CN109957421B - Combination method of catalytic cracking and light hydrocarbon deep processing - Google Patents

Abstract

The invention provides a combined method of catalytic cracking and light hydrocarbon deep processing. Step 1, establishing a light hydrocarbon collection system: establishing a C3-C6 light hydrocarbon collecting system through newly-built connecting pipelines at the separation system or the outflow pipeline position of one or more light hydrocarbon deep processing devices in a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device, and collecting one or more partially or completely unreacted C3-C6 light hydrocarbons; step 2, pretreating the collected C3-C6 light hydrocarbon: C3-C6 light hydrocarbons collected in the step 1 are introduced into a dividing wall type heat exchanger or a boiler to be completely gasified; and 3, introducing the completely gasified C3-C6 light hydrocarbon in the step 2 into a catalytic cracking device independently or after being mixed with steam, contacting with a hot regenerated catalyst, and partially reacting in a catalytic cracking reactor to generate active light hydrocarbon required by a light hydrocarbon deep processing device matched with a refinery enterprise. The method can improve the yield of the product of the light hydrocarbon deep processing device.

Description

Combination method of catalytic cracking and light hydrocarbon deep processing

Technical Field

The invention relates to a combined method of catalytic cracking and light hydrocarbon deep processing, belonging to the technical field of petrochemical industry.

Background

In order to improve economic benefit, refinery enterprises carry out deep processing on light hydrocarbons of C3-C7 fractions produced by catalytic cracking, coking and other devices, a gas separation device separates C3 components and further separates the propylene to enter a polypropylene device, and simultaneously, a propane-rich material flow is obtained by separation and is generally collected into liquefied gas components for sale or enters a propane dehydrogenation device; and C4 fraction separated by the gas separation device sequentially enters an MTBE device and an alkylation device, isobutene is converted into MTBE in the MTBE device, and isobutane and residual butene are reacted in the alkylation device according to the ratio of 1: 1 into alkylate with high octane number; the C4 fraction can also enter a methyl ethyl ketone device after entering an MTBE device, and the residual chain butene is converted into methyl ethyl ketone; the C5-C7 light gasoline fraction enters a light gasoline etherification device, active olefins which can be etherified in the catalytic gasoline, such as 2-methyl-1-butene and 2-methyl-2-butene which are used as isoamylene and 2-methyl-1-pentene which are used as isohexene, can react with alcohols to generate corresponding ethers, and the olefin content of the catalytic gasoline can be reduced by 10-15 percent. The hydrocarbons which can react in the light hydrocarbon deep processing device to generate high-value target products are active light hydrocarbons, such as propylene of a polypropylene device, isobutene of an MTBE device, isobutane and butylene of an alkylation device, n-butene of a methyl ethyl ketone device and the like. The refinery basically forms a refinery integrated combined process which takes a catalytic cracking device as a tap and is matched with a C3-C7 light hydrocarbon deep processing device, so that low-value liquefied gas components can be processed to generate high-value polypropylene, MTBE, methyl ethyl ketone, alkylate oil and etherified light gasoline, the value of light hydrocarbon products is improved, and the olefin content of gasoline blending components can be further reduced to a certain extent.

The light hydrocarbon deep processing device types and scales equipped by different refinery enterprises are different, and generally comprise one or more of polypropylene, MTBE, alkylation, light gasoline ether and methyl ethyl ketone devices, and the processing capacities of the devices matched with catalysis are different. The unreacted light hydrocarbon from the light hydrocarbon deep processing device, C3-C4 components are generally sold as liquefied gas at low price, and the light gasoline components are generally not separated, namely the light gasoline after ether directly enters a gasoline blending pool to be blended into finished gasoline. The existing refinery enterprises do not consider the comprehensive optimization of the FCC serving as a tap and comprising various C3-C6 light hydrocarbon deep processing devices as a whole.

It has been found through research that the unreacted light hydrocarbon stream exiting the light hydrocarbon further processing unit still contains a significant amount of hydrocarbons that can be further catalytically cracked. The olefin is generally considered to have higher reaction activity of cracking, isomerization and the like, for example, 30 to 60 percent of olefin, mainly other three isomers of isobutene, still exists in unreacted C4 extracted from the top of a methanol extraction tower in an MTBE device; part of unreacted light gasoline extracted from the top of the methanol extraction tower for light gasoline etherification also contains 25-50% (volume percentage) of olefins, including unconverted C5-C7 active olefins and inactive olefins. Research on how to promote the further conversion of the part of olefins mainly focuses on that an optional light hydrocarbon isomerization module is arranged in an etherification integral technology (such as a light gasoline etherification process of CDTECH), but light gasoline needs to be regasified to about 400 ℃ and enters an isomerization reactor for intermittent regeneration again, so that the operation is complex, the energy consumption is high, and the isomerization module is not selected or the operation rate is low when the existing refining enterprise technology is selected. Streams rich in normal butane and isobutane and containing considerable amount of butylene are output from light hydrocarbon deep processing devices such as an alkylation device and a methyl ethyl ketone device, and the streams are generally collected by existing refining and chemical enterprises and then sold as liquefied gas at low price.

