Process for removing acid gas from ammonia-containing condensate and recovering ammonia

Abstract

The present invention discloses a process for removing acid gas from ammonia-containing condensate and recovering ammonia. The process includes concentrating ammonia-containing vapor, removing acid gas, recovering ammonia gas from a side-line, refining ammonia, and producing an ammonia product. The process reduces the acid gas removal load of the pressurized stripping tower and the acid gas removal tower, lowering the risk of acidic media corrosiveness on metal equipment and pipelines. The process significantly reduces initial investment and operating costs. The process eliminates the environment in which ammonium carbamate is generated, completely resolving equipment corrosion issues. The acid gas content in the ammonia gas from the side-line is low, simplifying the process and preventing ammonium salt crystallization from clogging heat exchange equipment. The process of step-by-step pressure reduction, cooling, and washing dissolves hydrogen sulfide and carbon dioxide in the ammonia gas in the condensate of each pressure-reducing separator in an ionic state, allowing the saturated ammonia gas to flash evaporate from the condensate, thereby producing ammonia gas of higher purity.

Description

Technical Field

[0001] The present invention relates to coal chemical technology, in particular to a process for removing acid gas and recovering ammonia from ammonia-containing condensate purified by a carbon monoxide conversion device for raw gas in production. Background Art

[0002] In the coal chemical industry, the condensate generated during the carbon monoxide shift process in feed gas purification plants contains volatile weak electrolytes such as CO2, H2S, and NH3. CO2 and H2S are acidic substances that corrode metal equipment and pipelines within the production plant. The presence of ammonia can cause ammonia salts of CO2 and H2S to crystallize, clogging pipelines and equipment. Furthermore, excessive ammonia nitrogen levels in the system increase the difficulty and cost of treating ammonia nitrogen in the gasification plant's black water. If not promptly treated, this can cause significant environmental damage.

[0003] At present, the treatment of the condensate in China mainly adopts the single-tower stripping and double-tower stripping methods:

[0004] Single-tower stripping removes acid gases and ammonia from the condensate, followed by cooling and separation. After cooling and separation, the acid gases are sent to a flare or Claus sulfur recovery system, while the condensate is sent to flue gas desulfurization or wastewater treatment. The operating pressure of this tower is 0.3-0.5 MPa(g).

[0005] Double-tower stripping: The shift condensate is first fed to the first stripping tower. Acid gas removed from the top of the tower is sent to sulfur recovery, and ammonia-containing condensate from the bottom of the tower is sent to the second stripping tower. Acid gas removed from the top of the second stripping tower is sent to sulfur recovery, while the bottom of the tower is sent to the gasification island. Side-stream ammonia is subjected to three stages of condensation and deep condensation desulfurization to produce aqueous ammonia. The top operating pressure of the first stripping tower is ~0.3 MPa(g), the top temperature is ~40°C, and the bottom temperature is ~140°C. The operating pressure of the second stripping tower is ~0.5 MPa(g), the top operating temperature is ~50°C, and the bottom operating temperature is ~158°C.

[0006] The above process methods have the following problems:

[0007] In the single-tower stripping process, the acid gas at the top of the stripping tower is around 130°C and contains a certain amount of saturated water. After cooling, ammonium salts such as NH4HS, (NH4)2S, NH4HCO3, and (NH4)2CO3 crystals form, clogging the cooler's heat exchange tubes. Simultaneously, the reducing agent ammonium carbamate (NH2COONH4) forms, damaging the oxide film, the protective layer on the metal surface. Without protection, the metal quickly corrodes, causing damage to equipment and piping. The acid gas after cooling and separation contains ammonia, typically at levels between 3,000 and 10,000 ppm. This is then sent to a flare or Claus sulfur recovery system for combustion. During the combustion process, ammonia is converted into nitrogen oxides, which are carcinogenic and are released into the atmosphere, seriously polluting the environment.

[0008] After separation, the ammonia condensate is sent to flue gas desulfurization (FGD) or wastewater treatment. Because the condensate contains H2S and NH3, with H2S concentrations ranging from ~2000ppm and NH3 concentrations ranging from ~30,000ppm, sending it to wastewater treatment increases the wastewater treatment load and has a significant impact on the environment. Sending it to FGD, due to the high H2S content in the ammonia, will cause elemental sulfur to precipitate, clogging the FGD and denitrification packing and rendering the system inoperable.

[0009] The main reason is that the separation depth of ammonia and acid gas is not enough, the acid gas removed by steam contains ammonia, and the ammonia condensate contains acid gas.

[0010] Problem 1 of the dual-tower stripping process: The bottom liquid volume of the first stripper is almost equal to the amount of converted condensate, which is fed to the second stripper. Because the condensate is not converted, the heat load of the second stripper remains high, resulting in high steam consumption and operating costs. Furthermore, the equipment is large, requiring a significant initial investment.

