A method for deep desulfurization of coking liquefied gas

Abstract

The application provides a coking liquefied gas deep desulfurization method, which comprises the following steps: regenerating and modifying waste catalytic cracking catalysts, wherein the waste catalytic cracking catalysts are subjected to coking treatment, the catalysts after the coking treatment are mixed and ground with molecular sieves, and the regenerated and modified catalysts are obtained after solidification and molding; coking liquefied gas is contacted with the regenerated and modified catalysts to perform a catalytic thermal cracking reaction, macromolecular sulfides in the coking liquefied gas are thermally cracked into small molecular sulfides; the coking liquefied gas after the catalytic thermal cracking reaction is sequentially subjected to desulfurization hydrogen treatment, desulfurization alcohol treatment, dehydration treatment and desulfurization carbon treatment, and finally, the coking liquefied gas after the desulfurization treatment is obtained. The method can realize the upgraded utilization of the coking liquefied gas and the reuse of the catalyst, reduce the sulfur content in the coking liquefied gas, avoid the loss caused by the deep cracking of the coking liquefied gas, and perform deep desulfurization on the coking liquefied gas.

Description

Technical Field

[0001] The present invention relates to a method for deep desulfurization of coking liquefied gas, in particular to a combined purification method for coking liquefied gas, which also includes the regeneration, modification and application of waste catalytic cracking catalysts. Background Art

[0002] my country's energy structure is rich in coal, poor in oil, and low in natural gas, requiring large quantities of oil to be imported. In recent years, the contradiction between oil supply and demand has become increasingly intensified worldwide. The quality of crude oil processed in my country is becoming increasingly heavier and inferior. Coking, as an important method for upgrading and utilizing inferior oil, is widely used in refining and chemical companies. Coking liquefied gas typically has a high sulfur content and low practical application value, and is mostly used solely as fuel, resulting in a waste of resources. This portion of liquefied gas contains approximately 12-17% propylene by weight, typically containing around 200-300 ppm of carbonyl sulfide, as well as trace amounts of hydrogen sulfide, mercaptans, and macromolecular sulfides. Macromolecular sulfides other than hydrogen sulfide and mercaptans are particularly difficult to remove. If this portion of propylene could be desulfurized and purified for use in a butyl alcohol and octanol unit, the application value of the coking liquefied gas could be greatly enhanced.

[0003] As crude oil processing becomes increasingly heavier and inferior, catalytic cracking has become one of the most important heavy oil processing processes. Catalysts play a crucial role in the catalytic cracking process. Over time, catalysts deactivate due to heavy metal contamination and carbon deposition, leading to decreased catalytic activity and the need for regular catalyst replacement. As my country's crude oil processing volume increases annually, the amount of spent catalyst produced by domestic catalytic cracking units is also increasing. Currently, there are no effective methods or approaches for the treatment and utilization of this large amount of spent catalytic cracking catalyst. The most common treatment method is landfilling as solid waste, which not only wastes significant resources but also, due to the presence of heavy metals in spent catalysts, can potentially pollute the environment if improperly handled. Using regeneration methods to restore or partially restore the activity of spent catalytic cracking catalysts and finding suitable applications for their reuse would not only address the environmental challenges associated with improper waste catalyst disposal but also create higher profits for businesses.

[0004] CN 106365944 B discloses a method for separating coking liquefied gas to produce polymer-grade propylene. Using low-quality coking liquefied gas, a byproduct of heavy oil coking, as raw material, the method involves removing hydrogen sulfide from the coking liquefied gas, removing mercaptans from the coking liquefied gas, rectifying the coking liquefied gas, dehydrating crude propylene, and removing carbonyl sulfide from the crude propylene to produce a propylene product. During the rectification process, carbonyl sulfide and propylene have similar boiling points and cannot be removed by conventional distillation. The present invention removes carbonyl sulfide in a carbonyl sulfide hydrolysis tank to produce a polymer-grade propylene product. Dehydration is achieved by operating a coalescing dehydrator and a caustic soda dehydration tank in series, strictly controlling the residual moisture in the propylene product and significantly increasing the application value of the coking liquefied gas. However, the invention utilizes conventional desulfurization methods, which can only remove hydrogen sulfide and mercaptans, but cannot remove macromolecular sulfides.

[0005] CN 107201254 B discloses a method for refining mixed liquefied petroleum gas. The invention provides a refining method in which coking liquefied petroleum gas is introduced into a riser reactor of a catalytic cracking unit to undergo a cracking reaction along with the catalytic cracking feed. The mixed liquefied petroleum gas is then distilled from the fractionation system of the catalytic cracking unit to form a mixture of catalytic liquefied petroleum gas and catalytic liquefied petroleum gas. The mixed liquefied petroleum gas is then fed into a hydrogen sulfide extraction unit and a mercaptan extraction unit to remove hydrogen sulfide and mercaptans, respectively. The sulfur content of the desulfurized liquefied petroleum gas product is no more than 10 μg / g. Due to the high activity of the catalytic cracking catalyst, this process not only cracks large molecular sulfides into small molecular sulfides, but also cracks the coking liquefied gas to a certain extent, and even undergoes some deep cracking to produce carbon deposits. This results in a high loss rate of the coking liquefied gas, which in turn causes certain economic losses during the processing.

