An efficient ccus process

Abstract

The application discloses a kind of efficient CCUS processes, comprising the following steps: raw gas is enriched to low concentration CO2 by CO2 capture process;The raw gas after enrichment is pressurized by CO2 compression process;The raw gas after pressurization is removed by CO2 purification process harmful substances such as sulfur, nitrogen and chlorine;The CO2 mixed gas after purification is separated by CO2 rectification process, and O2, N2, CH4, CO, C2H 10 , light hydrocarbon and other recyclable substances are separated from CO2.The application process is simple, energy is effectively recovered, various recyclable gases are effectively separated as high value-added products, and the economic efficiency is good, with low equipment investment and operating cost.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide treatment technology, specifically a highly efficient CCUS process for the coal chemical industry. Background Technology

[0002] Since the last century, rapid urbanization and industrialization have had a significant impact on the climate. Greenhouse gas emissions, primarily carbon dioxide, have led to major global problems such as global warming and ocean acidification, severely affecting human survival and development. Therefore, reducing CO2 emissions is crucial for mitigating global warming and achieving carbon neutrality.

[0003] Carbon capture, utilization and storage (CCUS) has always been a focus of international attention and is considered the most promising and effective means of emission reduction.

[0004] CCUS technology involves multiple technical aspects such as carbon dioxide capture, transportation, and storage. Its high cost is a significant factor hindering the development of the entire industry chain. Ultimately, this stems from the poor economic viability of the projects themselves, leading to insufficient motivation from governments and capital enterprises to jointly promote them.

[0005] Publication No. 215479714U discloses a condensing hydrogen production converter system equipped with a PSA tail gas CCUS system, including: a conversion section, a first medium heating section, a high-temperature air preheating section, a second medium heating section, a low-temperature air preheating section, a condensing air preheating section, a flue gas fan, a chimney, a purified tail gas and supplementary fuel heating section, a booster compressor, a CCUS system, and a PSA system; the high-temperature flue gas from the conversion section enters the first medium heating section for heat exchange and cooling; then it is divided into two paths, one of which enters the high-temperature air preheating section to exchange heat with air from the low-temperature air preheating section; the other path of flue gas enters the parallel purified tail gas and supplementary fuel heating section to exchange heat with the purified tail gas and supplementary fuel of the CCUS system pressurized by the booster compressor. This utility model effectively utilizes the waste heat of the flue gas, which can reduce the flue gas outlet temperature to below 60-120℃, improve the thermal efficiency of the converter, and further reduce CO2 emissions. The solution focuses on how to effectively utilize the waste heat of the high-temperature flue gas from the conversion section to improve the thermal efficiency of the converter. It does not involve the issue of feed gas separation. Moreover, there is no better way to improve the economic efficiency of the CCUS system for feed gas with low temperature. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems and provide a high-efficiency CCUS process that is simple in process, effectively recovers energy, effectively separates various recyclable gases into high value-added products, has good economic efficiency, and low equipment investment and operating costs.

[0007] The high-efficiency CCUS process of this invention includes the following steps:

[0008] a. The raw gas undergoes a CO2 capture process to capture and concentrate low-concentration CO2;

[0009] b. The concentrated raw gas is pressurized through a CO2 compression process;

[0010] c. The pressurized raw gas is purified by a CO2 purification process to remove harmful substances such as sulfur, nitrogen, and chlorine.

[0011] d. The purified CO2 mixture undergoes precise separation via a CO2 distillation process to separate O2, N2, CH4, CO, C2H4, C2H6, C3H6, C3H8, and C4H4 from the CO2 mixture. 10 Light hydrocarbons and other recyclable substances are separated from CO2.

[0012] In step a, the CO2 capture process is as follows: the raw gas is captured by a CO2 absorption tower and then analyzed by a desorption tower. The resulting raw gas has a CO2 concentration of more than 80% vol, a temperature of 25°C, and a pressure of 15 kPaG.

[0013] In step b, the CO2 compression process is as follows: the raw gas after the CO2 capture process enters the raw gas buffer tank, and after being stabilized by the raw gas buffer tank, it enters the CO2 compressor to be pressurized to 2.5-8 MPaG, and then is cooled to 40°C by the heat exchanger.

[0014] In step b, the raw gas pressurized by the CO2 compressor is sent to a heat exchanger to exchange heat indirectly with the heat carrier. The heat carrier after heat exchange serves as a heat source to heat the reboilers of each column in the CO2 distillation process. The heat carrier after cooling is returned to the heat exchanger for recycling.

[0015] In step c, the CO2 purification process involves the following steps: the raw gas after the CO2 compression process is sequentially fed into an oil remover for oil removal, into a COS hydrolyzer for organic sulfur removal, and into a desulfurization reactor for inorganic sulfur removal.