The light hydrocarbon enters a catalytic cracking unit to react again, which is also a research hotspot. In order to improve the quality of gasoline, reduce the olefin content of gasoline and improve the yield of liquefied gas, a large number of technical measures for recycling catalytic gasoline are disclosed at home and abroad, and two typical measures are as follows: (1) the gasoline is recycled to the crude heavy oil riser, generally injected into the upstream of a raw oil nozzle, for example, USP5043522 and USP5846403 disclose that the catalytic cracking gasoline is injected into the upstream of the raw oil feeding nozzle and is catalytically converted by using a high-temperature and high-activity regenerated catalyst; CN1160746A also discloses a method for injecting low-quality gasoline such as straight-run gasoline, coker gasoline, etc. into the lower reaction part of the riser to make it preferentially contact with regenerated catalyst; (2) the method comprises the steps of adopting a single gasoline riser to refine gasoline, such as CN1069054A and USP3784463, to react by adopting a catalytic cracking device with double riser reactors, injecting low-quality gasoline including catalytic cracking crude gasoline into a gasoline riser reactor, and utilizing reaction conditions of high temperature and large catalyst-to-oil ratio to realize catalytic modification of the low-quality gasoline so as to improve the yield of liquefied gas and the octane number of the gasoline. Researchers at home and abroad (CORMA A, MELO F V, et al. applied catalysts A: General,2004,265:195-206.) found that when high yield of low-carbon olefins (ethylene, propylene, butylene) is required, the product distribution is better by adopting the first recycling mode, because the temperature of a reaction system is reduced after the heavy oil raw material is injected, the reaction time of oil and solvent is shortened, and the reaction of generating dry gas by over cracking of gasoline in a high-temperature environment is stopped in time. The gasoline is recycled by adopting the independent lifting pipe, the gasoline recycling reactor can be additionally arranged on the basis of the traditional single lifting pipe reactor, the mutual interference of light and heavy raw materials in the reaction process can be avoided, the zone reaction of different raw materials is realized, and the recycling reaction depth of the gasoline can be adjusted. Researchers at home and abroad hardly study the re-reaction of C3-C4 fraction liquefied gas which is lighter than gasoline in a catalytic cracking industrial device; meanwhile, in the industrial application of the catalytic cracking device, high-pressure liquid-phase light hydrocarbon is generally adopted to be fed through a special light hydrocarbon nozzle, and enters the interior of the lifting pipe to be contacted with a hot regenerated catalyst, so that the catalyst is likely to be thermally cracked to be catalyst powder with smaller particles due to rapid gasification expansion, the catalyst consumption of the catalytic device is increased, and cold liquid-phase hydrocarbon absorbs a large amount of heat in the gasification process to cause the local temperature around the hydrocarbon to be low, so that the conversion rate of the light hydrocarbon is reduced, and the reaction depth design that the light hydrocarbon enters the catalytic device to react again can not be achieved. For example, Daqing refining company (Wangwei, Weiqiang, Xuzhanwu, etc. catalytic cracking gasoline recycling technology application, oil refining design, 2002, 32 (3): 24-28) adopts cold liquid phase gasoline to cross-line into a pre-lifting steam pipeline, so that the mixing temperature is too low, the damage of the catalyst is aggravated, and the loss of the catalyst is caused.

The purity of the unreacted light hydrocarbon from the light hydrocarbon further processing unit has also been investigated, for example, the ether light hydrocarbon contains a certain amount of methanol. CN86101079A discloses a process for catalytic cracking of petroleum hydrocarbons with methanol as a reactant, which is contacted with a fine particle ZSM-5 catalyst, such that the exothermic methanol conversion reaction is substantially heat balanced with the endothermic catalytic cracking reaction. "petrochemical, 2009,38 (3): 267-272' researches on the mixing and modification of methanol and catalytic gasoline on a small-sized riser, and the results show that the mixing of methanol and FCC gasoline improves the quality of gasoline, and is beneficial to increasing the yield of cracked gas and increasing the liquid yield. However, the coupling reaction of methanol conversion and catalytic cracking of petroleum hydrocarbon is limited by process conditions, catalyst activity and selectivity, and the methanol conversion rate and olefin selectivity are not high. CN200610091074.6 and CN200810117095.X disclose catalysts containing silicoaluminophosphate molecular sieve compositions, and researches show that oxygen-containing compounds can be converted into low-carbon olefins at lower temperature and carbon deposition catalysts, and the conversion rate is higher, but the method needs to replace the catalysts of the existing catalytic devices and independently transform the settler part of a riser.

Disclosure of Invention

The invention mainly aims to provide a combined method of catalytic cracking and light hydrocarbon deep processing, which aims to solve the problem of low product yield of a light hydrocarbon deep processing device in the prior art.