[0011] Problem 2 of the dual-tower stripping process: Incomplete separation of ammonia and acid gases occurred in both strippers 1# and 2#. Ammonia and acid gases coexisted, generating ammonium carbamate (NH2COONH4), which corroded equipment and piping. Both strippers 1# and 2# were constructed of stainless steel, with options including S30403, S31603, S32168, and S22053. Titanium was also used, increasing project costs.

[0012] Problem 3 of the dual-tower stripping process: Both strippers 1 and 2 remove acid, and the acid gas contains a high amount of ammonia. The separation of ammonia and acid gas is incomplete, and no secondary separation treatment is performed. The acid gas is flared or sent to Claus sulfur recovery, generating nitrogen oxides, polluting the environment, and wasting ammonia.

[0013] Problem 4 of the double-tower stripping process: The hydrogen sulfide content of the ammonia produced from the side line of the 2# stripping tower is high, the refining process of the ammonia produced from the side line is complex, the deep condensation desulfurization consumption is high, and the operating cost is high. Summary of the Invention

[0014] The purpose of the present invention is to solve the problems existing in the recovery of conversion condensate due to the superposition of ammonia and acid gas circulation, which leads to blockage and corrosion of equipment and pipelines, incomplete treatment, and poor washing effect of low-temperature methanol. The present invention provides a process for removing acid gas from ammonia-containing condensate and recovering ammonia. The process has the advantages of complete removal of acid gas, high purity of recovered ammonia, no corrosion of equipment and pipelines, no crystallization blocking equipment and pipelines, complete removal of ammonia and acid gas from the treated condensate, low energy consumption, small equipment specifications and low investment.

[0015] The above technical problems of the present invention are mainly solved by the following technical solution: a process for removing acid gas and recovering ammonia from ammonia-containing condensate, which is characterized by comprising the following steps and contents:

[0016] (1) Ammonia-containing vapor condensation

[0017] A. Send the high-pressure condensate into the flash tank to flash out part of the acid gas and non-condensable gas and send them to sulfur recovery.

[0018] B. The condensate after flash evaporation is heated through a temperature-raising heat exchanger, and the temperature is raised to 80℃~100℃ before entering the upper part of the pressurized stripping tower.

[0019] C. Acid gas, non-condensable gas, ammonia and saturated water vapor are taken out from the top of the pressurized stripping tower at 133℃~140℃ and directly enter the acid gas removal tower. The mass ratio of ammonia gas is 0.08~0.12 times that of the conversion condensate.

[0020] D. The pressurized stripping tower kettle obtains clean condensate at ~138℃, including NH3≤50ppm, H2S≤10ppm, which is then sent to the gasification island.

[0021] (2) Removal of acid gas

[0022] The ammonia-containing acid gas from the top of the pressurized stripping tower and the acid gas taken out from the top of the ammonia recovery tower enter the tower together from the bottom of the acid gas removal tower:

[0023] E. The acid gas removal tower bottom liquid is pressurized by the bottom liquid pump, heated by the temperature-raising heat exchanger, and then discharged in two ways after the cooling of the bottom liquid: one way is cooled to room temperature by circulating water in cooler 1, and then enters the middle part of the acid gas removal tower as the washing liquid of the acid gas removal tower for circulating cooling and washing; the other way is sent to the ammonia recovery tower as the recovery liquid for recovering ammonia; wherein, the mass ratio of the circulating cooling washing liquid in the middle part of the acid gas removal tower to the recovery liquid of the ammonia recovery tower is: 2.0-4.0;

[0024] F. The top of the acid gas removal tower uses an ammonia recovery tower. The clean condensate from the bottom of the tower is cooled to room temperature through the heat recovery device 2 and the cooler 2 for cooling and washing.

[0025] G. The acid gas and non-condensable gas removed from the top of the acid gas removal tower are sent to sulfur recovery, and the NH3 in the removed acid gas is ≤100ppm.

[0026] (3) Side-line ammonia recovery

[0027] H. The recovered liquid from the bottom of the acid gas removal tower is sequentially heat-exchanged with the ammonia recovery tower side line with saturated water vapor in the universal heat recovery device 1 to recover heat, and then with the ammonia recovery tower bottom condensate universal heat recovery device 2 to recover heat.

[0028] The tower bottom is heated by steam greater than 1.0MPa(g), including direct steam entry into the tower and heating by a reboiler outside the tower; the top of the ammonia recovery tower uses the clean condensate from the tower bottom of the ammonia recovery tower to pass through heat recovery device 2 and cooler 2 to cool to room temperature for cooling and washing.

