CN108489290A - A kind of high-temperature flue gas residual neat recovering system - Google Patents

Abstract

The invention belongs to the technical field of coal tar deep processing, and in particular relates to a high-temperature flue gas waste heat recovery system. A high-temperature expansion joint is installed at the interface between the high-temperature heat exchanger and the high-temperature flue gas fan, a cold air bypass pipe and a blower are installed next to the high-temperature heat exchanger, and an air volume meter and an air volume regulating valve are installed between the high-temperature heat exchanger and the high-temperature burner , the pure radiation heating furnace is connected with the high-temperature heat exchanger through a high-temperature flue. The flue gas after heat exchange by the heat exchanger is introduced into the low-temperature flue through the high-temperature flue gas fan, and finally discharged through the chimney on the top of the pure radiation heating furnace. The invention can reduce the high-temperature flue gas whose temperature is higher than 450°C that cannot be recovered by conventional waste heat recovery systems to below 450°C, thereby recovering the heat of the high-temperature section in the high-temperature flue gas and reducing energy consumption.

Description

A high-temperature flue gas waste heat recovery system

technical field

The invention belongs to the technical field of coal tar deep processing, and in particular relates to a high-temperature flue gas waste heat recovery system.

Background technique

The tube furnace of the coal tar deep processing system, because the heated medium is a fluid that is easy to coke, for the convenience of later operation and maintenance, a pure radiation tube furnace is often used, and the exhaust gas temperature usually exceeds 450 °C. The conventional waste heat recovery system is suitable for the flue gas whose exhaust temperature is lower than 450°C, and the exhaust gas temperature is higher than 450°C. When the load is large, the waste heat boiler is used for comprehensive utilization. However, for the tube furnace in the tar deep processing industry, due to The overall load is small, and the exhaust gas temperature is higher than 450°C, so there are few ways to recover the waste heat of high-temperature flue gas. In the coal tar deep processing system, the occasional load fluctuation of the device will cause the temperature of the exhaust gas of the tube furnace to be super high for a short time, which will affect the waste heat recovery system, especially the safe operation and service life of the flue gas induced draft fan. The exhaust gas temperature of the high-temperature waste heat recovery system is high. Due to the thermal expansion properties of the material itself, it will cause high-temperature stress problems that conventional waste heat recovery does not have. The key high-temperature heat exchangers and flue pipes need special designs.

Contents of the invention

The purpose of the present invention is to provide a high-temperature waste heat recovery system for recovering exhaust gas at a temperature of 450 to 750°C. Through high-temperature waste heat recovery, the temperature of high-temperature flue gas can be reduced to below 450°C, and then conventional The waste heat recovery system further recovers heat.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A high-temperature flue gas waste heat recovery system. A high-temperature expansion joint is arranged at the interface between the high-temperature heat exchanger and the high-temperature flue gas fan. A cold air bypass pipe and a blower are arranged beside the high-temperature heat exchanger. There is an air volume meter and an air volume regulating valve between them. The pure radiation heating furnace and the high-temperature heat exchanger are connected through a high-temperature flue. A flue gas bypass flue with an automatic regulating valve is installed on the high-temperature flue. Downstream of the high-temperature heat exchanger, the flue gas after heat exchange by the high-temperature heat exchanger is introduced into the low-temperature flue through the high-temperature flue gas fan, and finally discharged through the chimney on the top of the pure radiation heating furnace.

The high temperature heat exchanger includes a high temperature heat exchange tube group, the high temperature heat exchange tube group is supported by one end, and the other end is a free end, the upper end of the high temperature heat exchange tube group is connected to the internal expansion joint, and the bottom of the high temperature heat exchange tube group is connected to the low temperature flue gas. The gas pipe is connected, and the low-temperature flue gas pipe is provided with a cleaning and drainage port. The high-temperature heat exchange tube group is sealed by a steel shell to form a heat exchange tube shell side. The upper part of the heat exchange tube shell side is the high-temperature flue gas with a cleaning reserved port. catheter.

The high temperature expansion joint is a bellows structure, made of stainless steel 304 or above.

The high-temperature flue adopts an external thermal insulation structure and is made of stainless steel 304 or above.

The low-temperature flue is provided with a reserved interface for the low-temperature flue.

The high-temperature flue gas fan uses circulating water for cooling, and is made of stainless steel 304 or above.

