CN111520695B - Comprehensive utilization system for recycling flue gas waste heat of aluminum electrolysis cell - Google Patents
Comprehensive utilization system for recycling flue gas waste heat of aluminum electrolysis cell Download PDFInfo
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- CN111520695B CN111520695B CN202010384443.0A CN202010384443A CN111520695B CN 111520695 B CN111520695 B CN 111520695B CN 202010384443 A CN202010384443 A CN 202010384443A CN 111520695 B CN111520695 B CN 111520695B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
- F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
- F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D1/00—Steam central heating systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B15/00—Sorption machines, plants or systems, operating continuously, e.g. absorption type
- F25B15/02—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas
- F25B15/06—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas the refrigerant being water vapour evaporated from a salt solution, e.g. lithium bromide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/27—Relating to heating, ventilation or air conditioning [HVAC] technologies
- Y02A30/274—Relating to heating, ventilation or air conditioning [HVAC] technologies using waste energy, e.g. from internal combustion engine
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/62—Absorption based systems
- Y02B30/625—Absorption based systems combined with heat or power generation [CHP], e.g. trigeneration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
Abstract
The invention discloses a comprehensive utilization system for recovering flue gas waste heat of an aluminum electrolytic cell, which respectively forms three heat recovery and utilization pipelines through steam generated by a flue gas heat exchanger: (1) Supplying steam to an alumina preparation process system through a afterburning boiler; (2) supplying steam to the lithium bromide absorption refrigerating unit; (3) supplying steam to the heating system; the requirements of users on cooling and heating in different seasons are met; through reasonable thermodynamic system design, the problems of low smoke waste heat taste, fluctuation of smoke parameters and the like of the aluminum electrolysis cell are solved, the smoke waste heat of the aluminum electrolysis cell is recovered, high-grade process steam is provided for alumina production, and the aims of energy conservation, emission reduction and comprehensive utilization of the waste heat are fulfilled.
Description
Technical Field
The invention relates to the technical field of aluminum electrolysis cell flue gas waste heat recovery, in particular to a comprehensive utilization system for aluminum electrolysis cell flue gas waste heat recovery.
Background
The electrolytic aluminum belongs to high energy consumption industry, and the aluminum electrolysis process needs to deliver high current to an electrolytic cell and can generate high temperature of 920-960 ℃. In order to protect the safe operation of the electrolytic cell and effectively remove harmful flue gas generated in the electrolytic process, the electrolytic aluminum workshop is provided with an electrolytic flue gas exhaust system. The flue gas temperature in the electrolysis flue gas exhaust system is about 150 ℃, and can reach 200 ℃ at most. The heat taken away by the flue gas of the electrolytic cell accounts for about 30 percent of the total heat loss. How to reasonably utilize the part of waste heat resources has important significance on energy conservation, emission reduction, cost reduction and efficiency improvement in the electrolytic aluminum industry.
At present, the utilization of the waste heat of the electrolytic flue gas is mostly used for power generation, for example, a steam-water separator is used for steam-water separation, and then a turbine generator set is used for power generation, and the waste heat of the flue gas and the waste heat of an aluminum electrolytic cell are comprehensively collected for power generation.
Besides, a few technologies are that the waste heat of the flue gas is utilized, and the system is also used for showering and heating, for example, the publication date is 2016 (6 months and 27 days), the publication number is CN205402866U, the invention name is the Chinese utility model patent of the electrolytic aluminum waste heat recycling shower and heating system, the electrolytic aluminum waste heat recycling shower and heating system disclosed by the document mainly comprises a flue gas pipe, a water inlet pipeline, a soft water circulation pipeline and a heating and heating pipeline, the soft water circulation pipeline comprises a first flue gas heat exchanger, a plate heat exchanger and a circulating pump which are communicated through pipelines, a water supplementing pipeline is connected on the pipeline between the circulating pump and the plate heat exchanger, a water supplementing pump, a soft water tank and a water softener are sequentially installed on the water supplementing pipeline, and a refrigerant inlet and a refrigerant outlet of the plate heat exchanger are respectively connected with the water inlet pipeline and the shower water tank; the heating pipeline comprises a heating pipe network, a second flue gas heat exchanger is connected between a water inlet end and a water return end of the heating pipe network, and heat medium inlets of the first flue gas heat exchanger and the second flue gas heat exchanger are connected with flue gas pipes. The structure can use the waste heat of the flue gas of the electrolytic aluminum for shower and heating, and has the effect of reducing energy consumption relatively.
