Method, system for removing water from carbon dioxide fluid using triethylene glycol and applications thereof

Abstract

This application relates to a method and system for removing water from a carbon dioxide fluid using triethylene glycol, and the application of this method in transporting supercritical carbon dioxide fluid. The method includes calculating a correction factor: obtaining a correction factor R based on the critical pressure of the carbon dioxide fluid according to formula (I): R = 0.7195 - 0.02729P c +0.0118T(I), where P c The critical pressure of the carbon dioxide fluid is given by T, where T is the temperature range of 20℃-30℃; the corrected pressure is calculated using formula (II). b :P b =P c *R(II); Pressure-boosted dehydration: The pressure of the carbon dioxide fluid is increased to the corrected pressure P through multi-stage pressure-boosted cooling. b The process involves cooling to remove some of the water from the carbon dioxide fluid, with the temperature after each stage of pressurization and cooling controlled within the range of 20°C to 30°C. Triethylene glycol dehydration is then performed, using a triethylene glycol absorbent to further remove water from the pressurized and dehydrated carbon dioxide fluid. The method and system of this application can reduce energy consumption and lower process costs.

Description

Technical Field

[0001] This application relates to the field of fluid separation, and more particularly to a method and system for removing water from a carbon dioxide fluid using triethylene glycol, and its application. Background Technology

[0002] Under low-pressure conditions, the carbon dioxide fluid obtained from the carbon capture unit of a natural gas processing plant or a CCS (Carbon Capture and Storage) / CCUS (Carbon Capture, Utilization & Storage) system typically contains varying amounts of water (water vapor or free water), which can often lead to serious consequences. For example, the presence of water in the carbon dioxide fluid can not only form acids that corrode pipelines and equipment, but also significantly increase the hydrate formation temperature, causing hydrates to form even at higher temperatures, affecting pipeline throughput, and potentially leading to serious consequences such as valve blockage, pipeline icing, and equipment damage, thus impacting safe production.

[0003] Currently, the dehydration of carbon dioxide fluid is a process of removing moisture from the gas to prevent the precipitation of free water. The main method currently used is triethylene glycol solvent absorption. After dehydration, the gas dew point drops by no more than -45°C. However, this method has the problem of high energy consumption for solvent regeneration, resulting in high operating costs for the equipment. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0005] In one aspect, this application provides a method for removing water from a carbon dioxide fluid using triethylene glycol, comprising the following steps:

[0006] Calculate the correction factor: Obtain the correction factor R based on the critical pressure of the carbon dioxide fluid according to formula (I):

[0007] R = 0.7195 - 0.02729P c +0.0118T(I),

[0008] Where P c The critical pressure of the carbon dioxide fluid is T, and the temperature is in the range of 20℃-30℃.

[0009] Calculate the corrected pressure: Obtain the corrected pressure P according to formula (II). b :

[0010] P b =P c *R(II);

[0011] Pressurized dehydration: The pressure of the carbon dioxide fluid is increased to the corrected pressure P through multi-stage pressurized cooling. b The system is cooled to remove some of the water from the carbon dioxide fluid, with the temperature after each stage of pressurization and cooling controlled within the range of 20°C to 30°C.

[0012] Triethylene glycol dehydration: Water in the carbon dioxide fluid after pressurized dehydration is further removed using a triethylene glycol absorbent.

[0013] As used in this application, the term "carbon dioxide fluid" refers to a fluid system consisting of carbon dioxide at a mole fraction (dry basis) greater than or equal to 95% and other chemical substances (such as nitrogen, oxygen, hydrogen sulfide, etc.) at a mole fraction (dry basis) less than or equal to 5%.

[0014] Those skilled in the art can calculate the critical pressure P of the carbon dioxide fluid in the temperature range of 20℃-30℃ based on the dry-basis composition of the above-mentioned carbon dioxide fluid using the Peng-Robinson equation of state and phase equilibrium calculations (such as with commercially available chemical process simulation software like HYSYS). c For example, the critical pressure P of the carbon dioxide fluid. c It can be within the range of 7.39MPa-8.1MPa.

