CN104830371B - The apparatus and method of C2 in a kind of recovery oil refinery dry gas - Google Patents

Abstract

The invention discloses a device for recovering C2 in refinery dry gas, which includes a PSA unit, a compression unit and an oil absorption unit; the PSA unit includes a section of PSA device; the compression unit includes a compressor and a liquid separation tank, wherein the The inlet of one stage of PSA device is connected with raw material dry gas, the outlet of said one stage of PSA device is connected with the inlet of compressor, and the outlet of compressor is connected with the inlet of liquid separation tank. The beneficial effects of the present invention are as follows: firstly use a section of PSA with low energy consumption to initially concentrate the raw material dry gas, and then use the absorption and desorption method with high recovery rate and high product purity to further purify the PSA enriched gas, and the gas in the absorption unit enters The temperature of material, absorbent and tower top reflux is 40°C, and the cooling and condensation temperature can be reached by using circulating cooling water without refrigeration equipment. Compressed condensate is used as absorbent, and there is no need to introduce C4 absorbent from other devices. The invention also discloses a method for recovering C2 in refinery dry gas.

Description

A device and method for recovering C2 in refinery dry gas

technical field

The present invention relates to a device and method for recovering C2 in refinery dry gas. Specifically, it relates to C2 and C2+ components in refinery dry gas. The oil absorption method further removes methane, hydrogen, nitrogen, oxygen and other light components in the enriched gas, and the finally obtained product is used as a raw material for ethylene production, and belongs to the technical field of tail gas recovery in petroleum refineries.

Background technique

At present, the methods for recovering C2 from dry gas in refineries mainly include two-stage PSA method and shallow cooling oil method.

The two-stage PSA method has two stages of PSA, the first stage of PSA is the main adsorption unit, and the PSA enriched gas is used as the replacement gas to further replace the adsorbent bed after the adsorption step, so as to reduce the residual methane in the bed, etc. The concentration of non-ideal components is used to achieve the purpose of improving the purity of the enriched product gas. The function of the second stage PSA is to recover and replace C2 and C2+ components in the exhaust gas to improve the total recovery rate.

Shallow cooling oil method compresses and boosts the original dry gas to about 4.0MPa, then uses refinery C4 as the absorbent, and absorbs C2 and C3 components in the dry gas in the absorption tower at a shallow cooling temperature of 10-15°C , to achieve the purpose of removing methane, hydrogen and other components. Then, in the desorption tower, the C4 absorbent that has absorbed the C2 and C3 components is desorbed to obtain a C2-enriched product gas. The methane-rich hydrogen fuel gas at the top of the absorption tower carries C3 and C4 components, and gasoline or naphtha is used to absorb the C3 and C4 components in the fuel gas. The shallow cooling oil method needs to provide cooling capacity through the lithium bromide refrigeration unit to cool the dry gas and absorbent to 10-15 °C.

The two-stage PSA method has the advantages of low energy consumption and low operating pressure, but it also has the disadvantages of low recovery rate and low product gas purity. The C2 recovery rate is about 84% to 88%, and the methane content in the product gas is about It is about 10% (V).

The shallow cooling oil method has the advantages of high recovery rate (90% to 93%) and high purity of product gas (methane content in product gas is less than 5% (V)), but at the same time it has high energy consumption, high operating pressure, and lithium bromide needs to be installed. The refrigerating unit needs to introduce C4 absorbent from an external device and has a large degree of correlation with other devices.

Contents of the invention

The purpose of the present invention is to provide a device and method for recovering C2 in refinery dry gas, which greatly reduces energy consumption while ensuring high recovery rate and high product purity.

