JP7312245B2 - Exhaust heat recovery system and its operation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust heat recovery system for recovering heat from exhaust gas in a cement manufacturing process, and an operating method thereof.

The cement manufacturing process can be broadly divided into the raw material process of drying, pulverizing, and blending the cement raw materials, the firing process of firing the raw materials into clinker, an intermediate product, and the finishing process of adding gypsum to the clinker and pulverizing it into cement. consists of In the firing step, the cement raw material is first preheated by a preheater, then calcined in a calcining furnace, then calcined in a kiln furnace, and finally cooled in a cooler. An exhaust heat recovery system is known that introduces exhaust gas from such a baking process into a boiler, recovers the exhaust heat, and generates power using the recovered heat. Patent Documents 1 and 2 disclose this type of exhaust heat recovery system.

FIG. 1 of Patent Document 1 discloses an exhaust heat recovery system in a conventional general cement firing process. This exhaust heat recovery system includes a heat recovery boiler, an exhaust fan, and a raw material mill in an exhaust gas system of a preheater. Exhaust gas from the preheater flowing into the exhaust gas system by the operation of the exhaust fan is guided to the heat recovery boiler to recover heat, and then passed through the raw material mill to be used for drying and pulverizing the raw material for cement.

Patent Literature 2 discloses an exhaust heat recovery system in a cement firing process. This exhaust heat recovery system includes a heat recovery boiler and an exhaust fan in a first exhaust gas system of the preheater, and a raw material mill and an exhaust fan in a second exhaust gas system of the preheater. A gas pipe connects the upstream side of the heat recovery boiler in the first exhaust gas system and the upstream side of the raw material mill in the second exhaust gas system. A control valve is provided in the gas pipe, and the control valve adjusts the exhaust gas flowing from the first exhaust gas system to the second exhaust gas system, so that the amount of heat of the exhaust gas introduced into the raw material mill is sufficient for drying the raw material. It is kept constant so that there is no excess or deficiency.

JP-A-58-194766 JP-A-58-194767

Cement raw materials that are dried and ground in raw material mills include limestone, clay, silica, and iron oxide raw materials. Since these raw materials are generally stored outdoors, the moisture content varies depending on the weather and season. The amount of heat required for drying the cement raw material also fluctuates according to the change in the water content of the cement raw material. In addition, the amount of heat required for drying the cement raw material varies depending on the amount of cement raw material processed.

As described above, the amount of heat required for drying the cement raw material in the raw material mill fluctuates. Therefore, if the heat quantity of the exhaust gas introduced into the raw material mill is constant as in Patent Document 2, the surplus heat quantity may cause a decrease in heat recovery efficiency, and the shortage of heat quantity may cause insufficient drying of the cement raw material.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust heat recovery system in a cement firing process including a boiler and an exhaust fan and a dryer provided downstream thereof, and a method of operating the same. , to increase the heat absorption of the boiler while avoiding insufficient drying of the material to be dried in the dryer.

An exhaust heat recovery system according to one aspect of the present invention includes:
an exhaust gas line including a boiler, an exhaust fan, and a dryer connected in series, through which exhaust gas from a preheater for preheating cement raw materials flows;
a bypass line connected to the exhaust gas line to flow the exhaust gas to the exhaust fan bypassing the boiler;
a flow rate adjusting device provided in the exhaust gas line or the bypass line for adjusting the flow rate of the exhaust gas flowing through the bypass line;
a moisture measuring device for measuring the moisture content of the material to be dried supplied to the dryer;
a thermometer for detecting the temperature of dryer exhaust gas discharged from the dryer;
Based on the moisture content of the material to be dried, the temperature detected by the thermometer, and the airflow rate of the exhaust fan, the amount of excess or deficiency of the amount of heat of the dryer is determined, and the bypass is determined based on the determined amount of excess or deficiency. a control device that determines the flow rate of the exhaust gas flowing through the line and operates the flow control device so that the determined flow rate of the exhaust gas is obtained.

