CN103486898A - Automatic safe control device of industrial waste heat recovery system - Google Patents

Abstract

The invention provides an automatic safety control device of an industrial waste heat recovery system. The automatic safety control device is based on the industrial waste heat recovery system. Temperature sensors are installed on the heat pipe type heat receiver to measure the surface temperature of the heat receiver, and temperature sensors are installed at the inlet and outlet of the condenser to measure the heat of the whole system. A pressure sensor is installed on the condenser to measure the pressure of the working medium inside the system. The signal of the above sensor is input to the control system, and the safe and effective utilization of industrial waste heat is realized by controlling the quantity of working medium in the system.

Description

Automatic safety control device for industrial waste heat recovery system

technical field

The invention relates to the field of automatic control, in particular to an automatic safety control device for an industrial waste heat recovery system.

Background technique

Industrial waste heat generally exists in electric power, metallurgy, chemical industry and other industries, and the flue gas at the tail of the boiler contains huge heat, so how to take out the heat in the flue gas and make full use of the above energy is one of the main research contents of energy saving and emission reduction. At present, the high-efficiency heat exchange methods in the utilization of industrial waste heat mainly include the following two types: direct heat exchange by heat exchangers and heat pipe heat exchangers. For the direct heat exchange method of the heat exchanger, since the heated substance directly exchanges heat with the flue gas, the temperature difference is large, which easily leads to corrosion on the surface of the heat exchanger and seriously affects the life of the heat exchanger.

At present, the most widely used waste heat recovery method is the heat pipe heat exchanger. Since the heat pipe uses the principle of phase change of the working fluid for heat exchange, it can effectively ensure that the surface temperature of the heat exchanger is maintained above the dew point temperature of the flue gas, and overcomes the problem of flue gas. Gas dew point corrosion problem.

However, in the existing industrial waste heat recovery systems using heat pipe heat exchangers, after the structure of the heat pipe heat exchanger is determined, its heat transfer capacity is difficult to adjust according to the heat transfer demand of the system. The inside of the heat pipe heat exchanger will generate a lot of thermal stress and even burst.

Contents of the invention

(1) Technical problems to be solved

In view of the above technical problems, the present invention provides an automatic safety control device for an industrial waste heat recovery system to improve the safety of the industrial waste heat recovery system.

(2) Technical solution

According to one aspect of the present invention, an automatic safety control device for an industrial waste heat recovery system is provided. The industrial waste heat recovery system includes: a heat pipe type heat collector (100); The liquid pipeline is connected to the condensate inlet of the heat pipe type heat extractor (100), and its exhaust port is connected to the outside world; the liquid intake end of the water pump (300) is connected to the working medium liquid pool (700), and its liquid outlet end is connected to To the replenishment port of the condenser. The automatic safety control device includes: a pressure sensor (601), which is arranged in the condenser (200), for measuring the pressure inside the condenser (200); an air release valve (603), which is a solenoid valve, is arranged in the condenser Between the outlet of the working fluid and the external environment; the control device (500), connected to the pressure sensor (601), is used to execute the following control process: when the value sensed by the pressure sensor (601) exceeds the third threshold, send The command opens the purge valve (603).

(3) Beneficial effects

It can be seen from the above technical solutions that the automatic safety control device of the industrial waste heat recovery system of the present invention has the following beneficial effects:

(1) A pressure sensor is installed in the condenser. When the pressure reaches the preset threshold, the control device sends an instruction to open the steam release valve (603), so that the pressure in the condenser is kept at a safe level, and the heat load of the user is avoided. When the heat pipe fluctuates violently, a large working medium pressure and thermal stress will be generated inside the heat pipe heat exchanger, and the waste heat recovery system may burst;

(2) A temperature sensor is installed at the inlet and outlet of the condenser 200 to use the heat recovered by the waste heat recovery system, and compare the waste heat recovery amount of the waste heat system with the heat demand of the user to adjust the quantity of secondary substances inside the system, thereby changing the entire system The high heat transfer capacity further avoids the risk of bursting of the waste heat recovery system due to the large working fluid pressure and thermal stress inside the heat pipe heat exchanger when the user's heat load fluctuates violently;

(2) A temperature sensor is installed outside the heat extractor 100 of the waste heat recovery system to measure the temperature of the outer surface of the heat extractor and the temperature of the flue gas, and the temperature of the surface of the heat extractor of the waste heat recovery system is controlled by a control device to ensure that The temperature of the outer surface of the heater is higher than the dew point temperature of the flue gas, which overcomes the common problem of dew point corrosion of heat exchange equipment in the existing waste heat recovery system.

