CN211871870U - System for recovering carbon second fraction in refinery dry gas - Google Patents
System for recovering carbon second fraction in refinery dry gas Download PDFInfo
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- CN211871870U CN211871870U CN201922164244.4U CN201922164244U CN211871870U CN 211871870 U CN211871870 U CN 211871870U CN 201922164244 U CN201922164244 U CN 201922164244U CN 211871870 U CN211871870 U CN 211871870U
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Abstract
The invention provides a system for recovering carbon-two fraction in refinery dry gas by using a partition tower, which comprises a compressor, a heat exchanger and the partition tower; the outlet of the compressor is connected with the inlet of the heat exchanger, and the outlet of the heat exchanger is connected with the inlet of the partition wall tower. The system for recovering the carbon second fraction in the refinery dry gas has the advantages of simple process, short flow and low energy consumption. The recovery of the carbon dioxide fraction (mainly ethylene and ethane) from the refinery dry gas is achieved using a single column. The refinery dry gas is compressed and cooled and then enters from the middle part of the absorption tower, and the absorbent enters from the top of the absorption tower and is in countercurrent contact with the refinery dry gas to absorb the carbon dioxide and the above fractions; and distilling the carbon dioxide fraction from the tower of the absorption tower, purifying and then sending the purified carbon dioxide fraction to an ethylene device to realize the separation and recovery of ethane and ethylene. C3 and C3 lower olefins are distilled from the bottom of the column together with the absorbent, and the overhead gas enters a fuel gas system or other utilization devices.
Description
Technical Field
The utility model relates to a refinery dry gas handles field, more specifically relates to a system for retrieving C2 fraction in refinery dry gas.
Background
Refinery dry gas is mainly derived from secondary processing processes of crude oil, such as catalytic cracking, hydrocracking, catalytic reforming, coking and the like. At present, most of refinery dry gas C2 fractions in China are not fully utilized, and some high-value C2 fractions are burnt or utilized in a low-quality mode, such as delayed coking dry gas and C2 fractions in catalytic cracking products are mostly burnt as fuels, and the like, so that great resource waste and environmental pollution are caused.
The method for recovering the C2 fraction from the refinery dry gas mainly comprises cryogenic separation, medium-cold oil absorption, light-cold oil absorption, complex separation, pressure swing adsorption and the like, and various methods have own characteristics. The cryogenic separation method has mature process, high ethylene recovery rate but large investment, and higher energy consumption for recovering the dilute ethylene; the complex separation method has higher ethylene recovery rate, but has strict requirements on impurities in raw materials, higher pretreatment cost and needs a special complex absorbent; the pressure swing adsorption method has simple operation and lower energy consumption, but the product purity is lower and the ethylene recovery rate is lower.
The oil absorption method mainly separates gas mixture by using different solubilities of the absorbent on each component in the gas, firstly absorbs heavy components of C2 and above C2 by using the absorbent, separates out non-condensable gases such as methane, hydrogen, oxygen and the like, and then separates each component in the absorbent by adopting a rectification method. The method has the characteristics of small scale, strong adaptability, low investment cost and the like.
CN 104557385B and CN 104557386B propose a recovery system and a recovery method for mixed dry gas of a refinery plant. The system comprises: the system comprises an unsaturated dry gas recovery device, a saturated dry gas recovery device and a reabsorption tower; the refinery dry gas is respectively subjected to recovery treatment by an absorption-desorption method, and a saturated C2 concentrated gas product and an unsaturated C2 concentrated gas product are obtained from the top of the desorption tower and are respectively sent to an ethylene device cracking furnace and an alkali wash tower. The method has high recovery rate and low energy consumption, and basically has no influence on the operation of an ethylene device.
