CN102327725B - A method for adsorption and capture of CO2 using steric hindrance effect - Google Patents

Abstract

The present invention provides a method for adsorption and capture of _CO2 using steric hindrance effect, which enables a stable adsorption capacity for medium-high temperature mixed gas from industrial emission sources, and exhibits good _CO2 selectivity relative to the remaining gases in the mixed gas adsorption. It is characterized in that: 3A zeolite molecular sieve with a pore diameter of about 0.3-0.34nm is used as the adsorbent, adopts pressure swing adsorption technology, and absorbs CO ₂ in the mixed gas through steric hindrance effect.

Description

A method for adsorption and capture of CO2 using steric hindrance effect

technical field

The invention relates to the technical field of _CO2 capture methods, in particular to a method for adsorption and capture of _CO2 using steric hindrance effect.

Background technique

In today's world, a large amount of CO ₂ emission makes the greenhouse effect more and more serious. Therefore, it is particularly necessary to adopt appropriate technology for CO ₂ separation and recovery for industrial emission sources with high CO ₂ concentration and high temperature.

In the prior art, the pressure swing adsorption process using physical adsorbents to capture CO ₂ has received extensive attention. 5A zeolite molecular sieves and 13X zeolite molecular sieves are widely used as adsorbents. Among them, 5A zeolite molecular sieves have the characteristic that the CO ₂ adsorption capacity in equilibrium adsorption varies with temperature. The characteristics of the increase and significantly decrease, its adsorption capacity is poor when used at high temperatures: for example, when the temperature rises to 175 ° C, the CO ₂ adsorption capacity of 5A zeolite molecular sieve is only 24% of 25 ° C; 13X zeolite molecular sieve is for When the mixed gas with low concentration of CO ₂ has a low amount of CO ₂ to be adsorbed, its ability to selectively adsorb CO ₂ is poor. Therefore, it is urgent to find an adsorbent that has a good adsorption capacity for _CO2 under medium and high temperature conditions, and exhibits specific _CO2 selective adsorption relative to the rest of the gas mixture, and to determine its performance under reasonable process conditions. Play the best way to adsorb and capture _CO2 .

Contents of the invention

In view of the above problems, the present invention provides a method for adsorption and capture of _CO2 using steric hindrance effect, which enables a stable adsorption capacity for medium and high temperature mixed gases from industrial emission sources, and exhibits good performance relative to the remaining gases in the mixed gas. _CO2 selective adsorption.

A method for adsorbing and capturing _CO2 using steric hindrance effect, the technical scheme of which is as follows:

It is characterized in that: 3A zeolite molecular sieve with a pore diameter of about 0.3-0.34nm is used as the adsorbent, adopts pressure swing adsorption technology, and absorbs CO ₂ in the mixed gas through steric hindrance effect.

It is further characterized in that: the adsorption temperature in the pressure swing adsorption technology is 80°C-300°C, and the adsorption pressure is 0.2MPa-1MPa;

It is further characterized by:

It includes at least two adsorption towers, and the adsorbent in the adsorption tower is a 3A zeolite molecular sieve with a pore size of about 0.3-0.34nm. When _CO2 is adsorbed, at least one of the adsorption towers participates in the adsorption and at least one of the adsorption towers participates in the desorption. The method steps of pressure adsorption technique are as follows:

a. Feed the raw material gas into the adsorption tower participating in the adsorption for adsorption. Adsorption temperature: 80°C-300°C, adsorption pressure: 0.2MPa-1MPa, adsorption time: 200 seconds to 300 seconds, and the gas after being adsorbed CO ₂ from The outlet of the adsorption tower flows out;

b. The adsorption of the adsorption tower participating in the adsorption and the desorption of the adsorption tower participating in the desorption are completed at the same time, and then a single adsorption tower that has completed desorption corresponds to a single adsorption tower that has completed adsorption. The pressure equalization time is 5 seconds to 10 seconds;

c After the pressure equalization is completed, the adsorption tower that has just been adsorbed is connected to the outside through the pipeline, and the desorption is performed by reducing the pressure. The desorption pressure: 0MPa～0.1MPa, _CO2 is discharged from the adsorption tower, and the 3A zeolite molecular sieve in the adsorption tower is regenerated. Its desorption time is the same as its adsorption time, and other adsorption towers are synchronously adsorbing at this time;

d The adsorption tower that has just been desorbed is pressurized for the first time through another adsorption tower that has completed the adsorption process at the same time, and then part of the product gas that has absorbed CO ₂ is introduced to pressurize the adsorption tower to the adsorption pressure: 0.2MPa～1MPa ;

After e, the adsorption tower that has been pressurized is cycled to carry out the above-mentioned work steps.