Description of drawings

Fig. 1 is a schematic structural diagram of an industrial waste heat recovery system according to an embodiment of the present invention.

[Description of the main component symbols of the present invention]

100-heat pipe heater; 200-condenser;

300-water pump; 401-first temperature sensor;

402-the second temperature sensor; 403-the third temperature sensor;

500-control device; 601-pressure sensor;

602-inlet valve; 603-air release valve;

700-working fluid pool.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be noted that, in the drawings or descriptions of the specification, similar or identical parts all use the same figure numbers. Implementations not shown or described in the accompanying drawings are forms known to those of ordinary skill in the art. Additionally, while illustrations of parameters including particular values may be provided herein, it should be understood that the parameters need not be exactly equal to the corresponding values, but rather may approximate the corresponding values within acceptable error margins or design constraints. The directional terms mentioned in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only referring to the directions of the drawings. Therefore, the directional terms used are for illustration and not for limiting the protection scope of the present invention.

The invention provides an automatic safety control device of an industrial waste heat recovery system. In the automatic safety control device, a temperature sensor is installed on the heat receiver to measure the surface temperature of the heat receiver, a temperature sensor is installed at the inlet and outlet of the condenser to measure the heat of the whole system, and a pressure sensor is installed on the condenser To measure the pressure of the working medium inside the system, the signal of the above sensor is input to the PLC control system, and the quantity of secondary substances in the system is controlled to realize the safe and effective utilization of secondary waste heat.

In an exemplary embodiment of the present invention, an automatic safety control device is provided. Please refer to FIG. 1 , the automatic safety control device is based on an industrial waste heat recovery system including a heat pipe heat receiver 100 , a condenser 200 and a water pump 300 .

The heat pipe type heat extractor 100 is composed of a plurality of identical heat extracting plates, and the number of heat extracting plates is determined by the required heat load. The surface of each heating plate has fins as the extended heat exchange surface, and there are corrugations on the surface of the extended heat exchange surface, which are used to increase the disturbance of the flue gas measurement, improve the convective heat transfer coefficient, and increase the heat exchange area of the surface of the heat extraction plate. The inner surface of the inner cavity of the heat extraction plate is engraved with micro-scale grooves for enhancing the heat exchange inside the heat extraction device.

Condenser 200, its steam inlet end is connected to heat pipe heat collector 100 through a steam pipeline, and its condensate outlet is sent back to the condensate inlet of heat pipe heat collector through a liquid return pipeline; its exhaust port is connected to the outside world . The steam hose and liquid return pipeline between the condenser 200 and the heat extractor 100 are metal hoses, which facilitates the arrangement of the heat extractor and the condenser. The condenser is designed in different structural forms according to the different materials to be heated

The water pump 300, its liquid intake end is connected to the working medium liquid pool 700, and its liquid output end is connected to the liquid replenishment port of the condenser 200, which is used to increase the amount of working medium inside the system by increasing the heat taken by the system when necessary.

The heat pipe heat collector 100 absorbs heat from the flue gas, and drives the liquid working fluid inside to undergo a phase change to become steam. The steam is delivered to the condenser 200 through a steam line. The condenser 200 uses the heat carried in the steam to heat the material, and at the same time, the steam releases heat and condenses into a liquid working medium. The liquid working medium flows back to the heat receiver 100 of the heat pipe through the liquid return pipeline.

The automatic safety control device includes: a temperature sensor group, a PLC control device 500 , a pressure sensor 601 , a liquid inlet valve 602 and an air release valve 603 . Each component of the industrial waste heat recovery system of this embodiment will be described in detail below.

