WO2009012623A1

WO2009012623A1 - A non-cryogenic separation method for lower hydrocarbon containing light gas

Info

Publication number: WO2009012623A1
Application number: PCT/CN2007/002884
Authority: WO
Inventors: Jinfang Ni; Lixin Li
Original assignee: Shanghai Wison Chemical Engineering Co., Ltd
Priority date: 2007-07-25
Filing date: 2007-10-08
Publication date: 2009-01-29
Also published as: CN101353286A; CN101353286B

Abstract

Disclosed is a non-cryogenic separation method for lower hydrocarbon containing light gas, which comprises the following steps: (1)cooling the pretreated gas from outlet of reactor to 10°C~-37°C, then feeding the gas into pre-cutting column; (2) feeding the cooled overhead product of pre-cutting column into absorption column, and absorbing C2 hydrocarbons of overhead product of pre-cutting column with the absorption agent comprising of C3, C4, C5 or its mixture of hydrocarbons; and (3) feeding the bottom product of pre-cutting column into deethanizer to make clearity cutting of C2 and C3, and obtaining C2-fraction from the overhead of deethanizer and C3 and its heavier component from the bottom of deethanizer.

Description

Non-cryogenic low-carbon hydrocarbon separation method containing light gas

Technical field

The invention belongs to the technical field of light hydrocarbon separation, and particularly relates to a separation method in the process of converting oxides to olefins and cracking hydrocarbons to obtain olefins. Background technique

Ethylene and propylene are the basic raw materials for the petrochemical industry and have been obtained in the past by steam cracking or catalytic cracking of hydrocarbons. In the case of increasingly tight oil supplies, processes have been developed for the production of light olefins using oxides, particularly methanol and ethanol. Alcohols can be produced from natural gas or coal syngas, thus avoiding the use of petroleum resources.

The product composition of the oxide conversion process is similar to that of the cracking furnace outlet product of hydrocarbon cracking to ethylene, and is a light gas such as hydrogen, nitrogen and light hydrocarbons, i.e., C1 to C5 saturated hydrocarbons and unsaturated hydrocarbons. Separating this mixture into a variety of high purity products requires a very complex separation process.

In the process of separation of traditional hydrocarbon cracking ethylene, cryogenic separation is widely used. The typical separation process can be broadly divided into three categories, namely, the sequential process of removing the formazan, the pre-deacetylation process, and the pre-de-propylation process. Taking the sequential process as an example, the cracked gas from the cracking furnace is quenched, compressed, dried, and then cooled into a deep cold degassing methane system, and then the material of the demethylated tartaceous column is successively introduced into the deacetylation tower, the depropanizer tower, and the deacetylation tower. The alkylbenzene, then the carbon distillate and the carbon tri fraction are separately rectified to obtain polymer grade ethylene and propylene. Chinese patent ZL 92100471.0 proposes a pre-cutting process different from the above three processes. The first separator of the process is a non-clear cutting tower of carbon distillate, and the classic sequential process or pre-de-acetaming process or before Compared with the depropanation process, the amount of gas entering the cryogenic system and the load of the deaerator tower are reduced, and the measure of increasing the utilization level of the cold is adopted to compensate for the lowering of the condensation temperature due to the cutting of some heavier components. The disadvantage of moving. However, no matter which process requires cryogenic separation for the separation of formazan, hydrogen and carbon dihydrocarbons, it is necessary to provide a variety of different specifications of cooling capacity from propylene compressors and ethylene compressors, for example, requiring an ethylene refrigeration compressor - 100° The amount of cold in C. For low-pressure demethanization, it is also necessary to have a compression compressor to provide a cooling capacity of around 135 °C. In addition to complex refrigeration compressor systems, sophisticated cold box equipment is required, making the cryogenic separation process complex and expensive.

In order to avoid the shortcomings of the cryogenic separation process described above, UOP has developed a process for the production of ethylene: "PROCESS FOR PRODUCING ETHYLENE" WO 01/25] 74. The main features of this method are: The pre-de-ethane removal process is used to reduce the amount of feed to the demethylation tower.

Compared with the conventional apparatus for cracking ethylene to produce ethylene, the ethylene content in the top product of the demethylated tower is increased, thereby increasing the temperature of the top of the demethanizer and avoiding the cooling of ethylene.