[0029] I. The ammonia-containing gas taken out from the top of the ammonia recovery tower is sent to the acid gas removal tower for circulation to remove the acid gas and recover the ammonia.

[0030] J. The condensate taken out from the bottom of the ammonia recovery tower recovers heat through the heat recovery device 2. A portion of it is cooled to room temperature through the cooler 2 and used as the top washing liquid of the acid gas removal tower and the ammonia recovery tower. The rest is sent to the gasification island. The NH3 content of the condensate is ≤50ppm and the H2S content is ≤10ppm.

[0031] K. The ammonia gas with a certain amount of saturated water vapor produced by the side line passes through the heat recovery device 1 and is cooled by heat exchange with the tower bottom recovery liquid of the acid gas removal tower before entering step 4.

[0032] (4) Ammonia refining

[0033] L. After heat exchange in the heat recovery device 1, the ammonia gas extracted from the side line of the ammonia recovery tower is reduced in pressure to ~0.25MPa(g) and enters the pressure-reducing washing separator 1. The ammonia gas after cooling and flashing in the pressure-reducing washing separator 1 is first washed by bubbling with the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas.

[0034] M. After washing, the flashed ammonia gas in the pressure-reducing washing separator 1 enters the cooler 3 and is cooled to ~110°C. The pressure is reduced to ~0.15MPa(g) and the ammonia gas enters the pressure-reducing washing separator 2. The flashed ammonia gas is cooled in the pressure-reducing washing separator 2 and is first washed by bubbling of the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas.

[0035] N. The ammonia gas flashed in the pressure-reducing washing separator 2 after washing enters the cooler 4 and is cooled to room temperature. The pressure is reduced to ~0.05MPa(g) and enters the pressure-reducing bubbling separator. The ammonia gas after flashing is cooled in the separator and washed by bubbling with the condensate in the separator. The ammonia gas flashed in the pressure-reducing bubbling separator after bubbling washing is sent to the ammonia absorber in step five.

[0036] O. The condensate from pressure-reducing washing separator 1, pressure-reducing washing separator 2 and pressure-reducing bubbling separator is pressurized by a centrifugal pump and sent to an ammonia recovery tower for circulation treatment after separation.

[0037] (5) Ammonia product production

[0038] The ammonia gas flashed from the pressure-reducing bubble separator enters the ammonia absorber and is mixed with desalted water to produce ammonia water, in which H2S is ≤10ppm.

[0039] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, in step (1), the ammonia-containing gas is concentrated, the acid gas and ammonia in the conversion condensate are simultaneously extracted in a pressurized stripping tower and sent to step (2) for treatment.

[0040] In the aforementioned process for removing acid gases from ammonia-containing condensate and recovering ammonia, in step (1) B, the condensate after flash evaporation is simultaneously heat-exchanged with the bottom liquid of the acid gas removal tower in step (2) through a temperature-raising heat exchanger, and the temperature is raised to 80°C to 100°C before being input from the upper part of the pressurized stripping tower.

[0041] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, in step (1) B, the pressurized stripping tower is operated at a pressure of 0.2 MPa(g) to 0.3 MPa(g), and the tower bottom is directly heated by 0.5 MPa(g) low-pressure steam.

[0042] In the aforementioned process for removing acid gas and recovering ammonia from an ammonia-containing condensate, in step (2), the acid gas and ammonia are separated in the acid gas removal tower by controlling the operating environment conditions to influence the changing trends of the ionization equilibrium and the solubility equilibrium, so that the acid gas and ammonia are not simultaneously enriched in the same area, thereby eliminating the formation of ammonium carbamate.

[0043] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, in step (2), the top of the acid gas removal tower is operated at a pressure of 0.13 MPa(g) to 0.16 MPa(g); the bottom of the tower is operated at a temperature of 110°C to 120°C, and the top of the tower is operated at a temperature of 40°C to 50°C.

[0044] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, in step (iii), the acid gas containing a small amount of gaseous ammonia taken out from the top of the ammonia recovery tower is returned to the acid gas removal tower in step (ii), where the acid gas and ammonia are again subjected to stripping separation to remove the acid gas, leaving the ammonia in the bottom of the tower; and the ammonia condensate containing a small amount of acid gas in the bottom of the acid gas removal tower in step (ii) is sent to the ammonia recovery tower in step (iii), and ammonia is produced as a side line.

[0045] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, the acid gas removed from the top of the acid gas removal tower has a low ammonia content, with a mass concentration of ≤100 ppm, and the removed acid gas is sent to sulfur recovery; the vapor ammonia removed from the side line of the ammonia recovery tower contains acid gas with a hydrogen sulfide content of ≤300 ppm and a carbon dioxide content of ≤1000 ppm, and is sent to step (iv) for ammonia refining.

