Natural gas pretreatment dechlorination method and device

Abstract

The invention belongs to the field of natural gas ground engineering, and discloses a natural gas pretreatment dechlorination method and device. The device comprises a flushing water buffer injection facility, a natural gas pretreatment facility, a flushing water circulating pump, a wastewater flash tank and an optional alkali liquor buffer injection facility. The device disclosed by the invention adopts an integrated circulating spraying technology and equipment, the occupied area is saved, and the device and the method disclosed by the invention can be used for effectively removing chloride ions and free acid in the natural gas.

Description

Technical Field

[0001] The present invention belongs to the field of natural gas surface engineering, and more specifically, relates to a natural gas pretreatment dechlorination method and device. Background Art

[0002] Natural gas gathering, transportation and purification is an intermediate link in the natural gas production process. The purpose of this link is to remove almost all H2S and H2O from the sour natural gas extracted from the gas field, and partially remove CO2, so that the quality of the purified natural gas meets the requirements of the national standard "Natural Gas" product gas.

[0003] At present, the material selection of equipment and pipelines in domestic natural gas purification plants does not take into account the chloride ions carried in the raw natural gas. In addition, key equipment such as natural gas feed filters, natural gas desulfurization towers, lean and rich amine liquid heat exchangers and solvent regeneration towers are all made of stainless steel. Sour natural gas pipelines and instruments are also largely made of stainless steel.

[0004] However, during the actual operation of natural gas gathering and purification plants, the raw natural gas often carries a large amount of chlorine-containing droplets. According to measurements at a natural gas purification plant, during the five-year operation period from 2010 to 2015, the average chloride ion concentration in the effluent from the natural gas plant was 11,000 mg / L.

[0005] According to the NACE standard, the chloride ion concentration requirements for 316L austenitic stainless steel are as follows: When the temperature is less than 60°C and the H2S partial pressure is less than 350kPa, the chloride ion concentration must not exceed 50mg / L. Therefore, the chloride ion concentration carried by the purification plant's raw gas far exceeds the design and standard requirements, posing a risk of chloride-induced hydrogen sulfide stress corrosion cracking. The raw gas pipeline conveys a high-pressure medium and typically contains toxic components such as hydrogen sulfide and organic sulfur. Once chloride-induced hydrogen sulfide stress corrosion cracking occurs, the raw gas leaks in large quantities and at high speeds, affecting a wide range of areas, posing risks of human poisoning, fire and explosion, and environmental pollution. If the overall material quality is improved, the investment in the purification plant will increase significantly. Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies and provides a method and apparatus for pre-treatment dechlorination of natural gas. The apparatus utilizes integrated circulating spray technology and equipment, saving floor space. The apparatus and method can effectively remove chloride ions and free acids from natural gas.

[0007] To achieve the above objectives, the present invention provides a natural gas pretreatment dechlorination device, which includes a flushing water buffer injection facility, a natural gas pretreatment facility, a flushing water circulation pump and a wastewater flash tank, and optionally an alkali solution buffer injection facility;

[0008] The natural gas pretreatment facility includes a pretreatment section, a water washing section, and a separation section; the separation section is vertically arranged above the water washing section, and a flushing water inlet is provided on the side wall of the separation section near the bottom of the separation section; a circulating flushing water outlet is provided on the bottom side wall of the water washing section, and a wastewater outlet is provided at the bottom of the water washing section;

[0009] The flushing water buffer injection facility includes a flushing water buffer tank and a flushing water pump, and the water outlet of the flushing water buffer tank is connected to the flushing water inlet through the flushing water pump;

[0010] A natural gas inlet and a circulating flushing water spray inlet are provided above the pretreatment section; the circulating flushing water outlet is connected to the circulating flushing water spray inlet via the flushing water circulating pump; optionally, the alkali liquid buffer injection facility comprises an alkali liquid buffer tank and an alkali liquid pump, and the alkali liquid outlet of the alkali liquid buffer tank is connected to the flushing water circulating pump inlet via the alkali liquid pump;

[0011] The outlet of the pretreatment section is connected to the upper side wall of the water washing section;

[0012] The wastewater outlet is connected to the feed port of the wastewater flash tank;

[0013] A pre-treated natural gas outlet is provided above the separation section, and the pre-treated natural gas outlet is connected to a gathering and transportation pipeline network or a purification device.

