CN114606033A - Natural gas solvent absorption denitrification flash control system and parameter optimization method - Google Patents
Natural gas solvent absorption denitrification flash control system and parameter optimization method Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000002904 solvent Substances 0.000 title claims abstract description 99
- 238000010521 absorption reaction Methods 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 50
- 239000003345 natural gas Substances 0.000 title claims abstract description 49
- 238000005457 optimization Methods 0.000 title claims abstract description 14
- 239000007789 gas Substances 0.000 claims abstract description 104
- 239000007788 liquid Substances 0.000 claims abstract description 103
- 238000001514 detection method Methods 0.000 claims abstract description 36
- 238000009530 blood pressure measurement Methods 0.000 claims abstract description 26
- 238000004364 calculation method Methods 0.000 claims abstract description 7
- 238000005259 measurement Methods 0.000 claims abstract description 5
- 238000001704 evaporation Methods 0.000 claims description 56
- 230000008020 evaporation Effects 0.000 claims description 56
- 238000005070 sampling Methods 0.000 claims description 16
- 239000000443 aerosol Substances 0.000 claims description 6
- 238000007701 flash-distillation Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims 1
- 230000008569 process Effects 0.000 description 14
- 229930195733 hydrocarbon Natural products 0.000 description 5
- 150000002430 hydrocarbons Chemical class 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000004215 Carbon black (E152) Substances 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- 230000003044 adaptive effect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 238000005057 refrigeration Methods 0.000 description 2
- 239000011555 saturated liquid Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical class [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000004517 catalytic hydrocracking Methods 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000002068 genetic effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen(.) Chemical compound [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000013139 quantization Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/105—Removal of contaminants of nitrogen
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/06—Flash distillation
- B01D3/065—Multiple-effect flash distillation (more than two traps)
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D27/00—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00
- G05D27/02—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00 characterised by the use of electric means
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
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- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
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Abstract
A natural gas solvent absorption denitrification flash control system is characterized in that a liquid level detection device, a liquid flow control valve, a gas pressure measurement device and a flowmeter are arranged on each flash tank of a multi-stage flash subsystem, and the flow control is performed on the flash system through the operation state of the flash system analyzed and measured by a processor, so that the pressure in the flash tanks is accurately controlled; a natural gas solvent absorption denitrification flash control parameter optimization method includes setting flash tank gas pressure control target values of flash tank systems of multiple flash tank subsystems, determining initial setting values of liquid flow control valves according to the flash tank gas pressure control target values, collecting measurement data of a gas pressure measurement device, the liquid flow control valves and gas flow control valves in real time, determining adjustment value calculation methods of the liquid flow control valves according to gas pressure numerical values in a period of time, and calculating adjustment values, so that control parameters of natural gas solvent absorption denitrification flash are optimized and adjusted quickly and accurately.
Description
Technical Field
The invention relates to natural gas processing, in particular to a natural gas solvent absorption denitrification flash evaporation process, and specifically relates to a natural gas solvent absorption denitrification flash evaporation process optimization control system and a method thereof.
Background
As high-quality fuel and important chemical raw materials, natural gas is increasingly paid more attention to people in application, and the trend of accelerating the development of the natural gas industry is the world trend. However, natural gas produced in many oil and gas fields often contains a large amount of nitrogen, and natural gas with high nitrogen content has low calorific value and large energy consumption in the gathering and transportation process, and cannot be directly used as fuel. Therefore, denitrification of natural gas is an important condition for making full use of natural gas. The natural gas denitrification processes currently used in industry include: cryogenic cooling, solvent absorption, pressure swing adsorption and selective adsorption. The solvent absorption method has mild denitrification operation conditions, does not need to remove carbon dioxide, and has large operation flexibility and good application prospect because most of equipment and pipelines are made of carbon steel.
