CN116625026A - Energy-saving ammonia refrigerating system for ammonia synthesis device and energy-saving method thereof - Google Patents
Energy-saving ammonia refrigerating system for ammonia synthesis device and energy-saving method thereof Download PDFInfo
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- CN116625026A CN116625026A CN202310912297.8A CN202310912297A CN116625026A CN 116625026 A CN116625026 A CN 116625026A CN 202310912297 A CN202310912297 A CN 202310912297A CN 116625026 A CN116625026 A CN 116625026A
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- ammonia
- temperature
- cooler
- energy
- lithium bromide
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 558
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 243
- 238000000034 method Methods 0.000 title claims abstract description 32
- 230000015572 biosynthetic process Effects 0.000 title claims description 26
- 238000003786 synthesis reaction Methods 0.000 title claims description 26
- 239000000463 material Substances 0.000 claims abstract description 75
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 71
- 238000001704 evaporation Methods 0.000 claims abstract description 38
- 230000008020 evaporation Effects 0.000 claims abstract description 38
- 238000004781 supercooling Methods 0.000 claims abstract description 8
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 4
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 claims description 98
- 238000005057 refrigeration Methods 0.000 claims description 57
- 238000001816 cooling Methods 0.000 claims description 48
- 230000008569 process Effects 0.000 claims description 16
- 238000000746 purification Methods 0.000 claims description 12
- 239000003638 chemical reducing agent Substances 0.000 claims description 9
- 238000009826 distribution Methods 0.000 claims description 5
- 238000004134 energy conservation Methods 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 13
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000000498 cooling water Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Classifications
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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
- F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
- F25B25/02—Compression-sorption machines, plants, or systems
-
- 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
- F25B40/00—Subcoolers, desuperheaters or superheaters
- F25B40/02—Subcoolers
-
- 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
- F25B41/00—Fluid-circulation arrangements
- F25B41/40—Fluid line arrangements
-
- 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
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
Abstract
The invention belongs to the field of synthetic ammonia, and in particular relates to an energy-saving ammonia refrigerating system for an ammonia synthesizing device and an energy-saving method thereof. According to the invention, on one hand, the supercooling degree of liquid ammonia fed into the liquid ammonia tank is improved through the liquid ammonia supercooler, the temperature of liquid ammonia supplied to the ammonia evaporation cooler group is reduced, the refrigerating capacity of unit mass liquid ammonia evaporation is improved, and on the other hand, the material cooled by the circulating water cooler is further cooled through the low-temperature water cooler, so that the ammonia evaporation requirement is reduced, the steam consumption of the condensing steam turbine is further reduced, and the purpose of energy conservation is achieved.
Description
Technical Field
The invention belongs to the field of synthetic ammonia, and particularly relates to an energy-saving ammonia refrigeration system for a synthetic ammonia device and an energy-saving method thereof.
Background
The technological process of the ammonia synthesizing device mainly comprises the technological steps of gas making, conversion, purification, ammonia synthesis and the like. In the process of production, according to the requirements of process material flows on temperature levels, materials are cooled and condensed by means of normal-temperature circulating cooling water cooling, cold-heat exchange among materials, ammonia evaporation cooling, deep cooling and the like, so that the purposes of separating, purifying and cooling the materials are achieved.
In the technological process, the low temperature methanol at-38 ℃ in the purification section, the usable H2 material, the sulfur-containing/sulfur-free rich methanol which needs to be cooled to-38 ℃, the H2S fraction which needs to be cooled to-35 ℃, the low temperature cooling at-8 ℃ in the ammonia separation in the synthesis section and the like are needed, and a large amount of cooling load can be achieved. Due to the temperature level, the cooling water can not be directly circulated at normal temperature, and a lithium bromide refrigerator at 7 ℃ or a conventional electric refrigerator can not be directly realized. Therefore, in the ammonia synthesis device, the characteristic that the low temperature can be achieved by utilizing the ammonia evaporation is obtained locally, the ammonia synthesis device is realized through an ammonia refrigerating system, and as the three-stage ammonia compressor group is conventionally arranged according to the refrigerating temperatures of different temperature stages required in the ammonia synthesis device, the evaporated gas ammonia in loops of different temperature stages and corresponding different evaporation pressure stages is compressed.