[0046] In the aforementioned process for removing acid gas from ammonia-containing condensate and recovering ammonia, in step (iii), the recovered liquid after its temperature is raised to 140°C to 150°C is fed from the upper part of the ammonia recovery tower; the operating pressure at the top of the ammonia recovery tower is 0.5 MPa(g); the operating temperature of the tower bottom is 158°C to 165°C, and the operating temperature of the tower top is 55°C to 65°C; the temperature of the ammonia produced from the side line is 148°C to 152°C.

[0047] The above-mentioned process for removing acid gas from amino acid-containing condensate and recovering ammonia is as follows: in step (4), the ammonia produced from the side line of the ammonia recovery tower in step (3) is subjected to a first-stage cooling and pressure reduction, then a second-stage cooling and pressure reduction, and a condensate circulation washing in a washing separator; then a third-stage cooling and pressure reduction, and a bubbling washing in a washing separator; the acid gas carbon dioxide and hydrogen sulfide that escaped without being dissolved in the condensate are again dissolved in the separated condensate; the condensate after the circulation washing is sent to the ammonia recovery tower in step (3) to remove the acid gas again and recover the ammonia; after the three-stage cooling and pressure reduction washing, the gaseous ammonia is cooled to room temperature and enters a pressure-reducing bubbling separator for bubbling separation to obtain high-purity ammonia separated by flash evaporation, which is sent to step (5) to prepare ammonia water.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. Design the conditions for the high-pressure shift condensate to enter the pressure-reducing flash tank: flash off the non-condensable gas and some acid gas dissolved in the condensate under the high-pressure conditions of the shift reaction, reduce the acid gas removal load of the pressurized stripping tower and the acid gas removal tower, and reduce the risk of acidic medium corrosion on metal equipment and pipelines.

[0050] 2. A pressurized stripping tower is used to completely remove the acid gases and ammonia from the shift condensate. Qualified purified water (NH3 ≤ 50 ppm, H2S ≤ 10 ppm) is sent to a gasification unit at the bottom of the tower. Concentrated ammonia-containing ammonia-containing gas is obtained at the top of the tower and sent to the next step, where an acid gas removal tower separates the acid gases from the ammonia. Because the mass of the ammonia-containing ammonia-containing gas treated is only 0.08 to 0.12 times that of the shift condensate, the equipment specifications and heat load of the acid gas removal tower and ammonia recovery tower are significantly reduced, significantly reducing initial investment and operating costs. The diameter of the acid gas removal tower is also significantly reduced, to only approximately 0.32 times the cross-sectional area of ​​the stripping tower in a conventional double-tower stripping system.

[0051] 3. The removal of acid gas utilizes the principle that ionization equilibrium and solubility equilibrium change with the change of environmental conditions; when the temperature of the ammonium salt formed by the acidic medium H2S, CO2 and NH3 in the aqueous solution rises from room temperature to 125℃, the ionization equilibrium constant changes from large to small; when it exceeds 125℃, the ionization equilibrium constant changes from small to large; the solubility of H2S, CO2 and NH3 in water decreases with the increase of temperature; the operating pressure of the acid gas removal tower is controlled at 0.15MPa(g), and the operating temperature of the lower part of the tower is controlled at 80℃~130℃; in the acid gas removal tower, the acid gas H2S and CO2 are removed from the top of the tower, and NH3 remains in the bottom of the tower. The acid gas and ammonia are separated to the greatest extent, and CO2 and NH3 are not enriched in the same area at the same time, thus avoiding the formation of ammonium carbamate (NH2COONH4) with reducing properties. Because ammonium carbamate has strong reducing properties, it will destroy the oxide film on the surface of metal equipment and pipelines, thereby corroding the equipment and pipelines. Since there is no environment for ammonium carbamate to be generated, the equipment corrosion problem is completely solved, and the material of the acid removal tower can be ordinary stainless steel S30408.

[0052] 4. Since the equipment corrosion problem has been completely solved, the upper section of the ammonia recovery tower can be made of ordinary stainless steel S30408, and the lower section can be made of carbon steel. The one-time investment cost of the double towers is reduced by about 50%.

[0053] 5. Step 2 mainly removes acid gas, and step 3 mainly produces ammonia: the acid gas containing a small amount of ammonia taken out from the top of the ammonia recovery tower is returned to the acid gas removal tower in step 2, and the acid gas and ammonia are stripped and separated again to remove the acid gas and recover ammonia; the ammonia condensate containing less acid gas in the bottom of the acid gas removal tower in step 2 is sent to the ammonia recovery tower in step 3, and ammonia is produced in the side line; the acid gas taken out from the top of the acid gas removal tower has low ammonia content, with a mass concentration of only less than 100ppm, and the removed acid gas is sent to the sulfur Sulfur recovery; the acid gas content in the steam ammonia produced from the side line of the ammonia recovery tower is very low, with the mass concentration of hydrogen sulfide content less than 300ppm and the mass concentration of carbon dioxide content less than 1000ppm; while the acid gas content in the ammonia produced from the side line of conventional double-tower stripping on the market is above 1000ppm. The steam ammonia produced from the side line requires three-stage condensation separation and low-temperature sulfur solidification purification to remove the acidic medium. Not only is the process complicated, but the treatment process may also cause ammonium salt crystals to block the heat exchange equipment.

