CN113582813A - Method for dewatering and desalting ethylene glycol regeneration system of offshore gas field - Google Patents
Method for dewatering and desalting ethylene glycol regeneration system of offshore gas field Download PDFInfo
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Abstract
The invention relates to a method for dehydrating and desalting an ethylene glycol regeneration system of an offshore gas field. The method comprises the following steps: feeding the pretreated saliferous glycol-rich solution into a rectifying tower with a lateral line; in the rectifying tower, water vapor is condensed from the top of the rectifying tower through a condenser and enters a reflux tank, part of condensate in the reflux tank flows back into the rectifying tower, and part of condensate is discharged through a production water delivery pump; supersaturated glycol generated in the tower kettle of the rectifying tower is conveyed to a centrifuge for solid-liquid separation through a saturated glycol conveying pump, solid salt is collected and treated, and the glycol after centrifugal separation is heated by a circulating heater and returns to the tower kettle of the rectifying tower; and (4) extracting the qualified lean glycol product from the lower part of the rectifying tower. The invention realizes the simultaneous dehydration and desalination by only using one rectifying tower, thereby not only inhibiting the occurrence of scaling and corrosion to the maximum extent, but also reducing the occupied area and the equipment cost.
Description
Technical Field
The invention belongs to the field of separation and purification, and the dehydration and desalination of ethylene glycol are completed by a rectifying tower with side line extraction.
Background
In the process of deepwater gas field exploitation, as petroleum and natural gas are exploited to enter deeper water areas and higher-pressure operation environments, hydrate risks are aggravated, and the safe transportation of oil and gas is seriously threatened. (AlHarooni, K.; Gubner, R.; Iglauer, S.; Pack, D.; Barifcani, A.Influent of Regenerated monomer on Natural Gas Hydrate formation. energy & Fuels 2017,31(11),12914-12931.) to prevent the formation of Natural Gas hydrates, ethylene Glycol (MEG) is typically injected at the wellhead. (Al Helal, A.; Soames, A.; Gubner, R.; Iglauer, S.; Barifcani, A. Performance of erythrobic acids as an oxygenen scavenger in thermal ly induced lean MEG. journal of Petroleum Science and Engineering 2018,170, 911-. Wherein the salt is mainly sodium chloride. If untreated, reinjection will cause the glycol mass fraction to fail or the deposition of salts and other contaminants to compromise the entire underwater system. Therefore, the ethylene glycol must be recovered and regenerated to remove water, salt, hydrocarbons and carbon dioxide from the rich MEG, so that the ethylene glycol product meets the requirements of concentration, salt content and the like, and is conveyed back to a water injection point for recycling, thereby reducing the operation cost and the corrosion of equipment and pipelines.
At present, three methods, namely a traditional regeneration method, a complete regeneration method and a split-flow regeneration method, are mainly used for recovering and regenerating ethylene glycol. (Teixeira, a.m.; Arinelli, l.d.o.; mediros, j.l.d.; Ara jo, o.d.q.f. excess Analysis of monomeric glycol recovery processes for hydrate inhibition in offset Natural Gas fields. journal of Natural Gas Science and Engineering 2016,35, 798-: the rich ethylene glycol is subjected to dealkylation and dehydration treatment, so that the rich solution is regenerated into lean solution, and the lean solution is reinjected into the pipeline. The complete regeneration method comprises the following steps: and (3) the pretreated ethylene glycol-rich liquid enters a flash separator, the water content of the ethylene glycol-rich liquid is evaporated and then enters a distillation tower to generate ethylene glycol barren solution, and the salt and the non-volatile impurities are concentrated in the flash separator and removed by a decanter centrifuge. The flow of the shunting desalting method comprises the following steps: the pretreated glycol rich solution enters a regeneration tower for dehydration, a part of the produced glycol barren solution enters a flash separator for desalination, glycol is heated and gasified in the flash separator and then enters a condenser for condensation, the condensed glycol is mixed with the glycol barren solution which is not subjected to desalination before to obtain regenerated glycol barren solution, and impurities such as high-dissolved salt at the bottom of the flash separator are conveyed to a centrifuge for removal. (handstand, zhangchung, lianyu, yang zhuangchun, spaying, sun xu, high strength, country rock. ethylene glycol recovery and desalination technology in the project of wine [ A ]. editions of Chinese shipbuilding institute of engineering, edition of China, ocean engineering talk [ C ]: Chinese shipbuilding institute of engineering, 2014:8.)