[0006] CN 113797981 A provides a method for revitalizing a spent catalytic cracking catalyst, comprising: calcining a spent catalytic cracking catalyst containing contaminated metals; alkali leaching the calcined product in an alkaline solution containing a structural protective agent; and sequentially washing the alkali-leached product with water and acid to obtain a revitalized catalytic cracking catalyst. The structural protective agent is selected from one or more of water glass, silica sol, sodium metaaluminate, and molecular sieve mother liquor, and the contaminated metals include vanadium. The revitalized catalytic cracking catalyst can have a 1%-10% higher crystallinity, a 50%-80% vanadium removal rate, and a 10-15% higher micro-reaction activity than a spent catalyst cracking balance agent. The resulting catalyst maintains good activity stability after multiple regeneration cycles.

[0007] CN 110102310 A discloses a method for preparing a tar lightening catalyst based on waste FCC catalyst, which is to use waste FCC catalyst as active metal source, put the waste FCC catalyst in mixed acid of nitric acid and hydrofluoric acid for high temperature digestion to obtain a digestion solution containing active metal, impregnate the digestion solution with carbon material to obtain a precursor, and then calcine the precursor under the mixed gas atmosphere of CO2 and / or H2O and inert gas at 650-800 DEG C to prepare a high-activity tar lightening catalyst. The tar lightening catalyst can further catalytically crack the polycyclic aromatic hydrocarbons and oxygen-containing heterocyclic compounds in the tar formed by pyrolysis of coal, biomass and other carbon-containing substances into light aromatic hydrocarbons such as benzene and toluene, so as to catalytically modify the tar and improve the quality of the tar. The purpose of the invention is to utilize the active metal components in the waste FCC catalyst, but the carrier structure of the FCC catalyst is not further recycled. SUMMARY

[0008] In order to realize the upgrading utilization of coking liquefied gas and the recycling of catalyst, reduce the sulfur content in coking liquefied gas, and avoid the loss caused by deep cracking of coking liquefied gas, the present application provides a method for deep desulfurization of coking liquefied gas, which comprises the steps of regenerating and modifying waste FCC catalyst, converting the difficult-to-remove macromolecular sulfides into small molecular sulfides by catalytic thermal cracking using the regenerated FCC catalyst, and then performing deep desulfurization of coking liquefied gas by using the processes of conventional carbonyl sulfur hydrolysis, alcohol amine extraction, alcohol amine desorption, alkali extraction, and alkali regeneration.

[0009] The method for deep desulfurization of coking liquefied gas provided by the present application comprises the following steps:

[0010] a. Regenerating and modifying the waste FCC catalyst, which comprises the steps of coke-burning treatment of the waste FCC catalyst, mixing and grinding the coke-burning treated catalyst with molecular sieve, and obtaining the regenerated and modified catalyst after solidification and molding;

[0011] b. Contacting the coking liquefied gas with the regenerated and modified catalyst to perform catalytic thermal cracking reaction, and thermally cracking the macromolecular sulfides in the coking liquefied gas into small molecular sulfides;

[0012] c. Performing desulfurization, demercaptanization, dehydration, and decarbonyl sulfur treatment on the coking liquefied gas after the catalytic thermal cracking reaction in sequence, and finally obtaining the desulfurized coking liquefied gas.

[0013] In the above technical solution, the regeneration and modification treatment of the waste FCC catalyst in step a comprises the following steps:

[0014] Burning process of spent catalytic cracking catalyst. In order to better achieve burning and remove the organic matter that may remain in the catalyst pores, this step includes two burning processes, namely the first burning and the second burning, in which:

[0015] The reaction conditions of the first charring process are: slightly positive pressure, riser reactor inlet temperature 450-590℃, nitrogen space velocity 800-1500h -1 , air speed 60-150h -1 , charring time 2-6h. Preferably, the reactor inlet temperature is 480-580℃, the nitrogen space velocity is 950-1200h -1 , air speed 75-120h -1 , scorching time 3-5h.

[0016] The reaction conditions of the second charring process are: slightly positive pressure, reactor inlet temperature 499-606℃, nitrogen space velocity 800-1500h -1 , air speed 200-650h -1 , charring time 3-9h. Preferably, the reactor inlet temperature is 510-580℃, the nitrogen space velocity is 950-1200h -1 , air speed 300-600h -1 , scorching time 4-8h.