[0014] In the present invention, the natural gas processing capacity of the purification device can be as high as 36 million cubic meters per day.

[0015] According to the present invention, preferably, the water inlet of the flushing water buffer tank is connected to the boundary flushing water pipeline.

[0016] According to the present invention, preferably, the natural gas inlet is connected to a natural gas pipeline in a restricted area, and preferably, the natural gas pipeline in the restricted area is connected to a production wellhead of a gas field.

[0017] According to the present invention, preferably, the alkali inlet of the alkali buffer tank is connected to the alkali delivery device. In the present invention, the alkali in the alkali buffer tank is injected into the circulating flushing water to adjust the pH of the circulating flushing water and promote the absorption of acid components in natural gas.

[0018] According to the present invention, the wastewater flash tank preferably has a flash gas outlet at the top and a flash wastewater outlet at the bottom. The flash gas outlet is connected to a sulfur recovery unit and / or a flare, and the flash wastewater outlet is connected to a wastewater treatment unit. In the present invention, as a preferred embodiment, the wastewater flash tank can flash off dissolved acid gas components (H2S, CO2) and hydrocarbon components in the chlorine-containing wastewater by reducing the pressure.

[0019] According to the present invention, preferably, the inlet pipeline of the flushing water circulation pump is connected to the circulating flushing water outlet and the alkali solution pump outlet at the same time.

[0020] According to the present invention, preferably, the pretreatment section is equipped with multiple nozzles for forward and / or reverse spraying, connected to the circulating flushing water spray inlet. In the present invention, as a preferred embodiment, the circulating flushing water and alkali solution are mixed and then passed through the nozzles for high-speed and intense contact with the natural gas, thereby removing acid components and chloride ions carried by the natural gas.

[0021] According to the present invention, preferably, a gas-liquid separation element and a spray element are provided in the water washing section, and the spray element is provided on the upper part of the gas-liquid separation element.

[0022] According to the present invention, preferably, a coalescing element is provided in the separation section to further reduce the impact of natural gas on the gathering and transportation pipeline network or purification device.

[0023] According to the present invention, preferably, the pretreatment section is an L-shaped pipeline, one end of the L-shaped pipeline is provided with a natural gas inlet and a circulating flushing water spray inlet, and the other end is the outlet of the pretreatment section.

[0024] According to the present invention, preferably, the wastewater outlet is connected to the feed port of the wastewater flash tank via a liquid-controlled valve.

[0025] According to the present invention, preferably, the flash gas outlet is connected to a sulfur recovery device and / or a flare via a pressure regulating valve.

[0026] According to the present invention, preferably, the flash wastewater outlet is connected to a wastewater treatment device via a flow and liquid level cascade control system.

[0027] According to the present invention, preferably, the flushing water circulation pump is a variable frequency controlled shielded pump.

[0028] According to the present invention, preferably, the flushing water pump is an automatic variable frequency regulated reciprocating pump.

[0029] According to the present invention, preferably, the alkali solution pump is an automatic variable frequency regulated reciprocating pump.

[0030] According to the present invention, preferably, the purification device is made of at least one of 316L austenitic stainless steel, duplex steel, 316 stainless steel and 825 stainless steel.

