阅读说明：本技术 用于使烃进料流异构化的方法 (Process for isomerizing a hydrocarbon feedstream ) 是由 安东·姆利纳尔 N·帕特尔 詹森·L·诺伊 于 2020-01-31 设计创作，主要内容包括：本发明描述了一种用于使包含C4至C7烃中的至少一种的烃进料流异构化的方法。在干燥区中干燥该烃进料流,该干燥区被配置成提供干燥的烃进料流。在容器中利用该干燥的烃进料流吸收来自气体流的氯化物,该容器包括吸附区段,该吸附区段被配置成提供富氯化物的烃进料流和贫氯化物的蒸气。在异构化条件下,在异构化反应区中利用异构化催化剂使该富氯化物的烃进料流异构化以产生经异构化的流出物流。在稳定区中稳定该经异构化的流出物流以提供包含氯化物的稳定剂废气流和液体异构物流,其中该稳定剂废气流的至少一部分包含该气体流。(A process for isomerizing a hydrocarbon feedstream comprising at least one of C4 to C7 hydrocarbons is described. The hydrocarbon feedstream is dried in a drying zone configured to provide a dried hydrocarbon feedstream. Absorbing chloride from the gas stream with the dried hydrocarbon feedstream in a vessel comprising an adsorption section configured to provide a chloride-rich hydrocarbon feedstream and a chloride-depleted vapor. The chloride-rich hydrocarbon feed stream is isomerized in an isomerization reaction zone using an isomerization catalyst under isomerization conditions to produce an isomerized effluent stream. Stabilizing the isomerized effluent stream in a stabilization zone to provide a stabilizer off-gas stream comprising chloride and a liquid isomerized stream, wherein at least a portion of the stabilizer off-gas stream comprises the gas stream.)

1. For making a container contain C₄To C₇A method of isomerizing a hydrocarbon feedstream (102) of at least one of the hydrocarbons, the method comprising:

drying the hydrocarbon feed stream (102) in a drying zone (104) configured to remove water from the hydrocarbon feed stream (102) and provide a dried hydrocarbon feed stream (110);

adsorbing chloride from a gas stream (118) with the dried hydrocarbon feedstream (110) in a vessel (114) comprising an adsorption section (116) configured to provide a chloride-rich hydrocarbon feedstream (120) and a chloride-depleted vapor (166), wherein the temperature of the dried hydrocarbon feedstream (110) at the inlet of the vessel (114) is substantially equal to the temperature of the dried hydrocarbon feedstream (110) at the drying zone (104);

isomerizing the chloride-rich hydrocarbon feedstream (120) in an isomerization reaction zone (132) using an isomerization catalyst under isomerization conditions to produce an isomerized effluent stream (136); and the number of the first and second groups,

stabilizing the isomerized effluent stream (136) in a stabilization zone (138) to provide a stabilizer off-gas stream (142) comprising chloride and a liquid isomerate stream (144), wherein at least a portion of the stabilizer off-gas stream (142) comprises the gas stream (118).

2. The method of claim 1, wherein all of the dried hydrocarbon feedstream (110) is passed to the vessel (118).

3. The method of claim 1, further comprising:

bypassing the adsorption section (116) with a portion (110a) of the dried hydrocarbon feedstream (110).

4. The method of claim 3, wherein the vessel (114) has a first section comprising the adsorption section (116) and a second section comprising a surge section (162).

5. The method of claim 4, wherein the first section (116) is disposed vertically above the second section (162).

6. The process of claim 4 or 5, wherein the vessel (114) further comprises a cooler (164) disposed vertically above the first section (116), the cooler having an operating temperature between-40 ℃ and 4 ℃ (-40F to 40F).

7. The method of claim 4 or 5, wherein the second section (162) of the vessel (114) receives the portion (110a) of the dried hydrocarbon feedstream (110) that bypasses the adsorption section (116).

8. The method of any of claims 3 to 5, wherein the portion (110a) of the dried hydrocarbon feedstream (110) that bypasses the adsorption section (116) comprises between 5% to 40% (by volume) of the dried hydrocarbon feedstream (110).

9. The method of any of claims 3 to 5, further comprising:

monitoring a chloride level of the chloride-depleted vapor (166); and the number of the first and second groups,

adjusting a ratio of the portion (110a) of the dried hydrocarbon feedstream (110) that bypasses the adsorption section (116) to an amount of the dried hydrocarbon feedstream (110) passed to the adsorption section (116) based on the chloride level of the chloride-depleted vapor (166).

