Method for separating and capturing carbon dioxide in flue gas

Abstract

The invention discloses a method for separating and capturing carbon dioxide in flue gas, comprising the following steps: pre-treating the flue gas discharged from a factory; subjecting the pre-treated flue gas to a first CO2 gas separation through a gas separation membrane; and after the first separation, passing the flue gas into a solid-liquid two-phase absorbent for a second CO2 gas separation. The invention combines a membrane separation method with an adsorption method, firstly utilizing a hollow fiber membrane with good CO2 selectivity to preliminarily increase the concentration of CO2 gas in the flue gas, and then passing the concentrated gas into a solid-liquid two-phase absorbent, thereby solving the problem of low efficiency in the CO2 separation and capture process; utilizing the solid-liquid two-phase absorbent to process the gas treated by the membrane separator, thereby reducing the loss of the gas separation membrane and increasing the life of the membrane for repeated use; the solid-liquid two-phase absorbent greatly increases the absorption efficiency of carbon dioxide for convenient recycling, and at the same time, the solid can be reused after being heated, thereby greatly reducing the production cost.

Description

Technical Field

[0001] The present invention specifically relates to a method for separating and capturing carbon dioxide. Background Art

[0002] With the development of human society and industry, greenhouse gas CO2 emissions have reached 14,000 MtCO2 / year, causing the concentration of CO2 in the atmosphere to increase year by year. As an industrial power, China is in a period of vigorous development, which is accompanied by huge resource consumption. my country mainly produces CO2 in high-energy-consuming industries, including metallurgy, cement, thermal power and other industrial sectors, which has caused a series of climate and environmental problems. Therefore, it is particularly urgent to separate flue gas and capture, seal and utilize CO2 as resources to reduce its emissions. However, the flue gas emitted by factories in my country currently generally has the disadvantages of high exhaust temperature, large exhaust volume and low CO2 concentration (generally <15%). This also leads to high investment and operation and maintenance costs in the actual application of this method, which to a certain extent restricts the industrialization process.

[0003] In order to solve this problem, the main methods currently used for CO2 capture include chemical solvent absorption, physical solvent absorption, low-temperature distillation, membrane separation, etc. Publication No. CN202022770649.5 proposes a nitrogen-free gas-fired glass furnace oxygen + CO2 circulating combustion system and device, which recovers CO2 in the tail gas of the glass furnace through a circulating flue gas CO2 recovery device, and uses it as oxygen-rich gas distribution to improve the formation of oxygen-rich gas as a combustion aid for the glass furnace, thereby improving the utilization of carbon resources in the flue gas; CN202111323337.2 proposes a method for purifying sintering flue gas and solidifying CO2 using LF refining waste residue, pouring the LF refining waste residue into a soaking pool for stirring and soaking, leaching free calcium oxide and forming a saturated solution of Ca(OH)2, which is mixed with the flue gas to react and fix the CO2 gas.

[0004] However, the existing technology is not efficient in separating and capturing CO2 gas in flue gas, and its separation and capture efficiency needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the separation and capture efficiency of carbon dioxide in flue gas, combining membrane separation method with adsorption method, the former for coarse separation and the latter for fine separation, to further achieve efficient separation and capture of CO2 gas.

[0006] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0007] A method for separating and capturing carbon dioxide in flue gas comprises the following steps:

[0008] (1) Pre-treat the flue gas emitted by the factory;

[0009] (2) passing the pretreated flue gas through a gas separation membrane for the first CO2 gas separation;

[0010] (3) After the first separation, the flue gas is passed into a solid-liquid two-phase absorbent for a second CO2 gas separation.

[0011] According to the above scheme, the solid-liquid two-phase absorbent is prepared by dissolving a liquid absorbent in a solvent and then mixing it with a solid adsorbent.

[0012] According to the above scheme, the liquid absorbent is any one of 3-methylaminopropylamine, triethylenetetramine, anhydrous piperazine, ethylenediamine, diethylenetriamine, and diethylaminopropylamine, or a mixture thereof; and the solid adsorbent is activated carbon fiber.

[0013] According to the above scheme, the solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, methanol and ethanol.

[0014] According to the above scheme, the concentration of liquid adsorbent in the solid-liquid two-phase absorbent is 0.1-0.5 mol / L, and the content of solid adsorbent is 5-12 wt%.

[0015] According to the above scheme, the CO2 concentration in the flue gas is 20-60%, the N2 concentration is 10-40%, the H2O concentration is 5-15%, and the O2 concentration is 0-10% by volume.

[0016] According to the above scheme, the flue gas in step 1 is pre-treated including dust removal, condensation, and filtration; the temperature after passing through the condenser is lower than 35°C.

[0017] According to the above scheme, the gas separation membrane in step 2 is a hollow fiber membrane, and the membrane material type is any one of polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, silicone rubber, polyethersulfone, and cellulose acetate.