An exhaust heat recovery system according to another aspect of the present invention includes:
an exhaust gas line including a boiler, an exhaust fan, and a dryer connected in series, through which exhaust gas from a preheater for preheating cement raw materials flows;
a bypass line connected to the exhaust gas line to flow the exhaust gas to the exhaust fan bypassing the boiler;
a flow rate adjusting device provided in the exhaust gas line or the bypass line for adjusting the flow rate of the exhaust gas flowing through the bypass line;
a moisture measuring device for measuring the moisture content of the material to be dried supplied to the dryer;
a thermometer for detecting the temperature of dryer exhaust gas discharged from the dryer;
According to the moisture content of the material to be dried measured by the moisture measuring device, a target value of the raw material mill outlet gas temperature at which the cement raw material is dried just enough is determined, and the dryer exhaust gas detected by the thermometer is obtained. and a control device for controlling the temperature of the dryer exhaust gas to the target value by increasing or decreasing the flow rate of the exhaust gas flowing through the bypass line by the flow control device based on the temperature of the dryer.

A method for operating an exhaust heat recovery system according to one aspect of the present invention includes:
an exhaust gas line through which exhaust gas from a preheater for preheating cement raw material flows, comprising a boiler, an exhaust fan, and a dryer connected in series; A method of operating an exhaust heat recovery system comprising a bypass line flowing to
measuring the moisture content of the material to be dried supplied to the dryer;
detecting the temperature of dryer exhaust gas discharged from the dryer; and
Based on the moisture content of the material to be dried, the temperature of the exhaust gas from the dryer, and the air flow rate of the exhaust fan, the excess or deficiency of the heat quantity of the dryer is determined, and the bypass line is determined based on the determined excess or deficiency. determining the flow rate of the exhaust gas flowing through the bypass line, and adjusting the flow rate of the exhaust gas flowing through the bypass line to obtain the determined flow rate of the exhaust gas.

A method for operating an exhaust heat recovery system according to another aspect of the present invention comprises:
an exhaust gas line through which exhaust gas from a preheater for preheating cement raw material flows, comprising a boiler, an exhaust fan, and a dryer connected in series; A method of operating an exhaust heat recovery system comprising a bypass line flowing to
measuring the moisture content of the material to be dried supplied to the dryer;
detecting the temperature of dryer exhaust gas discharged from the dryer; and
A target value for the temperature of the exhaust gas from the dryer at the outlet of the dryer where the cement raw material is dried just enough according to the measured moisture content of the material to be dried, and the detected temperature of the exhaust gas from the dryer . and adjusting the flow rate of the exhaust gas flowing through the bypass line so that the temperature of the exhaust gas from the dryer becomes the target value.

In the exhaust heat recovery system, the dryer may be, for example, a raw material mill for drying and pulverizing cement raw materials, or a coal mill for drying and pulverizing coal. The dryer must sufficiently dry the material to be dried, whose moisture content may fluctuate.

Therefore, in the exhaust heat recovery system and the operating method thereof, the flow rate of the exhaust gas flowing through the bypass line is adjusted so that the material to be dried can be dried just enough. That is, when the amount of heat in the dryer is insufficient, the amount of heat introduced into the dryer is increased by increasing the flow rate of the exhaust gas flowing through the bypass line. Further, when the dryer has excess heat, the amount of heat introduced into the dryer is reduced by reducing the flow rate of the exhaust gas flowing through the bypass line.

Since the bypass line bypasses the boiler, the larger the flow rate of the exhaust gas flowing through the bypass line, the lower the heat absorption amount of the boiler. In the present invention, the flow rate of the exhaust gas flowing through the bypass line is adjusted to the minimum required so that the material to be dried is dried in the dryer just enough. Therefore, the amount of heat absorbed by the boiler can be maximized while avoiding insufficient drying of the material to be dried in the dryer.