The temperature sensor group includes several temperature sensors, wherein: the first temperature sensor 401 is arranged on the outside of the outer surface of the heat pipe heat extractor, and is used to detect the temperature of the flue gas in the environment where the heat pipe heat extractor 100 is located; the second temperature sensor 402 , set on the outer surface of the heat pipe type heat extractor for detecting the temperature on the surface of the heat extractor; the third temperature sensor 403 is set on the outer surface of the outer inlet end of the condenser for measuring the temperature of the outer surface of the outer inlet end of the condenser ; The third temperature sensor 404 is arranged on the outer surface of the outlet end outside the condenser, and is used to measure the temperature of the outer surface of the outlet end outside the condenser;

The pressure sensor 601 is arranged in the condenser 200 and is used to measure the pressure inside the condenser. The air release valve 603 is a solenoid valve, which is arranged between the working medium outlet of the condenser and the external environment, and is used to reduce the amount of working medium inside the industrial waste heat recovery system when it is necessary to reduce the heat gain of the waste heat recovery system. The liquid inlet valve 602 is arranged between the liquid outlet of the water pump 300 and the refrigerant inlet of the condenser, and is used to increase the amount of the refrigerant inside the industrial waste heat recovery system if necessary.

The PLC control device 500 is connected to the first temperature sensor 401, the second temperature sensor 402, the third temperature sensor 403, and the pressure sensor 601 by wire or wirelessly, and controls the water pump 300 and the water pump in the system through the signals of the above sensors. The switch of the liquid valve 602 and the steam release valve 603 of the condenser achieves the purpose of adjusting the heat exchange rate of the system and preventing dew point corrosion on the surface and system bursting. The control process includes:

(1) When the temperature sensed by the first temperature sensor 401 is greater than the set first threshold, it indicates that the temperature of the flue gas is high, and heat can be extracted from the flue gas. The steam valve 603 is opened, and a certain amount of distilled water is filled into the waste heat recovery system. Then send an instruction to close the water pump 300 and the liquid inlet valve 602, keep the steam release valve 302 in an open state, and send an instruction to close the steam release valve 60 after the non-condensable gas is basically exhausted. At this point, the system starts waste heat recovery, where the first threshold is generally set at 50°C;

(2) When the difference between the temperature value sensed by the second temperature sensor 402 and the flue gas dew point temperature is less than the second threshold value, an instruction is sent to open the steam release valve 603 to reduce the amount of working fluid inside the industrial waste heat recovery system, thereby reducing the operating temperature of the system. Take heat to prevent dew point corrosion on the surface of the heat taker, where the second threshold is generally set at 10°C;

(3) When the difference between the temperature value sensed by the second temperature sensor 402 and the flue gas dew point temperature is greater than the third threshold value, an instruction is sent to open the water pump 300 and the liquid inlet valve 602 to increase the amount of working fluid inside the system and increase the system capacity. heat exchange, where the third threshold is generally set at 40°C;

(4) When the value sensed by the pressure sensor 601 exceeds the third threshold, an instruction is sent to open the steam release valve 603 to ensure the safety of the system. The third threshold is generally set to the maximum that the industrial waste heat recovery system can withstand 80% of the pressure value.

(5) When the temperature difference between the third temperature sensor 403 and the fourth temperature sensor 404 is less than the fourth threshold, an instruction is sent to open the water pump 300 and the liquid inlet valve 602 to increase the amount of working fluid inside the system to increase the heat transfer capacity of the system, Wherein, the fourth threshold depends on the heating requirement of the material in the condenser, for example, the material needs to be heated by 50° C. from ambient temperature.

It should be noted that the above-mentioned control processes do not have a strict sequence relationship, and one of them can be executed according to the situation.

So far, the present embodiment has been described in detail with reference to the drawings. Based on the above description, those skilled in the art should have a clear understanding of the industrial waste heat recovery system of the present invention.

In addition, the above definition of each element is not limited to the various specific structures or shapes mentioned in the embodiments, and those skilled in the art can simply replace them with familiar ones, for example:

(1) The working fluid distilled water used in the waste heat recovery system can also be replaced with other working fluids that have a large latent heat of vaporization and are easy to obtain;

(2) The PLC control system can be replaced by other control systems;

(3) The values of the first threshold, the second threshold, the third threshold and the fourth threshold can be reasonably set as required.