10. The method of any of claims 1 or 3 to 5, wherein the adsorption section (116) receives between 60% to 100% (by volume) of the dried hydrocarbon feedstream (110).

Background

C₈Alkylaromatic hydrocarbons are generally considered valuable products, with the highest demand for paraxylene. The major source of para-xylene includes mixed xylene streams from crude oil refining. Examples of such streams are C derived from catalytic reformate by a commercial xylene isomerization process or by separation by liquid-liquid extraction and/or fractionation₈Alkylaromatic hydrocarbon fractions.

Simulated moving bed ("SMB") adsorption processes are commercially used in large scale petrochemical separations to recover high purity para-xylene from mixed xylenes. As used herein, the term "mixed xylenes" refers to C₈A mixture of aromatic isomers comprising ethylbenzene, para-xylene, meta-xylene, and ortho-xylene. High purity para-xylene can be used to produce polyester fibers, resins, and films by converting para-xylene to terephthalic acid or dimethyl terephthalate, which is then reacted with ethylene glycol to form polyethylene terephthalate, as well as the raw materials for most polyesters.

The general techniques employed in the performance of SMB adsorptive separation processes are widely described and practiced. Generally, the process simulates a moving bed of adsorbent with a continuous countercurrent flow of liquid feed over the adsorbent. The feed and product continuously enter and exit the adsorbent bed in an almost constant composition. Separation of para-xylene relative to other C by use of adsorbent₈Affinity differences of aromatic isomers. More specifically for adsorbents relative to other C₈The initial affinity of the aromatic isomer for para-xylene is selected for the adsorbent.

For desorption of paraxylene, a desorbent is used which has a higher affinity for the adsorbent relative to paraxylene. One such desorbent is the desorbent, para-diethylbenzene, and the desorbent, para-diethylbenzene, is two carbon numbers heavier than xylene. It is also known to use the light desorbent toluene, which is only one carbon number lighter than the xylene feed. Toluene is relatively weak as a desorbent compared to p-diethylbenzene. Because toluene is weaker, a higher desorbent to feed ratio (D/F) and more energy are required for separation in the extract and raffinate fractionation columns.

A typical SMB adsorption process for para-xylene production produces a single extract stream rich in para-xylene and a single raffinate stream containing the remaining ethylbenzene, meta-xylene, and ortho-xylene from the feed. Two raffinate streams may also be obtained from processes such as those disclosed in us 20150087878a1 and us 20150266794a1 to yield one raffinate rich in ethylbenzene and another raffinate rich in meta-xylene and ortho-xylene. The two preferentially ethylbenzene-rich or depleted streams may then be processed separately downstream, such as in a separate xylene isomerization unit, to take advantage of the differences in the C8 aromatic composition.

Recently, us 9850186B2 has shown that two raffinates can be obtained, thereby allowing differences to be observed in both C8 aromatic hydrocarbon and toluene desorbent compositions. The two raffinates are then processed separately, with the desorbent-depleted raffinate passing directly from the desorbent-rich raffinate stream to a separate xylene isomerization unit. This configuration, while possible, requires the construction of two separate xylene isomerization units and the use of toluene as a desorbent, as well as the enrichment of different C8 aromatic species to take full advantage of the configuration.

Fig. 1A and 1B illustrate separation processes using a single raffinate stream with a light desorbent and a single raffinate stream with a heavy desorbent. Fig. 1A illustrates an adsorptive separation process 10 using a single raffinate stream and a heavy desorbent. C is to be₈The aromatic hydrocarbon feedstream 15 is sent to an adsorptive separation unit 20. A para-xylene extract stream 25 is recovered from the adsorptive separation unit 20. Will contain desorbent and other C₈The raffinate stream 30 of aromatics (ethylbenzene, meta-xylene, and ortho-xylene) is sent to a fractionation column 35 where it is separated intoContaining other C₈An overhead stream 40 of aromatic hydrocarbons and a bottoms stream 45 comprising desorbent. The bottoms stream 45 is recycled to the adsorptive separation unit 20. The overhead stream 40 is passed to an isomerization unit 50 where C is passed₈Aromatics are isomerized to produce additional para-xylene.

