CN201377962Y - Equipment for producing compressed natural gas from mixed gas containing methane - Google Patents

Abstract

The utility model discloses an equipment of preparing Compressed Natural Gas (CNG) from containing methane gas mixture, it includes refrigerating plant, contain methane gas mixture separator, cryogenic fluid pump and high pressure heat exchanger, contain methane gas mixture and get into refrigerating plant in proper order and become Liquefied Natural Gas (LNG) behind the methane gas mixture separator, then it pressurizes to go into cryogenic fluid pump, become high-pressure LNG, high-pressure LNG gets into and just directly becomes the CNG product after the gasification of high pressure heat exchanger rewarming, can supply to store and fill dress usefulness, the complicated device of cooling into CNG with the compressor with low pressure natural gas compression has been saved. The purity of the CNG product obtained by using the equipment can reach more than 99.8 percent, and the whole equipment is simple and convenient to operate.

Description

Equipment for producing compressed natural gas from mixed gas containing methane

technical field

The utility model relates to separation equipment especially used for the mixed gas containing methane.

Background technique

CNG (Compressed Natural Gas) is natural gas pressurized (generally over 16MPa) and stored in a gaseous form in a pressure vessel. CNG can be used as vehicle fuel. Among various alternative fuels for automobiles, natural gas is an ideal clean fuel for automobiles, which has advantages in resources, environmental protection, economy and safety. At present, CNG vehicles account for the largest proportion of natural gas vehicles in the world, and its technology is also the most mature, with good environmental and economic benefits. In addition, CNG can also be used for peak shaving of natural gas. The use of CNG peak shaving is very stable during the peak of gas consumption, and the pressure of the pipeline network can be guaranteed. Due to the fact that in the process of industrial production and energy exploitation in my country, a huge amount of mixed gas containing methane will be produced, such as coke oven gas, gas (oxygen-containing coalbed methane), etc., most of which are discharged as "waste gas" or directly burned. Take coke oven gas as an example, at least two "west-to-east gas pipelines" are burned in my country every year. If usable components such as methane are extracted from these "waste gases" and utilized, it can effectively solve the dual problems of energy supply security and ecological environment protection, and play an important role in achieving sustainable economic and social development.

Chinese patent ZL200620115881.2 discloses a liquefaction equipment for air-containing coalbed methane, including compression and purification equipment, refrigeration equipment and liquefaction separation equipment. The compression and purification equipment performs dust removal, compression, dehydration, etc. The liquefaction separation equipment fractionates the liquefied natural gas. It can produce liquefied natural gas from coalbed methane, but cannot directly produce CNG.

Utility model content

The purpose of the utility model is to provide a separation device, which can directly produce CNG from the mixed gas containing methane.

In order to achieve the above object, the basic idea of the utility model is to adopt the method of low-temperature liquefaction and rectification to liquefy and separate methane from the mixed gas containing methane, and then use a low-temperature liquid pump to pressurize the liquefied natural gas (LNG) to 6-6 Above 30MPa, it becomes a high-pressure liquid. After reheating, the high-pressure liquid becomes a high-pressure gas, that is, a CNG product, which is stored in a high-pressure container for use.

As a technical solution to realize the basic idea of the present invention, a device for producing compressed natural gas from methane-containing mixed gas is provided, including: a refrigeration device, and the methane-containing mixed gas is cooled in the refrigeration device to generate a gas-liquid mixture ; A methane-containing mixed gas separation device comprising a fractionation tower, which is used for separating liquefied natural gas from the gas-liquid mixture, and has an inlet for inputting the gas-liquid mixture, and a top gas outlet and for discharging liquefied natural gas The bottom liquid outlet of natural gas; the equipment for producing compressed natural gas also includes a low-temperature liquid pump having an outlet and an inlet connected to the bottom liquid outlet of the fractionation tower, and a high-pressure heat exchanger, and the low-temperature liquid pump will come from the The liquefied natural gas in the fractionation tower is sent to the high-pressure heat exchanger under pressure.

As another preferred solution of the above technical solution, it also includes a reboiler arranged between the bottom liquid outlet of the fractionation tower and the inlet of the cryogenic liquid pump, for heating the liquefied natural gas flowing into it, so as to improve the liquefied natural gas purity.

As yet another preferred solution of the above technical solution, it further includes a subcooler arranged between the outlet of the reboiler and the inlet of the cryogenic liquid pump for cooling the liquefied natural gas flowing therein.

