an exhaust gas line for introducing the exhaust gas discharged from the PH boiler to a cement raw material mill of the cement plant as a heat source for drying the cement raw material; an exhaust gas damper disposed in the exhaust gas line; a branch exhaust gas line branching off from the exhaust gas line upstream of the exhaust gas damper; Equipped with. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a cement plant exhaust heat recovery system that can effectively utilize exhaust heat generated in a cement plant. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a cement plant exhaust heat recovery system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the cement plant exhaust heat recovery system of FIG. 1. [Diagram 3] FIG. 3 is a schematic diagram showing a more specific example of the cement plant exhaust heat recovery system of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0011] <Outline of Cement Plant Exhaust Heat Recovery System 1> As shown in FIG. 1, a cement plant exhaust heat recovery system 1 includes a cement plant 2 that produces cement from cement raw materials, and an exhaust heat recovery system 3 that recovers exhaust heat from the cement plant 2.

[0012] The cement plant 2 includes a cement raw material mill 11 for drying and grinding cement raw materials composed of limestone, clay, etc., a preheater 13 for preheating the ground granulated cement raw materials with combustion gas, a kiln 18 for burning the preheated cement raw materials, an air quenching cooler 21 for producing clinker as an intermediate product by supplying cooling air to the burned product produced in the kiln 18, and a cement mill 22 for producing finely powdered cement by grinding the clinker mixed with gypsum. Gypsum is mixed in to delay the solidification of the cement.

[0013] The cement plant 2 is provided with a calciner 14 for supplying combustion gas to the preheater 13, and coal (pulverized coal) is supplied from a coal mill 17 to a calcination burner 15 of the calciner 14. Combustion gas generated by the combustion in the calciner 14 of the pulverized coal injected from the calcination burner 15 and combustion exhaust gas generated by the combustion of waste plastics in the kiln 18 flow toward the preheater 13. The coal mill 17 also supplies pulverized coal to a kiln burner 19 that constitutes the kiln 18.

[0014] The combustion gas used as a heat source in the preheater 13 is supplied as exhaust gas to the exhaust heat recovery system 3. In addition, the cooling air supplied to the air quenching cooler 21 becomes AQC exhaust gas through heat exchange with the fired product, and a part of the AQC exhaust gas is supplied to the kiln 18 and the calcination burner 15 as combustion air (not shown). The remaining AQC exhaust gas is supplied to the exhaust heat recovery system. There are no particular limitations on the use of the exhaust heat recovered by the exhaust heat recovery system 3 from the PH exhaust gas and the AQC exhaust gas, but in this example, the recovered exhaust heat is used to generate power.

[0015] The exhaust heat recovery system 3 that functions as a power generation system will be described. The exhaust heat recovery system 3 further includes a PH boiler 20 for generating steam using exhaust gas discharged from a preheater 13 as a heat source, a steam turbine 31 for rotating using the steam as a driving source, a generator 32 connected to the steam turbine 31, and a condenser 33 for condensing the steam discharged from the steam turbine 31. The condensate (hereinafter, sometimes referred to as feed water) discharged from the condenser 33 is supplied to an AQC boiler 30 (described later).

[0016] The exhaust heat recovery system 3 includes an AQC boiler 30 for heating feed water using the AQC exhaust gas discharged from the air quenching cooler 21 as a heat source. The AQC heating fluid heat-exchanged in the AQC boiler 30 may be any of hot water, steam, or superheated steam. For example, when the AQC boiler 30 is composed of only an economizer 35 (see FIG. 3), the AQC heating fluid is hot water. For another example, an AQC evaporator (not shown) and an AQC superheater (not shown) may be provided in the AQC boiler 30 in addition to the economizer 35. In this case, the superheated steam discharged from the AQC superheater toward the PH boiler 20 may be the AQC heating fluid. However, a part of the hot water discharged from the economizer 35 may be supplied to another heat exchanger as the AQC heating fluid without being supplied to the AQC evaporator. In other words, the AQC heating fluid discharged from the AQC boiler 30 may be supplied to the steam turbine 31 via the PH boiler 20, or may be supplied to the steam turbine 31 via another heating system, or a combination of these may be used (details will be described later).