According to the present invention, there is provided an exhaust heat recovery system for a cement firing process including a boiler, an exhaust fan and a dryer provided downstream thereof, and a method of operating the same, which avoids insufficient drying of the material to be dried in the dryer. It is possible to propose a method that increases the amount of heat absorbed by the boiler.

FIG. 1 is a diagram showing a schematic configuration of a cement burning plant including an exhaust heat recovery system according to one embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the control system of the exhaust heat recovery system.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a cement burning plant 1 including an exhaust heat recovery system 8 according to this embodiment.

A cement burning plant 1 shown in FIG.

The preheater 21 includes multiple stages of cyclones connected in series. In the preheater 21, exhaust heat from the rotary kiln 23 moves from the bottom cyclone to the top cyclone, and the cement raw material moves from the top cyclone to the bottom cyclone. The lowermost cyclone of the preheater 21 is connected to the calcining furnace 22 . In the calcining furnace 22, the cement raw material coming out of the preheater 21 is calcined in an atmosphere of about 900°C. The outlet of the calcining furnace 22 is connected to the inlet of the rotary kiln 23 . The rotary kiln 23 is a horizontally long cylindrical rotary kiln, and is installed with a slight slope from the raw material inlet toward the raw material outlet. In the rotary kiln 23, the cement raw material preheated and calcined by the preheater 21 and the calcining furnace 22 is calcined by exhaust heat from the air quenching cooler 24 and combustion gas from the burner. The outlet of rotary kiln 23 is connected to the inlet of air quenching cooler 24 . In the air quenching cooler 24, the hot sintered material coming out of the rotary kiln 23 is brought into contact with cold air, and the sintered material is rapidly cooled to become clinker. The clinker coming out of the air quenching cooler 24 is sent to a clinker silo by a clinker conveyor (not shown).

High-temperature exhaust gas from the rotary kiln 23 flows through the calcining furnace 22 and the preheater 21 in this order. The preheater 21 is connected to an exhaust gas line 4 through which exhaust gas from the cement baking process flows. The exhaust gas line 4 includes a preheater boiler (hereinafter referred to as "PH boiler 51"), an exhaust fan 52, a raw material mill 53, a separator 54, a dust collector 55, an exhaust fan 56, and a chimney 57 from upstream to downstream of the exhaust gas flow. are provided in this order for

By operating the exhaust fan 52 and the exhaust fan 56 , the exhaust gas from the preheater 21 flows out to the exhaust gas line 4 . Part of the heat of the exhaust gas flowing through the exhaust gas line 4 is first recovered by the PH boiler 51 . The steam superheated by the PH boiler 51 is introduced into a steam turbine 81 to drive a generator 82 connected to the steam turbine 81 via a shaft. The turbine output of the steam turbine 81 can be evaluated by, for example, the power generation amount of the generator 82 and the steam flow rate generated by the PH boiler 51 . In this embodiment, the turbine output of the steam turbine 81 is evaluated by the steam flow rate detected by the steam flow meter 65 provided in the PH boiler 51 .

The exhaust gas flowing through the exhaust gas line 4 is then used in the raw material mill 53 to dry cement raw materials. The cement raw material is introduced into the raw material mill 53 in addition to the exhaust gas. The cement raw material (dried material) supplied to the raw material mill 53 and the cement raw material (dried material) discharged from the raw material mill 53 are periodically sampled to measure the mass of each. The water content (moisture content) of the cement raw material supplied to the raw material mill 53 can be obtained based on the difference between the mass of the material to be dried and the mass of the dried material in the raw material mill 53, that is, the mass decreased in the raw material mill 53. can. In this embodiment, these cement raw material mass measuring devices are used as the water content measuring device 66 for measuring the water content of the cement raw material. However, the moisture measuring device 66 is not limited to the above, and a moisture measuring device using a known moisture measuring method such as an infrared absorption method, a Karl Fischer method, or a dielectric constant method may be used.

