Evaporation system for process stream

Abstract

To provide a safe, effective and cost-effective process and apparatus for eliminating or mitigating shortcomings of conventional processes.SOLUTION: A process and system for removing heavy organic impurities from a process stream includes providing a process stream having water and about 0.5 to about 1.5 mass% of heavy organic impurities. The process includes separating water from the heavy organic impurities in an evaporator system having one or more evaporation stages so as to provide an aqueous condensate and a liquid residue. The aqueous condensate has about 0.1 mass% or less of heavy organic impurities, and the liquid residue has about 3-10 mass% of heavy organic impurities.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] A method for removing heavy organic impurities from a process stream is provided. More specifically, the method includes providing a process stream and separating water from heavy organics from the process stream in an evaporator system, the evaporator system being effective to obtain an aqueous condensate and a liquid residue. [Background technology]

[0002] Various methods and systems for producing acrylonitrile and methacrylonitrile are known. See, for example, U.S. Patent No. 6,107,509. Typically, the recovery and purification of acrylonitrile / methacrylonitrile, which is produced by directly reacting a hydrocarbon selected from the group consisting of propane, propylene, or isobutylene, ammonia, and oxygen in the presence of a catalyst, includes the steps of transferring the reactor effluent containing acrylonitrile / methacrylonitrile to a first tower (quench) and cooling the reactor effluent with a first aqueous stream, transferring the cooled acrylonitrile / methacrylonitrile-containing effluent to a second tower (absorption tower) and contacting the cooled effluent with a second aqueous stream and absorbing the acrylonitrile / methacrylonitrile into the second aqueous stream. The purification process is accomplished by absorbing the triol from the second column, transferring a second aqueous stream containing acrylonitrile / methacrylonitrile from the second column to a first distillation column (recovery column) to separate the crude acrylonitrile / methacrylonitrile from the second aqueous stream, and transferring the separated crude acrylonitrile / methacrylonitrile to a second distillation column (first distillation column) to remove at least some of the impurities from the crude acrylonitrile / methacrylonitrile and transferring the partially purified acrylonitrile / methacrylonitrile to a third distillation column (product column) to obtain the acrylonitrile / methacrylonitrile product. U.S. Patents Nos. 4,234,510, 3,885,928, 3,352,764, 3,198,750 and 3,044,966 illustrate typical recovery and purification processes for acrylonitrile and methacrylonitrile.

[0003] A process for recovering olefinic nitriles is described in U.S. Pat. No. 4,334,965. As described in U.S. Pat. No. 4,334,965, a multi-stage evaporator is used to remove water from the extract distillate or stripper column bottoms which are recycled as a quench liquid to the quench tower of an acrylonitrile purification and recovery system. This process results in a significant reduction in the amount of quench tower waste bottoms produced by the system. The use of a multi-effect evaporator results in significant energy savings compared to other techniques for reducing the water content of the recycle stream. U.S. Pat. No. 4,334,965 discloses that, similar to U.S. Pat. No. 4,166,008, by using a multi-effect evaporator, more than 50% of the liquid in the recycle stream can be removed from the recycle stream, leaving a concentrated recycle stream that can be used as a quench liquid. However, U.S. Pat. No. 4,334,965 discloses that the overall energy costs of the technology are much lower compared to the technology described in U.S. Pat. No. 4,166,008, due to the very high energy efficiency of the multiple effect evaporators. Although acrylonitrile / methacrylonitrile production has been practiced commercially for many years, there remain areas where improvement would be substantially beneficial. One such area of ​​improvement would be more efficient evaporator operation on the recovery column bottoms. Summary of the Invention [Means for solving the problem]

[0004] Thus, one aspect of the present disclosure provides a safe, effective and cost-effective method and apparatus that overcomes or reduces the shortcomings of conventional methods. A method for removing heavy organic impurities from a process stream includes providing a process stream having water and about 0.5 to about 1.5 wt. % heavy organic impurities. The method includes separating the water from the heavy organic impurities in an evaporator system having one or more evaporation stages to obtain an aqueous condensate and a liquid residue. The aqueous condensate has less than about 0.1 wt. % heavy organic impurities and the liquid residue has about 3 to 10 wt. % heavy organic impurities.

