Cascade type organic heat carrier furnace

Abstract

The invention relates to a cascade type organic heat carrier furnace, which adopts a high-pressure water flue gas waste heat recovery system, realizes safe and efficient recovery and utilization of flue gas waste heat of the organic heat carrier furnace while effectively avoiding low-temperature corrosion of flue gas, and is compact and convenient to install and arrange. The organic heat carrier furnace is essentially an organic heat carrier furnace adopting a hot water type waste heat recoverer and an external air pre-heater heat regeneration technology.

Description

Technical Field

[0001] The invention belongs to the technical field of boilers, and in particular relates to a cascade organic heat carrier boiler using a hot water type waste heat recovery device and an air preheater outside the furnace for heat recovery. Background Art

[0002] A thermal oil boiler is a special boiler that uses an organic heat carrier, namely thermal oil, as its working medium. The high-temperature flue gas generated by the combustion of fuel heats the thermal oil. After the temperature of the thermal oil is increased, it provides the required heat for the heat-using equipment. When the flue gas generated by the combustion of the fuel is discharged through the chimney, the temperature is generally around 230°C, and some are even as high as 300°C, which not only wastes heat but also causes thermal pollution to the environment.

[0003] Most thermal oil furnaces do not recover waste heat or only add air preheaters to recover part of the flue gas waste heat. Some processes are equipped with waste heat recovery devices with steam generators such as heat pipe boilers. For example, ZL200420027889.4 provides a thermal oil furnace tail gas waste heat recovery device with a steam generator. This technology can reduce the exhaust temperature of the thermal oil furnace to about 160℃ and recover a certain amount of steam.

[0004] However, if the user of the thermal oil boiler does not need the steam generated by the waste heat recovery process, or the steam load changes, the common phenomenon of venting excess steam from the evaporator will occur. The use of this type of technology is greatly restricted, and only the air preheater can be increased to recover part of the flue gas waste heat. In order to avoid low-temperature corrosion of the air preheater, the exhaust temperature of the boiler is usually above 160°C, and the overall thermal efficiency of the boiler is still low, which does not meet the requirements of energy saving and environmental protection.

[0005] Therefore, how to reasonably recycle and utilize the flue gas waste heat of the organic heat carrier furnace, reduce the exhaust temperature, avoid low-temperature corrosion, and improve the overall thermal efficiency of the organic heat carrier furnace has become a hot topic in this field. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned shortcoming of the high exhaust temperature of the existing organic heat carrier furnace. A high-pressure water flue gas waste heat recovery system is adopted, that is, a combined system of an air-water heat exchanger in the flue and an air preheater outside the furnace, which effectively avoids low-temperature corrosion of the air-water heat exchanger in the flue and realizes safe and efficient thermal utilization of the waste heat of the flue gas of the organic heat carrier furnace.

[0007] The purpose of the present invention is achieved by the following measures:

[0008] A cascade organic heat carrier furnace, the cascade organic heat carrier furnace comprising a heat transfer oil furnace heating system and a high-pressure water flue gas waste heat recovery system, the high-pressure water flue gas waste heat recovery system comprising an air-water heat exchanger 10, an air preheater outside the furnace 11, a buffer water tank 13, a circulating water pump 15 and connecting pipes thereof,

[0009] The thermal oil furnace heating system comprises a thermal oil furnace body 1, a burner 2, a thermal oil pump 7, a heat-using device 3, an oil-gas separator 5, a filter 6 and connecting pipelines. The thermal oil is sequentially connected through the thermal oil pump 7, the thermal oil furnace body 1, the heat-using device 3, the oil-gas separator 5, the filter 6, and returns to the thermal oil pump 7. The thermal oil furnace system is provided with a high-level expansion tank 4 and a low-level oil storage tank 8. The separated gas in the oil-gas separator 5 enters the high-level expansion tank 4. The high-level expansion tank 4 is connected to the low-level oil storage tank 8 through an overflow pipe.