In fig. 1B, a light desorbent is used in process 75. In this case, raffinate stream 30 is separated into overhead stream 55 comprising desorbent and stream comprising other C' s₈A bottoms stream 60 of aromatic hydrocarbons. The bottoms stream 60 is sent to an isomerization unit 65.

Since fractionation is one of the largest energy users in an aromatics complex, it is desirable to reduce fractionation costs.

Accordingly, there is a need for an improved process for producing paraxylene with reduced operating costs.

Drawings

In the drawings of the invention, in which like numerals represent like elements, one or more embodiments are illustrated, and in which:

fig. 1A and 1B show a process flow diagram of a prior art process for producing para-xylene.

Fig. 2A and 2B show process flow diagrams of methods for producing para-xylene according to one or more embodiments of the present invention.

Definition of

As used herein, the term "stream" may include various hydrocarbon molecules and other materials.

As used herein, the terms "stream," "feed," "product," "fraction," or "portion" may include various hydrocarbon molecules such as straight and branched alkanes, cycloalkanes, alkenes, alkadienes, and alkynes, and optionally other substances such as gases, e.g., hydrogen, or impurities such as heavy metals, as well as sulfur and nitrogen compounds. Each of the above may also include aromatic hydrocarbons and non-aromatic hydrocarbons.

As used herein, the term "overhead stream" may mean a stream withdrawn at or near the top of a vessel (such as a column).

As used herein, the term "bottoms stream" can mean a stream withdrawn at or near the bottom of a vessel (such as a column).

Hydrocarbon molecules may be abbreviated as C1, C2, C3, Cn, where "n" represents the number of carbon atoms in one or more hydrocarbon molecules, or abbreviations may be used as adjectives for non-aromatic hydrocarbons or compounds, for example. Similarly, aromatic compounds may be abbreviated as a6, a7, A8, An, wherein "n" represents the number of carbon atoms in one or more aromatic molecules. In addition, the superscript "+" or "-" may be used for one or more hydrocarbon symbols of the abbreviation, such as C3+ or C3-, including one or more hydrocarbons of the abbreviation. By way of example, the abbreviation "C3 +" means one or more hydrocarbon molecules having three or more carbon atoms.

As used herein, the term "unit" may refer to a region that includes one or more items of equipment and/or one or more sub-regions. Items of equipment may include, but are not limited to, one or more reactors or reaction vessels, separation vessels, one or more adsorption chambers, rotary valves, distillation columns, heaters, exchangers, piping, pumps, compressors, and controllers. In addition, an equipment item such as a reactor, dryer, adsorption chamber, or vessel may also include one or more zones or sub-zones.

The term "column" means one or more distillation columns for separating one or more components of different volatile substances. Unless otherwise specified, each column includes a condenser at the top of the column for condensing a portion of the top stream and refluxing it back to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom stream and returning it to the bottom of the column. The feed to the column may be preheated. The top or overhead pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottom temperature is the liquid bottom outlet temperature. Unless otherwise indicated, overhead and bottoms lines refer to the net lines to the column from any reflux or reboiled column downstream. The stripping column omits the reboiler at the bottom of the column and instead provides the heating requirements and separation power for the liquefied inert medium (such as steam).

As shown in the figures, the process flow lines in the figures may be referred to interchangeably as, for example, lines, pipes, feeds, gases, products, discharges, components, parts, or streams.

The term "transfer" means the transfer of a substance from a conduit or container to an object.

The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer code (including source code, object code, or executable code). The term "communication" and its derivatives encompass both direct and indirect communication.

A "control system" is defined as a hardware and software computing component that determines the set point of a control element in the adsorption section.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following description.

Adsorptive separations are used to recover a variety of hydrocarbons and other chemical products. The disclosed chemical separation using this method includes: the separation of aromatic hydrocarbon mixtures into specific aromatic hydrocarbon isomers, the separation of linear and nonlinear aliphatic hydrocarbons and olefins, the separation of paraffins or aromatic hydrocarbons from feed mixtures containing both aromatic and paraffinic hydrocarbons, the separation of chiral compounds for pharmaceuticals and fine chemicals, the separation of oxygenates such as alcohols and ethers, and the separation of carbohydrates such as sugars. Aromatic separation comprises a mixture of dialkyl substituted monocyclic aromatics and dimethylnaphthalenes. The main commercial application forming the focus of the previous references and the following description of the invention without limiting it is from C₈The mixture of aromatic hydrocarbons recovers para-xylene and/or meta-xylene.