In the prior denitrification process of natural gas by a solvent absorption method, a raw material gas firstly flows through a propane refrigeration system to be cooled and then enters the lower part of a solvent absorption tower. The raw material gas is diffused from bottom to top in the solvent absorption tower and is subjected to gas-liquid mass transfer with the absorption solvent descending from the top of the tower, so that hydrocarbon components mainly comprising methane are selectively absorbed and enter a liquid phase. When the raw gas leaves the top of the column, it becomes a nitrogen stream with very little hydrocarbon content. And the solvent discharged from the bottom of the absorption tower is subjected to multistage flash evaporation to gradually reduce the pressure of the hydrocarbon-rich solvent. The flash gas discharged from the multi-stage flash tank is subjected to compression, heat exchange and propane refrigeration, and a small amount of solvent carried in the flash gas is separated out and then is sent out of a boundary zone as a product, or a selective filter is further arranged at the outlet of part of the flash tank on the basis of multi-stage flash equipment, so that the product gas which is little affected by the fluctuation of the components of the raw material gas and stable in components is provided, the raw material gas can be fully separated, and the production loss is low. The regenerated solvent is discharged from the steaming tank, and is returned to the top of the absorption tower for recycling after being pressurized and cooled, so that the cost is favorably controlled.
However, since the flash evaporation is realized by that after high-pressure saturated liquid enters a low-pressure container, a part of gas in the saturated liquid is evaporated into gas due to sudden pressure reduction, and therefore, the pressure control of the container directly influences the flash evaporation product. However, the connection relationship of the pressure vessels of the multistage flash process is complex, and the automatic control in the chemical engineering often has hysteresis and uncertainty, so that the pressure of the flash process is difficult to realize accurate control, and further the pressure fluctuation of the flash tank causes the instability of the flash process product.
Document CN110997879A discloses a solvent absorption process for separating components of an impure feed gas, hydrogen sulphide, carbon dioxide and other sulphur compounds in the gas being simultaneously removed from the feed gas by a physical solvent. The process provides a method for removing acid gases from hydrocarbons with reduced amounts of solvent, reducing the cost and expense of removing acid gases from feed gases. However, this method does not perform real-time feedback control of the flash tank pressure, and thus the flash tank pressure is liable to fluctuate, which leads to instability in terms of the quality or quantity of the flash product.
According to the GA-based flash tank pressure fuzzy adaptive PID control method, aiming at the problems of nonlinearity, hysteresis and the like of flash tank pressure control in hydrocracking, a quantization factor and a scale factor of a fuzzy controller are optimized by using a genetic algorithm, so that the adaptive adjustment of parameters of a fuzzy PID controller is realized, the adaptive capacity and robustness of adiabatic flash tank pressure control are improved by the optimized fuzzy adaptive PID controller, the dynamic characteristic and static performance of a system are improved, and the control effect on nonlinearity and time hysteresis is better. However, the pressure in the flash tank is controlled only by controlling the gas valve, the flow of the input liquid is not correspondingly controlled, and the influence of the connection relationship among the multi-stage flash tanks on the aspects of pressure control, flow control and the like is not considered, so that the effect in a flash system consisting of the multi-stage flash tanks is still examined.
Therefore, it is required to provide an optimization control system and a parameter optimization method for a natural gas solvent absorption denitrification flash process, so as to realize parameter optimization of a multi-stage flash subsystem, and thus quickly and accurately control flash pressure in a flash tank pipe in the multi-stage flash subsystem.
Disclosure of Invention
The invention provides a natural gas solvent absorption denitrification flash control system and a parameter optimization method aiming at the problems in the prior art. The technical scheme adopted by the invention is as follows:
a natural gas aerosol absorption denitrification flash control system comprising:
flash distillation system, including solvent absorption tower, multistage flash distillation subsystem, its characterized in that: each stage of the multistage flash evaporation subsystem comprises a flash evaporation tank, a liquid level detection device, a liquid flow control valve, a gas pressure measurement device and a flowmeter, wherein the liquid level detection device is arranged at the lower side in the flash evaporation tank, the liquid flow control valve is arranged on a solvent outlet pipeline at the bottom of the flash evaporation tank, the gas pressure measurement device is arranged on the flash evaporation tank, the flowmeter is arranged on a pipeline where a steam outlet of the flash evaporation tank is located, the multistage flash evaporation subsystem further comprises a sampling cavity provided with the gas pressure measurement device, a solvent outlet of the solvent absorption tower is connected with the sampling cavity through a pipeline, the sampling cavity is connected with a solvent inlet of a first-stage flash evaporation system in the multistage flash evaporation subsystem through a pipeline, and the flash evaporation tanks of the multistage flash evaporation subsystem are sequentially connected through pipelines; and at least one processor configured to control flow based on the flash system operating conditions, the flash system operating conditions being monitored by the liquid level detection device, the gas pressure measurement device, the flow meter.
