CN102389685B - Coal mine methane gas enriching method comprising step of pumping at exhaust end of adsorption tower - Google Patents

Abstract

The invention provides a method for increasing the concentration of exhaust air gas in coal mines enriched by vacuum pressure swing adsorption. It obtains the product gas from the desorption stage by means of vacuuming. In order to increase the volume fraction of methane gas in the product gas, gas is drawn from the exhaust end of the adsorption tower at the initial stage of vacuuming, and the extracted gas is returned to the raw gas. The adsorbent used in the adsorption tower in the present invention has selective adsorption capacity for methane and can be activated carbon, zeolite molecular sieve, and MOF. In the present invention, the adsorption pressure is controlled within 0.16 MPa, the methane in the coal mine exhaust gas can be enriched with low energy consumption, the utilization of the methane gas in the coal mine exhaust gas can be realized, and the emission of greenhouse gases can be reduced at the same time. The invention can also be used for the enrichment and concentration of gases rich in methane, carbon dioxide, carbon monoxide and other strong adsorption components.

Description

A coal mine exhaust air gas enrichment method with an exhaust end extraction step of an adsorption tower

technical field

The present invention belongs to pressure swing adsorption gas separation field, relate to a kind of method of vacuum pressure swing adsorption enrichment coal mine exhaust gas, can be used for the enrichment of strongly adsorbed component gases such as methane, carbon dioxide.

Background technique

Every year in China, more than 18 billion m ³ of pure methane is mixed into the mine air flow and evacuated through exhaust air, which is equivalent to more than 36 million tons of coal being wasted in vain. Moreover, methane is the second largest greenhouse gas next to CO ₂ , and the damage to the atmospheric environment caused by methane emissions has become a major environmental problem faced by the whole world. my country is a large coal country. According to statistics, the coalbed methane reserves within 2000m are 36 trillion cubic meters, accounting for 12.5% of the world's coalbed methane reserves, ranking third in the world. It emits 1/3 of the total amount of coalbed methane, ranking first in the world. The large amount of methane gas released into the atmosphere is mainly due to the low concentration of methane gas. Mine exhaust gas accounts for 80%-90% of the emitted methane gas, and its average concentration is about 0.25%. It is difficult to utilize such low-concentration gas. The current exhaust air gas oxidation device generally requires the methane concentration to be higher than 0.3% to maintain stable operation. When the methane concentration exceeds 0.5%, the gas oxidation device can be used for power generation. Lean-burn gas turbines can then be used to generate electricity. Therefore, it is of great significance to enrich and utilize the exhaust gas with low methane concentration.

Among all the gas separation methods, the pressure swing adsorption method has received extensive attention in the field of gas separation due to its advantages of small investment and low operating costs. In the adsorption separation process of recovery of heavy component gas, in order to ensure the recovery rate, the concentration of strongly adsorbed component gas in the exhaust gas is generally controlled, which will inevitably cause the mass transfer area to stay in the adsorption tower and affect the concentration of product gas. In the case of high adsorption pressure, the mass transfer area is generally moved out of the adsorption tower by the method of forward pressure reduction to increase the product gas concentration. For example, the patent CN85103557A enriches coal mine gas, and CN101422683A recovers carbon monoxide gas. However, when the adsorption pressure is low, forward depressurization cannot be achieved, or the magnitude of forward depressurization is relatively small.

Patents CN101503335A and CN101502740A disclose a multi-stage adsorption separation process for coal mine gas, methane is adsorbed as a heavy component gas, and high-concentration methane product gas is obtained by vacuum desorption. In the first-stage adsorption process, the concentration of methane in the exhaust gas is controlled to a relatively large value, so that the mass transfer area can be moved out of the adsorption tower, and the exhaust gas with a higher concentration enters another stage of adsorption separation device for separation. After separation, the obtained The gas is returned to the feed gas inlet for separation. Although such a flow process can increase the concentration under the condition of higher yield, the system is more complicated, and the investment in equipment has also been increased.