For the traditional regeneration method, the flow is simple, the operation cost is low, but the desalting treatment is not carried out, a large amount of salt is deposited in the later operation period to cause scaling and serious corrosion of equipment, and the method is not suitable for long-term stable operation; the complete regeneration method and the shunt regeneration method introduce a desalting unit, which can effectively inhibit the occurrence of scaling and corrosion, but the desalting and the dewatering are carried out by two unit operations, the occupied area of equipment is large, and the running cost is high. Since the MRU is generally built on an offshore platform, the area of the offshore platform is limited. Therefore, how to effectively prevent corrosion and scale formation, reduce the operation cost and reduce the occupied area becomes an important difficult problem to be solved urgently in the prior glycol dehydration and desalination.
Disclosure of Invention
The invention aims to effectively prevent corrosion and scale formation, reduce operation cost and reduce occupied area, and provides a method for dewatering and desalting an offshore gas field glycol regeneration system. The method adopts the rectifying tower with side extraction for dehydration and desalination, realizes simultaneous dehydration and desalination by only one rectifying tower, can inhibit scaling and corrosion to the maximum extent, and also reduces the occupied area and the equipment cost.
In order to achieve the aim, the technical scheme of the invention is as follows:
a method for de-watering and desalting an offshore gas field ethylene glycol regeneration system, the method comprising the steps of:
feeding the pretreated saliferous glycol-rich solution into a rectifying tower with a lateral line; in the rectifying tower, water vapor is condensed from the top of the rectifying tower through a condenser and enters a reflux tank, part of condensate in the reflux tank flows back into the rectifying tower, and part of condensate is discharged through a production water delivery pump; supersaturated glycol generated in the tower kettle of the rectifying tower is conveyed to a centrifuge for solid-liquid separation through a saturated glycol conveying pump, solid salt is collected and treated, and the glycol after centrifugal separation is heated by a circulating heater and returns to the tower kettle of the rectifying tower; qualified lean glycol products enter a qualified lean glycol conveying pipeline through a qualified lean glycol conveying pump at the lower part of the rectifying tower;
the rectifying tower is provided with a side draw outlet, the number of the plates is between 10 and 13, the position of the feed plate is between 7 and 10 plates, and the position of the side draw is between 9 and 12 plates.
The reflux ratio of the rectifying tower is 0.05-0.1, the mass ratio of the side extraction amount to the feeding amount is 0.3-0.8: 1.
the operating pressure of the rectifying tower is controlled to be 10-30kPaA, the tower top temperature is controlled to be 40-70 ℃, the side line extraction point temperature is controlled to be 80-120 ℃, and the tower kettle temperature is controlled to be 140-160 ℃.
The water content of the pretreated ethylene glycol-rich solution containing salt is within the range of 30 wt% -70 wt%, and the salt content of the pretreated ethylene glycol-rich solution is within the range of 1 wt% -5 wt%. The ethylene glycol content ranges from 27% to 67% by weight.
The condenser is a coil pipe type condenser, and the condensing medium is seawater.
A system for offshore gas field ethylene glycol regeneration, the system comprising: the top of the rectifying tower is connected with the inlet of a reflux tank through a condenser, and the discharge port of the reflux tank is also connected with a production water delivery pump and the top of the rectifying tower through pipelines respectively; a side draw outlet of the rectifying tower is connected with a qualified lean glycol delivery pump; the tower kettle of the rectifying tower is connected with a supersaturated glycol delivery pump, the supersaturated glycol delivery pump is also connected with a centrifugal machine, and the centrifugal machine is also connected with the tower kettle of the rectifying tower; the vacuum pump is connected with the reflux tank; the condenser is connected with a seawater pipeline;
the conveying pipeline of the salt-containing glycol-rich solution is connected with the feed inlet of the rectifying tower; the production water delivery pump is also connected with a delivery pipeline of the production water; the qualified lean glycol delivery pump is also connected with a delivery pipeline of the qualified lean glycol.
The invention relates to a method for dehydrating and desalting an ethylene glycol regeneration system of an offshore gas field, which has the design principle that: the desalination and dehydration adopt a negative pressure rectifying tower with a lateral line, and utilize the phase change characteristics of glycol solutions with different concentrations under different pressure and temperature conditions; the high-concentration supersaturated glycol solution is still in a liquid phase under specific pressure and temperature, after heat transfer with the glycol rich solution, water with low boiling point flows out from the top of the tower, the glycol solution with the concentration up to the standard flows out from the lateral line, and the supersaturated glycol concentrated solution is subjected to solid-liquid separation by adopting a centrifuge; the negative pressure rectification is adopted, so that the energy consumption can be reduced and the glycol degradation can be prevented.
The invention has the beneficial effects that:
the invention realizes that the ethylene glycol dehydration and desalination operation is carried out in a rectifying tower with a side line, and compared with the traditional regeneration method which introduces desalination operation, the invention inhibits the generation of scaling and corrosion to the maximum extent; compared with a full-flow regeneration method and a split-flow regeneration method, the method does not need separate flash evaporation desalination and regeneration dehydration, has simple flow, reduces equipment cost and reduces occupied area.