The cement raw material pulverized and dried in the raw material mill 53 is discharged together with the exhaust gas and flows into the separator 54 . The separator 54 separates and classifies the cement raw material from the exhaust gas. The exhaust gas from the separator 54 is discharged from the chimney 57 after the dust is separated by the dust collector 55 . The cement raw materials separated and classified by the separator 54 are mixed and stored in the silo 58 and supplied from the silo 58 to the preheater 21 . Cement raw materials classified by the separator 54 that do not have an appropriate particle size are sent to the inlet of the raw material mill 53 .

The outlet of the preheater 21 and the inlet of the PH boiler 51 are connected by a first conduit 41 . The first conduit 41 is provided with a boiler inlet gas thermometer 61 that detects the temperature of the exhaust gas entering the PH boiler 51 . The outlet of the PH boiler 51 and the inlet of the exhaust fan 52 are connected by the second conduit 42 . The second conduit 42 is provided with a boiler outlet gas thermometer 62 for detecting the temperature of the exhaust gas emitted from the PH boiler 51 . Further, the second conduit 42 is provided with an exhaust fan inlet gas thermometer 63 for detecting the temperature of the exhaust gas after the exhaust gas from the PH boiler 51 and the exhaust gas flowing through the bypass pipe 71 are merged. The outlet of the exhaust fan 52 and the inlet of the raw material mill 53 are connected by a third conduit 43 . A fourth conduit 44 connects the outlet of the raw material mill 53 and the inlet of the separator 54 . The fourth conduit 44 is provided with a mill outlet gas thermometer 64 for detecting the temperature of the passing exhaust gas. In addition, the exhaust gas passing through the fourth conduit 44 accompanies pulverized cement raw materials.

A bypass line 7 is connected to the exhaust gas line 4 to flow the exhaust gas from the preheater 21 to the exhaust fan 52 while bypassing the PH boiler 51 . Specifically, the bypass line 7 includes a bypass pipe 71 that bypasses the PH boiler 51 and connects between the first conduit 41 and the second conduit 42 . A bypass damper 72 is provided on the bypass pipe 71 . The bypass damper 72 is an example of the flow control device 9 that controls the flow rate of exhaust gas flowing through the bypass pipe 71 . A known flow control device 9 such as a valve or a blower may be used instead of the bypass damper 72 . Moreover, although the bypass damper 72 is provided in the bypass line 7 in this embodiment, the bypass damper 72 may be provided upstream of the PH boiler 51 in the exhaust gas line 4 .

The exhaust heat recovery system 8 according to the present embodiment is constructed in the cement burning plant 1 configured as described above, and recovers the heat of the exhaust gas flowing through the exhaust gas line 4 from the PH boiler 51 . More specifically, the exhaust heat recovery system 8 is connected to an exhaust gas line 4 including a PH boiler 51, an exhaust fan 52, and a raw material mill 53, which are connected in series, and an exhaust gas line 4. A bypass line 7 that bypasses and flows to the exhaust fan 52, and a bypass damper 72 that is provided in the bypass line 7 (or the exhaust gas line 4) and functions as a flow rate adjusting device 9 that adjusts the flow rate of the exhaust gas flowing through the bypass line 7. Prepare.

Operation of the exhaust heat recovery system 8 is controlled by the controller 6 . FIG. 2 is a block diagram showing the configuration of the control system of the exhaust heat recovery system 8. As shown in FIG. The controller 6 may be embodied as a kind of computer, such as a PLC (Programmable Controller). The controller 6 comprises a processor 60a and volatile and non-volatile memory 60b. The processor 60a is composed of a CPU, an MPU, a GPU, etc., and reads out and executes various programs stored in the memory 60b to realize control according to a control target and various processes described later. The control device 6 is connected to various devices of the cement burning plant 1 via a network, and is also connected to various instruments via the network. The control device 6 exchanges data with connected devices and acquires measurement information from the connected meters.