[0031] Another aspect of the present invention provides a method for pre-treatment and dechlorination of natural gas, which uses the above-mentioned device and comprises the following steps:

[0032] The flushing water entering the flushing water buffer tank is pressurized by the flushing water pump and then sent to the natural gas pretreatment facility;

[0033] In the natural gas pretreatment facility, the natural gas contacts the circulating flushing water from the bottom of the water washing section and the optional alkaline solution from the alkaline solution buffer tank in the pretreatment section, and after flushing, obtains flushed natural gas and chlorine-containing flushing water; the flushed natural gas and chlorine-containing flushing water are fed into the water washing section;

[0034] The washed natural gas contacts the washing water from the washing water buffer tank in the water washing section, undergoes washing, impurity removal and primary gas-liquid separation, and obtains pretreated natural gas and chlorine-containing wastewater;

[0035] The pretreated natural gas enters the separation section, undergoes gas-liquid separation and impurity removal, and is then sent to the gathering and transportation network or purification device;

[0036] A portion of the chlorine-containing wastewater is used as the circulating flushing water, and the remaining portion is sent to the wastewater flash tank through the wastewater outlet.

[0037] According to the present invention, preferably, the flushing water comes from a public engineering unit and is sent into the flushing water buffer tank through the boundary flushing water pipeline.

[0038] According to the present invention, preferably, the chlorine-containing wastewater fed into the wastewater flash tank is flash-treated to obtain flash gas and flash wastewater, the flash gas is fed into a sulfur recovery device and / or a flare for recovery, and the flash wastewater is fed into a wastewater treatment device for treatment.

[0039] According to the present invention, preferably, the natural gas is contacted in the pretreatment section with the circulating flushing water from the bottom of the water washing section and optionally the alkali solution from the alkali solution buffer tank in a countercurrent or cocurrent manner.

[0040] According to the present invention, preferably, the flushing water buffer tank is maintained at an operating pressure of 0.05-0.25 MPaG by nitrogen.

[0041] According to the present invention, preferably, the alkali solution buffer tank is maintained at an operating pressure of 0.05-0.25 MPaG by nitrogen.

[0042] According to the present invention, preferably, the temperature of the flushing water buffer tank is 30-39°C.

[0043] According to the present invention, preferably, the temperature of the alkali solution buffer tank is 30-39°C.

[0044] According to the present invention, preferably, the outlet pressure of the flushing water circulation pump is 2.0-9.2 MPaG.

[0045] According to the present invention, preferably, the outlet pressure of the alkali solution pump is 2.0-9.2 MPaG;

[0046] According to the present invention, preferably, the flow rate of the alkali solution pump is controlled by the pH of the liquid at the outlet of the flushing water circulation pump.

[0047] According to the present invention, preferably, the operating pressure of the wastewater flash tank is controlled to be 0.2-2.0 MPaG by a flash gas pressure control valve.

[0048] The beneficial effects of the technical solution of the present invention are as follows:

[0049] 1. The device and method of the present invention are proposed to address the situation where the existing raw natural gas has a high chloride ion content and contains free acid and other solid and liquid impurities, which pose a safety hazard to natural gas purification equipment. The device and method of the present invention can be used at the natural gas field production wellhead, upstream of the gathering and transportation pipeline, or upstream of the purification device to effectively remove chloride ions, free acid and other solid and liquid impurities in natural gas. After treatment by the present invention, the chloride ion concentration in the entrained droplets of natural gas is <50 mg / L, meeting the requirements of downstream equipment and pipeline materials. In addition, due to the removal of free acid, the natural gas pretreatment facilities, downstream equipment and pipeline materials of the present invention can be made of lower-priced materials, thereby achieving economic cost savings.

[0050] 2. The device and method of the present invention can reduce the chloride ion concentration in natural gas, and at the same time remove solid and hydrocarbon impurities such as free acid and sand carried in the raw natural gas, thereby reducing the impact on downstream devices and ensuring the safe operation of downstream purification devices. It is suitable for large natural gas fields.

