A refrigeration system using waste heat from boiler flue gas

Abstract

The present invention discloses a waste heat refrigeration system utilizing boiler flue gas, the system comprising a flue gas treatment unit, a water circulation pipeline, a spray pipeline and a heat transfer oil circulation pipeline which are serially mounted on a flue gas pipeline, the flue gas treatment unit comprising a waste heat pre-recovery device, a flue gas purification component and a steam-water separator which are sequentially arranged, the flue gas treatment unit comprising a waste heat pre-recovery device, a flue gas purification component and a steam-water separator which are sequentially arranged, the flue gas purification component comprising a dust collector and a desulfurization tower which are sequentially connected; and the steam-water separator is a spherical steam-water separator which is serially connected to the rear of the flue gas purification component, the corresponding gas outlet of which is connected to an evaporator group, and the liquid outlet is connected to a lithium bromide chiller. The present invention has a wide range of applications, high energy efficiency, and can simultaneously achieve certain water-saving benefits and energy-saving benefits.

Description

Technical Field

[0001] The invention relates to the technical field of boiler waste heat recovery, and in particular to a waste heat refrigeration system utilizing boiler flue gas. Background Art

[0002] Most of the flue gas generated by the boiler during use is directly discharged into the air, which not only causes a large amount of heat energy waste and reduces energy utilization. Flue gas is the main way of energy waste in boiler equipment. The energy consumption of traditional boiler flue gas is about 15%. Although energy-saving boilers can keep the heat loss of flue gas within 10%, they will still take away a lot of heat. At the same time, flue gas is directly discharged into the air, which will pollute the external environment and affect the atmospheric environment.

[0003] At present, the high exhaust temperature has become one of the main reasons affecting boiler efficiency. For every 10℃ increase in exhaust temperature, the boiler efficiency decreases by 0.6~1.0%. Based on the mandatory requirements of national environmental protection, industrial boilers must desulfurize and denitrify the flue gas before they can be discharged. The most commonly used desulfurization method is wet flue gas desulfurization, which consumes a lot of water. After desulfurization, the flue gas is basically supersaturated wet flue gas with a lot of moisture, which not only causes visual pollution and environmental pollution, deteriorates the urban landscape, but also aggravates the formation of haze. However, this type of supersaturated wet flue gas will cause equipment corrosion under low temperature conditions. In order to reduce low-temperature corrosion, the exhaust temperature of the boiler is generally designed to be 130~150℃, and the actual operating exhaust temperature is more than 20℃ higher than the design value, resulting in a higher temperature for this part of the flue gas. Direct discharge will cause a great waste of resources.

[0004] In the existing technology, heat exchangers are also used to recover the waste heat of flue gas to improve the efficiency of boilers, but the structures of heat exchangers on the market are different and the effects are uneven. There are still defects such as poor energy-saving and environmental protection effects and low energy utilization rate. If the waste heat in the exhaust gas can be converted into hot water by increasing the rear heating surface, and air-conditioning cold water can be produced through a hot water type lithium bromide chiller, centralized cooling can be achieved, and cooling water can be recycled, it has both economic value and social value. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a refrigeration system using waste heat from boiler flue gas to solve the shortcomings of the above-mentioned background technology.

[0006] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0007] A refrigeration system utilizing waste heat of boiler flue gas, comprising a flue gas treatment unit installed in series on a flue gas pipeline, an evaporator group and a lithium bromide chiller arranged at the rear of the flue gas treatment unit;

[0008] The flue gas treatment unit comprises a waste heat pre-recovery device, a flue gas purification component and a steam-water separator which are arranged in sequence. The waste heat pre-recovery device comprises a tubular shell arranged along the direction of flue gas travel, wherein a plurality of heat-conducting material tubes arranged in parallel are arranged in the shell as flue gas channels and a heat exchange unit. Both ends of the shell are closed, and heat-conducting oil is filled between the shell and the heat exchange tube, and a heat-conducting oil circulation pipeline is externally connected. A heat-conducting unit is connected to the heat-conducting oil circulation pipeline, and the heat-conducting oil is connected to a water circulation pipeline, and the heat of the heat-conducting oil is exchanged with cold water through the heat-conducting unit.

