A method and system for removing sour gases from ethylene cracking gas

Abstract

The application discloses a method and system for removing acid gas from ethylene cracking gas. The method comprises: ethylene cracking gas containing acid gas sequentially passing through a first supergravity amine washing, a second supergravity amine washing and water washing; the first supergravity amine washing adopts a first compounded amine liquid, and the second supergravity amine washing adopts a second compounded amine liquid. The application uses the supergravity technology to strengthen the amine washing process and uses the compounded amine liquid, greatly improves the acid gas removal depth, and can reach that hydrogen sulfide and carbon dioxide are less than 1 μL / L respectively without needing an alkali washing unit. Compared with the prior art, the acid gas removal depth in the amine washing process can be greatly improved, the acid gas removal process is simplified, and source reduction of ethylene waste alkali liquid is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas purification, in particular to a method and system for removing acid gas from ethylene cracking gas. BACKGROUND

[0002] Ethylene is an important basic organic chemical raw material. Ethylene cracking gas leaving the cracking furnace usually contains a certain volume of acid gas, mainly hydrogen sulfide and carbon dioxide. Hydrogen sulfide can cause poisoning of the catalyst used in the subsequent process of cracking gas, and at the same time cause corrosion of equipment and pipelines; carbon dioxide will condense in the subsequent cryogenic separation process, block the pipeline, and at the same time will continue to enrich in the circulating ethylene, reduce the ethylene partial pressure, and cause the molecular weight of the polymerization product to decrease. Therefore, it is necessary to remove the acid gas in the ethylene cracking gas before entering the separation process.

[0003] In industry, the acid gas in the cracking gas is usually removed by using an alkali washing process or an amine-alkali combined process after three or four stages of compression, and the content of hydrogen sulfide and carbon dioxide in the cracking gas is strictly controlled ≯1 μL / L. Generally speaking, when the acid gas content is ≤0.1%, the alkali washing process is more economical; when the acid gas content is in the range of 0.1% to 0.5%, the use of the amine-alkali combined process can reduce the consumption of alkali; when the acid gas content is ≥0.5%, the raw material needs to be desulfurized. At present, the alkali washing process is mainly used, mainly three-stage alkali washing and one-stage water washing or two-stage alkali washing and one-stage water washing. A large amount of ethylene waste alkali is produced in the alkali washing process. The ethylene waste alkali is a hazardous waste, has strong alkalinity, and usually contains yellow oil. A part of organic sulfur such as sulfides and mercaptans in the waste alkali is often wrapped in the yellow oil, causing the waste alkali to have great toxicity and be accompanied by a foul odor. The ethylene waste alkali is not renewable, and is usually treated by using a wet oxidation technology, which has high energy consumption, and the essence is to exchange water quality with energy consumption. With the continuous increase of ethylene production capacity, the problem of source reduction of ethylene waste alkali is also increasingly valued.

[0004] In order to reduce the discharge of waste alkali and improve the acid gas removal efficiency of the alkali washing tower, patent application CN101092576A provides a supergravity alkali washing or amine washing-alkali washing process, but its essence is still the alkali washing process or the amine-alkali combined process: using amine washing as a pretreatment means of alkali washing, and after removing part of the acid gas by amine washing, entering the alkali washing to reduce the consumption of alkali. The amine washing process described in the patent application can only be used as a pretreatment process of the alkali washing process, and cannot completely replace the alkali washing process, and still produces ethylene waste alkali. SUMMARY

[0005] In order to overcome the problems of insufficient depth of amine liquid in removing acid gas, large amount of waste alkali in the alkali washing process, strong toxicity, non-renewability, and difficulty in treatment, the present application provides a method and system for removing acid gas from ethylene cracking gas, which is specifically a method for removing acid gas from ethylene cracking gas by using a supergravity amine washing process.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] The present application provides a method for removing acid gas from ethylene cracking gas, which comprises: ethylene cracking gas containing acid gas sequentially passing through a first supergravity amine washing, a second supergravity amine washing and water washing.

[0008] The first supergravity amine washing adopts a first compounded amine solution, and the second supergravity amine washing adopts a second compounded amine solution.