[0017] In the example of Fig. 1, the exhaust heat utilized in the exhaust heat recovery system 3 is further utilized. Specifically, an exhaust gas line 7 is provided for supplying the exhaust gas discharged from the PH boiler 20 to a cement raw material mill 11. The cement raw material mill 11 utilizes the exhaust gas as a heat source for drying the cement raw material. In addition, an exhaust gas damper 8 is disposed in the exhaust gas line 7, and the flow rate of the exhaust gas supplied to the cement raw material mill 11 is adjusted by controlling the opening degree of the exhaust gas damper 8.

[0018] In this embodiment, a branch exhaust gas line 9 is further provided, which branches off from the exhaust gas line 7 upstream of the exhaust gas damper 8. The branch exhaust gas line 9 includes a first branch exhaust gas line 9a and a second branch exhaust gas line 9b arranged in parallel to each other. The first branch exhaust gas line 9a is adapted to guide the exhaust gas to the heat recovery device 5, and the second branch exhaust gas line 9b is adapted to guide the exhaust gas to the humidity control tower 16. A first branch exhaust gas damper 6a and a second exhaust gas branch damper 6b are arranged in the first branch exhaust gas line 9a and the second branch exhaust gas line 9b, respectively.

[0019] The heat recovery device 5 is not particularly limited as long as it is a device that recovers heat from exhaust gas (a specific configuration will be described later). The humidity control tower 16 is configured to collect dust contained in the exhaust gas, for example, by using spray water, to lower the temperature. In the example of FIG. 1, the amount of exhaust gas required in the heat recovery device 5 flows through the first branch exhaust gas line 9a, and the excess amount of exhaust gas flows through the second branch exhaust gas line 9b. The flow rate of the exhaust gas flowing into each of the heat recovery device 5 and the humidity control tower 16 is distributed by adjusting the opening degree of the first branch exhaust gas damper 6a and the second branch exhaust gas damper 6b. The exhaust gas that has passed through each of the humidity control tower 16, the heat recovery device 5, and the cement raw material mill 11 is subjected to dust collection treatment and the like before being released into the atmosphere (a detailed description of which is omitted in this paper).

[0020] The inventors of the present application have focused on the fact that not all of the exhaust gas discharged from the PH boiler 20 is necessarily required as a heat source for drying the cement raw materials. In other words, they have focused on the fact that it is not necessarily necessary to flow all of the exhaust gas that has passed through the PH boiler 20 into the exhaust gas line 7. For example, when the moisture content of the cement raw materials is relatively low, or when the amount of cement raw materials input to the preheater 13 is relatively small, the amount of exhaust gas required as a heat source for drying is reduced. In this regard, according to the above-mentioned configuration, when there is excess exhaust gas that does not need to be supplied to the exhaust gas line 7, the excess exhaust gas can be flowed into the first branch exhaust gas line 9a and the second branch exhaust gas line 9b through the opening control of the exhaust gas damper 8. This makes it possible to effectively utilize the exhaust heat that has passed through the PH boiler 20. Thus, a cement plant exhaust heat recovery system 1 that can effectively utilize the exhaust heat generated in the cement plant 2 is realized.

[0021] <Control of exhaust gas damper 8 opening> 1, the control of the opening degree of the exhaust gas damper 8 will be described. The controller 90, which is a component of the cement plant exhaust heat recovery system 1, includes a damper control unit 91 for controlling the opening degree of the exhaust gas damper 8. The damper control unit 91 is configured to control the opening degree of the exhaust gas damper 8 based on raw material mill operation parameters that indicate the operating state of the cement raw material mill 11. All of the raw material mill operation parameters change depending on the amount of cement raw material supplied to the cement raw material mill 11 or the moisture content of the cement raw material.

[0022] For example, the raw material mill operation parameters include the state quantity of the hydraulic cylinder 11a of the cement raw material mill 11 (hydraulic pressure as a more specific example) and the temperature of the exhaust gas discharged from the cement raw material mill 11. The temperature of the exhaust gas discharged from the cement raw material mill 11 is measured by an exhaust gas temperature sensor (not shown). These measurement results are sent to the damper control unit 91.