[0017] It should be further explained here that the two coking processes require the control of different coking conditions, such as temperature, nitrogen, and air flow. In the first coking process, the carbon deposits on the spent catalytic cracking catalyst and the amount of organic matter that may remain in the catalyst pores are large, and relatively mild conditions need to be controlled. Controlling the coking process may generate a large amount of reaction heat, preventing the molecular sieve's specific surface area, pore volume, pore size and other physical parameters from undergoing large changes, thereby affecting the subsequent catalytic performance of the catalyst. The purpose of the second coking process is to completely react the carbon deposits remaining in the first coking process with the organic matter in the catalyst pores. Since the first coking process has already dealt with most of the carbon deposits and organic matter, the temperature and oxygen content of the second coking process can be appropriately increased compared to the first coking process.

[0018] 2. Preparation of CuY molecular sieve: First, ion exchange the NaY molecular sieve with a 0.2-1 mol / L aqueous nitric acid solution for 2-5 hours. Then, ion exchange the resulting HY molecular sieve with a 0.2-1 mol / L aqueous copper nitrate solution for 3-8 hours. The product is filtered and dried to obtain the CuY molecular sieve.

[0019] CuY molecular sieve is selected in the present invention because of its large adsorption capacity and good adsorption selectivity.

[0020] 3. Modification and regeneration of the catalytic cracking catalyst. The catalytic cracking catalyst after two times of coking and the CuY molecular sieve prepared in step 2 are mixed according to a mass ratio of 3-7:1, deionized water or ethanol is added to stir to prepare a slurry, and then the slurry is sent to a grinding machine to grind to a solid particle size of less than 3 μm. The mass amount of the deionized water or ethanol is 15-35% of the mass of the catalytic cracking catalyst, the stirring time for preparing the slurry is 30-70 min, the rotating speed is 100-300 r·min-1, the rotating speed during grinding is 200-400 r·min-1, and the grinding time is 40-120 min. -1 -1

[0021] The obtained slurry is sprayed and dried in a spray dryer at 650-800 ℃ for 2-6 h, and then solidified at 550-750 ℃ for 2-6 h. Further, the solidification temperature is preferably 550-630 ℃, and the time is 3-5 h. After solidification, 60-70 wt% of the obtained catalyst has a particle size in the range of 30-95 μm. Since the reaction occurs in a fluidized bed reactor, too small particle size can easily block the pipeline, and too large particle size can cause poor fluidization performance, thereby affecting the reaction performance, so the particle size of the catalyst needs to be appropriate.

[0022] After the above steps, the modified and regenerated catalytic cracking catalyst is obtained. The catalyst has both cracking and adsorption functions, has moderate acidity, and has good sulfide adsorption function. The subsequent cracking reaction process can be carried out at a lower reaction temperature, which not only achieves the goal of reducing the sulfur content in the coking liquefied gas, but also avoids the loss caused by deep cracking of the coking liquefied gas. The catalyst modification and regeneration method is simple, the raw materials used are all commercially available products, and is suitable for large-scale industrial production, thereby providing a feasible scheme for upgrading and utilization of the coking liquefied gas.

[0023] The catalytic cracking thermal cracking test is completed on a RU-II type continuous riser catalytic cracking evaluation test device. The regenerated catalyst reaches the bottom of the reactor through the regeneration device and the retransport line, the coking liquefied gas after pre-lifting and preheating enters the riser reactor to contact the catalyst for cracking reaction, the reactants and the catalyst are lifted to the separator, and then enter the post-fractionation system from the top of the settler after settling and filtering. The carbonized catalyst falls into the stripper and is stripped by steam, and then is transported to the top of the regenerator through the standby transport line. In the regenerator, the carbonized catalyst is regenerated by air coking. The regenerated catalyst flows into the regenerated catalyst transport line. The circulation amount of the catalyst is controlled by the opening degree of the standby slide valve and the regeneration slide valve. The cracking gas is metered by a dry gas meter.

[0024] ​​The above cracking is carried out at 350-420℃, and a regenerated and modified catalytic cracking catalyst is used for the catalytic thermal cracking test, so that the relatively large molecular sulfides difficult to remove are thermally cracked into relatively small molecular sulfides easy to remove, and part of the sulfides are adsorbed, thereby reducing the loss of coking propylene to the maximum extent.

[0025] The process for removing sulfides from the coking liquefied gas after the catalytic thermal cracking reaction includes the following steps:

[0026] (1) Coking liquefied gas desulfurization: the coking liquefied gas after the catalytic thermal cracking reaction enters a hydrogen sulfide extraction unit and is subjected to alcohol amine extraction to remove hydrogen sulfide. In the coking liquefied gas desulfurization tower, the coking liquefied gas flows from bottom to top, and the desulfurizing agent flows from top to bottom. The hydrogen sulfide in the coking liquefied gas is absorbed by the desulfurizing agent and then discharged from the bottom of the tower. The coking liquefied gas after the removal of hydrogen sulfide is discharged from the top of the tower.