CN 104557384B discloses a refinery mixed dry gas recovery system and a recovery method. The system comprises: the system comprises a compressor, a heat exchanger, an absorption tower, a reabsorption tower, a desorption tower, a purification device and a rough separation tower; the compressor is connected with the heat exchanger and then connected with the absorption tower, and the top of the absorption tower is connected with the reabsorption tower; the absorption tower kettle is connected with the desorption tower, the top of the desorption tower is connected with the purification device and then connected with the rough separation tower, and the desorption tower kettle is connected with the upper part of the absorption tower. Recovering the carbon dioxide component in the dry gas by an absorbent, sending the gas at the top of the absorption tower to a reabsorption tower with a small amount of the absorbent, sending the liquid at the bottom of the absorption tower to a desorption tower, returning the poor solvent at the bottom of the desorption tower to the absorption tower through heat exchange, sending the gas phase at the top of the tower to a rough separation tower, extracting the ethylene-rich gas at the top of the rough separation tower, sending the ethylene-rich gas to a demethanizer of an ethylene device, extracting the ethane-rich gas at the bottom of the rough separation tower, and sending the ethane-rich. The absorbent is a carbon four fraction containing n-butane and isobutane, a saturated liquefied gas containing saturated carbon three and carbon four, or a carbon five fraction containing n-pentane and isopentane; the reabsorber is gasoline, or heavy naphtha and aromatic raffinate oil.
CN 104557387B discloses a refinery mixed dry gas recovery system and a recovery method. The system comprises: the device comprises an absorption tower, a desorption tower, a rough separation tower, a purification device, a gasoline absorption tower and a gasoline desorption tower; the compressor is connected with the heat exchanger and then connected with the absorption tower, the top of the absorption tower is connected with the gasoline absorption tower, and the bottom of the absorption tower is connected with the desorption tower; the carbon dioxide component in the dry gas is recovered through one set of absorption-desorption, the gas phase at the top of the desorption tower enters the rough separation tower, and the entrained absorbent is recovered through the other set of absorption-desorption. The ethylene-rich gas is extracted from the top of the coarse fractionating tower and sent to a demethanizer of the ethylene device, and the ethane-rich gas is extracted from the bottom of the coarse fractionating tower and sent to a cracking furnace of the ethylene device.
CN 1640992 proposes a low pressure, low temperature process for the recovery of C2 and heavier hydrocarbons. The process adopts low pressure technology, avoids the generation of nitric acid resin under the condition of recovery temperature of-100 ℃, can keep higher olefin yield, and simultaneously avoids potential danger. Belongs to cryogenic separation, and has large investment and high energy consumption.
US 6308532 proposes a process for recovering ethylene and propylene from refinery dry gas by withdrawing C3, C4, C5, C6 liquid phase from an absorber drum and recycling a part of the liquid phase to the top of the tower, maintaining the top of the tower at not lower than-95 ℃, while withdrawing propylene and ethylene products in the side. The process belongs to cryogenic separation, and has large investment and high energy consumption.
CN 101063048A discloses a method for absorbing and separating refinery catalytic cracking dry gas by using intercooling oil, which comprises the steps of compressing, removing acid gas, drying, purifying, absorbing, desorbing, cold quantity recycling, roughly dividing and the like, and has the advantages of low absorbent cost and the like.
CN 101812322A discloses an absorption-separation catalytic cracking dry gas method with the absorption temperature of 5-15 ℃ and the adoption of an expander and a cold box for recovering cold, which improves the yield of ethylene and ethane, but has complex flow, large investment and high energy consumption.
CN101759516A discloses a method for separating refinery catalytic dry gas by an oil absorption method, which comprises the steps of compression, absorption, desorption, reabsorption and the like, and carbon pentahydrocarbon is used as an absorbent to recover carbon two and three fractions in the catalytic dry gas. However, this method is only used for recovering catalytic dry gas, and the ethylene recovery rate is low. The process of patent CN101759518A differs from that of CN101759516A in that a carbon tetracarbon is used as an absorbent.
In addition, CN105647583A discloses a novel absorption stabilization process and system, wherein the stabilization column in the absorption stabilization system is a dividing wall distillation column, specifically a dividing wall column with a middle partition plate, and the side line light gasoline distillation range of the dividing wall column is 40-100 ℃. CN107298988A discloses a refining absorption stabilizing process and a refining absorption stabilizing system, wherein the absorption stabilizing system comprises a gas-liquid balance tank, a rich gas compressor, a rich gas balance tank, an absorption tower, a desorption-stabilization dividing wall tower, a reabsorption tower, a regeneration tank, a desorption gas balance tank and a vacuum pump; the desorption-stabilization dividing wall tower is an upper dividing wall type dividing wall tower, a partition plate is arranged in the middle of the desorption-stabilization dividing wall tower along the longitudinal direction, the interior of the desorption-stabilization dividing wall tower is divided into a desorption area, a stabilization area and a stripping area, and the partition plate directly extends from the top of the dividing wall tower but is not contacted with the bottom of the dividing wall tower. The fields of the two patents are catalytic cracking devices absorption stabilizing systems, the processing raw materials are gasoline, and clear cutting of liquefied gas, light gasoline and heavy gasoline can be realized by adopting a bulkhead rectifying tower.