In order to recover the ethylene in the top gas of the demethylation tower, the gas is sent to a pressure swing adsorption facility to separate formazan, hydrogen and ethylene, and the recovered ethylene is returned to the oxidation reactor outlet material.

According to the patent specification, the process is similar to the conventional separation device for naphtha cracking.

99.5% ethylene recovery, ethylene concentration in ethylene products can reach more than 99.5%. This patent uses a pre-de-acetazone column to reduce the feed to the demethalogenation system, but still contains all of the carbon distillate.

The separation method has low investment in equipment, but due to the adoption of PSA technology, the operation procedure is complicated and the system maintenance workload is large.

U.S. Patent No. 5,326,929 and U.S. Patent No. 5,219, 007 disclose the use of a solvent for the separation of hydrogen, methane and carbon components. The main process of the process is: Feeding into a demethylation absorption tower with an intermediate cooling and reboiler, the column uses C5 from the formazan absorption tower as solvent to absorb carbon dioxide and heavier components, and the overhead gas is Methane hydrogen and entrained carbon dioxide and solvent, the tower is a solvent that absorbs carbon two and carbon three. The gas at the top of the demethanizer absorption tower enters the formazan absorption tower, and the solvent at the outlet of the regenerator absorbs methane and carbon two, and the outlet gas at the top of the tower is a hydrogen product. The solvent that absorbed the formazan and heavier components was removed from the tower of the formazan absorption tower to the demethylation absorption tower. The kettle liquid of the demethanizer absorption tower is a solvent that absorbs a large amount of ethylene propylene and must be regenerated by a regenerator. The carbon dioxide and carbon three desorbed from the regenerator are desorbed, and the regenerated solvent is recycled to the dealkylation absorption tower. Although this method avoids multi-stage ethylene refrigeration compressors and cold boxes, the number of molecules required for the solvent is almost equal to the sum of the number of molecules of ethylene and propylene fed. Such a large amount of solvent is recycled and regenerated, and then cooled and absorbed, and the energy consumed is large. When US 5326929 uses C5 as the solvent, when the ethylene content in the feed is 4763.3 lb mole/hr, the solvent is required to be 5651.8 lb mole/h, and the ratio of solvent to carbon two is 1.186. The process regenerates the solvent at pressures greater than 3.2 mpa and the regeneration temperature is high, possibly as high as 150 °C. The solvent was then cooled to -50 ° C and passed to a methane absorption column. With such a large amount of solvent heating and then cooling the cycle, the energy consumption is significant.

Chinese patent CN 1847203 A proposes a separation process for methanol conversion to produce low-carbon olefin gas. The process is similar to the pre-dehydration and pre-hydrogenation process of the hydrocarbon cracking unit, but the feed to the demethylation tower is eliminated. The graded cooling cold box system increases the feed temperature of the de-arming tower and simplifies the cryogenic de-arming system. Packaging requirements. ' Invention content OBJECT OF THE INVENTION The object of the present invention is to provide a non-light gas-containing non-defective product with low investment, low energy consumption, high material recovery rate, simple operation, small maintenance, and reliable operation. Cryogenic low carbon hydrocarbon separation process.

The object of the present invention can be achieved by the following technical solutions: A method for separating non-cryogenic low-carbon hydrocarbons containing light gases, characterized in that the method comprises the following steps:

(1) The pretreated reactor outlet gas is cooled to 10 ° C ~ - 37 Torr and sent to a pre-cutting tower, the top product including formazan, hydrogen and other light gases, a partial carbon distillate and phase equilibrium a small amount of carbon three, the tower product is the remaining carbon two and heavier components;

(2) The overhead product of the pre-cutting tower is cooled and sent to an absorption tower, and the carbon dioxide in the top product of the pre-cutting tower is adsorbed by an absorbent composed of a mixture of carbon tris, carbon tetra, carbon five or a hydrocarbon thereof. The hydrocarbons are absorbed, the light gas is discharged from the top, and the column product is returned to the pre-cutting tower as a feed;

(3) The tower product of the pre-cutting tower is sent to the decoupling tower for clear cutting of carbon two and carbon three, and the carbon dioxide fraction is obtained at the top of the tower; the product of the tower is carbon three and heavier components, if entering the pre-cutting tower The feed contains acetylene, and the overhead product is first removed from the acetylene and then passed to the ethylene rectification column for purification to the desired mass concentration.