[0009] The first compounded amine solution and the second compounded amine solution independently comprise two or more of triethanolamine, methyldiethanolamine, N-tert-butyl diethanolamine, N-methyl tert-butyl aminoethoxy ethanol, tert-butyl amino hexyloxy hexanol, tert-butyl amino ethanol, diethanolamine, diglycolamine, methylethanolamine, N-tert-butyl ethanolamine and ethanolamine.

[0010] At least one tertiary amine is contained.

[0011] For example, the compounded amine solution is compounded by methyldiethanolamine, N-tert-butyl diethanolamine and diethanolamine; or compounded by methyldiethanolamine, N-tert-butyl diethanolamine, diglycolamine and N-tert-butyl ethanolamine; or compounded by methyldiethanolamine, methylethanolamine and ethanolamine; or compounded by methyldiethanolamine, N-tert-butyl diethanolamine and diethanolamine.

[0012] According to the method of the present application, preferably, the first compounded amine solution and the second compounded amine solution after absorbing acid gas are respectively recycled after regeneration.

[0013] According to the method of the present application, preferably, the first compounded amine solution comprises at least one tertiary amine, one secondary amine and one primary amine. More preferably, the molar ratio of the tertiary amine to the secondary amine is 0.1-10:1, and the molar ratio of the secondary amine to the primary amine is 0.5-10:1.

[0014] According to the method of the present application, preferably, the second compounded amine solution comprises at least one tertiary amine, one secondary amine and one primary amine. More preferably, the molar ratio of the tertiary amine to the secondary amine is 0.1-10:1, and the molar ratio of the secondary amine to the primary amine is 0.5-10:1.

[0015] Compared with primary amine and secondary amine, tertiary amine has higher stability, but because there is no hydrogen atom on the nitrogen atom, it cannot directly react with carbon dioxide, resulting in a lower carbon dioxide absorption rate. Primary amine and secondary amine can directly react with carbon dioxide because there is a hydrogen atom on the nitrogen atom, which can improve the carbon dioxide absorption rate. Therefore, the use of the compounded amine solution can enhance the carbon dioxide absorption rate of the amine solution while maintaining a high carbon capacity, thereby improving the carbon dioxide removal efficiency.

[0016] According to the method of the present application, preferably, the total amine concentration in each of the first compounded amine solution and / or the second compounded amine solution is 5% to 80%; more preferably, 15% to 35%. Unless otherwise specified, the percentages (concentration, content, etc.) in the present application are mass percentages.

[0017] In the method of the present application, the composition and total amine concentration of the first compounded amine solution and the second compounded amine solution can be the same or different.

[0018] According to the method of the present application, preferably, the specific process of the first high-gravity amine washing and the second high-gravity amine washing comprises:

[0019] The ethylene cracking gas containing sour gas and the first compounded amine solution enter the first high-gravity reactor through the gas phase inlet and the liquid phase inlet, respectively; the gas phase and the liquid phase are in intense contact inside the stator and the rotor, and after the removal of the sour gas, the gas phase and the liquid phase are output from the gas phase outlet and the liquid phase outlet of the first high-gravity reactor, respectively, the gas phase goes to the second high-gravity reactor, and the liquid phase is recycled as the first compounded amine solution after regeneration;

[0020] The gas phase from the first high-gravity reactor and the second compounded amine solution enter the second high-gravity reactor through the gas phase inlet and the liquid phase inlet, respectively; the gas phase and the liquid phase are in intense contact inside the stator and the rotor, and after the removal of the remaining sour gas, the gas phase and the liquid phase are output from the gas phase outlet and the liquid phase outlet of the second high-gravity reactor, respectively, the gas phase goes to the water washing unit, and the liquid phase is recycled as the second compounded amine solution after regeneration.

[0021] According to the method of the present application, preferably, the rotational speed of each of the first high-gravity reactor and / or the second high-gravity reactor is 100 rpm to 1400 rpm; more preferably, 600 rpm to 800 rpm.