Further, the at least one processor controls a solvent outlet flow of the flash system, the solvent outlet corresponding to a solvent outlet of the flash tank in each stage of the multi-stage flash subsystem.
Further, the at least one processor controls solvent outlet flow through the liquid flow control valve.
Preferably, the at least one processor calculates the adjustment value of the flow control valve from the monitored values of the liquid level detection device, the gas pressure measurement device and the flow meter.
Preferably, the flow rate is controlled by the original state of the flow rate control valve and the adjustment value of the flow rate control valve.
The invention also discloses a natural gas solvent absorption denitrification flash evaporation control parameter optimization method, which is characterized by comprising the following steps of:
firstly, setting a flash tank gas pressure control target value of each stage of flash system in a multi-stage flash subsystem;
secondly, determining an initial setting value of a liquid flow control valve according to a flash tank gas pressure control target value;
step three, collecting the measurement data of the gas pressure measuring device, the liquid flow control valve and the gas flow control valve in real time;
and fourthly, determining an adjusting value calculation method of the liquid flow control valve according to the gas pressure value in a period of time, and calculating the adjusting value of the liquid flow control valve based on the measured data.
Further, the fourth step determines an adjustment value calculation method of the liquid flow control valve by judging whether the gas pressure values in a period of time are all greater than a threshold value.
Further, if the judgment result is yes, the compensated adjustment value of the liquid flow control valve is calculated.
Further, if the judgment result is negative, the uncompensated adjustment value of the liquid flow control valve is calculated.
Preferably, the third step acquires the measurement data of the gas pressure measuring device, the liquid flow control valve and the flow meter in real time according to a fixed acquisition frequency f.
Preferably, f is 1000-.
Further, the fourth step takes the data measured by the gas pressure measuring device collected in a plurality of consecutive cycles as the gas pressure value.
Preferably, the flash system comprises a 4-stage flash system.
Preferably, the gas pressure control target values of the first-stage flash tank, the second-stage flash tank, the third-stage flash tank and the fourth-stage flash tank are respectively 2.7MPa, 1.8MPa, 0.9MPa and 0.14 MPa.
Compared with the prior art, the invention has the following beneficial effects:
the natural gas solvent absorption denitrification flash evaporation control system and the parameter optimization method provided by the invention can control the flow of the multistage flash evaporation subsystem through the control system, thereby accurately controlling the pressure in each stage of flash evaporation tank, and quickly and accurately controlling and adjusting flash evaporation process parameters through the flash evaporation control parameter optimization method.
Drawings
FIG. 1 is a schematic diagram of a flash evaporation control system for absorption denitrification of natural gas solvent according to the present invention.
FIG. 2 is a flow chart of a method for optimizing flash evaporation control parameters of natural gas solvent absorption denitrification according to the invention.
In the figure: 1 is a flash system, 2 is a processor, 3 is a solvent absorption tower, 4 is a multi-stage flash subsystem, 5 is a first-stage flash tank, 6 is a second-stage flash tank, 7 is a third-stage flash tank, 8 is a fourth-stage flash tank, 9 is a first-stage flash tank liquid level detection device, 10 is a second-stage flash tank liquid level detection device, 11 is a third-stage flash tank liquid level detection device, 12 is a fourth-stage flash tank liquid level detection device, 13 is a first-stage flash tank liquid flow control valve, 14 is a second-stage flash tank liquid flow control valve, 15 is a third-stage flash tank liquid flow control valve, 16 is a fourth-stage flash tank liquid flow control valve, 17 is a first-stage flash tank gas pressure measurement device, 18 is a second-stage flash tank gas pressure measurement device, 19 is a third-stage flash tank gas pressure measurement device, 20 is a fourth-stage flash tank gas pressure measurement device, 21 is a first-stage flash tank flow meter, and 22 is a second-stage flash tank flow meter, reference numeral 23 denotes a three-stage flash tank flow meter, 24 denotes a four-stage flash tank flow meter, 25 denotes a sampling chamber, 26 denotes a sampling chamber gas pressure detection device, 27 denotes a CH4 priority filter, 28 denotes a first N2 filter, 29 denotes a second N2 filter, 30 denotes a lean CH4 flow meter, 31 denotes a main pipe outlet control valve, 32 denotes a first valve, 32 denotes a second valve, S1 denotes a first step, S2 denotes a second step, S3 denotes a third step, and S4 denotes a fourth step.