[0027] (2) Coking liquefied gas desulfurization: the coking liquefied gas after the removal of hydrogen sulfide enters an alkali washing fiber membrane desulfurization tank, and a traditional alkali washing fiber membrane contact method is used to remove mercaptans in the coking liquefied gas.

[0028] (3) Coking liquefied gas dehydration: the coking liquefied gas is first subjected to preliminary dehydration in a coalescence dehydration tank, and then further dehydrated in a flake alkali dehydration tower, so that the water content in the coking liquefied gas is reduced to less than 10 ppm.

[0029] (4) Coking liquefied gas decarbonyl sulfide: the coking liquefied gas after dehydration enters a hydrolysis decarbonyl sulfide tank. The hydrolysis decarbonyl sulfide tank uses a self-made carbonyl sulfide hydrolysis catalyst. The carbonyl sulfide hydrolysis catalyst has a unique core-shell structure. The inner core is a 2mm small ball, and the shell is a 1mm coating. The composition of the inner core includes a carrier and an active component, wherein the carrier includes alumina, silica, and titanium oxide, and the main active component includes potassium oxide, gallium oxide, and lanthanum oxide. The shell is a C and N doped compound, which includes zinc oxide, aluminum oxide, and silicon dioxide.

[0030] The decarbonyl sulfide reaction process is as follows: the coking liquefied gas penetrates through the catalyst shell, diffuses to the inner core, and undergoes a COS hydrolysis reaction. The further generated H2S diffuses to the shell, where H2S is captured, thereby completing a complete sulfide (carbonyl sulfide + hydrogen sulfide) removal process. The self-made carbonyl sulfide hydrolysis catalyst can simultaneously achieve carbonyl sulfide hydrolysis and capture and removal of hydrogen sulfide after hydrolysis. The existing carbonyl sulfide hydrolysis catalyst can only achieve carbonyl sulfide hydrolysis.

[0031] In the preparation process of the self-made carbonyl sulfide hydrolysis catalyst, two processes of inner core preparation and shell preparation are included.

[0032] During the core preparation process, titanium oxide and active components are introduced in the form of precursors, wherein the titanium oxide precursor is metatitanic acid, and the precursors of potassium oxide, gallium oxide, and lanthanum oxide are added in the form of potassium nitrate, gallium nitrate, and lanthanum nitrate, respectively.

[0033] The amount of titanium oxide precursor and active component precursor is calculated based on the weight of the oxides. According to the calculation principle, the weight of the molecular sieve and oxide required for the preparation of the inner core is: 52-80 parts of molecular sieve, 20-35 parts of titanium oxide, 3-7 parts of potassium oxide, 1-3 parts of gallium oxide, and 2-4 parts of lanthanum oxide.

[0034] The molecular sieve is any one or more of HY, HMCM-22, and HZSM-5. The above molecular sieves are selected because HY, HMCM-22, and HZSM-5 molecular sieves have relatively weak acidity and can be used to adjust the overall acidity of the carbonyl sulfide hydrolysis catalyst, thereby achieving a synergistic catalytic effect with the metal components in the carbonyl sulfide hydrolysis catalyst.

[0035] Specifically, the catalyst core preparation process includes the following steps:

[0036] Step b1: uniformly mix the molecular sieve, titanium oxide precursor, and additive to form a solid material.

[0037] Step b2: Add the binder into water and stir evenly to form solution A.

[0038] Step b3, rolling balls: Place the solid material in a rolling ball machine, spray solution A onto the material in the rolling ball machine, rotate the rolling ball machine to form small balls with a diameter of about 2 mm, and screen the spherical particles to obtain a spherical carrier with a diameter of 2 mm.

[0039] Step b4, impregnation: The precursors of the active components potassium oxide, gallium oxide, and lanthanum oxide are dissolved in water to prepare solution B, and the support is added to solution B and impregnated for 3-6 hours.

[0040] Step b5, drying: drying the impregnated carrier at a temperature of 100-130° C. for 1-4 hours.

[0041] Step b6, calcination: calcine the dried carrier at a temperature of 300-600° C. for 3-5 hours to obtain the core of the carbonyl sulfide hydrolysis catalyst.

[0042] In the above step b1, in order to achieve better mixing and binder effects, the auxiliary agent is one of sesbania powder, polyvinyl alcohol, and polyacrylamide; the binder is any one of acetic acid, nitric acid, or citric acid, preferably nitric acid.

[0043] Specifically, the preparation process of the catalyst shell includes the following steps:

[0044] Step c1, dispersing the molecular sieve in a solvent to form a suspension I; based on the inventors' extensive previous practical experience, for example, when selecting the molecular sieve used in the catalyst shell, it is required to have certain shape selectivity, so the molecular sieve used is any one or more of HZSM-23, HBEA or HMOR; the solvent used includes any one or a combination of methanol, water or N,N-dimethylformamide; the ratio of the mass of the molecular sieve to the volume of the solvent is 1:10-1:50, more preferably 1:20-1:30.