[0010] The gas-water heat exchanger 10 is arranged on the flue 9 of the high-temperature side thermal oil furnace. The flue gas with a higher temperature in the flue 9 is discharged after the temperature is reduced by the gas-water heat exchanger 10. The external air preheater 11 is arranged outside the flue 9. The air is transported to the burner 2 through the blower 19 and the hot air 20 formed by the external air preheater 11. The high-temperature water coming out of the gas-water heat exchanger 10 enters the external air preheater 11 as a heat source for the external air preheater 11.

[0011] The low-temperature water coming out of the external air preheater 11 enters the buffer water tank 13. The low-temperature water in the buffer water tank 13 is pressurized by the circulating water pump 15, enters the air-water heat exchanger 10, and is then transported to the external air preheater 11 to heat the air transported by the blower 19 and returns to the buffer water tank 13. Alternatively, the high-temperature water coming out of the air-water heat exchanger 10 enters the buffer water tank 13, is then transported to the external air preheater 11 through the circulating water pump 15, heats the air transported by the blower 19, and returns to the air-water heat exchanger 10, thereby forming a high-pressure water flue gas waste heat recovery system.

[0012] The buffer water tank 13 is provided with a pressure regulator 16, and the gas coming out of the pressure regulator 16 enters the buffer gas tank 13 through the pressure regulating valve 18, thereby maintaining the liquid water in the gas-water heat exchanger 10, the external air preheater 11, the buffer water tank 13 and the connecting pipes at a relatively high pressure, so that the saturation temperature corresponding to the heat carrier medium in the high-pressure water flue gas waste heat recovery system, i.e., water, is relatively high, thereby meeting the water temperature requirement for heating the external air preheater 11.

[0013] Preferably, the temperature of water coming out of the air-water heat exchanger 10 is 10° C. to 30° C. lower than the corresponding saturated water temperature under the system pressure.

[0014] The pressure regulator 16 is a high-pressure gas storage tank or a gas compressor.

[0015] Preferably, the gas coming out of the pressure regulator 16 is an inert gas, such as nitrogen or argon.

[0016] The fuel of the organic heat carrier furnace burner 2 is coal, biomass, fuel oil or combustible gas.

[0017] The water and air in the external air preheater 11 adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, fin tubes or spiral groove tubes.

[0018] The water and flue gas in the gas-water heat exchanger 10 adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, fin tubes or spiral grooved tubes.

[0019] By controlling the water inlet temperature of the air-water heat exchanger 10 (for example, above 85°C, the appropriate temperature is determined according to the sulfur content of the fuel), so that the average value of the water inlet temperature and the exhaust temperature of the air-water heat exchanger 10, that is, the metal wall temperature, is higher than the flue gas acid dew point temperature, low-temperature corrosion of the air-water heat exchanger 10 can be effectively avoided. Under the premise of avoiding condensation, the waste heat of the flue gas can be utilized to the maximum extent, so that the flue gas waste heat recovery device can operate economically and with high thermal efficiency, thereby achieving the purpose of energy saving and consumption reduction.

[0020] The buffer water tank 13 is provided with an exhaust valve 21, a pressure gauge, and a safety valve.

[0021] Insulation measures are taken for the pipes of the high-temperature water flue gas waste heat recovery system.

[0022] The high-pressure water flue gas waste heat recovery system is also applicable to a heat transfer oil furnace heating system adopting a suction circulation method.

[0023] Parts not mentioned in the present invention may be implemented using existing technologies, that is, existing mature and reliable reasonable improvement measures may be introduced into the present system, such as setting necessary valves, bypasses, automatic control facilities, etc.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. Energy saving: High-pressure water is used as the heat carrier for recovering waste heat from flue gas of organic heat carrier furnace, combined with air-water heat exchanger and heat recovery technology of air preheater outside furnace, which can effectively avoid low-temperature corrosion of flue gas of organic heat carrier furnace and realize safe and efficient recovery of waste heat from flue gas. The flue gas emission temperature can reach about 130℃, which meets the requirements of energy saving and environmental protection.