The pretreatment described in the step (1) is to pressurize the reactor outlet gas to 2.0 to 4.0 MPa to remove acid gas and moisture.

The pretreatment described in the step (1) is that the reactor outlet gas is subjected to compression cooling to remove the acid gas and dried, and then enters the high pressure depropanizer column, and the high pressure depropanizer column top gas is further pressurized to 2.0 to 4.0 MPa and then enters. The acetylene hydrogenation reactor removes the alkyne or goes to the pre-cutting column.

The pre-cutting tower described in the step (1) is a non-clear cutting rectification column of carbon distillate, and the carbon dioxide fraction of the top of the column may account for 5% to 70% of the carbon of the feed; the other light gases include nitrogen. , oxygen.

The cooling described in the step (2) is carried out using a propylene refrigerant or an ethylene refrigerant having a temperature of -50 ° C to - 66 ° C. The absorption tower described in the step (2) adopts an absorbent containing carbon trioxide as a main component, and divides the discharge of the deethanization tower into two, and a part is used as a feed of the depropylation tower to carry out carbon tri and carbon four. The other part is cooled to below -50 ° C and sent to the absorption tower as an absorbent. The amount of the absorbent is 5% to 90% of the discharge amount of the decarburization column, and the top of the de-propanizer tower is ejected. The material is carbon three, including all carbon three components fed into the cutting tower. If the carbon three components contain alkynes, the alkyne should be removed first and then separated into propylene, propylene and other pure components by precise separation. The product of the tower is carbon tetragen and heavier components, and is sent to the butyl sulphide to separate the carbon four from the carbon five.

The absorption tower described in the step (2) adopts an absorbent containing carbon tetrachloride as a main component, and divides the discharge of the depropanizer column into two, and a part of which is used as a feed of the debutanizer to carry out carbon four and carbon five. Separating; the other part is cooled to not higher than -50 ° C and sent to the absorption tower as an absorbent. The amount of the absorbent is the amount of the carbon kettle. 20%~95%.

The absorption tower described in the step (2) adopts an absorbent containing carbon five as a main component, and the distillate tower tray discharge can be divided into two parts, one part is sent out as a carbon five finished product, and the other part is cooled to After being not higher than -50 ° C, it is sent to the absorption tower as an absorbent, and the amount of the absorbent may be 30% to 98% of the discharge amount of the column.

The top outlet gas of the absorption tower contains a small amount of absorbent. When the content of the absorbent exceeds the requirement, the outlet gas of the absorption tower enters a cooling condenser to reduce the absorbent content, and the condensing cooler tail gas can be re-entered into the separation facility. For further separation, the separation facility includes pressure swing or membrane separation.

Compared with the prior art, the present invention is a process for separating light hydrocarbon-containing low-carbon hydrocarbons without using a deep-cooling cold box and a demethylation tower, using only propylene refrigerant and first-grade low-grade ethylene refrigerant. The ethylene content of the ethylene product obtained by the method is greater than 99.95%, and the ethylene recovery rate is greater than 99.6%.

By adopting the above process, the carbon dioxide fraction contained in the pre-cut bottom tank liquid is greater than 99.8% of the feed, and the carbon triazine content is greater than 99.5% of the feed, which has a high material recovery rate. The separation of formazan, hydrogen and carbon di fractions of the present invention is accomplished in two steps. In the first step, 30%~95% of carbon dioxide is separated from formazan and hydrogen by a pre-cutting tower. In the second step, the carbon dioxide is absorbed by the solvent in the absorption tower to achieve complete separation of carbon two and methane hydrogen. The feed to the absorber is cooled with a coolant to a temperature not higher than -50 °C. Since carbon dioxide has been largely removed before entering the absorption column, the amount of solvent required is much less than the solvent absorption and separation method in which all other carbon distillates enter the absorption column, and the regeneration of the solvent passes through the pre-cutting tower. Distillation is achieved. The steps of compression, methanol removal, dimethyl ether removal and drying are not carried out before the pre-cutting tower. Therefore, the energy consumption is low, the operation is simple, the maintenance amount is small, and the operation is reliable. DRAWINGS