In order to achieve the above object, the present invention provides a combined process of catalytic cracking and light hydrocarbon deep processing, comprising the steps of:

step 1, establishing a light hydrocarbon collection system: establishing a C3-C6 light hydrocarbon collecting system through a newly-built connecting pipeline at the position of a separation system or a device outflow pipeline of one or more light hydrocarbon deep processing devices in a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device configured in the existing refinery enterprise, and collecting one or more partial or all unreacted C3-C6 light hydrocarbons;

step 2, pretreating the collected C3-C6 light hydrocarbon: C3-C6 light hydrocarbons collected in the step 1 are introduced into a dividing wall type heat exchanger or a boiler to be completely gasified, the pressure of the gasified light hydrocarbons is more than 0.5MPa, the temperature needs to meet the requirement that the temperature of the gasified light hydrocarbons is more than 160 ℃ and the superheat degree is more than 20 ℃ at the same time;

and 3, introducing the completely gasified C3-C6 light hydrocarbon in the step 2 into a catalytic cracking device independently or after being mixed with steam, contacting with a hot regenerated catalyst, and partially reacting in a catalytic cracking reactor to generate active light hydrocarbon required by a light hydrocarbon deep processing device matched with a refinery enterprise.

The invention relates to a combined method of catalytic cracking and light hydrocarbon deep processing, wherein raw materials of one or more of a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device in the step 1 are preferably sourced from a catalytic cracking reactor.

The combination method of catalytic cracking and light hydrocarbon deep processing, provided by the invention, comprises the step 3 of preferably introducing the active light hydrocarbon into one or more light hydrocarbon deep processing devices of a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device configured in the existing refinery enterprise for treatment.

The combined method of catalytic cracking and light hydrocarbon deep processing is characterized in that the C3-C6 light hydrocarbon completely gasified in the step 2 in the step 3 is introduced into a catalytic cracking device independently or after being mixed with water vapor, namely the C3-C6 light hydrocarbon is introduced into a light hydrocarbon feeding nozzle at the lower part of an independent light hydrocarbon riser reactor in the catalytic cracking device independently or after being mixed with water vapor, or is introduced into a light hydrocarbon feeding nozzle at the lower part of a heavy oil feeding nozzle of a heavy oil riser in the catalytic cracking device, or is introduced into a heavy oil riser pre-lifting steam pipeline or a dry gas pre-lifting pipeline to be mixed with steam and then enters a heavy oil riser pre-lifting section.

The invention relates to a combined method of catalytic cracking and light hydrocarbon deep processing, wherein a riser in a catalytic cracking device adopts a non-expanding riser, or an expanding riser with an expanded bottom and a vertical conveying pipe structure, or a bottom expanding riser, or a middle expanding riser.

The combined method of catalytic cracking and light hydrocarbon deep processing is characterized in that the collected unreacted C3-C6 light hydrocarbon is preferably one or more light hydrocarbon material flows rich in propane, n-butane, isobutane, butylene and light gasoline after ether.

The combined method of catalytic cracking and light hydrocarbon deep processing comprises the step of recovering unreacted C3-C6 light hydrocarbon from an MTBE device and/or a light gasoline etherification device, wherein the unreacted C3-C6 light hydrocarbon comprises methanol.

In the step 3, the weight of the C3-C6 light hydrocarbon which is introduced into the catalytic cracking device and is completely gasified preferably accounts for 0-40% of the weight of the heavy oil introduced into the catalytic cracking device.

The combined method of catalytic cracking and light hydrocarbon deep processing, provided by the invention, comprises the following steps of (1) in the step 3, preferably, the contact temperature of C3-C6 light hydrocarbon and a hot regenerated catalyst is 640-700 ℃, and the outlet temperature of a light hydrocarbon riser is 580-670 ℃; the outlet temperature of the heavy oil riser is 500-560 ℃.

The combined method of catalytic cracking and light hydrocarbon deep processing is characterized in that the regenerated catalyst is a catalytic cracking catalyst, the active component of the catalytic cracking catalyst is one or more of Y or HY type zeolite containing or not containing rare earth, ultrastable Y type zeolite containing or not containing rare earth, silicoaluminophosphate zeolite, ZSM-5 zeolite and high-silicon zeolite with a pentasil structure, or the catalytic cracking catalyst is an amorphous silicoaluminophosphate catalyst.

The invention relates to a combined method of catalytic cracking and light hydrocarbon deep processing, wherein the catalytic cracking catalyst preferably contains five-membered ring structure zeolite accounting for 5-40% of the weight of the catalytic cracking catalyst.