Drawings
FIG. 1 is a process flow diagram of a one-step dehydration, desalination and rectification tower;
FIG. 2 is a graph of MEG content in overhead production at different sampling times for the operating pressure of 25kPaA in example 1;
FIG. 3 is a graph of the MEG content in the side-cut streams at different sampling times for the operating pressure of 25kPaA in example 1;
FIG. 4 is a plot of sodium ion content in side-cut streams at different sampling times for the operating pressure of 25kPaA in example 1;
FIG. 5 is a graph of MEG content in overhead production at different sampling times for the operating pressure of 15kPaA in example 2;
FIG. 6 is a graph of the MEG content in the side-cut streams at different sampling times for the operating pressure of 15kPaA in example 2;
FIG. 7 is a plot of sodium ion content in side-cut streams at different sampling times for the operating pressure of 15kPaA in example 2;
FIG. 8 is a graph showing the MEG content in the overhead product liquid at different sampling times in the case of feed composition water (ethylene glycol: sodium chloride) in example 3 at a mass ratio of 70:27: 3;
FIG. 9 is a graph of MEG content in side-cut streams at different sampling times for the case of feed composition water, ethylene glycol and sodium chloride (mass ratio) 70:27:3 in example 3;
FIG. 10 is a graph showing the sodium ion content in the side-cut streams at different sampling times in the case of feed composition water, ethylene glycol and sodium chloride (mass ratio) of 70:27:3 in example 3;
FIG. 11 is a graph showing the MEG content in the overhead product liquid at different sampling times in the case of feed composition water (ethylene glycol: sodium chloride) in example 4 at a mass ratio of 50:45: 5;
FIG. 12 is a graph of MEG content in side-cut streams at different sampling times for the case of feed composition water, ethylene glycol and sodium chloride (mass ratio) 50:45:5 in example 4;
FIG. 13 is a graph of the sodium ion content in the side-cut streams at different sampling times for the case of feed composition water, ethylene glycol and sodium chloride (mass ratio) of 50:45:5 in example 4;
wherein, the method comprises the following steps of 1-a rectifying tower, 2-a condenser, 3-a reflux tank, 4-a production water delivery pump, 5-a vacuum pump, 6-a qualified lean glycol delivery pump, 7-a supersaturated glycol delivery pump, 8-a centrifuge, 9-a circulating heater, 10-a salt-containing glycol solution, 11-produced water, 12-a qualified lean glycol, 13-a salt, 14-desalted glycol and 15-a seawater pipeline.
Detailed Description
To further illustrate the technical solution of the present invention, the following specific examples are given. It should be understood that the present invention has been shown and described only by way of illustration and description, and it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention or exceeding the scope of the claims.
The invention relates to a rectifying tower system with a side line for dehydrating and desalting ethylene glycol, which is shown in a figure 1: the top of the rectifying tower 1 is connected with the inlet of a reflux tank 3 through a condenser 2, and the discharge port of the reflux tank 3 is also connected with a production water delivery pump 4 and the top of the rectifying tower 1 through pipelines respectively; a side draw outlet of the rectifying tower 1 is connected with a qualified lean glycol delivery pump 6; the tower kettle of the rectifying tower 1 is connected with a supersaturated ethylene glycol delivery pump 7, the supersaturated ethylene glycol delivery pump 7 is also connected with a centrifuge 8, and the centrifuge 8 is also connected with the tower kettle of the rectifying tower 1; the vacuum pump 5 is connected with the reflux tank 3; the condenser 2 is connected with a seawater pipeline;
a conveying pipeline of the salt-containing glycol-rich solution 10 is connected with a feed inlet of the rectifying tower 1; the production water delivery pump 4 is also connected with a delivery pipeline of the production water 11; the qualified lean glycol delivery pump 6 is also connected with a delivery pipeline of qualified lean glycol 12; the centrifuge 8 also obtains solid salt 13.
The saline ethylene glycol-rich solution 10 from the upstream pretreatment enters a rectifying tower 1 with a side line; in the rectifying tower 1, water vapor is condensed from the top of the rectifying tower through a condenser 2 and enters a reflux tank 3, part of condensate in the reflux tank flows back into the rectifying tower, and part of condensate is discharged through a production water delivery pump 4; supersaturated glycol generated at the bottom of the rectifying tower 1 is conveyed to a centrifuge 8 through a supersaturated glycol conveying pump 7 for solid-liquid separation, solid salt 13 is collected and treated, and glycol 14 after centrifugal separation is heated by a circulating heater 9 and returns to the bottom of the rectifying tower 1; at the lower part of the rectifying tower 1, qualified lean glycol products 12 enter a conveying pipeline of the qualified lean glycol 12 through a qualified lean glycol conveying pump 6;
and the vacuum pump 5 is connected with the reflux tank 3 to provide negative pressure for the whole rectification system.