Figure 1 shows the carbon three oil absorption process of the pre-cutting tower;

Figure 2 shows the carbon four oil absorption process of the pre-cutting tower;

Figure 3 shows the carbon five oil absorption process of the pre-cutting tower;

Figure 4 shows the separation process of pre-depropanation with carbon trioxide as the absorbent. detailed description

The present invention contemplates a process for separating light hydrocarbon-containing low carbon hydrocarbons without the use of a cryogenic cold box and a demethylation rectification column using only propylene refrigerant and a first stage low grade ethylene refrigerant. This process has low investment and low energy consumption. The present invention may employ a feed which is subjected to compression, removal of acid gas, and drying at the outlet of the reactor, and may also be passed after the propane is removed. After the imported raw materials are cooled to 10 Ό to -37 Ό, the two phases of the gas and liquid are separated into the cutting tower. The column is a non-clear cutting distillation column of carbon distillate, and the top product includes formazan, hydrogen and possibly other light gases (such as a small amount of nitrogen and oxygen) and a partial carbon distillate, and the top carbon distillate can be It accounts for 10% to 70% of the feed carbon 2; the bottom product is the remaining carbon two and all the heavier components. The overhead product of the pre-cutting tower is cooled by an ethylene refrigerant having a temperature higher than -66 ° C and sent to an absorption tower. The carbon tris or carbon tetra or carbon five or a mixture of these hydrocarbons is used as an absorbent, and the pre-cut tower is used. The carbon dihydrocarbons in the top product are absorbed and the light gases are discharged from the top. The overhead gas of the absorber contains a small amount of adsorbent, the amount of which is related to the proportion of light gas in the feed, the temperature of the inlet material of the absorber, and the nature of the absorbent. Under reasonable process conditions, when the composition of the absorbent is mainly carbon three, the carbon content of the outlet gas is in the range of 2% to 10%, and can enter a cooling condenser to condense part of the carbon to reduce loss. To further reduce the carbon trioxide content or purify the hydrogen, the off-gas of the cooling condenser can be re-introduced into other separation facilities, such as pressure swing or membrane separation. The kettle liquid of the absorption tower is returned to the pre-cutting tower as a feed. When the absorbent is carbon tetra or carbon five, a cooling condenser may be provided at the outlet of the absorption tower if it is necessary to further reduce the absorbent content for various reasons.

The tower product of the pre-cutting tower is sent to the decoupling column for clear cutting of carbon two and carbon three, and the carbon distillate obtained from the top of the deethanizer is separated into ethylene rectification column and separated into ethylene and ethane; Carbon three and heavier components. If the feed to the pre-cut column contains acetylene, the top product of the deacetamer column needs to be removed from the acetylene before entering the ethylene rectification column. If the absorption tower adopts an absorbent containing carbon trioxide as a main component, the de-ethanation tower can be divided into two (see FIG. 1), and a part of the de-propanizer is fed as carbon three and carbon four. Separate; another part is pumped and cooled and sent to the absorption tower as an absorbent. The amount of the absorbent may be from 5% to 90% of the discharge amount of the decarburization column. When the absorption tower uses carbon trioxide as the absorbent, the overhead vapor gas contains a gas phase carbon trioxide content balanced with the liquid phase carbon three phase. In order to reduce the loss of carbon three, a cooling condenser can be arranged at the top of the absorption tower to condense part of the carbon in the outlet gas to increase the recovery rate.

The top of the depropanizer is discharged from carbon three, including all carbon three components fed to the cutting column. The carbon triester obtained at the top of the depropanizer column is passed to a propylene rectification column to be separated into propylene and propylene. If the carbon three component contains an alkyne, the alkyne should be removed first and then separated into pure components by distillation; the column product is carbon tetra and heavier.

If the absorption tower adopts an absorbent containing carbon four as a main component, the depropanization tower bottom discharge can be divided into two (see Fig. 2), and a part of the debutmentation tower as a feed for the separation of carbon four and carbon five. The other part is pumped and cooled and sent to the absorption tower as an absorbent. The amount of absorbent can be 20 %~95%. If the content of the C4 fraction in the feed is too low and the driving time of the absorbent necessary for accumulation is too long, carbon tetragen may be injected into the depropanizer column at one time as an absorbent for recycling.

