CN-121993740-A - Supercritical CO based on compression factor change2Stable supercharging method

CN121993740ACN 121993740 ACN121993740 ACN 121993740ACN-121993740-A

Abstract

The invention discloses a supercritical CO 2 stable supercharging method based on compression factor change, which comprises the steps of determining a temperature threshold value of exhaust temperature of each stage of supercharging according to supercharging parameters, setting the stage number to be supercharged, the exhaust pressure and the exhaust temperature of each stage and the air inlet temperature of the next stage, acquiring a change rate trend chart of a compression factor z when the compression factor z changes along with the temperature and the pressure, determining the change rule of the compression factor z along with the temperature under the air inlet and exhaust pressure of each stage according to the change rate trend chart, limiting the change range of the compression factor z within a set change rate range, setting an inter-stage temperature accurate control system in the process from the exhaust of each stage to the air inlet of the next stage, and accurately controlling the temperature within the air inlet temperature fluctuation range of the next stage set in the step one according to the change rate range set by the compression factor z. The invention can boost the mixture of CO 2 and CO 2 from the conventional gas state to the supercritical state, and the highest pressure after the pressurization can reach 50MPa, thereby meeting the high-pressure gas injection requirement of CCUS engineering.

Inventors

WU ZENING
HOU XIAOBING
WANG YOUPENG
ZHENG PENGJU
LU YI

Assignees

中国石油化工股份有限公司
中石化石油机械股份有限公司

Dates

Publication Date: 20260508
Application Date: 20251230

Claims (9)

