Separation method and device after concentrated gas based on dry gas raw material change

Abstract

The invention belongs to the technical field of dry gas concentration and gas separation, and discloses a method and a device for separating concentrated gas based on dry gas raw material change. An expansion machine is additionally arranged at the top of an absorption tower, an ethylene crude separation tower is additionally arranged after concentrated gas is extracted, and the cold energy of methane hydrogen at the top of the absorption tower after expansion is provided for the crude separation tower, so that crude ethane at the bottom of the crude separation tower meets the feeding condition of an ethane furnace under the condition of not consuming the cold energy of public engineering, and crude ethylene at the top of the tower does not contain C3 heavy components; and separation is carried out by a demethanizing tower and an ethylene refining tower instead of a depropanizing tower. A dry gas raw material of the dry gas concentration device is changed into catalytic dry gas from hydrocarbonylation tail gas generated by the catalytic dry gas through a device for preparing ethylbenzene from the dry gas by a gas phase method. Compared with the original process, the total energy consumption can be reduced by 21.2%; through a method of separating after concentrating gas, a liquid phase method is used for preparing ethylbenzene instead of a gas phase method for preparing ethylbenzene from dry gas, and 1.2 t / h high-grade ethylbenzene can be produced more; the energy consumption is obviously reduced, and the product quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of dry gas concentration and gas separation, and in particular to a method and device for separation of concentrated gas based on dry gas raw material change. Background Art

[0002] Refinery dry gas mainly comes from the primary and secondary processing of crude oil, such as atmospheric and vacuum distillation, catalytic cracking, delayed coking, catalytic reforming and alkane dehydrogenation. The main components are methane, ethane, ethylene, propylene, propane, butane, etc., among which C2 has the highest content. At present, the methods for recovering C2 from refinery dry gas mainly include deep cold separation, cold oil absorption, pressure swing adsorption (PSA), etc. Each method has its own advantages and disadvantages. Among them, the cold oil absorption method belongs to physical absorption, which uses the solubility difference of each component in the dry gas in the absorbent to achieve dry gas separation. The absorbent is generally mixed C4, mixed C5 and liquefied gas. First, the C2 and C3 components are selectively absorbed through the absorption process, and then the C2 and C3 components are recovered through the desorption method. The cold oil absorption method includes medium cold oil absorption method (-40~-20℃) and shallow cold oil absorption method (10℃~15℃). The medium cold oil absorption method has lower energy consumption.

[0003] As the tail gas of the catalytic unit, the catalytic dry gas of the refinery is usually directly burned as fuel gas, and the utilization rate is low. The ethylene content in the catalytic dry gas is generally high (10% to 30%). Burning it as fuel gas will cause serious waste of ethylene resources. Using the ethylene in the catalytic dry gas to produce ethylbenzene can improve the utilization rate of the catalytic dry gas and effectively reduce the production cost of the ethylbenzene unit. The gas phase process has a high reaction temperature, many side reactions, and many impurity components such as xylene and propylbenzene in the product. The quality of the ethylbenzene product is relatively poor and the energy consumption is high. The liquid phase process has mild reaction conditions, and the ethylbenzene product produced is of better quality and lower energy consumption than the gas phase process, and has a good development advantage.

[0004] At present, considering the factory's demand for low energy consumption in the production process and high-grade ethylbenzene products, it is necessary to adjust the catalytic dry gas process direction, reduce the load of the gas-phase dry gas ethylbenzene production unit, and allow more catalytic dry gas to enter the dry gas concentration unit. The ethylene content in the concentrated dry gas is too high and cannot be directly entered into the ethane furnace. In addition, the methane hydrogen at the top of the absorption tower in the dry gas concentration unit has the characteristics of high pressure and low temperature. The current device treatment measures are to add a throttle valve to the methane hydrogen pipeline to reduce pressure and set a steam heat exchanger to heat it before entering the fuel pipeline network. This process not only consumes steam energy significantly, but also fails to utilize the pressure energy and the contained cold capacity, resulting in energy waste. Summary of the invention

[0005] The present invention relates to a method and device for separating concentrated gas based on dry gas raw material change. The key point is to stop the operation of a high-energy-consuming gas-phase dry gas to ethylbenzene device. At this time, the raw material of the dry gas concentration device is changed from catalytic dry gas to ethylbenzene hydrocarbon tail gas obtained by gas-phase dry gas to catalytic dry gas. By adjusting the circulation amount of the absorbent and the process parameters of each device, the process indicators of the product before and after the dry gas raw material change are consistent. Considering that the ethylene content in the concentrated gas of the dry gas concentration device is relatively high at this time and cannot enter the ethane furnace, an ethylene coarse separation tower is added to roughly separate the concentrated gas. The cooling capacity required by the feed precooler and the top condenser of the coarse separation tower is provided by the high-pressure and low-temperature methane hydrogen at the top of the absorption tower through the newly added expander.

[0006] In this way, by adding a new ethylene crude separation tower and an expander, the cooling capacity of methane hydrogen at the top of the absorption tower is recycled and utilized without consuming much cooling capacity of the utility project, thereby improving energy utilization. After the concentrated gas enters the ethylene crude separation tower, the ethylene content in the crude ethane at the bottom of the tower meets the feeding conditions of the ethane furnace. At the same time, the crude ethylene at the top of the tower does not contain heavy components such as carbon three, so it does not need to pass through the depropanizer, but only needs to pass through the demethanizer and ethylene refining tower. Ethylene is used in the liquid phase ethylbenzene production unit to obtain high-grade ethylbenzene products, which significantly reduces energy consumption and realizes the full utilization of carbon two resources.