However, no related technology for comprehensively utilizing the waste heat of the flue gas of the electrolytic cell for cooling and heating exists at present.
But also can not be simultaneously used for other comprehensive utilization means in the aspect of alumina preparation. During the production and preparation process of the alumina, high-temperature steam at 250-300 ℃ is required to heat the ore pulp. The waste heat smoke of the electrolytic cell can only heat the steam to 120-150 ℃, and cannot be used for the preparation process of the aluminum oxide. To make reasonable use of this steam, corresponding piping needs to be designed for effective use. Particularly, the heat-exchange device and the cooling and heating system are required to be comprehensively utilized simultaneously, so that a corresponding heat recovery comprehensive utilization system can be obtained only through corresponding specific design and test, and the utilization of the waste heat of the aluminum electrolysis cell flue gas can be improved.
Disclosure of Invention
The invention aims to develop a comprehensive utilization system for recovering the flue gas waste heat of an aluminum electrolysis cell by utilizing the flue gas waste heat of the aluminum electrolysis cell, and the system can realize the cold and heat utilization requirements of users in different seasons; through reasonable thermodynamic system design, the problems of low flue gas waste heat taste, fluctuation of flue gas parameters and the like of the aluminum electrolysis cell are solved, the flue gas waste heat of the aluminum electrolysis cell is recovered, high-grade process steam is provided for aluminum oxide production, and the aims of energy conservation, emission reduction and comprehensive utilization of the waste heat are fulfilled.
The technical scheme of the invention is as follows:
a comprehensive utilization system for recovering flue gas waste heat of an aluminum electrolytic cell is characterized in that: the system comprises a flue gas heat exchanger, a lithium bromide absorption refrigerating unit, an alumina preparation process system, a afterburning boiler, a heating system and corresponding connecting pipelines; the flue gas heat exchanger exchanges heat with flue gas of the electrolytic cell, and steam generated by the flue gas heat exchanger is output to three heat recycling pipelines:
the first pipeline is connected with the alumina preparation process system through a afterburning boiler, and a steam output pipeline of the flue gas heat exchanger is supplied to the alumina preparation process system;
a steam output pipeline of the flue gas heat exchanger is connected to the lithium bromide absorption refrigerating unit to supply steam to the lithium bromide absorption refrigerating unit, and a steam output loop of the lithium bromide absorption refrigerating unit is connected to the flue gas heat exchanger;
a steam output pipeline of the flue gas heat exchanger is simultaneously connected to a heating system to supply steam to the heating system, and a steam output loop of the heating system is connected to the flue gas heat exchanger;
the heat recovery and utilization pipeline is applied to be configured as follows:
in summer, the lithium bromide absorption refrigerating unit and the alumina preparation process system are put into use, and the heating system and corresponding pipelines are not put into use;
in winter, a heating system and an alumina preparation process system are put into use, and a lithium bromide absorption refrigerating unit and a corresponding pipeline are not put into use.
The specific configuration is used in summer and winter, and the climate is specifically adjusted according to the use situation.
The heat recycling pipeline of the comprehensive utilization system is specifically arranged as follows:
the steam output pipeline of the flue gas heat exchanger is divided into two steam output branches connected in parallel, wherein one steam output branch is a afterburning boiler branch, and the other steam output branch is an afterburning boiler bypass;
a afterburning boiler bypass valve is arranged on the afterburning boiler bypass and is respectively connected to the lithium bromide absorption refrigerating unit and the heating system through the afterburning boiler bypass valve;
on the afterburning boiler branch road, the steam input end of afterburning boiler is provided with inlet regulating valve one, and the steam output end of afterburning boiler sets up two branch roads, wherein: the first branch is a temperature increasing branch and is used for providing high-temperature steam for an alumina preparation process system, and the temperature range of the high-temperature steam is 250-300 ℃; the other branch is a steam supplementing branch, a first outlet adjusting valve is arranged on the steam supplementing branch, and the first outlet adjusting valve is used for providing supplementing steam for the heating system and the lithium bromide absorption refrigerating unit respectively.