[0015] In an exemplary embodiment, in the pressurization and dehydration step, the number of stages of the multi-stage pressurization cooling is determined by the initial pressure of the carbon dioxide fluid. In each stage of pressurization cooling, the compression ratio after pressurization is in the range of 4-5 compared to before pressurization, until the pressure is increased to the corrected pressure P. b .

[0016] In an exemplary embodiment, the method further includes separating the cooled carbon dioxide fluid in each stage of pressurization cooling to remove free water generated in each stage of pressurization cooling.

[0017] In another aspect, this application provides a system for removing water from a carbon dioxide fluid using triethylene glycol, comprising:

[0018] A pressurized dehydration device is configured to perform multi-stage pressurization and cooling on the carbon dioxide fluid until the pressure is increased to a corrected pressure P. b The system is cooled to remove some of the water from the carbon dioxide fluid, with the temperature after each stage of pressurization and cooling controlled within the range of 20°C to 30°C.

[0019] A triethylene glycol dehydration unit is configured to further remove water from the pressurized dehydrated carbon dioxide fluid using a triethylene glycol absorbent.

[0020] The corrected pressure P is obtained according to the following formulas (I) and (II). b :

[0021] R = 0.7195 - 0.02729P c +0.0118T(I),

[0022] P b =P c *R(II),

[0023] P c R is the critical pressure of the carbon dioxide fluid, R is a correction factor based on the critical pressure of the carbon dioxide fluid, and T is the temperature in the range of 20℃-30℃.

[0024] In an exemplary embodiment, the pressurized dehydration device may include multiple pressurized dehydration units, each of which performs a single stage of pressurized cooling. For example, if a three-stage pressurized cooling system is used, it may include three pressurized dehydration units.

[0025] In an exemplary embodiment, each pressurized dehydration unit includes a pressurized compressor, a cooler, and a separator. The cooler may include a circulating water cooler, an air cooler, etc.

[0026] In another aspect, this application provides the application of the above-described method in transporting supercritical carbon dioxide fluid, including:

[0027] The carbon dioxide fluid from a carbon capture and storage system (CCS) / carbon capture, utilization and storage system (CCUS) or acid gas reinjection system is dehydrated using the above method, wherein the initial pressure of the carbon dioxide fluid is less than its critical pressure.

[0028] The dehydrated carbon dioxide fluid is pressurized to a pressure greater than its critical pressure, making the carbon dioxide fluid a supercritical carbon dioxide fluid.

[0029] After the supercritical carbon dioxide fluid is further pressurized to an external output pressure greater than the critical pressure, the supercritical carbon dioxide fluid with external output pressure is pumped and transmitted in the CCS / CCUS system or acid gas reinjection system.

[0030] In an exemplary embodiment, pressurizing the dehydrated carbon dioxide fluid to a pressure greater than its critical pressure includes using a critical pressure boosting compressor, a cooler, and a separator.

[0031] The method and system of this application are particularly suitable for applications requiring the pressurization and external discharge of dehydrated carbon dioxide fluid, such as CCS / CCUS systems or acid gas reinjection systems, in which the external discharge pressure is greater than or much greater than the pressure of the carbon dioxide fluid before dehydration.

[0032] In existing technologies, the obtained carbon dioxide fluid is typically fed directly into a triethylene glycol dehydration unit for dehydration, and then pressurized to the output pressure before being pumped for transport. However, this application optimizes the dehydration process by using a modified pressure based on the critical pressure of the carbon dioxide fluid, dividing the process into two parts using this specific pressurization point as a node. First, a portion of the water is removed through pressurized dehydration at a specific pressure, and then the pressurized dehydrated carbon dioxide fluid undergoes a secondary dehydration with triethylene glycol. The inventors of this application discovered that at this specific modified pressure, the saturated water content of the carbon dioxide fluid reaches a minimum, thus enabling a more economical and efficient natural dehydration of the carbon dioxide fluid through pressurized dehydration at this specific pressure.