[0022] According to the method of the present application, preferably, the volume ratio of the gas phase to the liquid phase in each of the first high-gravity reactor and / or the second high-gravity reactor is 100 to 500:1, more preferably, 100 to 200:1; the gas phase pressure is 0.5 to 2.5 MPa(G), more preferably, 0.5 to 2.0 MPa(G).

[0023] According to the method of the present application, preferably, the rotational speed of each of the first high-gravity reactor and / or the second high-gravity reactor is 600 rpm to 800 rpm;

[0024] The volume ratio of the gas phase to the liquid phase in each of the first high-gravity reactor and / or the second high-gravity reactor is 100 to 200:1; the gas phase pressure is 0.5 to 2.0 MPa(G).

[0025] According to the method of the present application, preferably, the ethylene cracking gas containing acid gas is derived from after the third or fourth compressor, wherein the hydrogen sulfide content is ≤ 1500 μL / L, the carbon dioxide content is ≤ 1500 μL / L, preferably, derived from after the third compressor, the hydrogen sulfide content is ≤ 1000 μL / L, the carbon dioxide content is ≤ 1000 μL / L.

[0026] According to the method of the present application, preferably, the hydrogen sulfide and carbon dioxide content in the ethylene cracking gas after the second supergravity amine washing is ≤ 1 μL / L respectively.

[0027] Another aspect of the present application provides a system for removing acid gas in ethylene cracking gas to complete the above method, which comprises a first supergravity reactor, a second supergravity reactor and a water washing unit.

[0028] The present application utilizes the supergravity technology and the combined amine liquid to strengthen the amine washing process to remove the acid gas in the ethylene cracking gas, and realizes the effect that the hydrogen sulfide and carbon dioxide concentration in the ethylene cracking gas after the two-stage amine washing is ≤ 1 μL / L respectively.

[0029] The method of the present application has the following advantages:

[0030] Compared with the existing ethylene cracking gas deacidification process, the method of the present application greatly improves the depth of the amine washing process to remove the acid gas, improves the utilization rate of the amine liquid, and reduces the energy consumption required for regeneration. The method of the present application does not need the alkali washing process, realizes the source reduction of the ethylene waste alkali liquid, and reduces the three-waste emissions of the device. The method of the present application has a simple process, less equipment occupation, and lower energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram of the system and process for removing acid gas in ethylene cracking gas in the preferred scheme of the present application.

[0032] Explanation of reference signs:

[0033] 1. A first supergravity reactor;

[0034] 2. A second supergravity reactor;

[0035] 3. A water washing unit;

[0036] 4. An amine liquid regeneration unit. DETAILED DESCRIPTION

[0037] In order to more clearly illustrate the present application, the present application will be further described below in combination with the preferred embodiments. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.

[0038] All numerical designations (e.g., temperatures, times, concentrations, and weights, etc., including ranges for each thereof) herein can be approximations, typically being changed by increments of 0.1 or 1.0 (+) or (-) as appropriate. All numerical designations are to be understood as being preceded by the term "about."

[0039] As shown in Figure 1 The present application provides a preferred embodiment of a system for removing acid gas from ethylene cracking gas, which comprises a first high gravity reactor 1, a second high gravity reactor 2, and a water washing unit 3; the first high gravity reactor 1 and the second high gravity reactor 2 are each equipped with an amine liquid regeneration unit 4.

[0040] The ethylene cracking gas containing acid gas and the first compounded amine liquid are respectively introduced into the gas phase inlet and the liquid phase inlet of the first high gravity reactor 1; the gas phase and the liquid phase are in intense contact inside the stator and the rotor, and the removal of acid gas is completed; the gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the first high gravity reactor 1, the gas phase goes to the second high gravity reactor 2, and the liquid phase is regenerated by the amine liquid regeneration unit 4 and then recycled as the first compounded amine liquid;

[0041] The gas phase from the first high gravity reactor 1 and the second compounded amine liquid are respectively introduced into the gas phase inlet and the liquid phase inlet of the second high gravity reactor 2; the gas phase and the liquid phase are in intense contact inside the stator and the rotor, and the removal of residual acid gas is completed; the gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the second high gravity reactor 2, the gas phase goes to the water washing unit 3, and the liquid phase is regenerated by the amine liquid regeneration unit 4 and then recycled as the second compounded amine liquid.