In actual operation, the actual operation load of the flue gas heat exchanger may not reach the design value due to factors such as production tasks of aluminum electrolysis cell workshops, so that the parameters of outlet steam are too low, and the heat demand of the lithium bromide absorption refrigerating unit or the heating system cannot be met. Therefore, the system is provided with the steam supplementing branch, the opening degree of the outlet regulating valve of the afterburning boiler is automatically regulated according to actual working conditions, and the steam generated by the afterburning boiler and the steam of the flue gas heat exchanger are converged to supply proper amount of high-temperature steam to the lithium bromide absorption refrigerating unit or the heating system so as to improve the temperature of the two paths of required steam and achieve the purpose of reasonably regulating steam parameters.
And the steam inlet end and the steam outlet end of the aluminum oxide preparation process system are respectively provided with an inlet regulating valve IV and an outlet regulating valve IV, and the amount of steam entering the aluminum oxide preparation process system and the amount of steam coming out of the aluminum oxide preparation process system are regulated through the inlet regulating valve IV and the outlet regulating valve IV.
And the steam inlet end and the steam outlet end of the heating system are respectively provided with a third inlet regulating valve and a third outlet regulating valve, and the steam quantity entering the heating system and the steam quantity coming out of the heating system are regulated through the third inlet regulating valve and the third outlet regulating valve.
And the steam inlet end and the steam outlet end of the lithium bromide absorption refrigerating unit are respectively provided with a second inlet regulating valve and a second outlet regulating valve, and the steam quantity entering the lithium bromide absorption refrigerating unit and the steam quantity coming out of the lithium bromide absorption refrigerating unit are regulated through the second inlet regulating valve and the second outlet regulating valve.
The after-burning boiler can adopt natural gas or coal as fuel.
The lithium bromide absorption refrigerating unit mainly generates a driving heat source through waste heat steam of an electrolytic cell, and more refrigerant steam is generated by respectively using refrigerant steam generated by a high-temperature regenerator as a heat source of a low-temperature regenerator. The lithium bromide absorption refrigerating unit has the specific structure that: the system comprises a high-temperature regenerator, a low-temperature regenerator, a condenser, an evaporator, an absorber, a low-temperature heat exchanger, a heat recoverer, a high-temperature heat exchanger and the like.
According to the specific structure of the lithium bromide absorption refrigerating unit, the steam-water trend is as follows:
A. and waste heat steam enters a high-temperature regenerator of the lithium bromide absorption refrigerating unit through a steam inlet regulating valve II, is used as a heat source to heat absorption liquid intermediate liquid of the high-temperature regenerator to generate refrigerant steam, and then returns to the flue gas heat exchanger through a steam trap, a heat recoverer, an outlet regulating valve II and a heat exchanger circulating water pump.
B. The refrigerant steam generated by the high-temperature regenerator passes through the first steam-water separator to the low-temperature regenerator, and the concentrated solution of the absorption liquid in the low-temperature regenerator is continuously heated to generate more refrigerant steam; and the part of refrigerant steam passes through the steam-water separator II to the condenser and is condensed into refrigerant water together with the refrigerant steam from the high-temperature regenerator.
For the refrigerant steam of the high-temperature regenerator, the refrigerant steam enters the low-temperature regenerator through the steam-water separator, then intermediate liquid in the absorption liquid is heated to generate new refrigerant steam, the new refrigerant steam enters the condenser to be condensed into refrigerant water after passing through the steam-water separator II, meanwhile, cold steam coming from the steam-water separator is finally condensed into the refrigerant water in the condenser, and the waste heat steam is only used as a heat source to heat the absorption liquid after entering the high-temperature regenerator through the inlet regulating valve II and is not mixed with the absorption liquid in the high-temperature regenerator.
C. The refrigerant water generated in the condenser is sent to the evaporator through a pipeline, the refrigerant water in the evaporator forms a self-circulation loop through the refrigerant pump and the evaporator sprayer, the sprayed refrigerant water evaporates and absorbs heat to generate steam to enter the absorber, the back water of the chilled water from the cold load user is cooled to be low-temperature chilled water under the action of evaporation and heat absorption, and the low-temperature chilled water is supplied to the cold load user.
D. The steam generated by the evaporator enters the absorber, and is absorbed and mixed by the strong absorption solution sprayed by the absorber sprayer to become the weak absorption solution.
E. And the absorption liquid dilute solution in the absorber returns to the high-temperature regenerator through an absorption liquid pump II, the low-temperature heat exchanger, the heat recoverer and the high-temperature heat exchanger in sequence.
