Process and system for efficiently removing dimethyl ether in mixed C4

Abstract

The invention discloses a process and a system for efficiently removing dimethyl ether in mixed C4, relates to the technical field of petrochemical engineering separation, and aims to solve the problems that in the prior art, when dimethyl ether in C4 is removed, the desorption efficiency of the dimethyl ether is low, waste heat in a rectifying tower is not sufficiently recycled when the dimethyl ether is rectified, and the desorption efficiency of the dimethyl ether is low. According to the scheme, the device comprises an adsorption tower and a divided-wall rectifying tower, the adsorption tower comprises a heat preservation shell, an inner shell fixedly arranged on the inner wall of the heat preservation shell, a spiral flow guide ring, a refrigerant conveying pipe fixedly arranged on the inner wall of the upper part of the heat preservation shell, a refrigerant output pipe fixedly arranged on the inner wall of the lower part of the heat preservation shell, a desorption gas output pipe and a steam conveying pipe. According to the invention, the modified MOF adsorbent can be used for carrying out low-temperature adsorption on dimethyl ether in C4 mixed gas, the desorption efficiency is improved, heat in the divided-wall rectifying tower can be recovered, waste heat is used for regenerating the adsorbent, and the energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical separation, and particularly to a process and system for efficiently removing dimethyl ether from mixed C4. Background Art

[0002] Refers to a hydrocarbon mixture containing four carbon atoms. The main components include n-butane, isobutane, isobutene, 1,3-butadiene, 1-butene, 2-butene, etc. It mainly comes from the refining production process and the by-products of ethylene production by cracking. In addition to alkanes, the C4 fraction in refineries also contains a large amount of olefins, but contains little or no butadiene and alkynes. The alkane content in the C4 fraction produced by co-production through cracking is low, mainly butene and butadiene.

[0003] During the alkylation reaction process, butadiene can generate acid-soluble oil (ASO) with a very high molecular weight. The acid-soluble oil will increase the dry point of the alkylated oil, reduce the octane number and yield. When separating these ASOs, some acids will also be lost. Butadiene is also prone to polymerize on the surface of the alkylation catalyst to form gums, clogging the catalyst pores and reducing the catalyst life. Dimethyl ether is also a main impurity consuming acid in alkylation, and it will reduce the yield and octane number of the alkylated oil.

[0004] In the prior art, the removal of dimethyl ether mainly relies on a single adsorption method (such as molecular sieve) or rectification method, but there are the following problems:

[0005] Adsorption method: low adsorption capacity, frequent regeneration, and competitive adsorption between dimethyl ether and C4 components (such as butene and butane), with poor selectivity; rectification method: the boiling points of dimethyl ether and some C4 components are close (such as the boiling point of dimethyl ether is -24.9°C, and that of isobutane is -11.7°C), resulting in high separation energy consumption. Based on the prior art, when removing dimethyl ether from C4 in petrochemical industry, it is easy to cause low desorption efficiency of dimethyl ether, and there is no sufficient recovery of the waste heat in the rectification tower during the rectification of dimethyl ether, resulting in high energy consumption. Summary of the Invention