The existing ammonia refrigeration systems have the following problems: in a large-scale ammonia synthesis device, the device is driven by the action of a condensing steam turbine. The higher the ammonia refrigeration load, the more power the ammonia compressor needs to be driven, the more steam is consumed, and the capacity is limited and production operation is affected due to the limited capacity of the equipment. For energy saving and safe production, effectively reducing the load of an ammonia refrigeration system is a problem to be solved urgently by related practitioners.
Disclosure of Invention
In order to make up for the defects of the prior art, the invention provides an energy-saving ammonia refrigeration system for an ammonia synthesis device and an energy-saving method technical scheme thereof.
The utility model provides an energy-saving ammonia refrigerating system for synthetic ammonia device, includes ammonia compressor group, gas ammonia circulating water cooling condenser, liquid ammonia groove and the ammonia evaporative cooler group that loops through the pipe connection in proper order, ammonia compressor group cooperation is connected and is used for driving its condenser steam turbine of work, the material return circuit is connected in the ammonia evaporative cooler group cooperation, set up on the material return circuit and be used for carrying out refrigerated circulating water cooler to the material, set up the liquid ammonia subcooler on the pipeline between gas ammonia circulating water cooling condenser and the liquid ammonia groove, still set up low temperature water cooler on the material return circuit, low temperature water cooler is used for further cooling to the material through circulating water cooler refrigerated.
Further, the liquid ammonia subcooler and the low-temperature water cooler are connected with a lithium bromide refrigerating unit through pipelines.
Further, the lithium bromide refrigerating unit is a steam type lithium bromide refrigerating unit, the steam type lithium bromide refrigerating unit is connected with a temperature and pressure reducer through a pipeline, and the temperature and pressure reducer reduces the temperature and pressure of the main steam of the condensing steam turbine part to the steam inlet parameter required by the steam type lithium bromide refrigerating unit, so that the steam type lithium bromide refrigerating unit can prepare low-temperature water.
Further, the ammonia compressor group comprises M ammonia compressors which are determined according to the number of process temperature stages and are sequentially connected in series, the ammonia evaporative cooler group comprises N ammonia evaporative coolers which are connected with the ammonia compressors through pipelines, N and M are positive integers which are larger than 1, and N is larger than or equal to M.
Further, the number of the material loops is N, and N is a positive integer not greater than N.
Further, the ammonia compressor group comprises 3 ammonia compressors which are sequentially connected in series, namely a first-stage ammonia compressor, a second-stage ammonia compressor and a third-stage ammonia compressor, 2 material loops are respectively a purification section material refrigerating loop and a synthesis section material refrigerating loop, the ammonia evaporative cooler group comprises three ammonia evaporative coolers which are respectively a first-stage ammonia evaporative cooler connected with the first-stage ammonia compressor through pipelines, a second-stage ammonia evaporative cooler connected with the second-stage ammonia compressor through pipelines and a third-stage ammonia evaporative cooler connected with the third-stage ammonia compressor through pipelines, the purification section material refrigerating loop is connected with the first-stage ammonia evaporative cooler, the synthesis section material refrigerating loop is connected with the second-stage ammonia evaporative cooler and the third-stage ammonia evaporative cooler, and materials output by the synthesis section material refrigerating loop are subjected to two-stage cooling of the second-stage ammonia evaporative cooler and the third-stage ammonia evaporative cooler.
Further, the ammonia compressor system further comprises a surge loop, wherein the surge loop is connected between the liquid ammonia tank and the ammonia compressor group and is used for compensating liquid ammonia for the ammonia compressor group, and a surge valve is arranged on the surge loop.
The invention also includes an energy saving method for use in an ammonia refrigeration system as described above, comprising:
after the air ammonia circulating water cooling condenser condenses the air ammonia into liquid ammonia, the liquid ammonia is subjected to supercooling treatment through the liquid ammonia supercooler, so that the supercooling degree of the liquid ammonia entering the liquid ammonia tank is improved, the temperature of the liquid ammonia supplied to the ammonia evaporation cooler group is reduced, the refrigerating capacity of evaporation of unit mass liquid ammonia is improved, and the ammonia evaporation requirement is reduced;
after the circulating water cooler performs primary cooling on the material, the material is further cooled by the low-temperature water cooler so as to further reduce the temperature of the material, thereby reducing the ammonia evaporation requirement.