If the absorption tower adopts the absorbent containing carbon five as the main component, the discharge of the dibutyl ruthenium tray can be divided into two (see Fig. 3), one part is sent out as a carbon five finished product; the other part is pumped and After cooling, it is sent to an absorption tower as an absorbent. The amount of the absorbent may be 30 to 98% of the amount of the carbon kettle discharged. If the C5 fraction in the feed is too low and the start-up time required for the accumulation of the absorbent is too long, carbon 5 can be injected once in the depropanizer column as a recycling absorbent.

If the feed has passed the depropanizer and does not contain carbon four and heavier components, the separation process is shown in Figure 4. The reactor outlet gas is compressed, washed with water, washed with alkali, dried and dehydrated, and then passed to a high pressure depyrene column. The gas of the high pressure depropanizer overhead gas is further pressurized to 2.0~4.0Mpa, and then the acetylene hydrogenation reactor is used to remove the alkyne; or the acetylene hydrogenation reactor is set at the top outlet of the deethanizer tower, and the high pressure desulfurization is directly cooled. The gas at the top of the tower is gas-liquid two phases. The gas phase enters the pre-cutting column, and the liquid phase is divided into two, one part is used as the reflux of the high pressure depropanizer column, and a part is used as the feed of the pre-cutting tower. The overhead product of the pre-cutting tower is cooled and sent to an absorption tower, which uses carbon trioxide as an absorbent to absorb the carbon dihydrocarbons in the top product of the pre-cutting tower, and the light gas is discharged from the top; The kettle product is returned to the pre-cutting tower as a feed. The product of the pre-cutting column is sent to a deethanizer for clear cutting of carbon two and carbon three, the top of the column is carbon distillate, and the product of the column is carbon three. The carbon triene is removed from the propyne and sent to the propylene rectification column. The overhead propylene product of the propylene rectification column is sent out of the boundary zone; the column is cooled and sent to the absorption tower as an absorbent. The top of the deethanizer is discharged to an ethylene rectification column, and ethylene and ethane are separated. If a carbon tri-absorbing agent containing propylene as a main component is used, the discharge of the tower of the deacetylation tower is divided into two, and some of the carbon three is pumped and cooled, and then sent to the absorption tower as an absorption unit, and part of the propylene is supplied. Distillation column. If a propane-based carbon tri-absorbent (see Figure 4) is used, the propylene rectification tank is divided into two parts, one part is the propane product sent out of the boundary area, and the rest is pumped and cooled to the absorption. The column acts as an absorbent.

Regardless of the absorbent used in the absorption tower, the exhaust gas from the top of the absorption tower can be passed through an expander and a heat exchanger, and heated under reduced pressure to a pressure and temperature that meets the requirements. Regardless of the absorbent used in the absorber, the vent gas at the top of the absorber can be passed to a cooling condenser as needed to reduce the absorbent content.

Using the above process, the carbon dioxide fraction contained in the pre-cut bottom tank liquid is greater than 99.8% of the feed, and the carbon three fraction is greater than 99.5% of the feed, which has a high material recovery rate.

A second advantage of the invention is the low energy consumption. The separation of formazan, hydrogen and carbon diterpenes in the present invention is accomplished in two steps. In the first step, 30%~95% of carbon dioxide is separated from methane and hydrogen by a pre-cutting tower. In the second step, the carbon dioxide is absorbed by the solvent in the absorption tower to achieve complete separation of carbon two and methane hydrogen. Absorbent for feed tower Cool to a temperature not higher than -50 °C. Since carbon dioxide has been largely removed before entering the absorption column, the amount of solvent required is much less than the solvent absorption and separation method in which all other carbon distillates enter the absorption column, and the regeneration of the solvent passes through the pre-cutting tower. Distillation is achieved. When US 5326929 uses C5 as a solvent, when the ethylene content in the feed is 4763.3 lb mole/hr, a solvent of 5651.8 lb mole/h is required, and the ratio of solvent to carbon two is 1.186. The method regenerates the solvent at a pressure greater than 3.2 mpa. The regeneration temperature is very high, possibly up to 150° (:. Then the solvent is cooled to -50 ° C and then fed to the formazan absorption tower. Such a large amount of solvent is heated and then cooled. The cycle, the energy consumption is obvious. However, the advantage of this method is that it is suitable for the cracking gas composition of the hydrocarbon cracking ethylene plant and there is no cryogenic system.