[0054] 6. Ammonia extracted from the side line of the refined ammonia recovery tower is produced using a two-stage decompression condensation separation and circulation washing method: Utilizing the principle that ammonia's solubility in water decreases as pressure decreases and increases as temperature decreases, the ammonia extracted from the side line of the ammonia recovery tower at ~140°C is decompressed to ~0.25 MPa(g) after heat exchange in heat recovery unit 1 and enters decompression washing separator 1. The ammonia flashed in decompression washing separator 1 enters cooler 3, where its temperature is reduced to ~110°C and decompressed to ~0.15 MPa(g) before entering decompression washing separator 2. Condensate is recycled and washed in the second-stage decompression separator to dissolve the acidic gases carbon dioxide and hydrogen sulfide that escape without being dissolved in the condensate again in the separated condensate, thereby making the ammonia separated in the gas phase by the decompression separator purer. After the cyclic washing, the condensate is returned to the ammonia recovery tower to remove the acidic gases and recover the ammonia. At the same time, the ammonia gas flashed from the pressure-reducing washing separator 2 enters the cooler 4 and is cooled to room temperature, and then is reduced in pressure to ~0.05 MPa(g) before entering the pressure-reducing bubbling separator. During the step-by-step pressure reduction, temperature reduction, and washing process, hydrogen sulfide and carbon dioxide in the ammonia gas dissolve in the condensate of each level of the pressure-reducing separator and appear in the ionic state. The ammonia gas that has reached saturation of solution flashes and escapes from the condensate, thereby obtaining ammonia gas with higher purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention is a schematic flow diagram of a process for removing acid gas from condensate and recovering ammonia. DETAILED DESCRIPTION

[0056] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0057] This embodiment provides a process for removing acid gas from ammonia-containing condensate and recovering ammonia, such as Figure 1As shown, the equipment includes a pressure-reducing flash tank, a temperature-raising heat exchanger, a pressurized stripping tower, an acid gas removal tower, a cooler 1, an ammonia recovery tower, a heat recovery device 1, a heat recovery device 2, a cooler 2, a pressure-reducing washing separator 1, a cooler 3, a pressure-reducing washing separator 2, a cooler 4, a pressure-reducing bubbling separator, an ammonia absorber, etc.

[0058] Including the following steps and contents:

[0059] Step 1: Concentration of Acid-Containing Steam

[0060] The high-pressure condensate from the conversion is fed into a 0.4 MPa(g) flash tank, where some acid gases and non-condensable gases are flashed off and sent to sulfur recovery. The flashed condensate and the acid gas removal tower bottoms are heated to 80°C-100°C via a temperature-raising heat exchanger before entering the top of a pressurized stripping tower. The pressurized stripping tower operates at a pressure of 0.2 MPa(g)-0.3 MPa(g). The bottoms of the towers are heated directly by 0.5 MPa(g) low-pressure steam (including indirect reboiler heating). Acid gases, non-condensable gases, ammonia, and saturated water vapor are withdrawn from the top of the tower at 133°C-140°C and fed directly to the acid gas removal tower. The mass ratio of ammonia-containing vapor is 0.08-0.12 times that of the conversion condensate. Clean condensate (NH3≤50ppm, H2S≤10ppm) at a temperature of ~138°C (NH3≤50ppm, H2S≤10ppm) is generated in the bottoms of the pressurized stripping tower and sent to the aeration island.

[0061] In this step, the high-pressure condensate from the conversion is sent to a 0.4 MPa(g) flash tank to flash out some of the acid gas and non-condensable gas and send them to sulfur recovery, thereby reducing the acid gas removal load of the pressurized stripping tower and the acid gas removal tower, and at the same time reducing the risk of corrosion of metal equipment and pipelines by the acidic medium.

[0062] Step 2: Removal of acid gas

[0063] The ammonia-containing steam from the top of the pressurized stripping tower and the acid gas taken out from the top of the ammonia recovery tower enter the bottom of the acid gas removal tower together. The top of the acid gas removal tower operates at a pressure of 0.13MPa(g) to 0.16MPa(g); the bottom of the tower operates at a temperature of 110℃ to 120℃, and the top of the tower operates at a temperature of 40℃ to 50℃.