Further, the liquid ammonia subcooler and the low-temperature water cooler are cooled by a lithium bromide refrigerating unit, and the cold energy distribution method of the lithium bromide refrigerating unit comprises the following steps:
the method comprises the steps of calculating the percentage of the mass of ammonia consumed by each ammonia evaporative cooler to the mass of the total ammonia consumed according to the refrigeration load of each ammonia evaporative cooler and the mass of ammonia to be evaporated corresponding to the unit refrigeration capacity of the temperature stage, and distributing cold capacity of a lithium bromide refrigerating unit according to the following formula so as to keep the mass proportion of each temperature stage ammonia loop balanced:
Q i =k i (Q total (S) -Q Remainder of the process ),i=1,2...n
Wherein n is the number of material loops; q (Q) Total (S) The total cold quantity of the lithium bromide refrigerating unit; q (Q) i The cooling capacity of the ith material loop is allocated to the lithium bromide refrigerating unit; k (k) i The sum of the mass of ammonia consumed by all ammonia evaporative coolers in the ith material loop is the percentage of the mass of ammonia consumed in total; q (Q) Remainder of the process The cooling capacity of the liquid ammonia subcooler is distributed for the lithium bromide refrigerating unit.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, on one hand, the supercooling degree of liquid ammonia fed into the liquid ammonia tank is improved through the liquid ammonia supercooler, the temperature of liquid ammonia supplied to the ammonia evaporation cooler group is reduced, the refrigerating capacity of unit mass liquid ammonia evaporation is improved, and on the other hand, the material cooled by the circulating water cooler is further cooled through the low-temperature water cooler, so that the ammonia evaporation requirement is reduced, the load of an ammonia refrigerating system is effectively reduced, the steam consumption of a condensing steam turbine is reduced, and the purpose of energy conservation is achieved.
Drawings
FIG. 1 is a schematic diagram of an energy-saving ammonia refrigeration system for an ammonia synthesis device according to the present invention.
FIG. 2 is a schematic diagram of a material refrigeration circuit in a purification section of an energy-saving ammonia refrigeration system for an ammonia synthesis device according to the present invention.
FIG. 3 is a schematic diagram of a material refrigeration loop in a synthesis section of an energy-saving ammonia refrigeration system for an ammonia synthesis device according to the present invention.
In the figure:
1 is a condensing steam turbine;
2a is a primary ammonia compressor;
2b is a secondary ammonia compressor;
2c is a tertiary ammonia compressor;
3 is a gas ammonia circulating water cooling condenser;
4 is a liquid ammonia tank;
5a is a primary ammonia evaporative cooler;
5b is a secondary ammonia evaporative cooler;
5c is a three-stage ammonia evaporative cooler;
6 is a surge valve;
7a is a first circulating water cooler;
7b is a second circulating water cooler;
8 is an ammonia evaporation regulating valve;
9 is a liquid ammonia subcooler;
10a is a first low-temperature water cooler;
10b is a second low-temperature water cooler;
11 is a lithium bromide refrigerating unit;
12 is a temperature and pressure reducer;
13 is a material refrigeration loop of the purification section;
and 14 is a material refrigeration loop of a synthesis section.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1-3, an energy-saving ammonia refrigeration system for an ammonia synthesis device comprises an ammonia compressor group, an ammonia gas circulating water cooling condenser 3, a liquid ammonia tank 4 and an ammonia evaporation cooler group which are sequentially connected through pipelines and form a circulating loop, wherein the ammonia compressor group is matched and connected with a condensing steam turbine 1 for driving the ammonia compressor group to work, the ammonia evaporation cooler group is matched and connected with a material loop, a circulating water cooler for cooling materials is arranged on the material loop, a liquid ammonia subcooler 9 is arranged on a pipeline between the ammonia gas circulating water cooling condenser 3 and the liquid ammonia tank 4, and a low-temperature water cooler is further arranged on the material loop and is used for cooling the materials cooled by the circulating water cooler.