The invention has the beneficial effects that:

the combined method of catalytic cracking and light hydrocarbon deep processing provided by the invention optimizes the flow direction of intermediate reactants among different devices so as to optimize the whole product structure, and can stop part of operation units so as to save the operation energy consumption of the devices. If the light hydrocarbon after ether enters the catalytic device for recycling, the isomerization of olefin in the light hydrocarbon after ether is realized in the catalytic device, and an isomerization unit of an etherification device can be omitted; the etherified light hydrocarbon is recycled to the catalytic device without separating a small amount of methanol, so that a methanol extraction tower and a methanol recovery tower of the etherified device can be stopped, the methanol enters the catalytic device for recycling, the yield and the selectivity of the low-carbon olefin can be improved, and the product distribution of the catalytic device is optimized; under the condition of the same device scale, because light hydrocarbon circulates between the catalytic device and the etherification device, the etherification raw material can be greatly improved, and the yield of etherification products is improved.

In addition, the unreacted light hydrocarbon separated from the light hydrocarbon deep processing device returns to the catalytic cracking device again for reaction, and the generated active light hydrocarbon is continuously subjected to the light hydrocarbon deep processing technology, so that the yield of products of the light hydrocarbon deep processing device is improved.

Drawings

FIG. 1 is a schematic view of a process of combining a catalytic unit and an MTBE unit in example 1 of the present invention;

FIG. 2 is a schematic view of a combined process of a catalytic apparatus and a light gasoline etherification apparatus according to example 2 of the present invention;

FIG. 3 is a schematic view of a combined process of a catalytic apparatus and an etherification apparatus according to example 3 of the present invention;

FIG. 4 is a schematic view of a combination process of a catalytic unit and MTBE, methyl ethyl ketone and the like in example 4 of the present invention;

FIG. 5 is a schematic view of the combined process of the catalytic unit and the light hydrocarbon deep processing unit established in the refinery.

Detailed Description

The following examples illustrate the invention in detail: examples detailed embodiments and procedures are given on the premise of the technical scheme of the present invention, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.

The invention provides a combined method of catalytic cracking and light hydrocarbon deep processing. The method is characterized in that light hydrocarbon produced by a catalytic cracking device is introduced into a light hydrocarbon deep processing device for reaction, part of unreacted light hydrocarbon passes through a light hydrocarbon recovery system and is pretreated and then returns to a proper position of a catalytic cracking device reactor for re-reaction, and the reacted product is introduced into the light hydrocarbon deep processing device again for treatment. The invention can improve the yield of active light hydrocarbon of a light hydrocarbon deep processing device and can reduce the olefin content in the gasoline blending component to a certain degree.

The light dydrocarbon in the range of unreacted C3-C6 recovered by the light dydrocarbon deep processing device has quite high conversion rate at the temperature of over 620 ℃ under the reaction condition of the existence of a catalytic cracking catalyst, the light dydrocarbon can generate a series of reactions such as thermal cracking, oligomerization cracking, hydrogen transfer, isomerization and the like, and the proportion of the light dydrocarbon in the raw materials of the light dydrocarbon deep processing device in the reacted product is greatly increased. If the content of isobutene in C4 is almost zero after etherification, isobutene can rise to more than 40 percent of the whole butene proportion after the reaction; propane, isobutane, n-butane and the like also have considerable conversion rate and yields of ethylene, propylene and butylene under the high-temperature catalytic cracking condition.

The invention provides a combined method of catalytic cracking and light hydrocarbon deep processing, which comprises the following steps: the C3-C4 and/or light gasoline produced by catalytic cracking are respectively fed into light hydrocarbon deep processing devices such as a polypropylene device, an alkylation device, an MTBE (methyl tert-butyl ether) and/or light gasoline etherification device and the like configured in the existing refinery after raw material pretreatment for reaction, unreacted C3-C6 light hydrocarbons are recovered, and are returned to the catalytic device for reaction after the pretreatment such as heating gasification and the like, so that the yield of reactive light hydrocarbons such as propylene, isobutane, butene and the like which can be used as raw materials of the light hydrocarbon deep processing device and are produced by the catalytic cracking device is increased. Thereby realizing the comprehensive optimization of the light hydrocarbon deep processing technologies such as catalytic cracking, alkylation and the like to form a combined technology. The invention can improve the treatment capacity and the product yield of the light hydrocarbon deep processing device of the existing refinery without greatly adjusting the process technology and the catalyst of the refinery, improve the yields of etherified products such as polypropylene, alkylate oil, methyl ethyl ketone, methyl tert-butyl ether (MTBE), methyl tert-amyl ether (TAME), methyl tert-hexyl ether (MTHEXE), methyl tert-heptyl ether (MTHEPE) and the like, and simultaneously reduce the olefin content in gasoline blending components to a certain degree. The invention can obviously optimize the product distribution of the refining enterprises, improve the yield of high-value products and improve the economic benefit.