After adopting the method of the present invention, 3A zeolite molecular sieves with a pore diameter of about 0.3 to 0.34nm are loaded in the adsorption tower, and the molecular diameters of other gases except CO _in the feed gas are all greater than 0.34nm (the effective molecular diameter of _N2 is 0.364nm). nm, the effective molecular diameter of O ₂ is 0.346nm, and the effective molecular diameter of CH ₄ is 0.38nm), so N ₂ , O ₂ , CH ₄ and other gases are not easy to adsorb in the micropores of 3A zeolite molecular sieve. The gap between them passes through the adsorption layer, and the effective diameter of _CO2 is 0.33nm. It enters the micropores in the 3A zeolite molecular sieve with the kinetic energy of molecular motion and is adsorbed and captured. The method improves the selectivity of the adsorbent and increases the actual capture efficiency of the adsorbent. Taking the treatment of _CO2 and _N2 mixed gas with a _CO2 content of 10% as an example, the _CO2 effective adsorption capacity of the present invention is the commonly used 13X zeolite 5 times that of molecular sieves, and the concentration of CO ₂ in the desorbed gas is also over 95%, basically reaching the level of direct liquefaction, thereby realizing the efficient capture and utilization of CO ₂ gas. The invention has a stable equilibrium adsorption amount for the mixed gas of the industrial discharge source, and exhibits specific _CO2 selective adsorption relative to the rest of the gas in the mixed gas. However, in the prior art, 3A zeolite molecular sieves are only used to absorb moisture.

Description of drawings

Fig. 1 is a four-tower pressure swing adsorption process flow diagram of the present invention;

Fig. 2 is the composition of adsorption tower outlet gas in specific embodiment one;

Fig. 3 is the gas composition at the outlet of the adsorption tower in the specific embodiment 2.

Detailed ways

It includes at least two adsorption towers, and the adsorbent in the adsorption tower is a 3A zeolite molecular sieve with a pore size of about 0.3-0.34nm. When _CO2 is adsorbed, at least one of the adsorption towers participates in the adsorption and at least one of the adsorption towers participates in the desorption. The method steps of pressure adsorption technique are as follows:

a. Feed the raw material gas into the adsorption tower participating in the adsorption for adsorption. Adsorption temperature: 80°C-300°C, adsorption pressure: 0.2MPa-1MPa, adsorption time: 200 seconds to 300 seconds, and the gas after being adsorbed CO ₂ from The outlet of the adsorption tower flows out;

b. The adsorption of the adsorption tower participating in the adsorption and the desorption of the adsorption tower participating in the desorption are completed, and then a single adsorption tower that has completed desorption corresponds to a single adsorption tower that has completed adsorption. The pressure equalization time is 5 seconds to 20 seconds;

c After the pressure equalization is completed, the adsorption tower that has just been adsorbed is connected to the outside through the pipeline, and the desorption is performed by reducing the pressure. The desorption pressure: 0MPa～0.1MPa, _CO2 is discharged from the adsorption tower, and the 3A zeolite molecular sieve in the adsorption tower is regenerated. Its desorption time is the same as its adsorption time, and other adsorption towers are synchronously adsorbing at this time;

d The adsorption tower that has just desorbed is pressurized for the first time through another adsorption tower that has completed the adsorption process at the same time, and then the product gas from which CO ₂ has been removed is introduced to pressurize the adsorption tower to the adsorption pressure: 0.2MPa～1MPa ;

After e, the adsorption tower that has been pressurized is cycled to carry out the above-mentioned work steps.

Specific embodiment one:

The four-tower pressure swing adsorption is used to capture _CO2 from the flue gas of thermal power plants. The characteristics of the flue gas of thermal power plants are:

Large processing capacity: based on the daily power generation of 14.4 million kWh, the exhaust gas is about 532.4m ³ /s;

Higher temperature: the average temperature of the flue gas is 100°C, the flue gas temperature at the outlet of the suction fan after dust removal is 130°C, and the flue gas temperature at the chimney outlet is between 70-90°C;

The pressure is low; the flue gas outlet is generally at normal pressure, and the pressure is 0.1-0.15 MPa;