[0064] The acid gas removal tower bottoms liquid is pressurized by a bottoms liquid pump and heated through a temperature-raising heat exchanger to become the feed liquid for the pressurized stripping tower. A portion of the cooled bottoms liquid is then cooled to room temperature by circulating water in cooler 1 and fed into the middle section of the acid gas removal tower as scrubber for a circulating cooling wash. The remaining bottoms liquid, after passing through the temperature-raising heat exchanger, is sent as recovered liquid to the ammonia recovery tower for ammonia recovery. The top of the acid gas removal tower uses clean condensate from the ammonia recovery tower bottoms, which is cooled to room temperature in heat recovery unit 2 and cooler 2 for cooling wash. The mass ratio of the circulating cooling wash liquid in the middle section of the acid gas removal tower to the recovered liquid from the ammonia recovery tower is 2.0-4.0.

[0065] The acid gas and non-condensable gas removed from the top of the acid gas removal tower are sent to sulfur recovery, and the NH3 in the removed acid gas is ≤100ppm.

[0066] Step 3: Side-line ammonia recovery

[0067] The recovered liquid from the acid gas removal tower's bottoms is sequentially exchanged with heat recovery unit 1, which extracts saturated steam from the ammonia recovery tower's sidestream, and then with heat recovery unit 2, which extracts heat from the bottoms of the ammonia recovery tower's condensate. After reaching a temperature of 140°C to 150°C, the recovered liquid is fed into the top of the ammonia recovery tower. The operating pressure at the top of the ammonia recovery tower is approximately 0.5 MPa(g), with the bottom operating temperature at 158°C to 165°C and the top operating temperature at 55°C to 65°C. The temperature of the sidestream ammonia is 148°C to 152°C. The bottoms are heated with steam at a pressure exceeding 1.0 MPa(g), both directly into the tower and via an external reboiler. Clean condensate from the bottoms of the ammonia recovery tower is cooled to ambient temperature in heat recovery unit 2 and then cooled to ambient temperature in cooler 2 for washing.

[0068] The ammonia-containing gas taken out from the top of the ammonia recovery tower is sent to the acid gas removal tower for circulation to remove the acid gas and recover the ammonia.

[0069] The condensate taken out from the bottom of the ammonia recovery tower recovers heat through the heat recovery device 2. A portion of it is cooled to room temperature through the cooler 2 and used as the top washing liquid of the acid gas removal tower and the ammonia recovery tower. The rest is sent to the gasification island. The NH3 content of the condensate is ≤50ppm and the H2S content is ≤10ppm.

[0070] The ammonia gas with a certain amount of saturated water vapor produced by the side line passes through the heat recovery device 1 and is cooled by heat exchange with the tower bottom recovery liquid of the acid gas removal tower before entering the ammonia refining step.

[0071] In the above steps 2 and 3, the acid gas is taken out from the top of the ammonia recovery tower and sent back to the acid gas removal tower for recycling to remove the acid gas. The acid gas removal tower is only focused on removing the acid gas, and the ammonia recovery tower is only focused on recovering ammonia.

[0072] Step 4: Ammonia Refining

[0073] After heat exchange in heat recovery unit 1, the ammonia gas extracted from the side line of the ammonia recovery tower at ~140°C is depressurized to ~0.25 MPa(g) and enters pressure-reducing washing separator 1. The ammonia gas after cooling and flashing in pressure-reducing washing separator 1 is first washed by bubbling with the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas. The flashed ammonia gas from pressure-reducing washing separator 1 enters cooler 3, where the temperature is reduced to ~110°C, and the pressure is reduced to ~0.15 MPa(g) before entering pressure-reducing washing separator 2. The ammonia gas after cooling and flashing in the separator is first washed by bubbling with the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas. The ammonia gas flashed through the pressure-reducing washing separator 2 enters the cooler 4 and is cooled to room temperature, and then is reduced in pressure to ~0.05 MPa (g) and enters the pressure-reducing bubbling separator. The ammonia gas after flashing is cooled in the separator and is washed by bubbling with the condensate in the separator. The ammonia gas flashed through the pressure-reducing separator after bubbling washing is sent to the ammonia absorber in step five.

[0074] The condensate from the pressure-reducing washing separator 1, the pressure-reducing washing separator 2 and the pressure-reducing bubbling separator is pressurized by a centrifugal pump and sent to an ammonia recovery tower for circulation treatment after separation.

[0075] In this step, the side-line ammonia gas is produced by step-by-step pressure reduction and temperature reduction, and the ammonia condensate is circulated and washed to remove the residual acid gas of the ammonia gas.

[0076] Step 5: Preparation of ammonia products

[0077] The ammonia gas flashed from the pressure-reducing bubble separator enters the ammonia absorber and is mixed with desalted water to produce the required ammonia water, in which H2S is ≤10ppm.