The invention selects light hydrocarbon flow entering a catalytic device for re-reaction on the basis of carrying out comprehensive accounting optimization on catalytic cracking and C3-C6 light hydrocarbon deep processing devices, and the recovered unreacted C3-C6 light hydrocarbon enters an unreacted light hydrocarbon collecting and preprocessing system, namely, one or more partially or completely unreacted light hydrocarbons flowing out from middle flows of separation systems or devices of light hydrocarbon deep processing devices such as polypropylene, alkylation, MTBE and/or light gasoline etherification and the like configured by refining enterprises are collected and enter the unreacted light hydrocarbon collecting and preprocessing system. The selection principle of the light hydrocarbon material flow fully considers the factors of the product distribution of the high-temperature catalytic cracking of the light hydrocarbon, the price difference between the product and the raw material, the local market condition and the like. Therefore, the invention can relatively flexibly adjust the catalytic device and the light hydrocarbon deep processing device according to the market and the potential of the catalytic device and the light hydrocarbon deep processing device which are fully developed, thereby producing reactive active light hydrocarbon such as propylene, isobutene, isobutane, butene and the like which can be processed by the light hydrocarbon deep processing device of a high-yield refining enterprise, further producing products with high cost performance in the market or in short supply, and improving the profitability of the refining enterprise under the change of a complex market.

The recycled unreacted light hydrocarbon enters the catalytic cracking device for re-reaction (recycling), and the recycling mode can adopt several recycling modes, namely C3-C6 light hydrocarbon is singly introduced into the bottom of a single light hydrocarbon recycling reactor in the catalytic cracking device or introduced into a light hydrocarbon feeding nozzle at the lower part of a heavy oil feeding nozzle of a heavy oil riser in the catalytic cracking device after being mixed with water vapor, or introduced into a pre-lifting steam pipeline of the catalytic cracking reactor or a dry gas pre-lifting pipeline and steam are mixed and then enter a riser pre-lifting section. Meanwhile, the light hydrocarbon is firstly fed into a dividing wall type heat exchanger (shell-and-tube heat exchanger, plate-and-shell heat exchanger and the like) before being fed into a catalytic cracking device reactor, and can be completely gasified by adopting equipment such as a waste heat boiler or a conventional boiler and the like, and a heat source can be circulating oil at the middle part or the bottom part of a fractionating tower, or steam, or high-temperature flue gas, or combustion heat and the like. The pressure of the gas injected into the riser is required to be more than 0.5MPa, the dew point temperature of water vapor under the pressure is 152 ℃, and the dew point of light gasoline components C5-C6 is 90-150 ℃; in order to ensure that light hydrocarbon can smoothly enter the riser reactor and simultaneously avoid causing the light hydrocarbon or water vapor to be condensed into liquid again in the heat exchange process of the light hydrocarbon and the water vapor, the light hydrocarbon injected into the riser needs to simultaneously meet the following two conditions: (1) the pressure of gasified light hydrocarbon is more than 0.5 MPa; (2) the temperature of the gasified light hydrocarbon is more than 160 ℃, and simultaneously, the factors that the light hydrocarbon may also contain heavier gasoline, the pressure of the light hydrocarbon feeding may be higher and the like are considered, so that the gasification temperature of the light hydrocarbon which is actually fed is required to be 20 ℃ above the dew point temperature, namely the superheat degree of the light hydrocarbon is 20 ℃; both of the above conditions are satisfied simultaneously. The light hydrocarbon can also enter a pre-lifting steam pipeline or a dry gas pre-lifting pipeline to be mixed with steam and then enter the bottom of the lifting pipe. The catalytic cracking riser reaction of the invention can adopt a common pre-lifting structure, or an expanded diameter riser with an expanded diameter at the bottom and a vertical conveying pipe structure, or a middle expanded diameter riser. By adopting the technical measures of the invention, the full overheating gasification of the light hydrocarbon or the mixed gas of the light hydrocarbon and the water vapor is emphasized, and the superheated gasification can be used as a one-step lifting gas for lifting the hot regenerated catalyst conveyed from the regenerator; in the process, the light hydrocarbon can be uniformly mixed and contacted with the hot regenerated catalyst, the light hydrocarbon can be heated to high temperature more quickly, and no liquid phase appears in the heat exchange process, so that the catalyst is prevented from thermal collapse. The light hydrocarbon heating temperature in the implementation process of the technology can be 160-500 ℃, and preferably 200-400 ℃. The technical measures of the invention are adopted to slightly modify the existing catalytic cracking device, and generally only a light hydrocarbon collecting pipeline, a light hydrocarbon heating heat exchanger or a heating furnace of a refinery enterprise are needed to be established, and the overheated light hydrocarbon is connected into a proper pipeline or a gas nozzle of the catalytic device; when the scheme of introducing the superheated light hydrocarbon gas from the dry gas pre-lifting pipeline is modified, the method can be completed even in the state that the catalytic device does not stop working. When the processing scheme of the catalytic device is changed or the subsequent factors such as fractionation, a gas compressor, absorption stability, gas separation and the like are limited, the scheme of the invention can be conveniently cut out without influencing the normal operation of the device.

The recycling amount of unreacted C3-C6 light hydrocarbon entering the catalytic device is 0-40 wt% based on the weight of the heavy oil entering the catalytic device, the contact temperature of the light hydrocarbon of the catalytic device after recycling the light hydrocarbon and a regenerated catalyst is 640-700 ℃, and the outlet temperature of a riser of the catalytic device is 500-560 ℃.