[0042] Example 1

[0043] This example uses Figure 1 The system process and the compounded amine liquid are used to treat the following ethylene cracking gas containing acid gas. The pressure of the ethylene cracking gas containing acid gas is 1.0 MPa (G); the first and second compounded amine liquids are each composed of methyldiethanolamine (content of 30%), N-tert-butyl diethanolamine (content of 5%), diethanolamine (content of 10%), ethanolamine (content of 5%), and water, and the total amine concentration is 50%; the rotation speed of the first and second high gravity reactors is 800 rpm, and the volume ratio of the gas phase to the liquid phase is 150:1.

[0044] The ethylene cracking gas containing acid gas and the primary compounded amine solution are respectively introduced into the interior of the primary high gravity reactor through the gas phase inlet and the liquid phase inlet, and the two phases are subjected to a violent mass transfer process under the shearing and crushing of the stator and the rotor, so that the removal of the acid gas in the ethylene cracking gas is completed. Then the ethylene cracking gas and the primary compounded amine solution are respectively discharged from the gas phase outlet and the liquid phase outlet of the primary high gravity reactor. The primary compounded amine solution is sent to the amine solution regeneration unit 4 for regeneration, and the ethylene cracking gas is introduced into the secondary high gravity reactor 2 to contact with the secondary compounded amine solution for the removal of acid gas.

[0045] The ethylene cracking gas and the secondary compounded amine solution from the primary high gravity reactor 1 are respectively introduced into the secondary high gravity reactor 2 through the gas phase inlet and the liquid phase inlet. The gas phase and the liquid phase are subjected to a violent contact in the interior of the stator and the rotor, so that the removal of the remaining acid gas is completed. The gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the secondary high gravity reactor 2, and the gas phase is sent to the water washing unit 3, and the liquid phase is regenerated by the amine solution regeneration unit 4 and then recycled as the secondary compounded amine solution.

[0046] The specific effects of the ethylene cracking gas sequentially passing through the two high gravity reactors are shown in Table 1 as follows:

[0047] Table 1 Concentrations of hydrogen sulfide and carbon dioxide in ethylene cracking gas

[0048]

[0049] Example 2

[0050] This example uses Figure 1 The system process and the compounded amine solution are used to treat the following ethylene cracking gas containing acid gas. The pressure of the ethylene cracking gas containing acid gas is 2.03 MPa (G); the primary and secondary compounded amine solutions are both composed of methyldiethanolamine (content of 15%), N-tert-butyl diethanolamine (content of 5%), N-tert-butyl ethanolamine (content of 5%), diglycolamine (5%) and water, and the total amine concentration is 30%; the rotation speeds of the primary and secondary high gravity reactors are both 600 rpm, and the volume ratios of the gas phase to the liquid phase are both 250:1.

[0051] The ethylene cracking gas containing acid gas and the primary compounded amine solution are respectively introduced into the interior of the primary high gravity reactor through the gas phase inlet and the liquid phase inlet, and the two phases are subjected to a violent mass transfer process under the shearing and crushing of the stator and the rotor, so that the removal of the acid gas in the ethylene cracking gas is completed. Then the ethylene cracking gas and the primary compounded amine solution are respectively discharged from the gas phase outlet and the liquid phase outlet of the primary high gravity reactor. The primary compounded amine solution is sent to the amine solution regeneration unit 4 for regeneration, and the ethylene cracking gas is introduced into the secondary high gravity reactor 2 to contact with the secondary compounded amine solution for the removal of acid gas.

[0052] The ethylene cracking gas from the first high gravity reactor 1 and the second compounded amine liquid respectively enter through the gas phase inlet and the liquid phase inlet of the second high gravity reactor 2; the gas phase and the liquid phase have a violent contact inside the stator and the rotor, and the removal of the remaining acid gas is completed; the gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the second high gravity reactor 2, the gas phase goes to the water washing unit 3, and the liquid phase is regenerated by the amine liquid regeneration unit 4 and then recycled as the second compounded amine liquid.