[0007] The technical solution of the present invention is: a method for separating concentrated gas based on the change of dry gas raw material, the steps are as follows:

[0008] The gas phase of the first flash gas 7 from the first flash tank B is combined with the raw dry gas 1 through the circulating dry gas compressor D to enter the absorption tower A as a mixed dry gas; the lean solvent 2 from the bottom of the solvent regeneration tower K and the semi-lean solvent 3 from the liquid phase of the second flash tank C enter the absorption tower A from the top and the middle of the absorption tower A respectively; the lean solvent 2 and the semi-lean solvent 3 are countercurrently contacted with the mixed dry gas to absorb the carbon two components in the mixed dry gas; the top of the absorption tower A is the methane hydrogen mixed gas 4, which is expanded by the newly added expander J and then heat-exchanged with the gas phase at the top of the ethylene crude fraction tower G through the crude fraction tower top gas-expanded gas heat exchanger H; the rich absorption liquid 5 in the bottom of the absorption tower A enters the first flash tank B;

[0009] The liquid phase of the first flash bottom liquid 8 of the first flash tank B enters the second flash tank C; the gas phase of the second flash gas 9 of the second flash tank C is cooled by the coarse fraction tower feed-coarse fraction tower top gas heat exchanger F, and then enters the middle and upper position of the ethylene coarse fraction tower G as the flash tank concentrated gas 12; part of the liquid phase of the second flash bottom liquid 10 of the second flash tank C is used as the semi-lean solvent 3, and the remaining part is used as the solvent regeneration tower feed 11 to enter the solvent regeneration tower K;

[0010] The top of the ethylene crude fraction tower G is passed through the crude fraction tower top gas-expanded gas heat exchanger H and the crude fraction tower reflux tank I to obtain crude ethylene 13, and part of the crude ethylene is refluxed to the ethylene crude fraction tower G; the crude ethylene 13 enters the crude fraction tower feed-crude fraction tower top gas heat exchanger F for heat exchange to obtain heat-exchanged crude ethylene 17, which successively enters the crude ethylene compressor O for pressurization and the demethanizer feed cooler P for cooling, and then enters the middle part of the demethanizer Q as the demethanizer feed 19; the top of the demethanizer Q is passed through the demethanizer condenser R and the demethanizer reflux tank S to obtain methane 20, and part of the methane The ethane is refluxed to the demethanizer Q; the bottom of the demethanizer Q is mixed carbon dioxide 21; part of the mixed carbon dioxide 21 is refluxed to the bottom of the demethanizer Q through the demethanizer reboiler T; the mixed carbon dioxide 21 enters the ethylene refining tower U, the top of the ethylene refining tower U is passed through the ethylene refining tower condenser V and the ethylene refining tower reflux tank W to obtain a high-purity ethylene product 22, and enters the liquid phase ethylbenzene preparation device Y to obtain an ethylbenzene product 24; part of the ethane 23 at the bottom of the ethylene refining tower U is refluxed to the bottom of the ethylene refining tower U through the ethylene refining tower reboiler X, and the rest enters the ethane furnace Z for cracking;

[0011] Crude ethane 14 is obtained at the bottom of the ethylene crude fraction tower G;

[0012] The top gas of the solvent regeneration tower K passes through the solvent recovery tower top condenser L and the solvent recovery tower reflux tank M as the solvent regeneration tower top concentrated gas 15, and part of the concentrated gas is refluxed to the solvent regeneration tower K; the solvent regeneration tower top concentrated gas 15 is combined with the crude ethane 14 at the bottom of the ethylene crude fraction tower G as the ethane furnace feed 16 and enters the ethane furnace Z; the ethane furnace Z is cracked to obtain the ethane furnace output 25.

[0013] When the utility refrigerant is replenished to the top of the ethylene crude fraction tower G, the crude ethylene compressor O, the demethanizer feed cooler P, the demethanizer Q, and the ethylene refining tower U are shut down;

[0014] The gas phase of the first flash gas 7 from the first flash tank B is combined with the raw dry gas 1 through the circulating dry gas compressor D to enter the absorption tower A as a mixed dry gas; the lean solvent 2 from the bottom of the solvent regeneration tower K and the semi-lean solvent 3 from the liquid phase of the second flash tank C enter the absorption tower A from the top and the middle of the absorption tower A respectively; the lean solvent 2 and the semi-lean solvent 3 are countercurrently contacted with the mixed dry gas to absorb the carbon two components in the mixed dry gas; the top of the absorption tower A is the methane hydrogen mixed gas 4, which is expanded by the newly added expander J and then heat-exchanged with the gas phase at the top of the ethylene crude fraction tower G through the crude fraction tower top gas-expanded gas heat exchanger H; the rich absorption liquid 5 in the bottom of the absorption tower A enters the first flash tank B;

[0015] The liquid-phase primary flash bottom liquid 8 of the primary flash tank B enters the secondary flash tank C; the gas-phase secondary flash gas 9 of the secondary flash tank C is cooled by the crude fraction tower feed-crude fraction tower top gas heat exchanger F, and then enters the middle and upper position of the ethylene crude fraction tower G as the flash tank concentrated gas 12; part of the liquid-phase secondary flash bottom liquid 10 of the secondary flash tank C is used as the semi-lean solvent 3, and the remaining part enters the solvent regeneration tower K as the solvent regeneration tower feed 11; the top gas of the solvent regeneration tower K is passed through the solvent recovery tower top condenser L and the solvent recovery tower reflux tank M as the solvent regeneration tower top concentrated gas 15, and part of the concentrated gas is refluxed to the solvent regeneration tower K; the solvent regeneration tower top concentrated gas 15 is combined with the crude ethane 14 at the bottom of the ethylene crude fraction tower G as the ethane furnace feed 16 and enters the ethane furnace Z;

[0016] The top of the ethylene crude fraction tower G is passed through the crude fraction tower top gas-expanded gas heat exchanger H and the crude fraction tower reflux tank I to obtain product-grade ethylene, and part of the product-grade ethylene is refluxed to the ethylene crude fraction tower G. The product-grade ethylene enters the crude fraction tower feed-crude fraction tower top gas heat exchanger F for heat exchange to obtain product-grade ethylene after heat exchange, and the product-grade ethylene after heat exchange enters the liquid phase ethylbenzene production device Y, and part of it is produced as an ethylene product, and the destination of the product-grade ethylene 17 is flexibly adjusted according to demand; the ethane 14 at the bottom of the ethylene crude fraction tower G enters the ethane furnace Z for cracking.