1. A supercritical CO 2 stable pressurization method based on compression factor change is characterized in that a multi-stage pressurization method is adopted to stably pressurize a mixed gas of normal-pressure or low-pressure gaseous CO 2 and CO 2 to a high-pressure supercritical state, and the method comprises the following steps: Firstly, determining a temperature threshold value of the exhaust temperature of each stage of supercharging according to supercharging parameters, and then setting the stage number required to be supercharged, the exhaust pressure of each stage, the exhaust temperature and the air inlet temperature of the next stage by combining the air inlet pressure and the exhaust pressure; step two, obtaining a change rate trend chart of the compression factor z along with the change of temperature and pressure; step three, combining the pressure change in the pressurizing process, determining the change rule of the compression factor z along with the temperature under the air inlet and outlet pressure of each level according to the change rate trend chart, and limiting the change range of the compression factor z to the set change rate range so as to obtain a corresponding temperature control limiting range; setting an inter-stage temperature accurate control system in the process from the exhaust of each stage to the air intake of the next stage, and accurately controlling the temperature in the air intake temperature fluctuation range of the next stage set in the step one according to the change rate range set by the compression factor z in the step three and the temperature control limiting range.
2. The method for stabilizing and pressurizing supercritical CO 2 based on the variation of the compression factor according to claim 1, wherein the second step specifically includes: Firstly, setting and calculating a compression factor z value of each set temperature unit span in a set temperature range under a specific pressure; secondly, acquiring a set pressure range through calculation and analysis, calculating a corresponding temperature range under the span of the set pressure unit in the corresponding pressure range, simultaneously calculating a compression factor z value under each set temperature unit span, and storing records; Thirdly, performing data arrangement and storage on all the calculated z values by taking the abscissa as the temperature and the ordinate as the pressure; then, calculating and recording the change rate of the z value under all pressure and temperature changes, wherein the calculation formula of the change rate of the z value is that the difference value of the z value of the highest temperature and the lowest temperature is divided by the z value of the lowest temperature under one temperature unit span; And finally, displaying the calculation result through a diagram, displaying by taking the abscissa as the temperature and the ordinate as the pressure, dividing the intensity range of the z value change rate, and distinguishing by different colors.
3. The method for stabilizing and pressurizing supercritical CO 2 based on variation of compression factor according to claim 1, wherein in the fourth step, before the temperature is precisely controlled, the compression factor is further ordered with the intensity of variation of temperature in the intake state of each pressurizing stage, and the priority of temperature control is determined for priority control in the control process.
4. The supercritical CO 2 stable pressurizing method based on the compression factor change as claimed in claim 1, wherein in the fourth step, the accurate temperature control system comprises an air cooler, which comprises a hollow sealed box body, a variable frequency fan arranged at the lower part of the box body, various louvers arranged on the box body and a multi-stage cooling tube bundle, a pair of louvers C are symmetrically arranged at the lower part of the box body, the multi-stage cooling tube bundles corresponding to each stage of temperature control system are arranged in the box body, the louvers X1-X4 which are arranged in the box body and are independently operated are respectively in one-to-one correspondence, the cooling of each stage of temperature control system is respectively and independently controlled by the louvers X1-X4, the top of the box body is also provided with a louver D which covers the multi-stage cooling tube bundle, the box body is also provided with a hot air circulation louver R which covers the multi-stage cooling tube bundle, and the various louvers are controlled and opened by a stepping motor to control the opening angle so as to control the cooling adjustment.
5. The compression factor variation-based supercritical CO 2 stable supercharging method of claim 4, wherein the accurate temperature control system further comprises an intelligent central controller, the intelligent central controller comprises a temperature measuring component and a central controller, the temperature measuring component is arranged at the downstream of each stage of cooling tube bundles, namely at the inlet position of next stage supercharging equipment, the temperature measuring component transmits data to the central controller, and the central controller controls the air cooler to act for temperature adjustment.
6. The method for stabilizing and pressurizing supercritical CO 2 based on the variation of compression factor according to claim 5, wherein in the process of system debugging, the hysteresis of temperature measuring component to temperature variation is evaluated, and the central controller is adjusted accordingly, specifically, when the air cooler shutter switch is operated by 5%, the difference between the time point of the operation and the time point of stabilizing the downstream temperature measuring component after the start of obvious variation is recorded, then the fluid transmission delay time of the system is measured, and the time parameter is input into the delay function module of the central controller, so as to apply a waiting judging period of delay time to the output of all temperature control instructions, and avoid the repeated or contradictory instructions from being sent out during the feedback signal hysteresis period.
7. The method for stabilizing and pressurizing supercritical CO 2 based on compression factor variation according to claim 5, wherein in the fourth step, the accurate temperature control method is as follows: Firstly, taking a supercharging stage with the most severe change of a compression factor z value along with temperature as the most advanced stage, requiring that the air inlet temperature of the supercharging stage should meet the condition that the z value does not fall in the range of the change rate set in the step three, determining the supercharging air inlet temperature as tx, and designing the condition judgment as tx+/-precision value as a steady-state and no-action interval according to the precision set value by a control logic; And secondly, judging a temperature value lower than the tx-precision value as a low temperature zone, performing temperature compensation logic operation according to temperature measurement feedback, judging a temperature value higher than the tx+ precision value as a high temperature zone, and performing cooling logic operation according to temperature measurement feedback.
8. The method for stable pressurization of supercritical CO 2 based on compression factor variation according to claim 7, wherein the temperature compensation logic operation and the cooling logic operation are specifically: acquiring the temperature monitored by the temperature measuring component, judging whether the temperature is in a steady state and no-action interval, if so, keeping the current state, and if not, carrying out the next judgment; If the temperature is smaller than the low temperature interval, judging whether the variable frequency fan is stopped, if not stopping, reducing the opening angle of the corresponding shutter X until the shutter is closed, and if the temperature is smaller than the low temperature interval, opening the shutter R or reducing the rotating speed of the variable frequency fan; If the temperature is higher than the high temperature interval, judging whether the corresponding shutter X is fully opened, if not, enlarging the opening angle of the corresponding shutter X, if so, judging whether the rotating speed of the variable frequency fan is maximum, if so, opening the shutters D and C, closing the shutter R, and if not, enlarging the rotating speed of the variable frequency fan.
9. The method for stably pressurizing supercritical CO 2 based on the variation of the compression factor according to claim 1, wherein in the first step, the pressurizing process flow is that a process medium enters a first-stage air inlet washing tank, filtered air enters a buffer tank for buffering, then is subjected to first-stage pressurizing, the pressurized air enters a second-stage temperature control system for cooling and temperature control, then enters a second-stage air inlet washing tank, the filtered air enters the buffer tank for buffering, then is subjected to second-stage pressurizing, the pressurized air enters a third-stage temperature control system for cooling and temperature control, then enters a third-stage air inlet washing tank, the filtered air enters the buffer tank for buffering, then is subjected to third-stage pressurizing, the pressurized air enters a fourth-stage temperature control system for cooling and temperature control, then enters a fourth-stage air inlet washing tank for buffering, the pressurized air enters an outlet temperature control system for cooling and temperature control, and the medium is discharged outwards when the pressure of the medium reaches the required pressure.