[0053] The specific effects of the ethylene cracking gas sequentially passing through the two high gravity reactors are shown in Table 2 as follows:

[0054] Table 2 Concentrations of hydrogen sulfide and carbon dioxide in the ethylene cracking gas

[0055]

[0056] Example 3

[0057] This example uses Figure 1 The system process and the compounded amine liquid treat the following ethylene cracking gas containing acid gas. The pressure of the ethylene cracking gas containing acid gas is 1.55 MPa (G); the first and the second compounded amine liquids are both composed of methyldiethanolamine (content of 10%), methylethanolamine (content of 4%), ethanolamine (content of 1%) and water, and the total amine concentration is 15%; the rotation speeds of the first and the second high gravity reactors are both 1200 rpm, and the volume ratios of the gas phase to the liquid phase are both 450:1.

[0058] The ethylene cracking gas containing acid gas and the first compounded amine liquid respectively enter the reactor interior through the gas phase inlet and the liquid phase inlet of the first high gravity reactor, and under the shearing and crushing of the stator and the rotor, the two phases have a violent mass transfer process, and the removal of the acid gas in the ethylene cracking gas is completed; then the ethylene cracking gas and the compounded amine liquid respectively leave the reactor through the gas phase and the liquid phase outlet of the first high gravity reactor. The first compounded amine liquid is sent to the amine liquid regeneration unit 4 for regeneration, and the ethylene cracking gas enters the second high gravity reactor 2 to contact the second compounded amine liquid for the removal of acid gas.

[0059] The ethylene cracking gas from the first high gravity reactor 1 and the second compounded amine liquid respectively enter through the gas phase inlet and the liquid phase inlet of the second high gravity reactor 2; the gas phase and the liquid phase have a violent contact inside the stator and the rotor, and the removal of the remaining acid gas is completed; the gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the second high gravity reactor 2, the gas phase goes to the water washing unit 3, and the liquid phase is regenerated by the amine liquid regeneration unit 4 and then recycled as the second compounded amine liquid.

[0060] The specific effects of the ethylene cracking gas sequentially passing through the two high gravity reactors are shown in Table 3 as follows:

[0061] Table 3 Concentration of hydrogen sulfide and carbon dioxide in ethylene cracking gas

[0062]

[0063] From the results shown in Tables 1 to 3, it can be seen that under the conditions described in the examples of the present application, the combination of the high gravity reactor and the compounded amine solution can well meet the requirements for removal of hydrogen sulfide and carbon dioxide from ethylene cracking gas.

[0064] Example 4

[0065] In this example, a two-stage high gravity reactor in series is used as the place for removal of hydrogen sulfide and carbon dioxide, and two-stage amine washing or two-stage caustic washing is carried out using compounded amine solution or caustic solution as the absorbent to treat the following ethylene cracking gas containing acid gas. The pressure of the ethylene cracking gas containing acid gas is 1.0 MPa (G); the rotational speed of the high gravity reactor is 1000 rpm, and the volume ratio of the gas phase to the liquid phase is 200:1.

[0066] The ethylene cracking gas containing acid gas enters the reactor through the gas phase inlet of the high gravity reactor, and the absorbent enters the reactor through the liquid phase inlet of the high gravity reactor. Under the shearing and crushing of the stator and the rotor, the two phases undergo a violent mass transfer process, and the removal of acid gas from the ethylene cracking gas is completed; thereafter, the ethylene cracking gas and the absorbent leave the reactor through the gas phase and liquid phase outlets of the reactor, respectively.

[0067] When the absorbent is compounded amine solution, the compounded amine solution is composed of methyldiethanolamine (content 6%), N-tert-butyl diethanolamine (content 1%), diethanolamine (content 2%), ethanolamine (content 1%) and water, and the total amine concentration is 10%. The compounded amine solution leaving the reactor is recycled after regeneration; when the absorbent is caustic solution, the caustic solution is sodium hydroxide solution, and the caustic solution concentration is 10%. In order to ensure the free alkali concentration in the caustic solution, a certain amount of old caustic solution leaving the reactor needs to be discharged, and the same amount of fresh caustic solution needs to be supplemented.