[0033] Compared with a one-stage triethylene glycol dehydration process, this application divides the triethylene glycol dehydration process into two stages, making maximum use of the fluid pressurization dehydration effect, reducing the amount of triethylene glycol circulating in the triethylene glycol dehydration device, reducing the energy consumption of the entire dehydration system, and significantly enhancing economic benefits.

[0034] The system and method of this application enable the water content in carbon dioxide fluid to be reduced to less than 200 ppm with maximum economic efficiency, thereby enabling its use in carbon dioxide sequestration or oil displacement.

[0035] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0036] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0037] Figure 1 This is a schematic flowchart illustrating a method for removing water from a carbon dioxide fluid using triethylene glycol, according to an exemplary embodiment of this application; and

[0038] Figure 2 This is a schematic diagram illustrating a method for dehydrating and transporting supercritical carbon dioxide fluid using triethylene glycol, according to an exemplary embodiment of this application. Detailed Implementation

[0039] The embodiments described in this application are exemplary and not restrictive, and it will be apparent to those skilled in the art that there are many more embodiments and implementations within the scope of the embodiments described in this application.

[0040] Because pipeline transportation of supercritical carbon dioxide offers advantages such as low viscosity and high flow rate, CCS / CCUS systems or acid gas reinjection systems ideally require supercritical transportation of carbon dioxide at ambient temperature (20°C-30°C). Furthermore, the carbon dioxide used in these systems typically contains some water (water vapor or free water), necessitating water removal before transportation. Currently, such carbon dioxide is usually directly fed into a triethylene glycol dehydration unit for dehydration, then pressurized to an external pressure exceeding the critical pressure for delivery, or directly pressurized to a pressure exceeding the critical pressure before triethylene glycol dehydration. However, the inventors of this application have discovered that such methods require pressurizing more water in the fluid and removing more water with triethylene glycol, thus increasing energy consumption and reducing efficiency.

[0041] Therefore, this application provides an improved method and system for removing water from carbon dioxide fluid using triethylene glycol.

[0042] Example 1:

[0043] The method for removing water from carbon dioxide fluid using triethylene glycol may include the following steps:

[0044] S100: Calculate the correction factor.

[0045] Specific steps may include obtaining a correction factor R based on the critical pressure of the carbon dioxide fluid according to formula (I):

[0046] R = 0.7195 - 0.02729P c +0.0118T(I),

[0047] Where P c The critical pressure of the carbon dioxide fluid is T, and the temperature is in the range of 20℃-30℃.

[0048] S200: Calculate the corrected pressure.

[0049] The specific steps may include obtaining the corrected pressure P according to formula (II). b :

[0050] P b =P c *R(II).

[0051] S300: Pressure-boosted dehydration.

[0052] Specific steps may include increasing the pressure of the carbon dioxide fluid to a corrected pressure P through multi-stage pressurization and cooling. bThe system is cooled to remove some of the water from the carbon dioxide fluid, with the temperature after each stage of pressurization and cooling controlled within the range of 20°C to 30°C.

[0053] S400: Triethylene glycol dehydration.

[0054] Specific steps may include using a triethylene glycol absorbent to further remove water from the pressurized and dehydrated carbon dioxide fluid.

[0055] Example 2

[0056] This embodiment describes the application of the method and system of this application, such as its application in transporting supercritical carbon dioxide fluid. Specifically, it may include the following steps:

[0057] S1000: Dehydrates carbon dioxide fluid from a carbon capture and storage system (CCS) / carbon capture, utilization and storage system (CCUS) or an acid gas reinjection system, wherein the initial pressure of the carbon dioxide fluid is less than its critical pressure.

[0058] Specific steps may include:

[0059] Carbon dioxide fluid is purified carbon dioxide gas containing impurities. Gas composition and operating conditions (absolute pressure).