[0078] After actual testing, the main indicator data of this embodiment and the prior art are shown in Table 1.

[0079] Table 1: Main indicators of the application example of this embodiment compared with the prior art

[0080]

[0081]

[0082] All technical means not described in the present invention are existing technologies well known to those skilled in the art.

[0083] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Without departing from the principles of the present technical solution, any equivalent changes or equivalent modifications made in accordance with the technical ideas proposed in the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A process for removing acid gas from ammonia-containing condensate and recovering ammonia, characterized by comprising the following steps: And content: (1) Ammonia-containing vapor concentration A. Send the high-pressure condensate into the flash tank to flash out part of the acid gas and non-condensable gas and send them to sulfur recovery; B. The condensate after flash evaporation is heated through a temperature-raising heat exchanger, and the temperature rises to 80℃~100℃ before entering the upper part of the pressurized stripping tower; C. Acid gas, non-condensable gas, ammonia and saturated water vapor are taken out from the top of the pressurized stripping tower at 133℃~140℃ and directly enter the acid gas removal tower. The mass ratio of ammonia gas is 0.08~0.12 times of the conversion condensate. D. The pressurized stripping tower kettle obtains clean condensate at 138°C, including NH3≤50ppm, H2S≤10ppm, and is sent to the gasification island; (2) Removal of acid gas The ammonia-containing acid gas from the top of the pressurized stripping tower and the acid gas taken out from the top of the ammonia recovery tower enter the tower together from the bottom of the acid gas removal tower: E. The acid gas removal tower bottom liquid is pressurized by the tower bottom liquid pump, and is heated by the temperature-raising heat exchanger to be the feed liquid of the pressurized stripping tower. After cooling the tower bottom liquid, it is output in two ways: one way is cooled to room temperature by circulating water in cooler 1, and then enters the middle part of the acid gas removal tower as the washing liquid of the acid gas removal tower for circulating cooling and washing; One path is sent to the ammonia recovery tower as the recovery liquid for ammonia recovery; wherein, the mass ratio of the circulating cooling washing liquid in the middle of the acid gas removal tower to the recovery liquid of the ammonia recovery tower is: 2.0-4.0; F. The top of the acid gas removal tower uses an ammonia recovery tower. The clean condensate from the tower kettle is cooled to room temperature through a heat recovery device 2 and a cooler 2 for cooling and washing. G. The acid gas and non-condensable gas removed from the top of the acid gas removal tower are sent to sulfur recovery, and the NH3 in the removed acid gas is ≤100ppm; (3) Side-line ammonia recovery H. The recovered liquid from the bottom of the acid gas removal tower is sequentially heat-exchanged with the ammonia recovery tower side line with saturated water vapor by the universal heat recovery device 1 to recover heat, and then heat-exchanged with the ammonia recovery tower bottom condensate universal heat recovery device 2 to recover heat; The tower kettle is heated by steam with a G of greater than 1.0 MPa, including direct steam into the tower and heating by a reboiler outside the tower; the top of the ammonia recovery tower uses the clean condensate from the ammonia recovery tower kettle to pass through heat recovery device 2 and cooler 2 to cool to room temperature for cooling and washing; I. The ammonia-containing gas taken out from the top of the ammonia recovery tower is sent to the acid gas removal tower for circulation to remove the acid gas and recover ammonia; J. The condensate taken out from the bottom of the ammonia recovery tower is sent to the heat recovery device 2 to recover heat. A portion of it is cooled to room temperature by the cooler 2 and used as the top washing liquid of the acid gas removal tower and the ammonia recovery tower. The rest is sent to the gasification island. The NH3 content of the condensate is ≤50ppm and the H2S content is ≤10ppm. K. The ammonia gas with a certain amount of saturated water vapor produced by the side line passes through the heat recovery device 1 and is cooled by heat exchange with the tower bottom recovery liquid of the acid gas removal tower before entering step (IV); (4) Ammonia refining L. After heat exchange in the heat recovery device 1, the ammonia gas extracted from the side line of the ammonia recovery tower is decompressed to 0.25 MPaG and enters the pressure-reducing washing separator 1. The ammonia gas after cooling and flash evaporation in the pressure-reducing washing separator 1 is first washed by bubbling of the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas; M. After washing, the flashed ammonia gas in the pressure-reducing washing separator 1 enters the cooler 3 and is cooled to 110°C. The pressure is reduced to 0.15 MPaG and enters the pressure-reducing washing separator 2. The flashed ammonia gas is cooled in the pressure-reducing washing separator 2 and is first washed by bubbling with the condensate in the separator, and then washed by the condensate circulating packing in the separator to remove the residual hydrogen sulfide in the ammonia gas. N. The ammonia gas flashed in the pressure-reducing washing separator 2 after washing enters the cooler 4 and is cooled to room temperature. The pressure is reduced to 0.05 MPaG and enters the pressure-reducing bubbling separator. The ammonia gas after flashing is cooled in the separator and washed by bubbling with the condensate in the separator. The ammonia gas flashed in the pressure-reducing bubbling separator after bubbling washing is sent to the ammonia absorber in step (V); O, the condensate of pressure-reducing washing separator 1, pressure-reducing washing separator 2, and pressure-reducing bubbling separator is pressurized by a centrifugal pump and sent to the ammonia recovery tower for circulation treatment; (V) Ammonia product production The ammonia gas flashed from the pressure-reducing bubble separator enters the ammonia absorber and is mixed with desalted water to produce ammonia water, in which H2S is ≤10ppm.