In order to achieve the above object, the present invention is specifically realized through the following technical solutions:

A device for recovering C2 in refinery dry gas, including a PSA unit, a compression unit and an oil absorption unit;

The PSA unit comprises a section of PSA device;

The compression unit includes a compressor and a liquid separator tank, wherein the inlet of the first-stage PSA device communicates with the raw material dry gas, the outlet of the first-stage PSA device communicates with the inlet of the compressor, and the outlet of the compressor communicates with the inlet of the liquid separator tank. connected;

The oil absorption unit includes a deoxygenation demethanizer, a desorption tower, an absorption tower, and a naphtha absorption tower, and the inlet of the deoxygenation demethanizer is communicated with the bottom compressed condensate outlet of the liquid separation tank through a pipeline, and the The liquid phase outlet at the bottom of the deoxygenation demethanizer is communicated with the inlet of the desorption tower through a pipeline, and the gas outlet at the top of the deoxygenation demethanizer and the gas outlet at the top of the liquid separation tank are respectively connected to the absorber through pipelines. The gas inlet of the tower, the liquid phase outlet at the bottom of the desorption tower is connected to the liquid inlet of the absorption tower through a pumping pipeline, the gas outlet at the top of the absorption tower is communicated with the inlet of the naphtha absorption tower through a pipeline, and the The liquid phase outlet at the bottom of the absorption tower communicates with the inlet of the deoxygenation and demethanizer through a pumping pipeline.

The fuel gas at the top outlet of the naphtha absorption tower is connected to the pipe network, and the rich naphtha at the bottom outlet of the naphtha absorption tower is deethylene-cracked.

On the pumping pipeline at the bottom of the desorption tower, a branch is drawn for cracking of C4 products to remove ethylene.

The top outlet of the desorption tower is connected to the reflux tank through pipelines, and the bottom of the reflux tank is transported back to the desorption tower through the top reflux pump, and the top of the reflux tank is provided with a pipeline to de-ethylene-crack the ethylene-rich gas.

A condensate pump is also included, and the condensate pump is arranged on the pipeline at the bottom outlet of the liquid separation tank.

The group of PSA adsorbers includes 10 PSA adsorbers, and the working process of each PSA adsorber includes adsorption, pressure equalization drop, reverse discharge, evacuation, pressure equalization rise, and final charge according to the process sequence. The 10 PSA adsorbers enter the adsorption process alternately. , and at any time, there are 4 PSA adsorbers in the adsorption process, while the other 6 PSA adsorbers are in the pressure equalization, reverse discharge, evacuation, pressure equalization, and final charge processes.

A method for recovering C2 in refinery dry gas, comprising the following steps:

In the first step, the raw material dry gas is concentrated by a section of PSA, and the C2 and C2+ components in the raw material dry gas are adsorbed by the adsorber, and the components such as hydrogen, methane, nitrogen, etc. that are not easily adsorbed are discharged from the top of the adsorber, and then The adsorbed C2 and C2+ components are desorbed by reverse discharge and vacuum pumping to obtain concentrated and desorbed gas;

In the second step, the concentrated and desorbed gas obtained in the first step is compressed and then cooled and separated. The pressure during the compression process is 2-5MPa. After the compressed gas is cooled to 40°C, it enters the liquid separation tank for liquid separation. Fuel noncondensable gas collected from the top of the liquid separator tank and compressed condensate collected from the bottom of the tank;

In the 3rd step, the gas outlet at the top of the deoxygenation demethanizer and the gas outlet at the top of the liquid separation tank are respectively connected to the lower part of the absorption tower through pipelines for absorption, and the absorption tower utilizes C4 absorbent to absorb C2, C3 and other components, to obtain a C4-rich absorbent, and fuel gases such as methane and hydrogen that are not absorbed flow out from the top of the absorption tower;

In step 4, the C4-rich absorbent obtained in step 3 and the compressed condensate obtained in step 2 are sent to the deoxygenation demethanizer for stripping, so that the oxygen and methane contained in the C4-rich absorbent and compressed condensate are After being removed, the absorbent at the bottom of the tower is sent to the desorption tower, and the stripping gas containing C2 and C3 at the top of the tower is repeated in step 3;

In step 5, the absorbent at the bottom of the tower in step 4 is sent to the desorption tower, and the bottom of the desorption tower is heated by low-pressure steam to analyze the C2 and C3 components in the absorbent, and the overhead distillate of the desorption tower is cooled After reaching 40°C, enter the reflux tank for liquid separation, the gas phase of the reflux tank is discharged as C2-rich product gas, and the liquid phase of the reflux tank is transported back to the top of the desorption tower through the top reflux pump;

In the 6th step, the unabsorbed methane, hydrogen and other fuel gases obtained in step 3 and flowing out from the top of the absorption tower enter the lower part of the naphtha absorption tower, and are reversely contacted with the naphtha that enters from the upper part of the tower to make the fuel gas Light hydrocarbons such as C3 and C4 carried in the gas are absorbed by naphtha. The fuel gas at the top of the tower goes to the fuel gas pipeline network, and the naphtha-rich ethylene device at the bottom of the tower is used as cracking material.