[0051] 3. The device of the present invention utilizes integrated circulating spray technology and equipment. Compared to solutions that arrange the pretreatment and water washing sections from top to bottom, the device of the present invention separates the pretreatment section, significantly saving floor space. It is suitable for use at natural gas field production wellheads, upstream of gathering and transportation pipelines, or upstream of purification units. It reduces feed gas loss and significantly reduces flushing water consumption. The treated wastewater can be sent to a sewage treatment plant after subsequent treatment, minimizing environmental impact. The device of the present invention can be modified from existing devices.

[0052] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0054] Figure 1 A schematic diagram of a natural gas pretreatment and dechlorination device provided in Example 1 of the present invention is shown.

[0055] Figure 2A schematic diagram of a natural gas pretreatment and dechlorination device provided in Example 2 of the present invention is shown.

[0056] The following are the descriptions of the reference numerals:

[0057] 1 Natural gas pretreatment facility; 1-1 Pretreatment section; 1-2 Water washing section; 1-3 Separation section; 2 Flushing water circulation pump; 3 Wastewater flash tank; 4 Flushing water buffer injection facility; 4-1 Flushing water buffer tank; 4-2 Flushing water pump; 5 Alkali buffer injection facility; 5-1 Alkali buffer tank; 5-2 Alkali pump;

[0058] Logistics: S1 natural gas; S2 pretreated natural gas; S3 circulating flushing water spray inlet inlet; S4 chlorinated wastewater; S5 high-pressure flushing water; S6 fresh flushing water; S7 flash steam; S8 external chlorinated wastewater; S9 alkali solution. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0060] Example 1

[0061] This embodiment provides a natural gas pretreatment dechlorination device, such as Figure 1 As shown, the device includes a flushing water buffer injection facility 4, a natural gas pretreatment facility 1, a flushing water circulation pump 2 and a wastewater flash tank 3;

[0062] The natural gas pretreatment facility 1 includes a pretreatment section 1-1, a water washing section 1-2, and a separation section 1-3. The combined equipment of the water washing section 1-2 and the separation section 1-3 is 8 meters high and 0.8 meters in diameter. The pretreatment section 1-1 is 3 meters high and 0.3 meters in diameter. The separation section 1-3 is vertically disposed above the water washing section 1-2. A flushing water inlet is provided on the side wall of the separation section 1-3, near the bottom of the separation section 1-3. A circulating flushing water outlet is provided on the bottom side wall of the water washing section 1-2, and a wastewater outlet is provided at the bottom of the water washing section. A gas-liquid separation element and a spray element (not shown) are provided within the water washing section, with the spray element being disposed above the gas-liquid separation element.

[0063] The flushing water buffer injection facility 4 includes a flushing water buffer tank 4-1 and a flushing water pump 4-2. The water inlet of the flushing water buffer tank 4-1 is connected to the boundary area flushing water pipeline, and the water outlet of the flushing water buffer tank 4-1 is connected to the flushing water inlet through the flushing water pump 4-2. The flushing water pump 4-2 is an automatic variable frequency reciprocating pump.

[0064] The pretreatment section 1-1 is an L-shaped pipeline, with a natural gas inlet and a circulating flushing water spray inlet provided above one end of the L-shaped pipeline; the natural gas inlet is connected to the boundary area natural gas pipeline, which is connected to the gas field production wellhead; the circulating flushing water outlet is connected to the circulating flushing water spray inlet via the flushing water circulating pump 2; a plurality of sequential spray nozzles are provided in the pretreatment section and connected to the circulating flushing water spray inlet; the flushing water circulating pump 2 is a variable frequency controlled shielded pump;

[0065] The other end of the L-shaped pipe is the outlet of the pretreatment section 1-1, and the outlet of the pretreatment section 1-1 is connected to the upper side wall of the water washing section 1-2;

[0066] The wastewater outlet is connected to the feed port of the wastewater flash tank 3 through a liquid-controlled valve; a flash gas outlet is provided at the top of the wastewater flash tank 3, and a flash wastewater outlet is provided at the bottom. The flash gas outlet is connected to the flare through a pressure regulating valve, and the flash wastewater outlet is connected to the wastewater treatment device through a flow and liquid level cascade control system;

[0067] A pre-treated natural gas outlet is provided above the separation sections 1-3, and the pre-treated natural gas outlet is connected to a purification device. A coalescing element is provided in the separation section. The purification device is made of 825 stainless steel.

