阅读说明：本技术 用于工艺流的蒸发系统 (Vaporization system for process streams ) 是由 T·R·麦克唐奈 J·R·库奇 D·R·瓦纳 P·T·瓦赫滕多夫 于 2014-09-29 设计创作，主要内容包括：本发明涉及一种用于工艺流的蒸发系统。用于从工艺流移除重有机杂质的工艺和系统包括提供具有水和大约0.5至大约1.5重量百分数的重有机杂质的工艺流。该工艺包括在具有一个或更多个蒸发级的蒸发器系统中将水与重有机杂质分离以提供含水冷凝物和液体残余物。含水冷凝物具有大约0.1重量百分数或更少的重有机杂质而液体残余物具有大约3至大约10重量百分数的重有机杂质。(The present invention relates to an evaporation system for a process stream. A process and system for removing heavy organic impurities from a process stream includes providing a process stream having water and from about 0.5 to about 1.5 weight percent of heavy organic impurities. The process includes separating water from heavy organic impurities in an evaporator system having one or more evaporation stages to provide an aqueous condensate and a liquid residue. The aqueous condensate has about 0.1 weight percent or less of the heavy organic impurities and the liquid residue has about 3 to about 10 weight percent of the heavy organic impurities.)

1. A process for removing heavy organic impurities from a process stream, the process comprising:

providing a process stream comprising water and heavy organic impurities; and

separating water from the heavy organic impurities in an evaporator system having two or more evaporation stages to provide an aqueous condensate and a liquid residue;

the method is characterized in that:

the two or more evaporation stages comprise two or more heat exchangers arranged in series;

each heat exchanger is a shell and tube heat exchanger and in each heat exchanger, the liquid in the tube side of the heat exchanger is partially evaporated to produce a vapor-like effluent and a liquid effluent;

the liquid effluent produced in a heat exchanger is sent to the tube side of the next heat exchanger in the series, and the vaporous effluent produced in a heat exchanger is sent to the shell side of the next heat exchanger in the series, causing additional partial evaporation of the liquid, which is continuous for as many stages as necessary to remove the desired amount of water from the process stream;

wherein in each stage steam supplied with heat is condensed by the heat exchanger to produce an aqueous condensate which is recovered and recycled for reuse or subjected to chemical or biological purification;

wherein the evaporator system provides a total evaporation percentage of greater than 55% to 85%;

wherein the aqueous condensate has 0.1 weight percent or less of heavy organic impurities and the liquid residue has 3 to 10 weight percent of heavy organic impurities; and

wherein at least a portion of the aqueous condensate is passed to a quench tower and/or a light organics stripper.

2. The process of claim 1, wherein the process stream comprises 0.5 to 1.5 weight percent of heavy organic impurities.

3. The process of claim 1, wherein the heavy organic impurities comprise polymeric materials produced during an ammoxidation reaction.

4. The process of claim 1, wherein the evaporator system comprises 2 to 6 evaporation stages.

5. The process of claim 1, wherein the evaporator system comprises 2 to 5 evaporation stages.

6. The process of claim 1, wherein the evaporator system comprises 2 to 4 evaporation stages.

7. The process of claim 1, wherein the evaporator system comprises 2 to 3 evaporation stages.

8. The process of claim 1, wherein the process stream comprises 0.75 to 1.25 weight percent of heavy organic impurities.

9. The process of claim 3 wherein the ammoxidation process is an acrylonitrile process.

10. The process of claim 9, wherein the process stream is a residue stream from an extractive distillation column of an acrylonitrile process.

11. The process of claim 1, wherein the aqueous condensate has 0.075 weight percent or less of heavy organic impurities.

12. The process of claim 1, wherein the aqueous condensate has 0.05 weight percent or less of heavy organic impurities.

13. The process of claim 1, wherein the aqueous condensate has 0.025 weight percent or less of heavy organic impurities.

14. The process of claim 1, wherein at least a portion of the aqueous condensate is passed to a first stage of a quench tower.

15. The process of claim 1, wherein the evaporator system provides a total evaporation percentage of greater than 60% to 85%.