[0068] The specific effects of this example are shown in Table 4, wherein the outlet limited concentration in the table is the concentration that the cracking gas must reach at the outlet whether it is amine washing or caustic washing:

[0069] Table 4 Discharge amount of compounded amine solution and caustic solution under the same removal depth

[0070]

[0071] From the results shown in Table 4, in order to reach the outlet limited concentration shown in the table, when using the compounded amine solution as the absorbent, the amine solution needs to be regenerated and recycled continuously, because the regeneration is relatively complete, there is no need to replace the compounded amine solution, and therefore there is no waste liquid discharge; when using the alkali solution as the absorbent, because the acidic gas continuously reacts with the alkali solution to consume the effective component sodium hydroxide in the alkali solution, the effect of removing the acidic gas by the alkali solution decreases, in the case that the alkali solution cannot be regenerated, in order to meet the removal depth, the alkali solution needs to be replaced to maintain a certain concentration, and in the replacement process, waste liquid is discharged.

[0072] Comparative Example 1

[0073] The present comparative example uses Figure 1 The system process and single amine solution are used to treat the ethylene cracking gas containing acidic gas. The pressure of the ethylene cracking gas containing acidic gas is 1.0 MPa (G); the amine solution used in the first stage and the second stage both consists of methyldiethanolamine, and the total amine concentration is 50%; the rotation speed of the supergravity reactor in the first stage and the second stage is 800 rpm, and the volume ratio of the gas phase to the liquid phase is 150:1.

[0074] The ethylene cracking gas containing acidic gas and the first-stage amine solution enter the inside of the first-stage supergravity reactor through the gas phase inlet and the liquid phase inlet of the first-stage supergravity reactor respectively, and under the shearing and crushing of the stator and the rotor, the two phases undergo a violent mass transfer process to complete the removal of the acidic gas in the ethylene cracking gas; then the ethylene cracking gas and the compounded amine solution exit the reactor through the gas phase outlet and the liquid phase outlet of the first-stage supergravity reactor respectively. The first-stage amine solution is sent to the amine regeneration unit 4 for regeneration, and the ethylene cracking gas enters the second-stage supergravity reactor 2 to contact the second-stage amine solution for the removal of acidic gas.

[0075] The ethylene cracking gas from the first-stage supergravity reactor 1 and the second-stage amine solution enter the second-stage supergravity reactor 2 through the gas phase inlet and the liquid phase inlet of the second-stage supergravity reactor 2 respectively; the gas phase and the liquid phase undergo violent contact in the inside of the stator and the rotor to complete the removal of the remaining acidic gas; the gas phase and the liquid phase are output from the gas phase outlet and the liquid phase outlet of the second-stage supergravity reactor 2 respectively, the gas phase goes to the water washing unit 3, and the liquid phase is regenerated after passing through the amine regeneration unit 4 and then is used as the second-stage amine solution for recycling.

[0076] The specific effects of the ethylene cracking gas sequentially passing through the two-stage supergravity reactors are shown in Table 5:

[0077] Table 5 Concentration of hydrogen sulfide and carbon dioxide in ethylene cracking gas

[0078]

[0079] As shown in Table 5, using a single amine solution as the absorbent cannot achieve the effect of removing hydrogen sulfide and carbon dioxide to below 1 μL / L. A comparison with Example 1 shows that using a compound amine solution can improve the mass transfer driving force of the acid gas, effectively increasing the removal depth of hydrogen sulfide and carbon dioxide.

[0080] Comparative Example 2

[0081] This comparative example uses an amine scrubbing tower and a compound amine solution to treat the following ethylene cracking gas containing acidic gases. The pressure of the ethylene cracking gas containing acidic gases is 1.0 MPa (G); the compound amine solution consists of methyl diethanolamine (30%), N-tert-butyldiethanolamine (5%), diethanolamine (10%), ethanolamine (5%), and water, with a total amine concentration of 50%; the volume ratio of gas phase to liquid phase in the amine scrubbing tower is 150:1.