[0016] In step d, the CO2 distillation process is as follows: the purified feed gas is first sent to a CO2 liquefaction unit to cool the feed gas to -25°C and then enters a CO2 heavy removal tower. The bottom of the tower separates C3 and above components and sends them to a light hydrocarbon separation tower. The top of the tower separates a mixed gas containing CO2, N2, O2, CO, CH4, and H2 and sends it to a CO2 light removal tower.

[0017] The light hydrocarbon separation tower separates C3H6, C3H8, and C4H 10High-purity propylene, propane, and butane products can be obtained by collecting them from the top, middle, and bottom of the tower, respectively; liquid CO2 product is separated from the bottom of the CO2 light component removal tower, and a light component containing some CO2 is produced from the top of the tower.

[0018] In step d, the CO2 compressor is a single-stage or multi-stage compressor, and the driving method used is electric drive or steam turbine drive.

[0019] Beneficial effects:

[0020] 1. This invention integrates four processes: CO2 capture, CO2 compression, CO2 purification, and CO2 distillation. These processes sequentially capture, pressurize, purify, and separate CO2 from the feed gas, thereby removing harmful organic and inorganic substances such as sulfur, nitrogen, and chlorine from the CO2 gas. The separated O2 and N2 can be used as high-additional air separation products, and the separated CH4, CO, C2H4, C2H6, C3H6, C3H8, and C4H are also present. 10 Light hydrocarbons, as high value-added chemical products, have achieved economic benefits.

[0021] 2. By fully utilizing the characteristic of increased gas temperature after pressurization, the raw material gas exiting the compressor undergoes indirect heat exchange with the heat exchanger in the heat exchanger to recover heat energy. This heat source fully meets the heat load of the reboilers of each column in the distillation process, eliminating the need for energy consumption during the distillation separation process and greatly reducing the consumption of circulating water in the unit. This significantly improves product precision and quality while reducing the unit's energy consumption and operating costs.

[0022] 3. First, impurities are removed through a purification process, and then a three-tower combined distillation process is used to effectively separate a variety of recyclable gases as high value-added products. It has the advantages of simple process, effective energy recovery, good economy, and low equipment investment and operating costs. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention.

[0024] Among them, 1.1-CO2 absorption tower, 1.2-CO2 stripping tower; 2.1-raw material gas buffer tank; 2.2-CO2 compressor, 2.3-heat exchanger; 3.1-oil remover, 3.2-COS hydrolysis reactor, 3.3-desulfurization reactor; 4.1-CO2 liquefaction unit, 4.2-CO2 heavy hydrocarbon removal tower, 4.3-CO2 light hydrocarbon removal tower, 4.4-light hydrocarbon separation tower.

[0025] Specific implementation methods

[0026] The present invention will be further explained below with reference to the accompanying drawings:

[0027] In this embodiment, four processes are sequentially arranged along the direction of raw gas transportation: CO2 capture, CO2 compression, CO2 purification, and CO2 distillation.

[0028] In this embodiment, the CO2 feed gas has the following parameters: CO2 content is 37.39%, N2 content is 62.31%, and the remainder is light hydrocarbon components.

[0029] In the CO2 capture process, the CO2 feed gas is first captured by the CO2 absorption tower 1.1, and then analyzed by the CO2 desorption tower 1.2. The resulting feed gas has a CO2 temperature of 25℃, a pressure of 15 kPaG, and a flow rate of 253,000 Nm³. 3 / h. The specific composition of the captured feed gas is shown in Table 1.

[0030] Table 1. Specifications of Raw Gas

[0031] 1 <![CDATA[CO2]]> % vol 82.93 2 CO % vol 0.34 3 <![CDATA[H2]]> % vol 0.01 4 <![CDATA[N2]]> % vol 10.81 5 <![CDATA[CH4]]> % vol 1.76 6 <![CDATA[O2]]> % vol 0.73 7 <![CDATA[C2H4]]> % vol 0.29 8 <![CDATA[C2H6]]> % vol 1.5 9 <![CDATA[C3H8]]> % vol 0.94 10 <![CDATA[C3H6]]> % vol 0.23 11 <![CDATA[C4H 10 ]]> % vol 0.2 12 <![CDATA[H2S]]> ppmv ～24 13 COS ppmv ～40 14 <![CDATA[NH3]]> ppmv ～4 15 <![CDATA[CH3OH]]> ppmv ～168 16 <![CDATA[H2O]]> - Saturated

[0032] In the CO2 compression process, the feed gas after the CO2 capture process enters the feed gas buffer tank 2.1. After being pressurized in the feed gas buffer tank 2.1, it enters the CO2 compressor 2.2 and is pressurized to 2.5-8 MPaG. Then, it is sent to the heat exchanger 2.3 to indirectly exchange heat with the heat carrier and cool down to 40°C. The heat carrier after heat exchange serves as a heat source to heat the reboilers of each column in the CO2 distillation process. The cooled heat carrier is returned to the heat exchanger 2.3 for recycling. The heat carrier can be circulating water or heat transfer oil, etc. The heat energy of the pressurized feed gas is recovered through the heat exchanger 2.3, which also reduces the heat energy required for subsequent cooling of the purified gas.