The control device 6 is connected to a boiler inlet gas thermometer 61, a boiler outlet gas thermometer 62, an exhaust fan inlet gas thermometer 63, a mill outlet gas thermometer 64, and a steam flow meter 65. Get information. The moisture content of the cement raw material measured by the moisture measuring device 66 may be measured periodically and stored in the control device 6 or input sequentially. The control device 6 is also connected to the bypass damper 72 and the exhaust fans 52 and 56 . The control device 6 issues an opening command to the bypass damper 72 . The bypass damper 72 changes the degree of opening of the bypass pipe 71 according to the degree-of-opening command. The flow rate of the exhaust gas flowing through the bypass line 7 increases in proportion to the degree of opening of the bypass pipe 71 .

The control device 6 issues an air blow volume command to the exhaust fans 52 and 56 . The exhaust fans 52 and 56 change their output so as to achieve the air blow volume corresponding to the air blow volume command. However, the exhaust fans 52 and 56 may have a constant output and can only be switched on and off. The control device 6 may determine the air blow volume based on the following equation (1), and generate air volume commands to be sent to the exhaust fans 52 and 56 based on the determined air volume. However, in Equation 1, Vg is the air flow rate [Nm ³ /h], F is the steam flow rate detected by the steam flow meter 65 [Kg/h], Jg ₁ is the enthalpy of exhaust gas at the inlet of the PH boiler 51 [kJ /Nm ³ ], Jg ₂ is the enthalpy of exhaust gas at the outlet of the PH boiler 51 [kJ/Nm ³ ], h ₁ is the enthalpy of water at the heat transfer tube inlet of the PH boiler 51 [kJ/kg], h ₂ is the PH boiler 51 The enthalpy [kJ/kg] of water at the heat transfer tube outlet of , and L represents the heat loss [kJ/h] from the outer surface of the PH boiler 51, respectively.

Since the exhaust gas from the PH boiler 51 is used as process air during the operation of the cement burning plant 1, the blowing volumes of the exhaust fans 52 and 56 are desirably kept constant. The control device 6 acquires the water content of the cement raw material supplied to the raw material mill 53, the mill outlet gas temperature detected by the mill outlet gas thermometer 64, and the air blowing rate of the exhaust fan 52, and monitors these values. do. The mill outlet gas temperature changes according to the water content of the cement raw material discharged from the raw material mill 53 . Therefore, the control device 6 monitors the water content of the cement raw material discharged from the raw material mill 53, which is estimated from the mill outlet gas temperature, so as to be maintained at a predetermined value. However, the control device 6 may monitor the moisture content of the cement raw material at the outlet of the raw material mill 53 that is directly measured in the same manner as the water content of the cement raw material supplied to the raw material mill 53 .

The control device 6 controls the operation of the exhaust heat recovery system 8 so that the heat absorption amount of the PH boiler 51 is further increased. An operation method 1 and an operation method 2 by the control device 6 will be described below. The control device 6 implements one of the operating method 1 and the operating method 2 .

[Operating method 1]
The control device 6 calculates the amount of heat in the raw material mill 53 based on the water content of the cement raw material, the raw material mill outlet gas temperature, and the amount of air flow. For example, the amount of heat required in the raw material mill 53 is derived from the water content of the cement raw material, and the amount of excess or deficiency of the amount of heat with respect to this required amount of heat is determined from the temperature of the mill outlet gas and the air flow rate. The control device 6 determines the flow rate of the exhaust gas flowing through the bypass line 7 based on the amount of heat in the raw material mill 53 . For example, the control device 6 stores in advance the relationship between the amount of excess or deficiency in the amount of heat, the amount of air blown, and the flow rate of the exhaust gas flowing through the bypass line 7. Flow rate can be determined. Here, instead of the flow rate of the exhaust gas flowing through the bypass line 7, at least one of the degree of opening of the bypass damper 72, the flow rate of the exhaust gas flowing through the PH boiler 51, and the flow rate ratio between the PH boiler 51 and the bypass line 7 is determined. may be