[0082] Ethylene cracking gas containing acidic gas and compound amine liquid enter the amine washing tower through the gas phase inlet and liquid phase inlet, respectively. The two phases complete the removal of acidic gas from the ethylene cracking gas inside the packing. Afterward, the ethylene cracking gas and compound amine liquid leave the amine washing tower through the gas phase outlet and liquid phase outlet, respectively.

[0083] The specific effects of ethylene cracked gas passing through the amine scrubbing tower are shown in Table 6 below:

[0084] Table 6 Concentrations of hydrogen sulfide and carbon dioxide in ethylene cracking gas

[0085]

[0086] As shown in Table 6, conventional amine scrubbing towers cannot achieve the effect of removing hydrogen sulfide and carbon dioxide to below 1 μL / L. A comparison with Example 1 shows that, compared to conventional amine scrubbing towers, the use of a centrifugal reactor can effectively enhance the mass transfer process between the gas and liquid phases, thereby increasing the removal depth of hydrogen sulfide and carbon dioxide.

[0087] Comparative Example 3

[0088] This comparative example uses Figure 1 The system process and compound amine solution are used to treat ethylene cracking gas containing acidic gases. The pressure of the ethylene cracking gas containing acidic gases is 1.0 MPa(G); the compound amine solution consists of methyl diethanolamine (30%), N-tert-butyldiethanolamine (5%), diethanolamine (10%), ethanolamine (5%), and water, with a total amine concentration of 50%; the centrifugal reactor rotates at 800 rpm, and the gas-to-liquid volume ratio is 150:1.

[0089] The ethylene cracking gas containing acid gas and the first-stage compounded amine liquid are respectively introduced into the interior of the first-stage high gravity reactor through the gas phase inlet and the liquid phase inlet of the first-stage high gravity reactor, and the two phases are subjected to a violent mass transfer process under the shearing and crushing of the stator and the rotor to complete the removal of the acid gas in the ethylene cracking gas; then the ethylene cracking gas and the compounded amine liquid are respectively discharged from the gas phase and the liquid phase of the first-stage high gravity reactor. The first-stage compounded amine liquid is sent to the amine liquid regeneration unit 4 for regeneration, and the ethylene cracking gas is introduced into the second-stage high gravity reactor 2 to contact the second-stage compounded amine liquid for the removal of acid gas.

[0090] The ethylene cracking gas from the first-stage high gravity reactor 1 and the second-stage compounded amine liquid are respectively introduced into the second-stage high gravity reactor 2 through the gas phase inlet and the liquid phase inlet; the gas phase and the liquid phase are subjected to a violent contact in the interior of the stator and the rotor to complete the removal of the remaining acid gas; the gas phase and the liquid phase are respectively output from the gas phase outlet and the liquid phase outlet of the second-stage high gravity reactor 2, and the gas phase is sent to the water washing unit 3, and the liquid phase is regenerated by the amine liquid regeneration unit 4 and then recycled as the second-stage compounded amine liquid.

[0091] The specific effects of the ethylene cracking gas sequentially passing through the two-stage high gravity reactors are shown in Table 7:

[0092] Table 7 Concentrations of hydrogen sulfide and carbon dioxide in ethylene cracking gas

[0093]

[0094] As shown in Table 7, when the concentrations of hydrogen sulfide and carbon dioxide in the cracking gas are both more than 1500 μL / L, the method provided by the present application cannot achieve the effect of removing hydrogen sulfide and carbon dioxide to below 1 μL / L. By comparison with Example 1, it can be seen that when the contents of hydrogen sulfide and carbon dioxide in the ethylene cracking gas are too high, the method provided by the present application cannot achieve the effect of removing hydrogen sulfide and carbon dioxide to below 1 μL / L. As shown in the examples and the comparative examples, the method provided by the present application can deeply remove the acid gas in the ethylene cracking gas to achieve the removal effect of hydrogen sulfide and carbon dioxide being ≤1 μL / L.