The low-temperature smoke pipe temperature measuring point is set between the high-temperature flue gas fan and the high-temperature heat exchanger. When the flue gas temperature measured by the low-temperature smoke pipe temperature measuring point exceeds a limit value, the flue gas bypass smoke The automatic regulating valve on the duct is opened, and part of the high-temperature flue gas is directly discharged from the flue gas bypass flue with the automatic regulating valve into the low-temperature flue, reducing the inlet temperature of the high-temperature flue gas fan; the flue gas flow of the bypass is determined by the temperature of the low-temperature flue pipe Measuring point feedback control ensures that the temperature of the flue gas entering the high-temperature flue gas fan does not exceed the temperature.

During normal operation, high-temperature flue gas above 450°C is drawn from the chimney of the pure radiation heating furnace and enters the high-temperature heat exchanger through the high-temperature flue; the combustion-supporting air at room temperature is introduced from the atmosphere through the blower into the high-temperature heat exchanger Heat exchange with high-temperature flue gas in the heat exchanger produces high-temperature combustion-supporting air; during low-load operation, by increasing the passage of bypass combustion-supporting air, the temperature of the tube wall of the heat exchange tube is increased to avoid dew point corrosion of the high-temperature heat exchanger.

When the system fails or is overhauled, the blower is in normal use, and the cold air goes through the cold air bypass pipe without passing through the high-temperature heat exchanger, and directly enters the high-temperature burner; the sealed chimney baffle on the top of the pure radiation heating furnace is opened, and the high-temperature flue gas Exhaust directly from the chimney without entering the system.

The high-temperature flue gas enters the high-temperature heat exchange tube group from the high-temperature flue gas duct, and the low-temperature flue gas after heat exchange is discharged from the low-temperature flue gas duct; the normal-temperature combustion air enters the shell side of the heat exchange tube from the side of the high-temperature heat exchanger, and passes through multiple The baffle heat exchange is discharged from the side of the high-temperature heat exchanger; the cleaning reserved port is cleaned by external steam or water to clean the inner wall of the high-temperature heat exchange tube group, and the cleaned waste liquid is discharged from the cleaning discharge port.

The beneficial effects obtained by the present invention are:

Through a waste heat recovery system including a high-temperature air preheater with its own expansion joint and a high-temperature flue gas fan, the high-temperature flue gas with a temperature higher than 450°C that cannot be recovered by a conventional waste heat recovery system can be reduced to below 450°C, thereby Recover the heat of the high-temperature section in the high-temperature flue gas to reduce the energy consumption of the device.

There is a branch circuit with an automatic regulating valve at the high-temperature flue, and the opening of the automatic regulating valve is adjusted through the feedback of the temperature measuring point at the outlet of the heat exchanger to introduce cold air, so as to achieve the effect of protecting the flue gas fan, thus ensuring the whole The device will not cause the overall shutdown due to occasional fluctuations in load.

A low-temperature flue gas interface is set externally, and an ordinary waste heat recovery system or desulfurization and denitrification process system can be added according to actual engineering needs, which expands the applicability of the system.

The invention has been tried out in a 350,000-ton/year coal tar deep processing project. The heat load of the tube furnace is 3MW. When the high temperature heat exchange system is not installed, the discharge temperature of the tube furnace is 709°C, the thermal efficiency is 63%, and the fuel consumption is 1062Nm3/h; after connecting to the high temperature heat exchange system, the exhaust gas temperature drops to 375°C , the thermal efficiency rises to 78%, the fuel consumption is 858Nm3/h, and the calculation is based on the operation of 8000h per year, which can save 1634 thousand liters of fuel per year.

Description of drawings

Figure 1 is a flow chart of the high-temperature flue gas waste heat recovery system;

Figure 2 is the overall structure diagram of the high temperature flue gas waste heat recovery system;

Fig. 3 is a partial schematic diagram I of the high-temperature flue gas waste heat recovery system;

Fig. 4 is a partial schematic diagram II of the high-temperature flue gas waste heat recovery system;

Fig. 5 is the structural representation of high temperature heat exchanger;