[0017] A concentrated gas separation device based on dry gas raw material change is used to realize the concentrated gas separation method based on dry gas raw material change; the concentrated gas separation device based on dry gas raw material change comprises an absorption tower A, a primary flash tank B, a secondary flash tank C, a circulating dry gas compressor D, an ethylene crude fraction tower reboiler E, a crude fraction tower feed-coarse fraction tower top gas heat exchanger F, an ethylene crude fraction tower G, a crude fraction tower top gas-expanded gas heat exchanger H, a crude fraction tower reflux tank I, Newly added expander J, solvent recovery tower K, solvent recovery tower top condenser L, solvent recovery tower reflux tank M, solvent recovery tower reboiler N, crude ethylene compressor O, demethanizer feed cooler P, demethanizer Q, demethanizer condenser R, demethanizer reflux tank S, demethanizer reboiler T, ethylene refining tower U, ethylene refining tower condenser V, ethylene refining tower reflux tank W, ethylene refining tower reboiler X, liquid phase ethylbenzene production unit Y, ethane furnace unit Z;

[0018] The raw dry gas is passed through the bottom of absorption tower A; the top of absorption tower A is connected in sequence to the newly added expander J and the top gas-expanded gas heat exchanger H of the crude fractionation tower; absorption tower A is connected to the primary flash tank B; the top of the primary flash tank B is connected in sequence to the circulating dry gas compressor D and the bottom of absorption tower A; the bottom of the primary flash tank B is connected to the secondary flash tank C; the bottom of the secondary flash tank C is divided into two branches, one of which is connected to the middle of absorption tower A, and the other is connected to the solvent recovery tower K; the top of the solvent recovery tower K is connected in sequence to the solvent recovery tower top condenser L and the solvent recovery tower reflux tank M, the solvent recovery tower reflux tank M is divided into two branches, one of which is connected back to the solvent recovery tower K, and the other is connected to the ethane furnace device Z; the bottom of the solvent recovery tower K is divided into two branches, one of which is connected to the solvent recovery tower reboiler N and back to the solvent recovery tower K, and the other is connected to the top of the absorption tower A;

[0019] The top of the secondary flash tank C is connected to the feed of the crude fraction tower-the top gas heat exchanger F of the crude fraction tower; the feed of the crude fraction tower-the top gas heat exchanger F of the crude fraction tower is respectively connected to the ethylene crude fraction tower G and the crude ethylene compressor O; the top of the ethylene crude fraction tower G is connected to the top gas-expansion gas heat exchanger H of the crude fraction tower; the crude fraction tower top gas-expansion gas heat exchanger H produces a product and is connected to the reflux tank I of the crude fraction tower; the reflux tank I of the crude fraction tower is divided into two branches, one of which is connected back to the top of the ethylene crude fraction tower G, and the other circuit is connected to the feed of the crude fraction tower-the top gas heat exchanger F of the crude fraction tower; the bottom of the ethylene crude fraction tower G is divided into two branches, one of which is connected to the reboiler E of the ethylene crude fraction tower and connected back to the ethylene crude fraction tower G, and the other branch is connected to the ethane furnace device Z;

[0020] The crude ethylene compressor O is connected to the demethanizer feed cooler P and the demethanizer Q in sequence; the top of the demethanizer Q is connected to the demethanizer condenser R and the demethanizer reflux tank S in sequence; the demethanizer reflux tank S is divided into two branches, one of which is connected back to the demethanizer Q, and the other is produced; the bottom of the demethanizer reflux tank S is divided into two branches, one of which is connected to the demethanizer reboiler T and is connected back, and the other is connected to the ethylene refining tower U; the top of the ethylene refining tower U is connected to the ethylene refining tower condenser V and the ethylene refining tower reflux tank W in sequence; the ethylene refining tower reflux tank W is divided into two branches, one of which is connected back to the ethylene refining tower U, and the other is connected to the liquid phase ethylbenzene production device Y; the bottom of the ethylene refining tower U is divided into two branches, one of which is connected to the ethylene refining tower reboiler X and is connected back to the ethylene refining tower U, and the other is connected to the ethane furnace device Z.