Detailed Description
The present invention will now be described in more detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown, it being understood that one skilled in the art may modify the invention herein described while still achieving the beneficial results of the present invention. Accordingly, the following description should be construed as broadly as possible to those skilled in the art and not as limiting the invention. Moreover, it is to be noted that the drawings are in a very simplified form and that non-precise ratios are employed for the sole purpose of facilitating and distinctly claiming the embodiments of the present invention.
In the interest of clarity, not all features of an actual implementation are described. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific details must be set forth in order to achieve the developer's specific goals.
For convenience of explanation, the natural gas solvent absorption denitrification flash evaporation control system and the parameter optimization method corresponding to the four-stage flash evaporation system are only illustrated. However, in practice, the number of flash stages included in the multi-stage flash subsystem may be more or less. In order to facilitate understanding of the technical scheme of the application, firstly, the optimal control system of the natural gas solvent absorption denitrification flash evaporation process provided by the invention is introduced.
As shown in fig. 1, a flash evaporation control system for absorption denitrification of natural gas solvent comprises a flash evaporation system 1 and a processor 2, wherein the flash evaporation system 1 is connected with the processor 2, and the connection can be performed through a wired or wireless network, such as: data transmission lines, WIFI, or ZIGBEE networks. The flash system 1 comprises a solvent absorption tower 3 and a multi-stage flash subsystem 4.
In the multistage flash subsystem 4, a primary flash system comprises a primary flash tank 5 and a CH4 priority filter 27, wherein a solvent inlet of the primary flash tank 5 is used for flowing in the hydrocarbon-rich solvent discharged from the solvent absorption tower 3, a solvent outlet is used for discharging the solvent subjected to primary flash processing from the primary flash tank 5, and a vapor outlet is connected with an inflow end of the CH4 priority filter 27 through a pipeline; the secondary flash system comprises a secondary flash tank 6, a first N2 priority filter 28, the solvent inlet of the secondary flash tank 6 is connected by a pipe to the solvent outlet of the primary flash tank 5, the solvent outlet discharges the solvent to the lower stage flash vessel, the vapor outlet is connected by a pipe to the gas inflow end of the first N2 priority filter 28; the three-stage flash system comprises a three-stage flash tank 7, a second N2 priority filter 29, a solvent inlet of the three-stage flash tank 7 is connected to a solvent outlet of the second-stage flash tank 6 through a pipeline, the solvent outlet discharges the solvent to a lower-stage flash vessel, a vapor outlet is connected to a gas inflow end of the second N2 priority filter 29 through a pipeline; the four-stage flash system comprises a four-stage flash drum 8, the solvent inlet of the four-stage flash drum 8 being connected by a conduit to the solvent outlet of the three-stage flash drum 7, the solvent outlet being connected to a respective booster pump and evaporator and circulating solvent into the solvent absorption column 3, the vapour outlet being connected to the product gas delivery conduit in common with the N2 lean gas outflow of the second N2 priority filter 29. A first-level flash tank liquid level detection device 9, a second-level flash tank liquid level detection device 10, a third-level flash tank liquid level detection device 11 and a fourth-level flash tank liquid level detection device 12 are respectively arranged at the lower sides of the interiors of the first-level flash tank 5, the second-level flash tank 6, the third-level flash tank 7 and the fourth-level flash tank 8, a first-level flash tank liquid flow control valve 13, a second-level flash tank liquid flow control valve 14, a third-level flash tank liquid flow control valve 15 and a fourth-level flash tank liquid flow control valve 16 are arranged on pipelines of solvent outlets at the bottoms of the first-level flash tank 5, the second-level flash tank 6, the third-level flash tank 7 and the fourth-level flash tank 8, a first-level flash tank gas pressure measurement device 17, a second-level flash tank gas pressure measurement device 18, a third-level flash tank gas pressure measurement device 19 and a fourth-level flash tank gas pressure measurement device 20 are respectively arranged