The present invention is generally applicable to adsorptive separation processes that simulate countercurrent movement of the adsorbent and surrounding liquid as described above.

Fractionation in a para-xylene production process is one of the largest energy users in modern aromatics complex. Thus, reducing fractionation costs results in improved economics.

It was confirmed from modeling that the use of two raffinate streams from the adsorption process produced significantly different stream compositions relative to the desorbent, as demonstrated in example 1 below.

Using the dual raffinate process, the two streams are fed independently into the raffinate column to take advantage of different desorbent concentrations. When this is done, and an additional tray is added between the two feed trays in the raffinate column, this results in significant reboiler duty savings and a reduction in the total combustion fuel required.

In the prior art, patents utilizing two raffinate streams have focused on C in each raffinate stream₈Differences in the composition of aromatic isomers (i.e., components in the feed separated in the process). They involve the use of a separate raffinate column and/or a separate isomerization unit, resulting in significantly increased capital costs.

In contrast, the present invention addresses the difference in the amount of desorbent in the two raffinate streams and sends those streams to a single fractionation column and a single isomerization, which reduces the capital cost of the system.

One aspect of the present invention is a process for producing para-xylene. In one embodiment, the process comprises separating C using a desorbent in a simulated moving bed apparatus₈A mixture of aromatic hydrocarbon isomers to produce a para-xylene-rich extract stream, a desorbent-rich raffinate stream, and a desorbent-lean raffinate stream, wherein the desorbent-rich raffinate stream has a greater concentration of desorbent than the desorbent-lean raffinate stream. Introducing a raffinate stream rich in desorbent and a raffinate stream lean in desorbent into a column having C₈An aromatic hydrocarbon outlet and a desorbent outlet, wherein a desorbent-rich raffinate stream is introduced at a first feed tray, and wherein a desorbent-lean raffinate stream is introduced at a second feed tray, and wherein the first feed tray is closer to the desorbent outlet than the second feed tray. Separating a desorbent-rich raffinate stream and a desorbent-poor raffinate stream in a fractionation column into C₈An aromatic stream and a desorbent stream.

In some embodiments, the method further comprises: will come from fractional distillationColumn C₈Introducing an aromatic stream into an isomerization zone; and let C₈Isomerization of aromatic streams to form isomerized C₈An aromatic stream.

In some embodiments, the method further comprises: isomerizing C₈The aromatics stream is recycled to the simulated moving bed unit, and wherein the isomerized aromatics stream comprises C₈At least a portion of the aromatic isomer mixture.

In some embodiments, the method further comprises: recycling a desorbent stream from the fractionation column to the simulated moving bed unit, and wherein the recycled desorbent stream comprises at least a portion of the desorbent in the simulated moving bed unit.

In some embodiments, the desorbent is a light desorbent, and wherein C is₈The aromatic hydrocarbon outlet is a bottom outlet, and the desorbent outlet is a top outlet.

In some embodiments, the light desorbent comprises toluene.

In some embodiments, the first feed tray is separated from the second feed tray by 5 to 15 trays.

In some embodiments, the desorbent is a heavy desorbent, and wherein C is₈The aromatic hydrocarbon outlet is a top outlet and the desorbent outlet is a bottom outlet.

In some embodiments, the heavy desorbent comprises para-diethylbenzene.

In some embodiments, the first feed tray is separated from the second feed tray by 25 to 30 trays.

In some embodiments, the desorbent-rich raffinate stream comprises from 45 wt% to 65 wt% desorbent, and the desorbent-poor raffinate stream comprises from 10 wt% to 35 wt% desorbent.

In some embodiments, the method further comprises at least one of: sensing at least one parameter of the method and generating a signal or data from the sensing; generating and transmitting a signal; or generate and transmit data.