In step 5, the C4 absorbent at the bottom of the desorption tower is pumped up, heat-exchanged, and cooled to 40°C and then divided into two streams, one is the C4 product delivery device with a smaller flow rate, and the other is a larger flow rate The recycled C4 absorbent is sent to the upper part of the absorption tower in the third step as absorbent.

The beneficial effects of the present invention are as follows: firstly use a section of PSA with low energy consumption to initially concentrate the raw material dry gas, and then use the absorption and desorption method with high recovery rate and high product purity to further purify the PSA enriched gas, and the gas in the absorption unit enters The temperature of material, absorbent and tower top reflux is 40°C, and the cooling and condensation temperature can be reached by using circulating cooling water without refrigeration equipment. Compressed condensate is used as absorbent, and there is no need to introduce C4 absorbent from other devices.

Under the premise of ensuring high recovery rate and high product purity (C2 recovery rate 93%, product gas methane content 3%-5% (V)), the energy consumption index is 20-30% lower than that of shallow cooling oil method.

Description of drawings

The present invention will be described in further detail below according to the drawings and embodiments.

Fig. 1 is a structural diagram of the present invention.

Fig. 2 is a block diagram of a PSA device.

In the picture:

1. One section of PSA device; 2. Compressor; 3. Liquid separation tank; 4. Deoxygenation and demethanization tower; 5. Desorption tower; 6. Absorption tower; 7. Naphtha absorption tower; 8. Reflux tank; 9. Tower Top reflux pump; 10. Condensate pump; 11. Raw material gas buffer tank; 12. Cold dryer; 13. PSA adsorber; 14. Vacuum pump; 15. Reverse degassing buffer tank;

detailed description

As shown in Figure 1-2, in this embodiment, a device for recovering C2 in refinery dry gas includes a PSA unit, a compression unit and an oil absorption unit;

The PSA unit includes a section of PSA device 1, including a raw gas buffer tank 11, a cold dryer 12, a group of PSA adsorbers 13, a vacuum pump 14, a reverse deflation buffer tank 15, a concentrated gas buffer tank 16, and a raw gas buffer tank 11 is connected to the inlet of the cold dryer 12 through a pipeline, and the outlet of the cold dryer 12 is connected to the PSA adsorber 13, and the outlet of the PSA adsorber 13 is connected to the concentrated gas buffer tank 16 through the vacuum pump 14, and the PSA adsorption The reverse deflation branch of the device 13 is connected with the reverse deflation buffer tank 15 and the concentrated gas buffer tank 16 respectively, the outlet of the reverse deflated buffer tank 15 is connected with the concentrated gas buffer tank 16, and the concentrated gas buffer tank 16 The outlet of the compressor is connected;

The compression unit includes a compressor 2 and a liquid separation tank 3, wherein the inlet of the first stage of the PSA device 1 communicates with the raw material dry gas, the outlet of the first stage of the PSA device 1 communicates with the inlet of the compressor 2, and the outlet of the compressor 2 It is communicated with the inlet of liquid separator tank 3;

The oil absorption unit includes a deoxygenation demethanizer 4, a desorption tower 5, an absorption tower 6, and a naphtha absorption tower 7, and the inlet of the deoxygenation demethanizer 4 is communicated with the bottom outlet of the liquid separation tank 3 through a pipeline , the liquid phase outlet at the bottom of the deoxygenation demethanizer 4 is communicated with the inlet of the desorption tower 5 through a pipeline, and the gas outlet at the top of the deoxygenation demethanizer 4 and the gas outlet at the top of the liquid separation tank 3 are respectively passed through The pipeline is connected to the gas inlet of the absorption tower 6, the liquid phase outlet at the bottom of the desorption tower 5 is connected to the liquid inlet of the absorption tower 6 by a pumping pipeline, and the gas outlet at the top of the absorption tower 6 is connected to the gas outlet through a pipeline. The inlet of the naphtha absorption tower 7 is communicated, and the liquid phase outlet at the bottom of the absorption tower 6 is communicated with the inlet of the deoxygenation demethanizer 4 through a pumping pipeline.