[0021] When there is utility refrigerant at the top of ethylene crude fractionation tower G, shut down crude ethylene compressor O, demethanizer feed cooler P, demethanizer Q, and ethylene refining tower U; raw dry gas goes to the bottom of absorption tower A; the top of absorption tower A is connected in sequence to the newly added expander J and the first inlet of crude fractionation tower top gas-expansion gas heat exchanger H; the bottom of absorption tower A is connected to the primary flash tank B; the top of the primary flash tank B is connected in sequence to the circulating dry gas compressor D and the bottom of absorption tower A; the bottom of the primary flash tank B is connected to the secondary flash tank C; the secondary flash tank The bottom of tank C is divided into two branches, one of which is connected to the middle of absorption tower A, and the other is connected to solvent recovery tower K; the top of solvent recovery tower K is connected to solvent recovery tower top condenser L and solvent recovery tower reflux tank M in sequence, and solvent recovery tower reflux tank M is divided into two branches, one of which is connected back to solvent recovery tower K, and the other is connected to the middle and lower part of ethylene crude fraction tower G; the bottom of solvent recovery tower K is divided into two branches, one of which is connected to solvent recovery tower reboiler N and back to solvent recovery tower K, and the other is connected to the top of absorption tower A;

[0022] The top of the secondary flash tank C is connected to the feed of the crude fraction tower-the overhead gas heat exchanger F of the crude fraction tower; the feed of the crude fraction tower-the overhead gas heat exchanger F of the crude fraction tower is respectively connected to the middle part of the ethylene crude fraction tower G and the liquid phase ethylbenzene production device Y; the top of the ethylene crude fraction tower G is connected to the second inlet of the overhead gas-expansion gas heat exchanger H of the crude fraction tower; the first outlet of the overhead gas-expansion gas heat exchanger H of the crude fraction tower produces the product, and the second outlet is connected to the reflux tank I of the crude fraction tower; the reflux tank I of the crude fraction tower is divided into two branches, one of which is connected back to the top of the ethylene crude fraction tower G, and the other circuit is connected to the feed of the crude fraction tower-the overhead gas heat exchanger F of the crude fraction tower; the bottom of the ethylene crude fraction tower G is divided into two branches, one of which is connected to the reboiler E of the ethylene crude fraction tower and connected back to the ethylene crude fraction tower G, and the other branch is connected to the ethane furnace device Z.

[0023] The invention has the beneficial effects that the newly added ethylene crude fractionation tower and expander not only do not consume much cooling capacity of the public works, but also recycle and utilize the cooling capacity of the methane hydrogen at the top of the absorption tower, thereby improving the energy utilization rate. After the concentrated gas enters the ethylene crude fractionation tower, the ethylene content in the crude ethane at the bottom of the tower meets the feeding conditions of the ethane furnace, and at the same time, the crude ethylene at the top of the tower does not contain heavy components such as carbon three, and does not need to pass through the depropanizer, but only needs to pass through the demethanizer and the ethylene refining tower. The ethylene is used in the liquid phase ethylbenzene production device to obtain high-grade ethylbenzene products, which significantly reduces energy consumption and realizes efficient utilization of carbon two resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of a method for separating concentrated gas based on dry gas raw material change.

[0025] Figure 2 The present invention is a flow chart of the method when utility refrigerant is added to the top of the ethylene crude fractionation tower.

[0026] Logistics in the figure: 1 raw material dry gas; 2 lean solvent; 3 semi-lean solvent; 4 methane hydrogen mixed gas; 5 rich absorbent; 6 newly added expander outlet gas; 7 primary flash gas; 8 primary flash bottom liquid; 9 secondary flash gas; 10 secondary flash bottom liquid; 11 solvent regeneration tower feed; 12 flash tank concentrated gas; 13 crude ethylene; 14 crude ethane at the bottom of the tower; 15 solvent regeneration tower top concentrated gas; 16 ethane furnace feed; 17 crude ethylene after heat exchange; 18 compressor outlet crude ethylene; 19 demethanizer feed; 20 methane; 21 mixed carbon dioxide; 22 ethylene product; 23 ethane; 24 ethylbenzene product; 25 ethane furnace discharge.

[0027] Equipment in the figure: A absorption tower; B primary flash tank; C secondary flash tank; D circulating dry gas compressor; E ethylene crude fraction tower reboiler; F crude fraction tower feed-crude fraction tower top gas heat exchanger; G ethylene crude fraction tower; H crude fraction tower top gas-expansion gas heat exchanger; I crude fraction tower reflux tank; J newly added expander; K solvent recovery tower; L solvent recovery tower top condenser; M solvent recovery tower reflux tank; N solvent recovery tower reboiler; O crude ethylene compressor; P demethanizer feed cooler; Q demethanizer; R demethanizer condenser; S demethanizer reflux tank; T demethanizer reboiler; U ethylene refining tower; V ethylene refining tower condenser; W ethylene refining tower reflux tank; X ethylene refining tower reboiler; Y liquid phase ethylbenzene production unit; Z ethane furnace unit. DETAILED DESCRIPTION

[0028] The following is a detailed and complete description of the technical solution of the present invention, based on the case where a gas-phase dry gas to ethylbenzene production unit using catalytic dry gas as raw material was shut down and the raw material of the dry gas concentration unit was changed from ethylbenzene alkylation tail gas to catalytic dry gas. Figure 1 Taking the example, the separation process of concentrated gas after dry gas raw material change of the present invention is described in detail.

[0029] The desulfurized catalytic dry gas is combined with dry gas from other devices to form raw dry gas 1 and enter the process of the present invention. The raw dry gas 1 is combined with the gas phase 7 of flash tank B as mixed dry gas and enters the absorption tower A. The lean solvent 2 from the bottom of the solvent regeneration tower K and the semi-lean solvent 3 from the liquid phase of the secondary flash tank C enter from the top and middle of the absorption tower A respectively, and countercurrently contact with the mixed dry gas to absorb the carbon two components in the dry gas. The top of the absorption tower A is a methane-hydrogen mixed gas 4, which is expanded by the newly added expander J and heat-exchanged with the gas phase at the top of the ethylene crude fraction tower G through the crude fraction tower top gas-expanded gas heat exchanger H. The rich absorption liquid 5 in the bottom of the absorption tower A enters the primary flash tank B.