In the figure: 1. blower; 2. high temperature expansion joint; 3. high temperature heat exchanger; 4. cold air bypass pipe; 5. air volume meter; 6. air volume regulating valve; 7. high temperature burner; Furnace; 9. High temperature flue; 10. Flue gas bypass flue with automatic regulating valve; 11. Temperature measuring point of low temperature flue pipe; 12. Reserved interface for low temperature flue; 13. Low temperature flue; 14. High temperature Flue gas fan; 15. Chimney; 16. Sealed chimney baffle; 3-1. High temperature heat exchange tube group; 3-2. Internal expansion joint; 3-3. Cleaning reserved opening; 3-4. High temperature flue gas Conduit; 3-5, cleaning liquid outlet; 3-6, low-temperature flue gas conduit; 3-7, shell side of heat exchange tube.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in FIGS. 1-5 , the high-temperature flue gas waste heat recovery system of the present invention includes a blower 1 , a high-temperature heat exchanger 3 , a high-temperature burner 7 , a pure radiation heating furnace 8 and a high-temperature flue gas fan 14 . In order to prevent the expansion of the high-temperature pipeline from bringing greater expansion thrust to the equipment, a high-temperature expansion joint 2 is provided at the interface between the high-temperature heat exchanger 3 and the high-temperature flue gas fan 14, and a cold air bypass pipe 4 and The blower 1, the high-temperature heat exchanger 3 and the high-temperature burner 7 are provided with an air volume meter 5 and an air volume regulating valve 6 for flow measurement and adjustment, and a high-temperature flue is passed between the pure radiation heating furnace 8 and the high-temperature heat exchanger 3 9 is connected, and at the same time, a flue gas bypass flue 10 with an automatic regulating valve is set on the high temperature flue 9, and the flue gas after heat exchange by the high temperature heat exchanger 3 is introduced into the low temperature flue 13 through the high temperature flue gas fan 14, and finally passed through The top chimney 15 of the pure radiation heating furnace 8 is discharged, and the low-temperature flue 13 is provided with a low-temperature flue reserved interface 12 .

The high temperature heat exchanger 3 includes a high temperature heat exchange tube group 3-1, the upper end of the high temperature heat exchange tube group 3-1 is connected to the internal expansion joint 3-2, the bottom of the high temperature heat exchange tube group 3-1 is connected to the low temperature flue gas duct 3-6 Connection, the low-temperature flue gas duct 3-6 is provided with a cleaning outlet 3-5, and the high-temperature heat exchange tube group 3-1 is sealed by a steel shell to form a heat exchange tube shell side 3-7, and a heat exchange tube shell side 3 -7 The upper part is a high-temperature flue gas conduit 3-4 with a reserved opening 3-3 for cleaning.

The material of the high-temperature expansion joint 2 is made of stainless steel 304 or above, and a bellows-type structure, which has the advantage of being able to effectively resist corrosion and oxidation caused by high-temperature flue gas, and at the same time effectively absorb the expansion caused by the pipeline;

The high-temperature flue 9 adopts an external thermal insulation structure instead of an internal thermal insulation structure. The benefits it brings can prevent the impurities from the internal insulation material from entering the high-temperature fan and heat exchanger, which will cause system failure;

The high-temperature flue 9 is provided with a flue gas bypass flue 10 with an automatic regulating valve, which has the advantage of avoiding unnecessary emergency shutdown caused by occasional load fluctuations of the heating furnace, thereby improving the stability of the overall operation sex;

The low-temperature flue 13 is provided with a reserved interface 12 for the low-temperature flue, which has the advantage that according to actual engineering needs, the flue gas below 450°C after heat exchange can be connected to a conventional waste heat recovery system or introduced into a desulfurization system. The denitrification system expands the applicability of the system;

The material of the high-temperature flue gas fan 14 is made of stainless steel 304 or above, and circulating water is used for cooling, which has the advantage of reducing the actual operating temperature of the fan and improving the operating life of the fan;

In the high-temperature heat exchanger 3, an internal expansion joint 3-2 is arranged at the end of the high-temperature heat exchange tube group 3-1, and the internal expansion joint 3-2 is made of stainless steel 304 or above, which has the advantage that it can be absorbed inside the equipment The expansion of the high-temperature heat exchange tube bundle ensures the safe and stable operation of the heat exchanger;

The high-temperature heat exchanger 3 is provided with a cleaning reserved port 3-3 on the high-temperature flue gas conduit 3-4, and a cleaning liquid discharge port 3-5 is provided on the low-temperature flue gas conduit 3-6, which brings The advantage is that the inside of the heat exchange tube bundle can be cleaned without dismantling the high temperature air preheater, which simplifies the maintenance process and improves the life of the heat exchanger.

During normal operation, the high-temperature flue gas above 450°C is drawn from the chimney 15 of the pure radiation heating furnace 8, and enters the high-temperature heat exchanger 3 through the high-temperature flue 9. In order to avoid impurities from being introduced into the high-temperature heat exchanger 3 and the high-temperature flue gas fan 14. The high-temperature flue 9 uses external insulation, and the material of the pipe is stainless steel 304 or above according to the operating temperature. The high-temperature flue gas fan 14 is placed downstream of the high-temperature heat exchanger 3 , in an area with a relatively low temperature. The low-temperature flue 13 from the outlet of the high-temperature flue gas blower 14 to the chimney 15 can be selected for internal or external thermal insulation according to actual needs; when the internal thermal insulation is selected, the material of the smoke pipe can be ordinary carbon steel. In order to absorb the thermal expansion of the pipeline due to high temperature, stainless steel high-temperature expansion joints 2 are respectively installed at the inlet and outlet of the high-temperature flue gas fan 14 and the high-temperature heat exchanger 3 . The high-temperature flue gas fan 14 is made of stainless steel, and cooling circulating water is introduced to reduce the operating temperature of the fan.