The rectifying tower is provided with a side draw outlet, the number of the plate is between 10 and 13, the position of the plate is between 7 and 10, and the position of the side draw is between 9 and 12.
The reflux ratio of the rectifying tower 1 is 0.05-0.1, the mass ratio of the side extraction amount to the feeding amount is 0.3-0.8: 1.
the operating pressure of the rectifying tower is controlled to be 10-30kPaA, the tower top temperature is controlled to be 40-70 ℃, the side line extraction point temperature is controlled to be 80-120 ℃, and the tower kettle temperature is controlled to be 140-160 ℃.
The pre-treated salt-containing ethylene glycol-rich solution 10 has a water content ranging from 30 wt% to 70 wt% and a salt content ranging from 1 wt% to 5 wt%. The water content ranges from 27 wt% to 67 wt%.
The pretreated salt-containing ethylene glycol-rich solution 10 is the solution in the whole MRU system after pretreatment to remove the soluble salts and hydrocarbons. The main components of the solution are ethylene glycol, water, high solubility salts and trace amounts of low solubility salts. The main salt is sodium chloride.
The condenser 3 is a coil condenser, and the condensing medium is seawater.
Example 1:
under the conditions that the feeding amount is 1L/h, the ethylene glycol in the overhead produced liquid is less than 150ppm, and the ethylene glycol in the side-draw lean ethylene glycol is (90 +/-1) wt%, the inventor finally determines that the optimal theoretical plate number is 12, the corresponding optimal reflux ratio is 0.0765, the optimal feeding position is on the 9 th plate, and the optimal side-draw position is on the 11 th plate through a large amount of experiments and analysis.
1. The number of the plates of the rectifying tower is 12, the feeding position is at the 9 th plate, the side draw position is at the 11 th plate, the reflux ratio is set to 0.0765, and the mass ratio of the side draw amount to the feeding amount is 0.53.
2. The operating pressure of the rectifying tower is 25kPaA, the tower top temperature is 64 +/-3 ℃, the side line extraction point temperature is controlled at 106 +/-3 ℃, and the tower kettle temperature is 153 +/-3 ℃.
3. The feed component water comprises ethylene glycol and sodium chloride (mass ratio) of 50:47:3, the feed amount is 1L/h, the overhead extraction amount is 0.44L/h, and the side extraction amount is 0.53L/h.
The experimental steps are as follows:
(1) checking the air tightness of the device, enabling the numerical value of the potentiometer to return to zero, and connecting circulating water;
(2) preparing a sodium chloride solution of ethylene glycol and water (ethylene glycol: water: sodium chloride: 47:50:3), adding the solution into the tower kettle of the rectifying tower until the addition is stopped at the tower kettle 1/3;
(3) starting a vacuum pump, starting the tower kettle for heating when the pressure is reduced to 25kPaA, and starting the tower body for heat tracing when the feed liquid in the tower kettle begins to boil;
(4) keeping total reflux for 30min when the temperature of the tower top and tower kettle is stable and the time begins to be timed when reflux exists, then adjusting the reflux ratio to 0.0765, and collecting H from the tower top2O; starting total reflux when the temperatures of the tower kettle and the tower top are respectively maintained at 153 +/-3 ℃ and 64 +/-3 ℃, starting feeding, adjusting the feeding flow rate to be 1L/h, and adjusting the reflux ratio to 0.0765; after the temperatures of the tower kettle, the side line and the tower top reach 153 +/-2 ℃, 106 +/-3 ℃ and 64 +/-3 ℃, extracting MEG barren solution from the side line, adjusting the heat load of the tower kettle, maintaining the temperatures of the tower kettle, the side line and the tower top at 153 +/-3 ℃, 106 +/-3 ℃ and 64 +/-3 ℃, and continuously operating for 8 hours;
(5) and (3) analyzing the MEG concentration in the top of the tower, the MEG concentration in the side-draw liquid and the sodium ion content in the side-draw liquid at the sampling frequency of 30 min/time.
(6) After the experiment is finished, starting total reflux, closing the tower kettle for heating, carrying out heat tracing on the tower body, and closing circulating water for reflux after the temperature of the tower kettle reaches 60 ℃; guiding out residual liquid in the device, cleaning for 2 times by using tap water, and cleaning for 1 time by using deionized water; and (5) finishing, settling, cleaning and cleaning the experimental site.