[0023] The damper control unit 91 applies the raw material mill operation parameters to a predetermined function formula to determine the opening degree of the exhaust gas damper 8. Then, a command for realizing the determined opening degree is sent from the damper control unit 91 to the exhaust gas damper 8. The damper control unit 91 may use a data table instead of the function formula. The data table may associate multiple patterns of parameter values ​​(e.g., multiple patterns of moisture content obtained by analysis) with multiple patterns of opening degrees of the exhaust gas damper 8, and the damper control unit 91 may identify the opening degree corresponding to the acquired parameter from the data table.

[0024] Furthermore, the above-mentioned function formula or data table may be corrected afterwards. For example, the correlation between various process quantities accumulated with the operation of the cement plant exhaust heat recovery system 1 and the moisture content of the cement raw material may be analyzed, and the analysis results may be reflected in the function formula or data table. In response to the reflection, for example, the coefficients constituting the function formula are corrected. The above-mentioned various process quantities include the driving oil pressure of the hydraulic cylinder 11a of the cement raw material mill 11, the raw material mill differential pressure, the temperature of the exhaust gas discharged from the cement raw material mill 11, and the like.

[0025] According to the inventor's knowledge, the raw material mill operation parameters change depending on the moisture content of the cement raw materials fed into the preheater 13 and / or the amount of the cement raw materials fed into the preheater 13. According to the above configuration, the opening degree of the exhaust gas damper 8 is controlled based on these parameters, so that more of the surplus exhaust gas that is not used as a heat source for drying the cement raw materials can flow into the branch exhaust gas line 9.

[0026] For example, when both the moisture content of the cement raw materials and the input amount of the cement raw materials decrease, the calorific value of the drying exhaust gas required in the cement raw materials mill 11 decreases, and as a result, the temperature of the exhaust gas from the cement raw materials mill 11 increases. The damper control unit 91 specifies the opening degree of the exhaust gas damper 8 according to the increase in the temperature of the exhaust gas (the specified damper opening degree is smaller than the opening degree of the exhaust gas damper 8 before the decrease in the moisture content and input amount occurs). Then, a command to realize the specified opening degree is sent from the damper control unit 91 to the exhaust gas damper 8, and the opening degree of the exhaust gas damper 8 becomes the opening degree according to the decrease in the moisture content and input amount. As a result, the flow rate of the exhaust gas flowing into the cement raw materials mill 11 decreases, and the flow rate of the exhaust gas flowing through the branch exhaust gas line 9 can be increased, making it possible to increase the heat recovered by the heat recovery device 5.

[0027] <Example of Cement Plant Exhaust Heat Recovery System 1> Fig. 2 is a schematic diagram showing a more specific example of the cement plant exhaust heat recovery system 1 of Fig. 1. As shown in the figure, the exhaust heat recovery system 3 includes a water supply line 40 through which the feedwater discharged from the condenser 33 flows. The water supply line 40 includes an AQC water supply line 43. The AQC water supply line 43 is configured to guide the feedwater discharged from the condenser 33 to the AQC boiler 30. Furthermore, the water supply line 40 includes a heat exchange water supply line 44 for guiding the feedwater extracted from the AQC water supply line 43 to the heat exchanger 50.

[0028] Here, the heat exchanger 50 is configured to generate hot water from feed water using the exhaust gas flowing through the branch exhaust gas line 9 as a heat source. More specifically, the heat exchanger 50 is an economizer 51 forming a part of the PH boiler 20, and the economizer 51 is configured with a heat transfer tube (hereinafter, may be simply referred to as a heat transfer tube) arranged inside the branch exhaust gas line 9. The feed water introduced by the heat exchange feed water line 44 flows through the heat transfer tube. The heat transfer tube constituting the economizer 51 is located upstream of the first branch exhaust gas line 9a and the second branch exhaust gas line 9b. The heat exchanger 50 is configured to heat the feed water through heat exchange between the exhaust gas flowing through the branch exhaust gas line 9 and the feed water supplied to the heat transfer tube.

[0029] The hot water discharged from the heat exchanger 50 is guided to another device through a hot water discharge line 61. The device may be anything that uses hot water as a heat source, and one example is a flasher 73 (see FIG. 3) described below.

