Oxamide preparation tail gas treatment device

Abstract

The invention discloses an oxamide preparation tail gas treatment device which comprises a methanol absorption section, a methanol condensation section, an ammonia absorption section and an ammonia absorption raw material preparation section which are sequentially arranged from top to bottom, methanol in gas is absorbed by the methanol absorption section through desalted water, and ammonia in the gas is absorbed by the ammonia absorption section through a methanol solution of dimethyl oxalate. The method comprises the following steps: absorbing unreacted ammonia by using dimethyl oxalate, generating oxamide, returning the oxamide to an oxamide synthesis reactor, condensing methanol steam without ammonia so as to reduce methanol brought out by nitrogen, washing tail gas by using a circulating aqueous solution and desalted water, discharging the tail gas after reaching the standard, and feeding the aqueous solution containing methanol to a sewage treatment device to supplement a carbon source. According to the method, steam does not need to be consumed, only a small amount of cooling water or chilled water needs to be consumed, ammonia in the tail gas is absorbed through reaction of dimethyl oxalate needed in the oxamide production process and ammonia in the tail gas, then methanol in the tail gas is condensed and then returns to a reaction system, and therefore recycling of the ammonia and the methanol is achieved.

Description

Technical Field

[0001] The invention relates to the field of tail gas treatment, and in particular to a tail gas treatment device for oxalamide preparation. Background Art

[0002] Oxamide is an important organic compound. In the agricultural field, it is an efficient slow-release nitrogen fertilizer that can supply the nitrogen elements needed by crops. In the pharmaceutical field, it is an important raw material for synthesizing peptides and proteins, and it is also an important raw material for synthesizing polyamide polymer materials.

[0003] The most promising production method in the industry is to use dimethyl oxalate and ammonia to prepare oxamide. In the process of preparing oxamide by ammonolysis of dimethyl oxalate, in order to ensure the purity of oxamide, an excess of ammonia is required. Therefore, in the subsequent separation and drying process, the tail gas generally contains nitrogen, methanol and ammonia.

[0004] In the existing technical solution, methanol and ammonia are first condensed into liquids, and then separated by distillation. The separated ammonia is compressed and returned to the front-end dimethyl oxalate ammonolysis process to prepare oxalamide, and the separated methanol is sold as a by-product. In this technical solution, the condensation of methanol and ammonia and the top condenser of the ammonia-alcohol distillation need to consume cooling water or chilled water, the bottom reboiler of the ammonia-alcohol distillation needs to consume steam or other heat sources, and the tail gas discharged from the top of the distillation tower needs to be washed again before it can be discharged. Therefore, the existing technical solution has the disadvantages of large equipment investment and high steam and circulating water consumption.

[0005] Therefore, how to overcome the above technical defects is a problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] The purpose of the present invention is to provide an oxalamide preparation tail gas treatment device, which does not require the consumption of steam and only requires the consumption of a small amount of cooling water or chilled water to achieve the recovery and utilization of ammonia and methanol.

[0007] In order to solve the above technical problems, the present invention provides an oxalamide preparation tail gas treatment device, comprising a methanol absorption section, a methanol condensation section, an ammonia absorption section and an ammonia absorption raw material preparation section arranged in sequence from top to bottom, the methanol absorption section absorbs methanol in the gas through desalted water, and the ammonia absorption section absorbs ammonia in the gas through a methanol solution of dimethyl oxalate.

[0008] Preferably, the methanol absorption section includes a first cylinder, an upper head is provided at the upper end of the first cylinder, an isolation tower plate is provided at the lower end of the first cylinder, and a desalted water nozzle, a methanol absorption first filler, a circulating water solution nozzle, a methanol absorption second filler and a riser are arranged in sequence from top to bottom in the first cylinder.

[0009] Preferably, a pipe cap is installed above the riser.