Analyzing the produced liquid at the top of the tower through TOC, and determining the content of MEG in the produced liquid at the top of the tower; and analyzing the side-line produced liquid by a constant moisture meter to determine the content of MEG in the side-line produced liquid, and analyzing the side-line produced liquid by a sodium ion detector to determine the content of sodium ions in the side-line produced liquid. Analyzing the solutions extracted at different time periods, wherein the content of ethylene glycol in the extracted liquid at the top of the tower fluctuates up and down, but is less than 150ppm, and the average value is 78 ppm; the ethylene glycol in the side-draw liquid is stabilized at 90 +/-1 wt%, and the average content of sodium ions is 70 ppm. As shown in fig. 2, 3 and 4.
The conclusion obtained in example 1 is that under the conditions that the composition water of the material, namely ethylene glycol and sodium chloride, is 50:47:3 (mass ratio) and the operating pressure is 25kPaA, the content of MEG in the produced liquid at the top of the tower is less than 150ppm, and the content of MEG in the produced liquid at the side line can be stabilized at 90 +/-1 wt%, so that the reinjection and the process requirements are met, the feasibility of completing the dehydration and desalination operation by using one rectifying tower is proved, the dehydration and desalination of the ethylene glycol are completed by adopting the method, a series of equipment such as a flash tank and the like are omitted, the operation flow is simple, the occupied area is reduced, and the equipment cost is reduced. Meanwhile, the average salt content in the side MEG was 70 ppm. The content is very small, the desalting effect is obvious, the desalting rate can reach more than 99 percent, and the scale formation and corrosion can be inhibited to the maximum extent.
Example 2:
conditions of the experiment
1. The number of the plates of the rectifying tower is 12, the feeding position is at the 9 th plate, the side draw position is at the 11 th plate, the reflux ratio is set to 0.0765, and the mass ratio of the side draw amount to the feeding amount is 0.53.
2. The operating pressure of the rectifying tower is 15kPaA, the temperature at the top of the tower is 54 +/-3 ℃, the temperature at the lateral line extraction point is controlled at 97 +/-3 ℃, and the temperature at the bottom of the tower is 143 +/-3 ℃.
3. The feed component water comprises ethylene glycol and sodium chloride (mass ratio) of 50:47:3, the feed amount is 1L/h, the overhead extraction amount is 0.44L/h, and the side extraction amount is 0.53L/h.
The experimental steps are as follows:
(1) checking the air tightness of the device, enabling the numerical value of the potentiometer to return to zero, and connecting circulating water;
(2) preparing a sodium chloride solution of ethylene glycol and water (ethylene glycol: water: sodium chloride: 47:50:3), adding the solution into the tower kettle of the rectifying tower until the addition is stopped at the tower kettle 1/3;
(3) starting a vacuum pump, starting the tower kettle for heating when the pressure is reduced to 15kPaA, and starting the tower body for heat tracing when the feed liquid in the tower kettle begins to boil;
(4) when the temperature of the tower top and the tower kettle is stable and the timing is started when reflux exists, the total reflux is kept for 30min, then the reflux ratio is adjusted to 0.0765, and H2O is extracted from the tower top; when the temperatures of the tower kettle and the tower top are respectively maintained at 143 +/-3 ℃ and 54 +/-3 ℃, starting total reflux, starting feeding, adjusting the feeding flow rate to be 1L/h, and adjusting the reflux ratio to 0.0765; after the temperatures of the tower kettle, the side line and the tower top reach 143 +/-3 ℃, 97 +/-3 ℃ and 54 +/-3 ℃, MEG barren solution is collected from the side line, the heat load of the tower kettle is adjusted, the temperatures of the tower kettle, the side line and the tower top are maintained to be 143 +/-3 ℃, 97 +/-3 ℃ and 54 +/-3 ℃, and then the operation is continued for 8 hours.
(5) And (3) analyzing the MEG concentration in the top of the tower, the MEG concentration in the side-draw liquid and the sodium ion content in the side-draw liquid at the sampling frequency of 30 min/time.
(6) After the experiment is finished, starting total reflux, closing the tower kettle for heating, carrying out heat tracing on the tower body, and closing circulating water for reflux after the temperature of the tower kettle reaches 60 ℃; guiding out residual liquid in the device, cleaning for 2 times by using tap water, and cleaning for 1 time by using deionized water; and (5) finishing, settling, cleaning and cleaning the experimental site.