The light hydrocarbon collected after the etherification device can contain a part of unreacted methanol. In the etherification reaction process, in order to recover unreacted methanol, a mixture of the light hydrocarbons after the etherification and obtained from the top of the etherification fractionating tower and methanol is usually fed into a methanol extraction tower to extract the methanol with water so as to separate the light hydrocarbons after the etherification, and the mixture of the methanol and the water needs a methanol recovery tower to be separated, so that the energy consumption is very high. The invention injects the methanol into the catalytic cracking device, thereby simultaneously realizing the coupling of methanol conversion and the catalytic cracking of petroleum hydrocarbon. According to the invention, researches show that the light hydrocarbon after ether contains relatively less methanol, and can be returned to the catalytic device for recycling without separation, and enter the light hydrocarbon recycling position of the invention, and the methanol is almost completely converted due to relatively high reaction severity; there is no particular requirement for the selection of the catalytic cracking catalyst.

The combination of the invention is to ensure the distillation range of the commercial gasoline, if the ether rear light hydrocarbon at the top of the methanol extraction tower is adopted for recycling, part of the ether rear light hydrocarbon enters the catalytic cracking device for recycling, and part of the ether rear light hydrocarbon is thrown out of the device; if the mixed raw material which takes the light hydrocarbon after the ether as the main and a small amount of methanol as the auxiliary at the top of the etherification separation tower is adopted for recycling, part of the light gasoline and/or mixed carbon four of the catalytic cracking device is removed from the etherification device, and part of the light gasoline and/or mixed carbon four is thrown out of the combined process device.

The etherification process is a common MTBE and catalytic light gasoline etherification process, is not particularly specific to a special etherification technology, generally comprises an etherification reaction unit, an etherification fractionating tower for realizing product separation, a methanol extraction tower and a methanol recovery tower, and the coupling process only needs to return materials which mainly contain light hydrocarbons after ethers and contain a small amount of methanol at the top of the etherification fractionating tower to a catalytic device; or returning light hydrocarbon after the ether at the top of the methanol extraction tower to the catalytic device.

The catalytic device can be realized by slightly improving the prior catalytic device, and if an independent lifting pipe is arranged, raw materials containing unreacted light hydrocarbon can be injected into the independent lifting pipe; if only one lifting pipe is provided, unreacted light hydrocarbon enters the bottom of the lifting pipe preferentially, and the temperature of the catalyst can be reduced because the light hydrocarbon is contacted with the high-temperature regenerated catalyst firstly and generates endothermic cracking reaction, so that the light hydrocarbon reacts with the regenerated catalyst, the coke formation on the catalyst is less, and the catalyst retains most of activity. The light hydrocarbon recycling improves the agent-oil ratio of heavy oil and the catalyst to a certain extent, reduces the contact temperature difference of the oil agent and is beneficial to the optimization of the distribution of catalytic products. Because the light hydrocarbon entering the riser reactor is required to be completely gasified, the light hydrocarbon can enter the bottom of the riser after being mixed with steam through the pre-lifting steam pipeline or the dry gas pre-lifting pipeline.

The catalytic cracking device of the invention has no special requirements on the catalyst, is suitable for all types of catalytic cracking catalysts, and the active components of the catalytic cracking device are selected from one, two or three of Y or HY type zeolite containing or not containing rare earth, ultrastable Y type zeolite containing or not containing rare earth, silicoaluminophosphate molecular sieves, ZSM-5 series zeolite or high-silicon zeolite with five-membered ring structure prepared by other methods, and amorphous silicon-aluminum catalyst. When the catalytic device is optimized, the original catalyst can be adopted, the catalyst containing the shape-selective molecular sieve can also be adopted, and the catalyst containing 5-40 wt% of five-membered ring structure zeolite in the active component is preferred.

The embodiments and features of the method of the present invention in experimental and industrial settings are further described below with reference to the accompanying drawings.

The light hydrocarbon deep processing device in fig. 5 comprises a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device, and can be increased or decreased according to the actual conditions of enterprises. In the actual operation process of an enterprise, the types and the quantity of remilled light hydrocarbon entering the catalytic device can be flexibly adjusted according to the market, the light hydrocarbon reaction characteristics and the device operation condition. The following examples are specific.

Example 1

Referring to fig. 1, the heavy oil catalytic cracking device in this embodiment is an industrial device of 250 ten thousand tons/year in a certain refinery, and the etherification device is an MTBE device designed to produce 8 ten thousand tons of MTBE every year. In the experimental process, ether light hydrocarbon at the top of the methanol extraction tower is heated by a heat exchanger and then enters a pre-lifting steam pipeline at the bottom of a lifting pipe of a catalytic device together with lifting steam, and the same volume of pre-lifting steam can be replaced by the gasified steam; meanwhile, experiments also investigate that the mixed light hydrocarbon raw material pumped out from the top of the etherification separation tower, which takes the light hydrocarbon after the ether as the main part and takes a small amount of methanol as the auxiliary part, enters the bottom of the lifting pipe of the catalytic device together with the lifting steam after being heated by the heat exchanger.