on the first-level flash tank 5, the second-level flash tank 6, the third-level flash tank 7 and the fourth-level flash tank 8, install one-level flash tank flowmeter 21, second grade flash tank flowmeter 22, tertiary flash tank flowmeter 23, level four flash tank flowmeter 24 on the pipeline at the vapor outlet place of one-level flash tank 5, second grade flash tank 6, tertiary flash tank 7 and level four flash tank 8 the solvent of solvent absorption tower 3 exports to set up sampling chamber 25 on the pipeline between the solvent entry of one-level flash tank 5, on being close to the position of one-level flash tank, sampling chamber gas pressure detection device 26 is installed to sampling chamber 25. The outflow end of the CH4 preferential filter 27 CH4 is connected to the circulating gas flow inlet of the solvent absorption tower 3 as a circulating gas flow outlet. The CH4 priority filter 27 has a CH 4-lean gas outflow end connected to a branch pipe via a CH 4-lean flow meter 30, a main pipe inlet connected to the outflow end of the CH 4-lean flow meter 30, and a main pipe outlet connected to a first branch pipe and a second branch pipe, the first branch pipe and the second branch pipe being respectively provided with a first valve 32 and a second valve 33 for controlling opening and closing, the second branch pipe being connected to the gas inflow end of the first N2 priority filter 28 via the second valve 33, and the N2 outflow end of the first N2 priority filter 28 being connected to a discharge device for discharging the vapor rich in N2; the first branch line is connected to an N2 gas discharge line via the first valve 32, the N2-lean gas outflow end of the first N2 priority filter 28 is connected to the gas inflow end of the second N2 priority filter 29, and the N2-lean gas outflow end of the second N2 priority filter 29 outputs CH 4-rich gas.
Liquid level detection devices such as the first-stage flash tank liquid level detection device 9, the second-stage flash tank liquid level detection device 10, the third-stage flash tank liquid level detection device 11, the fourth-stage flash tank liquid level detection device 12, liquid flow control valves such as the first-stage flash tank liquid flow control valve 13, the second-stage flash tank liquid flow control valve 14, the third-stage flash tank liquid flow control valve 15, the fourth-stage flash tank liquid flow control valve 16, gas pressure measurement devices such as the first-stage flash tank gas pressure measurement device 17, the second-stage flash tank gas pressure measurement device 18, the third-stage flash tank gas pressure measurement device 19, the fourth-stage flash tank gas pressure measurement device 20, the sampling cavity gas pressure detection device 26, flow meters such as the first-stage flash tank flow meter 21, the second-stage flash tank flow meter 22, the third-stage flash tank flow meter 23, the fourth-stage flash tank flow meter 24 and the like, the flash evaporation system is connected to a processor 2, a plurality of liquid level detection devices, a gas pressure measuring device, a liquid flow control valve and a flow meter transmit measuring data to the processor 2, and the processor 2 performs calculation and judgment according to the measuring data to perform flow control on the flash evaporation system.
The processor 2 controls the flow of the solvent outlet through the liquid flow control valves such as the first-stage flash tank liquid flow control valve 13, the second-stage flash tank liquid flow control valve 14, the third-stage flash tank liquid flow control valve 15, and the fourth-stage flash tank liquid flow control valve 16, so as to control the flow of the solvent flowing out of the corresponding flash tank.
The processor 2 controls the adjustment amplitude of the flow control valve by calculating the adjustment value of the flow control valve.
The processor 2 adjusts the state of the flow control valve by the original state of the flow control valve and the adjustment value of the flow control valve, thereby realizing flow control.
As shown in fig. 2, a method for optimizing flash evaporation control parameters of natural gas solvent absorption denitrification comprises the following steps:
first step S1: determining control target values P of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 8t1、Pt2、Pt3、Pt4。
The control target value P can be adjusted according to the process settingt1、Pt2、Pt3、Pt4Set to 2.7MPa, 1.8MPa, 0.9MPa and 0.14MPa, respectively. The control target value P is input in a preset or manual modet1、Pt2、Pt3、Pt4Is input into the processor 2, the processor 2 converts Pt1、Pt2、Pt3、Pt4And the control target values of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 8 participate in subsequent parameter calculation.