Analyzing the produced liquid at the top of the tower through TOC, and determining the content of MEG in the produced liquid at the top of the tower; and analyzing the side-line produced liquid by a constant moisture meter to determine the content of MEG in the side-line produced liquid, and analyzing the side-line produced liquid by a sodium ion detector to determine the content of sodium ions in the side-line produced liquid. Analyzing the solutions extracted in different time periods, wherein the content of ethylene glycol in the extracted liquid at the top of the tower fluctuates up and down, but is less than 150ppm, and the average value is 50 ppm; the ethylene glycol in the side-draw liquid is stabilized at 90 +/-1 wt%, and the average content of sodium ions is 72 ppm. As shown in fig. 5, 6 and 7.
The conclusion obtained by the example 2 is that under the conditions that the material composition water comprises ethylene glycol and sodium chloride in a mass ratio of 50:47:3 and the operation pressure is 15kPaA, the content of MEG in the tower top produced liquid is less than 150ppm, and the content of MEG in the side line produced liquid can be stabilized at 90 +/-1 wt%, so that the reinjection and process requirements are met, the feasibility of completing the dehydration and desalination operation by using one rectifying tower is proved, the dehydration and desalination of the ethylene glycol are completed by adopting the method, a series of equipment such as flash tanks and the like are omitted, the operation flow is simple, the occupied area is reduced, and the equipment cost is reduced. Meanwhile, the average salt content in the side MEG was 72 ppm. The content is very small, the desalting effect is obvious, the desalting rate can reach more than 99 percent, and the scale formation and corrosion can be inhibited to the maximum extent.
Example 3:
conditions of the experiment
1. The number of the plates of the rectifying tower is 12, the feeding position is at the 9 th plate, the side draw position is at the 11 th plate, the reflux ratio is set to 0.0765, and the mass ratio of the side draw amount to the feeding amount is 0.33.
2. The operating pressure of the rectifying tower is 25kPaA, the tower top temperature is 64 +/-3 ℃, the side line extraction point temperature is controlled at 106 +/-3 ℃, and the tower kettle temperature is 153 +/-3 ℃.
3. The feed component water comprises ethylene glycol and sodium chloride (mass ratio) of 70:27:3, the feed amount is 1L/h, the overhead extraction amount is 0.64L/h, and the side extraction amount is 0.33L/h.
The experimental steps are as follows:
(1) checking the air tightness of the device, enabling the numerical value of the potentiometer to return to zero, and connecting circulating water;
(2) preparing a sodium chloride solution of ethylene glycol and water (70: 27:3) and adding the solution into a tower kettle of a rectifying tower until the solution is stopped adding at 1/3 of the tower kettle;
(3) starting a vacuum pump, starting the tower kettle for heating when the pressure is reduced to 25kPaA, and starting the tower body for heat tracing when the feed liquid in the tower kettle begins to boil;
(4) when the temperature of the tower top and the tower kettle is stable and the timing is started when reflux exists, the total reflux is kept for 30min, then the reflux ratio is adjusted to 0.0765, and H2O is extracted from the tower top; starting total reflux when the temperatures of the tower kettle and the tower top are respectively maintained at 153 +/-3 ℃ and 64 +/-3 ℃, starting feeding, adjusting the feeding flow rate to be 1L/h, and adjusting the reflux ratio to 0.0765; after the temperatures of the tower kettle, the side line and the tower top reach 153 +/-3 ℃, 106 +/-3 ℃ and 64 +/-3 ℃, MEG barren solution is collected from the side line, the heat load of the tower kettle is adjusted, and the operation is continuously carried out for 8 hours after the temperatures of the tower kettle, the side line and the tower top are maintained to be 153 +/-3 ℃, 106 +/-3 ℃ and 64 +/-3 ℃.
(5) And (3) analyzing the MEG concentration in the top of the tower, the MEG concentration in the side-draw liquid and the sodium ion content in the side-draw liquid at the sampling frequency of 30 min/time.
(6) After the experiment is finished, starting total reflux, closing the tower kettle for heating, carrying out heat tracing on the tower body, and closing circulating water for reflux after the temperature of the tower kettle reaches 60 ℃; guiding out residual liquid in the device, cleaning for 2 times by using tap water, and cleaning for 1 time by using deionized water; and (5) finishing, settling, cleaning and cleaning the experimental site.
Analyzing the produced liquid at the top of the tower through TOC, and determining the content of MEG in the produced liquid at the top of the tower; and analyzing the side-line produced liquid by a constant moisture meter to determine the content of MEG in the side-line produced liquid, and analyzing the side-line produced liquid by a sodium ion detector to determine the content of sodium ions in the side-line produced liquid. Analyzing the solutions extracted in different time periods, wherein the content of ethylene glycol in the extracted liquid at the top of the tower fluctuates up and down, but is less than 150ppm, and the average value is 70 ppm; the ethylene glycol in the side-draw liquid is stabilized at 90 +/-1 wt%, and the average content of sodium ions is 62 ppm. As shown in fig. 8, 9 and 10.