[0030] The gas phase 7 of the first-stage flash tank B is pressurized by the compressor D and merged with the raw gas 1 as a mixed dry gas to return to the absorption tower A. The liquid phase 8 of the first-stage flash tank B enters the second-stage flash tank C. The gas phase 9 of the second-stage flash tank C is cooled by the coarse fraction tower feed-coarse fraction tower top gas heat exchanger F and then enters the coarse fraction tower G as the flash tank concentrated gas 12. The liquid phase of the second-stage flash tank C returns to the absorption tower A as a semi-lean solvent 3, and the rest enters the solvent regeneration tower K.

[0031] The concentrated gas 12 from the flash tank enters the ethylene crude fraction tower G at the upper position of the tower, and crude ethylene 13 and crude ethane 14 are obtained at the top and bottom of the tower, respectively. The lean solvent 2 produced in the bottom of the solvent regeneration tower K enters the top of the absorption tower A, and the gas phase at the top of the tower is used as the concentrated gas 15 and merges with the crude ethane 14 at the bottom of the ethylene crude fraction tower G 16 and enters the ethane furnace Z.

[0032] Optionally, when there is a refrigerant supplement from the utility, the concentrated gas 16 at the top of the solvent regeneration tower can be pre-cooled and then introduced into the middle and lower position of the ethylene crude fraction tower G. When the cooling capacity is sufficient, product-grade ethylene can be directly obtained at the top of the ethylene crude fraction tower G, and it is not necessary to introduce the crude ethylene 13 at the top of the crude fraction tower G into the demethanizer Q and the ethylene refining tower U for further separation.

[0033] The crude ethylene 13 at the top of the ethylene crude fraction tower G is pressurized by the crude ethylene compressor O and then cooled by the demethanizer feed cooler P and enters the middle part of the demethanizer Q. Methane 20 is obtained at the top of the demethanizer Q, and mixed carbon dioxide 21 is obtained at the bottom of the tower. The mixed carbon dioxide 21 at the bottom of the demethanizer Q enters the ethylene refining tower U. The high-purity ethylene product 22 obtained at the top of the ethylene refining tower U enters the liquid phase ethylbenzene production device Y, and the ethylbenzene product 24 is obtained. The ethane 23 at the bottom of the tower enters the ethane furnace Z for cracking, and the cracking product 25 is obtained.

[0034] Optionally, part of the high-purity ethylene product 22 obtained at the top of the ethylene refining tower U can enter the liquid-phase ethylbenzene production unit Y, and part can be produced as an ethylene product. The destination of the ethylene product 22 can be flexibly adjusted according to demand.

[0035] Example:

[0036] In view of a petrochemical company's dry gas volume of 9377 kg / h, in which the desulfurized catalytic dry gas with an ethylene content of 18.94% (volume fraction) is used in a gas-phase dry gas to ethylbenzene unit. Due to the high energy consumption of the gas-phase method and poor product quality, it is proposed to stop the operation of the gas-phase dry gas to ethylbenzene unit, merge the catalytic dry gas into the dry gas concentration unit, and separate the concentrated gas after the raw material of the dry gas concentration unit is changed, which improves the energy utilization rate, significantly reduces energy consumption, and realizes the efficient utilization of carbon two resources. The details are as follows:

[0037] The composition of the catalytic dry gas is shown in Table 1:

[0038] Table 1 Catalytic dry gas composition

[0039] Components Volume fraction / % Mass fraction / % <![CDATA[H2]]> 18.48 1.87 <![CDATA[CO2]]> 0.87 1.93 <![CDATA[O2]]> 0.33 0.53 <![CDATA[N2]]> 18.41 25.99 <![CDATA[CH4]]> 32.19 26.02 <![CDATA[C2H6]]> 8.74 13.25 <![CDATA[C2H4]]> 18.94 26.77 <![CDATA[C3H8]]> 0.08 0.18 <![CDATA[C3H6]]> 1.08 2.29 C4 and C4+ 0.16 0.48 H2O 0.67 0.6

[0040] The present invention proposes a method for separating concentrated gas based on the change of dry gas raw material, and the specific process is as follows:

[0041] The catalytic dry gas after desulfurization is combined with the dry gas from other devices to form a dry gas raw material 1 to enter the process of the present invention. The dry gas raw material 1 has a mass flow rate of 30367kg / h, and is combined with the flash tank B gas phase 7 to form a mixed dry gas. The mixed dry gas has a mass flow rate of 34172kg / h and a temperature of -35°C. It enters the absorption tower A, the feed position is 30, the theoretical plate number is 30 for calculation, and the tower top pressure is controlled at 3.6MPag. The lean solvent 2 from the bottom of the self-solvent regeneration tower K and the semi-lean solvent 3 from the liquid phase of the secondary flash tank C enter from the top and middle of the absorption tower A respectively, and countercurrently contact with the mixed dry gas to absorb the carbon two components in the dry gas. The top of the absorption tower A is a methane hydrogen mixed gas 4 with a temperature of -32°C. After the newly added expander J, the temperature is -69.5°C. It is heat exchanged with the top gas phase of the ethylene crude fraction tower G through the crude fraction tower top gas-expanded gas heat exchanger H. The rich absorption liquid 5 in the bottom of the absorption tower A enters the primary flash tank B with a mass flow rate of 76217kg / h.

[0042] The gas phase 7 of the first-stage flash tank B has a pressure of 0.5 MPag and is pressurized to 3.64 MPag by compressor D, and then merged with the raw gas 1 as a mixed dry gas and returned to the absorption tower A. The liquid phase 8 of the first-stage flash tank B enters the second-stage flash tank C. The gas phase 9 of the second-stage flash tank C has a temperature of -64°C. After being cooled by the coarse fraction tower feed-coarse fraction tower top gas heat exchanger F, it enters the coarse fraction tower G as the flash tank concentrated gas 12 with a mass flow rate of 6066 kg / h and a temperature of -18°C. The liquid phase of the second-stage flash tank C returns to the absorption tower A as a semi-lean solvent 3, and the rest enters the solvent regeneration tower K.