[0009] The flue gas purification assembly includes a dust collector and a desulfurization tower connected in sequence;

[0010] The steam-water separator is a spherical steam-water separator, which is connected in series at the rear of the flue gas purification component and is used to separate gas and water from the purified flue gas; the gas outlet end of the spherical steam-water separator is connected to the evaporator group, and the gas exhaust device is connected to the rear of the evaporator group, and the evaporator group is connected to the water circulation pipeline; the water outlet end of the spherical steam-water separator and the hot water outlet end of the water circulation pipeline are connected to the lithium bromide chiller together, and the hot water separated in the spherical steam-water separator and the hot water in the water circulation pipeline are used as heat sources for cooling in the lithium bromide chiller, and after generating low-temperature water, it enters the water circulation pipeline for the next cycle.

[0011] As a further limitation, the amount of the heat transfer oil filled in the interlayer space between the shell and the heat exchange tube is 2 / 3 of the volume of the interlayer space.

[0012] As a further limitation, the heat conductive material tube is preferably an aluminum tube or a heat conductive ceramic tube, the inner diameter of a single tube is 15-30 cm, and the sum of the cross-sectional areas corresponding to the inner diameters of the heat conductive material tubes is 30-45% of the cross-sectional area of ​​the cylindrical shell volume portion.

[0013] As a further limitation, the heat transfer oil is preferably an alkylbenzene type heat transfer oil.

[0014] As a further limitation, the evaporator includes an evaporation chamber, a smoke passage for smoke to pass through is arranged in the evaporation chamber, a coil heat exchanger is wound around the smoke passage, a spray assembly facing the coil heat exchanger is arranged on the upper part of the coil heat exchanger, and a water receiving pan is arranged on the lower part of the coil heat exchanger;

[0015] Atomizing spray heads are evenly distributed on the spray assembly. The atomizing spray heads are externally connected to a spray pipeline and are connected to a water circulation pipeline through the spray pipeline. Low-temperature water generated by refrigeration in a lithium bromide chiller is used as spray water in the water circulation pipeline.

[0016] As a further limitation, the spray water outlet pipe of the evaporator, the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit are connected to a heat spreader as water inlet, and the outlet water of the heat spreader is directly connected to the hot water supply end of the lithium bromide chiller;

[0017] The heat spreader includes a heat-insulating shell and a buffer cavity arranged in the shell, and three groups of water inlet pipes are arranged on the buffer cavity, which are respectively connected with the spray water outlet pipe of the evaporator, the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit. Among them, the water inlet pipe corresponding to the spray water outlet pipe of the evaporator is a straight pipe, which is directly connected to the buffer cavity, and the water inlet pipe corresponding to the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit are independent serpentine heat exchange coils. Two groups of serpentine heat exchange coils are arranged in the buffer cavity and are connected to the buffer cavity at the end of the serpentine heat exchange coil to ensure the heat exchange effect.

[0018] Beneficial effect: The present invention recovers heat from boiler flue gas three times, and uses water as a heat transfer medium to send the tertiary recovered heat into a lithium bromide chiller as a heat source for refrigeration, and uses the lithium bromide chiller to produce cold capacity from the flue gas waste heat in the boiler flue gas, thereby realizing the recovery of flue gas waste heat. The recovery rate of flue gas waste heat is higher than that of traditional single or secondary heat recovery, which can improve the operating efficiency of the boiler, save energy and reduce costs; it can be widely used in the recovery of low-temperature hot water waste heat in the fields of petroleum, chemical industry, etc., and at the same time meet the demand for chilled water in the above-mentioned fields, thereby achieving the purpose of waste heat reuse.

[0019] At the same time, the hot and humid flue gas discharged from the desulfurization tower can be condensed through the lithium bromide chiller. The condensation effect is reliable, which can achieve the purpose of water saving while realizing deep demisting of the flue gas and achieving the purpose of whitening. At the same time, it can avoid the problems caused by poor quality of low-temperature water. It can directly enter the cooling cycle or be directly used for recycling. It can bring water-saving benefits to the enterprise while also having certain environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the present invention;

[0021] Among them: 1. Flue gas duct; 2. Waste heat pre-recovery device; 3. Heat conductive material pipe; 4. Dust collector; 5. Desulfurization tower; 6. Steam-water separator; 7. Evaporator; 8. Cooling flue gas outlet; 9. Spray pipeline; 10. Low-temperature water storage tank; 11. Water circulation pipeline; 12. Lithium bromide chiller; 13. Heat spreader; 14. Heat exchange unit; 15. Heat transfer oil circulation pipeline. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific diagrams and embodiments.