Contents of the invention

In order to increase the concentration of gas in the pressure swing adsorption separation process, the invention provides an adsorption separation method for pumping at the exhaust end of an adsorption tower. This method can increase the concentration of product gas methane.

The invention discloses a method for enriching exhaust air gas in coal mines with a pumping step at the exhaust end of an adsorption tower, and realizes the enrichment of low-concentration gas by means of vacuum pressure swing adsorption. In the vacuum pressure swing adsorption method, methane gas is a strong adsorption component, and product gas rich in methane is obtained in the decompression desorption process. In the method for increasing pressure swing adsorption and concentrating coal mine exhaust air gas concentration, part of the vacuumed gas is discharged. The adsorbent used in the pressure swing adsorption method is an adsorbent with selective adsorption capacity for methane, which may be zeolite molecular sieve, activated carbon, MOF (metal organic framework material) and the like.

The pressure swing adsorption separation device includes at least 2 adsorption towers, and can also be any adsorption tower with more than 2 towers. The process flow of the pressure swing adsorption method mainly includes six steps of pressure boosting, adsorption, pressure equalization drop, vacuum discharge, vacuum pumping, and pressure equalization increase. The parameters of the pressure swing adsorption process are as follows: the adsorption pressure is controlled within the absolute pressure of 0.1MPa-0.16MPa, and the step-down desorption pressure is controlled within the absolute pressure of 0.01MPa-0.08MPa. In the pressure swing adsorption process, after the pressure equalization drop is completed, a vacuum is drawn from the upper end of the adsorption tower to discharge part of the extracted gas. In this way, the gas with a relatively low volume fraction of methane flowing out in the initial stage of desorption can be prevented from entering the product gas, and the concentration of exhaust gas in coal mines enriched by vacuum pressure swing adsorption can be increased.

The system is mainly composed of the following parts: blower-1, intake buffer tank-2, first intake control valve-3A, second intake control valve-3B, first vacuum control valve-4A, second vacuum Control valve-4B, first adsorption tower-5A, second adsorption tower-5B, first discharge gas control valve-6A, second discharge gas control valve 6B, first pressure equalization control valve-7A, second pressure equalization control Valve-7B, first exhaust control valve-8, second exhaust control valve-13, third exhaust control valve-14, one-way valve-9, exhaust gas buffer tank-10, exhaust gas flow regulating valve- 11. Vacuum pump-12. The blower-1 is connected to the lower ends of the first adsorption tower-5A and the second adsorption tower-5B respectively through the first intake control valve-3A and the second intake control valve-3B through the intake buffer tank-2. -5A is connected to the vacuum pump-12 through the first pumping control valve-4A, and the second adsorption tower-5B is connected to the vacuum pump-12 through the second pumping control valve-4B. One end of the first adsorption tower-5A and the first exhaust control valve 8 are connected with the first pressure equalization control valve 7A and the second pressure equalization control valve 7B, and the other end is connected with a vacuum pump to realize the vacuuming step at the exhaust end of the adsorption tower. The second extraction control valve 13 is connected to the exhaust port of the vacuum pump and the inlet port of the blower, and is used to recover the methane gas in the exhaust gas. One end of the third extraction control valve 14 is connected to the vacuum pump, and the other end is used as the output end of the product gas; One end of the exhaust gas control valve 6A and the second exhaust gas control valve 6B are respectively connected to the upper ends of the first adsorption tower-5A and the second adsorption tower-5B, and the other end is connected to the exhaust gas buffer tank-10, discharge through the check valve-9 Air flow regulating valve -11 is connected.

The beneficial effects of the present invention are:

1) It can increase the volume fraction of the product gas methane in the enrichment of coal mine exhaust gas by vacuum pressure swing adsorption;

2) Enrich a certain gas in the mixed gas by pressure swing adsorption method, which has low initial investment, low operating cost, and flexible and convenient operation;

3) The present invention can make full use of low-concentration depleted gas and reduce environmental pollution caused by gas emissions, which has great economic and environmental significance.

