Methanol rectification removal device

Abstract

The utility model provides a methanol rectification removal device which comprises a carbon dioxide absorption tower, a rectification tower I and a rectification tower II, the gas inlet end of the carbon dioxide absorption tower is connected with a methanol-containing natural gas pipeline, the bottom end of the carbon dioxide absorption tower is connected with a flash tank in a cross-flow manner, and the liquid outlet end of the flash tank is connected with a lean and rich liquid heat exchanger through a pipeline. The liquid outlet end of the rich and lean liquid heat exchanger is connected with a buffer tank through a pipeline, and the liquid outlet end of the buffer tank is connected with a methanol-containing natural gas pipeline. According to the utility model, natural gas in methanol is indirectly removed in a manner of removing methanol in regenerated gas generated during regeneration in an LNG (Liquefied Natural Gas) liquefaction plant, so that the purpose of stable production is achieved, and meanwhile, methanol in natural gas in the LNG liquefaction plant is indirectly removed in a double-tower rectification manner of the first rectification tower and the second rectification tower, so that the production efficiency is improved. Under the condition that methanol is not added into an upstream gas station, methanol is removed at the minimum cost in an LNG (Liquefied Natural Gas) liquefaction plant, and stable production is maintained while freezing blockage is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of methanol processing and relates to a methanol distillation removal device. Background Art

[0002] The raw materials of all LNG liquefaction plants are coalbed methane, coke oven gas, and pipeline gas (hereinafter referred to as natural gas). No methanol component is produced in naturally formed coalbed methane, sandstone gas, and coke oven gas produced by chemical exhaust gas.

[0003] However, the gas gathering station receives natural gas from the wellhead, adjusts it to medium pressure, and then transmits it to the urban area / LNG liquefaction plant pipeline. The natural gas inlet of the pressure regulating box at the end of the medium-pressure pipeline frequently suffers from freezing and blockage in winter, so the methanol in the natural gas needs to be treated. Summary of the Invention

[0004] The purpose of the present invention is to provide a methanol distillation and removal device to solve the problems raised in the above background technology.

[0005] The purpose of the utility model can be achieved through the following technical solutions: a methanol distillation removal device, comprising a carbon dioxide absorption tower, a first distillation tower and a second distillation tower, the air inlet end of the carbon dioxide absorption tower is connected to a natural gas pipeline containing methanol, the bottom end of the carbon dioxide absorption tower is connected to a flash tank, the liquid outlet pipeline of the flash tank is connected to a lean-rich liquid heat exchanger, the liquid outlet pipeline of the lean-rich liquid heat exchanger is connected to a buffer tank, the liquid outlet end of the buffer tank is connected to a natural gas pipeline containing methanol, and a lean liquid pump is fixedly installed in the middle of the liquid outlet pipeline of the buffer tank. The top pipeline of the lean-rich liquid heat exchanger is connected to a regeneration tower, the top pipeline of the regeneration tower is connected to a regeneration gas-liquid separator, and a regeneration gas cooler is fixedly installed on the pipeline between the regeneration tower and the regeneration gas-liquid separator, the regeneration gas-liquid separator is connected to a distillate heat exchanger through a first booster pump pipeline, the distillate heat exchanger is respectively connected to a buffer tank and a distillation tower pipeline, the distillation tower pipeline is connected to a top condenser, the top condenser is connected to a distillation tower pipeline, and the bottom of the distillation tower is connected to the distillate heat exchanger pipeline through a second booster pump.

[0006] In the above-mentioned methanol distillation removal device, heaters are fixedly installed at the bottoms of the regeneration tower, the first distillation tower and the second distillation tower.

[0007] In the above-mentioned methanol distillation removal device, the water inlet and outlet of the top condenser are both connected to the external circulating cooling water through a water pump.

[0008] In the above-mentioned methanol distillation removal device, pressure detectors are fixedly installed on the front faces of the carbon dioxide absorption tower, the regeneration tower, the first distillation tower and the second distillation tower.

[0009] Compared with the existing technology, the advantages of the methanol distillation and removal device of the present invention are: by removing the methanol in the regeneration gas generated during the regeneration of the LNG liquefaction plant, the natural gas in the methanol is indirectly removed, thereby achieving the purpose of stable production. At the same time, a double-tower distillation method of a first distillation tower and a second distillation tower is adopted to indirectly remove the methanol in the natural gas of the LNG liquefaction plant. In the case that it is impossible to prevent the upstream gas station from adding methanol, the methanol can be removed at the lowest cost in the LNG liquefaction plant, and stable production can be maintained while preventing freezing and blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the methanol distillation removal device of the present invention.