[0043] The concentrated gas 12 from the flash tank enters the ethylene crude fraction tower G, with a feed position of 20, a theoretical plate number of 40, and a controllable top pressure of 1.62 MPag. The mass flow rates of crude ethylene 13 and crude ethane 14 are 4200 kg / h and 1866 kg / h, respectively, at the top and bottom of the tower. The lean solvent 2 produced in the bottom of the solvent regeneration tower K enters the top of the absorption tower A, and the gas phase at the top of the tower is used as the concentrated gas 15 to merge with the crude ethane 14 at the bottom of the ethylene crude fraction tower G, and enters the ethane furnace Z with a mass flow rate of 8834 kg / h.

[0044] The crude ethylene 13 at the top of the ethylene crude fractionation tower G is pressurized to 3.2 MPag by the crude ethylene compressor O and is cooled to -35°C by the demethanizer feed cooler P and enters the demethanizer Q, the feed position is 25, the theoretical plate number is 50 for calculation, and the top pressure is controlled to be 3.0 MPag. Methane 20 with a mass flow rate of 339 kg / h is obtained at the top of the tower, and the mixed carbon dioxide 21 is obtained at the bottom of the demethanizer Q. The mixed carbon dioxide 21 at the bottom of the demethanizer Q enters the ethylene refining tower U, the feed position is 40, the theoretical plate number is 60 for calculation, and the top pressure is controlled to be 1.62 MPag. The high-purity ethylene product 22 is obtained at the top of the ethylene refining tower U and enters the liquid phase ethylbenzene production unit Y. The ethylbenzene product 24 has a mass flow rate of 8700 kg / h. The ethane 23 at the bottom of the tower enters the ethane furnace Z for cracking, and the cracking product 25 is obtained.

[0045] Compared with the original process in which the catalytic dry gas first passes through the gas phase dry gas to ethylbenzene device to obtain ethylbenzene hydrocarbon tail gas and then enters the dry gas concentration device, the process of the present invention shuts down the gas phase dry gas to ethylbenzene device, and the catalytic dry gas directly enters the dry gas concentration device. Compared with the method of separating the concentrated gas and then preparing ethylbenzene by liquid phase, the total energy consumption and product indicators are shown in Table 2

[0046] Table 2 Comparison of total energy consumption and product indicators

[0047]

[0048] Compared with the original process, the total energy consumption of the process of the present invention is reduced by 21.2%, the xylene content in ethylbenzene is lower, it is a high-grade ethylbenzene product, and can produce 1.2t / h more ethylbenzene; it significantly reduces energy consumption, improves product quality, and realizes efficient utilization of carbon dioxide resources.

[0049] The present example is merely illustrative and not a complete set of embodiments. All other embodiments improved or adjusted by ordinary technicians in this field are within the protection scope of the present invention.

Claims

1. A method for separation of concentrated gas based on dry gas raw material change, characterized in that: Here are the steps: The gas phase of the first flash gas (7) from the first flash tank (B) is combined with the raw material dry gas (1) through the circulating dry gas compressor (D) to form a mixed dry gas and enter the absorption tower (A); the lean solvent (2) from the bottom of the solvent regeneration tower (K) and the semi-lean solvent (3) from the liquid phase of the second flash tank (C) enter the absorption tower (A) from the top and the middle of the absorption tower (A) respectively; the lean solvent (2) and the semi-lean solvent (3) are countercurrently contacted with the mixed dry gas to absorb the carbon two components in the mixed dry gas; the top of the absorption tower (A) is the methane hydrogen mixed gas (4), which is expanded by the newly added expander (J) and then heat-exchanged with the gas phase at the top of the ethylene crude fraction tower (G) through the crude fraction tower top gas-expanded gas heat exchanger (H); The rich absorption liquid (5) in the bottom of the absorption tower (A) enters the primary flash tank (B); The liquid phase of the first flash bottom liquid (8) of the first flash tank (B) enters the second flash tank (C); the gas phase of the second flash gas (9) of the second flash tank (C) is cooled by the crude fraction tower feed-crude fraction tower top gas heat exchanger (F), and then enters the middle and upper position of the ethylene crude fraction tower (G) as the flash tank concentrated gas (12); part of the liquid phase of the second flash bottom liquid (10) of the second flash tank (C) is used as the semi-lean solvent (3), and the remaining part is used as the solvent regeneration tower feed (11) to enter the solvent regeneration tower (K); The top of the ethylene crude fraction tower (G) is passed through a crude fraction tower top gas-expanded gas heat exchanger (H) and a crude fraction tower reflux tank (I) to obtain crude ethylene (13), and part of the crude ethylene is refluxed to the ethylene crude fraction tower (G); the crude ethylene (13) enters a crude fraction tower feed-crude fraction tower top gas heat exchanger (F) for heat exchange to obtain heat-exchanged crude ethylene (17), which is successively entered into a crude ethylene compressor (O) for pressurization and a demethanizer feed cooler (P) for cooling, and then enters the middle of a demethanizer (Q) as a demethanizer feed (19); the top of the demethanizer (Q) is passed through a demethanizer condenser (R) and a demethanizer reflux tank (S) to obtain methane (20), and part of the methane is refluxed to the demethanizer (Q); the bottom of the demethanizer (Q) is the mixed carbon 2 (21); part of the mixed carbon 2 (21) is refluxed to the bottom of the demethanizer (Q) through the demethanizer reboiler (T); the mixed carbon 2 (21) enters the ethylene refining tower (U), the top of the ethylene refining tower (U) is passed through the ethylene refining tower condenser (V) and the ethylene refining tower reflux tank (W) to obtain a high-purity ethylene product (22), and enters the liquid phase ethylbenzene production device (Y) to obtain an ethylbenzene product (24); part of the ethane (23) at the bottom of the ethylene refining tower (U) is refluxed to the bottom of the ethylene refining tower (U) through the ethylene refining tower reboiler (X), and the rest enters the ethane furnace (Z) for cracking; The crude ethane (14) is obtained at the bottom of the crude ethylene fraction tower (G); The gas phase at the top of the solvent regeneration tower (K) is passed through a solvent recovery tower top condenser (L) and a solvent recovery tower reflux tank (M) as a solvent regeneration tower top concentrated gas (15), and part of the concentrated gas is refluxed to the solvent regeneration tower (K); the solvent regeneration tower top concentrated gas (15) is combined with the crude ethane (14) at the bottom of the ethylene crude fraction tower (G) as an ethane furnace feed (16) and enters an ethane furnace (Z); the ethane furnace (Z) is cracked to obtain an ethane furnace output (25).