Another aspect of the invention is a process for producing para-xylene. In one embodiment, the methodThe method comprises the following steps: separation of C using desorbent in simulated moving bed apparatus₈A mixture of aromatic hydrocarbon isomers to produce a para-xylene-rich extract stream, a desorbent-rich raffinate stream, and a desorbent-lean raffinate stream, wherein the desorbent-rich raffinate stream has a greater concentration of desorbent than the desorbent-lean raffinate stream. Direct introduction of a desorbent-rich raffinate stream and a desorbent-lean raffinate stream into a column having C₈An aromatic hydrocarbon outlet and a desorbent outlet, wherein a desorbent-rich raffinate stream is introduced at a first feed tray, and wherein a desorbent-lean raffinate stream is introduced at a second feed tray, and wherein the first feed tray is closer to the desorbent outlet than the second feed tray. The desorbent rich raffinate stream and the desorbent lean raffinate stream in the fractionation column are separated into an aromatic stream and a desorbent stream. C from the fractionating tower₈An aromatic stream is introduced into the isomerization zone. Make C₈The aromatic stream is isomerized to form an isomerized aromatic stream. Recycling the isomerized C8 aromatics stream to the simulated moving bed unit, and wherein the isomerized C is₈The aromatic stream comprises C₈At least a portion of the aromatic isomer mixture.

In some embodiments, the method further comprises: recycling a desorbent stream from the fractionation column to the simulated moving bed unit, and wherein the recycled desorbent stream comprises at least a portion of the desorbent in the simulated moving bed unit.

In some embodiments, the desorbent is a light desorbent, and wherein C is₈The aromatic hydrocarbon outlet is a bottom outlet, and the desorbent outlet is a top outlet.

In some embodiments, the first feed tray is separated from the second feed tray by 5 to 15 trays.

In some embodiments, the desorbent is a heavy desorbent, and wherein C is₈The aromatic hydrocarbon outlet is a top outlet and the desorbent outlet is a bottom outlet.

In some embodiments, the first feed tray is separated from the second feed tray by 25 to 30 trays.

In some embodiments, the desorbent-rich raffinate stream comprises from 45 wt% to 65 wt% desorbent, and the desorbent-poor raffinate stream comprises from 10 wt% to 35 wt% desorbent.

In some embodiments, the desorbent comprises a light desorbent comprising toluene, or the desorbent comprises a heavy desorbent comprising para-diethylbenzene.

Fig. 2A and 2B illustrate separation processes using the dual raffinate stream process of the present invention with a light desorbent and a heavy desorbent. The light desorbent has a carbon number less than xylene and the heavy desorbent has a carbon number greater than xylene.

When heavy desorbent is used in the process 100, the desorbent is discharged from the bottom of the column, as shown in figure 2A. Suitable heavy desorbents include, but are not limited to, p-diethylbenzene. In this case, the main raffinate, which contains the most desorbent, is located closer to the bottom of the column.

C is to be₈Aromatic hydrocarbon feedstream 110 is sent to an adsorptive separation unit 115 where para-xylene is separated from the xylene mixture using an SMB unit. The SMB process is a commercial adsorptive separation process that uses several adsorption beds and moves an inlet stream and an outlet stream between the beds, with a process stream comprising para-xylene passing through the beds. The adsorbent bed contains an adsorbent for preferentially adsorbing para-xylene and the para-xylene is later desorbed using a desorbent as the process stream. As is known in the art, the SMB technology is an established commercial technology in which an adsorbent bed is held in place in one or more generally cylindrical adsorption chambers, and the locations at which streams involved in the process enter and leave the chambers are slowly shifted along the length of the chambers. Typically, at least four streams (feed, desorbent, extract and raffinate) are employed in the procedure, and the positions at which the feed and desorbent streams enter the chamber via separate bed lines and the extract and raffinate streams exit the chamber via other bed lines are simultaneously shifted in the same direction at set intervals. Each shift in the position of these transfer points delivers or removes liquid from a different bed within the adsorption chamber. This shift may be performed using dedicated bed lines for each stream at each bed inlet. However, large scale SMB technology process units will typically beThere are at least eight individual beds, or at least twelve individual beds, or at least sixteen individual beds or up to twenty-four individual beds. The use of separate bed lines for each stream at each bed would greatly increase the cost of the process and therefore these bed lines are reused, with each bed line carrying one of the four process streams at some point in the cycle and valves, such as swing valves, controlling the flow of the four streams throughout the unit.

The SMB process produces at least two effluent streams: an extract stream containing compounds selectively retained on the adsorbent; and a raffinate stream containing compounds that are not strongly adsorbed. Both the extract stream and the raffinate stream will also contain desorbent. The concentration of desorbent in the extract and raffinate streams will vary somewhat over time during each incremental shift of the process bed line. The extract and raffinate streams are typically passed to extract and raffinate fractionators where desorbent is separated from the extract and raffinate compounds, respectively. In this manner, the desorbent is recovered and can then be recycled to the adsorption zone as a process stream (referred to herein as the desorbent stream). Each bed will contain adsorbent, discussed in more detail below.