[0010] Preferably, the upper cover is provided with a gas exhaust port, a nitrogen inlet and a pressure gauge port, the first cylinder side wall is provided with a desalted water inlet, a circulating water solution inlet, an overflow port and a circulating water solution outlet in sequence from top to bottom, and the first cylinder side wall is also provided with a first liquid level gauge upper interface, a first liquid level gauge lower interface and a first thermometer interface.

[0011] Preferably, the methanol condensation section comprises a second cylinder and a heat exchange tube bundle and a baffle installed inside the second cylinder, the heat exchange tube bundle is arranged vertically, and a plurality of the baffles are arranged alternately horizontally.

[0012] Preferably, the side wall of the second cylinder is provided with a coolant inlet and a coolant outlet in sequence from top to bottom.

[0013] Preferably, the ammonia absorption section includes a third cylinder, in which a first baffle, a sieve plate tray and a second baffle are arranged, the first baffle is arranged at the upper end of the third cylinder, the second baffle is arranged at the middle end of the third cylinder, and a plurality of sieve plate trays are arranged alternately horizontally.

[0014] Preferably, the side wall of the third cylinder is provided with a dimethyl oxalate methanol liquid inlet, a circulating absorption liquid inlet and an exhaust gas inlet in order from top to bottom.

[0015] Preferably, the ammonia absorption raw material preparation section includes a fourth cylinder, and a liquid guide plate and a partition are arranged in the fourth cylinder. The liquid guide plate is obliquely arranged at the upper end of the fourth cylinder, and the partition is vertically arranged at the lower end of the fourth cylinder.

[0016] Preferably, the side wall of the fourth cylinder located on the left side of the partition is provided with a dimethyl oxalate inlet and a methanol inlet in sequence from top to bottom, the fourth cylinder located on the left side of the partition is provided with a dimethyl oxalate methanol solution outlet, the fourth cylinder located on the right side of the partition is provided with a circulating absorption liquid outlet, the side wall of the fourth cylinder located on the left side of the partition is provided with a second liquid level gauge upper interface, a second thermometer interface and a second liquid level gauge lower interface in sequence from top to bottom, and the side wall of the fourth cylinder located on the right side of the partition is provided with a third liquid level gauge upper interface, a third thermometer interface and a third liquid level gauge lower interface in sequence from top to bottom.

[0017] The invention provides an oxalamide preparation tail gas treatment device, comprising a methanol absorption section, a methanol condensation section, an ammonia absorption section and an ammonia absorption raw material preparation section which are arranged in sequence from top to bottom, the methanol absorption section absorbs methanol in the gas through desalted water, and the ammonia absorption section absorbs ammonia in the gas through a methanol solution of dimethyl oxalate.

[0018] Dimethyl oxalate is used to absorb unreacted ammonia and generate oxalamide, which is returned to the oxalamide synthesis reactor. The methanol vapor after the ammonia is removed is condensed to reduce the methanol carried out by nitrogen. Finally, the tail gas is washed with circulating aqueous solution and desalted water to meet the discharge standards, and the aqueous solution containing methanol is sent to the sewage treatment device to supplement the carbon source. No steam is required, only a small amount of cooling water or chilled water is required. The ammonia in the tail gas is absorbed by the reaction of dimethyl oxalate required in the oxalamide production process with ammonia in the tail gas, and then the methanol in the tail gas is condensed and returned to the reaction system, thereby realizing the recycling of ammonia and methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a specific implementation of the tail gas treatment device for preparing oxamide provided by the present invention. DETAILED DESCRIPTION

[0020] The core of the present invention is to provide an oxalamide preparation tail gas treatment device, which does not require the consumption of steam and only requires the consumption of a small amount of cooling water or chilled water to achieve the recovery and utilization of ammonia and methanol.

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] Please refer to Figure 1 , Figure 1 This is a schematic structural diagram of a specific implementation of the tail gas treatment device for preparing oxamide provided by the present invention.