U.O.P. Company's special IJ: "PROCESS FOR PRODUCING ETHYLENE" WO 01/25174 The pre-deionization tower is used to reduce the feed to the demethylation system, but still contains all the carbon distillate. The top of the pre-cutting tower of the present invention contains carbon in the range of 5% to 70%. The top of the WO 01/25174 demethylation tower contains 15% of the feed ethylene, which needs to be adsorbed and desorbed by the pressure swing adsorption unit. The desorbed gas is returned to the raw material compressor inlet, increasing the load on all subsequent processes. The pre-cutting tower top discharge absorbent of the present invention absorbs the carbon 2 therein, and the absorption liquid is returned to the pre-cutting tower, and the steps of compression, methanol removal, dimethyl ether removal and drying are not performed before the pre-cutting tower. . The same raw material gas composition was used to simulate the present invention and the conventional pre-demethanization cryogenic process, respectively. The power of the feed gas compressor and the refrigeration compressor for the two processes was as follows:

Table 1 Comparison of compressor power between the present invention and conventional sequential processes

Traditional sequential process, KW invention, KW

The first three sections of the raw material gas compressor 6534 6534

Feed gas compressor fourth section 2170 2170

Ethylene compressor section power 90.3 200.3

Ethylene compressor - segment power 67.4

Ethylene compressor ^ 'section power 348.5

506.2 200.3

Propylene compressor section power 1 49 1 704

Iridene compressor - segment power 237 1 .9 2343

Three-stage power of propylene compressor 1925.5 2065

Propylene compressor four-stage power 3407.4 35 13

Total power of propylene compressor 9653.8 9625

Total refrigeration compressor power 10160 9825.3

Refrigeration compressor total power comparison 100 96.7 It can be seen that the energy consumption of the invention is slightly lower than the cryogenic separation process with long process, large investment and complicated operation.

The WO 01/25174 specification has its patented process and compressor power comparison of the traditional front-end decoupling process:

If the power of the feed gas compressor and the refrigeration compressor in the conventional sequential process and the pre-de-acetamation process are equal or substantially equal, it can be inferred that the total power of the compressor of the present invention is slightly lower than the PSA process.

Table 2 Compressor power comparison of the three processes

Considering that the pressure swing adsorption device operates with steps of pressurization, adsorption, purging, repressurization, etc., it requires a lot of power, and the present invention is more energy efficient than the process described in WO 01/25 1 74.

Example 1

The process is shown in Figure 1. The outlet gas of a reactor is subjected to compression, water washing, alkali washing, methanol removal and drying and dehydration to enter the separation process. The gas S 100 is cooled by the feed cooler E101 to about 10 ° C and enters the flash tank V101 for gas-liquid phase separation. The gas and liquid phases are further cooled to 0 ° C and -20 ° C by the pre-cutting tower feed cooler E 102, respectively, and then enter the pre-cutting tower T101. The overhead product S307 of the pre-cutting tower T101 contains all of the light gas and about 24% of the ethylene in the feed. The overhead discharge enters the absorption column 102 after cooling with an ethylene refrigerant at -60 ° C in the oil absorption tower feed cooler E103. The absorption tower T102 absorbs carbon dioxide in the feed by using a carbon trioxide-based absorbent S408. The overhead gas of the absorption tower T102 is further cooled by an ethylene refrigerant at -60 ° C in the oil absorption tower outlet cooler E105 to reduce the propylene content therein, and then discharged as methane hydrogen product S3 13 . If the user needs higher purity hydrogen, S313 can enter the separation facility such as pressure swing adsorption or membrane separation for further processing. Pre-cut tower tower discharge S31 1 is carbon two, carbon three and heavier Products, directly go to the de-ethanation tower T201 for the separation of carbon two and carbon three, the top material removes the acetylene and then goes to the ethylene rectification tower 1, the tower material to the de-propanizer tower T202, the de-propanizer tower top product In addition to the propyne, the propylene rectification column 2 is removed, and the product of the column is separated from the carbon tetrazide 3 and carbon 5 by the deuteration column T203. According to the logistics data listed in the table, after separating the light gas such as methane and hydrogen through the pre-cutting tower and the absorption tower, the ethylene and propylene in the feed only lost 0.57 and 4.386 kgmol/hr, respectively, accounting for 0.0422% and 0.487 of the feed. %. The ethylene contained in the circulating liquid S304 of the absorption tower to the pre-cutting column is less than 24% of the ethylene fed.