The adsorbent preferentially adsorbs paraxylene while allowing substantially passage of metaxylene, orthoxylene, and ethylbenzene under unaltered conditions and as part of the raffinate stream. Thereafter, the adsorbed paraxylene is desorbed from the adsorbent by passing the desorbent through the adsorbent bed to form an extract stream. The desorbent material often also serves to flush unadsorbed material from void spaces around and within the adsorbent.

The adsorption and desorption steps can be performed in a single large adsorbent bed or on a table-based basis in several parallel beds. However, it has been found that simulated moving bed adsorptive separation provides several advantages, such as high purity and recovery. Thus, many commercial scale petrochemical separations, particularly those used to separate xylenes and mixed normal paraffins, are performed using SMB technology. Further details regarding the equipment and techniques used in SMB processes may be found in US 3,208,833; US 3,214,247; US 3,392,113; US 3,455,815; US 3,523,762; US 3,617,504; US 4,006,197; US 4,133,842; US 4,434,051; and other patents.

The para-xylene extract stream 120 is removed from the adsorptive separation unit 115 and may be further processed as desired.

Will contain desorbent and other C₈The desorbent rich raffinate stream 125 of aromatic hydrocarbons is sent to a fractionation column 135. The term "rich" is intended to indicate that the concentration of a specified compound or class of compounds is greater than 45 wt%, or in the range of 45 wt% to 65 wt%. Will contain desorbent and other C₈A desorbent-lean raffinate stream 130 of aromatic hydrocarbons is also sent to the fractionation column 135. The term "lean" is intended to indicate that the concentration of a specified compound or class of compounds is less than 35 wt.%, or in the range of 10 wt.% to 35 wt.%.

The raffinate rich desorbent stream 125 contains more desorbent than the desorbent lean stream 130. Thus, the desorbent-rich raffinate stream 125 enters the fractionation column closer to the desorbent-containing bottoms stream 140 than the desorbent-lean raffinate stream 130.

The desorbent rich raffinate stream 125 feed trays are separated from the desorbent lean raffinate stream 130 by 25-30 trays.

Separating the desorbent-rich raffinate stream 125 and the desorbent-lean raffinate stream 130 into a desorbent-containing bottoms stream 140 and a raffinate stream comprising other C' s₈An overhead stream 145 of aromatic hydrocarbons. The bottoms stream 140 is recycled to the adsorptive separation unit 115. The bottoms stream 140 contains 98 wt.% or more, or 98.5 wt.% or more, or 99 wt.% or more, or 99.5 wt.% or more of heavy desorbent. Overhead stream 145 is sent to isomerization unit 150 for isomerization to more desired aromatic hydrocarbons, including para-xylene.

In the process 200 shown in fig. 2B, a light desorbent is used. When light desorbent is used, the stream with more desorbent is fed to a location closer to the top of the column because the desorbent is considered to be the top stream, and C is₈The aromatic hydrocarbon is considered as a bottoms stream. In this case, the desorbent-rich raffinate stream 225 is depleted in desorbent relative to the desorbent-lean raffinate streamLiquid stream 230 is closer to the overhead stream. The desorbent rich raffinate stream 225 feed trays are separated from the desorbent lean raffinate stream 230 feed trays by 5-15 trays.

Separating the desorbent-rich raffinate stream 225 and the desorbent-lean raffinate stream 130 into an overhead stream 240 comprising desorbent and a stream comprising other C₈A bottoms stream 245 of aromatic hydrocarbons. The bottoms stream 245 is sent to an isomerization unit 250. The overhead stream 240 contains 95 wt.% or more, or 96 wt.% or more, or 97 wt.% or more, or 98 wt.% or more, or 99 wt.% or more, or 99.5 wt.% or more light desorbent.

A description of the prior art and the method and apparatus of the present invention is presented with reference to the accompanying drawings. The drawings are simplified illustrations of prior art and various embodiments of the invention, and are not intended to unduly limit the broad scope of the description provided herein and the claims that follow. Certain hardware, such as valves, pumps, compressors, heat exchangers, instrumentation and controls, have been omitted because such hardware is not necessary for a clear understanding of the present invention. The use and application of such hardware is well within the skill of the art.