[0006] The present invention provides a process and system for efficiently removing dimethyl ether from mixed C4, which solves the problems in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A high-efficiency dimethyl ether removal system for mixed C4 hydrocarbons, comprising an adsorption tower and a dividing-wall distillation column. The adsorption tower includes a heat-insulating outer shell, an inner shell fixedly arranged on the inner wall of the heat-insulating outer shell, a spiral guide ring, a refrigerant delivery pipe fixedly arranged on the upper inner wall of the heat-insulating outer shell, a refrigerant output pipe fixedly arranged on the lower inner wall of the heat-insulating outer shell, a desorbed gas output pipe fixedly arranged on the upper inner wall of the heat-insulating outer shell, and a steam delivery pipe fixedly arranged on the lower inner wall of the heat-insulating outer shell. An adsorption mechanism is arranged inside the inner shell. The adsorption mechanism includes a plurality of adsorption rings composed of metal-organic framework materials loaded with ionic liquids and a plurality of gas distributors with ventilation holes on the outer walls. A water tank is arranged between the adsorption tower and the dividing-wall distillation column. A waste heat recovery mechanism is arranged inside the water tank. The waste heat recovery mechanism includes a recovery pipe flange-connected to the lower outer wall of the heat-coupling structure of the dividing-wall distillation column, a reflux pipe flange-connected to the lower outer wall of the heat-coupling structure of the dividing-wall distillation column, and a heat exchange pipe. A waste heat pipe is flange-connected to the top inner wall of the dividing-wall distillation column, and the bottom end of the waste heat pipe extends into the water tank.

[0009] Preferably, an exhaust pipe is fixedly arranged on the inner wall at the center of the top of the heat-insulating outer shell, and an air inlet pipe is fixedly arranged on the inner wall at the center of the bottom of the heat-insulating outer shell. A refrigerant delivery pipe and a desorbed gas output pipe are fixedly arranged on the inner wall of the top of the heat-insulating outer shell, and a refrigerant output pipe and a steam delivery pipe are fixedly arranged on the inner wall of the bottom of the heat-insulating outer shell.

[0010] Preferably, a plurality of the adsorption rings are respectively bolt-connected to the upper inner wall of the inner shell, and a plurality of the gas distributors are respectively bolt-connected to the upper inner wall of the inner shell. A plurality of the gas distributors respectively abut against the bottom outer walls of a plurality of the adsorption rings.

[0011] Through the above scheme, a refrigerant such as liquid ammonia or ethylene glycol is delivered into the space between the heat-insulating outer shell and the inner shell through the refrigerant delivery pipe. The refrigerant moves along the spiral guide ring to reduce the temperature inside the inner shell. The air inlet pipe delivers the C4 mixed gas into the inner shell. The gas distributor makes the C4 mixed gas uniformly contact the adsorption rings. The metal-organic framework (MOF) material (such as MIL-101(Cr)) and the loaded ionic liquid (such as [BMIM][PF6]) in the adsorption rings desorb the dimethyl ether in the C4 mixed gas.

[0012] Preferably, a C4 delivery pipe is flange-connected to the outer wall at the top of the exhaust pipe, and one end of the C4 delivery pipe is flange-connected to the outer wall at the middle air inlet end of the dividing-wall distillation column.

[0013] Preferably, a water inlet pipe is fixedly arranged on one inner wall of the water tank, and a tank cover is bolt-connected to the outer wall at the top of the water tank.

[0014] Preferably, a flange joint is fixedly provided on the inner wall of the lower part of one side of the water tank, and the two flange joints are respectively connected to the outer walls of one ends of the recovery pipe and the return pipe through bolts. The lower two ends of the heat exchange pipe are respectively fixedly provided on the inner walls of one ends of the two flange joints.

[0015] Preferably, a steam connection pipe is connected to the outer wall of the upper part of one side of the water tank through a flange, and one end of the steam connection pipe is connected to the outer wall of the bottom of the steam delivery pipe through a flange. The top of the desorbed gas output pipe is connected to a desorbed gas delivery pipe through a flange, and one end of the desorbed gas delivery pipe is connected to the inner wall of the middle part of one side of the dividing wall distillation column through a flange.

[0016] Through the above solution, the heat at the bottom of the dividing wall distillation column is transferred to the water in the water tank through the heat coupling structure at the bottom of the column. At the same time, the waste heat pipe transports the waste heat at the top of the column to the water to heat the water in the water tank in real time, causing water vapor to be generated in the water tank. Subsequently, the valve is opened, and the water vapor enters the inner shell to regenerate the multiple adsorption rings.