Description

Supercritical CO 2 stable pressurization method based on compression factor change Technical Field The invention relates to the technical field of CCUS engineering. More particularly, the invention relates to a supercritical CO 2 stable pressurization method based on compression factor change. Background The CCUS (carbon capture, utilization and sequestration) technology is a key technology for coping with climate crisis, and urgency of the CCUS technology is a key for realizing green low-carbon development, and the CCUS technology has formed consensus on the global scale. Modern CCUS technology generally injects captured carbon resources (CO 2 and CO 2 mixed gas) into depleted oil fields to realize oil displacement and yield increase (EOR), and forms a circular economy closed loop of black gold and greenhouse gases. In order to achieve CO 2 gas injection and yield increase, the trapped carbon resources (CO 2 and CO 2 gas mixture) need to be pressurized to a high-pressure supercritical state and then injected into the oil well. The supercritical CO 2 supercharging equipment is CCUS core equipment, but the domestic application of the CO 2 supercharging equipment of each oil field is less, the domestic supercritical CO 2 mixed medium gas injection supercharging equipment is insufficient in self-supporting technical capability, in order to respond to the green low-carbon development strategy, the aims of 'carbon peak reaching and carbon neutralization' are comprehensively realized by helping China, the development of a high-pressure supercritical CO 2 supercharging technology is urgently needed, a supercritical CO 2 stable supercharging method is sought, and the high-pressure supercritical CO 2 gas injection requirement of CCUS engineering of each large oil and gas field in China is met. CO 2 has a high critical parameter (critical temperature tc=31.1 ℃, critical pressure pc=7.38 MPa), and its supercritical state has the characteristic advantages of both high density of liquid and low viscosity of gas. In the pressurizing process, CO 2 enters a supercritical state from a conventional gas state and is accompanied by temperature change, and the temperature of a CO 2 medium is controlled, so that pressure and flow speed fluctuation in the pressurizing process are prevented, and even CO 2 liquefaction is avoided. The technical problems that 1, the pressure boosting process CO 2 or CO 2 is in a mixed gas phase state change (supercritical state is changed into liquid state due to temperature, pressure and other parameter changes) so that pressure boosting cannot be carried out and even equipment is damaged are mainly solved. 2. The pressure and flow speed of the medium in the pressurizing process are obviously changed due to temperature change, the pressurizing process is unstable, abnormal noise and vibration of equipment are caused, and even the service life of equipment is shortened. Disclosure of Invention The invention aims to provide a high-pressure supercritical CO 2 multistage stable pressurization method based on compression factor change, which comprehensively considers the phase stability of a multistage pressurization process and the parameter stability of the pressurization process, and provides a stable pressurization method for stabilizing the multistage pressurization of high-pressure supercritical CO 2 with z value by accurately controlling the temperature of an inter-stage cooler while the compression factor z value change rate in the pressurization process is used for expressing the stabilization degree of the pressurization process in the pressurization process while the phase state of the pressurization process is ensured. The method can boost the mixture of CO 2 and CO 2 from the conventional gas state to the supercritical state, and the highest pressure after the pressurization can reach 50MPa, thereby meeting the high-pressure gas injection requirement of CCUS engineering. In order to solve the technical problems, the invention provides a supercritical CO 2 stable pressurizing method based on compression factor change, which adopts a multistage pressurizing method to stably pressurize a mixed gas of normal-pressure or low-pressure gaseous CO 2 and CO 2 to a high-pressure supercritical state, and comprises the following steps: Firstly, determining a temperature threshold value of the exhaust temperature of each stage of supercharging according to supercharging parameters, and then setting the stage number required to be supercharged, the exhaust pressure of each stage, the exhaust temperature and the air inlet temperature of the next stage by combining the air inlet pressure and the exhaust pressure; step two, obtaining a change rate trend chart of the compression factor z along with the change of temperature and pressure; step three, combining the pressure change in the pressurizing process, determining the change rule of the compression factor z along with the temperature under the air inlet