2. The method for separating concentrated gas based on dry gas raw material change according to claim 1, characterized in that: A high-purity ethylene product (22) is obtained at the top of the ethylene refining tower (U), part of which enters the liquid phase ethylbenzene production unit (Y) and part is produced as an ethylene product. The destination of the ethylene product (22) is adjusted according to demand.

3. The method for separation of concentrated gas based on dry gas raw material change according to claim 1 or 2, characterized in that: When the utility refrigerant is replenished to the top of the ethylene crude fraction tower (G), the crude ethylene compressor (O), the demethanizer feed cooler (P), the demethanizer (Q), and the ethylene refining tower (U) are shut down; The gas phase of the first flash gas (7) from the first flash tank (B) is combined with the raw material dry gas (1) through the circulating dry gas compressor (D) to form a mixed dry gas and enter the absorption tower (A); the lean solvent (2) from the bottom of the solvent regeneration tower (K) and the semi-lean solvent (3) from the liquid phase of the second flash tank (C) enter the absorption tower (A) from the top and the middle of the absorption tower (A) respectively; the lean solvent (2) and the semi-lean solvent (3) are countercurrently contacted with the mixed dry gas to absorb the carbon two components in the mixed dry gas; the top of the absorption tower (A) is the methane hydrogen mixed gas (4), which is expanded by the newly added expander (J) and then heat-exchanged with the gas phase at the top of the ethylene crude fraction tower (G) through the crude fraction tower top gas-expanded gas heat exchanger (H); The rich absorption liquid (5) in the bottom of the absorption tower (A) enters the primary flash tank (B); The liquid-phase primary flash bottom liquid (8) of the primary flash tank (B) enters the secondary flash tank (C); the gas-phase secondary flash gas (9) of the secondary flash tank (C) is cooled by the crude fraction tower feed-crude fraction tower top gas heat exchanger (F), and then enters the middle and upper position of the ethylene crude fraction tower (G) as the flash tank concentrated gas (12); part of the liquid-phase secondary flash bottom liquid (10) of the secondary flash tank (C) is used as the semi-lean solvent (3), and the remaining part is used as the solvent regeneration tower feed (11) to enter the solvent regeneration tower (K); the top gas of the solvent regeneration tower (K) is passed through the solvent recovery tower top condenser (L) and the solvent recovery tower reflux tank (M) as the solvent regeneration tower top concentrated gas (15), and part of the concentrated gas is refluxed to the solvent regeneration tower (K); the solvent regeneration tower top concentrated gas (15) is combined with the crude ethane (14) at the bottom of the ethylene crude fraction tower (G) as the ethane furnace feed (16) to enter the ethane furnace (Z); The top of the ethylene crude fraction tower (G) is passed through a crude fraction tower top gas-expanded gas heat exchanger (H) and a crude fraction tower reflux tank (I) to obtain product-grade ethylene, part of which is refluxed to the ethylene crude fraction tower (G), and the product-grade ethylene enters a crude fraction tower feed-crude fraction tower top gas heat exchanger (F) for heat exchange to obtain product-grade ethylene after heat exchange, and the product-grade ethylene after heat exchange enters a liquid phase ethylbenzene production device (Y), part of which is produced as an ethylene product, and the destination of the product-grade ethylene (17) is flexibly adjusted according to demand; the ethane (14) at the bottom of the ethylene crude fraction tower (G) enters an ethane furnace (Z) for cracking.