[0030] 2, a bypass line 62 is provided that connects the hot water discharge line 61 and the heat exchange water supply line 44. The bypass line 62 is configured to guide the feed water extracted from the heat exchange water supply line 44 to the hot water discharge line 61, bypassing the heat exchanger 50. In addition, a bypass flow control valve 63 is disposed in the bypass line 62, and the ratio between the amount of feed water supplied to the heat transfer tube and the amount of feed water flowing through the bypass line 62 is determined according to the opening degree of the bypass flow control valve 63.

[0031] At least a part of the exhaust gas that has passed through the heat transfer tubes of the economizer 51 flows through the first branch exhaust gas line 9a of the branch exhaust gas line 9 and into the heat recovery device 5. FIG. 2 illustrates an embodiment in which the heat recovery device 5 is a coal mill 17, and the exhaust gas flowing through the first branch exhaust gas line 9a is used as a heat source for drying coal used in the coal mill 17. More specifically, the exhaust gas flowing through the first branch exhaust gas line 9a is used as a heat source for drying coal used by the kiln burner 19 (see FIG. 1) and the calcination burner 15 (see FIG. 1).

[0032] The controller 90 illustrated in Fig. 2 includes a bypass flow regulation valve control unit 92 for controlling the aperture of the bypass flow regulation valve 63. It is preferable that the temperature of the exhaust gas supplied to the coal mill 17 falls within a certain range (for example, 165°C or higher). On the other hand, the calorific value of the exhaust gas discharged per unit time from the PH boiler 20 varies depending on the operating state of the cement plant 2. Therefore, the bypass flow regulation valve control unit 92 is adapted to control the aperture of the bypass flow regulation valve 63 based on the measured value of the temperature of the exhaust gas flowing through the first branch exhaust gas line 9a.

[0033] For example, the first branch exhaust gas line 9a is provided with a first exhaust gas temperature sensor 121 for measuring the temperature of the exhaust gas, and the measurement value of the first exhaust gas temperature sensor 121 is sent to the bypass flow regulation valve control unit 92. If the measurement value is below an allowable temperature (for example, 165°C), the bypass flow regulation valve control unit 92 sends a command to the bypass flow regulation valve 63 to increase the opening degree. This reduces the amount of feed water flowing into the heat transfer tube of the economizer 51, and makes it possible to increase the temperature of the exhaust gas flowing through the first branch exhaust gas line 9a.

[0034] As described above, the cement plant exhaust heat recovery system 1 includes the heat exchanger 50. According to this configuration, the heat exchanger 50 can generate hot water from feed water by utilizing the exhaust heat of the exhaust gas. This allows the exhaust heat of the exhaust gas to be transferred to the hot water and used separately as various heat sources.

[0035] As described above, the heat recovery device 5 is the coal mill 17. According to this configuration, the heat source of the exhaust gas flowing through the branch exhaust gas line 9 can be used as a drying heat source for the coal mill 17. In particular, in the embodiment in which the exhaust gas that has passed through the heat transfer tubes that constitute the economizer 51 is supplied to the coal mill 17, the following technical advantages can be obtained. That is, the temperature of the exhaust gas flowing into the coal mill 17 needs to be 165°C or higher, but the temperature of the exhaust gas discharged from the PH boiler 20 is about 250°C. In other words, at the stage before the exhaust gas flowing from the PH boiler 20 to the branch exhaust gas line 9 reaches the coal mill 17, the surplus exhaust heat contained in the exhaust gas can be recovered from about 250°C to 165°C by the heat exchanger 50. This allows the exhaust heat of the exhaust gas to be used more effectively.

[0036] Furthermore, the cement plant exhaust heat recovery system 1 includes a hot water discharge line 61, a bypass line 62, and a bypass flow regulation valve 63. According to this configuration, the flow rate of the feed water supplied to the heat exchanger 50 can be adjusted by adjusting the opening degree of the bypass flow regulation valve 63, so that the amount of heat exchanged in the heat exchanger 50 can be adjusted according to the operating state of the cement plant 2. Therefore, even if the operating state of the cement plant 2 fluctuates, the temperature of the exhaust gas supplied to the coal mill 17 can be kept within a certain range.