[0045] Step c2: adding a zinc source to the suspension I and stirring to obtain a suspension II; wherein the zinc source is zinc nitrate.

[0046] Step c3, adding a heterocyclic organic compound containing C and N elements to the suspension II and stirring to obtain a suspension of the complex; wherein, in order to enable the catalyst to better adsorb sulfides, C and N elements need to be introduced. The present invention uses a heterocyclic organic compound containing C and N as a source of C and N elements. After a large amount of practical summary, the heterocyclic organic compound containing C and N elements used in the present invention includes one or a combination of 2-methylimidazole, imidazole, pyridine, benzopyridine, etc.

[0047] Step c4: Add the catalyst core obtained above into a sugar coating machine and coat it with the suspension of the complex obtained in step c3, controlling the coating thickness to be about 1 mm.

[0048] The pellets coated in step c5 and step c4 are dried at 100-130° C. for 1-4 hours; after drying, they are calcined at 650-750° C. for 3-5 hours in a nitrogen atmosphere to obtain the coking liquefied gas carbonyl sulfide hydrolysis catalyst of the present invention.

[0049] The molar ratio of the zinc source in step c2 to the heterocyclic organic compound containing C and N elements in step c3 can be controlled to be 1:2-2:2.

[0050] The self-produced carbonyl sulfide hydrolysis catalyst of the present invention can catalyze the carbonyl sulfide hydrolysis reaction while simultaneously removing hydrogen sulfide produced during the hydrolysis process. This disrupts the equilibrium of the COS + H2O = H2S + CO2 reaction, favoring the rightward direction of the hydrolysis reaction and increasing the hydrolysis reaction rate. The catalyst exhibits high activity and good stability. The self-produced catalyst is simple to prepare, and the raw materials used are all commercially available products, making it suitable for large-scale industrial production.

[0051] In the present application, if not otherwise stated, the coking liquefied gas desulfurization, coking liquefied gas desulfurization, coking liquefied gas dehydration, coking liquefied gas decarbonyl sulfur and other processes are carried out in a known manner. It should be noted that the coking liquefied gas decarbonyl sulfur and other processes using a known manner refers to the use of catalysts, not the preparation of catalysts, such as the use of a fixed bed reactor, under general reaction conditions to achieve the process of reaction.

[0052] Further through the coking liquefied gas desulfurization, coking liquefied gas desulfurization, coking liquefied gas dehydration, coking liquefied gas decarbonyl sulfur and other processes, the sulfide content of the desulfurized coking liquefied gas obtained is reduced to less than 5 ppm. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the embodiments of the present disclosure clearer, the technical scheme in the embodiments of the present disclosure will be described clearly and completely below in combination with the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present disclosure.

[0054] Embodiment 1

[0055] The regeneration and modification of the old catalytic cracking catalyst includes the following steps:

[0056] 1. Waste catalytic cracking catalyst coking process, in order to better realize the coking and remove the organic matter that may be left in the pores of the catalyst, this step includes two coking,

[0057] (1) First coking, slightly positive pressure, reactor inlet temperature 550℃, nitrogen space velocity 1000h -1 , air space velocity 110h -1 , coking time 3h.

[0058] (2) Second coking, slightly positive pressure, reactor inlet temperature 560℃, nitrogen space velocity 1200h -1 , air space velocity 300h -1 , coking time 5h.

[0059] 2. Preparation of CuY molecular sieve, first ion exchange 500g NaY molecular sieve with 0.3mol / l nitric acid aqueous solution, exchange time 3h; then the obtained HY molecular sieve is ion exchanged with 0.3mol / l copper nitrate aqueous solution, exchange time 4h, filtration, drying, finally CuY molecular sieve is obtained.

[0060] 3. Modification and regeneration of the catalytic cracking catalyst, the catalytic cracking catalysts after one or two times of coking and the CuY molecular sieve prepared in step 2 are mixed according to a mass ratio of 4:1, deionized water is added for stirring to prepare a slurry, and then the slurry is sent to a grinder for grinding to a solid particle size of less than 3 μm, wherein the mass amount of the deionized water or ethanol is 15% of the mass of the catalytic cracking catalyst, the stirring time for preparing the slurry is 30 min, the rotating speed is 150 r·min-1, and the rotating speed during grinding is 300 r·min-1. -1 -1 The grinding time is 60 min.

[0061] The slurry obtained above is sprayed into a spray dryer, dried at 700 ℃ for 4 h, and then solidified at 550 ℃ for 4 h. After solidification, 60-70 wt% of the obtained catalyst has a particle size of 30-95 μm.