[0023] A specific embodiment of the present invention provides an oxalamide production tail gas treatment device, comprising a methanol absorption section, a methanol condensation section, an ammonia absorption section and an ammonia absorption raw material preparation section arranged in sequence from top to bottom, the methanol absorption section absorbs methanol in the gas through desalted water, and the ammonia absorption section absorbs ammonia in the gas through a methanol solution of dimethyl oxalate.

[0024] Dimethyl oxalate is used to absorb unreacted ammonia and generate oxalamide, which is returned to the oxalamide synthesis reactor. The methanol vapor after the ammonia is removed is condensed to reduce the methanol carried out by nitrogen. Finally, the tail gas is washed with circulating aqueous solution and desalted water to meet the emission standards. The aqueous solution containing methanol is sent to the sewage treatment device to supplement the carbon source. No steam is required, only a small amount of cooling water or chilled water is required. The ammonia in the tail gas is absorbed by the reaction of dimethyl oxalate required in the oxalamide production process and ammonia in the tail gas, and then the methanol in the tail gas is condensed and returned to the reaction system, thereby realizing the recycling of ammonia and methanol. The absorption effect of ammonia and methanol is good. Ammonia can generate oxalamide fertilizer, and methanol can supplement the carbon source for the sewage treatment device. It is a highly integrated, energy-saving and environmentally friendly waste recycling device.

[0025] In the tail gas treatment device for oxalamide preparation provided in the specific embodiment of the present invention, the methanol absorption section adopts a double-layer packed tower structure, the upper absorption liquid adopts desalted water, and the lower layer adopts circulating water solution, which can save the amount of desalted water while ensuring the absorption effect. It includes a first cylinder 12, an upper head 11 is arranged at the upper end of the first cylinder 12, an isolation tower plate 18 is arranged at the lower end of the first cylinder 12, and a desalted water nozzle 13, a first methanol absorption filler 14, a circulating water solution nozzle 15, a second methanol absorption filler 16 and a riser 17 are arranged in sequence from top to bottom in the first cylinder 12.

[0026] A pipe cap is installed above the riser pipe 17 to prevent the liquid above from flowing downward from the riser pipe 17 to below the isolation tower plate 18 .

[0027] Specifically, the upper head 11 is provided with a gas exhaust port N11, a nitrogen inlet N12 and a pressure gauge port P11, and the side wall of the first cylinder 12 is provided with a desalted water inlet N13, a circulating water solution inlet N14, an overflow port N15 and a circulating water solution outlet N16 from top to bottom, and the side wall of the first cylinder 12 is also provided with a first liquid level gauge upper interface L11, a first liquid level gauge lower interface L12 and a first thermometer interface T11.

[0028] In the oxalamide preparation tail gas treatment device provided in the specific embodiment of the present invention, the methanol condensation section includes a second cylinder 23 and a heat exchange tube bundle 21 and a baffle 22 installed inside the second cylinder 23. The heat exchange tube bundle 21 is arranged vertically and a plurality of baffles 22 are arranged horizontally and alternately.

[0029] Specifically, the side wall of the second cylinder 23 is provided with a coolant inlet N21 and a coolant outlet N22 in sequence from top to bottom.

[0030] In the tail gas treatment device for preparing oxalamide provided in the specific embodiment of the present invention, the ammonia absorption section adopts a multi-layer plate tower, which can effectively prevent blockage. The upper absorption liquid of the ammonia absorption section adopts a relatively pure dimethyl oxalate methanol solution, and the lower layer adopts a circulating absorption liquid, which can improve the absorption effect of ammonia. The ammonia absorption section includes a third cylinder 32, and the third cylinder 32 is provided with a first anti-collision baffle 31, a sieve plate tray 33 and a second anti-collision baffle 34. The first anti-collision baffle 31 is arranged at the upper end of the third cylinder 32, and the second anti-collision baffle 34 is arranged at the middle end of the third cylinder 32. A plurality of sieve plate trays 33 are arranged horizontally and alternately.

[0031] Specifically, the side wall of the third cylinder 32 is provided with a dimethyl oxalate methanol liquid inlet N31, a circulating absorption liquid inlet N32 and an exhaust gas inlet N33 in sequence from top to bottom.