[0037] <Further concrete example of cement plant exhaust heat recovery system 1> FIG. 3 is a schematic diagram showing an example further specific to FIG. 2. Hot water discharged from the heat exchanger 50 is led to the water tank 55 by the hot water discharge line 61. The water tank 55 stores the hot water. The hot water discharged from the water tank 55 is subjected to pressure reduction treatment by the flasher 73, separated into steam and drain, and supplied to the steam turbine 31. That is, the steam supply system shown in the example of FIG. 3 is composed of a first steam supply line 71 for leading the superheated steam discharged from the PH boiler 20 to the steam turbine 31 as the first working medium, and a second steam supply line 72 for leading the medium-low pressure steam generated by the flasher 73 to the steam turbine 31 as the second working medium. The drain separated in the flasher 73 flows into the heat exchange feed water line 44 via the return path 75. In FIG. 3, the feed water extracted from the AQC feed water line 43 flows into the flasher 73 via the branch line 49.

[0038] According to the configuration in which the cement plant exhaust heat recovery system 1 includes the water tank 55, hot water generated in the heat exchanger 50 by utilizing the exhaust heat of the exhaust gas flowing through the branch exhaust gas line 9 can be stored in the water tank 55. This makes it possible to effectively utilize the exhaust heat of the exhaust gas.

[0039] According to a configuration in which the cement plant exhaust heat recovery system 1 includes the second steam supply line 72 in addition to the first steam supply line 71, steam can be separated from the hot water stored in the water tank 55 and supplied as the second working medium to the steam turbine 31. Since the second working medium is supplied to the steam turbine 31 in addition to the first working medium, the output of the steam turbine 31 can be improved by utilizing the exhaust heat of the exhaust gas, and the amount of power generation of the exhaust heat recovery system 3 can be increased.

[0040] The cement plant exhaust heat recovery system 1 will be described further with reference to Fig. 3. The AQC boiler 30 includes an economizer 35 for generating hot water (AQC heating fluid) from feedwater guided by an AQC feedwater line 43. The economizer 35 is configured to utilize the AQC exhaust gas discharged from the air quenching cooler 21 as a heat source.

[0041] In the example of FIG. 3, a PH hot water supply line 36 is provided for conducting hot water discharged from an economizer 35 of the AQC boiler 30 to the PH boiler 20.

[0042] The PH boiler 20 illustrated in Fig. 3 includes an evaporator 23 for heating feedwater and a superheater 24 for generating superheated steam from the feedwater. Steam discharged from the evaporator 23 flows into the superheater 24. The superheated steam generated by the superheater 24 is guided to the steam turbine 31 via a first steam supply line 71.

[0043] 3, a hot water extraction line 37 is further provided for extracting hot water from the PH hot water supply line 36 and directing the hot water to a water tank 55. The hot water flowing through the hot water extraction line 37 flows into a flasher 73 via the water tank 55.

[0044] The hot water extraction line 37 is provided with a hot water extraction on-off valve 38 and a hot water extraction flow control valve 39. In addition, a flow meter 111 is provided for measuring the flow rate of hot water flowing through the PH hot water supply line 36. The flow meter 111 is located in the PH hot water supply line 36 downstream of the connection point C1 between the PH hot water supply line 36 and the hot water extraction line 37.

[0045] 3, the controller 90 includes a hot water flow control valve control unit 93 configured to control the opening degree of the hot water extraction flow control valve 39. The hot water flow control valve control unit 93 is configured to send a control command to the hot water extraction flow control valve 39 to increase the opening degree of the hot water extraction flow control valve 39 when the flow rate of the hot water measured by the flow meter 111 becomes equal to or greater than a specified flow rate.

[0046] The flow rate of hot water to be supplied from the PH hot water supply line 36 to the PH boiler 20 is determined in advance according to the operating state of the cement plant 2. This is because at least a part of the exhaust gas discharged from the PH boiler 20 needs to be supplied to the cement raw material mill 11, and the temperature of the exhaust gas needs to be set to about 250°C or higher. Therefore, when the flow rate of hot water flowing through the PH hot water supply line 36 becomes relatively large due to fluctuations in the operating state of the AQC boiler 30, excess hot water is generated. Therefore, when the measurement value of the flowmeter 111 is equal to or greater than a specified flow rate, the hot water flow control valve control unit 93 determines that excess hot water is flowing through the PH hot water supply line 36, and sends a command to the hot water extraction flow control valve 39 to increase the opening degree.