In order to prevent the flue gas temperature from being too high due to occasional fluctuations in the load of the pure radiation heating furnace 8, a flue gas bypass flue 10 with an automatic regulating valve is installed on the high-temperature flue 9, and a high-temperature flue gas fan 14 and a high-temperature The temperature measuring point 11 of the low-temperature flue pipe is set between the heat exchangers 3 . When the flue gas temperature measured by the low-temperature flue pipe temperature measuring point 11 exceeds a limit value, the automatic regulating valve on the flue gas bypass flue 10 with an automatic regulating valve is opened, and part of the high-temperature flue gas flows from the flue gas with an automatic regulating valve. The bypass flue 10 is directly discharged into the low-temperature flue 13 , thereby reducing the inlet temperature of the high-temperature flue gas fan 14 . The flue gas flow rate of the bypass can be controlled by the feedback of the temperature measuring point 11 of the low-temperature flue gas pipe, so as to ensure that the temperature of the flue gas entering the high-temperature flue gas fan 14 does not exceed the temperature.

The low-temperature flue 13 is provided with a reserved interface 12 for the low-temperature flue, sealed with a blind flange, and the caliber is consistent with the low-temperature flue 13 . When the actual project needs, it can be connected with an ordinary waste heat recovery system to further recover the heat in the flue gas; or an external desulfurization and denitrification system can be used to reduce pollutant emissions.

The combustion-supporting air at normal temperature is introduced into the high-temperature heat exchanger 3 from the atmosphere through the blower 1, and the blower 1 can be selected as a single or two sets (1 open and 1 standby) according to design requirements. In order to facilitate maintenance and avoid low-temperature corrosion, a cold air bypass pipe 4 is provided beside the high-temperature heat exchanger 3 . During normal operation, the combustion-supporting air can exchange heat with high-temperature flue gas in the high-temperature heat exchanger 3 to generate high-temperature combustion-supporting air. When the device is running at low load, the tube wall temperature of the heat exchange tube can be increased by increasing the passage of the bypass combustion air, thereby avoiding dew point corrosion of the high temperature heat exchanger. On the downstream of the high temperature heat exchanger 3, an air volume meter 5 and an air volume regulating valve 6 can be selected as required, and the combustion air volume can be accurately controlled according to the measured value, which can also reduce the energy consumption of the device.

When the high temperature waste heat recovery system fails or is overhauled, the high temperature flue gas recovery system can be isolated through the following operations. When the blower 1 is in normal use, the cold air goes through the cold air bypass pipe 4 instead of passing through the high-temperature heat exchanger 3, and directly enters the high-temperature burner 7; the sealed chimney baffle 16 on the top of the pure radiation heating furnace 8 is opened, and the high-temperature flue gas directly Straight discharge from the chimney 15 without entering the high temperature heat exchange system.

The key equipment of the present invention, the high-temperature heat exchanger 3, is realized in the following manner: the high-temperature flue gas enters the high-temperature heat exchange tube group 3-1 from the high-temperature flue gas conduit 3-4 at the top of the high-temperature heat exchanger 3, and the low-temperature flue gas after heat exchange The gas is discharged from the low-temperature flue gas duct 3-6 at the bottom of the heat exchanger. The normal-temperature combustion-supporting air enters the heat exchange tube shell side 3-7 from the side of the high-temperature heat exchanger 3 , and is discharged from the side of the high-temperature heat exchanger 3 through multiple baffles for heat exchange. The high-temperature heat exchange tube group 3-1 can be made of 304 stainless steel or above according to different operating temperatures. The high-temperature heat exchange tube group 3-1 is supported at one end (in this example, the bottom support can also be supported at the upper part), and the other end of the high-temperature heat exchange tube group 3-1 is a free end, connected to the internal expansion joint 3-2, and the internal The expansion joint 3-2 can absorb the high-temperature expansion of the inner 3-1 of the high-temperature heat exchange tube, so as to ensure that the external connection interface of the high-temperature heat exchanger 3 has no displacement during operation. In order to prevent the viscous components in the flue gas from adhering to the high-temperature heat exchanger 3, a cleaning port 3-3 is reserved in the high-temperature flue gas duct 3-4, and the high-temperature heat exchange tube group can be washed and cleaned by external steam or water 3-1 inner wall, the waste liquid after cleaning can be discharged from the cleaning discharge port 3-5 on the low-temperature flue gas conduit 3-6, thereby prolonging the service life of the high-temperature heat exchanger 3 .