The control device 6 obtains the opening degree of the bypass damper 72 that realizes the determined flow rate of the exhaust gas flowing through the bypass line 7 . The obtained opening degree of the bypass damper 72 may be displayed on, for example, a monitor (not shown) connected to the control device 6 so that the operator can visually recognize it. The control device 6 outputs an opening degree command to the bypass damper 72 based on the obtained opening degree of the bypass damper 72 . As a result, when the amount of heat in the raw material mill 53 is insufficient, the amount of heat introduced into the raw material mill 53 is increased by increasing the flow rate of the exhaust gas flowing through the bypass line 7 . Further, when the amount of heat in the raw material mill 53 is excessive, the amount of heat introduced into the raw material mill 53 decreases due to the decrease in the flow rate of the exhaust gas flowing through the bypass line 7 .

[Operating method 2]
The control device 6 controls the raw material mill outlet gas temperature to a predetermined value by increasing or decreasing the flow rate of the exhaust gas flowing through the bypass line 7 according to the change in the degree of opening of the bypass damper 72 . This predetermined value is a target value of the raw material mill outlet gas temperature at which the cement raw material can be dried just enough. The predetermined value may be stored in advance in the control device 6, or may be obtained using an arithmetic expression given in advance according to the detected water content of the cement raw material. When the detected mill outlet gas temperature is lower than a predetermined value, the controller 6 increases the amount of heat introduced into the raw material mill 53 by increasing the flow rate of the exhaust gas flowing through the bypass line 7, thereby Let the mill outlet gas temperature be a predetermined value. Further, when the raw material mill outlet gas temperature is higher than a predetermined value, the amount of heat introduced into the raw material mill 53 is reduced by reducing the flow rate of the exhaust gas flowing through the bypass line 7, thereby reducing the raw material mill outlet gas temperature to the predetermined value. and

Since the bypass line 7 bypasses the PH boiler 51, the heat absorption amount of the PH boiler 51 decreases as the flow rate of the exhaust gas flowing through the bypass line 7 increases. In the above-described operation methods 1 and 2, the flow rate of exhaust gas flowing through the bypass line 7 is adjusted to the minimum required so that the cement raw material is dried in the raw material mill 53 just enough. Therefore, the heat absorption amount of the PH boiler 51 can be maximized while avoiding insufficient drying of the cement raw material in the raw material mill 53 .

Although the preferred embodiments of the present invention have been described above, the present invention may include modifications of the details of the specific structures and/or functions of the above embodiments without departing from the spirit of the present invention. . For example, the above configuration can be modified as follows.

For example, in the exhaust heat recovery system 8 according to the above embodiment, instead of the raw material mill 53, a coal mill that pulverizes and dries coal may be used. That is, instead of the raw material mill 53, the dryer 5 (a device having a wide drying function) may be used. The exhaust heat recovery system 8 in which the dryer 5 is used in place of the raw material mill 53 in the above-described embodiment has the raw material mill 53 as the "dryer", the cement raw material as the "material to be dried", and the mill outlet gas thermometer 64 as It is explained by reading each as "dryer exit gas thermometer".

As described above, the exhaust heat recovery system 8 according to the present embodiment includes the boiler 51, the exhaust fan 52, and the dryer 5 (for example, the raw material mill 53 and the coal mill) connected in series, and the cement An exhaust gas line 4 through which the exhaust gas of the preheater 21 for preheating the raw material flows, a bypass line 7 connected to the exhaust gas line 4 and flowing the exhaust gas to the exhaust fan 52 bypassing the boiler 51, and provided in the exhaust gas line 4 or the bypass line 7 and a flow control device 9 (for example, a bypass damper 72 ) that controls the flow rate of the exhaust gas flowing through the bypass line 7 .