[0047] According to the above configuration, of the hot water discharged from the AQC boiler 30, surplus hot water that does not need to be supplied to the PH boiler 20 can be supplied to the water tank 55. In other words, surplus hot water generated according to the operating state of the AQC boiler 30 can be stored in the water tank 55. This allows the waste heat generated in the cement plant 2 to be utilized more effectively.

[0048] In addition, since the hot water flow control valve control unit 93 controls the hot water extraction flow control valve 39, when surplus hot water is generated that does not need to be supplied to the PH boiler 20, the surplus hot water can be automatically supplied to the water tank 55. The AQC exhaust heat can be effectively stored in the form of hot water even in the event of load fluctuations, which can contribute to the leveling out of the power generation load.

[0049] 3, the AQC boiler 30 includes one economizer 35, but the present disclosure is not limited thereto. For example, a plurality of economizers 35 may be arranged in parallel with each other. Alternatively, the AQC boiler 30 may further include an AQC evaporator (not shown) for generating steam from the hot water generated by the economizer 35, and an AQC superheater (not shown) for generating superheated steam from the steam.

[0050] <Other> 1, the controller 90 is illustrated as a component of the exhaust heat recovery system 3, but this is merely an example, and the controller 90 may be a component of the cement plant 2. Alternatively, the controller 90 may be realized by a plurality of DCS panels arranged in each of the cement plant 2 and the exhaust heat recovery system 3.

[0051] The controller 90 is configured by a computer, and includes a processor, a memory (storage medium), and an external communication interface. The processor is a CPU, a GPU, an MPU, a DSP, or a combination thereof. The processor according to other embodiments may be realized by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to store various data temporarily or non-temporarily, and is realized by at least one of a RAM, a ROM, and a flash memory, for example. The processor executes various control processes according to instructions of a program loaded into the memory.

[0052] <Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0053] 1) At least one embodiment of the cement plant exhaust heat recovery system (1) according to the present disclosure includes: A cement plant exhaust heat recovery system for recovering exhaust heat from a cement plant (2), comprising: a PH boiler (20) for generating steam using exhaust gas discharged from a preheater (13) of the cement plant as a heat source; an exhaust gas line (7) for introducing the exhaust gas discharged from the PH boiler to a cement raw material mill (11) of the cement plant as a heat source for drying cement raw materials; an exhaust gas damper (8) disposed in the exhaust gas line; a branch exhaust gas line (9) branching off from the exhaust gas line upstream of the exhaust gas damper; Equipped with.

[0054] The inventors of the present application have noticed that not all of the exhaust gas discharged from the PH boiler is necessarily required as a heat source for drying the cement raw materials. For example, when the moisture content of the cement raw materials is relatively low, or when the amount of cement raw materials fed to the preheater is relatively small, the amount of exhaust gas required as a heat source for drying is reduced. In this regard, according to the configuration of 1) above, when there is excess exhaust gas that does not need to be supplied to the exhaust gas line, the exhaust gas can be made to flow into the branch exhaust gas line by controlling the opening degree of the exhaust gas damper. This makes it possible to effectively utilize the exhaust heat of the exhaust gas that has passed through the PH boiler. Thus, a cement plant exhaust heat recovery system that can effectively utilize the exhaust heat generated in the cement plant is realized.

[0055] 2) In some embodiments, the cement plant exhaust heat recovery system described in 1) above includes: The mill further includes a damper control unit (91) configured to control the opening degree of the exhaust gas damper based on a raw material mill operation parameter indicating an operation state of the cement raw material mill.

[0056] According to the inventor's knowledge, the raw material mill operation parameters change depending on the moisture content of the cement raw materials fed into the preheater and / or the amount of cement raw materials fed into the preheater. According to the configuration of 2) above, the opening degree of the exhaust gas damper is controlled based on the raw material mill operation parameters, so that more of the surplus exhaust gas not required as a heat source for drying the cement raw materials can flow into the branch exhaust gas line.

[0057] 3) In some embodiments, the cement plant exhaust heat recovery system according to 1) or 2) above, The system further includes a heat exchanger (50) including a heat transfer tube (a heat transfer tube constituting an economizer 51) arranged inside the branch exhaust gas line, the heat exchanger (50) being configured to heat the feed water through heat exchange between the exhaust gas flowing through the branch exhaust gas line and the feed water supplied to the heat transfer tube.