[0032] Based on the oxalamide preparation tail gas treatment device provided in the above-mentioned specific embodiments, the ammonia absorption raw material preparation section includes a fourth cylinder 42, and a liquid guide plate 41 and a partition 43 are arranged in the fourth cylinder 42. The liquid guide plate 41 is obliquely arranged at the upper end of the fourth cylinder 42, and the partition 43 is vertically arranged at the lower end of the fourth cylinder 42.

[0033] Specifically, the side wall of the fourth cylinder 42 located on the left side of the partition 43 is provided with a dimethyl oxalate inlet N41 and a methanol inlet N42 from top to bottom, the fourth cylinder 42 located on the left side of the partition 43 is provided with a dimethyl oxalate methanol solution outlet N43, the fourth cylinder 42 located on the right side of the partition 43 is provided with a circulating absorption liquid outlet N44, the side wall of the fourth cylinder 42 located on the left side of the partition 43 is provided with a second liquid level gauge upper interface L41, a second thermometer interface T41 and a second liquid level gauge lower interface L42 from top to bottom, and the side wall of the fourth cylinder 42 located on the right side of the partition 43 is provided with a third liquid level gauge upper interface L43, a third thermometer interface T42 and a third liquid level gauge lower interface L44 from top to bottom.

[0034] The above interfaces connect corresponding components to achieve smooth flow of fluid and detection of the operating status of the equipment, and the position and layout of each interface can be adjusted according to the situation. Furthermore, the above sections and components to be connected are connected by flanges, and of course, threaded connections or welding can also be used, all of which are within the protection scope of the present invention.

[0035] The tail gas containing methanol and ammonia from the oxalamide synthesis unit enters the lower part of the ammonia absorption section from the N33 port and moves from bottom to top under pressure, and successively contacts the circulating absorption liquid and methanol solution of dimethyl oxalate sprayed from the ammonia absorption and methanol purification sections on the sieve plate. Ammonia reacts with dimethyl oxalate to generate oxalamide. The methanol and nitrogen gas without ammonia continue to move upward, and heat is exchanged with the chilled water in the tube side of the methanol condensation section and the shell side. Most of the methanol in the nitrogen is condensed and flows into the right area at the bottom of the absorption device together with the circulating absorption liquid. The circulating absorption liquid is pumped into the middle part of the ammonia absorption section by the circulating absorption pump for ammonia absorption, and the other part is pumped to the oxalamide synthesis reactor for the reaction of generating oxalamide. The left area at the bottom of the absorption device is the mixing area of ​​dimethyl oxalate and methanol. The mixed dimethyl oxalate and methanol are pumped to the upper part of the ammonia absorption area to absorb ammonia in the tail gas.

[0036] The tail gas from the methanol condensation section enters the methanol absorption section through the riser. The methanol absorption section is a two-stage packed tower. The lower section uses a circulating aqueous solution containing methanol to wash and absorb the methanol tail gas, and the upper section uses desalted water to further remove the methanol in the tail gas until it meets the emission standards.

[0037] Part of the circulating absorption liquid at the bottom of the methanol absorption section is used for washing and absorption of methanol, and part is sent to the sewage treatment device as a carbon source supplement.

[0038] By adjusting the packing height of the methanol absorption tower and the amount of desalted water sprayed, the methanol content in the tail gas can be controlled to meet the prescribed emission standards.

[0039] The above is a detailed introduction to the tail gas treatment device for preparing oxalamide provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. An oxalamide preparation tail gas treatment device, characterized in that: The invention comprises a methanol absorption section, a methanol condensation section, an ammonia absorption section and an ammonia absorption raw material preparation section which are arranged in sequence from top to bottom. The methanol absorption section absorbs methanol in the gas through desalted water, and the ammonia absorption section absorbs ammonia in the gas through a methanol solution of dimethyl oxalate.