16. The process of claim 1, wherein the evaporator system provides a total evaporation percentage of greater than 73% to 75%.

17. The process of claim 1, wherein the liquid residue has 4 to 8 weight percent of heavy organic impurities.

18. The process of claim 1, wherein the liquid residue has 5 to 7 weight percent of heavy organic impurities.

19. The process of claim 1, wherein the flow through the tube side of the heat exchanger is 1 to 3 meters per second.

20. The process of claim 1, wherein each evaporation stage provides an evaporation rate of 15 to 25%.

21. The process of claim 1, wherein the liquid residue is sent to a waste water incinerator.

Technical Field

A process for removing heavy organic impurities from a process stream is provided. More specifically, the process includes providing a process stream and separating water from heavy organics from the process stream in an evaporation system. The evaporation system is effective for providing an aqueous condensate and a liquid residue.

Background

Various processes and systems are known for the manufacture of acrylonitrile and methacrylonitrile; see, for example, U.S. patent No. 6,107,509. Typically, the recovery and purification of acrylonitrile/methacrylonitrile produced by the direct reaction of a hydrocarbon selected from propane, propylene or isobutylene, ammonia and oxygen in the presence of a catalyst is carried out by transporting the reactor effluent comprising acrylonitrile/methacrylonitrile to a first column (quench) where the reactor effluent is cooled with a first aqueous stream, transporting the cooled effluent comprising acrylonitrile/methacrylonitrile to a second column (absorber) where the cooled effluent is contacted with a second aqueous stream to absorb acrylonitrile/methacrylonitrile into a second aqueous stream, transporting the second aqueous stream comprising acrylonitrile/methacrylonitrile from the second column to a first distillation column (recovery column) for separating the original acrylonitrile/methacrylonitrile from the second aqueous stream and separating the separated original acrylonitrile/methacrylonitrile The olefinic nitrile is transported to a second distillation column (heads column) to remove at least some impurities from the original acrylonitrile/methacrylonitrile and the partially purified acrylonitrile/methacrylonitrile is transported to a third distillation column (product column) to obtain the finished acrylonitrile/methacrylonitrile U.S. patent 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.

A process for recovering an olefinic nitrile is described in U.S. Pat. No. 4,334,965. As described in U.S. patent No. 4,334,965, a multi-stage evaporator is used to remove water from extractive distillation or stripper bottoms (stripper tower bottoms) that is recycled as a coolant 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 residue produced by the system. The use of multiple effect evaporators represents a significant energy savings over other techniques for reducing the water content of the recycle stream. U.S. patent No. 4,334,965 discloses that by means of a multiple effect evaporator, 50% or more of the liquid in the recycle stream can be removed therefrom in the same manner as shown in U.S. patent No. 4,166,008, leaving a concentrated recycle stream to be used as a cooling liquid. U.S. patent No. 4,334,965 discloses that however because the multiple effect evaporator is so energy efficient, the overall energy cost of the technique is much lower than the technique described in U.S. patent No. 4,166,008.

Although the manufacture of acrylonitrile/methacrylonitrile has been commercially practiced for many years, there are areas in which improvements would be of substantial benefit. One of these areas of improvement would be more efficient evaporator operation for recovery column residue.

Disclosure of Invention

Accordingly, it is an aspect of the present invention to provide a safe, efficient and cost effective process and apparatus that overcomes or reduces the disadvantages of conventional processes.

A process for removing heavy organic impurities from a process stream includes providing a process stream having water and about 0.5 to about 1.5 weight percent of heavy organic impurities. The process includes separating water from heavy organic impurities in an evaporator system having one or more evaporation stages to provide an aqueous condensate and a liquid residue. The aqueous condensate has about 0.1 weight percent or less of the heavy organic impurities and the liquid residue has about 3 to about 10 weight percent of the heavy organic impurities.