Example 1 Calculation Results

The process is shown in Figure 3. The outlet gas of a reactor is subjected to compression, water washing, alkali washing, methanol removal, and drying and dehydration to enter the separation process. The gas S 100 is cooled by the feed cooler E101 to about 10 ° C and enters the flash tank V 101 for gas-liquid phase separation. The gas and liquid phases were further cooled to 0 Ό and - 19 ° C by the pre-cutting tower feed cooler E1 02, respectively, and then entered into the pre-cutting tower T101. The overhead product S308 of the pre-cutting tower T101 contains all of the light gas and about 27% of the ethylene in the feed, and is cooled in the oil absorption tower feed cooler E103 with an ethylene refrigerant at -60 ° C and then enters the absorption tower T102. The absorption tower T102 absorbs carbon two in the feed by using an absorbent (S408) containing carbon five as a main component. The pre-cutting tower T101 tower discharge S31 1 is carbon two, carbon three and heavier products, and directly removes the bismuth tower T201 to carry out the separation of carbon two and carbon three. The top product of the deuterium column T201 is carbon distillate S401 to remove acetylene and ethylene ethane to be separated from the ethylene rectification column 1; the bottom product depyeration column separates carbon tris and carbon four. The top product S501 of the depropanol column 202 is a carbon triterpene, which is further processed to obtain a propylene product; the bottom product is removed from the crucible. The top product of the debutanizer column is carbon four S503, and the product of the column is carbon five. Divide the carbon five fraction into two, and part of it is sent to the carbon five product S505 The boundary zone; a part of the pump is pressurized and cooled and sent to the absorption tower as an absorbent S408.

According to the logistics data listed in the table, after the separation of the light gas such as formazan and hydrogen by the pre-cutting tower and the absorption tower, the ethylene in the feed only lost 0.4839 kgmol/hr, accounting for 0.036% of the feed. The ethylene contained in the circulating liquid S304 from the absorption tower to the pre-cutting column was less than 27% of the ethylene fed. The propylene content in the top of the de-propanizer tower is greater than 99.8% of the feed content, the carbon tetra-content in the top of the debutanizer tower is greater than 98% of the feed content, and the yield of the carbon five product is 99%.

Example 2 Calculation Results

Example 3

The process is shown in Fig. 4. A reactor outlet gas S100 is compressed, washed with water, washed with alkali, dried and dehydrated, and then enters the high pressure deacetylation tower T202A. The high depropanizer tower T202A overhead gas is further pressurized to 3.6 MPa and then passed to the acetylene hydrogenation reactor to remove the alkyne. After the acetylene was removed, the material was cooled to 2 ° C to obtain a gas-liquid two phase, and the gas and liquid phases were further cooled. The gas phase enters the pre-cutting tower T101, and the liquid phase is divided into two, a part is used as a reflux of the high-pressure depropanizer T202A, and a part is fed as a pre-cutting tower T101. The overhead product of the pre-cutting tower T101 is sent to the absorption tower T102 after being cooled, and the tower uses carbon three as an absorbent to absorb the carbon dihydrocarbons in the top product of the pre-cutting tower, and the gas at the top of the absorption tower T102 is absorbed. Further, it was cooled in an oil absorption tower outlet cooler E305 with an ethylene refrigerant of -60 ° C to lower the absorbent content therein, and then discharged as a formazan hydrogen product S313. The absorption tower T102 tower product S304 is returned to the pre-cutting tower T101 as a feed. The tower product S311 of the pre-cutting tower T101 is sent to the decoupling column T201 for clear cutting of carbon two and carbon three, the carbon dioxide fraction S401 is obtained at the top of the column, and sent to the ethylene rectification tower D402 for separation into ethylene and ethane; The product is carbon tris, and the carbon triene is removed from the propyne and sent to the propylene rectification column D405. The overhead propylene product of the propylene rectification column is sent out of the boundary zone; the column reactor is cooled to -56 ° C and sent to the absorption column as an absorbent S408.