Second step S2: according to the control target value Pt1、Pt2、Pt3、Pt4Determining initial setting values vl of the primary flash tank liquid flow control valve 13, the secondary flash tank liquid flow control valve 14, the tertiary flash tank liquid flow control valve 15 and the quaternary flash tank liquid flow control valve 1610、vl20、vl30、vl40。
Specifically, according to equations 1-4, the initial setting value vl of the liquid flow control valve is determined10、vl20、vl30、vl40. Formulas 1-4 are as follows:
wherein p is atmospheric pressure (MPa), p1t、p2t、p3t、p4tControl target values (MPa), vl, of the primary flash tank 5, the secondary flash tank 6, the tertiary flash tank 7 and the quaternary flash tank 810、vl20、vl30、vl40Initial liquid flow (L/s), vg) of the tubes in which the solvent outlets of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 8 are located10、vg20、vg30、vg40Is the default gas flow (L/s) of the pipeline in which the gas outlets of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 8 are positioned, Q is the energy (J) required to be absorbed by one mole of gas to evaporate, R is the gas constant, T is the gas temperature (K), d is1、d2、d3、d4The internal diameters (m), H of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 81、H2、H3、H4The internal heights, l, of the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7 and the fourth-stage flash tank 800、l10、l20、l30、l40The initial liquid heights (m) of the solvent absorption column 3, the first-stage flash tank 5, the second-stage flash tank 6, the third-stage flash tank 7, and the fourth-stage flash tank 8, and k is the number of stages of the corresponding flash tanks. Said p iskt，vgk0T is a predetermined value, dk、HkIs the k-th stageDesign size of the flash tank, saidk0The initial values for the plurality of level detection devices in the initial state, Q, R, are well known physical constants that one skilled in the art would look up from material composition.
Third step S3: the data of the primary flash tank liquid level detection device 9, the secondary flash tank liquid level detection device 10, the tertiary flash tank liquid level detection device 11 and the quaternary flash tank liquid level detection device 12 are acquired in real time as l1i、l2i、l3i、l4iThe data of the gas pressure detection device 26 of the sampling cavity, the gas pressure measuring device 17 of the primary flash tank, the gas pressure measuring device 18 of the secondary flash tank, the gas pressure measuring device 19 of the tertiary flash tank and the gas pressure measuring device 20 of the quaternary flash tank is collected to be p0i、p1i、p2i、p3i、p4iControl values vg of the cycle of the first-stage flash tank flowmeter 21, the second-stage flash tank flowmeter 22, the third-stage flash tank flowmeter 23, and the fourth-stage flash tank flowmeter 241i、vg2i、vg3i、vg4iWherein i is the collection frequency.
Specifically, data is acquired at a fixed acquisition frequency f.
Preferably, f is 1000-.
Fourth step S4: and determining the adjustment values of the primary flash tank liquid flow control valve 13, the secondary flash tank liquid flow control valve 14, the tertiary flash tank liquid flow control valve 15 and the quaternary flash tank liquid flow control valve 16 according to the gas pressure value in a period of time.
In particular, by measuring p in real time0iAnd recording the measured data over a period of time, i.e. p for n consecutive periods0i-n+1、p0i-n+2、……、p0iWherein n ranges from 10 to 20. Judging the detected p of continuous n periods0Whether the data are all greater than the threshold. The threshold is calculated by equation 5:
wherein p is0thIs p0A judgment threshold value of d0P is the atmospheric pressure (MPa), Q is the energy (J) to be absorbed for one mole of gas to evaporate, and R is the gas constant, which is the internal diameter of the solvent absorption column 3. Q, R are well known physical constants that one skilled in the art would obtain from a material composition query.