[0060] Gas size to be dehydrated: 20 × 10 4 Nm 3 / d

[0061] Pressure of the gas to be dehydrated: 131 kPa

[0062] Temperature upon entry: 40℃

[0063] External pressure requirement: ≥8.0MPa

[0064] Moisture content requirement for export: ≤200ppm

[0065] The dry basis composition of the carbon dioxide fluid to be dehydrated is shown in Table 1 below:

[0066] Table 1

[0067] Components <![CDATA[CO2]]> <![CDATA[N2]]> <![CDATA[O2]]> mole fraction, % 98 1 1

[0068] Based on the dry basis composition of the carbon dioxide fluid to be dehydrated shown in Table 1, the critical pressure P of the carbon dioxide fluid to be dehydrated can be obtained by performing phase equilibrium calculations using the Peng-Robinson equation of state (e.g., using commercially available chemical process simulation software such as HYSYS). c The critical pressure P based on carbon dioxide fluid is 7.64 MPa. Furthermore, based on the outlet temperature of 30°C after pressurization and cooling, the critical pressure P is calculated according to formula (I). cThe correction factor R is 0.865, and the corrected pressure P is finally calculated according to formula (II). b It is 6.61 MPa.

[0069] Based on the initial pressure of 131 kPa and the corrected pressure of 6.61 MPa of the carbon dioxide fluid to be dehydrated, and based on the requirement that the compression ratio after each pressurization stage is in the range of 4-5 compared to before pressurization, this embodiment can use a three-stage pressurization and cooling process to implement the pressurization and dehydration steps.

[0070] The pressurized dehydration step may include:

[0071] The carbon dioxide fluid to be dehydrated is pressurized by the first-stage booster compressor 1 and then enters the first-stage booster cooler 2 to be cooled to 30°C and the pressure reaches 400 kPa. Then, it passes through the first-stage booster separator 3 to remove the free water generated after booster cooling (flow rate 139 kg / h). The free water is then transported to the sewage tank.

[0072] The gas phase from the upper outlet of the first-stage booster separator 3 then enters the second-stage booster compressor 4 and the second-stage booster cooler 5 in sequence, where it is further boosted to 1.8 Ma and cooled to 30°C. The gas phase is then separated into free water by the second-stage booster separator 6. The free water flows out from the lower outlet of the second-stage booster separator 6 (flow rate 54.09 kg / h) and is then transported to the wastewater tank.

[0073] The gas from the upper outlet of the second-stage booster separator 6 finally enters the third-stage booster compressor 7 and is boosted to the critical pressure of 6.61 MPa calculated earlier. Then it is cooled to 30°C by the third-stage booster cooler 8 and enters the third-stage booster separator 9. The free water flows out from the lower outlet of the third-stage booster separator 9 (flow rate 8.96 kg / h) and is transported to the sewage tank.

[0074] Through this pressurization and dehydration step, the water content of the carbon dioxide fluid can be reduced from 57,069 ppm before dehydration to 1,113 ppm.

[0075] The triethylene glycol dehydration step may include:

[0076] The gas phase from the upper outlet of the third-stage booster separator 9 enters the triethylene glycol dehydration unit 10 for deep dehydration to a water content of 200 ppm. The dehydrated water (7.67 kg / h) is then transported to the wastewater tank.

[0077] S2000: The dehydrated carbon dioxide fluid is pressurized to a pressure greater than its critical pressure, making the carbon dioxide fluid a supercritical carbon dioxide fluid.

[0078] Specific steps may include the following:

[0079] The carbon dioxide fluid, after being dehydrated in the triethylene glycol dehydration unit 10, enters the critical booster compressor 11 to boost the carbon dioxide fluid to 8 MPa, which is greater than the critical pressure of carbon dioxide fluid 7.64 MPa. It is then cooled to 30°C by the critical booster cooler 12, making the carbon dioxide fluid a supercritical fluid.

[0080] S3000: After the supercritical carbon dioxide fluid is further pressurized to an external output pressure greater than the critical pressure, the supercritical carbon dioxide fluid with external output pressure is pumped and transmitted in the CCS / CCUS system or acid gas reinjection system.

[0081] Specific steps may include the following:

[0082] The supercritical carbon dioxide fluid can be pressurized to 9 MPa by the external booster pump 13 and then pumped out.

[0083] In this embodiment, the required triethylene glycol circulation rate within the triethylene glycol dehydration device is 0.12 m³. 3 / h, the input power of the solution circulation pump is 0.25kW, and the gas consumption for triethylene glycol regeneration heating is 0.80m³ / h. 3 / h.