[0068] The above-mentioned device is used to pre-treat and dechlorinate natural gas, which includes the following steps:

[0069] The flushing water (performance parameters are shown in Table 1) of the public engineering unit is sent to the flushing water buffer tank 4-1 through the boundary flushing water pipeline; the flushing water in the flushing water buffer tank 4-1 (the flushing water buffer tank 4-1 is maintained at an operating pressure of 0.2 MPaG by nitrogen) is pumped through the flushing water pump 4-2 (normal flow rate 0.3m 3 / h, outlet pressure 9.0MPaG) and then pressurized and sent to the natural gas pretreatment facility 1;

[0070] Table 1 Flushing water performance parameters

[0071] pH 6.5-9.0 <![CDATA[H2S]]> <0.1 mg / L suspended solids ≤10.0mg / L Temperature, °C 39

[0072] In the natural gas pretreatment facility 1, natural gas (flow rate is 20000Nm 3 / h, the composition and performance parameters are shown in Table 2) in the pretreatment section 1-1 and contact with the circulating flushing water from the bottom of the water washing section 1-2. After flushing, the chloride ions in the natural gas are removed and a small amount of H2S, CO2 and hydrocarbons are dissolved to obtain flushed natural gas and chlorine-containing flushing water; the flushed natural gas and chlorine-containing flushing water are sent to the water washing section 1-2;

[0073] The washed natural gas is contacted with the wash water from the wash water buffer tank 4-1 in the water wash section 1-2, and is washed, impurity-removed, and subjected to primary gas-liquid separation to further remove chloride ions, thereby obtaining pretreated natural gas and chlorine-containing wastewater (composition and performance parameters are shown in Table 3);

[0074] The pretreated natural gas enters the separation section 1-3, and after gas-liquid separation and impurity removal, the liquid droplets and other impurities carried therein are removed to obtain a temperature of 35.94°C, a pressure of 8.29-8.49 MPaG, and a flow rate of 19995m 3 / hour, the natural gas with a chloride ion concentration of <50 mg / L is transported into the gathering and transportation network or purification device;

[0075] A portion of the chlorine-containing wastewater is passed through the flushing water circulation pump 2 (normal flow rate is 15m 3 / h, rated flow rate 18m 3 / h, the inlet pressure of the flushing water circulation pump is 8.4MPaG, and the outlet pressure of the flushing water circulation pump is 9.0MPaG) as the circulating flushing water, and the remaining part is sent to the wastewater flash tank 3 through the wastewater outlet.

[0076] Table 2 Composition and performance parameters of natural gas

[0077]

[0078] Table 3 Composition and performance parameters of chlorine-containing wastewater in Example 1

[0079]

[0080]

[0081] The chlorine-containing wastewater sent to the wastewater flash tank 3 (the operating pressure is controlled by the flash vapor pressure control valve to be 0.6 MPaG) is flash-evaporated to obtain flash vapor (H2S, CO2 and hydrocarbons dissolved in the chlorine-containing wastewater, the composition and performance parameters are shown in Table 4) and flash vaporized wastewater. The flash vapor is sent to the flare for recovery, and the flash vaporized wastewater is sent to the wastewater treatment device for treatment;

[0082] Table 4

[0083]

[0084] Example 2

[0085] This embodiment provides a natural gas pretreatment dechlorination device, such as Figure 2 As shown, the difference between this embodiment and embodiment 1 is that the device further includes an alkali solution buffer injection facility 5;