[0017] A high-efficiency process for removing dimethyl ether from mixed C4 includes the following steps:

[0018] Step S1: The C4 raw material enters the adsorption tower after pretreatment for dehydration and desulfurization, and dimethyl ether is removed under the action of the modified MOF adsorbent in the adsorption ring under a low-temperature environment.

[0019] Step S2: The C4 after adsorption enters the dividing wall distillation column. Dimethyl ether is taken out from the top of the column, light C4 components such as isobutane are taken out from the middle part of the side of the dividing wall distillation column, and heavy components such as butene are obtained at the bottom of the column.

[0020] Step S3: The coupling structure at the bottom exchanges heat with the heavy components at the bottom of the column, causing the heat transfer agent in the coupling structure to absorb heat and liquefy. Subsequently, it liquefies and releases heat in the heat exchange pipe. At the same time, the waste heat steam at the top of the column enters the water tank, and the waste heat is used to heat the water in the water tank, causing the water in the water tank to be heated to generate water vapor.

[0021] Step S4: The valve is opened, and the water vapor enters the adsorption tower along the steam connection pipe to heat and regenerate the adsorbent in the multiple adsorption rings. The desorbed dimethyl ether enters the dividing wall distillation column along the desorbed gas delivery pipe.

[0022] Preferably, the internal temperature of the adsorption tower in step S1 is -10°C - 0°C.

[0023] The beneficial effects of the present invention are:

[0024] 1. The refrigerant delivery pipe transports refrigerant, such as liquid ammonia or ethylene glycol, into the space between the thermal insulation shell and the inner shell. The refrigerant moves along the spiral guide ring to reduce the temperature inside the inner shell. The inlet pipe transports the C4 mixed gas into the inner shell, and the gas distributor enables the C4 mixed gas to uniformly contact the adsorption ring. The metal-organic framework (MOF) material (such as MIL-101(Cr)) and the supported ionic liquid (such as [BMIM][PF6]) in the adsorption ring desorb dimethyl ether from the C4 mixed gas, and it is possible to use the modified MOF adsorbent to perform low-temperature adsorption of dimethyl ether in the C4 mixed gas, improving the desorption efficiency.

[0025] 2. The heat coupling structure at the bottom of the dividing-wall distillation column transfers the heat at the bottom to the water in the water tank. At the same time, the waste heat pipe transports the waste heat at the top of the column to the water to heat the water in the water tank in real time, generating water vapor in the water tank. Subsequently, the valve is opened, and the water vapor enters the inner shell to regenerate the multiple adsorption rings. It is possible to recover the heat in the dividing-wall distillation column and use the waste heat to regenerate the adsorbent, reducing the energy consumption.

[0026] In summary, the present invention can use the modified MOF adsorbent to perform low-temperature adsorption of dimethyl ether in the C4 mixed gas, improving the desorption efficiency. It can recover the heat in the dividing-wall distillation column and use the waste heat to regenerate the adsorbent, reducing the energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic front view structure diagram of the overall high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0028] Figure 2 It is a schematic front view sectional structure diagram of the overall high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0029] Figure 3 It is a schematic front view sectional structure diagram of the adsorption tower of the high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0030] Figure 4 It is a schematic front view structure diagram of the adsorption tower of the high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0031] Figure 5 It is a schematic bottom view structure diagram of the adsorption tower of the high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0032] Figure 6 It is a schematic front view sectional structure diagram of the adsorption mechanism of the high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0033] Figure 7The front view structural schematic diagram of the waste heat recovery mechanism of a high-efficiency dimethyl ether removal system for mixed C4 in the present invention.