If the judgment result is yes, p is0i-n+1、p0i-n+2、……、p0iAre all greater than a threshold value p0thIndicating that the solvent entering the flash system is evaporated with liquid and therefore needs to be compensated for subsequent control adjustments. Calculating the adjustment values delta vl of the liquid flow control valve 13 of the primary flash tank, the liquid flow control valve 14 of the secondary flash tank, the liquid flow control valve 15 of the tertiary flash tank and the liquid flow control valve 16 of the quaternary flash tank by the formula 61、Δvl2、Δvl3、Δvl4。
Wherein, Δ pki＝pki-pktK is the number of flash tank stages, k-1 is the solvent absorption tower stage, i is the number of acquisitions, pkiIs the pressure value, p, collected by the gas pressure measuring device of the kth flash tank at the ith timektIs a pressure control target value of a k-th flash tank, delta p0iThe pressure value and the threshold value p acquired by the sampling cavity gas pressure detection device 26 at the ith time0thDifference of (a) v lkiIs the adjustment value of the liquid flow control valve of the kth flash tank at the ith acquisition, delta vgkiThe value and the preset value vg obtained by the ith acquisition of the flowmeter of the kth-stage flash tankk0Difference of (p)0iIs the pressure value, p, collected by the sampling cavity gas pressure detection device 26 at the ith time1iThe pressure value, Δ vl, obtained at the i-th acquisition of the gas pressure measuring device 17 of the primary flash tankk-1iQ, R is a well-known physical constant for adjustment value of the ith collection of the k-1 st-stage solvent absorption tower, and is inquired by the person skilled in the art according to the composition of the substanceT is obtained as a preset value. Through the adjustment and compensation, the influence of the evaporation with liquid on the control of subsequent parameters is compensated.
If the judgment result is negative, p is0i-n+1，p0i-n+2，……，p0iAre not all greater than the threshold p0thCalculating the adjustment values delta vl of the liquid flow control valve 13 of the primary flash tank, the liquid flow control valve 14 of the secondary flash tank, the liquid flow control valve 15 of the tertiary flash tank and the liquid flow control valve 16 of the quaternary flash tank according to the formula 71、Δvl2、Δvl3、Δvl4。
Wherein, Δ pki＝pki-pktK is the number of flash tank stages, k-1 is the solvent absorption tower stage, i is the number of acquisitions, pkiIs the pressure value, p, collected by the gas pressure measuring device of the kth flash tank at the ith timektIs a pressure control target value of a k-th flash tank, delta p0iThe pressure value and the threshold value p acquired by the sampling cavity gas pressure detection device 26 at the ith time0thDifference of (a) v lkiIs the adjustment value of the liquid flow control valve of the kth flash tank at the ith acquisition, delta vgkiThe value and the preset value vg obtained by the ith acquisition of the flowmeter of the kth-stage flash tankk0Difference of (a) v lk-1iQ, R is a known physical constant which is obtained by inquiring according to the composition of the substance by a person skilled in the art, and T is a preset value.
By calculating the adjustment value Δ vl1、Δvl2、Δvl3、Δvl4The size of the natural gas solvent is optimized by parameters of the natural gas solvent absorption denitrification flash control system. Subsequently, the adjustment values Δ vl are respectively adjusted1、Δvl2、Δvl3、Δvl4Control value vl corresponding to the current1i、vl2i、vl3i、vl4iAdding to obtain the control value vl of the next adjustment period1i+1、vl2i+1、vl3i+1、vl4i+1And applying said control value vl1i+1、vl2i+1、vl3i+1、vl4i+1And the natural gas solvent is respectively fed back to a primary flash tank liquid flow control valve 13, a secondary flash tank liquid flow control valve 14, a tertiary flash tank liquid flow control valve 15 and a quaternary flash tank liquid flow control valve 16, so that the control effect of the natural gas solvent absorption denitrification flash control system is optimized.
The natural gas solvent absorption denitrification flash control system provided by the invention controls the flow of the flash system through a plurality of liquid level detection devices, a gas pressure measurement device, a liquid flow control valve, a flow meter and a processor; the method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification can accurately calculate the control parameters of the flow control valve according to the current state, so that the control parameters are optimized; the automatic control of the parameters is realized through the provided natural gas solvent absorption denitrification flash evaporation control system and the parameter optimization method, and the accuracy of the automatic control of the natural gas solvent absorption denitrification flash evaporation process is improved.
In order to highlight the invention point in the description, some known necessary communication or pipeline pressure control components, such as network connectors and pumps, valves, etc., are omitted in describing the equipment system, but the arrangement positions and ways of the above necessary components can be determined by those skilled in the art according to the technical knowledge in the grasp of the components to implement the invention, and therefore, the detailed description is omitted.