The invention mainly solves the problem of how to recycle the C2 fraction in the refinery dry gas to realize high-value utilization by using the method which has short flow, low energy consumption and less investment because the common refinery dry gas contains a large amount of high-value C2 fractions and the like.
The C2 fraction is ethylene and ethane, the ethylene is the main raw material of the polymerization monomer, the value is high, after recovery, the environmental pollution is reduced, the value of the raw material is also improved, the ethane is the high-quality raw material for ethylene cracking, and after recovery, the ethane can enter an ethane furnace of an ethylene device, thus reflecting the advantage of refining and chemical integration.
At present, the method for recovering the C2 fraction from the refinery dry gas is a shallow cold oil absorption process, a middle cold oil absorption process and the like, and the processes are generally a 3-tower or 4-tower process, so that the energy consumption is high and the investment is large.
SUMMERY OF THE UTILITY MODEL
In order to solve the problems of high-value utilization of C2 fraction in refinery dry gas, short flow, low energy consumption and effective recovery of C2 fraction in a refinery and realize the overall optimization of refinery integration, the invention provides a system for efficiently recovering C2 fraction in refinery dry gas by using a single tower.
The invention provides a recovery unit of C2 fraction in refinery dry gas, comprising: a compressor, a heat exchanger, a dividing wall tower; the outlet of the compressor is connected with the inlet of the heat exchanger, and the outlet of the heat exchanger is connected with the inlet of the partition wall tower.
In the apparatus for recovering a C2 fraction from a refinery dry gas, it is preferable that a condenser is provided in the top of the dividing wall column and a reboiler is provided in the reactor.
The invention provides a device for recovering a C2 fraction in refinery dry gas, wherein, preferably, a bulkhead of the bulkhead tower is arranged at the top, and two sides of the bulkhead are respectively provided with a condenser.
In the apparatus for recovering a C2 fraction from a refinery dry gas according to the present invention, it is preferable that the dividing wall of the dividing wall column is provided in the middle.
The recovery device of the C2 fraction in the refinery dry gas provided by the invention preferably further comprises a purification system connected with the dividing wall tower, and an outlet of the purification system is connected with the ethylene unit alkaline washing tower.
In the apparatus for recovering a C2 fraction from a refinery dry gas, preferably, the outlet of the dividing wall column is connected to the adsorbent inlet of the dividing wall column via a line.
The recovery device of the C2 fraction in the refinery dry gas provided by the invention is characterized in that the number of theoretical plates of the dividing wall tower is preferably 20-90.
The recovery device of the C2 fraction in the refinery dry gas provided by the invention is characterized in that the number of theoretical plates of the dividing wall tower is preferably 30-80.
The invention provides a recovery device of C2 fraction in refinery dry gas, wherein, the area ratio of the feed side and the product extraction side of a partition wall tower is preferably 1:9 to 9: 1.
The invention provides a device for recovering a C2 fraction in refinery dry gas, wherein, preferably, the top of a dividing wall tower is connected with a refinery fuel gas system through a pipeline.
According to some embodiments of the invention, the invention may also state the following:
a system for efficiently recovering a C2 fraction from refinery dry gas using a single column, the system comprising: the system comprises a compressor, a heat exchanger, an absorption tower and a purification system; the compressor is connected with the heat exchanger and then connected with the absorption tower, and the absorption tower is connected with the purification system; wherein the absorption tower is a partition tower, the top of the absorption tower is provided with a condenser, and the tower kettle is provided with a reboiler.
The recommended absorber, i.e. divided wall column structure, may be: the dividing wall is at the top and two condensers and one reboiler, or the dividing wall may be in the middle and one condenser and one reboiler.
The area ratio of the feeding side of the absorption tower, namely the dividing wall tower, to the product extraction side is 1:9 to 9: 1.
In the invention, the dry gas can enter from the middle part or the lower part of the absorption tower, and the absorbent preferably enters from the top of the absorption tower.