The composition is relatively complex and the concentration of CO ₂ is low. The flue gas composition is: 13% CO ₂ , 73% N ₂ , 10% H ₂ O, 3% O ₂ and less than 1% of various pollutants ;

After pre-dehydration and pressurization, four-tower pressure swing adsorption is used to capture CO ₂ , as shown in Figure 1, which includes adsorption tower 1, adsorption tower 2, adsorption tower 3, adsorption tower 4, and product gas tank 5. The 3A zeolite molecular sieve of about 0.3-0.34nm is loaded in the adsorption tower 1, the adsorption tower 2, the adsorption tower 3, and the adsorption tower 4. The whole adsorption and trapping process is described by the working cycle of the adsorption tower 1:

a When the adsorption starts, the adsorption temperature in the adsorption tower 1 is 80°C and the adsorption pressure is 0.2MPa. The raw material gas is passed into the adsorption tower ₁ for adsorption. The adsorption time is 200 seconds. The outlet of 1 flows out and passes into the product gas tank 5;

b After that, the adsorption tower 1 and the adsorption tower 2 that have completed the desorption are pressure equalized, and the pressure equalization time is 20 seconds;

c Then make the adsorption tower 1 connect to the outside through the lower desorption pipeline, reduce the pressure to normal pressure for desorption, _CO2 is discharged from the adsorption tower, and the 3A zeolite molecular sieve in the adsorption tower is regenerated, and the desorption time is 200 seconds;

After d, the adsorption tower 1 is pressurized for the first time by the adsorption tower 2 having completed the desorption, and then the product gas tank 5 feeds gas into the adsorption tower 1 to pressurize the adsorption tower to close to 0.2MPa;

After e, the adsorption tower 1 that has been pressurized is cycled to carry out the above-mentioned working steps.

After adsorption and capture, the final outlet CO ₂ accounts for less than 2% of the total volume (see Figure 2), the CO ₂ removal rate is higher than 85%, and its carbon capture efficiency is 5 times that of the commonly used 13X zeolite molecular sieve. The concentration of CO ₂ obtained after desorption is above 95%, which is convenient for further transportation and storage of CO ₂ .

Specific embodiment two:

The four-tower pressure swing adsorption is used to capture CO ₂ in the circulating gas of the coking plant. The main component of the circulating gas in the CDQ process of the coking plant is the inert gas N ₂ , containing 10-16% of CO ₂ and no more than 7% of CO 2 A small amount of CO. After the heat exchange between the circulating gas and the coke layer, it becomes a high-temperature flue gas at 900°C, and the next cycle is carried out after the first dust removal, waste heat exchange, and second dust removal. During the heat exchange, the _CO2 in the circulating gas will react with the red coke to generate CO, causing the coke to burn. The main conditions of the recycled gas to be processed are as follows: temperature at 160 °C, pressure at 0.1-0.12 MPa, CO ₂ %:N ₂ %:CO%=15:79:6.

Four-tower pressure swing adsorption is used to capture _CO2 , as shown in Figure 1, which includes adsorption tower 1, adsorption tower 2, adsorption tower 3, adsorption tower 4, product gas tank 5, and 3A zeolite with a pore size of about 0.3-0.34nm Molecular sieves are filled in adsorption tower 1, adsorption tower 2, adsorption tower 3, and adsorption tower 4. The entire adsorption and capture process is described with the working cycle of adsorption tower 1:

a When the adsorption starts, the adsorption temperature in the adsorption tower 1 is 160°C and the adsorption pressure is 0.4MPa. The raw material gas is passed into the adsorption tower ₁ for adsorption. The adsorption time is 300 seconds. The outlet of 1 flows out and passes into the product gas tank 5;

After b, the adsorption tower 1 and the adsorption tower 3 that has completed the desorption are pressure equalized, and the pressure equalization time is 5 seconds;

c Then the adsorption tower 1 is evacuated through the lower desorption pipeline, depressurized to 0MPa vacuum for desorption, CO _is discharged from the adsorption tower, and the 3A zeolite molecular sieve in the adsorption tower is regenerated, desorption time: 300 seconds;

After d, the adsorption tower 1 is pressurized for the first time by the adsorption tower 3 having completed the desorption, and then the product gas tank 5 feeds gas into the adsorption tower 1 to pressurize the adsorption tower to 0.4MPa;

After e, the adsorption tower 1 that has been pressurized is cycled to carry out the above-mentioned working steps.