4) The present invention can also be used to recover other gases containing strong adsorption components such as methane, carbon dioxide, and carbon monoxide.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a process flow diagram of the present invention;

Marked in the figure: blower-1, intake buffer tank-2, first intake control valve-3A, second intake control valve-3B, first pumping control valve-4A, second pumping control valve- 4B, the first adsorption tower-5A, the second adsorption tower-5B, the first discharge gas control valve-6A, the second discharge gas control valve-6B, the first pressure equalization control valve-7A, the second pressure equalization control valve- 7B, the first exhaust control valve-8, the second exhaust control valve-13, the third exhaust control valve-14, the one-way valve-9, the exhaust gas buffer tank-10, the exhaust gas flow regulating valve-11, Vacuum pump-12.

Detailed ways

Example: Concentrate exhaust gas with a methane volume fraction of 0.2% to more than 0.5%.

As shown in Figure 1, a method for enriching exhaust gas in coal mines with an extraction step at the exhaust end of the adsorption tower. The second intake control valve 3B flows into the first adsorption tower 5A and the second adsorption tower 5B. After the adsorbent in the first adsorption tower 5A and the second adsorption tower 5B absorbs the strong adsorption component methane and part of nitrogen and oxygen in the feed gas, the remaining mixed gas containing trace methane gas passes through the first discharge gas control valve 6A, The second exhaust gas control valve 6B flows out through the one-way valve-9 through the exhaust gas buffer tank-10 and the exhaust gas flow regulating valve-11. After the adsorption tower has undergone a pressure equalization drop, the product gas is extracted from the first adsorption tower 5A and the second adsorption tower 5B by the vacuum pump 12 through the first pumping control valve 4A and the second pumping control valve 4B. The pressure equalization process is realized through the first pressure equalization control valve 7A and the second pressure equalization control valve 7B. One end of the first exhaust control valve 8 is connected to the first pressure equalization control valve 7A and the second pressure equalization control valve 7B, and the other end is connected to a vacuum pump to realize the vacuuming step at the exhaust end of the adsorption tower. The second exhaust control valve 13 is connected to the exhaust end of the vacuum pump and the inlet end of the blower. The cycle time sequence is shown in Table 1, and the separation process will be described below taking the first adsorption tower 5A as an example.

(1) The raw material gas is pressurized by the blower 1, enters the first adsorption tower 5A through the intake buffer tank 2 and the first intake control valve 3A, and completes the pressurization step;

(2) After the pressurization is completed, the feed gas continues to enter the first adsorption tower 5A. At this time, the first exhaust control valve 6A is opened, methane is adsorbed during the gas flow, and the unadsorbed gas with a lower methane volume fraction passes through The first exhaust control valve 6A discharges;

(3) When methane penetrates through the first adsorption tower 5A, close the first exhaust control valve 6A, open the first pressure equalization control valve 7A and the second pressure equalization control valve 7B to equalize the pressure of the adsorption tower, at this time The pressure in the first adsorption tower 5A decreases, and the pressure in the second adsorption tower 5B increases;

(4) After completing the pressure equalization, close the second pressure equalization control valve 7B and the first intake control valve 3A, open the first exhaust control valve 8 to vacuum the first adsorption tower 5A, and the volume fraction of methane extracted at this time is relatively Lower, this part of the gas returns to the raw gas through the second pumping control valve 13;

(5) Close the first pumping control valve 8 and the second pumping control valve 13 after pumping, and open the first pumping control valve 4A and the third pumping control valve 14. At this time, the pumped gas contains relatively high methane Volume fraction of product gas;

(6) After vacuuming, close the first vacuum control valve 4A, open the first pressure equalization control valve 7A and the second pressure equalization control valve 7B, and equalize the pressure of the first adsorption tower 5A;

(7) Repeat steps (1)-(6).

This completes a cycle.