Any of the above-described lines, conduits, units, devices, containers, surroundings, areas, or the like may be equipped with one or more monitoring components, including sensors, measurement devices, data capture devices, or data transmission devices. The signals, process or condition measurements, and data from the monitoring components can be used to monitor conditions in, around, and associated with the process tool. The signals, measurements, and/or data generated or recorded by the monitoring component may be collected, processed, and/or transmitted over one or more networks or connections, which may be private or public, general or private, direct or indirect, wired or wireless, encrypted or unencrypted, and/or combinations thereof; the description is not intended to be limited in this respect. Fig. 2A and 2B classify the above as 160, 260.

The signals, measurements, and/or data generated or recorded by the monitoring component may be transmitted to one or more computing devices or systems. A computing device or system may include at least one processor and memory storing computer-readable instructions that, when executed by the at least one processor, cause the one or more computing devices to perform a process that may include one or more steps. For example, one or more computing devices may be configured to receive data from one or more monitoring components relating to at least one piece of equipment associated with the process. One or more computing devices or systems may be configured to analyze the data. Based on the data analysis, one or more computing devices or systems may be configured to determine one or more recommended adjustments to one or more parameters of one or more processes described herein. One or more computing devices or systems may be configured to transmit encrypted or unencrypted data including one or more recommended adjustments to one or more parameters of one or more processes described herein.

Example 1

Using typical zeolite-type adsorbents known to those skilled in the art for separating and purifying paraxylene, the separation system was modeled using a computer modeling program based on the following feed and desorbent compositions and flow rates, an operating temperature of 156 ℃ (312 ° f), and a cycle time of 34 minutes.

As shown in table 1, when a two raffinate stream system was used, the main raffinate stream contained 60 wt.% desorbent, while the second raffinate stream contained 30 wt.% desorbent. If the two streams are mixed together, as is the case with a single raffinate design, the resulting stream will contain 50 wt.% desorbent. By feeding the two streams separately to a single raffinate column and adding five trays between the two feeds, the reboiler duty of the column was reduced by 3.9% relative to the single raffinate case.

TABLE 1

Case 1-two separate raffinate streams to a Single raffinate column

Case 2-Single Combined raffinate stream to Single raffinate column

Example 2

Two raffinate systems were also experimentally investigated using a simulated moving bed pilot plant and p-diethylbenzene desorbent. The pilot plant was operated at 177 ℃ (350 ° f) and 27 minute cycle times and used zeolite-based adsorbents known to those skilled in the art suitable for separation and purification of para-xylene. The feed and desorbent rates and compositions for this experiment were as follows:

when 25.5% of the total raffinate was used as the second raffinate, the resulting raffinate composition is shown in table 2. Table 2 shows the significantly different composition of p-diethylbenzene in the two raffinates. C of two raffinates once the desorbent is fractionated from the stream₈The aromatic composition is similar as it would be in a downstream raffinate column. By feeding the two raffinates separately to a single raffinate column and adding twenty trays between the feeds, the reboiler duty was reduced by 1.8% relative to the single raffinate case.

TABLE 2

Those of ordinary skill in the art will recognize and appreciate that various other components, such as valves, pumps, filters, coolers, etc., are not shown in the figures, as it is believed that their specifics are well within the purview of one of ordinary skill in the art and their description is not necessary to the implementation or understanding of the embodiments of the present invention.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.

Detailed description of the preferred embodiments

While the following is described in conjunction with specific embodiments, it is to be understood that this description is intended to illustrate and not limit the scope of the foregoing description and the appended claims.