The exhaust heat recovery system 8 includes a moisture measuring device 66 for measuring the moisture content of the material to be dried supplied to the dryer 5, a thermometer 64 for detecting the temperature of the dryer exhaust gas discharged from the dryer 5, and a controller 6 .

The control device 6 when carrying out the operation method 1 controls the dryer 5 based on the moisture content of the material to be dried supplied to the dryer 5, the temperature detected by the thermometer 64, and the air blowing volume of the exhaust fan 52. Then, the flow rate of the exhaust gas flowing through the bypass line 7 is determined based on the calculated excess and deficiency, and the flow control device 9 is operated so as to obtain the determined flow rate of the exhaust gas.

That is, the operation method 1 includes measuring the moisture content of the material to be dried supplied to the dryer 5, detecting the temperature of the dryer exhaust gas discharged from the dryer 5, and measuring the moisture content of the material to be dried. Excess or deficiency of the amount of heat of the dryer 5 is obtained based on the quantity, the temperature of the exhaust gas from the dryer, and the airflow rate of the exhaust fan 52, and the flow rate of the exhaust gas flowing through the bypass line 7 is determined based on the obtained excess or deficiency. and adjusting the flow rate of the exhaust gas flowing through the bypass line 7 so that the determined flow rate of the exhaust gas is obtained.

In addition, the control device 6 when carrying out the operation method 2, based on the moisture content of the material to be dried supplied to the dryer 5, the temperature detected by the thermometer 64, and the air blowing volume of the exhaust fan 52, The temperature of the dryer exhaust gas is controlled to a predetermined value by increasing or decreasing the flow rate of the exhaust gas flowing through the bypass line 7 using the flow control device 9 .

That is, the operation method 2 includes measuring the moisture content of the material to be dried supplied to the dryer 5, detecting the temperature of the dryer exhaust gas discharged from the dryer 5, and measuring the moisture content of the material to be dried. It includes adjusting the flow rate of the exhaust gas flowing through the bypass line 7 so that the temperature of the dryer exhaust gas reaches a predetermined value based on the amount, the temperature of the dryer exhaust gas, and the blowing rate of the exhaust fan 52 .

The dryer 5 must sufficiently dry the material to be dried, the moisture content of which may fluctuate. Therefore, in the exhaust heat recovery system 8 and its operation method, the flow rate of the exhaust gas flowing through the bypass line 7 is adjusted so that the material to be dried can be dried just enough. That is, when the amount of heat in the dryer 5 is insufficient, the amount of heat introduced into the dryer 5 is increased by increasing the flow rate of the exhaust gas flowing through the bypass line 7 . Further, when there is excess heat in the dryer 5, the amount of heat introduced into the dryer 5 is reduced by reducing the flow rate of the exhaust gas flowing through the bypass line 7. - 特許庁

Since the bypass line 7 bypasses the boiler 51, the heat absorption amount of the boiler 51 decreases as the flow rate of the exhaust gas flowing through the bypass line 7 increases. In the present invention, the flow rate of the exhaust gas flowing through the bypass line 7 is adjusted to the minimum required so that the material to be dried is dried in the dryer just enough. Therefore, the heat absorption amount of the boiler 51 can be maximized while avoiding insufficient drying of the material to be dried in the dryer.