[0084] In this embodiment, the carbon dioxide fluid treated by the dehydration method and system of this application has a water removal flow rate of 209.7 kg / h and an external gas water content of 200 ppm. The total compression power of the system is 1317 kW (including 4 booster compressors, an external booster pump, and a triethylene glycol circulation pump), the daily power consumption is 31245 kWh, the heating load is 7919 kW, and the daily gas consumption is 20.06 m³. 3 The daily comprehensive energy consumption is 391.2 tons of standard coal.

[0085] In contrast, under the same composition of the carbon dioxide fluid to be dehydrated, operating conditions, and treatment conditions, if triethylene glycol is directly dehydrated, the triethylene glycol circulation volume will increase to 0.14 m³. 3 / h, total compression power increased to 1342kW, daily power consumption increased to 32211kWh, and daily gas consumption increased to 23.53m³. 3 The daily comprehensive energy consumption increased to 399 tons of standard coal.

[0086] Therefore, for large-scale dehydration and transportation of carbon dioxide fluids, the method and system of this application can significantly reduce energy consumption, improve process efficiency, and enhance economic benefits.

[0087] While the embodiments disclosed in this application are as described above, the content is merely for the purpose of facilitating understanding of this application and is not intended to limit this application. Any person skilled in the art to which this application pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application; however, the scope of protection of this application shall still be determined by the scope defined in the appended claims.

Claims

1. A method for removing water from a carbon dioxide fluid using triethylene glycol, characterized in that, Includes the following steps: Calculate the correction factor: Obtain the correction factor based on the critical pressure of the carbon dioxide fluid according to formula (I). R : R =0.7195-0.02729P c +0.0118T(I), Where P c The critical pressure of the carbon dioxide fluid is T, and the temperature is in the range of 20℃-30℃. Calculate the corrected pressure: Obtain the corrected pressure P according to formula (II). b : P b =P c * R (II); Pressurized dehydration: The pressure of the carbon dioxide fluid is increased to the corrected pressure P through multi-stage pressurized cooling. b The system is cooled to remove some of the water from the carbon dioxide fluid, with the temperature after each stage of pressurization and cooling controlled within the range of 20°C to 30°C. Triethylene glycol dehydration: Water in the carbon dioxide fluid after pressurized dehydration is further removed using a triethylene glycol absorbent.

2. The method according to claim 1, characterized in that, In the pressurization and dehydration step, the number of stages of the multi-stage pressurization cooling is determined by the initial pressure of the carbon dioxide fluid. In each stage of pressurization cooling, the compression ratio after pressurization is within the range of 4-5 compared to before pressurization, until the pressure is increased to the corrected pressure P. b .

3. The method according to claim 1, characterized in that, The method further includes separating the cooled carbon dioxide fluid in each stage of pressurization cooling to remove free water generated in each stage of pressurization cooling.

4. The method according to claim 1, characterized in that, The critical pressure of the carbon dioxide fluid is in the range of 7.39 MPa to 8.1 MPa.

5. The application of the method according to any one of claims 1-4 in transporting supercritical carbon dioxide fluid, characterized in that, include: Carbon dioxide fluid from a carbon capture and storage system, a carbon capture, utilization and storage system, or an acid gas reinjection system is dehydrated by the method according to any one of claims 1-4, wherein the initial pressure of the carbon dioxide fluid is less than its critical pressure. The dehydrated carbon dioxide fluid is pressurized to a pressure greater than its critical pressure, making the carbon dioxide fluid a supercritical carbon dioxide fluid. After the supercritical carbon dioxide fluid is further pressurized to an external output pressure greater than the critical pressure, the supercritical carbon dioxide fluid with external output pressure is pumped and transmitted in the carbon capture and storage system, the carbon capture, utilization and storage system, or the acid gas reinjection system.

6. The application according to claim 5, characterized in that, Pressurizing dehydrated carbon dioxide fluid to a pressure greater than its critical pressure involves using a critical pressure boosting compressor, cooler, and separator.

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