[0086] The alkali solution buffer injection facility 5 includes an alkali solution buffer tank 5-1 and an alkali solution pump 5-2. The alkali solution outlet of the alkali solution buffer tank 5-1 is connected to the inlet of the flushing water circulation pump 2 through the alkali solution pump 5-2. Therefore, the inlet pipeline of the flushing water circulation pump 2 is connected to the circulating flushing water outlet and the outlet of the alkali solution pump 5-2 at the same time; the alkali solution pump 5-2 is an automatic variable frequency reciprocating pump;

[0087] The purification device is made of 316L austenitic stainless steel.

[0088] The above-mentioned device is used to pre-treat and dechlorinate natural gas, which includes the following steps:

[0089] The flushing water (performance parameters are shown in Table 1) of the public engineering unit is sent to the flushing water buffer tank 4-1 through the boundary flushing water pipeline; the flushing water in the flushing water buffer tank 4-1 (the flushing water buffer tank 4-1 is maintained at an operating pressure of 0.2 MPaG by nitrogen) is pumped through the flushing water pump 4-2 (normal flow rate 0.3m 3 / h, outlet pressure 9.0MPaG) and then pressurized and sent to the natural gas pretreatment facility 1;

[0090] In the natural gas pretreatment facility 1, natural gas (flow rate is 20000Nm 3 / h, composition and performance parameters are shown in Table 2) in the pretreatment section 1-1 with the circulating flushing water from the bottom of the water washing section and the alkali solution from the alkali solution buffer tank 5-1 (the flow rate of the alkali solution S9 is adjusted by the pH value of the water inlet S3 of the circulating flushing water spray inlet, and the control value is 7-7.5; the normal flow rate of the alkali solution pump is 1L / h, the rated flow rate is 10L / h, the alkali solution pump inlet pressure is 0.1MPaG, and the alkali solution pump outlet pressure is 9.0MPaG). After flushing, the chloride ions and acid components in the natural gas are removed, and a small amount of H2S, CO2 and hydrocarbons are dissolved, thereby obtaining flushed natural gas and chlorine-containing flushing water; the flushed natural gas and chlorine-containing flushing water are sent to the water washing section 1-2;

[0091] The washed natural gas is contacted with the wash water from the wash water buffer tank 4-1 in the water wash section 1-2, and is washed, impurity-removed, and subjected to primary gas-liquid separation to further remove chloride ions, acid components, and alkali liquor, thereby obtaining pretreated natural gas and chlorine-containing wastewater (composition and performance parameters are shown in Table 5);

[0092] The pretreated natural gas enters the separation section 1-3, and after gas-liquid separation and impurity removal, the liquid droplets and other impurities carried therein are removed to obtain a temperature of 35.94°C, a pressure of 8.29-8.49 MPaG, and a flow rate of 19995m 3 / hour, natural gas with a total concentration of acid components and chloride ions in the entrained droplets of less than 50 mg / L is sent to the gathering and transportation network or purification device;

[0093] A portion of the chlorine-containing wastewater is passed through the flushing water circulation pump 2 (normal flow rate is 15m 3 / h, rated flow rate 18m 3 / h, the inlet pressure of the flushing water circulation pump is 8.4MPaG, and the outlet pressure of the flushing water circulation pump is 9.0MPaG) as the circulating flushing water, and the remaining part is sent to the wastewater flash tank 3 through the wastewater outlet.

[0094] Table 5 Composition and performance parameters of chlorine-containing wastewater in Example 2

[0095]

[0096] The chlorine-containing wastewater sent to the wastewater flash tank 3 (the operating pressure is controlled by the flash vapor pressure control valve to be 0.6 MPaG) is flash-evaporated to obtain flash vapor (H2S, CO2 and hydrocarbons dissolved in the chlorine-containing wastewater, the composition and performance parameters are shown in Table 4) and flash vaporized wastewater. The flash vapor is sent to the flare for recovery, and the flash vaporized wastewater is sent to the wastewater treatment device for treatment;

[0097] Comparative Example 1

[0098] This comparative example provides a natural gas dechlorination device and process, which is the device and process described in the embodiment of application No. 202010141197.6.