With continued reference to fig. 1, the ammonia compressor set includes 3 ammonia compressors, namely a primary ammonia compressor 2a, a secondary ammonia compressor 2b and a tertiary ammonia compressor 2c, which are sequentially connected in series, the ammonia evaporative cooler set includes three ammonia evaporative coolers, namely a primary ammonia evaporative cooler 5a connected with the primary ammonia compressor 2a through a pipeline, a secondary ammonia evaporative cooler 5b connected with the secondary ammonia compressor 2b through a pipeline and a tertiary ammonia evaporative cooler 5c connected with the tertiary ammonia compressor 2c through a pipeline, the cooling temperature of the primary ammonia evaporative cooler 5a is-38 ℃, the cooling temperature of the secondary ammonia evaporative cooler 5b is-8 ℃, the cooling temperature of the tertiary ammonia evaporative cooler 5c is 10 ℃, an ammonia evaporative regulating valve 8 is arranged at the inlet of each ammonia evaporative cooler, 2 material loops are respectively a purification section material refrigerating loop 13 and a synthesis section material refrigerating loop 14, and as shown in fig. 2, a first circulating water cooler 7a, a first low-temperature water cooler 10a and a primary ammonia evaporative cooler 5a are sequentially arranged on the purification section material refrigerating loop 13. As shown in fig. 3, the synthesis section material refrigeration loop 14 is sequentially provided with a second circulating water cooler 7b, a second low-temperature water cooler 10b, a second-stage ammonia evaporative cooler 5b and a third-stage ammonia evaporative cooler 5c, and the material output by the synthesis section material refrigeration loop 14 is subjected to two-stage cooling by the second-stage ammonia evaporative cooler 5b and the third-stage ammonia evaporative cooler 5 c.
Further, the liquid ammonia subcooler 9 and the low-temperature water cooler are connected with the lithium bromide refrigeration unit 11 together through a pipeline, the lithium bromide refrigeration unit 11 is preferably a steam type lithium bromide refrigeration unit, the steam type lithium bromide refrigeration unit is connected with the temperature and pressure reducer 12 through a pipeline, and the temperature and pressure reducer 12 reduces the temperature and pressure of part of main steam of the condensing steam turbine 1 to the steam inlet parameter required by the steam type lithium bromide refrigeration unit, so that the steam type lithium bromide refrigeration unit can prepare low-temperature water.
Further, the energy-saving ammonia refrigeration system further comprises a surge loop, wherein the surge loop is connected between the liquid ammonia tank and the ammonia compressor group and is used for compensating liquid ammonia for the ammonia compressor group, and a surge valve 6 is arranged on the surge loop.
Specifically, the surge loop has 3, is connected with 3 ammonia compressors one-to-one, and when ammonia compressor load is too little, corresponding surge valve 6 can open, introduces a part of liquid ammonia to this ammonia compressor to increase load, prevents ammonia compressor surge.
It should be noted that the number of ammonia evaporative coolers in the ammonia evaporative cooler group can be adjusted as required, and the numbers of ammonia compressors and material loops are correspondingly adjusted.
During operation, the liquid ammonia tank 4 supplies liquid ammonia for the ammonia evaporation cooler, the ammonia evaporation cooler and the low-temperature water cooler are used for cooling materials, gas ammonia evaporated by the ammonia evaporation cooler is directly connected to a corresponding ammonia compressor, the ammonia compressor group pressurizes the gas ammonia, then the gas ammonia after pressurization is condensed by the gas ammonia circulating water cooling condenser 3 to form liquid ammonia, the liquid ammonia is further cooled by the liquid ammonia subcooler 9, and finally flows back to the liquid ammonia tank 4 in a backflow mode.
The low-temperature water cooler is preferably a 7 ℃ water cooler, and the cooling temperature is lower than that of the circulating water cooler. The cooling temperature of the liquid ammonia subcooler is lower than that of the gas ammonia circulating water cooling condenser.
The invention also provides an energy-saving method which is applied to the ammonia refrigeration system and comprises the following steps: first, after the gas ammonia is condensed into liquid ammonia by the gas ammonia circulating water cooling condenser 3, the liquid ammonia is supercooled by the liquid ammonia supercooler 9 to increase the supercooling degree of the liquid ammonia entering the liquid ammonia tank 4, reduce the liquid ammonia temperature supplied to the ammonia evaporation cooler group, and increase the refrigerating capacity of evaporation of liquid ammonia per unit mass, thereby reducing the ammonia evaporation demand. And secondly, after the circulating water cooler performs primary cooling on the material, the material is further cooled by the low-temperature water cooler so as to further reduce the temperature of the material, thereby reducing the ammonia evaporation requirement.