1: Cement firing plant 4: Exhaust gas line 5: Dryer 6: Control device 7: Bypass line 8: Exhaust heat recovery system 9: Flow control device 21: Preheater 22: Calcination furnace 23: Rotary kiln 24: Air quenching cooler 41 to 44: conduit 51: PH (preheater) boiler 52: exhaust fan 53: raw material mill 54: separator 55: dust collector 56: exhaust fan 57: chimney 58: silo 60a: processor 60b: memory 61: boiler inlet gas thermometer 62 : Boiler outlet gas thermometer 63 : Exhaust fan inlet gas thermometer 64 : Mill outlet gas thermometer (dryer outlet thermometer)
65: Steam flow meter 66: Water content measuring device 71: Bypass pipe 72: Bypass damper 81: Steam turbine 82: Generator

Claims (4)

an exhaust gas line including a boiler, an exhaust fan, and a dryer connected in series, through which exhaust gas from a preheater for preheating cement raw materials flows;
a bypass line connected to the exhaust gas line to flow the exhaust gas to the exhaust fan bypassing the boiler;
a flow rate adjusting device provided in the exhaust gas line or the bypass line for adjusting the flow rate of the exhaust gas flowing through the bypass line;
a moisture measuring device for measuring the moisture content of the material to be dried supplied to the dryer;
a thermometer for detecting the temperature of dryer exhaust gas discharged from the dryer;
Based on the moisture content of the material to be dried, the temperature detected by the thermometer, and the airflow rate of the exhaust fan, the amount of excess or deficiency of the amount of heat of the dryer is determined, and the bypass is determined based on the determined amount of excess or deficiency. a control device that determines the flow rate of the exhaust gas flowing through the line and operates the flow control device so that the determined flow rate of the exhaust gas is obtained;
Exhaust heat recovery system. an exhaust gas line including a boiler, an exhaust fan, and a dryer connected in series, through which exhaust gas from a preheater for preheating cement raw materials flows;
a bypass line connected to the exhaust gas line to flow the exhaust gas to the exhaust fan bypassing the boiler;
a flow rate adjusting device provided in the exhaust gas line or the bypass line for adjusting the flow rate of the exhaust gas flowing through the bypass line;
a moisture measuring device for measuring the moisture content of the material to be dried supplied to the dryer;
a thermometer for detecting the temperature of dryer exhaust gas discharged from the dryer;
According to the moisture content of the material to be dried measured by the moisture measuring device, a target value of the raw material mill outlet gas temperature at which the cement raw material is dried just enough is determined, and the dryer exhaust gas detected by the thermometer is obtained. a control device that controls the temperature of the dryer exhaust gas to the target value by increasing or decreasing the flow rate of the exhaust gas flowing through the bypass line by the flow rate adjusting device based on the temperature of
Exhaust heat recovery system. an exhaust gas line through which exhaust gas from a preheater for preheating cement raw material flows, comprising a boiler, an exhaust fan, and a dryer connected in series; A method of operating an exhaust heat recovery system comprising a bypass line flowing to
measuring the moisture content of the material to be dried supplied to the dryer;
detecting the temperature of dryer exhaust gas discharged from the dryer; and
Based on the moisture content of the material to be dried, the temperature of the exhaust gas from the dryer, and the air flow rate of the exhaust fan, the excess or deficiency of the heat quantity of the dryer is determined, and the bypass line is determined based on the determined excess or deficiency. determining the flow rate of the exhaust gas flowing through the bypass line, and adjusting the flow rate of the exhaust gas flowing through the bypass line to obtain the determined flow rate of the exhaust gas;
A method of operating an exhaust heat recovery system. an exhaust gas line through which exhaust gas from a preheater for preheating cement raw material flows, comprising a boiler, an exhaust fan, and a dryer connected in series; A method of operating an exhaust heat recovery system comprising a bypass line flowing to
measuring the moisture content of the material to be dried supplied to the dryer;
detecting the temperature of dryer exhaust gas discharged from the dryer; and
A target value for the temperature of the exhaust gas from the dryer at the outlet of the dryer where the cement raw material is dried just enough according to the measured moisture content of the material to be dried, and the detected temperature of the exhaust gas from the dryer . Based on , adjusting the flow rate of the exhaust gas flowing through the bypass line so that the temperature of the dryer exhaust gas reaches the target value,
A method of operating an exhaust heat recovery system.

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