[0062] The catalytic cracking thermal cracking test is completed on a RU-II type continuous riser catalytic cracking evaluation test device. The reaction temperature is 390 ℃, the regenerated catalyst reaches the bottom of the reactor from the regenerator through a regeneration line, certain coking liquid gas from a refinery is pre-lifted and pre-heated to enter the riser reactor to contact the catalyst to occur cracking reaction, the reactants and the catalyst are lifted to a separator, and after sedimentation and filtration, the coking liquid gas enters a post-fraction system from the top of the sedimentation tank. The coked catalyst falls into a stripper and is steam-stripped to be transported to the top of the regenerator through a standby line. In the regenerator, the coked catalyst is regenerated by air coking. The regenerated catalyst flows into a regenerated catalyst transport line. The circulation amount of the catalyst is controlled by the opening degree of the standby slide valve and the regeneration slide valve. The cracking gas is metered by a dry gas meter. After the coking liquid gas is catalytically thermally cracked, the loss rate is about 2%.

[0063] The process for removing sulfides from the coking liquid gas after the catalytic thermal cracking reaction includes the following steps:

[0064] (1) Removal of hydrogen sulfide from the coking liquid gas: the coking liquid gas after the catalytic thermal cracking reaction enters a hydrogen sulfide extraction unit to remove hydrogen sulfide by alcohol amine extraction. In a hydrogen sulfide removal tower for the coking liquid gas, the coking liquid gas flows from bottom to top, and the desulfurizing agent flows from top to bottom. The hydrogen sulfide in the coking liquid gas is absorbed by the desulfurizing agent and then discharged from the bottom of the tower together with the desulfurizing agent. The coking liquid gas after removal of the hydrogen sulfide is discharged from the top of the tower.

[0065] (2) Removal of mercaptans from the coking liquid gas: the coking liquid gas after removal of the hydrogen sulfide enters an alkali washing fiber membrane mercaptan removal tank to remove the mercaptans in the coking liquid gas by using a traditional alkali washing fiber membrane contact method.

[0066] (3) Removal of water from the coking liquid gas: the coking liquid gas is first subjected to preliminary dehydration in a coalescence dehydration tank, and then further dehydrated in a piece of caustic soda dehydration tower to reduce the water content in the coking liquid gas to less than 10 ppm. ​

[0067] (4) Decarburization of coking gas: After dehydration, the coking gas enters a hydrolysis decarburization tank, which uses a self-made carbonyl sulfur hydrolysis catalyst with a unique core-shell structure. The reaction process is as follows: the coking gas penetrates through the catalyst shell, diffuses to the core, and undergoes COS hydrolysis reaction, further producing H2S which diffuses to the shell and captures H2S, thus completing a complete sulfide (carbonyl sulfur + hydrogen sulfide) removal process. Finally, coking gas with a total sulfur of 3 ppm is obtained.

[0068] The preparation method of the self-made carbonyl sulfur hydrolysis catalyst is as follows:

[0069] Preparation of catalyst core: 824 g of HY molecular sieve, 194 g of metatitanic acid, and 25 g of polyvinyl alcohol were weighed and mixed uniformly to form a solid material; 19 g of nitric acid was weighed and added to water and stirred to form a solution; the uniformly mixed solid material was placed in a rolling ball machine, and the solution was sprayed onto the material in the rolling ball machine, and the rolling ball was formed by rotating the rolling ball machine to obtain small balls with a diameter of 2 mm; the small balls were dried at 120°C for 6h and calcined at 400°C for 5h to prepare the catalyst A core carrier.

[0070] A solution was prepared by dissolving 72 g of potassium nitrate, 64 g of gallium nitrate, and 52 g of lanthanum nitrate in water, and the catalyst A core carrier was added to the solution and immersed for 3h; the immersed carrier was dried at 130°C for 4h and calcined at 490°C for 5h to obtain the catalyst A core.

[0071] Catalyst shell coating:

[0072] 6g of HZSM-23 carrier was weighed and dispersed in 124mL of methanol, and after stirring and ultrasonic treatment, a uniform mixture I was obtained; 2g of zinc nitrate hexahydrate was added to mixture I and stirred at 25°C for 30 minutes to ensure complete dissolution, obtaining mixture II; 11g of methyl imidazole was added to mixture II and stirred at 25°C for 3 hours to obtain a complex; the catalyst A core obtained above was added to a sugar coating machine and coated with the above obtained complex, controlling the thickness of the coating to be about 1mm. After coating, the small balls were dried at a temperature of 100°C for 4 hours; after drying, they were calcined at 650°C for 3 hours under nitrogen atmosphere to obtain the carbonyl sulfur hydrolysis catalyst A.

[0073] Example 2

[0074] The regeneration and modification of the waste FCC catalyst includes the following steps:

[0075] 1. Waste FCC catalyst coking process: In order to better achieve coking and remove possible organic residues in the catalyst pores, this step includes two coking processes,

[0076] (1) First charring, slightly positive pressure, reactor inlet temperature 570°C, nitrogen space velocity 1200h -1 , air space velocity 120h -1 , charring time 5h.

[0077] (2) Second charring, slightly positive pressure, reactor inlet temperature 580°C, nitrogen space velocity 1200h -1 , air space velocity 600h -1 , charring time 7h.