2. The tail gas treatment device for preparing oxalamide according to claim 1, characterized in that: The methanol absorption section comprises a first cylinder (12), an upper end of the first cylinder (12) is provided with an upper head (11), a lower end of the first cylinder (12) is provided with an isolation plate (18), and the first cylinder (12) is provided with a desalted water nozzle (13), a first methanol absorption filler (14), a circulating water solution nozzle (15), a second methanol absorption filler (16) and a riser (17) arranged in sequence from top to bottom.

3. The tail gas treatment device for preparing oxalamide according to claim 2, characterized in that: A pipe cap is installed above the riser pipe (17).

4. The tail gas treatment device for oxalamide preparation according to claim 3, characterized in that: The upper end cap (11) is provided with a gas exhaust port (N11), a nitrogen inlet (N12) and a pressure gauge port (P11); the side wall of the first cylinder (12) is provided with a desalted water inlet (N13), a circulating water solution inlet (N14), an overflow port (N15) and a circulating water solution outlet (N16) in order from top to bottom; the side wall of the first cylinder (12) is also provided with a first liquid level gauge upper interface (L11), a first liquid level gauge lower interface (L12) and a first thermometer interface (T11).

5. The tail gas treatment device for oxalamide preparation according to claim 1, characterized in that: The methanol condensation section comprises a second cylinder (23) and a heat exchange tube bundle (21) and a baffle (22) installed inside the second cylinder (23); the heat exchange tube bundle (21) is arranged vertically, and a plurality of the baffles (22) are arranged alternately horizontally.

6. The tail gas treatment device for oxalamide preparation according to claim 5, characterized in that: The side wall of the second cylinder (23) is provided with a cooling liquid inlet (N21) and a cooling liquid outlet (N22) in sequence from top to bottom.

7. The tail gas treatment device for oxalamide preparation according to claim 1, characterized in that: The ammonia absorption section comprises a third cylinder (32), wherein a first impact baffle (31), a sieve plate tray (33) and a second impact baffle (34) are arranged in the third cylinder (32), wherein the first impact baffle (31) is arranged at the upper end of the third cylinder (32), and the second impact baffle (34) is arranged at the middle end of the third cylinder (32), and a plurality of sieve plate trays (33) are arranged alternately horizontally.

8. The tail gas treatment device for oxalamide preparation according to claim 7, characterized in that: The side wall of the third cylinder (32) is provided with a dimethyl oxalate methanol liquid inlet (N31), a circulating absorption liquid inlet (N32) and an exhaust gas inlet (N33) in sequence from top to bottom.

9. The tail gas treatment device for oxalamide preparation according to any one of claims 1 to 8, characterized in that: The ammonia absorption raw material preparation section comprises a fourth cylinder (42), wherein a liquid guide plate (41) and a partition plate (43) are arranged inside the fourth cylinder (42), wherein the liquid guide plate (41) is arranged obliquely at the upper end of the interior of the fourth cylinder (42), and the partition plate (43) is arranged vertically at the lower end of the interior of the fourth cylinder (42).

10. The tail gas treatment device for oxalamide preparation according to claim 9, characterized in that: The side wall of the fourth cylinder (42) located on the left side of the partition (43) is provided with a dimethyl oxalate inlet (N41) and a methanol inlet (N42) in order from top to bottom; the fourth cylinder (42) located on the left side of the partition (43) is provided with a dimethyl oxalate methanol solution outlet (N43); the fourth cylinder (42) located on the right side of the partition (43) is provided with a circulating absorption liquid outlet (N44); the side wall of the fourth cylinder (42) located on the left side of the partition (43) is provided with a second liquid level gauge upper interface (L41), a second thermometer interface (T41) and a second liquid level gauge lower interface (L42) in order from top to bottom; the side wall of the fourth cylinder (42) located on the right side of the partition (43) is provided with a third liquid level gauge upper interface (L43), a third thermometer interface (T42) and a third liquid level gauge lower interface (L44) in order from top to bottom.

Images