[0099] The device of the present invention adopts integrated circulating spraying technology and equipment. Compared with the scheme in which the pretreatment section and the water washing section are arranged from top to bottom in Comparative Example 1, the device of the present invention leads the pretreatment section out separately, which greatly saves the floor space. Specifically:

[0100] Comparative Example 1 actually uses a tower structure with a liquid separator at the top. The first water wash section is equivalent to a spray, while the second water wash section below is actually a water wash. However, during the water wash process in Comparative Example 1, the gas phase carries more liquid from bottom to top, thus reducing the dechlorination effect of the water wash. Therefore, if Comparative Example 1 is to achieve a dechlorination effect similar to that of the present application, its tower needs to be approximately 23 meters high and 1 meter in diameter.

[0101] The present invention separates the pretreatment section, achieving full contact dechlorination and gas-liquid separation in a smaller space, and provides a gas-liquid separation element in the water washing section, thereby reducing the impact of entrained liquid and enhancing the dechlorination effect. As described in Example 1-2, the equipment height of the water washing section 1-2 and the separation section 1-3 connected together is 8 meters and the diameter is 0.8 meters; the height of the pretreatment section 1-1 is 3 meters and the diameter is 0.3 meters, saving space and equipment investment.

[0102] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A natural gas pretreatment dechlorination device, characterized in that: The apparatus comprises a flushing water buffer injection facility, a natural gas pre-treatment facility, a flushing water circulation pump and a wastewater flash tank, and optionally, an alkali solution buffer injection facility; The natural gas pretreatment facility includes a pretreatment section, a water washing section, and a separation section; the separation section is vertically arranged above the water washing section, and a flushing water inlet is provided on the side wall of the separation section near the bottom of the separation section; a circulating flushing water outlet is provided on the bottom side wall of the water washing section, and a wastewater outlet is provided at the bottom of the water washing section; The flushing water buffer injection facility includes a flushing water buffer tank and a flushing water pump, and the water outlet of the flushing water buffer tank is connected to the flushing water inlet through the flushing water pump; A natural gas inlet and a circulating flushing water spray inlet are provided above the pretreatment section; the circulating flushing water outlet is connected to the circulating flushing water spray inlet via the flushing water circulating pump; optionally, the alkali liquid buffer injection facility comprises an alkali liquid buffer tank and an alkali liquid pump, and the alkali liquid outlet of the alkali liquid buffer tank is connected to the flushing water circulating pump inlet via the alkali liquid pump; The outlet of the pretreatment section is connected to the upper side wall of the water washing section; The wastewater outlet is connected to the feed port of the wastewater flash tank; A pre-treated natural gas outlet is provided above the separation section, and the pre-treated natural gas outlet is connected to a gathering and transportation pipeline network or a purification device.

2. The natural gas pretreatment device according to claim 1, wherein: The water inlet of the flushing water buffer tank is connected to the boundary area flushing water pipeline; The natural gas inlet is connected to a natural gas pipeline in a restricted area. Preferably, the natural gas pipeline in the restricted area is connected to a gas field production wellhead. The alkali liquid inlet of the alkali liquid buffer tank is connected to the alkali liquid conveying device; The wastewater flash tank is provided with a flash gas outlet at the top and a flash wastewater outlet at the bottom. The flash gas outlet is connected to a sulfur recovery device and / or a flare, and the flash wastewater outlet is connected to a wastewater treatment device. The inlet pipeline of the flushing water circulation pump is connected to the circulating flushing water outlet and the alkali solution pump outlet at the same time.