The final outlet CO ₂ concentration is below 2% (see Figure 3), and the removal rate reaches 88.3%, which can greatly reduce the coke burning loss rate. The concentration of CO ₂ obtained after desorption is above 96%, which is convenient for further transportation and storage of CO ₂ .

Specific embodiment three:

Four-tower pressure swing adsorption is used to capture _CO2 from the coke oven gas of the coke oven. The coke oven gas is a mixture, and its yield and composition vary due to the quality of the coking coal and the coking process conditions. Its main components are hydrogen and methane, and it also contains a certain amount of carbon monoxide, carbon dioxide, nitrogen and so on. The main conditions of the treated coke oven gas are as follows: temperature at 300 °C, pressure at 0.1-0.12 MPa, main composition H ₂ : CH ₄ : CO: CO ₂ : N ₂ =55%: 25%: 8%: 10%: 2%.

Four-tower pressure swing adsorption is used to capture _CO2 , as shown in Figure 1, which includes adsorption tower 1, adsorption tower 2, adsorption tower 3, adsorption tower 4, product gas tank 5, and 3A zeolite with a pore size of about 0.3-0.34nm Molecular sieve layers are filled in adsorption tower 1, adsorption tower 2, adsorption tower 3, and adsorption tower 4. The entire adsorption and capture process is described with the working cycle of adsorption tower 1:

a When the adsorption starts, the adsorption temperature in the adsorption tower 1 is 300°C, and the adsorption pressure is 1 MPa. The raw material gas is passed into the adsorption tower ₁ for adsorption, and the adsorption time is 200 seconds. The outlet of the outlet flows out and passes into the product gas tank 5;

After b, the adsorption tower 1 and the adsorption tower 4 that has completed the desorption are pressure equalized, and the pressure equalization time is 10 seconds;

c Then make the adsorption tower 1 vacuumize through the lower desorption pipeline, reduce the pressure to 0.1MPa for desorption, _CO2 is discharged from the adsorption tower, and the 3A zeolite molecular sieve in the adsorption tower is regenerated, and the desorption time is 200 seconds;

After d, the adsorption tower 1 is pressurized for the first time by the adsorption tower 4 having completed the desorption, and then the product gas tank 5 feeds gas into the adsorption tower 1 to pressurize the adsorption tower to 1MPa;

After e, the adsorption tower cycle 1 that has been pressurized is carried out to the above-mentioned working steps.

Claims (1)

1. one kind is used steric effect adsorbing and trapping CO ₂Method, it is characterized in that: be adsorbent with the aperture at the 3A of 0.3～0.34nm zeolite molecular sieve, adopt pressure swing adsorption, by the CO in the steric effect absorption mist ₂Adsorption temp in the described pressure swing adsorption is at 80 ℃～300 ℃, and adsorptive pressure is at 0.2MPa～1MPa; It comprises at least two adsorption towers, and the adsorbent in the adsorption tower is that the aperture is in the 3A of 0.3～0.34nm zeolite molecular sieve, CO absorption ₂The time, wherein at least one adsorption tower participates in absorption, at least one adsorption tower participates in desorb, and the method step of described pressure swing adsorption is as follows:

Adsorb adsorption temp in a, the adsorption tower with unstripped gas feeding participation absorption: 80 ℃～300 ℃, adsorptive pressure: 0.2MPa～1MPa, adsorption time: 200 seconds～300 seconds, be adsorbed CO ₂After gas flow out from the outlet of this adsorption tower;

The desorb of the adsorption tower of the absorption of the adsorption tower of b, participation absorption and participation desorb is finished simultaneously, and the corresponding single adsorption tower of finishing that adsorbed of the adsorption tower that single desorb is afterwards finished is all pressed, and all the pressure time is 5 seconds～10 seconds;

C, all press finish after, the adsorption tower that absorption is just finished carries out desorb by step-down, desorption pressures: 0MPa～0.1MPa, CO by the pipeline connection outside ₂Be discharged from this adsorption tower, the 3A zeolite molecular sieve regeneration in this adsorption tower, its desorption time is identical with its adsorption time, and this moment, other adsorption tower adsorbed synchronously;

The adsorption tower that d, desorb are just finished carries out the pressurising first time by another adsorption tower of finishing adsorption process simultaneously, feeds then and is adsorbed CO ₂Product gas this adsorption tower is pressurized to adsorptive pressure: 0.2MPa～1MPa;

Above-mentioned job step is carried out in this adsorption tower circulation that e, pressurising are afterwards finished.

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