[0058] According to the above configuration 3), the heat exchanger can generate hot water from the feed water by utilizing the waste heat contained in the exhaust gas. This allows the waste heat of the exhaust gas to be transferred to the hot water and used as a heat source for various purposes.

[0059] 4) In some embodiments, the cement plant exhaust heat recovery system described in 3) above includes: a water supply line (40) for introducing the water to the heat transfer tube; a hot water discharge line (61) for carrying hot water discharged from the heat exchanger; a bypass line (62) connected to the hot water discharge line and the water supply line so as to bypass the heat exchanger; a bypass flow control valve (63) disposed in the bypass line; Further equipped with The branch exhaust gas line is configured to guide the exhaust gas that has passed through the heat transfer tube to a coal mill (17) of the cement plant as a heat source for drying coal used by a kiln burner (19) for burning the cement raw materials.

[0060] According to the configuration of 4) above, the heat source of the exhaust gas flowing through the branch exhaust gas line can be used as a heat source for the coal mill. In addition, the flow rate of the exhaust gas discharged from the PH boiler varies depending on the operating state of the cement plant, and the temperature of the exhaust gas supplied to the coal mill needs to be kept within a certain range. In this regard, according to the configuration of 4) above, the flow rate of the feed water supplied to the heat exchanger can be adjusted by adjusting the opening degree of the bypass flow control valve, so that the heat exchange amount in the heat exchanger can be adjusted according to the operating state of the cement plant. Therefore, even if the operating state of the cement plant varies, the temperature of the exhaust gas supplied to the coal mill can be kept within a certain range.

[0061] 5) In some embodiments, the cement plant exhaust heat recovery system described in 4) above includes: The apparatus further includes a water tank (55) configured to receive the hot water flowing through the thermal fluid discharge line.

[0062] According to the above configuration 5), the hot water generated by the heat exchanger can be stored in the water tank by utilizing the exhaust heat contained in the exhaust gas flowing through the branch exhaust gas line. This makes it possible to effectively utilize the exhaust heat contained in the exhaust gas while minimizing its release outside the system.

[0063] 6) In some embodiments, the cement plant exhaust heat recovery system described in 5) above is A steam turbine (31); a first steam supply line (71) for guiding the steam discharged from the PH boiler to the steam turbine as a first working medium; a flasher (73) for generating steam by subjecting the hot water discharged from the water tank to a decompression treatment; a second steam supply line (72) for guiding the steam generated in the flasher to the steam turbine as a second working medium; It further comprises:

[0064] According to the above configuration 6), steam can be generated from the hot water stored in the water tank and supplied to the steam turbine as the second working medium. Since the second working medium is supplied to the steam turbine in addition to the first working medium, the exhaust heat of the exhaust gas can be utilized to improve the output of the steam turbine.

[0065] 7) In some embodiments, the cement plant exhaust heat recovery system according to 5) or 6) above, an AQC boiler (30) including an economizer (35) for generating hot water using, as a heat source, AQC exhaust gas (exhaust gas) discharged from an air quenching cooler (21) of the cement plant; a PH hot water supply line (36) for guiding the hot water discharged from the economizer to the PH boiler; a hot water extraction line (37) for guiding the hot water extracted from the PH hot water supply line to the water tank; It further comprises:

[0066] According to the above configuration 7), the surplus hot water discharged from the AQC boiler after being supplied to the PH boiler can be supplied to the water tank. This allows for more effective use of the waste heat generated in the cement plant.

[0067] 8) In some embodiments, the cement plant exhaust heat recovery system described in 7) above, a hot water extraction flow control valve (39) disposed in the hot water extraction line; a hot water flow control valve control unit (93) for controlling the hot water extraction flow control valve so that an opening degree of the hot water extraction flow control valve increases when a flow rate of the hot water flowing from the PH hot water supply line to the PH boiler becomes equal to or greater than a specified flow rate; It further comprises:

[0068] According to the above configuration 8), when surplus hot water is generated that does not need to be supplied to the PH boiler, the surplus hot water can be automatically supplied to the water tank. [Explanation of symbols]