[0011] In the figure, 1. Carbon dioxide absorption tower; 2. Lean liquid pump; 3. Flash tank; 4. Lean and rich liquid heat exchanger; 5. Regeneration tower; 6. First booster pump; 7. Buffer tank; 8. Second booster pump; 9. Regeneration gas cooler; 10. Regeneration gas-liquid separator; 11. Fraction heat exchanger; 12. Distillation tower 1; 13. Top condenser; 14. Distillation tower 2; 15. Heater. DETAILED DESCRIPTION

[0012] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0013] like Figure 1 As shown, the methanol distillation removal device of the present invention comprises a carbon dioxide absorption tower 1, a first distillation tower 12 and a second distillation tower 14. The air inlet end of the carbon dioxide absorption tower 1 is connected to a natural gas pipeline containing methanol. The bottom end of the carbon dioxide absorption tower 1 is connected to a flash tank 3 through-flow. The liquid outlet pipeline of the flash tank 3 is connected to a lean-rich liquid heat exchanger 4. The liquid outlet pipeline of the lean-rich liquid heat exchanger 4 is connected to a buffer tank 7. The liquid outlet end of the buffer tank 7 is connected to a natural gas pipeline containing methanol, and a lean liquid pump 2 is fixedly installed in the middle of the liquid outlet pipeline of the buffer tank 7. The top pipeline of the lean-rich liquid heat exchanger 4 is connected to There is a regeneration tower 5, the top pipeline of the regeneration tower 5 is connected to the regeneration gas-liquid separator 10, and the pipeline between the regeneration tower 5 and the regeneration gas-liquid separator 10 is fixedly installed with a regeneration gas cooler 9, the regeneration gas-liquid separator 10 is connected to the distillate heat exchanger 11 through the first booster pump 6 pipeline, the distillate heat exchanger 11 is respectively connected to the buffer tank 7 and the distillation tower 12 pipeline, the distillation tower 12 pipeline is connected to the top condenser 13, the top condenser 13 is connected to the distillation tower 2 14 pipeline, and the bottom of the distillation tower 2 14 is connected to the distillate heat exchanger 11 pipeline through the second booster pump 8.

[0014] like Figure 1As shown, in the methanol distillation and removal device of the present invention, heaters 15 are fixedly installed at the bottom of the regeneration tower 5, the first distillation tower 12 and the second distillation tower 14. The heater 15 has a voltage of 380 volts.

[0015] The water inlet and outlet of the tower top condenser 13 are both connected to external circulating cooling water through a water pump.

[0016] Pressure detectors are fixedly installed on the front of the carbon dioxide absorption tower 1 , the regeneration tower 5 , the first distillation tower 12 and the second distillation tower 14 .

[0017] Specifically, during the process, natural gas containing methanol first enters the carbon dioxide absorption tower 1, model "T2101", and passes through the packing layer from bottom to top in the tower. It is fully in contact with the 45% to 50% concentration MDEA aqueous solution sprayed from top to bottom on the packing surface. The high adsorption capacity of the 45% to 50% concentration MDEA aqueous solution at room temperature for carbon dioxide is used to remove carbon dioxide from the natural gas. At the same time, since methanol gas (droplets) and water are completely miscible, the methanol gas in the natural gas can also be dissolved in the MDEA solution. If the methanol content in the MDEA solution is less than 1.4%;

[0018] After the MDEA aqueous solution has absorbed the carbon dioxide, it enters the flash tank 3 of model "ST2101" from the bottom of the carbon dioxide absorption tower 1. The MDEA aqueous solution is pressed into the lean-rich liquid heat exchanger 4 of model "E2501" by using the pressure of the flash tank 3 and heated to 98℃~101℃. Then it enters the regeneration tower 5 of model "T2501" from the top and flows downward on the packing surface from top to bottom in a spray state. During the flow, a uniform liquid film is formed on the packing surface. The MDEA liquid at the bottom of the regeneration tower 5 is heated to a boiling state, and the steam evaporates upward and passes upward along the gaps on the packing surface. In the up-and-down process, the carbon dioxide and methanol dissolved in the downward MDEA solution will become gaseous due to the influence of high temperature, and go to the top of the regeneration tower 5 with the steam from bottom to top. During the whole regeneration process, the concentration of carbon dioxide and methanol decreases as the water vapor goes down, and finally a mixed gas of water vapor, methanol gas and carbon dioxide gas is obtained at the top of the regeneration tower 5.