As yet another preferred solution of the above technical solution, it also includes a condenser arranged between the top gas outlet of the fractionation tower and the subcooler for condensing the mixed gas containing methane flowing into it.

As yet another preferred solution of the above technical solution, the refrigerating device includes a gas expansion refrigerating device or a mixed working medium refrigerating device, wherein the gas expanding refrigerating device includes a heat exchanger.

As yet another preferred solution of the above technical solution, the exhaust gas from the subcooler passes through the heat exchanger of the refrigeration device to provide cooling capacity for the heat exchanger.

As yet another preferred solution of the above technical solution, the high-pressure heat exchanger is communicated with the mixed gas containing methane to provide hot fluid for the high-pressure heat exchanger.

As yet another preferred solution of the above technical solution, the high-pressure heat exchanger is connected with the refrigerant gas to provide hot fluid for the high-pressure heat exchanger.

The beneficial effects obtained by the utility model are: the method of low-temperature liquefaction separation is adopted to separate the methane from the methane-containing mixed gas, and then pressurized by a cryogenic pump to become high-pressure LNG; As a CNG product, it can be used for storage and filling, eliminating the need for complex devices that use compressors to compress and cool low-pressure natural gas into CNG. The purity of the CNG product obtained by using this equipment can reach more than 99.8%. The whole set of equipment is simple and easy to operate.

Description of drawings

The utility model is described in further detail below in conjunction with accompanying drawing and specific embodiment.

Fig. 1 is a schematic flow chart of producing CNG in the embodiment of the utility model.

Detailed ways

The equipment of the utility model mainly includes a refrigerating device, a raw material gas (that is, a mixed gas containing methane) separation device, an LNG booster device and a high-pressure heat exchanger. The refrigerating device includes two types of gas (nitrogen or nitrogen-methane mixed gas) expansion refrigerating device and a mixed working medium refrigerating device, wherein the gas expansion refrigerating device is simple in operation, low in investment, and moderate in energy consumption, and mainly includes a refrigerating gas compressor, multi-channel Heat exchangers, high-pressure heat exchangers, booster turbo expanders and other unit equipment; mixed working medium refrigeration devices are simple to operate, low in energy consumption, and moderate in investment, mainly including mixed working medium compressors, gas-liquid separators, multi-channel exchangers, etc. Heater, high pressure heat exchanger, low temperature throttle valve and other unit equipment. The methane-containing mixed gas separation device mainly includes a fractionation tower, a fractionation tower bottom reboiler, and a tower top condenser can also be selected according to actual conditions. The LNG pressurization equipment is a special cryogenic liquid pump, which pressurizes the LNG to above 6-30Mpa as required.

In the utility model, the methane-containing mixed gas is a mixed gas with a methane content (volume percentage) between 10% and 95%. If the mixed gas beyond this range is used in this equipment, the economy is not good, or it is not suitable for this equipment.

The mixed gas containing methane in the utility model is clean gas after purification treatment and is suitable for low temperature environment. The purification process includes dehydration, CO ₂ removal, desulfurization, mercury removal, benzene and aromatic hydrocarbon removal, naphthalene removal and removal of other high-boiling impurity components, etc.

In this embodiment, the refrigerating device adopts a gas expansion refrigerating device to liquefy and separate the mixed gas containing methane. The process flow is as follows:

Refer to the flow diagram of compressed natural gas CNG produced by the gas expansion refrigeration cycle in Figure 1. The purified methane-containing mixed gas A enters heat exchangers 1 and 2 in turn to exchange heat, is cooled by cold fluid, and the temperature decreases step by step. 2, the methane in the methane-containing mixture has basically become liquid. Then enter the fractionation tower 3, the liquid flows from top to bottom, and the gas flows from bottom to top. The lower you go, the more methane there is in the liquid, and the higher you go, the lower the methane in the gas. After the liquid flows to the bottom of the tower, it enters the reboiler 5 at the bottom of the tower, and a small amount of low-boiling components in the liquid (related to the raw material gas components, such as _O2 , _N2 , CO, H2 _, etc.) are heated and further flashed The purity of the liquefied natural gas (LNG) coming out of the fractionation tower is further improved, which can reach more than 99.8%. Then it enters the subcooler 6 and is further cooled by the gas coming out of the top of the tower to become subcooled liquefied natural gas LNG. The supercooled liquefied natural gas LNG enters the cryogenic liquid pump 7 and is pressurized to above 6 to 30 MPa. The high-pressure liquefied natural gas enters the high-pressure heat exchanger 8, exchanges heat with the hot fluid, and becomes high-pressure gas, that is, the compressed natural gas CNG product, which is stored after leaving the system. Exhaust gas B reheated from subcooler 6 enters heat exchangers 2 and 1 in turn to provide cooling capacity for the system, and finally exits the system.