The recycling amount of the etherified light hydrocarbon is 5-20 ten thousand tons/year, the recycled light hydrocarbon preferentially reacts with the regenerated catalyst at the bottom of the riser, the contact temperature of the light hydrocarbon and the regenerating agent is 640-700 ℃, and the outlet temperature of the riser of the catalytic device is 500-540 ℃. Table 1 shows the results of two embodiments of example 1, wherein the light hydrocarbon after ether used in scheme 1 is taken from the top of the methanol extraction column, while the light hydrocarbon after ether used in scheme 2 is withdrawn from the top of the etherification and separation column.

TABLE 1 catalyst unit optimization examples in combination with MTBE

Example 2

Referring to fig. 2, the heavy oil catalytic cracking apparatus in this embodiment is an industrial apparatus of 250 ten thousand tons/year in a certain refinery, and the etherification apparatus is designed as a 50 ten thousand ton light gasoline etherification apparatus. In the experimental process, light hydrocarbon after ether at the top of the methanol extraction tower is heated and gasified by a heat exchanger and then enters the bottom of the heavy oil lifting pipe from a light hydrocarbon feeding nozzle below a heavy oil feeding nozzle of the heavy oil lifting pipe.

The remixing amount of the etherified light gasoline is 15-30 ten thousand tons/year, the remixed light hydrocarbon preferentially reacts with the regenerated catalyst through a light hydrocarbon feeding nozzle arranged at the bottom of a lifting pipe, the contact temperature of the light hydrocarbon and the regenerating agent is 640-700 ℃, and the outlet temperature of the lifting pipe of the catalytic device is 500-540 ℃. Table 2 lists the results of one embodiment of example 2.

TABLE 2 catalytic unit and light gasoline etherification unit combination optimization embodiment

Example 3

Referring to fig. 3, the heavy oil catalytic cracking device in this embodiment is an industrial device of 250 ten thousand tons/year in a certain refinery, and the etherification device is an MTBE device designed to produce 8 ten thousand tons of MTBE per year and a light gasoline etherification device designed to produce 50 ten thousand tons of MTBE per year. In the experimental process, two kinds of light hydrocarbons behind ether at the top of the methanol extraction tower are mixed, heated and gasified by a heat exchanger, and then enter the bottom of the heavy oil lifting pipe from a light hydrocarbon feeding nozzle below a heavy oil feeding nozzle of the heavy oil lifting pipe.

The remixing amount of the etherified C4 and the light gasoline after etherification is respectively 5-20 ten thousand tons/year and 15-30 ten thousand tons/year, the mixed remixed light hydrocarbon preferentially reacts with the regenerated catalyst at the bottom of the riser, the contact temperature of the light hydrocarbon and the regenerant is 640-700 ℃, and the outlet temperature of the riser of the catalytic device is 500-540 ℃. Table 3 lists the results of one embodiment of example 3.

TABLE 3 optimization of catalytic unit in combination with MTBE and light gasoline etherification unit

Example 4

Referring to fig. 4, the heavy oil catalytic cracking apparatus in this embodiment is an industrial apparatus of a certain refinery at 60 ten thousand tons/year, and the etherification apparatus is an MTBE apparatus designed to produce 5 ten thousand tons of MTBE annually and an MTBE apparatus designed to produce 4 ten thousand tons of methyl ethyl ketone annually. Limited by the processing capacity of the catalytic device and the subsequent light hydrocarbon deep processing device, 6 ten thousand tons/year of isobutane (content is 90 w%) rich material flow of the separation device for feeding the methyl ethyl ketone device is heated and gasified, passes through the dry gas pre-lifting pipeline and then is converged into the pre-lifting steam pipeline together with the pre-lifting steam to enter the bottom of the lifting pipe.

The recycling amount of the isobutane-rich material flow is 3-8 ten thousand tons/year, the heated and gasified material flow enters the bottom of a lifting pipe through dry gas and a lifting pipe line and lifting steam mixed oil and preferentially reacts with a regenerated catalyst, the contact temperature of light hydrocarbon and the regenerated catalyst is 640-700 ℃, and the outlet temperature of the lifting pipe of the catalytic device is 500-540 ℃. Table 4 lists the results of one embodiment of example 4.

TABLE 4 optimization of the combination of the catalytic unit with the MTBE and methyl ethyl ketone unit

It can be seen from tables 1-4 that, compared with the prior art (i.e. the unreacted light hydrocarbon in the light hydrocarbon deep processing device is not collected and is introduced into the catalytic cracking device for recycling), by adopting the method of the present invention, the yield of the active light hydrocarbon produced by the catalytic cracking device is increased, and the yield of the target product of the light hydrocarbon deep processing device is correspondingly increased.