[0026] 2. Easy and compact installation: The air preheater 2 outside the furnace and the air-water heat exchanger 10 are easy to install, which can effectively save and utilize space. The air conveying duct is simplified and concise, which effectively reduces the duct resistance consumption;

[0027] 3. Flexible and convenient operation and adjustment: The high-pressure water flue gas waste heat recovery system is set up to realize the internal circulation heat utilization of flue gas waste heat. The operation and adjustment are flexible and convenient, and the heat balance of flue gas waste heat recovery is simple and reliable;

[0028] 4. High efficiency of heat exchange: The heat exchange coefficient of the gas-water heat exchanger 10 and the external air preheater 2 is affected by many factors, such as the specific heat capacity of water and flue gas, thermal conductivity, viscosity, flow rate, flow velocity, material and structure of the waste heat recovery device, etc., and the numerical range will be different. According to relevant literature reports, when using tubular heat exchange tubes, the heat exchange coefficient is about 66.7W / (㎡·K); while the conventional organic heat carrier furnace air preheater uses a tubular air preheater, and its heat exchange coefficient is 17.5W / (㎡·K)~23.3W / (㎡·K). Therefore, for the same parameters of combustion-supporting air, the combination of the gas-water heat exchanger 10 and the external air preheater 2 is nearly twice the size of the conventional flue air preheater, and the metal consumption of the heat exchanger is greatly reduced, and the air short circuit (heat exchange tube leakage) of the traditional air preheater will not cause a false decrease in exhaust temperature and an increase in actual power consumption;

[0029] 5. Compared with the prior art, the present invention is particularly suitable for the new construction or old system renovation of organic heat carrier furnaces using coal or biomass fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of a cascade organic heat carrier furnace of the present invention.

[0031] Figure 1 Among them, 1-thermal oil furnace body, 2-burner, 3-heat-using equipment, 4-high-level expansion tank, 5-oil-gas separator, 6-filter, 7-thermal oil pump, 8-low-level oil storage tank, 9-flue, 10-gas-water heat exchanger, 11-air preheater outside the furnace, 12-low-temperature water pipeline, 13-buffer water tank, 14-return water pipeline, 15-circulating water pump, 16-regulator, 17-regulator pipeline, 18-regulator valve, 19-blower, 20-hot air, 21-exhaust valve. DETAILED DESCRIPTION

[0032] The following is combined with Figure 1 The present invention is further described in detail with reference to the accompanying drawings and specific examples.

[0033] Embodiment 1:

[0034] A cascade organic heat carrier furnace, the cascade organic heat carrier furnace comprises a heat transfer oil furnace heating system and a high-pressure water flue gas waste heat recovery system, the high-pressure water flue gas waste heat recovery system comprises an air-water heat exchanger 10, an air preheater outside the furnace 11, a buffer water tank 13, a circulating water pump 15 and connecting pipes thereof,

[0035] The thermal oil furnace heating system comprises a thermal oil furnace body 1, a burner 2, a thermal oil pump 7, a heat-using device 3, an oil-gas separator 5, a filter 6 and connecting pipelines. The thermal oil is sequentially connected through the thermal oil pump 7, the thermal oil furnace body 1, the heat-using device 3, the oil-gas separator 5, the filter 6, and returns to the thermal oil pump 7. The thermal oil furnace system is provided with a high-level expansion tank 4 and a low-level oil storage tank 8. The separated gas in the oil-gas separator 5 enters the high-level expansion tank 4. The high-level expansion tank 4 is connected to the low-level oil storage tank 8 through an overflow pipe.