The method for calculating the total cold demand of the low-temperature water comprises the following steps:
1. the actual production data of the specific ammonia synthesis process device is researched and used as the basis of analysis and calculation. The investigation includes the highest freezing load of each temperature stage loop of the ammonia compressor, the surge line of each ammonia compressor, and the same material flow which is finally refrigerated by ammonia evaporation can pass through a circulating cooling water cooler, a material heat exchanger and the material inlet and outlet temperature/pressure, the material flow, the material composition, the mass or mol or volume percentage and the liquid phase fraction of each section of the ammonia evaporation cooler in sequence, and the material temperature required by the final process design.
2. According to the total maximum refrigeration load of production and the surge line load of each ammonia compressor, and by combining the balance requirement factors of each temperature stage loop, the maximum refrigeration load which can be reduced compared with the maximum refrigeration load of the ammonia compressor group is calculated, namely the maximum refrigeration capacity of the low-temperature water made by the lithium bromide refrigeration unit 11 is needed to be matched.
3. And determining the steam demand, temperature and pressure of the low-temperature water produced by the lithium bromide refrigeration unit 11 according to the maximum cold supply capacity of the low-temperature water and the equipment parameters of the lithium bromide refrigeration machine.
4. The steam temperature and pressure reducer 12 is utilized to reduce the temperature and pressure of the part of main steam of the steam turbine for driving the ammonia compressor to the steam inlet parameters required by the steam type lithium bromide refrigerator set, so that the lithium bromide refrigerator set 11 can prepare low-temperature water. The number of the lithium bromide refrigerating units 11 is determined according to equipment arrangement conditions, equipment manufacturer parameters and process cooling change amplitude.
5. If the process device has high-temperature waste heat resources (such as high-temperature condensed water, unused exhaust steam and the like), the waste heat resources can be utilized for refrigerating the lithium bromide refrigerating unit 11, so that the consumption of high-grade main steam is further saved.
Wherein, the liquid ammonia subcooler 9 and the low-temperature water cooler are cooled by the lithium bromide refrigeration unit 11, and the cold energy distribution method of the lithium bromide refrigeration unit 11 is as follows:
for the material loop with the temperature higher than 15 ℃ before entering each ammonia evaporation cooler, the percentage of the total ammonia consumption mass of each ammonia evaporation cooler is calculated according to the refrigeration load of each ammonia evaporation cooler and the ammonia mass to be evaporated of the unit refrigeration capacity of the corresponding temperature stage, and the lithium bromide refrigerating unit 11 distributes the refrigeration capacity according to the following formula, so that the mass proportion of each temperature stage ammonia loop is balanced:
Q i =k i (Q total (S) -Q Remainder of the process ),i=1,2...n
Wherein n is the number of material loops; q (Q) Total (S) Is the total cold energy of the lithium bromide refrigeration unit 11; q (Q) i The cooling capacity of the ith material loop is distributed to the lithium bromide refrigerating unit 11; k (k) i The sum of the mass of ammonia consumed by all ammonia evaporative coolers in the ith material loop is the percentage of the mass of ammonia consumed in total; q (Q) Remainder of the process The cooling capacity of the liquid ammonia subcooler 9 is allocated to the lithium bromide refrigeration unit 11.
Examples
1. Original system equipment configuration
An ammonia refrigerating system matched with a 30 ten thousand ton/year ammonia synthesizing device.
1. Rated condition of ammonia compressor
2. The ammonia compressor driving power source is a matched condensing steam turbine 1 unit, rated working condition
2. System analysis and reconstruction method
Aiming at the defect of the original operation of the device, the invention adopts the following scheme:
cooling capacity demand and distribution scheme
1. According to the highest refrigeration load of each temperature-stage loop of the project investigation production device, compared with the load when ammonia compressor surge occurs, the highest refrigeration load quantity of the ammonia compressor group, namely the maximum cooling capacity of 7 ℃ matched water, is determined by combining the balance requirement factors of each temperature-stage loop (therefore, exceeding the load reduction amplitude inevitably causes the ammonia compressor group to work below a surge line to surge, and the surge valve 6 has to be opened to cause the ineffective work of the ammonia compressor to increase).