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (13)

1. A combined method of catalytic cracking and light hydrocarbon deep processing is characterized by comprising the following steps:

step 1, establishing a light hydrocarbon collection system: establishing a C3-C6 light hydrocarbon collecting system through a newly-built connecting pipeline at the separation system or the device outflow pipeline position of one or more light hydrocarbon deep processing devices in a polypropylene device, an MTBE device, an alkylation device and a light gasoline etherification device configured by the existing refinery enterprises, and collecting one or more partial or all unreacted C3-C6 light hydrocarbons;

step 2, pretreating the collected C3-C6 light hydrocarbon: C3-C6 light hydrocarbons collected in the step 1 are introduced into a dividing wall type heat exchanger or a boiler to be completely gasified, the pressure of the gasified C3-C6 light hydrocarbons is more than 0.5MPa, the temperature simultaneously meets the requirements that the temperature of the gasified light hydrocarbons is more than 160 ℃ and the superheat degree is more than 20 ℃;

and 3, introducing the completely gasified C3-C6 light hydrocarbon in the step 2 into a riser reactor of a catalytic cracking device independently or after being mixed with steam, contacting with a hot regenerated catalyst, and reacting in the riser reactor to generate active light hydrocarbon required by a light hydrocarbon deep processing device matched with a refinery enterprise.

2. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 1, wherein the C3-C6 light hydrocarbons completely gasified in step 2 in step 3 are introduced into the riser reactor of the catalytic cracking unit separately or after being mixed with steam, and refer to the light hydrocarbon feed nozzles at the lower part of the light hydrocarbon riser where the C3-C6 light hydrocarbons are introduced into the catalytic cracking unit separately or after being mixed with steam; or a light hydrocarbon feeding nozzle at the lower part of a heavy oil feeding nozzle of a heavy oil riser of the catalytic cracking device, or a pre-lifting steam pipeline at the bottom of the heavy oil riser or a dry gas pre-lifting pipeline, and then the mixture is converged into the pre-lifting steam pipeline to be mixed with steam and then enters a pre-lifting section at the bottom of the heavy oil riser.

3. The combined catalytic cracking and light hydrocarbon further processing method according to claim 2, wherein the heavy oil riser in the catalytic cracking device is a non-expanded diameter riser, or a bottom expanded diameter riser, or a middle expanded diameter riser.

4. The combined catalytic cracking and light hydrocarbon deep processing method as claimed in claim 1, wherein the raw material of one or more light hydrocarbon deep processing units of the polypropylene unit, the MTBE unit, the alkylation unit and the light gasoline etherification unit in the step 1 is originated from a catalytic cracking unit.

5. The combination catalytic cracking and light hydrocarbon further processing method according to claim 1, wherein the collected unreacted C3-C6 light hydrocarbons include one or more of propane, n-butane, isobutane, butylene and light gasoline after ether separation at the top of the demethanizer of the light gasoline etherification apparatus.

6. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 1, wherein the active light hydrocarbon in step 3 is light hydrocarbon capable of undergoing chemical reaction in one or more light hydrocarbon further processing units of the polypropylene unit, the MTBE unit, the alkylation unit, and the light gasoline etherification unit configured in the existing refinery in step 1.

7. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 6, wherein the active light hydrocarbon in step 3 is propylene entering a polypropylene unit, isobutylene entering an MTBE unit, isobutane and chain butenes entering an alkylation unit, and isoamylene or isohexene entering a light gasoline etherification unit.

8. The combined catalytic cracking and light hydrocarbon further processing method as claimed in claim 7, wherein the isoamylene is 2-methyl-1-butene and/or 2-methyl-2-butene, and the isohexene is 2-methyl-1-pentene.

9. The combined catalytic cracking and light hydrocarbon deep processing method of claim 1, wherein the unreacted C3-C6 light hydrocarbons recovered from the MTBE unit and/or the light gasoline etherification unit include methanol.

10. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 1, wherein in step 3, the weight of the completely gasified C3-C6 light hydrocarbon introduced into the catalytic cracking unit accounts for 0-40% of the weight of the heavy oil introduced into the catalytic cracking unit.

11. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 2, wherein in step 3, the contact temperature of the C3-C6 light hydrocarbon and the hot regenerated catalyst is 640-700 ℃, the outlet temperature of the light hydrocarbon riser is 580-670 ℃, and the outlet temperature of the heavy oil riser is 500-560 ℃.

12. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 1, wherein the regenerated catalyst is a catalytic cracking catalyst, the active component of the catalytic cracking catalyst is selected from one or more of Y or HY type zeolite containing or not containing rare earth, ultrastable Y type zeolite containing or not containing rare earth, silicoaluminophosphate zeolite, ZSM-5 zeolite and high silica zeolite with pentasil structure, or the catalytic cracking catalyst is an amorphous silicoaluminophosphate catalyst.

13. The combination of catalytic cracking and light hydrocarbon further processing as claimed in claim 12, wherein the catalytic cracking catalyst contains 5-40 wt% of the catalytic cracking catalyst of the high-silicon zeolite with five-membered ring structure.

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