F. And the intermediate solution of the absorption liquid overflowing from the high-temperature regenerator is sent to the low-temperature regenerator through the high-temperature heat exchanger.
G. And the concentrated absorption solution in the low-temperature regenerator is sent to the absorber through the first absorption liquid pump and the heat exchanger.
H. And normal-temperature cooling water required by the lithium bromide absorption refrigerating unit absorbs heat from the cooling water inlet through the absorber and is heated, absorbs heat from the condenser and is heated, and finally is discharged from the cooling water outlet.
According to the design of the further structure, the principle of the system is as follows:
when the alumina preparation process system is put into operation, the afterburning boiler provides high-temperature steam for the alumina preparation process system; the load of the after-combustion boiler is adjusted according to the load of the alumina preparation process system and the load of the flue gas heat exchanger, namely the load is adjusted through a bypass valve, an inlet adjusting valve I, an outlet adjusting valve I, an inlet adjusting valve IV and an outlet adjusting valve IV of the after-combustion boiler respectively;
in summer, the heating system, the inlet regulating valve III and the outlet regulating valve III are closed, steam generated by the flue gas heat exchanger is sent to the lithium bromide absorption refrigerating unit for heat exchange, and meanwhile, a supplementary combustion boiler supplements a proper amount of high-temperature steam to the lithium bromide absorption refrigerating unit when necessary;
in winter, the lithium bromide absorption refrigerating unit, the inlet regulating valve II and the outlet regulating valve II are closed, steam generated by the flue gas heat exchanger is sent to a heating system for heating, and meanwhile, a supplementary combustion boiler supplements proper amount of high-temperature steam to the heating system when necessary.
The invention has the following beneficial effects and advantages:
(1) The invention provides a specific comprehensive solution for utilizing the flue gas waste heat of the electrolytic cell by organically combining cold consumption, domestic heat consumption and process heat consumption through effective measures.
(2) The invention provides domestic cold demand for users by using the lithium bromide absorption refrigerating unit, effectively utilizes the flue gas waste heat of the aluminum electrolytic cell and saves the power consumption of the common compression refrigerating unit.
(3) The invention utilizes the waste heat of the flue gas of the aluminum electrolysis cell, and the parameters are improved by the afterburning boiler, thereby providing a high-quality heat source required by the process for preparing the alumina.
(4) The invention utilizes the flue gas waste heat of the aluminum electrolytic cell, provides a heat source for heating in winter in heating areas, and reduces the heating energy consumption.
(5) The after-burning boiler is arranged behind the waste heat flue gas heat exchanger of the aluminum electrolytic cell, so that the steam quality can be effectively improved, and various process requirements can be met; meanwhile, the after-burning boiler can effectively reduce the influence of the fluctuation of the waste heat smoke parameters of the electrolytic cell and ensure the reliable operation of the system.
Drawings
Fig. 1 is a schematic diagram of the connection structure of the system.
Wherein the reference numerals are: 1 flue gas heat exchanger, 1-1 inlet regulating valve II, 1-2 outlet regulating valve II, 2 after-burning boiler, 2-1 inlet regulating valve I, 2-2 outlet regulating valve I, 2-3 after-burning boiler bypass valve, 3 heating system, 3-1 inlet regulating valve III, 3-2 outlet regulating valve III, 4 alumina preparation process system, 4-1 inlet regulating valve IV, 4-2 outlet regulating valve IV, 5 high temperature regenerator, 5-1 steam-water separator I, 6 steam trap, 7 heat recovery device, 8 heat exchanger circulating water pump, 9 low temperature regenerator, 9-1 steam-water separator II, 10 condenser, 11 evaporator, 11-1 evaporator spray thrower, 12 pump, 13 absorber, 13-1 refrigerant spray thrower, 14 absorption liquid pump I, 15 absorption liquid pump II, 16 low temperature heat exchanger, 17 high temperature heat exchanger, 18 cooling water inlet, 19 cooling water outlet, 20 cold load user, 21 flue gas of electrolytic tank.
Detailed Description
A comprehensive utilization system for recovering the flue gas waste heat of an aluminum electrolysis cell comprises a flue gas heat exchanger 1, a lithium bromide absorption refrigerating unit, an alumina preparation process system 4, a afterburning boiler 2, a heating system 3 and corresponding connecting pipelines; the flue gas heat exchanger 1 exchanges heat with flue gas 21 of the electrolytic cell, and steam generated by the flue gas heat exchanger 1 is output to three heat recovery and utilization pipelines respectively.