[0078] 2. Preparation of CuY molecular sieve, first ion exchange 1000g NaY molecular sieve with 0.7mol / l nitric acid aqueous solution, exchange time 5h; then ion exchange the obtained HY molecular sieve with 0.8mol / l copper nitrate aqueous solution, exchange time 7h, filtration, drying, finally obtain CuY molecular sieve.

[0079] 3. Modification, regeneration type of catalytic cracking catalyst, mix the catalytic cracking catalysts after first and second charring and CuY molecular sieve prepared in step 2 according to mass ratio 5:1, add deionized water to stir to prepare slurry, then send into grinder to grind to solid particle size less than 3μm, wherein the mass amount of deionized water or ethanol is 25% of the mass of catalytic cracking catalyst, the stirring time for preparing slurry is 30min, the rotating speed is 150r.min -1 , the rotating speed during grinding is 300r.min -1 , and the grinding time is 100min.

[0080] The above obtained slurry enters into spray dryer at 800°C to spray dry for 4h, then solidify at 550°C for 4h. The particle size of 60-70wt% of the obtained catalyst after solidification is 30-95μm.

[0081] The catalytic cracking thermal cracking test is completed on RU-II type continuous riser catalytic cracking evaluation test device. The reaction temperature is 390°C, the regenerated catalyst reaches the bottom of the reactor from the regenerator through the re-conveying line, the coking liquid gas of a certain refinery enters the riser reactor to contact the catalyst to occur cracking reaction after pre-lifting and pre-heating, the reactants and catalysts are lifted to the separator, and after sedimentation and filtration, they enter the post-fractionation system from the top of the settler. The carbonized catalyst falls into the stripper and is steam stripped, and then is conveyed to the top of the regenerator through the standby conveying line. In the regenerator, the carbonized catalyst is regenerated by charring with air. The regenerated catalyst flows into the regenerated catalyst conveying line. The circulating amount of the catalyst is controlled by the opening degree of the standby slide valve and the regeneration slide valve. The cracking gas is metered by a dry gas meter. After the coking liquid gas is catalytically thermally cracked, the loss rate is about 3%.

[0082] The process for removing sulfides from the coking liquid gas after catalytic thermal cracking reaction includes the following steps:

[0083] (1) Coking liquefied gas desulfurization hydrogen sulfide: the coking liquefied gas after catalytic thermal cracking reaction enters the hydrogen sulfide extraction unit to remove hydrogen sulfide by alcohol amine extraction. In the coking liquefied gas desulfurization hydrogen sulfide tower, the coking liquefied gas flows from bottom to top, and the desulfurizer flows from top to bottom. The two are countercurrently contacted. The hydrogen sulfide in the coking liquefied gas is absorbed by the desulfurizer and then discharged from the bottom of the tower. The coking liquefied gas after removal of hydrogen sulfide is discharged from the top of the tower.

[0084] (2) Coking liquefied gas desulfurization: the coking liquefied gas after desulfurization of hydrogen sulfide enters the alkali washing fiber membrane desulfurization tank to remove mercaptans in the coking liquefied gas by traditional alkali washing fiber membrane contact method.

[0085] (3) Coking liquefied gas dehydration: the coking liquefied gas is first subjected to preliminary dehydration in a coalescence dehydration tank, and then further dehydrated in a flake alkali dehydration tower to reduce the water content in the coking liquefied gas to below 10 ppm.

[0086] (4) Coking liquefied gas desulfurization: the coking liquefied gas after dehydration enters the hydrolysis desulfurization tank. The hydrolysis desulfurization tank uses a self-made carbonyl sulfide hydrolysis catalyst which has a unique core-shell structure. The reaction process is as follows: the coking liquefied gas penetrates through the catalyst shell, diffuses to the core, and undergoes COS hydrolysis reaction. Further generated H2S diffuses to the shell, where H2S capture occurs, thereby completing a complete sulfide (carbonyl sulfide + hydrogen sulfide) removal process. Finally, coking liquefied gas with a total sulfur content of 4 ppm is obtained.

[0087] The preparation method of the self-made carbonyl sulfide hydrolysis catalyst is as follows:

[0088] Preparation of catalyst core: 989g of HY molecular sieve, 256g of metatitanic acid, and 24g of polyvinyl alcohol were weighed and mixed uniformly to form a solid material. 21g of nitric acid was weighed and dissolved in water to form a solution. The uniformly mixed solid material was placed in a rolling ball machine, and the solution was sprayed onto the material in the rolling ball machine. The rolling ball machine was rotated to form small balls with a diameter of 2mm. The small balls were dried at 120℃ for 6h and calcined at 400℃ for 5h to obtain the catalyst A core carrier.

[0089] A solution was prepared by dissolving 89g of potassium nitrate, 74g of gallium nitrate, and 65g of lanthanum nitrate in water. The catalyst A core carrier was immersed in the solution for 3h. The impregnated carrier was dried at 130℃ for 4h and calcined at 490℃ for 5h to obtain the catalyst B core.