[0005] The process for providing a liquid residue to an ammoxidation process stream includes the steps of providing a process stream comprising water and heavy organic impurities; separating the water from the heavy organic impurities in an evaporator system having one or more evaporation stages to obtain an aqueous condensate and a liquid residue; and contacting the liquid residue with a reactor effluent in a quench tower to obtain ammonium sulfate. In one embodiment, the amount of ammonium sulfate and the amount of polymer are defined by the formula y=-M1x+C1, where y is the weight percent of ammonium sulfate, x is the weight percent of polymer, M1 is 4.6 or less, and C1 is 45 or less. The evaporator system comprises one or more evaporation stages, where a first evaporation stage is configured to receive the process stream from the distillation column and the one or more evaporation stages are configured to obtain an aqueous condensate and a liquid residue; and the quench tower and / or the light organics stripper are configured to receive the aqueous condensate.

[0006] The evaporation process includes conveying the process stream from the distillation column to an evaporator system comprising one or more evaporation stages, a first evaporation stage configured to receive the process stream from the distillation column, obtaining an aqueous condensate and a liquid residue from the one or more evaporation stages, and conveying the aqueous condensate to a quench tower and / or a light organics stripper. The above and other aspects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. A more complete understanding of exemplary embodiments of the present disclosure and their advantages can be obtained by referring to the following description in conjunction with the accompanying drawings in which like reference numbers indicate like features, and in which: [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic flow diagram of a process for producing an acrylonitrile product. [Diagram 2] 1 is a schematic flow diagram of an alternative process for producing an acrylonitrile product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Ammoxidation Process In one embodiment, a process stream is provided from an ammoxidation reaction process, one example of which is described in U.S. Patent No. 4,334,965, incorporated herein in its entirety. A general schematic diagram of various embodiments is shown in Figure 1. Referring to Figure 1, reactor effluent gas in conduit 100, containing acrylonitrile, HCN, acetonitrile, water vapor and impurities, is first passed to a quench tower 102. The gas may be contacted with a quench liquid in the quench tower 102. A bottom stream containing water and impurities is removed via conduit 106 and may be sent to waste treatment. The cooled reactor effluent gas may exit the quench system via line 108 and be sent to quench aftercooler 107. Quench aftercooler 107 is effective to cool the quench effluent to less than about 50° C. The cooled quench effluent is provided to absorber tower 110 via line 109. Wash water may be charged to the top of absorber tower 110 via line 112. Noncondensable gases may be removed from absorber tower 110 via line 114. An aqueous solution containing water, acrylonitrile, acetonitrile and impurities may be removed as a bottoms stream via line 116 and passed to extractive distillation tower 182. To perform the extractive distillation, a water solvent may be introduced into the top of the extractive distillation column 182 via line 184. Acrylonitrile and HCN may be removed as overhead vapor via line 186 and sent for further purification (not shown). A stream containing acetonitrile and water may be removed via line 188 and passed to a stripper 190. Heat may be added to the stripper 190 and acetonitrile may be removed as overhead vapor via line 192. A bottoms stream containing water, heavy organics and other impurities may be removed from the extractive distillation column 182 via line 196. A liquid stream containing primarily water may be removed from the bottom half of the stripper 190 via line 194 and used as the water solvent for the extractive distillation column 182.

[0009] Evaporator System According to one embodiment, the stripper column bottoms in line 196, which may also be referred to as a process stream, may be subjected to evaporation in an evaporator system. In this embodiment, the extractive distillation column bottoms in line 196, which may enter heat exchanger 136, includes water, polymers, ammonia, and acrylonitrile. As used herein, "heavy organic impurities" refers to polymers. As used herein, polymers refers to a mixture of heavy organics and trace amounts of light organics. Heavy organics may include a mixture of various high boiling organic compounds that have a high degree of nitrile substitution and also contain some oxygenated hydrocarbon groups. In this embodiment, the process stream includes from about 0.5 to about 1.5 wt. % heavy organic impurities, and in another embodiment, from about 0.75 to about 1.25 wt. % heavy organic impurities.

[0010] In this embodiment, the evaporator system may include one or more evaporation stages effective to obtain an aqueous condensate and a liquid residue. For example, the evaporator system may include 1 to about 6 evaporation stages, in another embodiment, 2 to about 6 evaporation stages, in another embodiment, 2 to about 5 evaporation stages, in another embodiment, 2 to about 4 evaporation stages, and in another embodiment, 2 to about 3 evaporation stages. In the embodiment shown in FIG. 1, the evaporator system comprises shell and tube heat exchangers 136, 138 and 142 in series. As used herein, "evaporation stage" refers to a single heat exchanger. In each heat exchanger, liquid on the tube side of the exchanger is partially evaporated to produce a vaporous effluent and a liquid effluent. The liquid effluent is fed to the tube side of the next heat exchanger in the series, while the vaporous effluent is fed to the shell side of the same heat exchanger to cause additional partial evaporation of the liquid. This technique is continued for as many stages as necessary to remove the desired amount of water from the stripper bottoms. In each stage, the heat supply steam is condensed via heat exchange to produce a condensate that is recovered and recycled for reuse or for chemical or biological purification.