As shown in fig. 1, the heat recovery and utilization pipeline is specifically configured as follows:
the steam output pipeline of the flue gas heat exchanger 1 is divided into two steam output branches which are connected in parallel, wherein one steam output branch is a afterburning boiler branch, and the other steam output branch is an afterburning boiler bypass;
a post-combustion boiler bypass valve 2-3 is arranged on the post-combustion boiler bypass and is respectively connected to a lithium bromide absorption refrigerating unit and a heating system 3 through the post-combustion boiler bypass valve 2-3;
on the after-burning boiler branch, the steam input end of the after-burning boiler 2 is provided with an inlet regulating valve I2-1, and the steam output end of the after-burning boiler 2 is provided with two branch circuits, wherein: the first branch is a temperature increasing branch and is used for providing high-temperature steam for the alumina preparation process system 4, and the temperature range of the high-temperature steam is 250-300 ℃; the other branch is a steam supplementing branch, an outlet regulating valve I2-2 is arranged on the steam supplementing branch, and the steam supplementing branch is used for providing supplementing steam for a heating system 3 and the lithium bromide absorption refrigerating unit through the outlet regulating valve I2-2 respectively.
In actual operation, the actual operation load of the flue gas heat exchanger 1 may not reach the design value due to factors such as production tasks of aluminum electrolysis cell workshops, so that the parameters of outlet steam are too low, and the heat demand of the lithium bromide absorption refrigerating unit or the heating system 3 cannot be met. Therefore, a steam supplementing branch is designed in the system, the opening degree is automatically adjusted through an outlet adjusting valve I2-2 of the afterburning boiler 2 according to actual working conditions, steam generated by the afterburning boiler 2 and steam of the flue gas heat exchanger 1 are converged to a lithium bromide absorption type refrigerating unit or a heating system 3 to supplement proper amount of high-temperature steam so as to improve the steam temperature required by two paths, and the purpose of reasonably adjusting steam parameters is achieved.
The steam inlet end and the steam outlet end of the aluminum oxide preparation process system 4 are respectively provided with an inlet regulating valve IV 4-1 and an outlet regulating valve IV 4-2, and the amount of steam entering the aluminum oxide preparation process system 4 and the amount of steam coming out of the aluminum oxide preparation process system 4 are regulated through the inlet regulating valve IV 4-1 and the outlet regulating valve IV 4-2.
And a steam inlet end and a steam outlet end of the heating system 3 are respectively provided with a third inlet regulating valve and a third outlet regulating valve, and the steam quantity entering the heating system 3 and the steam quantity coming out of the heating system 3 are regulated through the third inlet regulating valve and the third outlet regulating valve.
And the steam inlet end and the steam outlet end of the lithium bromide absorption refrigerating unit are respectively provided with an inlet regulating valve II 1-1 and an outlet regulating valve II 1-2, and the steam quantity entering the lithium bromide absorption refrigerating unit and the steam quantity coming out of the lithium bromide absorption refrigerating unit are regulated through the inlet regulating valve II 1-1 and the outlet regulating valve II 1-2.
The post-combustion boiler 2 can use natural gas or coal as fuel.
The lithium bromide absorption refrigerating unit comprises a high-temperature regenerator 5, a low-temperature regenerator 9, a condenser 10, an evaporator 11, an absorber 13, a low-temperature heat exchanger 16, a heat recoverer 7, a high-temperature heat exchanger 17 and other equipment, and the specific steam-water trend is as follows:
A. waste heat steam enters a high-temperature regenerator 5 of the lithium bromide absorption refrigerating unit through a steam inlet regulating valve II 1-1 and is used as a heat source to heat absorption liquid intermediate liquid of the high-temperature regenerator 5 to generate refrigerant steam, and then the waste heat steam returns to a flue gas heat exchanger 1 through a steam trap 6, a heat recoverer 7, an outlet regulating valve II 1-2 and a heat exchanger circulating water pump 8.