A first embodiment of the invention is a process for producing para-xylene comprising separating C using a desorbent in a simulated moving bed apparatus₈A mixture of aromatic hydrocarbon isomers to produce a para-xylene-rich extract stream, a desorbent-rich raffinate stream, and a desorbent-lean raffinate stream, wherein the desorbent-rich raffinate stream has a greater concentration of desorbent than the desorbent-lean raffinate stream; introducing the desorbent-rich raffinate stream and the desorbent-lean raffinate stream into a column having C₈An aromatics outlet and a desorbent outlet, wherein the desorbent-rich raffinate stream is introduced at a first feed tray, and wherein the desorbent-lean raffinate stream is introduced at a second feed tray, and wherein the first feed tray is closer to the desorbent outlet than the second feed tray; and separating the rich desorbent from the fractionation columnThe raffinate stream and the desorbent depleted raffinate stream are separated into C₈An aromatic stream and a desorbent stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, the method further comprising: c from the fractionating column₈Introducing an aromatic stream into an isomerization zone; and let C₈Isomerization of aromatic streams to form isomerized C₈An aromatic stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, the method further comprising: subjecting the isomerized C₈The aromatics stream is recycled to the simulated moving bed unit, and wherein the isomerized aromatics stream comprises C₈At least a portion of a mixture of aromatic isomers. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, the method further comprising: recycling the desorbent stream from the fractionation column to the simulated moving bed unit, and wherein the recycled desorbent stream comprises at least a portion of the desorbent in the simulated moving bed unit. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the desorbent is a light desorbent, and wherein the C is₈The aromatics outlet is the bottom outlet and the desorbent outlet is the top outlet. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the light desorbent from the overhead outlet comprises toluene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the first feed tray is separated from the second feed tray by 5 to 15 trays. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the desorbent is a desorbent, and wherein the C₈The outlet of aromatic hydrocarbon is the top of the towerA port, and the desorbent outlet is a bottom outlet. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the heavy desorbent from the bottom outlet comprises para-diethylbenzene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the first feed tray is separated from the second feed tray by 25 to 30 trays. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the desorbent-rich raffinate stream comprises from 45 wt% to 65 wt% desorbent and the desorbent-poor raffinate stream comprises from 10 wt% to 35 wt% desorbent. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the method further comprises at least one of: sensing at least one parameter of the method and generating a signal or data from the sensing; generating and transmitting a signal; or generate and transmit data.

A second embodiment of the invention is a process for producing para-xylene comprising separating C using a desorbent in a simulated moving bed apparatus₈A mixture of aromatic hydrocarbon isomers to produce a para-xylene-rich extract liquid stream, a desorbent-rich raffinate stream, and a desorbent-lean raffinate stream, wherein the desorbent-rich raffinate stream has a greater concentration of desorbent than the desorbent-lean raffinate stream; introducing the desorbent-rich raffinate stream and the desorbent-lean raffinate stream directly into a column having C₈An aromatics outlet and a desorbent outlet, wherein the desorbent-rich raffinate stream is introduced at a first feed tray, and wherein the desorbent-lean raffinate stream is introduced at a second feed tray, and wherein the first feed tray is closer to the desorbent outlet than the second feed tray; separating the desorbent rich raffinate stream and the desorbent lean raffinate stream in the fractionation column into an aromatic stream and a desorbent stream; will be provided withThe C from the fractionating column₈Introducing an aromatic stream into an isomerization zone; make the C to₈Isomerizing the aromatics stream to form an isomerized aromatics stream; and subjecting the isomerized C₈The aromatics stream is recycled to the simulated moving bed unit, and wherein the isomerized C₈The aromatic hydrocarbon stream contains C₈At least a portion of the aromatic isomer mixture. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, the method further comprising: recycling the desorbent stream from the fractionation column to the simulated moving bed unit, and wherein the recycled desorbent stream comprises at least a portion of the desorbent in the simulated moving bed unit. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the desorbent is a light desorbent, and wherein the C is₈The aromatics outlet is the bottom outlet and the desorbent outlet is the top outlet. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the first feed tray is separated from the second feed tray by 5 to 15 trays. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the desorbent is a desorbent, and wherein the C₈The aromatic outlet is the top outlet and the desorbent outlet is the bottom outlet. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the first feed tray is separated from the second feed tray by 25 to 30 trays. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the desorbent-rich raffinate stream comprises from 45 wt% to 65 wt% desorbent and the desorbent-poor raffinate stream comprises from 10 wt% to 35 wt% desorbent. An embodiment of the invention is a previous implementation in this paragraphScheme one, any or all of second embodiments in this paragraph wherein the desorbent comprises a light desorbent comprising toluene or the desorbent comprises a heavy desorbent comprising para-diethylbenzene.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent and can readily ascertain the essential characteristics of the present invention without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. Accordingly, the foregoing preferred specific embodiments are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever, and is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

In the foregoing, all temperatures are shown in degrees celsius and all parts and percentages are by weight unless otherwise indicated.