The conclusion obtained in example 3 is that under the conditions that the composition water of the material, namely ethylene glycol and sodium chloride, is 70:27:3 (mass ratio) and the operating pressure is 25kPaA, the content of MEG in the produced liquid at the top of the tower is less than 150ppm, and the content of MEG in the produced liquid at the side line can be stabilized at 90 +/-1 wt%, so that the reinjection and the process requirements are met, the feasibility of completing the dehydration and desalination operation by using one rectifying tower is proved, the dehydration and desalination of the ethylene glycol are completed by adopting the method, a series of equipment such as a flash tank and the like are omitted, the operation flow is simple, the occupied area is reduced, and the equipment cost is reduced. Meanwhile, the average salt content in the side MEG was 62 ppm. The content is very small, the desalting effect is obvious, the desalting rate can reach more than 99 percent, and the scale formation and corrosion can be inhibited to the maximum extent.
Example 4:
conditions of the experiment
1. The number of the plates of the rectifying tower is 12, the feeding position is at the 9 th plate, the side draw position is at the 11 th plate, the reflux ratio is set to 0.0765, and the mass ratio of the side draw amount to the feeding amount is 0.53.
2. The operating pressure of the rectifying tower is 25kPaA, the tower top temperature is 64 +/-3 ℃, the side line extraction point temperature is controlled at 106 +/-3 ℃, and the tower kettle temperature is 153 +/-3 ℃.
3. The feed component water comprises ethylene glycol and sodium chloride in a mass ratio of 50:45:5, the feed amount is 1L/h, the overhead extraction amount is 0.42L/h, and the side extraction amount is 0.53L/h.
The experimental steps are as follows:
(1) checking the air tightness of the device, enabling the numerical value of the potentiometer to return to zero, and connecting circulating water;
(2) preparing sodium chloride solution of ethylene glycol and water (water: ethylene glycol: sodium chloride is 50:45:5), adding into the tower kettle of the rectification tower until the tower kettle 1/3 is stopped adding;
(3) starting a vacuum pump, starting the tower kettle for heating when the pressure is reduced to 25kPaA, and starting the tower body for heat tracing when the feed liquid in the tower kettle begins to boil;
(4) when the temperature of the tower top and the tower kettle is stable and the timing is started when reflux exists, the total reflux is kept for 30min, then the reflux ratio is adjusted to 0.0765, and H2O is extracted from the tower top; starting total reflux when the temperatures of the tower kettle and the tower top are respectively maintained at 153 +/-3 ℃ and 64 +/-3 ℃, starting feeding, adjusting the feeding flow rate to be 1L/h, and adjusting the reflux ratio to 0.0765; after the temperatures of the tower kettle, the side line and the tower top reach 153 +/-3 ℃, 106 +/-3 ℃ and 64 +/-3 ℃, MEG barren solution is collected from the side line, the heat load of the tower kettle is adjusted, and the operation is continuously carried out for 8 hours after the temperatures of the tower kettle, the side line and the tower top are maintained to be 153 +/-3 ℃, 106 +/-3 ℃ and 64 +/-3 ℃.
(5) And (3) analyzing the MEG concentration in the top of the tower, the MEG concentration in the side-draw liquid and the sodium ion content in the side-draw liquid at the sampling frequency of 30 min/time.
(6) After the experiment is finished, starting total reflux, closing the tower kettle for heating, carrying out heat tracing on the tower body, and closing circulating water for reflux after the temperature of the tower kettle reaches 60 ℃; guiding out residual liquid in the device, cleaning for 2 times by using tap water, and cleaning for 1 time by using deionized water; and (5) finishing, settling, cleaning and cleaning the experimental site.
Analyzing the produced liquid at the top of the tower through TOC, and determining the content of MEG in the produced liquid at the top of the tower; and analyzing the side-line produced liquid by a constant moisture meter to determine the content of MEG in the side-line produced liquid, and analyzing the side-line produced liquid by a sodium ion detector to determine the content of sodium ions in the side-line produced liquid. Analyzing the solutions extracted at different time periods, wherein the content of ethylene glycol in the extracted liquid at the top of the tower fluctuates up and down, but is less than 150ppm, and the average value is 78 ppm; the ethylene glycol in the side-draw liquid is stabilized at 90 +/-1 wt%, and the average content of sodium ions is 114 ppm. As shown in fig. 11, 12 and 13.