[0011] A bottoms stream containing water, heavy organics and other impurities may be removed from extractive distillation column 182 via line 196 and sent to the tube side of first heat exchanger 136 while the low pressure vapor stream passes through the shell side of this heat exchanger. In one embodiment, the flow through the tube side of the heat exchanger is from about 1 to about 3 m / sec, and in another embodiment, from about 1.5 to about 2.5 m / sec. The heat exchange therein causes the low pressure vapor to condense and the extractive distillation column bottoms to partially vaporize. The condensate may be removed from first heat exchanger 136 for recycle via line 146.

[0012] Heating the extractive distillation column bottoms in the first heat exchanger 136 causes the extractive distillation column bottoms to be partially separated into a gas phase and a liquid phase. In an embodiment in which more than one heat exchanger is used, the liquid phase is withdrawn via line 148 and transferred to the tube side of the second heat exchanger 138, and a portion of the withdrawn liquid is recycled via line 150 to the bottom tube side of the first heat exchanger 136. The vapor generated in the first heat exchanger 136 is withdrawn via line 152 and transferred to the shell side of the second heat exchanger 138. The heat exchange in the heat exchanger 138 causes condensation of the vapor in the shell side and partial evaporation of the liquid in the tube side, thereby producing liquid in the gas phase in the second heat exchanger 138. The condensate generated in the shell side of the second heat exchanger 138 is discharged via line 154. This condensate has a relatively low concentration of heavy organics such as polymers. In embodiments where more than two heat exchangers are used, the liquid phase remaining on the tube side of the second heat exchanger 138 is transferred to the tube side of the third heat exchanger 142 via line 156, and a portion of the liquid is recirculated to the tube side of the second heat exchanger 138 via line 158. The vapor generated on the tube side of the second heat exchanger 138 is transferred to the shell side of the third heat exchanger 142 via line 160. Again, the heat exchange in the third heat exchanger 142 causes condensation of the vapor on the shell side to form a condensate which, like the condensate from the second heat exchanger 138, is withdrawn and transported via line 176.

[0013] Vapor generated on the tube side of the third heat exchanger 142 is withdrawn via line 170, condensed in condenser 172, collected in a water reservoir, and / or mixed with condensate from lines 146, 154, 162, and / or 176. Condensate from the shell side of heat exchanger 142 may be transferred via line 176 to a water reservoir for mixing and providing, for example, at 135. Liquid recovered from the tube side of the third heat exchanger 142 may be withdrawn via line 178 and recycled to the tube side of the third heat exchanger via line 180. The aqueous condensate may be of such high purity that it may be used as return water to a quench tower (e.g., the first stage of the quench tower) and / or a light organics stripper, for example, as conventional clean water for cleaning various process equipment. In this embodiment, the aqueous condensate has no more than about 0.1% by weight heavy organic impurities, in another embodiment about 0.075% by weight heavy organic impurities, in another embodiment about 0.05% by weight heavy organic impurities, and in another embodiment about 0.025% by weight heavy organic impurities.

[0014] In this embodiment, the liquid residue has about 3 to about 10% by mass of heavy organic impurities, in another embodiment about 4 to about 8% by mass of heavy organic impurities, and in another embodiment about 5 to about 7% by mass of heavy organic impurities. As shown in Figure 1, the liquid residue may be sent to a wastewater incinerator (WWI). Alternatively, as shown in Figure 2, the liquid residue may be sent to the lower part of the quench tower 102 via line 179. In one embodiment, the aqueous condensates generated in the second and third heat exchangers contain trace amounts of heavy organic matter. Therefore, they can be directly treated by conventional biological or chemical treatment to produce environmentally compatible water. Furthermore, the condensate generated in the fourth heat exchanger, like the condensate generated by the condenser, has a purity sufficient to be used for various process purposes such as wash water without further treatment. The condensate generated by the first heat exchanger has a high purity because it does not come into contact with other process streams.