Claims (10)

1. a kind of high-temperature flue gas residual neat recovering system, it is characterised in that：The interface of high-temperature heat-exchanging and high-temperature flue gas wind turbine is set Be equipped with high-temperature expansion joint, be provided with cold wind bypass pipe and air blower by high-temperature heat-exchanging, high-temperature heat-exchanging and high-temperature burner it Between be provided with air volume meter and volume damper, connected by high-temperature flue between pure radial pattern heating furnace and high-temperature heat-exchanging, it is high The flue gas by-pass flue of automatic regulating valve is provided on warm flue, high-temperature flue gas wind turbine is arranged in the downstream of high-temperature heat-exchanging, Flue gas after high-temperature heat-exchanging heat exchange introduces low temperature flue by high-temperature flue gas wind turbine, finally by the top of pure radial pattern heating furnace Smoke stack emission.

2. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：The high-temperature heat-exchanging includes High-temperature heat exchange tube group, high-temperature heat exchange tube group are supported using one end, and the other end is free end, and high-temperature heat exchange tube group upper end and inside are swollen Swollen section connection, high-temperature heat exchange tube group bottom are connect with low-temperature flue gas conduit, and low-temperature flue gas conduit, which is equipped with, cleans leakage fluid dram, high temperature Set of heat exchange tubes surrounding is sealed by box hat forms heat exchanger tube shell side, and heat exchanger tube shell side top is with the high-temperature flue gas for cleaning reserved opening Conduit.

3. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：The high-temperature expansion joint is wave Line tubular structure uses the above material of stainless steel 304.

4. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：The high-temperature flue is using outer Insulation construction uses the above material of stainless steel 304.

5. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：It is arranged in the low temperature flue There is low temperature flue spare interface.

6. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：The high-temperature flue gas wind turbine is adopted With recirculated water for cooling down, the above material of stainless steel 304 is used.

7. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：The high-temperature flue gas wind turbine with Low temperature smoke pipe temperature point is set between high-temperature heat-exchanging, is more than a limit value when low temperature smoke pipe temperature point measures flue-gas temperature When, it carries automatic regulating valve on the flue gas by-pass flue of automatic regulating valve and opens, part high-temperature flue gas is from automatic regulating valve Flue gas by-pass flue be directly discharged in low temperature flue, reduce high-temperature flue gas wind turbine inlet temperature；The flue gas flow of bypass By low temperature smoke pipe temperature point feedback control, ensure the flue-gas temperature not overtemperature into high-temperature flue gas wind turbine.

8. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：When normal operation, it is higher than 450 DEG C High-temperature flue gas is drawn from the chimney of pure radial pattern heating furnace, enters high-temperature heat-exchanging by high-temperature flue；The combustion air of room temperature High-temperature heat-exchanging is introduced from air by air blower, it is combustion-supporting that combustion air generates high temperature in high-temperature heat-exchanging with high-temperature flue gas heat exchange Wind；When underrun, combustion air throughput is bypassed by increase, the tube wall temperature of heat exchanger tube is improved, avoids high-temperature heat-exchanging Dew point corrosion.

9. high-temperature flue gas residual neat recovering system according to claim 1, it is characterised in that：When the system failure or maintenance, Air blower normal use, cold wind walk cold wind bypass pipe, and without high-temperature heat-exchanging, it is directly entered in high-temperature burner；Pure spoke Closed type flue damper at the top of emitting heating furnace is opened, and high-temperature flue gas is directly in line from chimney, without entering system.

10. high-temperature flue gas residual neat recovering system according to claim 2, it is characterised in that：High-temperature flue gas is from high-temperature flue gas Conduit enters high-temperature heat exchange tube group, and the low-temperature flue gas after heat exchange is discharged from low-temperature flue gas conduit；Room temperature combustion air exchanges heat from high temperature The side of device enters heat exchanger tube shell side, is exchanged heat by multiple tracks baffling, is discharged from high-temperature heat-exchanging side；Reserved opening is cleaned outside It connects steam or water rinses cleaning high-temperature heat exchange tube group inner wall, the waste liquid after cleaning is discharged by cleaning leakage fluid dram.