The fuel gas at the top outlet of the naphtha absorption tower 7 is connected to the pipe network, and the rich naphtha at the bottom outlet of the naphtha absorption tower 7 is deethylene cracked.

A branch is drawn on the pumping pipeline at the bottom of the desorption tower 5 for cracking of C4 products to remove ethylene.

The top outlet of the desorption tower 5 is connected with the reflux tank 8 through a pipeline, and the bottom of the reflux tank 8 is transported back to the desorption tower 5 through the top reflux pump 9, and the top of the reflux tank is provided with a pipeline to de-ethylene-crack the ethylene-rich gas.

A condensate pump 10 is also included, and the condensate pump is arranged on the pipeline at the bottom outlet of the liquid separation tank.

A group of PSA adsorbers includes 10 PSA adsorbers. The working process of each PSA adsorber includes adsorption, pressure equalization drop, reverse discharge, evacuation, pressure equalization rise, and final filling in the process sequence. The 10 PSA adsorbers enter the adsorption alternately. process, and at any one time, 4 PSA adsorbers are in the adsorption process, while the other 6 PSA adsorbers are in the pressure equalization, reverse discharge, evacuation, pressure equalization, and final charge processes.

The raw material dry gas from the outside world is buffered and separated by the raw material gas buffer tank, and then enters the cold dryer to remove saturated water and a small amount of heavy hydrocarbons contained in the raw material dry gas. The raw material gas after lyophilization enters the bottom of 4 PSA adsorbers which are in the adsorption state. Most of the effective components above C2 in the gas are selectively adsorbed by the adsorbent, and the weakly adsorbed components H2, N2, CH4, etc. pass through the adsorber. The bed is sent out from the top of the adsorber as adsorption waste gas. The remaining 6 towers are operated in other steps (pressure equalization, reverse discharge, evacuation, pressure equalization, final filling), and the 10 towers are switched alternately. The switching of each step of the adsorber is completed by the automatic switching of the program-controlled valve. The effective components above C2 (that is, enriched gas) adsorbed on the adsorbent are discharged from the adsorber in the reverse discharge and evacuation steps. The high-pressure part of the reverse deflation (concentrated gas) discharged from the reverse discharge step enters the reverse deflation buffer tank first, and is sent to the concentrated gas buffer tank after buffering and decompression, and the low pressure part directly enters the concentrated gas buffer tank to lift The concentrated gas is sent to the compressor of the compression unit after being buffered and stabilized. The evacuation of the PSA device is completed by the vacuum pump, and the pumped air (concentrated gas) is cooled to normal temperature by the after-cooler of the vacuum pump, and then enters the concentrated gas buffer tank.

A method for recovering C2 in refinery dry gas, comprising the following steps:

In the first step, the raw material dry gas is concentrated by a section of PSA, and the C2 and C2+ components in the raw material dry gas are adsorbed by the adsorber, and the components such as hydrogen, methane, nitrogen, etc. that are not easily adsorbed are discharged from the top of the adsorber, and then The adsorbed C2 and C2+ components are desorbed by reverse discharge and vacuum pumping to obtain concentrated and desorbed gas;

In the second step, the concentrated and desorbed gas obtained in the first step is compressed and then cooled and separated. The pressure during the compression process is 2-5MPa. After the compressed gas is cooled to 40°C, it enters the liquid separation tank for liquid separation. Fuel noncondensable gas collected from the top of the liquid separator tank and compressed condensate collected from the bottom of the tank;

In the 3rd step, the gas outlet at the top of the deoxygenation demethanizer and the gas outlet at the top of the liquid separation tank are respectively connected to the lower part of the absorption tower through pipelines for absorption, and the absorption tower utilizes C4 absorbent to absorb C2, C3 and other components, to obtain a C4-rich absorbent, and fuel gases such as methane and hydrogen that are not absorbed flow out from the top of the absorption tower;