2. According to the maximum cooling capacity requirement of 7 ℃ water and the parameters of a lithium bromide refrigerator, determining the steam quantity required by 7 ℃, dividing the main steam of a steam inlet turbine by 4.75t/h through a temperature and pressure reducer 12, and reducing the temperature by 0.9t/h and 104 ℃ to provide saturated steam of 5.65t/h and 0.8MPa.a of a steam type lithium bromide refrigerator set, thereby meeting the refrigerating capacity requirement of 2 steam type lithium bromide refrigerator sets of 250 kcal/h.
3. 2 sets of 250 kcal/H refrigerating capacity, namely 500 kcal/H in total, are configured, and are supplied to a 7 ℃ water pre-cooling heat exchanger, a purification section H2S fraction ammonia cooler, a 7 ℃ water pre-cooling heat exchanger and the like which are arranged behind a liquid ammonia tank 4 through a 7 ℃ water refrigerant medium, so that the refrigerating capacity of the ammonia refrigerating system is reduced by 500 kcal/H in total.
4. Wherein, on the water cooling capacity distribution of each 7 ℃, the supercooling of the liquid ammonia after the liquid ammonia tank 4 does not influence the balance of each downstream temperature stage loop, and the maximum application principle is adopted; the residual water cooling capacity of 7 ℃ is distributed to each temperature-stage loop by the principle of the same ammonia evaporation mass reduction of each loop, which is favorable for the ammonia balance of each temperature-stage loop and the prevention of surge of an ammonia compressor, and the evaporation latent heat is different under the condition of different evaporation temperatures/pressures of ammonia, and is calculated and implemented for debugging, wherein the water cooling capacity of 7 ℃ is distributed to 115 kcal/h of a liquid ammonia subcooler 9 (for reducing the evaporation capacity of integral ammonia) behind a liquid ammonia tank 4, 249 kcal/h of a 7 ℃ water precooling heat exchanger (for reducing the total ammonia evaporation capacity of minus 8 ℃ and 10 ℃ temperature stages) behind a synthetic gas circulating water cooler, and the 7 ℃ water precooling heat exchanger (for reducing the evaporation capacity of minus 38 ℃ temperature stages of ammonia) in a purification section totalizes 136 kcal/h.
(II) actual energy saving effect
1. The steam consumption of the steam turbine after transformation is 32.76t/h, the steam is added with 4.75t/h of the steam which is distributed to the steam type lithium bromide refrigerating unit, the total steam consumption of the ammonia refrigerating system after transformation is reduced to 37.5t/h, and compared with the original steam consumption of 43.56t/h, the steam consumption of 3.9MPa.a and the steam consumption of 6.06t/h at 400 ℃ are saved, and the comprehensive steam saving rate is 13.9%.
2. If the refrigeration load is lower, the same steam saving amount is achieved when 500 kcal/h is fused, and the comprehensive steam saving rate is higher due to the low energy consumption base number of the steam turbine.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (9)
1. The utility model provides an energy-saving ammonia refrigerating system for synthetic ammonia device, includes ammonia compressor group, gas ammonia circulating water cooling condenser (3), liquid ammonia groove (4) and the ammonia evaporative cooler group that loops through the pipe connection in proper order, ammonia compressor group cooperation is connected and is used for driving condensing steam turbine (1) of its work, the material return circuit is connected in the ammonia evaporative cooler group cooperation, set up on the material return circuit and be used for carrying out refrigerated circulating water cooler to the material, its characterized in that, set up liquid ammonia subcooler (9) on the pipeline between gas ammonia circulating water cooling condenser and the liquid ammonia groove (4), still set up low-temperature water cooler on the material return circuit, low-temperature water cooler is used for further cooling to the material through circulating water cooler refrigerated.
2. The energy-saving ammonia refrigeration system for an ammonia synthesis device according to claim 1, wherein the liquid ammonia subcooler and the low-temperature water cooler are connected together through a pipeline to a lithium bromide refrigeration unit (11).