[0019] At the top of the regeneration tower 5, a mixture of water vapor, methanol, and carbon dioxide is obtained. Following the pipeline, it first enters the E2801 regeneration gas cooler 9, where it is cooled to 35°C to 42°C by circulating cooling water. It then enters the ST2801 regeneration gas-liquid separator 10, where wastewater is obtained at the bottom. Due to the temperature range of 35°C to 42°C, carbon dioxide cannot condense and is completely discharged through the top vent pipe. However, due to its solubility and low boiling point, a large portion of methanol condenses into the liquid wastewater at the bottom of the regeneration gas-liquid separator 10. Monitoring indicates that the maximum concentration can reach 3.4% to 7%.

[0020] The liquid wastewater at the bottom of the regeneration gas-liquid separator 10 is pressurized by the first booster pump 6 and then enters the fraction heat exchanger 11 to be heated to 85°C to 92°C. It then enters the first distillation tower 12 and is sprayed downward from top to bottom. The liquid in the lower reboiler is heated to 101°C to 103°C. The boiling water vapor and methanol vapor evaporate upward along the gaps between the packings, exchanging mass and heat with the liquid film formed on the packing surface by the liquid sprayed from the top of the tower.

[0021] The boiling point of methanol at normal pressure is 65°C, while the boiling point of water is 100°C. Therefore, during the heat and mass exchange process on the packing surface, the methanol dissolved in the water will be heated and transformed into gas before the water vapor and flow upward with the steam. The water flowing from top to bottom will condense the water vapor from the bottom into water again, leaving only methanol gas and a part of water vapor, which flow out from the top of the tower.

[0022] The methanol gas and a portion of water vapor flowing out of the top of the regeneration gas-liquid separator 10 enter the top condenser 13 of model "E2803" along the pipeline, are cooled by circulating cooling water to form condensed water, and the temperature is controlled at 58°C to 62°C, slightly lower than the boiling point of methanol, and enter the top of the second distillation tower 14. The temperature of the liquid at the bottom of the second distillation tower 14 is controlled to be heated to 101°C to 103°C. The principle is the same as that of the first distillation tower 12. After secondary distillation, the methanol content in the water at the bottom of the second distillation tower 14 reaches below 0.05%. After passing through the pipeline and being cooled to room temperature by the distillate heat exchanger 11, it enters the buffer tank 7 before the lean liquid pump 2 for recycling. The non-condensable gas at the top of the second distillation tower 14 enters the flare for combustion treatment;

[0023] After two distillations, the methanol in the MDEA aqueous solution can be completely removed, and the distilled water returns to the front buffer tank 7 of the lean liquid pump 2 of the MDEA system, and the insufficient part is supplemented with desalted water.

[0024] Matters not described in detail in this specification constitute prior art known to those skilled in the art. The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art to which the present invention relates may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope defined by the appended claims.

Claims

1. A methanol distillation removal device, comprising a carbon dioxide absorption tower (1), a first distillation tower (12) and a second distillation tower (14), characterized in that: The air inlet end of the carbon dioxide absorption tower (1) is connected to a natural gas pipeline containing methanol, the bottom end of the carbon dioxide absorption tower (1) is connected to a flash tank (3), the liquid outlet pipeline of the flash tank (3) is connected to a lean-rich liquid heat exchanger (4), the liquid outlet pipeline of the lean-rich liquid heat exchanger (4) is connected to a buffer tank (7), the liquid outlet end of the buffer tank (7) is connected to a natural gas pipeline containing methanol, and a lean liquid pump (2) is fixedly installed in the middle of the liquid outlet pipeline of the buffer tank (7), the top pipeline of the lean-rich liquid heat exchanger (4) is connected to a regeneration tower (5), and the top pipeline of the regeneration tower (5) is connected to a gas-liquid regeneration tower. The regeneration tower (5) and the regeneration gas-liquid separator (10) are fixedly provided with a regeneration gas cooler (9), the regeneration gas-liquid separator (10) is connected to a fraction heat exchanger (11) through a first booster pump (6) pipeline, the fraction heat exchanger (11) is respectively connected to a buffer tank (7) and a first distillation tower (12) pipeline, the first distillation tower (12) pipeline is connected to a tower top condenser (13), the tower top condenser (13) is connected to a second distillation tower (14) pipeline, and the bottom of the second distillation tower (14) is connected to the fraction heat exchanger (11) pipeline through a second booster pump (8).

2. The methanol distillation removal device according to claim 1, characterized in that: Heaters (15) are fixedly installed at the bottoms of the regeneration tower (5), the first distillation tower (12), and the second distillation tower (14).

3. The methanol distillation removal device according to claim 1, characterized in that: The water inlet and outlet of the tower top condenser (13) are both connected to external circulating cooling water via a water pump.

4. The methanol distillation removal device according to claim 1, characterized in that: Pressure detectors are fixedly installed on the front faces of the carbon dioxide absorption tower (1), the regeneration tower (5), the first distillation tower (12), and the second distillation tower (14).

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