A process for providing a liquid residue to an ammonia oxidation process stream comprising: providing a process stream comprising water and heavy organic impurities; separating water from heavy organic impurities in an evaporator system having one or more evaporation stages to provide an aqueous condensate and a liquid residue; and contacting the liquid residue with the reactor effluent in a quench tower to provide ammonium sulfate. In one aspect, the amount of ammonium sulfate and the amount of polymer is 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.

An evaporator system includes one or more evaporation stages, wherein a first evaporation stage is configured to receive a process stream from a 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 organic stripper (light organic stripper) configured to receive the aqueous condensate.

An evaporation process includes conveying a process stream from a distillation column to an evaporator system, the evaporator system including one or more evaporation stages, wherein a first evaporation stage is configured to receive the process stream from the distillation column, provide an aqueous condensate and a liquid residue from the one or more evaporation stages; and passing the aqueous condensate to a quench tower and/or a light organics stripper.

The above and other aspects, features and advantages of the present invention will become apparent from the following detailed description of the illustrated embodiments thereof, which is to be read in connection with the accompanying drawings.

Drawings

A more complete understanding of the exemplary embodiments of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein:

figure 1 shows a schematic flow diagram of a process for making an acrylonitrile product,

fig. 2 shows a schematic flow diagram of an alternative process for manufacturing acrylonitrile products.

Detailed Description

Ammonia oxidation process

In one aspect, the process stream is provided from an ammoxidation reaction process. An example of one such process is illustrated in U.S. patent No. 4,334,965, which is incorporated herein in its entirety.

FIG. 1 is a global schematic representation of various aspects. Referring to fig. 1, the reactor effluent gas in line (conduit)100, which includes acrylonitrile, HCN, acetonitrile, water vapor and impurities, may first be passed to quench column 102. The gas may be contacted with a cooling liquid in the quench tower 102. A bottoms stream comprising water and impurities can be removed via line 106 and sent to waste disposal.

The cooled reactor effluent gas may exit the quench system via line 108 and be passed to a post quench cooler 107. The post-quench cooler 107 is effective for cooling the quench effluent to below about 50 ℃. The cooled quench effluent is sent to absorber 110 via line 109. Rinse water may enter the absorber 110 at the top through line 112. Non-condensable gases may be removed from the absorber via line 114. An aqueous solution (which comprises water, acrylonitrile, acetonitrile, and impurities) can be removed as a residue stream through line 116 and sent to extractive distillation column 182.

Solvent moisture may be introduced to the top of extractive distillation column 182 via line 184 to perform extractive distillation. Acrylonitrile and HCN may be removed as overhead vapor (overhead vapor) via line 186 and sent to further purification (not shown). A stream comprising acetonitrile and water may be removed via line 188 and sent to stripper 190. Heat may be added to stripper 190 to remove acetonitrile as overhead vapor via line 192. A residue stream comprising water, heavy organics, and other impurities can be removed from the extractive distillation column 182 via line 196. A liquid stream comprising primarily water may be removed from the lower half of stripper 190 through line 194 and used as solvent moisture to extractive distillation column 182.

Evaporator system

According to an aspect, stripper residue (which may also be referred to as a process stream) in line 196 can be subject to vaporization in the vaporizer system. In this regard, the extractive distillation column residue in line 196, which may enter heat exchanger 136, includes water, polymer, ammonia and acrylonitrile. As used herein, "heavy organic impurities" refers to polymers. As used herein, polymer refers to a mixture of heavy organic material and a small amount of light organic. Heavy organic materials may include mixtures of different high boiling point organic compounds (which have a high degree of nitrile substitution and also contain some oxygenated hydrocarbon groups). In this aspect, the process stream includes about 0.5 to about 1.5 weight percent of the heavy organic impurities, and in another aspect about 0.75 to about 1.25 weight percent.

In this regard, the evaporator system can include one or more evaporation stages effective to provide an aqueous condensate and a liquid residue. For example, the evaporator system can include from 1 to about 6 evaporation stages, from 2 to about 6 evaporation stages in another aspect, from 2 to about 5 evaporation stages in another aspect, from 2 to about 4 evaporation stages in another aspect, and from 2 to about 3 evaporation stages in another aspect.