[0023] In the following embodiments, those skilled in the art will understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0024] See also Figure 1 A preferred embodiment of a waste heat refrigeration system utilizing boiler flue gas is disclosed. In this embodiment, the waste heat refrigeration system includes a flue gas pipeline 1 and a waste heat pre-recovery device 2, a dust collector 4, a desulfurization tower 5, a steam-water separator 6 and an evaporator 7 which are sequentially installed in series in the flue gas pipeline 1, and a cooling flue gas outlet 8 is connected to the rear of the evaporator 7. In addition, a water circulation pipeline 11, a spray pipeline 9 and a heat transfer oil circulation pipeline 15 are also included. In the embodiment, the pump structure on the circulation pipeline, the corresponding valve structure and the pressure device in the flue gas pipeline 1 are omitted, but the corresponding pump structure must be used to realize the corresponding water circulation and heat transfer oil circulation on the circulation pipeline, which should be known to those skilled in the art and the corresponding setting method should be known, and the omitted part should not be regarded as undisclosed technical content.

[0025] In this embodiment, the flue gas to be treated in the flue gas pipeline 1 is supersaturated wet flue gas with a temperature of 175°C. After entering the system, the supersaturated wet flue gas first undergoes the first heat recovery treatment through the waste heat pre-recovery device 2. The waste heat pre-recovery device 2 includes a cylindrical shell arranged along the length direction of the flue gas pipeline 1, the two ends of the shell are closed, and a plurality of parallel heat-conducting material tubes 3 are arranged in the shell as flue gas channels and heat exchange unit tubes. The heat-conducting material tubes 3 are aluminum tubes, and the inner diameter of a single tube is 20 cm, and the sum of the cross-sectional areas corresponding to the inner diameters of the heat-conducting material tubes 3 is 38% of the cross-sectional area of ​​the volume portion of the cylindrical shell; and between the shell of the waste heat pre-recovery device 2 and the heat exchange tube 3, an alkylbenzene type heat-conducting oil occupying 2 / 3 of the cavity space is filled, and a heat-conducting oil circulation pipeline 15 is externally connected.

[0026] The high-temperature and high-humidity flue gas entering the flue gas duct 1 undergoes the first heat exchange through the heat-conducting material pipe 3 and the heat-conducting oil when passing through the waste heat pre-recovery device 2. During the heat exchange, the heat is taken away by the heat-conducting oil and passes through the heat exchange unit 14. In the heat exchange unit 14, heat is exchanged with the low-temperature water sent out from the low-temperature water storage tank 10. After the heat exchange, the high-temperature water after the heat exchange is completed is sent out through the water circulation pipeline 11.

[0027] After the supersaturated wet flue gas passes through the waste heat pre-recovery device 2 for a heat recovery, the temperature drops to 120-130°C. At this time, after passing through the dust collector 4 and the desulfurization tower 5, the temperature is relatively low, so it has a better dust removal and desulfurization effect. After the dust removal by the dust collector 4 and the desulfurization by the desulfurization tower 5, the flue gas still contains a high amount of moisture, and it is necessary to separate the water vapor through the steam-water separator 6 to facilitate subsequent treatment; in this embodiment, the steam-water separator 6 adopts a spherical steam-water separator, which separates the water vapor through a cyclone separation method. The supersaturated wet flue gas after purification enters the air inlet of the steam-water separator 6. When the cyclone is used, the airflow will change from linear motion to circular rotation motion, and generate centrifugal force during the rotation, and pass through Gas-liquid separation is achieved through this centrifugal force, and the purity of the liquid retained in the liquid outlet can be guaranteed after desulfurization and dust removal, and it contains a certain amount of heat; the gas outlet is connected to the evaporator 7, the evaporator 7 is provided with an evaporator heat exchanger, and a spray pipe facing the evaporator heat exchanger is provided on the upper part of the evaporator heat exchanger. The spray pipe is connected to the low-temperature water storage tank 10 through the spray pipeline 9, and the water in the low-temperature water storage tank 10 is used as spray water. The high-temperature flue gas after water-gas separation coming out of the gas outlet is sprayed in the evaporator heat exchanger to achieve the second heat recovery. The water content of the flue gas temperature after the second heat recovery is already relatively low, basically controlled below 10%, and the outlet gas temperature is also basically 40~60℃.

[0028] During the heat recovery process, the high-temperature spray water generated by spraying, the high-temperature water separated by the steam-water separator 6, and the high-temperature outlet water after heat exchange from the heat exchange unit 14 are connected to a heat spreader 13. A buffer chamber is provided in the heat spreader 13. Three streams of water with different temperatures are mixed and heat-spread in the buffer chamber of the heat spreader 13. The outlet water temperature is controlled at 55-75°C and is sent to the lithium bromide chiller 12 as a heat source for refrigeration. After refrigeration, low-temperature water of about 8°C is produced, and the low-temperature water is discharged into the low-temperature water storage tank 10 for circulation.