[0033] The CO2 purification process is as follows: the raw gas after the CO2 compression process is sequentially fed into the oil remover 3.1 for oil removal, into the COS hydrolyzer 3.2 for organic sulfur removal, and into the desulfurization reactor 3.3 for inorganic sulfur removal to obtain purified gas.

[0034] The CO2 distillation process is as follows: the purified feed gas is first sent to the CO2 liquefaction unit 4.1 to cool the feed gas to -25°C and then enters the CO2 heavy hydrocarbon removal tower 4.2. The bottom of the tower separates C3 and higher components and sends them to the light hydrocarbon separation tower 4.3. The top of the tower separates a mixed gas containing CO2, N2, O2, CO, CH4 and H2 and sends it to the CO2 light hydrocarbon removal tower 4.4.

[0035] Light hydrocarbon separation tower 4.3 separates C3H6, C3H8, and C4H 10 High-purity propylene, propane, and butane products can be obtained by collecting samples from the top, middle, and bottom of the tower, respectively; liquid CO2 product is separated from the bottom of the CO2 removal tower 4.4, and a light component containing some CO2 is collected from the top of the tower.

[0036] By adopting the method of this embodiment, not only is the purity of CO2 products greatly improved (purity can reach food-grade carbon dioxide ≥99.9%), but also C3H6, C3H8, and C4H are reduced. 10 Products such as N2, O2, CO, CH4, and H2 are separated in stages. The heat source for the distillation separation is the heat generated during the compression of CO2. This not only greatly improves the economic efficiency of the products, but also reduces the amount of circulating water used in the unit, saving 845 m3 / h of circulating water and reducing the unit's energy consumption by 20704 kWh, thus achieving the invention's goal of cost reduction and efficiency improvement.

Claims

1. A high-efficiency CCUS process, characterized in that, Includes the following steps: a. The raw gas undergoes a CO2 capture process to capture and concentrate low-concentration CO2. The CO2 capture process is as follows: the raw gas is captured by a CO2 absorption tower and then analyzed by a desorption tower. The resulting raw gas has a CO2 concentration of over 80% vol, a temperature of 25°C, and a pressure of 15 kPaG. b. The concentrated feed gas is pressurized through a CO2 compression process. The CO2 compression process is as follows: the feed gas after the CO2 capture process enters the feed gas buffer tank. After the feed gas buffer tank is stabilized, it enters the CO2 compressor and is pressurized to 2.5~8MPaG. Then, it is cooled to 40°C by indirect heat exchange with the heat carrier through a heat exchanger. The heat carrier after heat exchange serves as a heat source to heat the reboilers of each column in the CO2 distillation process. The heat carrier after cooling is returned to the heat exchanger for recycling. c. The pressurized raw gas is purified by CO2 to remove sulfur, nitrogen and chlorine. The CO2 purification process is as follows: the raw gas after CO2 compression is sequentially fed into an oil separator for oil removal, into a COS hydrolyzer for organic sulfur removal, and into a desulfurization reactor for inorganic sulfur removal. d. The purified CO2 mixture undergoes precise separation via a CO2 distillation process. This process involves the purified feed gas first being fed into a CO2 liquefaction unit to cool it to -25°C before entering a CO2 heavy-weight removal tower. The bottom of the tower separates C3 and higher-order components, which are then sent to a light hydrocarbon separation tower. The top of the tower separates a mixture containing CO2, N2, O2, CO, CH4, and H2, which is then sent to a CO2 light-weight removal tower. The light hydrocarbon separation tower separates C3H6, C3H8, and C4H... 10 High-purity propylene, propane, and butane products can be obtained by collecting them from the top, middle, and bottom of the tower, respectively; liquid CO2 product is separated from the bottom of the CO2 light component removal tower, and a light component containing some CO2 is produced from the top of the tower.

2. The high-efficiency CCUS process as described in claim 1, characterized in that, In step b, the CO2 compressor is a single-stage or multi-stage compressor, and the driving method used is electric drive or steam turbine drive.

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