3. The natural gas pretreatment and dechlorination device according to claim 1, wherein: The pretreatment section is provided with a plurality of nozzles for forward and / or reverse spraying, which are connected to the circulating flushing water spray inlet; The water washing section is provided with a gas-liquid separation element and a spray element, and the spray element is arranged on the upper part of the gas-liquid separation element; A coalescing element is provided in the separation section.

4. The natural gas pretreatment and dechlorination device according to claim 1, wherein: The pretreatment section is an L-shaped pipeline, one end of which is provided with a natural gas inlet and a circulating flushing water spray inlet, and the other end is the outlet of the pretreatment section.

5. The natural gas pretreatment and dechlorination device according to claim 1, wherein: The wastewater outlet is connected to the feed port of the wastewater flash tank through a hydraulically controlled valve; The flash gas outlet is connected to a sulfur recovery unit and / or a flare via a pressure regulating valve; The flash wastewater outlet is connected to the wastewater treatment device through a flow and liquid level cascade control system.

6. The natural gas pretreatment and dechlorination device according to claim 1, wherein: The flushing water circulation pump is a variable frequency controlled shielded pump; The flushing water pump is an automatic frequency conversion reciprocating pump; The alkali solution pump is an automatic frequency conversion adjustment reciprocating pump.

7. The natural gas pretreatment and dechlorination device according to claim 1, wherein: The purification device is made of at least one of 316L austenitic stainless steel, duplex steel, 316 stainless steel and 825 stainless steel.

8. A natural gas pretreatment dechlorination method, characterized in that: The method uses the device according to any one of claims 1 to 7, comprising the following steps: The flushing water entering the flushing water buffer tank is pressurized by the flushing water pump and then sent to the natural gas pretreatment facility; In the natural gas pretreatment facility, the natural gas contacts the circulating flushing water from the bottom of the water washing section and the optional alkaline solution from the alkaline solution buffer tank in the pretreatment section, and after flushing, obtains flushed natural gas and chlorine-containing flushing water; the flushed natural gas and chlorine-containing flushing water are fed into the water washing section; The washed natural gas contacts the washing water from the washing water buffer tank in the water washing section, undergoes washing, impurity removal and primary gas-liquid separation, and obtains pretreated natural gas and chlorine-containing wastewater; The pretreated natural gas enters the separation section, undergoes gas-liquid separation and impurity removal, and is then sent to the gathering and transportation network or purification device; A portion of the chlorine-containing wastewater is used as the circulating flushing water, and the remaining portion is sent to the wastewater flash tank through the wastewater outlet.

9. The natural gas pretreatment dechlorination method according to claim 8, wherein: The flushing water comes from the public engineering unit and is sent to the flushing water buffer tank through the boundary flushing water pipeline; The chlorine-containing wastewater fed into the wastewater flash tank is flash-distilled to obtain flash gas and flash wastewater, the flash gas is fed into a sulfur recovery device and / or a flare for recovery, and the flash wastewater is fed into a wastewater treatment device for treatment; In the pretreatment section, the natural gas contacts the circulating flushing water from the bottom of the water washing section and optionally the alkali solution from the alkali solution buffer tank in a reverse or forward manner.

10. The natural gas pretreatment dechlorination method according to claim 8, wherein: The flushing water buffer tank is maintained at an operating pressure of 0.05-0.25 MPaG by nitrogen; The alkali solution buffer tank is maintained at an operating pressure of 0.05-0.25 MPaG by nitrogen; The temperature of the flushing water buffer tank is 30-39°C; The temperature of the alkali solution buffer tank is 30-39°C; The outlet pressure of the flushing water circulation pump is 2.0-9.2 MPaG; The outlet pressure of the alkali liquid pump is 2.0-9.2 MPaG; The flow rate of the alkali solution pump is controlled by the pH of the liquid at the outlet of the flushing water circulation pump; The wastewater flash tank controls the operating pressure to be 0.2-2.0 MPaG through a flash vapor pressure control valve.

Images