In one aspect shown in fig. 1, the evaporator system includes shell and tube heat exchangers 136, 138 and 142 arranged in series. As used herein, "evaporation stage" refers to a single heat exchanger. In each heat exchanger, the liquid in the tube side of the heat exchanger is partially evaporated, producing a vaporous effluent and a liquid effluent. The liquid effluent is sent to the tube side of the next heat exchanger in series, while the vapor-like effluent is sent to the shell side of the same heat exchanger, causing additional partial vaporization of the liquid. This technique is continuous for as many stages as necessary to remove the desired amount of water from the stripper residue. In each stage, the condensate produced when the steam supplying the heat is condensed by heat exchange is recovered and recycled for reuse or subjected to chemical or biological purification.

A residue stream comprising water, heavy organics, and other impurities can be removed from the extractive distillation column 182 via line 196 and passed into the tube side of the first heat exchanger 136, while a lower pressure stream is passed through the shell side of the heat exchanger. The flow through the tube side of the heat exchanger is about 1 to about 3 meters/second on the one hand, and about 1.5 to about 2.5 meters/second on the other hand. The heat exchange therein causes the low pressure stream to condense and partially vaporize the extractive distillation column residue. Condensate may be removed from the first heat exchanger 136 via line 146 for reuse.

The heating of the extractive distillation column residue in the first heat exchanger 136 causes a partial separation thereof into vapor and liquid phases. In aspects where more than one heat exchanger is used, the liquid phase is withdrawn via line 148 and sent to the tube side of the second heat exchanger 138, and a portion of the withdrawn liquid is recycled to the bottom of the tube side of the first heat exchanger 136 via line 150. Steam produced in the first heat exchanger 136 is withdrawn and sent to the shell side of the second heat exchanger 138 via line 152. The heat exchange in the heat exchanger 138 causes condensation of the vapor on the shell side and partial evaporation of the liquid in the tube side, thereby producing liquid in the vapor phase in the second heat exchanger 138. Condensate produced on the shell side of the second heat exchanger 138 is discharged via line 154. The condensate has a relatively low concentration of heavy organics such as polymers and the like.

In aspects where more than two heat exchangers are used, the liquid phase remaining in the tube side of the second heat exchanger 138 is routed to the tube side of the third heat exchanger 142 via line 156, and a portion of the liquid is recycled to the tube side of the second heat exchanger 138 via line 158. Steam produced in the tube side of the second heat exchanger 138 is delivered to the shell side of the third heat exchanger 142 via line 160. The heat exchange in the third heat exchanger 142 in turn causes the steam to condense on the shell side to form condensate (which is withdrawn via line 176 and delivered in the same manner as the condensate from the second heat exchanger 138).

Steam generated in the tube side of the third heat exchanger 142 is withdrawn via line 170, condensed in condenser 172 and recovered in a utility water vessel and/or combined with condensate from lines 146, 154, 162, and/or 176. Condensate from the tube side of the heat exchanger 142 may also be delivered to the utility water vessel via line 176, for example as combined and provided at 135. Liquid recovered from the tube side of the third heat exchanger 142 can 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, for example, as conventional clear water, for example, in a rinse of various process equipment, as reflux to a quench tower (e.g., the first stage of a quench tower) and/or to a light organics stripper. In this regard, the aqueous condensate has about 0.1 weight percent or less of heavy organic impurities, in another aspect about 0.075 weight organic impurities, in another aspect about 0.05 weight organic impurities, and in another aspect about 0.025 weight organic impurities.

In another aspect, the liquid residue has from about 3 to about 10 weight percent heavy organic impurities, in another aspect from about 4 to about 8 weight percent heavy organic impurities, and in another aspect from about 5 to about 7 weight percent heavy organic impurities. As shown in fig. 1, the liquid residue may be sent to a Waste Water Incinerator (WWI). Alternatively, as shown in FIG. 2, the liquid residue may be sent to a lower portion of the quench tower 102 via line 179.