B. The refrigerant steam generated by the high-temperature regenerator 5 passes through the first steam-water separator 5-1 to the low-temperature regenerator 9, and the concentrated solution of the absorption liquid in the low-temperature regenerator 9 is continuously heated to generate more refrigerant steam. The part of the refrigerant steam passes through the second steam-water separator 9-1 to the condenser 10 to be condensed into refrigerant water together with the refrigerant steam from the high-temperature regenerator 5.
C. The refrigerant water generated in the condenser 10 is sent to the evaporator 11 through a pipeline, the refrigerant water in the evaporator 11 forms a self-circulation loop through the refrigerant pump 12 and the evaporator sprayer 11-1, the sprayed refrigerant water evaporates and absorbs heat to generate steam to enter the absorber 13, the back water of the chilled water from the cold load user 20 is cooled to be low-temperature chilled water through the evaporation and heat absorption effect, and the low-temperature chilled water is supplied to the cold load user 20.
D. The vapor generated by the evaporator 11 enters the absorber 13, and is absorbed and mixed by the absorption liquid concentrated solution sprayed by the absorber sprayer 13-1 to become the absorption liquid dilute solution.
E. The dilute solution of the absorption liquid in the absorber 13 returns to the high-temperature regenerator 5 through the second absorption liquid pump 15, the low-temperature heat exchanger 16, the heat recoverer 7 and the high-temperature heat exchanger 17.
F. The intermediate solution of the absorption liquid overflowing from the high-temperature regenerator 5 is sent to the low-temperature regenerator 9 through the high-temperature heat exchanger 17.
G. The concentrated absorption liquid solution in the low-temperature regenerator 9 is sent to the absorber 13 through the first absorption liquid pump 14 and the heat exchanger 16.
H. The normal temperature cooling water required by the lithium bromide absorption refrigerating unit absorbs heat from the cooling water inlet 18 through the absorber 13 and heats up, and then absorbs heat from the condenser 10 and heats up, and finally is discharged from the cooling water outlet 19.
In fig. 1, a low-temperature regenerator 9 and a condenser 10 are connected together, the low-temperature regenerator 9 is arranged on the left, the condenser 10 is arranged on the right, and a second steam-water separator 9-1 is an internal component of the low-temperature regenerator 9.
Also, as shown in fig. 1, the evaporator 11 and the absorber 13 are connected together, the left portion being 11, the right portion being 13, the evaporator shower 11-1 being an internal component of the evaporator 11, and the absorber shower 13-1 being an internal component of the absorber 13.
According to the design of the further structure, the principle of the system is as follows:
when the aluminum oxide preparation process system 4 is put into operation, the waste heat smoke of the electrolytic cell can only heat the steam to 120-150 ℃ and cannot be used for the aluminum oxide preparation process, but the afterburning boiler 2 can provide high-temperature steam of 250-300 ℃ for the aluminum oxide preparation process system 4; the load of the after-combustion boiler 2 is adjusted according to the load of the alumina preparation process system 4 and the load of the flue gas heat exchanger 1, namely the load is adjusted through a by-pass valve 2-3, an inlet adjusting valve I2-1, an outlet adjusting valve I2-2, an inlet adjusting valve IV 4-1 and an outlet adjusting valve IV 4-2 of the after-combustion boiler respectively. The steam heated by the waste heat and smoke of the aluminum electrolytic cell is sent to the afterburning boiler 2 for further heating, and the steam parameters are improved, so that high-temperature steam required by the alumina preparation process can be provided.
In summer, the heating system 3, the inlet regulating valve III 3-1 and the outlet regulating valve III 3-2 are closed; steam generated by the flue gas heat exchanger 1 is sent to the lithium bromide absorption refrigerating unit to be used for heat exchange, and meanwhile, the afterburning boiler 2 supplements a proper amount of high-temperature steam to the lithium bromide absorption refrigerating unit when necessary. Different cooling demands are provided for electrolytic aluminum factories, peripheral residents and industrial areas, and low-quality waste heat resources can be effectively utilized to drive a refrigerating unit to generate chilled water so as to meet the cooling demands of users.
In winter, the lithium bromide absorption refrigerating unit, the inlet regulating valve II 1-1 and the steam outlet regulating valve II 1-2 are closed, steam generated by the flue gas heat exchanger 1 is sent to the heating system 3 for heating, and meanwhile, the afterburning boiler 2 supplements appropriate high-temperature steam to the heating system 3 when necessary. Particularly, the northern area has cold weather, the electrolytic aluminum plant area, the surrounding residents and the industrial area have different heating requirements, and at the moment, the steam or hot water after the heat exchange of the waste heat of the flue gas of the electrolytic cell can be directly used as a heating source.