[0018] According to the above scheme, the concentration of CO2 gas in the flue gas after the first separation in step 2 is increased to 50-70 mol%.

[0019] According to the above scheme, the separation process in step 3 is completed in a glass bubble tower reactor, and the temperature is maintained at 40-80°C.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention combines membrane separation with adsorption. First, a hollow fiber membrane with good CO2 selectivity is used to preliminarily increase the concentration of CO2 gas in the flue gas. Then, the concentrated gas is passed into a solid-liquid two-phase absorbent, thereby solving the problem of low efficiency in the CO2 separation and capture process.

[0022] The gas treated by the membrane separator is treated with a solid-liquid two-phase absorbent, which reduces the loss of the gas separation membrane and increases the life of the membrane for repeated use.

[0023] In addition, the solid-liquid two-phase absorbent used in the present invention greatly increases the absorption efficiency of carbon dioxide, which is convenient for recycling. At the same time, the solid can be reused after being heated, which greatly reduces the production cost. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below, and it should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not intended to limit the present invention. The endpoints and any values ​​of the scope disclosed in this article are not limited to the accurate scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article.

[0025] In a specific embodiment, the solid-liquid two-phase absorbent used for separating and capturing carbon dioxide is prepared by dissolving a liquid absorbent in a solvent and adding a solid adsorbent, the concentration of the liquid absorbent is 0.1-0.5 mol / L, and the content of the solid adsorbent is 5-12 wt%; the absorbent is any one of 3-methylaminopropylamine, triethylenetetramine, anhydrous piperazine, ethylenediamine, diethylenetriamine, diethylaminopropylamine or a mixture thereof; the solid adsorbent is activated carbon fiber; the solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, and ethanol.

[0026] The prepared solid-liquid two-phase absorbent has greatly increased absorption efficiency of carbon dioxide, which is convenient for recycling. At the same time, the solid can be reused after being heated, which greatly reduces production costs.

[0027] A method for improving the separation and capture efficiency of carbon dioxide in flue gas is provided in a specific embodiment, as follows:

[0028] (1) Pre-treat the flue gas discharged from the factory; the pre-treatment includes dust removal, condensation, and filtration; the temperature after passing through the condenser is lower than 35°C;

[0029] (2) passing the pretreated flue gas through a gas separation membrane to perform a first CO2 gas separation; the concentration of CO2 gas in the flue gas after the first separation is increased to 50 to 70 mol%;

[0030] (3) After the first separation, the flue gas is passed into a solid-liquid two-phase absorbent for a second CO2 gas separation.

[0031] Combining membrane separation with adsorption, firstly using a hollow fiber membrane with good CO2 selectivity to initially increase the concentration of CO2 in flue gas, and then passing the concentrated gas into a solid-liquid two-phase absorbent, solving the problem of low efficiency in the CO2 separation and capture process. Using a solid-liquid two-phase absorbent to treat the gas treated by the membrane separator reduces the loss of the gas separation membrane and also increases the life of the membrane for repeated use.

[0032] The flue gas used in the specific embodiment has a CO2 concentration of 20-60%, a N2 concentration of 10-40%, a H2O concentration of 5-15%, and an O2 concentration of 0-10% by volume.

[0033] In the optimized solution, the gas separation membrane in step 2 adopts a hollow fiber membrane, and the membrane material type is any one of polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, silicone rubber, polyethersulfone, and cellulose acetate.

[0034] In the optimized scheme, the separation process of step 3 is completed in a glass bubble tower reactor, and the temperature is maintained at 40-80°C.

[0035] Example 1

[0036] (1) Preparation of solid-liquid two-phase absorbent: Weigh a certain mass of liquid absorbent (3-methylaminopropylamine and ethylenediamine in a mass ratio of 1:1) and solvent (N,N-dimethylformamide) on an electronic balance, place the drugs in a beaker, and use a magnetic stirrer to dissolve them to prepare a liquid absorbent with a concentration of 0.2 mol / L. Then weigh 8 wt% of activated carbon fiber and add it to the liquid absorbent and continue stirring; the stirring time for both times is 12 h, and the stirring rate is 300 r / min.

[0037] (2) Flue gas pretreatment: The flue gas discharged from the factory is first passed through a dust collector to filter out large and fine dust particles. After dust removal, the mixed gas is cooled to 30°C by a condenser and then stored in a gas storage tank.

[0038] (3) Membrane separation treatment: The pretreated mixed gas is initially separated through a hollow fiber membrane made of polysulfone material, so that the CO2 concentration in the mixed gas reaches more than 60 mol%, and is stored in a gas storage tank.