To sum up, the industrial waste heat recovery system of the present invention solves the technical defects of dew point corrosion, non-adjustable heat exchange rate, and bursting when the heat exchange rate changes drastically in the existing waste heat recovery system, and can control the surface of the heat collector Prevent the temperature from falling below the dew point, control the heat gain by measuring the temperature of the flue gas, prevent the system pressure from being too high, and greatly improve the safety and efficiency of industrial waste heat recovery.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. the automatic safety-control device of an industrial afterheat recovery system, this industrial afterheat recovery system comprises:

Heat pipe type heat exchanger (100);

Condenser (200), its steam inlet is connected with the steam (vapor) outlet of heat pipe type heat exchanger (100) by steam pipework, its condensation water outlet is connected to the condensation water entrance of heat pipe type heat exchanger (100) by the liquid back pipe road, its exhaust outlet is communicated to the external world;

Water pump (300), it is got the liquid end and is connected to working medium liquid pool (700), and its outlet end is connected to the fluid infusion mouth of condenser;

It is characterized in that, this automatic safety-control device comprises:

Pressure sensor (601), be arranged in condenser (200), for measuring the inner pressure of condenser (200);

Vent valve (603), be magnetic valve, is arranged between described condenser working medium outlet and external environment;

Control device (500), be connected to described pressure sensor (601), for carrying out following control flow: when the numerical value of pressure sensor (601) induction surpasses the 3rd threshold value, send instruction steam escape valve (603) is opened.

2. automatic safety-control device according to claim 1, is characterized in that, described the 3rd threshold value is 80% of the maximum pressure value that can bear of described industrial afterheat recovery system.

3. automatic safety-control device according to claim 1, is characterized in that, also comprises:

Sets of temperature sensors comprises:

The second temperature sensor (402), be arranged at the outer surface of described heat pipe type heat exchanger (100), for surveying the temperature on heat pipe heat collector (100) surface;

Liquid feed valve (602), be magnetic valve, is arranged between the outlet end and condenser working medium inlet of described water pump;

Described control device (500), be connected to described the second temperature sensor (402), for carrying out following control flow: when the difference of the temperature value of the second temperature sensor (402) induction and flue gas dew point temperature is less than Second Threshold, the transmission instruction is opened steam escape valve (603); Or, when the difference of the temperature value of the second temperature sensor (402) induction and flue gas dew point temperature is greater than the 3rd threshold value, the transmission instruction is opened water pump (300) and liquid feed valve (602).

4. automatic safety-control device according to claim 3, is characterized in that, described Second Threshold is 10 ℃.

5. automatic safety-control device according to claim 3 is characterized in that:

Described sets of temperature sensors also comprises: three-temperature sensor (403) is arranged at the outer surface of condenser outside arrival end, for measuring the temperature of condenser outside arrival end outer surface; The 4th temperature sensor (404), be arranged at the outer surface of the condenser outside port of export, for measuring the temperature of condenser outside port of export outer surface;

Described control device (500), be connected to described the first temperature sensor (401), also for carrying out following control flow: when the temperature difference of three-temperature sensor 403 and the 4th temperature sensor 404 is less than the 4th threshold value, sends instruction water pump (300) and liquid feed valve (602) are opened.

6. automatic safety-control device according to claim 5, is characterized in that, described the 4th threshold value depends on the demand for heat to material in condenser.

7. automatic safety-control device according to claim 5 is characterized in that:

Described sets of temperature sensors also comprises: the first temperature sensor (401) is arranged at the heat pipe type heat exchanger outer surface outside, for surveying the temperature of heat pipe type heat exchanger 100 place environment flue gases;

Described control device (500), be connected to described the first temperature sensor (401), for carrying out following control flow: when the temperature value of the first temperature sensor (401) induction is greater than the setting first threshold, sends instruction water pump (300), liquid feed valve (602) and steam escape valve (603) are opened; Then send instruction water pump (300) and liquid feed valve (602) are closed, keep steam escape valve (302) in open mode, after incoagulable gas is substantially drained, sends instruction steam escape valve (603) cuts out.

8. automatic safety-control device according to claim 7, is characterized in that, described first threshold is 50 ℃.

9. according to the described automatic safety-control device of any one in claim 1 to 8, it is characterized in that:

The heat-obtaining plate that described heat pipe type heat exchanger (100) is identical by polylith forms, and every heat-obtaining plate surface is with fin as the expansion heat-transfer surface, and expansion has ripple on the heat-transfer surface surface.

10. according to the described automatic safety-control device of any one in claim 1 to 8, it is characterized in that: described working medium is distilled water.

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