Claims (5)
1. A comprehensive utilization system for recovering the flue gas waste heat of an aluminum electrolysis cell is characterized in that: the system comprises a flue gas heat exchanger (1), a lithium bromide absorption refrigerating unit, an alumina preparation process system (4), a afterburning boiler (2), a heating system (3) and corresponding connecting pipelines; the flue gas heat exchanger (1) exchanges heat with flue gas (21) of the electrolytic cell, and steam generated by the flue gas heat exchanger (1) is output to three heat recovery utilization pipelines respectively:
a first pipeline, a steam output pipeline of the flue gas heat exchanger (1) is connected to the alumina preparation process system (4) through the afterburning boiler (2) and is supplied to the alumina preparation process system (4);
a second pipeline, wherein a steam output pipeline of the flue gas heat exchanger (1) is connected to the lithium bromide absorption refrigerating unit to supply steam to the lithium bromide absorption refrigerating unit, and a steam output loop of the lithium bromide absorption refrigerating unit is connected to the flue gas heat exchanger (1);
the steam output pipeline of the flue gas heat exchanger (1) is simultaneously connected to the heating system (3) to supply steam to the heating system (3), and the steam output loop of the heating system (3) is connected to the flue gas heat exchanger (1);
the heat recovery circuit is configured to be placed in service:
in summer, the lithium bromide absorption refrigerating unit and the alumina preparation process system (4) are put into use, and the heating system (3) and corresponding pipelines are not put into use;
in winter, the heating system (3) and the alumina preparation process system (4) are put into use, and the lithium bromide absorption refrigerating unit and the corresponding pipeline are not put into use; the steam output pipeline of the flue gas heat exchanger (1) is divided into two steam output branches which are connected in parallel, wherein one steam output branch is a afterburning boiler branch, and the other steam output branch is an afterburning boiler bypass; a post-combustion boiler bypass valve (2-3) is arranged on the post-combustion boiler bypass and is respectively connected to the lithium bromide absorption refrigerating unit and the heating system (3) through the post-combustion boiler bypass valve (2-3); on the afterburning boiler branch road, the steam input end of afterburning boiler (2) is provided with inlet regulating valve one (2-1), and the steam output end of afterburning boiler (2) sets up two branch roads, wherein: the first branch is a temperature increasing branch and is used for providing high-temperature steam for the alumina preparation process system (4), and the temperature range of the high-temperature steam is 250-300 ℃; the other branch is a steam supplementing branch, an outlet regulating valve I (2-2) is arranged on the steam supplementing branch, and the steam supplementing branch is respectively used for providing supplementing steam for a heating system (3) and the lithium bromide absorption type refrigerating unit through the outlet regulating valve I (2-2);
the steam inlet end and the steam outlet end of the lithium bromide absorption refrigerating unit are respectively provided with an inlet regulating valve II (1-1) and an outlet regulating valve II (1-2), and the amount of steam entering the lithium bromide absorption refrigerating unit and the amount of steam coming out of the lithium bromide absorption refrigerating unit are regulated through the inlet regulating valve II (1-1) and the outlet regulating valve II (1-2); the lithium bromide absorption refrigerating unit comprises a high-temperature regenerator (5), a low-temperature regenerator (9), a condenser (10), an evaporator (11), an absorber (13), a low-temperature heat exchanger (16), a heat recoverer (7) and a high-temperature heat exchanger (17), and the specific steam-water trend is as follows:
A. waste heat steam enters a high-temperature regenerator (5) of the lithium bromide absorption refrigerating unit through an inlet regulating valve II (1-1), absorption liquid intermediate liquid of the high-temperature regenerator (5) heated as a heat source generates refrigerant steam, and then the waste heat steam returns to the flue gas heat exchanger (1) through a steam trap (6), a heat recoverer (7), an outlet regulating valve II (1-2) and a heat exchanger circulating water pump (8);
B. refrigerant steam generated by the high-temperature regenerator (5) passes through the first steam-water separator (5-1) to the low-temperature regenerator (9), the concentrated solution of the absorption liquid in the low-temperature regenerator (9) is continuously heated to generate more refrigerant steam, and the generated refrigerant steam passes through the second steam-water separator (9-1) to the condenser (10) to be condensed into refrigerant water together with the refrigerant steam from the high-temperature regenerator (5);