In step 4, the C4-rich absorbent obtained in step 3 and the compressed condensate obtained in step 2 are sent to the deoxygenation demethanizer for stripping, so that the oxygen and methane contained in the C4-rich absorbent and compressed condensate are After being removed, the absorbent at the bottom of the tower is sent to the desorption tower, and the stripping gas containing C2 and C3 at the top of the tower is repeated in step 3;

In step 5, the absorbent at the bottom of the tower in step 4 is sent to the desorption tower, and the bottom of the desorption tower is heated by low-pressure steam to analyze the C2 and C3 components in the absorbent, and the overhead distillate of the desorption tower is cooled After reaching 40°C, it enters the reflux tank for liquid separation. The gas phase of the reflux tank is discharged as C2-rich product gas, and the liquid phase of the reflux tank is transported back to the top of the desorption tower through the top reflux pump.

In the 6th step, the unabsorbed methane, hydrogen and other fuel gases obtained in step 3 and flowing out from the top of the absorption tower enter the lower part of the naphtha absorption tower, and are reversely contacted with the naphtha that enters from the upper part of the tower to make the fuel gas Light hydrocarbons such as C3 and C4 carried in the gas are absorbed by naphtha. The fuel gas at the top of the tower goes to the fuel gas pipeline network, and the naphtha-rich ethylene device at the bottom of the tower is used as cracking material.

In step 5, the C4 absorbent at the bottom of the desorption tower is pumped up, heat-exchanged, and cooled to 40°C and then divided into two streams, one is the C4 product delivery device with a smaller flow rate, and the other is a larger flow rate The recycled C4 absorbent is sent to the upper part of the absorption tower in the third step as absorbent.

Claims (8)