In one aspect, the aqueous condensate produced in the second and third heat exchangers contains extremely small amounts of heavy organics. Thus, it can be treated directly by conventional biological or chemical treatment means to produce environmentally acceptable water. Furthermore, the condensate produced in the fourth heat exchanger and the condensate produced by the condenser are pure enough to be used for various process purposes, such as rinse water without further treatment. The condensate produced by the first heat exchanger is highly pure because it does not contact any other process streams.

Percentage of evaporation

In one aspect, higher evaporation may be beneficial because evaporator condensate may be reused or disposed of, while liquid residue from the final stage of a multi-stage evaporator may be incinerated and/or otherwise disposed of.

In one aspect, the percent vaporization of the residue of the extractive distillation column can be greater than about 55% to about 85%. In one aspect, the percent evaporation of the residue of the extractive distillation column can be greater than about 60%. In one aspect, the percent vaporization of the residue of the extractive distillation column can be greater than about 60% to about 85%. In one aspect, the percent vaporization of the residue of the extractive distillation column can be in the range of about 73% to about 75%.

By operating the four (4) stage vaporization process with a vaporization percentage of about 55 to about 60%, and in one aspect about 57%, the percentage of liquid polymer in the evaporator residue exiting the fourth and final heat exchanger 142 can be about 2.2% by weight.

By operating the four (4) stage evaporation process with about 60-65%, and in one aspect about 63%, percent evaporation, the percentage of liquid polymer in the evaporator residue exiting the fourth and final heat exchanger 142 can be about 3% by weight.

By operating the four (4) stage evaporation process with an evaporation percentage of about 80-85%, and in one aspect about 83%, the percentage of liquid polymer in the evaporator residue exiting the fourth and final heat exchanger 142 can be about 6% by weight.

By operating the four (4) stage evaporation process with an evaporation percentage of about 73-75%, and in one aspect about 74%, the percentage of liquid polymer in the evaporator residue exiting the fourth and final heat exchanger 142 can be about 5.5% by weight.

In one aspect, each evaporation stage provides an evaporation rate of about 15 to about 25%.

In one aspect, the percentage of evaporator condensate divided by the percent feed can be the percentage of evaporation of the residue of the extractive distillation column 182. In one aspect, the percent evaporation is from about 55 to about 60%, and in another aspect about 57%. The amount of polymer in the liquid residue was about 2.2 weight percent. In one aspect, the ratio of the percent evaporation to the weight percent of the polymer is about 55-60: 2.2.

In another aspect, the amount of polymer in the liquid residue is about 3 weight percent. In one aspect, the ratio of the percent evaporation to the weight percent of the polymer is about 60-65: 3.

In one aspect, the percent evaporation is about 82 to about 83%, and the amount of polymer in the liquid residue is about 6.0 weight percent. The condensate may be fed as a feed via line 135 to a light organics stripper LOS (not shown) for further processing or sent as a cooling liquid to the quench tower 102. In one aspect, the ratio of the percent evaporation to the weight percent of the polymer is about 82-83: 6.

In one aspect, the percent evaporation is about 73 to about 75 percent, and the polymer in the liquid residue is about 5.5 weight percent. The condensate may be fed as a feed via line 135 to a light organics stripper LOS (not shown) for further processing or sent as a cooling liquid to the quench tower 102. In one aspect, the ratio of the percent evaporation to the weight percent of the polymer is about 73-75: 5.5.

In one aspect, it was found that significantly less fouling (fouling) was experienced when the evaporation percentage was about 74% than at an evaporation percentage of about 83%, while at the same time achieving a relatively high amount of polymer weight percent in the liquid residue, i.e., 5.5 weight percent versus 6.0 weight percent at an evaporation percentage of about 83%. This is a surprising result, as it would have been expected that the amount of fouling would be linearly related to the weight percent of polymer in the liquid residue.

It was found that there could be too much fouling (mainly on the tube side) in the fourth stage evaporator or heat exchanger 142 when the evaporation percentage was greater than about 83%. It was found that an evaporation percentage of about 73-75% significantly reduced the amount of fouling while providing a relatively high amount of polymer weight percent in the liquid residue.