[0095] Obviously, the above examples of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. On the basis of the above description, those skilled in the art can make other different forms of changes or modifications, and it is impossible to enumerate all the implementation modes here. Any changes or modifications falling within the technical solution of the present application or being obviously derived therefrom are still within the protection scope of the present application.

Claims

1. A method for removing acidic gases from ethylene cracking gas, characterized in that, The method includes: passing ethylene cracked gas containing acid gas sequentially through a first-stage ultragravity amine wash, a second-stage ultragravity amine wash, and a water wash; The first stage of supergravity amine washing uses a first stage of compound amine solution, and the second stage of supergravity amine washing uses a second stage of compound amine solution; The first-stage and second-stage compound amine solutions independently contain two or more of the following: triethanolamine, methyl diethanolamine, N-tert-butyl diethanolamine, N-methyl-tert-butylaminoethoxyethanol, tert-butylaminohexyloxyhexanol, tert-butylaminoethanol, diethanolamine, diethylene glycolamine, methylethanolamine, N-tert-butylethanolamine, and ethanolamine. Both the first-stage and second-stage compound amine solutions contain at least one tertiary amine, one secondary amine, and one primary amine, wherein the molar ratio of the tertiary amine to the secondary amine is 0.1-10:1, and the molar ratio of the secondary amine to the primary amine is 0.5-10:

1. The gas-to-liquid volume ratio in each of the single-stage and / or two-stage supergravity reactors is 100-500:1; the gas phase pressure is 0.5-2.5 MPa(G). The ethylene cracked gas containing acidic gas comes from after a three- or four-stage compressor, wherein the hydrogen sulfide content is ≤1500 μL / L and the carbon dioxide content is ≤1500 μL / L; The hydrogen sulfide and carbon dioxide contents in the ethylene cracking gas after the two-stage supergravity amine wash are both below 1 μL / L.

2. The method for removing acidic gases from ethylene cracking gas according to claim 1, characterized in that, The first and second stages of compound amine solutions, after absorbing acidic gas, are regenerated and recycled.

3. The method for removing acidic gases from ethylene cracking gas according to claim 1, characterized in that, The total amine concentration in each of the first-stage and / or second-stage compound amine solutions is 5% to 80%.

4. The method for removing acidic gases from ethylene cracking gas according to claim 1, characterized in that, The specific processes of the first-stage and second-stage supergravity amine washing include: Ethylene cracking gas containing acidic gas and a first-stage compound amine solution enter through the gas phase inlet and liquid phase inlet of the first-stage supergravity reactor, respectively. The gas phase and liquid phase come into intense contact inside the stator and rotor. After the acidic gas is removed, the gas phase and liquid phase are output from the gas phase outlet and liquid phase outlet of the first-stage supergravity reactor, respectively. The gas phase goes to the second-stage supergravity reactor, and the liquid phase is recycled as the first-stage compound amine solution after regeneration. The gas phase and the second-stage compounded amine solution from the first-stage supergravity reactor enter through the gas phase inlet and liquid phase inlet of the second-stage supergravity reactor, respectively. The gas phase and liquid phase come into intense contact inside the stator and rotor, completing the removal of the remaining acidic gas. The gas phase and liquid phase are output from the gas phase outlet and liquid phase outlet of the second-stage supergravity reactor, respectively. The gas phase goes to the water washing unit, and the liquid phase is recycled as the second-stage compounded amine solution after regeneration.

5. The method for removing acidic gases from ethylene cracking gas according to claim 4, characterized in that, The rotational speed of each of the first-stage and / or second-stage hypergravity reactors is 100 rpm to 1400 rpm.

6. The method for removing acidic gases from ethylene cracking gas according to claim 1, characterized in that, The ethylene cracked gas containing acidic gas comes from after the third stage, with a hydrogen sulfide content ≤1000 μL / L and a carbon dioxide content ≤1000 μL / L.

7. A system for removing acidic gases from ethylene cracking gas, characterized in that, The system is used to perform the method according to any one of claims 1-6, and includes a first-stage hypergravity reactor, a second-stage hypergravity reactor, and a water washing unit.

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