Table 1 Cyclic timing table

In this embodiment, the methane volume fraction of the exhaust gas is 0.2%. The adsorbent loaded in this embodiment is coconut shell activated carbon. The process parameters in this embodiment are as follows: the maximum adsorption pressure of the raw material gas is 150 kPa (absolute pressure) after boosting by the blower, and the minimum desorption pressure is 20 kPa (absolute pressure). In this embodiment, the volume fraction of methane in the product gas is greater than 0.5%.

Claims (2)

1. A coal mine exhaust air gas enrichment method with the extraction step at the exhaust end of the adsorption tower, which is characterized in that the enrichment of low-concentration gas is realized by vacuum pressure swing adsorption, and vacuum exhaust is introduced in the adsorption process The process step; in the vacuum pressure swing adsorption method, methane gas is a strong adsorption component, and the product gas rich in methane is obtained in the decompression desorption process, and the vacuumed gas in the vacuum pressure swing adsorption is partially discharged; the vacuum variable The adsorbent used in the pressure adsorption method is an adsorbent with selective adsorption capacity for methane, and the adsorbent is zeolite molecular sieve, activated carbon or metal organic framework material; Among them, the pressure swing adsorption separation device includes two adsorption towers; the process flow of the vacuum pressure swing adsorption method mainly includes six steps of boosting pressure, adsorption, pressure equalization drop, vacuum discharge, vacuum pumping, and pressure equalization rise; the vacuum The process parameters of pressure swing adsorption are as follows: the adsorption pressure is controlled within the absolute pressure of 0.1MPa～0.16MPa, and the step-down desorption pressure is controlled within the absolute pressure of 0.01MPa～0.08MPa. First use the vacuum pump to draw air from the exhaust end of the adsorption tower, and this part of the gas does not enter the product gas; the enrichment device used is composed of the following parts: blower (1), intake buffer tank (2), first intake control valve (3A), the second intake control valve (3B), the first pumping control valve (4A), the second pumping control valve (4B), the first adsorption tower (5A), the second adsorption tower (5B), The first discharge gas control valve (6A), the second discharge gas control valve (6B), the first pressure equalization control valve (7A), the second pressure equalization control valve (7B), the first extraction control valve (8), Second exhaust control valve (13), third exhaust control valve (14), one-way valve (9), exhaust gas buffer tank (10), exhaust gas flow regulating valve (11), vacuum pump (12); blower (1) Through the intake buffer tank (2), the first intake control valve (3A) and the second intake control valve (3B) are respectively connected to the lower ends of the first adsorption tower (5A) and the second adsorption tower (5B) ; The first adsorption tower (5A) links to each other with the vacuum pump (12) by the first evacuation control valve (4A), and the second adsorption tower (5B) links to each other with the vacuum pump (12) by the second evacuation control valve (4B); An adsorption tower (5A), one end of the first exhaust control valve (8) is connected with the first pressure equalization control valve (7A) and the second pressure equalization control valve (7B), and the other end is connected with the vacuum pump (12) to realize adsorption The vacuuming step at the exhaust end of the tower; the second exhaust control valve (13) is connected to the exhaust end of the vacuum pump and the inlet end of the blower; one end of the third exhaust control valve (14) is connected to the vacuum pump, and the other end is used as the output end of the product gas; One end of the first exhaust gas control valve (6A) and the second exhaust gas control valve (6B) are respectively connected to the upper ends of the first adsorption tower (5A) and the second adsorption tower (5B), and the other end is connected to the upper end of the first adsorption tower (5A) and the second adsorption tower (5B) through the check valve (9). The discharge gas buffer tank (10) is connected to the discharge gas flow regulating valve (11). 2. A method for enriching coal mine exhaust gas gas with an extraction step at the exhaust end of an adsorption tower according to claim 1, characterized in that: the methane volume fraction of the coal mine exhaust gas gas is 0.2%; the adsorbent Coconut shell activated carbon is used; the highest adsorption pressure is 150kPa absolute pressure, and the lowest decompression desorption pressure is 20kPa absolute pressure; the finally obtained product gas methane volume fraction is greater than 0.5%.

Images