The gas coming out from the uppermost tray (or packing top) can directly go out of the fractionation tower and enter the subcooler 6 for rewarming. Also can as shown in Figure 1, enter tower top condenser 4, further liquefaction, liquid refluxes to fractionating tower 3 as reflux liquid, gas (tail gas) goes out subcooler 6 after going out condenser 4. In this way, the trace amount of methane in the gas will be further condensed, which improves the extraction rate of methane, but the energy consumption will increase.

The thermal fluid exchanging heat with the high-pressure liquefied natural gas in the heat exchanger 8 can be refrigerated gas or raw gas, which can be adjusted according to the process requirements. In this example, the thermal fluid is refrigerated gas. As shown in Figure 1, the refrigerant gas C (such as nitrogen) is compressed by the compressor 9 and cooled by the aftercooler 10, then enters the booster end 11 of the turboexpander for further pressurization, is cooled by the aftercooler 12, and then divided into two Road: one way enters the high-pressure heat exchanger 8 to exchange heat with LNG; the other way enters the heat exchanger 1 to exchange heat with the cold fluid. The two paths of refrigerated gas are cooled out of the heat exchanger and merged, then enter the expansion end 13 of the turbo expander, and become a low-temperature and low-pressure gas after expansion. Afterwards, it enters the cold end of heat exchanger 2 and 1 in turn to provide cooling capacity for the system, and then comes out, and then enters compressor 9 for compression, pressurization, cooling, expansion, and refrigeration, and so on.

It should be noted that the flow diagram shown in Figure 1 is not a fixed model, and can be adjusted according to actual needs and cooling capacity ratio. For example, whether to add a condenser to the top of the fractionation tower, whether the hot fluid in the high-pressure heat exchanger 8 goes through the cooling gas or the raw gas, whether to set a subcooler before the low-temperature liquid pump, etc., can be combined arbitrarily.

Claims (8)

1. A device for producing compressed natural gas from methane-containing mixed gas, comprising: a refrigeration unit in which the methane-containing mixture is cooled to produce a gas-liquid mixture; A methane-containing mixed gas separation device comprising a fractionation tower for separating liquefied natural gas from said gas-liquid mixture, and having an inlet for inputting said gas-liquid mixture, a top gas outlet and a gas outlet for discharging liquefied natural gas bottom liquid outlet; It is characterized in that the equipment also includes a cryogenic liquid pump having an outlet and an inlet connected to the bottom liquid outlet of the fractionation tower, and a high-pressure heat exchanger, and the cryogenic liquid pump adds the liquefied natural gas from the fractionation tower to The pressure is sent to the high pressure heat exchanger. 2. The apparatus according to claim 1, further comprising a reboiler arranged between the bottom liquid outlet of the fractionation tower and the inlet of the cryogenic liquid pump for heating the liquefied natural gas flowing therein , in order to improve the purity of liquefied natural gas. 3. The apparatus according to claim 2, further comprising a subcooler disposed between the outlet of the reboiler and the inlet of the cryogenic liquid pump for cooling the liquefied natural gas flowing therein. 4. The device according to claim 3, further comprising a condenser arranged between the top gas outlet of the fractionation tower and the subcooler, for condensing the mixed gas containing methane flowing therein. 5 . The device according to claim 4 , wherein the refrigerating device comprises a gas expansion refrigerating device or a mixed working medium refrigerating device, wherein the gas expansion refrigerating device includes a heat exchanger. 6. The equipment according to claim 5, characterized in that the exhaust gas coming out of the subcooler passes through the heat exchanger of the refrigeration device to provide cooling capacity for the heat exchanger. 7. The equipment according to claim 6, characterized in that the high-pressure heat exchanger is in communication with the mixed gas containing methane to provide hot fluid for the high-pressure heat exchanger. 8 . The device according to claim 6 , wherein the high-pressure heat exchanger is in communication with refrigerant gas to provide hot fluid for the high-pressure heat exchanger.

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