[0039] (4) Adsorption treatment: The adsorption process was completed in a glass bubble tower reactor, the temperature was maintained at 50°C, and the mixed gas after membrane separation was controlled by a gas flow meter to pass into the solid-liquid two-phase absorbent at a flow rate of 150 mL / min.

[0040] (5) During the absorption process, the weight gain of the reactor is measured every 5 minutes using an electronic balance, which is the amount of CO2 absorbed. The maximum absorption rate of CO2 gas by the solid-liquid two-phase absorbent is calculated.

[0041] After testing, the absorbent's absorption capacity for CO2 gas is 12.4 mg / g, and the maximum absorption rate is 0.97 mg / min.

[0042] Example 2

[0043] (1) Preparation of solid-liquid two-phase absorbent: Weigh a certain mass of absorbent (the mass ratio of 3-methylaminopropylamine to triethylenetetramine is 1:1) and solvent (ethanol) drugs on an electronic balance, place the drugs in a beaker, and use a magnetic stirrer to dissolve them to prepare a liquid absorbent with a concentration of 0.3 mol / L. Then weigh 10% of activated carbon fiber and add it to the liquid absorbent and continue stirring; the stirring time for both times is 12 h, and the stirring rate is 300 r / min.

[0044] (2) Flue gas pretreatment: The flue gas discharged from the factory is first passed through a dust collector to filter out large and fine dust particles. After dust removal, the mixed gas is cooled to 50°C by a condenser and then stored in a gas storage tank.

[0045] (3) Membrane separation treatment: The pretreated mixed gas is initially separated through a hollow fiber membrane made of polyethersulfone material, so that the CO2 concentration in the mixed gas reaches more than 60 mol% and is stored in a gas storage tank.

[0046] (4) Adsorption treatment: The adsorption process was completed in a glass bubble tower reactor, the temperature was maintained at 60°C, and the mixed gas after membrane separation was controlled by a gas flow meter to pass into the solid-liquid two-phase absorbent at a flow rate of 150 mL / min.

[0047] (5) During the absorption process, the weight gain of the reactor is measured every 5 minutes using an electronic balance, which is the amount of CO2 absorbed. The maximum absorption rate of CO2 gas by the solid-liquid two-phase absorbent is calculated.

[0048] After testing, the absorbent's absorption capacity for CO2 gas is 15.4 mg / g, and the maximum absorption rate is 1.06 mg CO2 / min.

[0049] Example 3

[0050] (1) Preparation of solid-liquid two-phase absorbent: Weigh a certain mass of absorbent (3-methylaminopropylamine and diethylaminopropylamine in a mass ratio of 1:1) and solvent (N,N-dimethylformamide) on an electronic balance, place the drugs in a beaker, and use a magnetic stirrer to dissolve them to prepare a liquid absorbent with a concentration of 0.4 mol / L. Then weigh 12% of activated carbon fiber and add it to the liquid absorbent and continue stirring; the stirring time for both times is 12 h, and the stirring rate is 300 r / min.

[0051] (2) Flue gas pretreatment: The flue gas discharged from the factory is first passed through a dust collector to filter out large and fine dust particles. After dust removal, the mixed gas is cooled to 50°C by a condenser and then stored in a gas storage tank.

[0052] (3) Membrane separation treatment: The pretreated mixed gas is initially separated through a hollow fiber membrane made of polysulfone material, so that the CO2 concentration in the mixed gas reaches more than 60 mol% and is stored in a gas storage tank.

[0053] (4) Adsorption treatment: The adsorption process was completed in a glass bubble tower reactor, the temperature was maintained at 60°C, and the mixed gas after membrane separation was controlled by a gas flow meter to pass into the solid-liquid two-phase absorbent at a flow rate of 150 mL / min.

[0054] (5) During the absorption process, the weight gain of the reactor is measured every 5 minutes using an electronic balance, which is the amount of CO2 absorbed. The maximum absorption rate of CO2 gas by the solid-liquid two-phase absorbent is calculated.

[0055] After testing, the absorbent's absorption capacity for CO2 gas is 13.7 mg / g, and the maximum absorption rate is 1.05 mg CO2 / min.

[0056] Example 4

[0057] (1) Preparation of solid-liquid two-phase absorbent: Weigh a certain mass of absorbent (3-methylaminopropylamine) and solvent (N,N-dimethylformamide) on an electronic balance, place the drugs in a beaker, and use a magnetic stirrer to dissolve them to prepare a liquid absorbent with a concentration of 0.2 mol / L. Then weigh 5% of activated carbon fiber and add it to the liquid absorbent and continue stirring; the stirring time for both times is 12 h, and the stirring rate is 300 r / min.

[0058] (2) Flue gas pretreatment: The flue gas discharged from the factory is first passed through a dust collector to filter out large and fine dust particles. After dust removal, the mixed gas is cooled to 50°C by a condenser and then stored in a gas storage tank.