In the invention, the top of the absorption tower is provided with a pipeline connected with a refinery fuel gas system, so that the distillate components of the top of the absorption tower enter the refinery fuel gas system. The overhead fraction of the absorber column can also be used for other purposes.
In the invention, the distilled component of the tower kettle of the absorption tower can be used as an absorbent and can be recycled to the top of the absorption tower, and part of the distilled component can be discharged from the device, the distilled C2 fraction in the tower is subjected to acid gas removal, deoxidation, arsenic removal, mercury removal and other treatment by a purification device, a purification system is connected with an ethylene device alkaline washing tower, and the purified material flow is sent to the ethylene device alkaline washing tower, so that the aim of recovering low-carbon olefin in a refinery by utilizing the main process of an ethylene device is fulfilled.
Prior art dividing wall columns (dividing wall columns) are commonly used as fractionation columns, and have little use in the art, either individually as a stabilizer Column after being used in a stripper Column, or by combining the functions of both to form a desorption-stabilizer dividing wall Column, as described above. The present inventors have found that a divided wall column can achieve separation of hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, hydrogen sulfide and methane from C2 fractions, C3 fractions and above.
In the invention, when the bulkhead tower is taken as the absorption tower, the operation pressure can be 2.0-6.0MPa and the tower top temperature is 0-45 ℃ when the theoretical plate number selected by the absorption tower (bulkhead tower) is 20-90. More preferred conditions are: the number of theoretical plates is 30-80, the operating pressure is 2.0-5.0MPa, and the tower top temperature is 10-30 ℃.
Part of the components of the absorption tower reactor is used as absorbent to be recycled to the absorption tower, and part of the components can be discharged from the device, or all of the components can be refluxed as absorbent, or all of the components can be discharged from the device. And recommending part of the absorbent to be recycled to the absorption tower for reuse and part of the absorbent to be discharged out of the device.
The invention provides a system for recovering C2 fraction from a refinery by using a dividing wall tower, which has the advantages of simple process, short flow and low energy consumption. The absorption tower uses a bulkhead tower, so that the recovery of C2 fraction (mainly ethylene and ethane) in the refinery dry gas is realized by using a single tower. The method comprises the following steps that (1) refinery dry gas containing low-carbon olefins from a refinery enters an absorption tower from the middle part or the lower part of the absorption tower through a compressor for pressurization and a heat exchanger, and an absorbent enters from the top of the absorption tower and is distilled from the bottom of the absorption tower; distilling C3 and C3 lower olefins and absorbent from the bottom of the column; the component distilled from the absorption column was a C2 fraction. The adaptability of refinery dry gas and absorbent is strong.
Drawings
FIG. 1 is a schematic diagram of a system for recovering a C2 fraction from refinery dry gas using a dividing wall column according to an embodiment of the present invention.
Description of reference numerals:
1-refinery dry gas; 2-a compressor; 3-a heat exchanger; 4-an absorption column; 5-a purification system; 6-gas phase components are discharged from the top of the absorption tower; 7-fresh absorbent; 8-distilling out components from the tower kettle of the absorption tower; 9-recycling the components distilled out of the tower kettle of the absorption tower as an absorbent; 10-distillation of the fraction (C2 fraction) in the absorber column; 11-purified C2 fraction to ethylene plant; 12-post-mix absorbent; 13-tower still distillation of the absorption tower to obtain components (C3 and fractions above);
fig. 2 is several possible forms of the absorption column of fig. 1 above, but is not limited to these forms.
Description of reference numerals:
form A: one condenser and one reboiler;
form B: two condensers and one reboiler;
Detailed Description
The present invention will be further described with reference to the following examples
Example (b):
the system for recovering the C2 fraction in the refinery dry gas by using the dividing wall tower comprises a compressor, a heat exchanger and an absorption tower, wherein the compressor is connected with the heat exchanger; the method comprises the steps of pressurizing a refinery dry gas 1 containing low-carbon olefin by a compressor 2 and a heat exchanger 3, feeding the refinery dry gas into an absorption tower from the lower part of an absorption tower 4, feeding an absorbent 12 into the absorption tower 4 from the upper part, discharging a gas 6 at the top of the absorption tower from a device, distilling a component 13 at the bottom of the absorption tower, mixing a part of distilled component 9 with a fresh absorbent 7, circulating the mixture to the absorption tower to be used as the absorbent, discharging a part of the component 8 from the device, distilling a component 10 from the absorption tower, and purifying a component 11 purified by a purifying device 5 to be a purified C2 fraction which can be used by an ethylene device or other devices, so that the C2 fraction in the refinery dry gas is recovered by using a partition wall of the. The top of the absorption tower is provided with a condenser, and the tower is provided with a reboiler.