[0034] In the figure: 1, adsorption tower; 101, heat preservation outer shell; 102, inner shell; 103, diversion ring; 104, exhaust pipe; 105, intake pipe; 106, refrigerant delivery pipe; 107, refrigerant output pipe; 108, desorbed gas output pipe; 109, steam delivery pipe; 2, adsorption mechanism; 201, adsorption ring; 202, gas distributor; 3, dividing wall distillation column; 4, C4 delivery pipe; 5, water tank; 6, tank cover; 7, waste heat recovery mechanism; 701, recovery pipe; 702, reflux pipe; 703, flange joint; 704, heat exchange pipe; 8, steam connection pipe; 9, desorbed gas delivery pipe; 10, waste heat pipe. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0036] Example 1, referring to Figures 1-6 , A high-efficiency dimethyl ether removal system for mixed C4 includes an adsorption tower 1 and a dividing wall distillation column 3. The adsorption tower 1 includes a heat preservation outer shell 101, an inner shell 102 fixedly arranged on the inner wall of the heat preservation outer shell 101, a spiral diversion ring 103, a refrigerant delivery pipe 106 fixedly arranged on the upper inner wall of the heat preservation outer shell 101, a refrigerant output pipe 107 fixedly arranged on the lower inner wall of the heat preservation outer shell 101, a desorbed gas output pipe 108 fixedly arranged on the upper inner wall of the heat preservation outer shell 101, and a steam delivery pipe 109 fixedly arranged on the lower inner wall of the heat preservation outer shell 101. An exhaust pipe 104 is fixedly arranged on the inner wall at the center of the top of the heat preservation outer shell 101, and an intake pipe 105 is fixedly arranged on the inner wall at the center of the bottom of the heat preservation outer shell 101. The refrigerant delivery pipe 106 and the desorbed gas output pipe 108 are fixedly arranged on the inner wall of the top of the heat preservation outer shell 101, and the refrigerant output pipe 107 and the steam delivery pipe 109 are fixedly arranged on the inner wall of the bottom of the heat preservation outer shell 101. An adsorption mechanism 2 is arranged inside the inner shell 102. The adsorption mechanism 2 includes a plurality of adsorption rings 201 composed of metal-organic framework materials loaded with ionic liquids and a plurality of gas distributors 202 with ventilation holes on the outer wall. The plurality of adsorption rings 201 are respectively connected to the upper inner wall of the inner shell 102 by bolts, and the plurality of gas distributors 202 are respectively connected to the upper inner wall of the inner shell 102 by bolts. The plurality of gas distributors 202 respectively abut against the bottom outer walls of the plurality of adsorption rings 201.

[0037] Example 2, referring to Figure 7, A high-efficiency dimethyl ether removal system for mixed C4 hydrocarbons further includes a C4 transfer pipe 4 flange-connected to the outer wall of the top of the exhaust pipe 104. One end of the C4 transfer pipe 4 is flange-connected to the outer wall of the middle air inlet end of the dividing-wall distillation column 3. A water tank 5 is provided between the adsorption tower 1 and the dividing-wall distillation column 3. A water inlet pipe is fixedly installed on one inner wall of the water tank 5. A tank cover 6 is bolted to the outer wall of the top of the water tank 5. A waste heat recovery mechanism 7 is arranged in the water tank 5. The waste heat recovery mechanism 7 includes a recovery pipe 701 flange-connected to the outer wall of the lower part of the heat coupling structure of the dividing-wall distillation column 3, a return pipe 702 flange-connected to the outer wall of the lower part of the heat coupling structure of the dividing-wall distillation column 3, and a heat exchange pipe 704. A flange joint 703 is fixedly installed on the inner wall of the lower part of one side of the water tank 5. The two flange joints 703 are respectively bolted to the outer wall of one end of the recovery pipe 701 and the return pipe 702. The lower ends of both ends of the heat exchange pipe 704 are fixedly installed on the inner walls of one ends of the two flange joints 703. A waste heat pipe 10 is flange-connected to the inner wall of the top of the dividing-wall distillation column 3. The bottom end of the waste heat pipe 10 extends into the water tank 5. A steam connection pipe 8 is flange-connected to the outer wall of the upper part of one side of the water tank 5. One end of the steam connection pipe 8 is flange-connected to the outer wall of the bottom of the steam transfer pipe 109. The top of the desorbed gas output pipe 108 is flange-connected to a desorbed gas transfer pipe 9. One end of the desorbed gas transfer pipe 9 is flange-connected to the inner wall of the middle part of one side of the dividing-wall distillation column 3.