[0036] The gas-water heat exchanger 10 is arranged on the flue 9 of the high-temperature side thermal oil furnace. The flue gas with a higher temperature in the flue 9 is discharged after the temperature is reduced by the gas-water heat exchanger 10. The external air preheater 11 is arranged outside the flue 9. The air is transported to the burner 2 through the blower 19 and the hot air 20 formed by the external air preheater 11. The high-temperature water coming out of the gas-water heat exchanger 10 enters the external air preheater 11 as a heat source for the external air preheater 11.

[0037] The low-temperature water coming out of the external air preheater 11 enters the buffer water tank 13 through the low-temperature water pipeline 12. The low-temperature water in the buffer water tank 13 is pressurized by the return water pipeline 14 and the circulating water pump 15, enters the air-water heat exchanger 10, and then returns to the external air preheater 11 to heat the air delivered by the blower 19, and returns to the buffer water tank 13 through the low-temperature water pipeline 12. Alternatively, the high-temperature water coming out of the air-water heat exchanger 10 enters the buffer water tank 13, and then is delivered to the external air preheater 11 through the circulating water pump 15, heats the air delivered by the blower 19, and then returns to the air-water heat exchanger 10, thereby forming a high-pressure water flue gas waste heat recovery system.

[0038] The buffer water tank 13 is provided with a pressure regulator 16, and the gas from the pressure regulator 16 enters the buffer gas tank 13 through a pressure regulator pipeline 17 and a pressure regulator valve 18, thereby maintaining the liquid water in the gas-water heat exchanger 10, the external air preheater 11, the buffer water tank 13 and the connecting pipes at a relatively high pressure, so that the saturation temperature of the heat carrier medium in the high-pressure water flue gas waste heat recovery system, i.e., water, is relatively high, thereby meeting the water temperature requirement for heating the external air preheater 11.

[0039] Preferably, the temperature of water coming out of the air-water heat exchanger 10 is 10° C. to 30° C. lower than the corresponding saturated water temperature under the system pressure.

[0040] The pressure regulator 16 is a high-pressure gas storage tank or a gas compressor.

[0041] Preferably, the gas coming out of the pressure regulator 16 is an inert gas, such as nitrogen or argon.

[0042] The fuel of the organic heat carrier furnace burner 2 is coal, biomass, fuel oil or combustible gas.

[0043] The water and air in the external air preheater 11 adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, fin tubes or spiral groove tubes.

[0044] The water and flue gas in the gas-water heat exchanger 10 adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, fin tubes or spiral grooved tubes.

[0045] By controlling the water inlet temperature of the air-water heat exchanger 10 (for example, above 85°C, the appropriate temperature is determined according to the sulfur content of the fuel), so that the average value of the water inlet temperature and the exhaust temperature of the air-water heat exchanger 10, that is, the metal wall temperature, is higher than the flue gas acid dew point temperature, low-temperature corrosion of the air-water heat exchanger 10 can be effectively avoided. Under the premise of avoiding condensation, the waste heat of the flue gas can be utilized to the maximum extent, so that the flue gas waste heat recovery device can operate economically and with high thermal efficiency, thereby achieving the purpose of energy saving and consumption reduction.

[0046] The buffer water tank 13 is provided with an exhaust valve 21, a pressure gauge, and a safety valve.

[0047] Insulation measures are taken for the pipes of the high-temperature water flue gas waste heat recovery system.

[0048] The high-pressure water flue gas waste heat recovery system is also applicable to a heat transfer oil furnace heating system adopting a suction circulation method.

[0049] Parts not mentioned in the present invention may be implemented using existing technologies, that is, existing mature and reliable reasonable improvement measures may be introduced into the present system, such as setting necessary valves, bypasses, automatic control facilities, etc.

[0050] Although the present invention has been disclosed as above with preferred embodiments, they are not intended to limit the present invention. Anyone familiar with the art can make various changes or modifications without departing from the spirit and scope of the present invention, which also belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the definition of the claims of this application.