Example 3 Calculation Results

Claims

Rights request

What is claimed is: 1. A method of separating a non-cryogenic low-carbon hydrocarbon containing a light gas, the method comprising the steps of:

(1) The pretreated reactor outlet gas is cooled to 10 ° C ~ - 37 ° C and sent to a pre-cutting tower, the top product including methane, hydrogen and other light gases, part of the carbon distillate and phase equilibrium a small amount of carbon three, the tower product is the remaining carbon two and heavier components;

(3) The tower product of the pre-cutting tower is sent to the decoupling tower for clear cutting of carbon two and carbon three, and the carbon dioxide fraction is obtained at the top of the tower; the product of the tower is carbon three and heavier components, if entering the pre-cutting tower The feed contains acetylene, and the overhead product first removes the acetylene and then enters the ethylene fine column to be purified to the desired mass concentration. '

2. The method for separating a non-cryogenic low-carbon hydrocarbon containing light gas according to claim 1, wherein the pretreatment in the step (1) is to pressurize the reactor outlet gas to 2.0~ 4.0MPa, remove acid gas and moisture.

The method for separating non-cryogenic low-carbon hydrocarbons containing light gas according to claim 1, wherein the pretreatment in the step (1) is to remove the reactor outlet gas by compression cooling. After the acid gas and drying, it enters the high pressure depropanizer tower, and the gas at the top of the high pressure depropanizer is further pressurized to 2.0 to 4.0 MPa, and then enters the acetylene hydrogenation reactor to remove the alkyne or go to the pre-cutting tower.

The method for separating non-cryogenic low-carbon hydrocarbons containing light gas according to claim 1, wherein the pre-cutting tower in the step (1) is a non-clear cut distillation of the carbon distillate. The tower top carbon distillate may comprise from 5% to 70% of the feed carbon two; the other light gases include nitrogen and oxygen.

The method for separating non-cryogenic low-carbon hydrocarbons containing light gas according to claim 1, wherein the cooling in the step (2) is performed by using propylene refrigerant or a temperature of -50 ° C. - 66 ° C ethylene refrigerant.

The method for separating a non-cryogenic low-carbon hydrocarbon containing light gas according to claim 1, wherein the absorption tower in the step (2) adopts an absorbent containing carbon trioxide as a main component. Distillate the de-ethanator column discharge into two, a part of which is used as a feed for the depropanizer to separate the carbon three and carbon four; Part of which is cooled to below -50 °C and sent to the absorption tower as an absorbent. The amount of the absorbent is 5% to 90% of the discharge amount of the deacetylation column, and the top discharge of the depropanizer is carbon three. , including all carbon three components entering the cutting tower, if the carbon three components contain alkyne, the alkyne should be removed first and then separated into pure components such as propylene and propane by distillation. The carbon four and heavier components are sent to the butyl sulphide to separate the carbon four from the carbon five.

The method for separating a non-cryogenic low-carbon hydrocarbon containing light gas according to claim 1, wherein the absorption tower in the step (2) adopts an absorbent containing carbon tetrachloride as a main component. The dipyridamole tray discharge is divided into two parts, one part is used as the feed of the debutanizer tower to carry out the separation of carbon four and carbon five; the other part is cooled to not higher than -5 CTC and sent to the absorption tower as an absorbent. The amount of the absorbent is 20% to 95% of the discharge amount of the carbon kettle.

The method for separating a non-cryogenic low-carbon hydrocarbon containing light gas according to claim 1, wherein the absorption tower in the step (2) adopts an absorbent containing carbon five as a main component. The distillate Tata can be divided into two parts, one part is sent out as a carbon five finished product, and the other part is cooled to not more than -50 ° C and sent to the absorption tower as an absorbent. The amount of the absorbent can be It is 30%~98 of the output of the tower.

0/

0 o

9. The method for separating a non-cryogenic low-carbon hydrocarbon containing light gas according to claim 1, wherein the absorption gas at the top of the absorption tower contains a small amount of absorbent, and the content of the absorbent exceeds the requirement. The absorption column outlet gas is passed to a cooling condenser to reduce the absorbent content, or the condensate cooler off-gas is passed to a separation facility for further separation, including a pressure swing or membrane separation.