[0038] Example 3, A high-efficiency dimethyl ether removal process for mixed C4 hydrocarbons includes the following steps:

[0039] Step S1: The C4 raw material enters the adsorption tower 1 after pretreatment for dehydration and desulfurization. Under a low-temperature environment, dimethyl ether is removed under the action of the modified MOF adsorbent in the adsorption ring 201. The internal temperature of the adsorption tower 1 in step S1 is -10°C - 0°C;

[0040] Step S2: The adsorbed C4 enters the dividing-wall distillation column 3. Dimethyl ether is taken out from the top of the column. Light C4 components (such as isobutane, etc.) are taken out from the middle part of the side of the dividing-wall distillation column 3, and heavy components (such as 1-butene, etc.) are obtained at the bottom of the column;

[0041] Step S3: The coupling structure at the bottom of the column exchanges heat with the bottom heavy components, so that the heat exchange agent in the coupling structure absorbs heat and liquefies. Then it liquefies and releases heat in the heat exchange pipe 704. At the same time, the waste heat steam at the top of the column enters the water tank 5, and the waste heat is used to heat the water in the water tank 5, so that the water in the water tank 5 is heated to generate water vapor;

[0042] Step S4: Open the valve, and the water vapor enters the adsorption tower 1 along the steam connection pipe to heat and regenerate the adsorbent in the plurality of adsorption rings 201. The desorbed dimethyl ether enters the dividing-wall distillation column 3 along the desorbed gas transfer pipe 9.

[0043] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0044] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered by the protection scope of the present invention.

Claims

1. A high-efficiency dimethyl ether removal system for mixed C4 hydrocarbons, comprising an adsorption tower (1) and a dividing-wall distillation column (3), characterized in that, The adsorption tower (1) includes a heat-insulating outer shell (101), an inner shell (102) fixedly arranged on the inner wall of the heat-insulating outer shell (101), a spiral flow guide ring (103), a refrigerant delivery pipe (106) fixedly arranged on the upper inner wall of the heat-insulating outer shell (101), a refrigerant output pipe (107) fixedly arranged on the lower inner wall of the heat-insulating outer shell (101), a desorbed gas output pipe (108) fixedly arranged on the upper inner wall of the heat-insulating outer shell (101), and a steam delivery pipe (109) fixedly arranged on the lower inner wall of the heat-insulating outer shell (101); An adsorption mechanism (2) is arranged inside the inner shell (102). The adsorption mechanism (2) includes a plurality of adsorption rings (201) composed of metal-organic framework materials loaded with ionic liquids and a plurality of gas distributors (202) with ventilation holes opened on the outer walls; A water tank (5) is arranged between the adsorption tower (1) and the dividing-wall distillation column (3); A waste heat recovery mechanism (7) is arranged inside the water tank (5). The waste heat recovery mechanism (7) includes a recovery pipe (701) connected to the lower outer wall of the heat-coupling structure of the dividing-wall distillation column (3) by a flange, a reflux pipe (702) connected to the lower outer wall of the heat-coupling structure of the dividing-wall distillation column (3) by a flange, and a heat exchange pipe (704); A waste heat pipe (10) is connected to the top inner wall of the dividing-wall distillation column (3) by a flange, and the bottom end of the waste heat pipe (10) extends into the water tank (5).