[0029] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A refrigeration system utilizing waste heat from boiler flue gas, characterized in that: It includes a flue gas treatment unit installed in series on the flue gas pipeline, an evaporator group and a lithium bromide chiller arranged at the rear of the flue gas treatment unit; The flue gas treatment unit comprises a waste heat pre-recovery device, a flue gas purification component and a steam-water separator which are arranged in sequence. The waste heat pre-recovery device comprises a tubular shell arranged along the direction of flue gas travel, wherein a plurality of heat-conducting material tubes arranged in parallel are arranged in the shell as flue gas channels and a heat exchange unit. Both ends of the shell are closed, and heat-conducting oil is filled between the shell and the heat exchange tube, and a heat-conducting oil circulation pipeline is externally connected. A heat-conducting unit is connected to the heat-conducting oil circulation pipeline, and the heat-conducting oil is connected to a water circulation pipeline, and the heat of the heat-conducting oil is exchanged with cold water through the heat-conducting unit. The flue gas purification assembly includes a dust collector and a desulfurization tower connected in sequence; The steam-water separator is a spherical steam-water separator, which is connected in series to the rear of the flue gas purification component and is used to separate gas and water from the purified flue gas; the gas outlet of the spherical steam-water separator is connected to the evaporator group, and the gas exhaust device is connected to the rear of the evaporator group, and the evaporator group is connected to the water circulation pipeline; the water outlet of the spherical steam-water separator and the hot water outlet of the water circulation pipeline are connected to the lithium bromide chiller together, and the hot water separated from the spherical steam-water separator and the hot water in the water circulation pipeline are used as heat sources for cooling in the lithium bromide chiller, and after generating low-temperature water, it enters the water circulation pipeline for the next cycle; The spray water outlet pipe of the evaporator, the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit are connected to a heat spreader as water inlet, and the outlet water of the heat spreader is directly connected to the hot water supply end of the lithium bromide chiller; The heat spreader includes an insulating shell and a buffer cavity arranged in the shell, and three groups of water inlet pipes are arranged on the buffer cavity, which are respectively connected with the spray water outlet pipe of the evaporator, the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit. Among them, the water inlet pipe corresponding to the spray water outlet pipe of the evaporator is a straight pipe, which is directly connected to the buffer cavity, and the water inlet pipe corresponding to the outlet pipe of the steam-water separator and the high-temperature water outlet pipe in the heat exchange unit are independent serpentine heat exchange coils. Two groups of serpentine heat exchange coils are arranged in the buffer cavity and are connected to the buffer cavity at the end of the serpentine heat exchange coil.

2. The refrigeration system using waste heat from boiler flue gas according to claim 1, characterized in that: The filling amount of the heat transfer oil in the interlayer space between the shell and the heat exchange tube is 2 / 3 of the volume of the interlayer space.

3. The refrigeration system using waste heat from boiler flue gas according to claim 1, characterized in that: The heat-conducting material tube is an aluminum tube or a heat-conducting ceramic tube.

4. The refrigeration system using waste heat from boiler flue gas according to claim 1, characterized in that: The inner diameter of a single tube of the heat conductive material tube is 15-30 cm, and the sum of the cross-sectional areas corresponding to the inner diameters of the tubes of the heat conductive material tube is 30-45% of the cross-sectional area of ​​the volume portion of the cylindrical shell.

5. The refrigeration system using waste heat from boiler flue gas according to claim 1, characterized in that: The heat transfer oil is an alkylbenzene type heat transfer oil.

6. The refrigeration system using waste heat from boiler flue gas according to claim 1, characterized in that: The evaporator comprises an evaporation chamber, in which a smoke channel for smoke to pass is arranged, a coil heat exchanger is wound around the smoke channel, a spray assembly facing the coil heat exchanger is arranged on the upper part of the coil heat exchanger, and a water receiving pan is arranged on the lower part of the coil heat exchanger.

7. The refrigeration system using waste heat from boiler flue gas according to claim 6, characterized in that: Atomizing spray heads are evenly distributed on the spray assembly. The atomizing spray heads are externally connected to a spray pipeline and are connected to a water circulation pipeline through the spray pipeline. Low-temperature water generated by refrigeration in a lithium bromide chiller is used as spray water in the water circulation pipeline.

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