C. refrigerant water generated in the condenser (10) is sent to the evaporator (11) through a pipeline, the refrigerant water in the evaporator (11) forms a self-circulation loop through a refrigerant pump (12) and an evaporator sprayer (11-1), the refrigerant water sprayed by the evaporator sprayer (11-1) evaporates and absorbs heat to generate steam which enters an absorber (13), the evaporation and heat absorption effect enables the backwater of the chilled water from a cold load user (20) to be cooled into low-temperature chilled water, and the low-temperature chilled water is supplied to the cold load user (20);
D. steam generated by the evaporator (11) enters the absorber (13) and is absorbed and mixed by the concentrated absorption liquid solution sprayed by the absorber sprayer (13-1) to become a dilute absorption liquid solution;
E. the absorption liquid dilute solution in the absorber (13) returns to the high-temperature regenerator (5) through an absorption liquid pump II (15), a low-temperature heat exchanger (16), a heat recoverer (7) and a high-temperature heat exchanger (17) in sequence;
F. the absorption liquid intermediate solution overflowing from the high-temperature regenerator (5) is sent to a low-temperature regenerator (9) through a high-temperature heat exchanger (17);
G. the concentrated solution of the absorption liquid in the low-temperature regenerator (9) is sent to an absorber (13) through a first absorption liquid pump (14) and a heat exchanger (16);
H. the normal-temperature cooling water required by the lithium bromide absorption refrigerating unit absorbs heat from a cooling water inlet (18) through an absorber (13) and is heated, then absorbs heat from a condenser (10) and is heated, and finally the normal-temperature cooling water is discharged from a cooling water outlet (19).
2. The comprehensive utilization system for recovering the flue gas waste heat of the aluminum electrolysis cell according to claim 1, which is characterized in that: the steam inlet end and the steam outlet end of the alumina preparation process system (4) are respectively provided with an inlet regulating valve IV (4-1) and an outlet regulating valve IV (4-2), and the amount of steam entering the alumina preparation process system (4) and the amount of steam coming out of the alumina preparation process system (4) are regulated through the inlet regulating valve IV (4-1) and the outlet regulating valve IV (4-2).
3. The comprehensive utilization system for recycling the flue gas waste heat of the aluminum electrolytic cell according to claim 1, which is characterized in that: the steam inlet end and the steam outlet end of the heating system (3) are respectively provided with a third inlet adjusting valve and a third outlet adjusting valve, and the steam quantity entering the heating system (3) and the steam quantity coming out of the heating system (3) are adjusted through the third inlet adjusting valve and the third outlet adjusting valve.
4. The comprehensive utilization system for recycling the flue gas waste heat of the aluminum electrolysis cell as recited in claim 1, wherein the comprehensive utilization principle comprises:
when the alumina preparation process system (4) is put into use, the afterburning boiler (2) provides high-temperature steam for the alumina preparation process system (4); the load of the afterburning boiler (2) is adjusted according to the load of the alumina preparation process system (4) and the load of the flue gas heat exchanger (1), namely the load is adjusted through a afterburning boiler bypass valve (2-3), an inlet adjusting valve I (2-1), an outlet adjusting valve I (2-2), an inlet adjusting valve IV (4-1) and an outlet adjusting valve IV (4-2) respectively;
in summer, the heating system (3), the inlet regulating valve III (3-1) and the outlet regulating valve III (3-2) are closed, steam generated by the flue gas heat exchanger (1) is sent to the lithium bromide absorption refrigerating unit to be used as heat exchange, and meanwhile, the afterburning boiler (2) supplements high-temperature steam to the lithium bromide absorption refrigerating unit according to specific conditions;
in winter, the lithium bromide absorption refrigerating unit, the inlet regulating valve II (1-1) and the outlet regulating valve II (1-2) are closed, steam generated by the flue gas heat exchanger (1) is sent to the heating system (3) for heating, and meanwhile, the afterburning boiler (2) supplements high-temperature steam to the heating system (3) when necessary.
5. The comprehensive utilization system for recycling the flue gas waste heat of the aluminum electrolytic cell according to claim 1, which is characterized in that: the afterburning boiler (2) adopts natural gas or coal as fuel.
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