Those skilled in the art will recognize that many modifications may be made thereto without departing from the spirit and scope of the present invention. For example, any number of stages may be employed in the evaporator system. Furthermore, although the low pressure stream is shown in the above description as a supply of heat necessary for all vaporization, any heat source may be employed. In a typical acrylonitrile purification and recovery plant, however, a low pressure stream, i.e., a saturated stream having a pressure of up to 100psig, typically about 20 to 60psig, is readily available and preferably utilized. The amount of water removed by the multi-effect evaporator in the stripper column may also vary primarily on an economic basis. Finally, it should also be understood that the multi-effect evaporator of the present invention need not be limited to use on stripper column residue as shown in the above description, but may be used to concentrate any other process stream that is recycled for use as a cooling liquid. For example, a multiple effect evaporator can be used to treat the extractive distillation column residue recycled in line 156 of FIG. 2 of U.S. Pat. No. 4,166,008. All such variations are intended to be included within the scope of the invention (which is to be limited only by the claims).

Quench tower operation

In one aspect, a process for operating a quench tower includes sending a reactor effluent to the quench tower and contacting the reactor effluent with water comprising polymer in an effluent extraction zone to provide an extracted effluent stream. The process also includes contacting the extracted effluent stream with sulfuric acid in an acid contact zone and removing the first stream to provide a first quench tower stream having about 10 weight percent or less of polymer. In one aspect, the process includes providing at least a portion of the water from the evaporator system. As explained herein, the water may be an aqueous condensate and/or a liquid residue.

In one aspect, 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) defines the amount of ammonium sulfate and the amount of polymer in the quench tower residue stream. In a related aspect, M1 is 1.5 or less and C1 is 30 or less. In one aspect, the process provides a quench tower residue stream having from about 10 to about 25 weight percent ammonium sulfate and less than about 5 weight percent polymer, and in another aspect from about 15 to about 21 weight percent ammonium sulfate and less than about 5 weight percent polymer. The quench tower residue stream has a pH of about 4.5 to about 6.0.

In another aspect, the process includes removing a second fluid to provide a second quench tower stream having more than about 10 weight percent polymer and less than about 5 weight percent ammonium sulfate.

In another aspect, at least a portion of the second quench tower fluid is recycled to the effluent extraction zone. The extracted effluent stream is countercurrent to the sulfuric acid. In one aspect, a first quench tower stream is removed above an effluent extraction zone. Adiabatic cooling may occur in the effluent extraction zone.

In an aspect, the process can include controlling an amount of make-up water sent to the quench tower and/or controlling an amount of sulfuric acid sent to the quench tower to obtain a concentration of ammonium sulfate in the quench tower residue stream of about 10 to about 25 weight percent. In an aspect, the process can include detecting a pH of a fluid residue of the quench tower residue and controlling a flow of sulfuric acid to the quench tower based on the detected pH of the fluid residue to obtain a quench tower residue stream having a pH of about 4.5-6.0. In an aspect, the process can include determining a concentration of ammonium sulfate in the quench tower residue stream based on a flow rate of sulfuric acid to the quench tower and a flow rate of the quench tower residue stream from or exiting the quench tower. In an aspect, the process may include adjusting the flow rate of make-up water and/or sulfuric acid sent 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 weight percent. By increasing the concentration of ammonium sulfate in the quench tower residue stream from 5-10 weight percent, as provided in conventional processes, to about 10 to about 25 weight percent, less water needs to be removed from the quench tower residue stream to obtain an even higher concentration of ammonium sulfate. It was found that a sulfate condenser can be used to effectively condense the quench tower residue stream to about 35-40 weight percent by increasing the concentration of ammonium sulfate in the quench tower residue stream to about 10 to about 25 weight percent.

Although the invention has been described in the foregoing description with respect to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention. It should be understood that the features of the present invention are susceptible to modification, alteration, change or substitution without departing from the spirit and scope of the present invention or the scope of the appended claims. For example, the size, number, size and shape of the various components may be varied to suit particular applications. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.