[0015] Evaporation Percentage In one embodiment, higher evaporation rates may be beneficial since the evaporator condensate may be recycled or discarded, although the liquid residue from the last stage of a multi-stage evaporator may be incinerated and / or alternatively discarded. In one embodiment, the evaporation percentage of the extractive distillation column bottoms may be greater than about 55% and less than or equal to about 85%. In one embodiment, the evaporation percentage of the extractive distillation column bottoms may be greater than about 60%. In one embodiment, the evaporation percentage of the extractive distillation column bottoms may be greater than about 60% and less than or equal to about 85%. In one embodiment, the evaporation percentage of the extractive distillation column bottoms may be in the range of about 73 to about 75%.

[0016] By performing a four-stage evaporation process with a vaporization percentage of about 55 to about 60%, and in one embodiment about 57%, the percentage of liquid polymer in the evaporator bottoms exiting the fourth and final heat exchanger 142 can be about 2.2% by weight. By performing a four-stage evaporation process with a vaporization percentage of about 60-65%, and in one embodiment about 63%, the percentage of liquid polymer in the evaporator bottoms exiting the fourth and final heat exchanger 142 can be about 3% by weight. By performing a four-stage evaporation process with a vaporization percentage of about 80-85%, and in one embodiment about 83%, the percentage of liquid polymer in the evaporator bottoms exiting the fourth and final heat exchanger 142 can be about 6% by weight.

[0017] By performing a four-stage evaporation process with a vaporization percentage of about 73-75%, and in one embodiment about 74%, the percentage of liquid polymer in the evaporator bottoms exiting the fourth and final heat exchanger 142 can be about 5.5% by weight. In one embodiment, each evaporation stage provides an evaporation rate of about 15 to about 25%. In one embodiment, the percentage of evaporator condensate divided by the feed percentage can be the evaporation percentage of the bottoms of extractive distillation column 182. In one embodiment, the evaporation percentage is about 55 to about 60%, and in another embodiment, about 57%. The amount of polymer in the liquid residue is about 2.2% by weight. In one embodiment, the ratio of the evaporation percentage value to the weight percent of the polymer is about 55-60:2.2.

[0018] In another embodiment, the amount of polymer in the liquid residue is about 3% by weight. In one embodiment, the ratio of the evaporation percentage value to the polymer weight percentage is about 60-65:3. In one embodiment, the evaporation percentage is about 82-83% and the amount of polymer in the liquid residue is about 6.0 wt.%. The condensate may be provided as feed to a light organics stripper (LOS) (not shown) via line 135 for further processing or sent to quench tower 102 as a quench liquid. In one embodiment, the ratio of the evaporation percentage value to the wt.% of polymer is about 82-83:6. In one embodiment, the evaporation percentage is about 73-75% and the polymer in the liquid residue is about 5.5 wt. %. The condensate may be provided as feed to a light organics stripper (LOS) (not shown) via line 135 for further processing or sent to quench tower 102 as a quench liquid. In one embodiment, the ratio of the evaporation percentage value to the polymer wt. % is about 73-75:5.5.

[0019] In one embodiment, it has been found that an evaporation percentage of about 74% results in substantially less fouling compared to an evaporation percentage of about 83%, while at the same time resulting in a relatively high mass of polymer in the liquid residue, i.e., 5.5 mass %, compared to 6.0 mass % at an evaporation percentage of about 83%. This is a surprising result, since one would expect the amount of fouling to be proportional to the mass % of polymer in the liquid stream. It has been found that evaporation percentages greater than about 83% can result in significant fouling (often on the tube side) in the fourth stage evaporator or heat exchanger 142. It has been found that evaporation percentages of about 73-75% significantly reduce the amount of fouling, but at the same time result in a relatively high mass of polymer in the liquid residue.

[0020] Those skilled in the art will appreciate that many modifications may be made in accordance with the present disclosure without departing from the spirit and scope of the present disclosure. For example, any number of stages may be used in the evaporator system. Additionally, while low pressure steam is shown in the above description to provide the heat required for all the evaporation, any heat source may be used. However, in a typical acrylonitrile purification and recovery plant, low pressure steam, i.e., saturated steam having a pressure of up to 100 psig, typically about 20-60 psig, is readily available and is preferably used. Similarly, the amount of water in the stripper column that is removed by the multiple effect evaporator may vary, primarily depending on economics. Finally, it should also be appreciated that the multiple effect evaporator of the present disclosure need not be limited to use with the stripper column bottoms shown in the above description, but may be used to condense any other process stream that is recycled for use as a quench liquid. For example, the multiple effect evaporator may be used to treat the extractive distillation column bottoms recycled in line 156 of FIG. 2 of U.S. Pat. No. 4,166,008. All such modifications are intended to be included within the scope of this disclosure, which is limited only by the following claims.