The conclusion obtained in example 3 is that under the conditions that the composition water of the material, namely ethylene glycol and sodium chloride, is 50:47:5 (mass ratio) and the operating pressure is 25kPaA, the content of MEG in the produced liquid at the top of the tower is less than 150ppm, and the content of MEG in the produced liquid at the side line can be stabilized at 90 +/-1 wt%, so that the reinjection and the process requirements are met, the feasibility of completing the dehydration and desalination operation by using one rectifying tower is proved, the dehydration and desalination of the ethylene glycol are completed by adopting the method, a series of equipment such as a flash tank and the like are omitted, the operation flow is simple, the occupied area is reduced, and the equipment cost is reduced. Meanwhile, the average salt content in the side MEG was 114 ppm. The content is very small, the desalting effect is obvious, the desalting rate can reach more than 99 percent, and the scale formation and corrosion can be inhibited to the maximum extent.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
The invention is not the best known technology.
Claims (4)
1. A method for dehydration desalination of an offshore gas field ethylene glycol regeneration system, characterized in that the method comprises the steps of:
feeding the pretreated saliferous glycol-rich solution into a rectifying tower with a lateral line; in the rectifying tower, water vapor is condensed from the top of the rectifying tower through a condenser and enters a reflux tank, part of condensate in the reflux tank flows back into the rectifying tower, and part of condensate is discharged through a production water delivery pump; supersaturated glycol generated in the tower kettle of the rectifying tower is conveyed to a centrifuge for solid-liquid separation through a supersaturated glycol conveying pump, solid salt is collected and treated, and the glycol after centrifugal separation is heated by a circulating heater and returns to the tower kettle of the rectifying tower; qualified lean glycol products enter a qualified lean glycol conveying pipeline through a qualified lean glycol conveying pump at the lower part of the rectifying tower;
the rectifying tower is provided with a side line extraction outlet, the number of the tower plates is between 10 and 13, the position of the feed plate is between 7 and 10 plates, and the position of the side line extraction is between 9 and 12 plates;
the reflux ratio of the rectifying tower is 0.05-0.1, the mass ratio of the side extraction amount to the feeding amount is 0.3-0.8: 1;
the operating pressure of the rectifying tower is controlled to be 10-30kPaA, the tower top temperature is controlled to be 40-70 ℃, the side line extraction point temperature is controlled to be 80-120 ℃, and the tower kettle temperature is controlled to be 140-160 ℃.
2. The method for the dehydration desalination of an offshore gas field glycol regeneration system according to claim 1, wherein said pretreated salt-containing glycol-rich solution has a water content ranging from 30 wt% to 70 wt%, a salt content ranging from 1 wt% to 5 wt%, and an ethylene glycol content ranging from 27 wt% to 67 wt%.
3. The method for de-watering and desalting an offshore gas field glycol regeneration system according to claim 1, wherein the condenser is a coil condenser and the condensing medium is seawater.
4. An ethylene glycol regeneration system for an offshore gas field, characterized in that the system comprises: the top of the rectifying tower is connected with the inlet of a reflux tank through a condenser, and the discharge port of the reflux tank is also connected with a production water delivery pump and the top of the rectifying tower through pipelines respectively; a side draw outlet of the rectifying tower is connected with a qualified lean glycol delivery pump; the tower kettle of the rectifying tower is connected with a supersaturated glycol delivery pump, the supersaturated glycol delivery pump is also connected with a centrifugal machine, and the centrifugal machine is also connected with the tower kettle of the rectifying tower; the vacuum pump is connected with the reflux tank; the condenser is connected with a seawater pipeline;
the conveying pipeline of the salt-containing glycol-rich solution is connected with the feed inlet of the rectifying tower; the production water delivery pump is also connected with a delivery pipeline of the production water; the qualified lean glycol delivery pump is also connected with a delivery pipeline of the qualified lean glycol.
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| CN114369009A (en) * | 2021-12-28 | 2022-04-19 | 中海油天津化工研究设计院有限公司 | Method for removing divalent salt in glycol regeneration system of offshore gas field |
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| CN110721555A (en) * | 2019-11-12 | 2020-01-24 | 中建安装集团有限公司 | Device and process for purifying maleic anhydride by novel solvent absorption method |
| CN112274958A (en) * | 2020-09-28 | 2021-01-29 | 重庆前卫科技集团有限公司 | Ethylene glycol regeneration and recovery system and ethylene glycol recovery method in deep sea natural gas development process |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110721555A (en) * | 2019-11-12 | 2020-01-24 | 中建安装集团有限公司 | Device and process for purifying maleic anhydride by novel solvent absorption method |
| CN112274958A (en) * | 2020-09-28 | 2021-01-29 | 重庆前卫科技集团有限公司 | Ethylene glycol regeneration and recovery system and ethylene glycol recovery method in deep sea natural gas development process |
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| CN114369009A (en) * | 2021-12-28 | 2022-04-19 | 中海油天津化工研究设计院有限公司 | Method for removing divalent salt in glycol regeneration system of offshore gas field |
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