Claims

1. A cascade organic heat carrier furnace, characterized in that: The cascade organic heat carrier furnace comprises a heat transfer oil furnace heating system and a high-pressure water flue gas waste heat recovery system, wherein the high-pressure water flue gas waste heat recovery system comprises an air-water heat exchanger (10), an air preheater outside the furnace (11), a buffer water tank (13), a circulating water pump (15) and connecting pipes thereof, The thermal oil furnace heating system comprises a thermal oil furnace body (1), a burner (2), a thermal oil pump (7), a heat-using device (3), an oil-gas separator (5) and connecting pipelines. The thermal oil is sequentially passed through the thermal oil pump (7), the thermal oil furnace body (1), the heat-using device (3) and the oil-gas separator (5) connected by the pipelines, and then returns to the thermal oil pump (7). The thermal oil furnace heating system is provided with a high-position expansion tank (4) and a low-position oil storage tank (8). The gas separated in the oil-gas separator (5) enters the high-position expansion tank (4). The high-position expansion tank (4) is connected to the low-position oil storage tank 8 via an overflow pipe. The air-water heat exchanger (10) is arranged on the flue (9) of the high-temperature side thermal oil furnace. The flue gas with a relatively high temperature in the flue (9) is discharged after its temperature is reduced by the air-water heat exchanger (10). The external air preheater (11) is arranged outside the flue (9). The hot air (20) formed by the air blower (19) and the external air preheater (11) is transported to the burner (2) as combustion-supporting air. The high-temperature water discharged from the air-water heat exchanger (10) enters the external air preheater (11) as a heat source for the external air preheater (11); Low-temperature water from the external air preheater (11) enters the buffer water tank (13), and after being pressurized by the circulating water pump (15), the low-temperature water in the buffer water tank (13) enters the air-water heat exchanger (10), and is then transported to the external air preheater (11), heats the air transported by the blower (19), and returns to the buffer water tank (13). Alternatively, high-temperature water from the air-water heat exchanger (10) enters the buffer water tank (13), and is then transported to the external air preheater (11) by the circulating water pump (15), heats the air transported by the blower (19), and returns to the air-water heat exchanger (10), thereby forming a high-pressure water flue gas waste heat recovery system.

2. The cascade organic heat carrier furnace according to claim 1, characterized in that: The buffer water tank (13) is provided with a pressure regulator (16). The gas coming out of the pressure regulator (16) enters the buffer gas tank (13) through a pressure regulating valve (18).

3. The cascade organic heat carrier furnace according to claim 2, characterized in that: The pressure regulator (16) is a high-pressure gas storage tank or a gas compressor.

4. The cascade organic heat carrier furnace according to claim 2, characterized in that: The gas coming out of the constant pressure device (16) is an inert gas.

5. The cascade organic heat carrier furnace according to claim 1, characterized in that: The fuel of the cascade organic heat carrier furnace burner (2) is coal, biomass, fuel oil or combustible gas.

6. The cascade organic heat carrier furnace according to claim 1, characterized in that: The water and air in the external air preheater (11) adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, fin tubes or spiral grooved tubes.

7. The cascade organic heat carrier furnace according to claim 1, characterized in that: The water and flue gas of the gas-water heat exchanger (10) adopt an indirect heat exchange method, and the heat exchange tubes adopt smooth tubes, finned tubes or spiral grooved tubes.

8. The cascade organic heat carrier furnace according to claim 1, characterized in that: The average value of the water inlet temperature and the exhaust gas temperature of the air-water heat exchanger (10) is higher than the flue gas acid dew point temperature.

9. The cascade organic heat carrier furnace according to claim 1, characterized in that: The buffer water tank (13) is provided with an exhaust valve (23), a pressure gauge and a safety valve.

10. The cascade organic heat carrier furnace according to claim 1, characterized in that: The high-pressure water flue gas waste heat recovery system is also applicable to a heat transfer oil furnace heating system adopting a suction circulation method.

Images