[0021] Quenching tower operation In one embodiment, a method of operating a quench tower includes conveying a reactor effluent to the quench tower and contacting the reactor effluent with water containing polymer in an effluent extraction section to obtain an extracted effluent stream. The method further includes contacting the extracted effluent stream with sulfuric acid in an acid contacting section and removing a first stream to provide a first quench tower stream having about 10 wt.% or less of polymer. In one embodiment, the method includes providing at least a portion of the water from an evaporator system. As described herein, the water can be an aqueous condensate and / or a liquid residue.

[0022] In one embodiment, the equation y=-M1x+C1, where y is the weight percent ammonium sulfate, x is the weight percent polymer, M1 is 4.6 or less, and C1 is 45 or less, defines the amount of ammonium sulfate and the amount of polymer in the quench tower bottoms stream. In a related embodiment, M1 is 1.5 or less and C1 is 30 or less. In one embodiment, the process provides a quench tower bottoms stream having about 10 to about 25 weight percent ammonium sulfate and less than about 5% polymer, and in another embodiment, about 15 to about 21 weight percent ammonium sulfate and less than about 5% polymer. The quench tower bottoms stream has a pH of about 4.5 to about 6.0. In another embodiment, the method includes removing a second stream to obtain a second quench tower stream having greater than about 10% by weight polymer and less than about 5% by weight ammonium sulfate. In another embodiment, at least a portion of the second quench tower stream is recycled to the effluent extraction section. The extraction effluent stream flows countercurrently to the sulfuric acid. In one embodiment, the first quench tower stream is removed upstream of the effluent extraction section. Adiabatic cooling may be performed in the effluent extraction section.

[0023] In one embodiment, the method may include controlling the amount of make-up water delivered to the quench tower and / or controlling the amount of sulfuric acid delivered to the quench tower to obtain a particular concentration of ammonium sulfate in the quench tower bottoms stream of about 10 to about 25% by weight. In one embodiment, the method may include detecting a pH of the quench tower bottoms and controlling a flow of sulfuric acid to the quench tower based on the detected pH of the bottoms to obtain a quench tower bottoms stream having a pH of about 4.5 to 6.0. In one embodiment, the method may include quantifying a concentration of ammonium sulfate in the quench tower bottoms stream based on the flow rate of sulfuric acid to the quench tower and the flow rate of the quench tower bottoms stream into and out of the quench tower. In one embodiment, the method may include adjusting the flow rate of sulfuric acid and / or make-up water delivered to the quench tower based on the concentration of ammonium sulfate determined in the determining step to maintain the concentration of ammonium sulfate in the range of about 10 to about 25% by weight. By increasing the concentration of ammonium sulfate in the quench tower bottoms stream from about 5 to about 10 weight percent, as obtained in conventional processes, to about 10 to about 25 weight percent, less water needs to be removed from the quench tower bottoms stream to obtain a higher concentration of ammonium sulfate. It has been found that by increasing the concentration of ammonium sulfate in the quench tower bottoms stream to about 10 to about 25 weight percent, the quench tower bottoms stream can be efficiently condensed to about 35 to 40 weight percent using a sulfate condenser.

[0024] In the foregoing specification, the disclosure has been described in relation to certain preferred embodiments thereof, and many details have been set forth for illustrative purposes, but it will be apparent to those skilled in the art that further embodiments are possible in the present disclosure, and that some of the details described herein may be significantly modified without departing from the basic principles of the present disclosure. It should be understood that features of the present disclosure may be modified, altered, changed, or substituted without departing from the spirit and scope of the present disclosure or the scope of the claims. For example, the dimensions, number, size, and shape of the various components may be modified to suit a particular application. Thus, the specific embodiments shown and described herein are for illustrative purposes only.

Claims

1. 1. A method for subjecting a liquid residue to an ammoxidation process stream, comprising the steps of: providing a process stream comprising water and heavy organic impurities; separating water from the heavy organic impurities in an evaporator system having one or more evaporation stages to obtain an aqueous condensate and a liquid residue; contacting the liquid residue with the reactor effluent in a quench tower to obtain ammonium sulfate. wherein the amount of ammonium sulfate and the amount of polymer are defined by the equation y=-M1x+C1, where y is the weight percent of ammonium sulfate, x is the weight percent of polymer, M1 is 4.6 or less, and C1 is 45 or less.