2. The process for removing acid gas from amino acid-containing condensate and recovering ammonia according to claim 1, characterized in that: In step (1), the concentrated amino acid-containing gas, the acid gas and ammonia in the conversion condensate are simultaneously and completely extracted in a pressurized stripping tower and sent to step (2) for treatment.

3. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 1, characterized in that: In step (1) B, the condensate after flash evaporation is simultaneously heated together with the bottom liquid of the acid gas removal tower in step (2) through a temperature-raising heat exchanger, and the temperature is raised to 80°C to 100°C before being input from the upper part of the pressurized stripping tower.

4. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 1, characterized in that: In step (1) B, the pressurized stripping tower is operated at a pressure of 0.2 MPaG to 0.3 MPaG, and the tower kettle adopts 0.5 MPaG low-pressure steam to directly enter the tower for heating.

5. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 1, characterized in that: In step (ii), the acid gas and ammonia are separated in the acid gas removal tower by controlling the operating environment conditions to influence the changing trends of the ionization equilibrium and the solubility equilibrium, and are not simultaneously enriched in the same area, thereby eliminating the formation of ammonium carbamate.

6. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 1, characterized in that: In step (ii), the top of the acid gas removal tower is operated at a pressure of 0.13 MPaG to 0.16 MPaG; the bottom of the tower is operated at a temperature of 110°C to 120°C, and the top of the tower is operated at a temperature of 40°C to 50°C.

7. The process for removing acid gas from amino acid-containing condensate and recovering ammonia according to claim 1, characterized in that: In step (iii), the acid gas containing a small amount of ammonia taken out from the top of the ammonia recovery tower is returned to the acid gas removal tower in step (ii), and the acid gas and ammonia are again stripped and separated to remove the acid gas, and the ammonia remains in the bottom of the tower; the ammonia condensate containing a small amount of acid gas in the bottom of the acid gas removal tower in step (ii) is sent to the ammonia recovery tower in step (iii), and ammonia is produced in the side line.

8. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 7, characterized in that: The acid gas taken out from the top of the acid gas removal tower has a low ammonia content, with a mass concentration of ≤100ppm, and the removed acid gas is sent to sulfur recovery; the steam ammonia taken out from the side line of the ammonia recovery tower contains acid gas hydrogen sulfide with a mass concentration of ≤300ppm and carbon dioxide with a mass concentration of ≤1000ppm, and is sent to step (IV) ammonia refining.

9. The process for removing acid gas from ammonia-containing condensate and recovering ammonia according to claim 1, characterized in that: In step (iii), the recovered liquid after the temperature is raised to 140°C to 150°C is fed from the upper part of the ammonia recovery tower; the operating pressure at the top of the ammonia recovery tower is 0.5 MPaG; the operating temperature of the tower bottom is 158°C to 165°C, and the operating temperature of the tower top is 55°C to 65°C; the temperature of the ammonia produced from the side line is 148°C to 152°C.

10. The process for removing acid gas and recovering ammonia from ammonia-containing condensate according to claim 1, characterized in that: In step (iv), the ammonia gas produced from the side line of the ammonia recovery tower in step (iii) is subjected to a first-stage cooling and pressure reduction, then a second-stage cooling and pressure reduction, and then a condensate circulation washing in a washing separator; then a third-stage cooling and pressure reduction, and then a bubbling washing in a washing separator; The acid gases carbon dioxide and hydrogen sulfide that escaped without being dissolved in the condensate are dissolved again in the separated condensate; After the circulating washing, the condensate is sent to the ammonia recovery tower in step (3) to remove the acid gas again and recover the ammonia. After the three-stage cooling and pressure reduction washing, the gaseous ammonia is cooled to room temperature and enters the pressure-reducing bubbling separator for bubbling separation to obtain high-purity ammonia separated by flash evaporation, which is sent to step (5) to prepare ammonia water.

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