[0090] Catalyst shell coating:

[0091] HZSM-23 carrier 7 g was weighed and dispersed in 163 mL of methanol, and a uniform mixture I was obtained by stirring and ultrasonic treatment; 2 g of zinc nitrate hexahydrate was weighed and added to the mixture I, and the mixture was continuously stirred at 25°C for 30 min to make it fully dissolved, to obtain mixture II; 12 g of methyl imidazole was added to the mixture II, and the mixture was continuously stirred at 25°C for 3 h to obtain a composite; the above obtained catalyst A core was added to a coating machine, and the composite was coated, and the thickness of the coating was controlled to be about 1 mm. After coating, the small balls were dried at 100°C for 4 h; and after drying, the catalyst was calcined at 650°C for 3 h under a nitrogen atmosphere to obtain a carbonyl sulfur hydrolysis catalyst B.

[0092] Comparative Example 1

[0093] In this example, fresh catalytic cracking catalyst was used, and the coking liquefied gas catalytic thermal cracking test was carried out on a RU-II type continuous riser catalytic cracking evaluation test device. The reaction temperature was 390°C, the regenerated catalyst was introduced into the reactor bottom from the regenerator through the retransport line, the coking liquefied gas from a certain refinery was pre-lifted and preheated to enter the riser reactor to contact the catalyst to occur cracking reaction, the reactants and catalyst were lifted to the separator, and after sedimentation and filtration, they entered the post-fractionation system from the top of the settler. The carbonized catalyst fell into the stripper and was steam stripped, and then was transported to the top of the regenerator through the standby transport line. In the regenerator, the carbonized catalyst was regenerated by air coking. The regenerated catalyst flowed into the regenerated catalyst transport line. The circulation amount of the catalyst was controlled by the opening degree of the standby slide valve and the regeneration slide valve. The cracking gas was metered by a dry gas meter. After the coking liquefied gas was catalytically thermally cracked, the loss rate was about 7%.

[0094] Comparative Example 2

[0095] In this example, the waste catalytic cracking catalyst was only subjected to a regeneration step without modification. The rest was the same as in Example 2.

[0096] The coking liquefied gas was subjected to catalytic thermal cracking reaction by the unmodified catalytic cracking catalyst, and then was further subjected to coking liquefied gas hydrogen sulfide removal, coking liquefied gas mercaptan removal, coking liquefied gas dehydration, coking liquefied gas carbonyl sulfur removal, and the like, to finally obtain coking liquefied gas with a total sulfur of 15 ppm.

[0097] Obviously, the above examples are only examples for clear illustration, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. It is not necessary or possible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for deep desulfurization of coking liquefied gas, characterized in that: The following steps are involved: a. regenerating and modifying the spent catalytic cracking catalyst, which includes charring the spent catalytic cracking catalyst, mixing and grinding the charred catalyst with a molecular sieve, and curing and molding the regenerated and modified catalyst; b. contacting the coking liquefied gas with the regenerated and modified catalyst to perform a catalytic thermal cracking reaction to thermally crack the macromolecular sulfides in the coking liquefied gas into small molecular sulfides; c. The coking liquefied gas after the catalytic thermal cracking reaction is sequentially subjected to hydrogen sulfide removal, mercaptan removal, dehydration, and carbonyl sulfide removal to ultimately obtain desulfurized coking liquefied gas; The process of carrying out the charring treatment on the spent catalytic cracking catalyst includes primary charring and secondary charring; The molecular sieve is CuY molecular sieve; The decarbonyl sulfide treatment uses a carbonyl sulfide hydrolysis catalyst, which has a core-shell structure; the core is composed of aluminum oxide, silicon dioxide or titanium oxide, and the main active component is potassium oxide, gallium oxide or lanthanum oxide; the outer shell is C and N doped zinc oxide, aluminum oxide or silicon dioxide.

2. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: During the primary coking, the riser reactor inlet temperature is 450-590°C, the nitrogen space velocity is 800-1500h -1 , air speed 60-150h -1 , the scorching time is 2-6h.

3. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: During the secondary coking, the riser reactor inlet temperature is 499-606°C, the nitrogen space velocity is 800-1500h -1 , air speed 200-650h -1 , scorching time 3-9h.

4. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: The mass ratio of the charred catalyst to the molecular sieve is 3-7:

1.

5. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: The curing temperature of the curing molding is 550-750° C., and the curing time is 2-6 hours.

6. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: 60-70 wt% of the regenerated and modified catalyst has a particle size within the range of 30-95 μm.

7. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: The reaction temperature of the catalytic thermal cracking reaction is 350-420°C.

8. The method for deep desulfurization of coking liquefied gas according to claim 1, characterized in that: The total sulfur content of the coking liquefied gas after desulfurization treatment is less than 5ppm.