[0059] (3) Membrane separation treatment: The pretreated mixed gas is initially separated through a hollow fiber membrane made of polyethersulfone material, so that the CO2 concentration in the mixed gas reaches more than 60 mol% and is stored in a gas storage tank.

[0060] (4) Adsorption treatment: The adsorption process was completed in a glass bubble tower reactor, the temperature was maintained at 60°C, and the mixed gas after membrane separation was controlled by a gas flow meter to pass into the solid-liquid two-phase absorbent at a flow rate of 150 mL / min.

[0061] (5) During the absorption process, the weight gain of the reactor is measured every 5 minutes using an electronic balance, which is the amount of CO2 absorbed. The maximum absorption rate of CO2 gas by the solid-liquid two-phase absorbent is calculated.

[0062] (6) Recycling of solid-liquid two-phase absorbent: The solid adsorbent in the solid-liquid two-phase absorbent treated by adsorption in step (4) is filtered out and heated at 200°C to desorb the adsorbed CO2 gas. After cooling to room temperature, steps (1) to (5) are repeated.

[0063] After testing, the absorption capacity of the first absorbent for CO2 gas is 14.8mg / g, and the maximum absorption rate is 0.98mgCO2 / min; the absorption capacity of the second absorbent for CO2 gas is 14.6mg / g, and the maximum absorption rate is 0.96mgCO2 / min.

[0064] Example 5

[0065] (1) Preparation of solid-liquid two-phase absorbent: Weigh a certain mass of absorbent (diethylaminopropylamine) and solvent (methanol) on an electronic balance, place the drugs in a beaker, and use a magnetic stirrer to dissolve them to prepare a liquid absorbent with a concentration of 0.3 mol / L. Then weigh 8% activated carbon fiber and add it to the liquid absorbent and continue stirring; the stirring time for both times is 12 h, and the stirring rate is 300 r / min.

[0066] (2) Flue gas pretreatment: The flue gas discharged from the factory is first passed through a dust collector to filter out large and fine dust particles. After dust removal, the mixed gas is cooled to 50°C by a condenser and then stored in a gas storage tank.

[0067] (3) Membrane separation treatment: The pretreated mixed gas is initially separated through a hollow fiber membrane made of polysulfone material, so that the CO2 concentration in the mixed gas reaches more than 60 mol% and is stored in a gas storage tank.

[0068] (4) Adsorption treatment: The adsorption process was completed in a glass bubble tower reactor, the temperature was maintained at 60°C, and the mixed gas after membrane separation was controlled by a gas flow meter to pass into the solid-liquid two-phase absorbent at a flow rate of 150 mL / min.

[0069] (5) During the absorption process, the weight gain of the reactor is measured every 5 minutes using an electronic balance, which is the amount of CO2 absorbed. The maximum absorption rate of CO2 gas by the solid-liquid two-phase absorbent is calculated.

[0070] (6) Recycling of solid-liquid two-phase absorbent: The solid adsorbent in the solid-liquid two-phase absorbent treated by adsorption in step (4) is filtered out and heated at 200°C to desorb the adsorbed CO2 gas. After cooling to room temperature, steps (1) to (5) are repeated.

[0071] After testing, the absorption capacity of the first absorbent for CO2 gas is 13.6mg / g, and the maximum absorption rate is 1.05mgCO2 / min; the absorption capacity of the second absorbent for CO2 gas is 13.4mg / g, and the maximum absorption rate is 0.96mgCO2 / min.

Claims

1. A method for separating and capturing carbon dioxide from flue gas, characterized in that The following steps are involved: (1) Pre-treatment of flue gas emitted by factories; (2) Passing the pretreated flue gas through a gas separation membrane for the first CO2 gas separation; (3) After the first separation, the flue gas is passed into a solid-liquid two-phase absorbent for a second CO2 gas separation; the separation process is completed in a glass bubble tower reactor with the temperature maintained at 40-80°C; The solid-liquid two-phase absorbent is prepared by dissolving a liquid absorbent in a solvent and then mixing it with a solid adsorbent; the liquid absorbent is a mixture of 3-methylaminopropylamine and triethylenetetramine in a mass ratio of 1:1; the solid adsorbent is activated carbon fiber; the solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, and ethanol; The liquid absorbent concentration in the solid-liquid two-phase absorbent is 0.1-0.5 mol / L, and the solid adsorbent content is 5-12 wt %.

2. The method for separating and capturing carbon dioxide in flue gas according to claim 1, characterized in that In step 1, the flue gas is pre-treated including dust removal, condensation, and filtration; the temperature after passing through the condenser is lower than 35°C.

3. The method for separating and capturing carbon dioxide in flue gas according to claim 1, characterized in that The gas separation membrane in step 2 is a hollow fiber membrane, and the membrane material type is any one of polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, silicone rubber, polyethersulfone, and cellulose acetate.