3. The energy-saving ammonia refrigerating system for the ammonia synthesizing device according to claim 2, wherein the lithium bromide refrigerating unit (11) is a steam type lithium bromide refrigerating unit, the steam type lithium bromide refrigerating unit is connected with a temperature and pressure reducer (12) through a pipeline, and the temperature and pressure reducer (12) reduces the temperature and pressure of the main steam of the condensing steam turbine part to the steam inlet parameter required by the steam type lithium bromide refrigerating unit, so that the steam type lithium bromide refrigerating unit can prepare low-temperature water.
4. The energy-saving ammonia refrigeration system for an ammonia plant according to claim 1, wherein the ammonia compressor group comprises M ammonia compressors connected in series in sequence, which are determined according to the number of process temperature stages, the ammonia evaporative cooler group comprises N ammonia evaporative coolers connected with the ammonia compressors through pipelines, N and M are positive integers greater than 1, and N is greater than or equal to M.
5. The energy-saving ammonia refrigeration system for an ammonia plant of claim 4 wherein the number of material loops is N, N being a positive integer no greater than N.
6. An energy-saving ammonia refrigeration system for an ammonia plant according to claim 5, wherein the ammonia compressor group comprises 3 ammonia compressors (2 a), 2b and 2 c) which are sequentially connected in series, wherein the material loops are respectively 2, a purification section material refrigeration loop (13) and a synthesis section material refrigeration loop (14), the ammonia evaporative cooler group comprises three ammonia evaporative coolers, namely a first ammonia evaporative cooler (5 a) connected with the first ammonia compressor (2 a) through a pipeline, a second ammonia evaporative cooler (5 b) connected with the second ammonia compressor (2 b) through a pipeline and a third ammonia evaporative cooler (5 c) connected with the third ammonia compressor (2 c) through a pipeline, the purification section material refrigeration loop (13) is connected with the first ammonia evaporative cooler (5 a), the synthesis section material loop (14) is connected with the second ammonia evaporative cooler (5 b) and the third ammonia evaporative cooler (5 c), and the synthesis section material (14) is cooled by the second ammonia evaporative cooler (5 b) through a pipeline.
7. The energy-saving ammonia refrigeration system for an ammonia plant according to claim 4, further comprising a surge loop connected between the liquid ammonia tank (4) and the ammonia compressor train for compensating the ammonia compressor train for the liquid ammonia, wherein a surge valve (6) is provided on the surge loop.
8. A method of saving energy, applied to an ammonia refrigeration system according to any one of claims 1 to 7, comprising:
after the gas ammonia is condensed into liquid ammonia by the gas ammonia circulating water cooling condenser (3), the liquid ammonia is subjected to supercooling treatment by the liquid ammonia supercooler (9) so as to improve the supercooling degree of the liquid ammonia entering the liquid ammonia tank (4), reduce the temperature of the liquid ammonia supplied to the ammonia evaporation cooler group, and improve the refrigerating capacity of evaporation of liquid ammonia with unit mass, thereby reducing the ammonia evaporation requirement;
after the circulating water cooler performs primary cooling on the material, the material is further cooled by the low-temperature water cooler so as to further reduce the temperature of the material, thereby reducing the ammonia evaporation requirement.
9. The energy saving method according to claim 8, wherein the liquid ammonia subcooler and the low-temperature water cooler are cooled by a lithium bromide refrigerating unit (11), and the cold energy distribution method of the lithium bromide refrigerating unit is as follows:
the method comprises the steps of calculating the percentage of the mass of ammonia consumed by each ammonia evaporative cooler to the mass of the total ammonia consumed according to the refrigeration load of each ammonia evaporative cooler and the mass of ammonia to be evaporated corresponding to the unit refrigeration capacity of the temperature stage, and distributing the refrigeration capacity of a lithium bromide refrigeration unit (11) according to the following formula so as to keep the mass proportion of each temperature stage ammonia loop balanced:
Q i =k i (Q total (S) -Q Remainder of the process ),i=1,2...n
Wherein n is the number of material loops; q (Q) Total (S) Is the total cold energy of the lithium bromide refrigerating unit (11); q (Q) i The cooling capacity of the ith material loop is allocated to the lithium bromide refrigerating unit (11); k (k) i The sum of the mass of ammonia consumed by all ammonia evaporative coolers in the ith material loop is the percentage of the mass of ammonia consumed in total; q (Q) Remainder of the process The cooling capacity of the liquid ammonia subcooler is distributed to the lithium bromide refrigerating unit (11).
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