2. 2. The method of claim 1, wherein the aqueous condensate has about 0.1% by weight or less of heavy organic impurities and the liquid residue has about 3 to about 10% by weight of heavy organic impurities.

3. 10. The method of claim 1, wherein the process stream comprises from about 0.5 to about 1.5 wt. % heavy organic impurities.

4. 10. The method of claim 1, wherein the heavy organic impurities comprise polymeric materials produced in an ammoxidation reaction process.

5. The method of claim 1 , wherein the evaporator system comprises from 1 to about 6 evaporation stages.

6. The method of claim 1 , wherein the evaporator system comprises from 2 to about 6 evaporation stages.

7. The method of claim 1 , wherein the evaporator system comprises from 2 to about 5 evaporation stages.

8. The method of claim 1 , wherein the evaporator system comprises from 2 to about 4 evaporation stages.

9. The method of claim 1 , wherein the evaporator system comprises from 2 to about 3 evaporation stages.

10. 10. The method of claim 1, wherein the process stream comprises from about 0.75 to about 1.25 wt. % heavy organic impurities.

11. 5. The method of claim 4, wherein the ammoxidation process is an acrylonitrile process.

12. 12. The method of claim 11, wherein the process stream is a bottoms stream from an extractive distillation column of an acrylonitrile process.

13. 10. The method of claim 1 , wherein the aqueous condensate has about 0.075 wt.% or less of heavy organic impurities.

14. 10. The method of claim 1 , wherein the aqueous condensate has about 0.05 wt.% or less of heavy organic impurities.

15. 10. The method of claim 1 , wherein the aqueous condensate has about 0.025% by weight or less of heavy organic impurities.

16. The method of claim 1 , wherein at least a portion of the aqueous condensate is conveyed to a quench tower and / or a light organics stripper.

17. 17. The method of claim 16, wherein at least a portion of the aqueous condensate is conveyed to a first stage of a quench tower.

18. The method of claim 1 , wherein the evaporator system is effective to achieve a total evaporation percentage of greater than about 55% and up to about 85%.

19. The method of claim 1 , wherein the evaporator system is effective to achieve a total evaporation percentage of greater than about 60% to about 85%.

20. 10. The method of claim 1, wherein the evaporator system is effective to achieve a total evaporation percentage of greater than about 73% and up to about 75%.

21. 10. The method of claim 1, wherein the liquid residue has about 4 to about 8 weight percent heavy organic impurities.

22. 10. The method of claim 1, wherein the liquid residue has about 5 to about 7 weight percent heavy organic impurities.

23. The method of claim 1 , wherein the evaporator system comprises at least one shell-and-tube heat exchanger.

24. 24. The method of claim 23, wherein the flow through the tube side of the heat exchanger is from about 1 to about 3 m / sec.

25. The method of claim 1 , wherein each evaporation stage achieves an evaporation rate of about 15 to about 25%.

26. 2. The method of claim 1, wherein M1 is 1.5 or less and C1 is 30 or less.

27. 10. The process of claim 1, wherein sulfuric acid is conveyed to the quench tower to obtain a quench tower bottoms stream having from about 10 to about 25 weight percent ammonium sulfate and less than about 5% polymer.

28. 10. The process of claim 1, wherein sulfuric acid is conveyed to the quench tower to obtain a quench tower bottoms stream having from about 15 to about 21 weight percent ammonium sulfate and less than about 5% polymer.

29. 10. The process of claim 1, wherein the quench tower bottoms stream has a pH of from about 4.5 to about 6.

0.

30. 30. The method of claim 29, wherein the pH is controlled by the addition of acid.

31. one or more evaporation stages, a first evaporation stage configured to receive the process stream from the distillation column, the one or more evaporation stages configured to provide an aqueous condensate and a liquid residue; and a quench tower and / or a light organics stripper configured to receive the aqueous condensate; 1. An evaporator system comprising:

32. 32. The system of claim 31, wherein the liquid residue is conveyed to a wastewater incinerator.

33. 32. The system of claim 31 , wherein a lower portion of the quench tower is configured to receive the liquid residue.

34. The system of claim 31 , wherein the evaporator system comprises from 1 to about 6 evaporation stages.

35. The system of claim 31 , wherein the evaporator system comprises from 2 to about 6 evaporation stages.

36. The system of claim 31 , wherein the evaporator system comprises from 2 to about 5 evaporation stages.

37. The system of claim 31 , wherein the evaporator system comprises from 2 to about 4 evaporation stages.

38. The system of claim 31 , wherein the evaporator system comprises from 2 to about 3 evaporation stages.

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