The composition of the refinery dry gas is shown in Table 1
TABLE 1 refinery Low carbon olefin compositions
| Component name | Component content (mass fraction) |
| Hydrogen gas | 0.0249 |
| Nitrogen gas | 0.1727 |
| Oxygen gas | 0.0132 |
| Carbon monoxide | 0.0121 |
| Carbon dioxide | 0.0274 |
| Hydrogen sulfide | 0.0010 |
| Methane | 0.2222 |
| Ethylene | 0.2017 |
| Ethane (III) | 0.1708 |
| Propylene (PA) | 0.0953 |
| Propane | 0.0208 |
| 1-butene | 0.0140 |
| N-butane | 0.0127 |
| N-pentane | 0.0111 |
The refinery dry gas is mainly refinery gas containing low-carbon olefin. Mainly comprises coking dry gas, reforming dry gas, catalytic cracking gas, hydrocracking gas and the like, but is not limited to the compositions of the dry gas and the dry gas shown in the table 1.
The method comprises the following steps:
1) compression
2) Cooling down
3) Absorption of
4) Purification
Example 1
The refinery dry gas is compressed to 5MPa and then cooled to 10 ℃, the absorption tower adopts the structure A shown in figure 2, the number of tower plates is 65, the area ratio of the feeding side and the product extraction side of the absorption tower, namely the partition tower, is 2:8, n-butane is adopted as an absorbent, and the product composition of the obtained refinery C2 fraction is shown in table 2.
TABLE 2 composition of C2 fraction product from refinery after absorption
In this example, the recovery rate of C2 from a refinery was 95% or more, and the mass fraction of C2 distilled out of the column was 95% or more.
Example 2
The refinery dry gas is compressed to 4MPa and then cooled to 15 ℃, the absorption tower adopts the structure B shown in the figure 2, the number of tower plates is 75, n-butene is adopted as an absorbent under the condition that the area ratio of the feeding side and the product extraction side of the absorption tower, namely a partition tower, is 5:5, and the product composition of the obtained refinery C2 fraction is shown in a table 3.
TABLE 3 post absorption refinery C2 fraction product composition
In this example, the recovery rate of C2 from a refinery was 91% or more, and the mass fraction of C2 distilled out of the column was 95% or more.
Claims (8)
1. An apparatus for recovering C2 fraction from refinery dry gas, comprising: a compressor, a heat exchanger, a dividing wall tower; the outlet of the compressor is connected with the inlet of the heat exchanger, and the outlet of the heat exchanger is connected with the inlet of the partition wall tower; the tower top of the partition tower is provided with a condenser, and the tower kettle is provided with a reboiler; the partition wall of the partition wall tower is arranged at the top, and two sides of the partition wall are respectively provided with a condenser.
2. The apparatus for recovering fraction C2 from refinery dry gas as claimed in claim 1, wherein: the dividing wall of the dividing wall tower is in the middle.
3. The apparatus for recovering fraction C2 from refinery dry gas as claimed in claim 1, wherein: the purifying system is connected with the next-door tower, and an outlet of the purifying system is connected with an ethylene unit alkaline washing tower.
4. The apparatus for recovering fraction C2 from refinery dry gas as claimed in claim 1, wherein: the outlet of the bulkhead tower is connected with the adsorbent inlet of the bulkhead tower through a pipeline.
5. The recovery device of C2 fraction in refinery dry gas according to any one of claims 1-4, wherein: the number of theoretical plates of the dividing wall tower is 20-90.
6. The apparatus for recovering fraction C2 from refinery dry gas as claimed in claim 5, wherein: the number of theoretical plates of the dividing wall tower is 30-80.
7. The recovery device of C2 fraction in refinery dry gas according to any one of claims 1-4, wherein: the ratio of the area of the feed side to the product take-off side of the dividing wall column is from 1:9 to 9: 1.
8. The recovery device of C2 fraction in refinery dry gas according to any one of claims 1-4, wherein: the top of the partition tower is connected with a refinery fuel gas system through a pipeline.
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