[0069] 1: Cement plant waste heat recovery system 2: Cement plant 3: Waste heat recovery system 5: Heat recovery device 6a: First branch exhaust gas damper 6b: Second exhaust gas branch damper 7: Exhaust gas line 8: Exhaust gas damper 9: Branch exhaust gas line 9a: First branch exhaust gas line 9b: Second branch exhaust gas line 11: Cement raw material mill 11a: Hydraulic cylinder 13: Preheater 14: Calcination furnace 15: Pre-firing burner 16: Humidity control tower 17: Coal mill 18: Kiln 19: Kilburna 20: PH boiler 21: Air quenching cooler 22: Cement mill 23: Evaporator 24:Superheater 30: AQC boiler 31: Steam turbine 32: Generator 33: Condenser 35: Economizer 36: PH hot water supply line 37: Hot water extraction line 38: Hot water extraction valve 39:Hot water extraction flow control valve 40: Water supply line 43: AQC water supply line 44: Heat exchange water supply line 49: Branch line 50: Heat exchanger 51: Economizer 55: Water tank 61: Hot water discharge line 62: Bypass line 63: Bypass flow control valve 71: First steam supply line 72: Second steam supply line 73: Flasher 75: Return route 90: Controller 91: Damper control section 92: Bypass flow control valve control section 93: Hot water flow control valve control unit 111:Flowmeter 121: First exhaust gas temperature sensor C1: Connection part

Claims

1. A cement plant exhaust heat recovery system for recovering exhaust heat from a cement plant, comprising: a PH boiler for generating steam using exhaust gas discharged from a preheater of the cement plant as a heat source; an exhaust gas line for introducing the exhaust gas discharged from the PH boiler to a cement raw material mill of the cement plant as a heat source for drying the cement raw material; an exhaust gas damper disposed in the exhaust gas line; a branch exhaust gas line branching off from the exhaust gas line upstream of the exhaust gas damper; Equipped Cement plant waste heat recovery system.

2. The present invention further includes a damper control unit configured to control the opening degree of the exhaust gas damper based on a raw material mill operation parameter indicating an operation state of the cement raw material mill. The cement plant exhaust heat recovery system according to claim 1 .

3. The heat exchanger further includes a heat transfer tube disposed inside the branch exhaust gas line, the heat exchanger being configured to heat the feed water through heat exchange between the exhaust gas flowing through the branch exhaust gas line and the feed water supplied to the heat transfer tube.

3. The cement plant exhaust heat recovery system according to claim 1 or 2.

4. a water supply line for guiding the water to the heat transfer tube; a hot water discharge line for carrying hot water discharged from the heat exchanger; a bypass line connected to the hot water discharge line and the water supply line so as to bypass the heat exchanger; a bypass flow regulation valve disposed in the bypass line; Further equipped with The branch exhaust gas line is configured to guide the exhaust gas that has passed through the heat transfer tube to a coal mill of the cement plant as a heat source for drying coal used by a kiln burner for burning the cement raw material. The cement plant exhaust heat recovery system according to claim 3.

5. a water tank configured to receive the hot water flowing through the thermal fluid discharge line; The cement plant exhaust heat recovery system according to claim 4.

6. A steam turbine; a first steam supply line for guiding the steam discharged from the PH boiler to the steam turbine as a first working medium; a flasher for generating steam by subjecting the hot water discharged from the water tank to a decompression treatment; a second steam supply line for guiding the steam generated in the flasher to the steam turbine as a second working medium; Further equipped The cement plant exhaust heat recovery system according to claim 5.

7. an AQC boiler including an economizer for generating hot water using the AQC exhaust gas discharged from an air quenching cooler of the cement plant as a heat source; a PH hot water supply line for guiding the hot water discharged from the economizer to the PH boiler; A hot water extraction line for guiding the hot water extracted from the PH hot water supply line to the water storage tank; Further equipped The cement plant exhaust heat recovery system according to claim 5.

8. a hot water extraction flow control valve disposed in the hot water extraction line; a hot water flow control valve control unit for controlling the hot water extraction flow control valve so that an opening degree of the hot water extraction flow control valve increases when a flow rate of the hot water flowing from the PH hot water supply line to the PH boiler becomes equal to or greater than a predetermined flow rate; Further equipped The cement plant exhaust heat recovery system according to claim 7.

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