4. A post-enrichment gas separation device based on dry gas raw material change, characterized in that: Used to realize the concentrated gas separation method based on dry gas raw material change according to any one of claims 1 to 3; the concentrated gas separation device based on dry gas raw material change comprises an absorption tower (A), a primary flash tank (B), a secondary flash tank (C), a circulating dry gas compressor (D), an ethylene crude fraction tower reboiler (E), a crude fraction tower feed-coarse fraction tower top gas heat exchanger (F), an ethylene crude fraction tower (G), a crude fraction tower top gas-expanded gas heat exchanger (H), a crude fraction tower reflux tank (I), a newly added expander (J), a solvent recovery Tower (K), solvent recovery tower top condenser (L), solvent recovery tower reflux tank (M), solvent recovery tower reboiler (N), crude ethylene compressor (O), demethanizer feed cooler (P), demethanizer (Q), demethanizer condenser (R), demethanizer reflux tank (S), demethanizer reboiler (T), ethylene refining tower (U), ethylene refining tower condenser (V), ethylene refining tower reflux tank (W), ethylene refining tower reboiler (X), liquid phase ethylbenzene production device (Y), ethane furnace device (Z); The raw dry gas is passed to the bottom of the absorption tower (A); the top of the absorption tower (A) is connected to the newly added expander (J) and the crude fraction tower top gas-expanded gas heat exchanger (H) in sequence; the absorption tower (A) is connected to the first-stage flash tank (B); the top of the first-stage flash tank (B) is connected to the circulating dry gas compressor (D) and the bottom of the absorption tower (A) in sequence; the bottom of the first-stage flash tank (B) is connected to the second-stage flash tank (C); the bottom of the second-stage flash tank (C) is divided into two branches, one of which is connected to the middle of the absorption tower (A) and the other is connected to the middle of the absorption tower (A). connected to a solvent recovery tower (K); the top of the solvent recovery tower (K) is connected in sequence to a solvent recovery tower top condenser (L) and a solvent recovery tower reflux tank (M); the solvent recovery tower reflux tank (M) is divided into two branches, one branch is connected back to the solvent recovery tower (K), and the other branch is connected to the ethane furnace device (Z); the bottom of the solvent recovery tower (K) is divided into two branches, one branch is connected to a solvent recovery tower reboiler (N) and back to the solvent recovery tower (K), and the other branch is connected to the top of the absorption tower (A); The top of the secondary flash tank (C) is connected to the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F); the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F) is respectively connected to the ethylene crude fraction tower (G) and the crude ethylene compressor (O); the top of the ethylene crude fraction tower (G) is connected to the top gas-expansion gas heat exchanger of the crude fraction tower (H); the product is extracted from the top gas-expansion gas heat exchanger of the crude fraction tower (H) and connected to the reflux tank (I) of the crude fraction tower; the reflux tank (I) of the crude fraction tower is divided into two branches, one of which is connected back to the top of the ethylene crude fraction tower (G), and the other circuit is connected to the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F); the bottom of the ethylene crude fraction tower (G) is divided into two branches, one of which is connected to the reboiler of the ethylene crude fraction tower (E) and connected back to the ethylene crude fraction tower (G), and the other branch is connected to the ethane furnace device (Z); The crude ethylene compressor (O) is connected to the demethanizer feed cooler (P) and the demethanizer (Q) in sequence; the top of the demethanizer (Q) is connected to the demethanizer condenser (R) and the demethanizer reflux tank (S) in sequence; the demethanizer reflux tank (S) is divided into two branches, one of which is connected back to the demethanizer (Q) and the other is used for extraction; the bottom of the demethanizer reflux tank (S) is divided into two branches, one of which is connected to the demethanizer reboiler (T) and back, and the other is connected to the ethylene refining Tower (U); the top of the ethylene refining tower (U) is connected to the ethylene refining tower condenser (V) and the ethylene refining tower reflux tank (W) in sequence; the ethylene refining tower reflux tank (W) is divided into two branches, one branch is connected back to the ethylene refining tower (U), and the other branch is connected to the liquid phase ethylbenzene production device (Y); the bottom of the ethylene refining tower (U) is divided into two branches, one branch is connected to the ethylene refining tower reboiler (X) and back to the ethylene refining tower (U), and the other branch is connected to the ethane furnace device (Z).

5. The concentrated gas separation device based on dry gas raw material change according to claim 4 is characterized in that: When the utility refrigerant reaches the top of the ethylene crude fraction tower (G), shut down the crude ethylene compressor (O), the demethanizer feed cooler (P), the demethanizer (Q), and the ethylene refining tower (U); the raw dry gas is passed to the bottom of the absorption tower (A); the top of the absorption tower (A) is connected in sequence to the newly added expander (J) and the first inlet of the crude fraction tower top gas-expanded gas heat exchanger (H); the bottom of the absorption tower (A) is connected to the primary flash tank (B); the top of the primary flash tank (B) is connected in sequence to the circulating dry gas compressor (D) and the bottom of the absorption tower (A); the bottom of the primary flash tank (B) is connected to the secondary flash tank (C); The bottom of the flash tank (C) is divided into two branches, one of which is connected to the middle of the absorption tower (A), and the other is connected to the solvent recovery tower (K); the top of the solvent recovery tower (K) is connected to the solvent recovery tower top condenser (L) and the solvent recovery tower reflux tank (M) in sequence, and the solvent recovery tower reflux tank (M) is divided into two branches, one of which is connected back to the solvent recovery tower (K), and the other is connected to the middle and lower part of the ethylene crude fractionation tower (G); the bottom of the solvent recovery tower (K) is divided into two branches, one of which is connected to the solvent recovery tower reboiler (N) and back to the solvent recovery tower (K), and the other is connected to the top of the absorption tower (A); The top of the secondary flash tank (C) is connected to the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F); the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F) are respectively connected to the middle of the ethylene crude fraction tower (G) and the liquid phase ethylbenzene production device (Y); the top of the ethylene crude fraction tower (G) is connected to the second inlet of the top gas-expanded gas heat exchanger of the crude fraction tower (H); the first outlet of the top gas-expanded gas heat exchanger of the crude fraction tower (H) produces a product, and the second outlet is connected to the reflux tank (I) of the crude fraction tower; the reflux tank (I) of the crude fraction tower is divided into two branches, one of which is connected back to the top of the ethylene crude fraction tower (G), and the other circuit is connected to the feed of the crude fraction tower-the top gas heat exchanger of the crude fraction tower (F); the bottom of the ethylene crude fraction tower (G) is divided into two branches, one of which is connected to the reboiler of the ethylene crude fraction tower (E) and connected back to the ethylene crude fraction tower (G), and the other branch is connected to the ethane furnace device (Z).

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