The foregoing shows and describes the general principles, essential features and advantages of the invention, which is, therefore, described only as an example of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but rather that the invention includes various equivalent changes and modifications without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (14)
1. A natural gas aerosol absorption denitrification flash control system comprising:
flash system, including solvent absorption tower, multistage flash distillation subsystem, its characterized in that: each stage of the multistage flash evaporation subsystem comprises a flash evaporation tank, a liquid level detection device, a liquid flow control valve, a gas pressure measurement device and a flowmeter, wherein the liquid level detection device is arranged at the lower side in the flash evaporation tank, the liquid flow control valve is arranged on a solvent outlet pipeline at the bottom of the flash evaporation tank, the gas pressure measurement device is arranged on the flash evaporation tank, the flowmeter is arranged on a pipeline where a steam outlet of the flash evaporation tank is positioned, the multistage flash evaporation subsystem further comprises a sampling cavity provided with the gas pressure measurement device, a solvent outlet of the solvent absorption tower is connected with the sampling cavity through a pipeline, the sampling cavity is connected with a solvent inlet of a first-stage flash evaporation system in the multistage flash evaporation subsystem through a pipeline, and the multistage flash evaporation subsystems are sequentially connected through pipelines; and
at least one processor configured to control flow based on an operating state of the flash system, the flash system operating state being monitored by the liquid level detection device, gas pressure measurement device, flow meter.
2. A natural gas aerosol absorption denitrification flash control system as set forth in claim 1, wherein: the at least one processor controls a solvent outlet flow of the flash system, the solvent outlet corresponding to a solvent outlet of the flash tank in each stage of the multi-stage flash subsystem.
3. A natural gas aerosol absorption denitrification flash control system as set forth in claim 1, wherein: the at least one processor controls solvent outlet flow through the liquid flow control valve.
4. A natural gas aerosol absorption denitrification flash control system as set forth in claim 1, wherein: and the at least one processor calculates the adjustment value of the flow control valve through the monitoring values of the liquid level detection device, the gas pressure measurement device and the flow meter.
5. A natural gas aerosol absorption denitrification flash control system as set forth in claim 4, wherein: and controlling the flow according to the original state of the flow control valve and the adjustment value of the flow control valve.
6. A natural gas solvent absorption denitrification flash evaporation control parameter optimization method is characterized by comprising the following steps:
firstly, setting a flash tank gas pressure control target value of each stage of flash system in a multi-stage flash subsystem;
secondly, determining an initial setting value of a liquid flow control valve according to a flash tank gas pressure control target value;
step three, collecting the measurement data of the gas pressure measuring device, the liquid flow control valve and the gas flow control valve in real time;
and fourthly, determining an adjusting value calculation method of the liquid flow control valve according to the gas pressure value in a period of time, and calculating the adjusting value of the liquid flow control valve based on the measured data.
7. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 6, wherein the method comprises the following steps: and the fourth step is to determine the adjustment value calculation method of the liquid flow control valve by judging whether the gas pressure values in a period of time are all larger than a threshold value.
8. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 7, wherein the method comprises the following steps: and when the judgment result is yes, calculating the compensated adjustment value of the liquid flow control valve.
9. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 7, wherein the method comprises the following steps: and if not, calculating the adjustment value of the liquid flow control valve without compensation.
10. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 6, wherein the method comprises the following steps: and the third step of acquiring the measurement data of the gas pressure measuring device, the liquid flow control valve and the flowmeter in real time according to the fixed acquisition frequency f.
11. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 10, wherein the method comprises the following steps: the fixed acquisition frequency f is 1000-5000 Hz.
12. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 6, wherein the method comprises the following steps: and the fourth step takes the data measured by the gas pressure measuring device collected in a plurality of continuous periods as the gas pressure numerical value.
13. The method for optimizing the flash evaporation control parameters of the natural gas solvent absorption denitrification according to claim 6, wherein the method comprises the following steps: the multi-stage flash subsystem comprises a 4-stage flash system.
14. The method for optimizing the flash evaporation control parameters for absorption denitrification of natural gas solvents according to claim 13, wherein the method comprises the following steps: the gas pressure control target values of the first-stage flash tank, the second-stage flash tank, the third-stage flash tank and the fourth-stage flash tank are respectively 2.7MPa, 1.8MPa, 0.9MPa and 0.14 MPa.
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