2. The high-efficiency dimethyl ether removal system for mixed C4 according to claim 1, characterized in that, An exhaust pipe (104) is fixedly arranged on the inner wall at the center of the top of the heat-insulating outer shell (101), and an air inlet pipe (105) is fixedly arranged on the inner wall at the center of the bottom of the heat-insulating outer shell (101). A refrigerant delivery pipe (106) and a desorbed gas output pipe (108) are fixedly arranged on the top inner wall of the heat-insulating outer shell (101), and a refrigerant output pipe (107) and a steam delivery pipe (109) are fixedly arranged on the bottom inner wall of the heat-insulating outer shell (101).

3. The high-efficiency dimethyl ether removal system for mixed C4 according to claim 1, characterized in that, A plurality of the adsorption rings (201) are respectively connected to the upper inner wall of the inner shell (102) by bolts, and a plurality of the gas distributors (202) are respectively connected to the upper inner wall of the inner shell (102) by bolts. A plurality of the gas distributors (202) respectively abut against the bottom outer walls of a plurality of the adsorption rings (201).

4. A high-efficiency dimethyl ether removal system for mixed C4 according to claim 2, characterized in that, A C4 delivery pipe (4) is connected to the top outer wall of the exhaust pipe (104) by a flange, and one end of the C4 delivery pipe (4) is connected to the outer wall of the middle air inlet end of the dividing-wall distillation column (3) by a flange.

5. The highly efficient dimethyl ether removal system for mixed C4 according to claim 1, wherein, A water inlet pipe is fixedly arranged on one inner wall of the water tank (5), and a tank cover (6) is connected to the top outer wall of the water tank (5) by bolts.

6. The high-efficiency dimethyl ether removal system for mixed C4 according to claim 1, characterized in that A flange joint (703) is fixedly arranged on the lower inner wall on one side of the water tank (5), and two flange joints (703) are respectively connected to one end outer walls of the recovery pipe (701) and the reflux pipe (702) by bolts. The lower two ends of the heat exchange pipe (704) are respectively fixedly arranged on the inner walls of one ends of the two flange joints (703).

7. The high-efficiency dimethyl ether removal system for mixed C4 according to claim 2, wherein On the upper outer wall of one side of the water tank (5), a steam connection pipe (8) is connected by a flange, and one end of the steam connection pipe (8) is connected by a flange to the bottom outer wall of the steam delivery pipe (109). The top of the desorbed gas output pipe (108) is connected by a flange to a desorbed gas delivery pipe (9), and one end of the desorbed gas delivery pipe (9) is connected by a flange to the inner wall of the middle part of one side of the dividing wall distillation column (3).

8. The removal process of the dimethyl ether efficient removal system for mixed C4 according to claim 1, characterized in that, It includes the following steps: Step S1: The C4 raw material enters the adsorption tower (1) after pretreatment (dehydration and desulfurization). Under a low-temperature environment, dimethyl ether is removed under the action of the modified MOF adsorbent in the adsorption ring (201). Step S2: The C4 after adsorption enters the dividing wall distillation column (3). Dimethyl ether is taken out from the top of the column. Light C4 components (isobutane, etc.) are taken out from the middle part of the side of the dividing wall distillation column (3), and heavy components (1-butene, etc.) are obtained at the bottom of the column. Step S3: The coupling structure at the bottom of the column exchanges heat with the heavy components at the bottom of the column, so that the heat transfer medium in the coupling structure absorbs heat and liquefies. Subsequently, it liquefies and releases heat in the heat exchange tube (704). At the same time, the waste heat steam at the top of the column enters the water tank (5), and the water in the water tank (5) is heated by using the waste heat, so that the water in the water tank (5) is heated to generate water vapor. Step S4: Open the valve, and the water vapor enters the adsorption tower (1) along the steam connection pipe to heat and regenerate the adsorbent in the plurality of adsorption rings (201). The desorbed dimethyl ether enters the dividing wall distillation column (3) along the desorbed gas delivery pipe (9).

9. The high-efficiency dimethyl ether removal process for mixed C4 according to claim 8, characterized in that, In step S1, the internal temperature of the adsorption tower (1) is -10°C - 0°C.

Images