1. A device for reclaiming C in refinery dry gas, comprising a PSA unit, a compression unit and an oil absorption unit; It is characterized in that, The PSA unit includes a section of PSA device, including a raw material gas buffer tank, a cold dryer, a set of PSA adsorbers, a vacuum pump, a reverse deflation buffer tank, and a concentrated gas buffer tank. The raw material gas buffer tank is connected to the cold dryer through pipelines. The inlet of the cold dryer is connected to the PSA adsorber, the outlet of the PSA adsorber is connected to the concentrated gas buffer tank through a vacuum pump, and the reverse deflation branch of the PSA adsorber is connected to the reverse deflate buffer tank respectively. It is connected with the concentrated gas buffer tank, the outlet of the reverse deflation buffer tank is connected with the concentrated gas buffer tank, and the outlet of the concentrated gas buffer tank is connected with the compressor; The compression unit includes a compressor and a liquid separator tank, wherein the inlet of the first-stage PSA device communicates with the raw material dry gas, the outlet of the first-stage PSA device communicates with the inlet of the compressor, and the outlet of the compressor communicates with the inlet of the liquid separator tank. connected; The oil absorption unit includes a deoxygenation demethanizer, a desorption tower, an absorption tower, and a naphtha absorption tower, and the inlet of the deoxygenation demethanizer is communicated with the bottom compressed condensate outlet of the liquid separation tank through a pipeline, and the The liquid phase outlet at the bottom of the deoxygenation demethanizer is communicated with the inlet of the desorption tower through a pipeline, and the gas outlet at the top of the deoxygenation demethanizer and the gas outlet at the top of the liquid separation tank are respectively connected to the absorber through pipelines. The gas inlet of the tower, the liquid phase outlet at the bottom of the desorption tower is connected to the liquid inlet of the absorption tower through a pumping pipeline, the gas outlet at the top of the absorption tower is communicated with the inlet of the naphtha absorption tower through a pipeline, and the The liquid phase outlet at the bottom of the absorption tower communicates with the inlet of the deoxygenation and demethanizer through a pumping pipeline. 2. a kind of device as claimed in claim 1 reclaims C in refinery dry gas, it is characterized in that, the fuel gas of the top outlet of described naphtha absorption tower goes to pipe network to communicate, and described naphtha absorption tower The rich naphtha at the bottom outlet goes to ethylene cracking. 3. The device for recovering C2 in the dry gas of a refinery as claimed in claim 1, wherein a branch is drawn on the pumping pipeline at the bottom of the desorption tower for C4 products to be deethylene cracked. 4. The device for recovering C2 in a kind of refinery dry gas as claimed in claim 1, wherein the top outlet of the desorption tower is connected with the reflux tank through a pipeline, and the bottom of the reflux tank is transported by the tower top reflux pump Back to the desorption tower, the top of the reflux tank is provided with a pipeline to de-ethylene-crack the ethylene-rich gas. 5. The device for recovering C2 in refinery dry gas as claimed in claim 1, further comprising a condensate pump, and the condensate pump is arranged on the pipeline at the bottom outlet of the liquid separation tank. 6. A kind of device as claimed in claim 1 reclaiming C in refinery dry gas, it is characterized in that one group of PSA adsorbers comprises 10 PSA adsorbers, and the working process of each PSA adsorber comprises adsorption by technological order , pressure drop, reverse discharge, evacuation, pressure rise, final charge, 10 PSA adsorbers enter the adsorption process alternately, and at any time, 4 PSA adsorbers are in the adsorption process, while the other 6 PSA adsorbers are in the adsorption process. They are respectively in the process of equalizing pressure drop, reverse discharge, evacuation, equalizing pressure rise and final charging. 7. A method for recovering C in refinery dry gas, comprising the following steps: In the first step, the raw material dry gas is concentrated through a section of PSA, and the C2 and C2+ components in the raw material dry gas are adsorbed by the adsorber, and the hydrogen, methane, and nitrogen components that are not easily adsorbed are discharged from the top of the adsorber, and then passed through Inverted and vacuumed to desorb the adsorbed C2 and C2+ components to obtain concentrated and desorbed gas; In the second step, the concentrated and desorbed gas obtained in the first step is compressed and then cooled and separated. The pressure during the compression process is 2-5MPa. After the compressed gas is cooled to 40°C, it enters the liquid separation tank for liquid separation. Fuel noncondensable gas collected from the top of the liquid separator tank and compressed condensate collected from the bottom of the tank; In the third step, the gas outlet at the top of the deoxygenation demethanizer and the gas outlet at the top of the liquid separation tank are respectively connected to the lower part of the absorption tower through pipelines for absorption, and the C4 absorbent is used in the absorption tower to absorb the C2 and C3 groups in the gas points, to obtain the absorbent rich in C4, and the unabsorbed methane and hydrogen fuel gas flow out from the top of the absorption tower; In step 4, the C4-rich absorbent obtained in step 3 and the compressed condensate obtained in step 2 are sent to the deoxygenation demethanizer for stripping, so that the oxygen and methane contained in the C4-rich absorbent and compressed condensate are After being removed, the absorbent at the bottom of the tower is sent to the desorption tower, and the stripping gas containing C2 and C3 at the top of the tower is repeated in step 3; In step 5, the absorbent at the bottom of the tower in step 4 is sent to the desorption tower, and the bottom of the desorption tower is heated by low-pressure steam to analyze the C2 and C3 components in the absorbent, and the overhead distillate of the desorption tower is cooled After reaching 40°C, enter the reflux tank for liquid separation, the gas phase of the reflux tank is discharged as C2-rich product gas, and the liquid phase of the reflux tank is transported back to the top of the desorption tower through the top reflux pump; In the 6th step, the unabsorbed methane and hydrogen fuel gas obtained in step 3 from the tower top of the absorption tower flow into the lower part of the naphtha absorption tower, and are reversely contacted with the naphtha that enters from the upper part of the tower to make the fuel gas The C3 and C4 light hydrocarbons carried in the gas are absorbed by naphtha, the fuel gas at the top of the tower goes to the fuel gas pipeline network, and the ethylene-rich naphtha at the bottom of the tower is used as cracking material. 8. A method for recovering C2 in refinery dry gas as claimed in claim 7, characterized in that, in the 5th step, the C4 absorbent at the bottom of the desorption tower is boosted by a pump, heat exchanged, and cooled to 40°C Afterwards, it is divided into two strands, one is the C4 product delivery device with a smaller flow rate, and the other is the circulating C4 absorbent with a larger flow rate, which is sent to the upper part of the absorption tower in the third step as absorbent.