A method and system for producing low carbon olefins

Abstract

The present disclosure relates to a method and system for producing low-carbon olefins, in which a separate light hydrocarbon reaction bed is provided, and the light hydrocarbon and the second catalyst are countercurrently contacted in the bed for catalytic conversion reaction, so as to avoid the influence of the coked catalyst in the first riser on the second catalyst, and the conversion efficiency is high, and dilution steam is not needed to be injected, and the energy consumption of the device is low.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of catalytic cracking, in particular, to a method and system for producing low-carbon olefins. BACKGROUND

[0002] The catalytic cracking (FCC) device is one of the typical oil refining devices, which is used to crack heavy feedstock oil into small molecules such as gasoline, diesel, and liquefied gas under the action of continuously regenerated catalyst and suitable process conditions. At present, the catalytic cracking process is widely used and mature. The catalytic cracking reaction is in the form of a riser plug flow and short contact of catalyst-gas. The feedstock oil is fully mixed, accelerated, and stabilized with atomized steam in the feedstock oil nozzle, and then sprayed into the riser at a certain speed to contact with the high-temperature regenerated catalyst from the regeneration inclined pipe in the riser, rapidly gasify and react. The catalyst, heavy feedstock oil, and cracked oil gas flow upward in the riser. As the flow proceeds, the large molecules of the feedstock oil are cracked into small molecules of liquid products (gasoline and diesel) and smaller molecules of light hydrocarbon products (dry gas and liquefied gas). At the same time, the gum and asphaltene in the heavy feedstock oil generate coke and adhere to the catalyst. A coarse cyclone separator or a rapid separator is used at the outlet of the riser to pre-separate the catalyst and the cracked oil gas. Most of the catalyst enters the stripping section at the lower part of the reactor. The oil gas containing a small amount of catalyst passes through the coarse cyclone riser, the dilute phase of the reactor, and enters the single-stage or two-stage cyclone separator at the top of the reactor for further separation. The spent catalyst is stripped and then enters the regenerator through the spent inclined pipe for continuous coke-burning regeneration, and at the same time, the catalyst is heated and circulated back to the riser.

[0003] On the basis of catalytic cracking process, Research Institute of Petroleum Processing developed heavy oil catalytic pyrolysis (CPP) for olefins and enhanced catalytic cracking (DCC-Plus) process. The CPP process mainly produces more ethylene and propylene, and the DCC-Plus process mainly produces more propylene and aromatics, with by-product ethylene. The combination of riser and bed is used, and two risers, i.e. the main riser and the second riser, are provided. The main riser is an inner riser, and the feed is fresh feedstock oil injected by a feedstock oil nozzle, with a large amount of dilution steam injected to reduce the oil-gas partial pressure and increase the catalyst-oil ratio C / O. The outlet temperature is 50-100℃ higher than that of catalytic cracking, and the purpose is to crack heavy feedstock to produce naphtha (gasoline) components, which provides feedstock for the third reactor bed. The second riser is an outer riser, which is a catalyst supplementing riser, and creates suitable reaction conditions for the bed reaction, i.e. increases the overall catalyst activity of the bed. The lifting medium is all light gasoline and mixed C4 recycled for lifting, and the outlet temperature of the riser is as high as 620-670℃. The light gasoline and mixed C4 play a lifting role and basically do not convert in the riser. By injecting dilution steam, a large amount of regenerated catalyst is obtained, and the catalyst-oil ratio C / O is as high as 31-47 (mass ratio, for the feed of the second riser, i.e. 2-3 t of catalyst per kmol of feed). The third reactor is a bed reactor, and the products and catalyst of the first reactor of the main riser and the second reactor of the second riser, as well as stripping steam, pass through the third reactor. The weight hourly space velocity of the bed is controlled to be 2-4 h -1 In this reaction environment, more propylene is generated. Due to the large reaction depth and the need for more reaction heat, the catalyst-oil ratio C / O of the main riser is 9.3-15, and that of conventional catalytic cracking is 6.5. The catalyst-oil ratio C / O of the second riser is as high as 31-47, and the total catalyst-oil ratio C / O of the two risers is 15-25 (mass ratio, for fresh feed). The main features are as follows: the main riser uses heavy oil feedstock to produce naphtha (gasoline) components, and the outlet is a low-pressure distribution plate that uniformly distributes the catalyst and oil gas from the main riser to the third reactor bed, and the catalyst contains more carbon and heavy metals; the outlet of the second riser is a distribution tank that uniformly distributes most of the light gasoline and mixed C4 materials and catalyst to the third reactor bed, and the catalyst is basically fresh regenerated catalyst; the temperature of the third reactor bed is not controlled. Due to the introduction of fresh regenerated catalyst by the second riser, the catalyst activity is enhanced, and the bed space velocity is controlled by controlling the material level, thereby controlling the catalyst-gas contact time. The conversion of naphtha (gasoline) feedstock from the main riser and unconverted recycled light gasoline and mixed C4 from the second riser riser is realized, and the purpose of maximum production of propylene is achieved in this reaction environment.

[0004] However, there are still many deficiencies: (1) the non-naphtha (gasoline) components at the outlet of the third reactor bed have an impact on the conversion of gasoline and mixed C4, reducing the partial pressure of the raw material gas; (2) the catalyst at the outlet of the main riser has been covered by coking (the carbon deposition rate is about 0.5-0.6 w%) and contaminated by heavy metals, and the activity loss is large, which weakens the contribution of the light gasoline and mixed C4 to the recycling; (3) in the third reactor bed, there are engineering limitations in the uniform mixing, uniform distribution and fluidization of the two catalysts and oil gas; (4) the light naphtha (gasoline) recycled is subjected to fractionation after being depressurized at the bottom of the absorption stabilizer, and the process is long and the energy consumption of the device is high. SUMMARY

[0005] The purpose of the present disclosure is to overcome the defects of the existing CPP and DCC-Plus methods, such as the mutual influence of the two catalysts, low conversion efficiency, long process, high energy consumption of the device, etc., and to provide a method and system for producing low-carbon olefins.

[0006] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides a method for producing low-carbon olefins, which comprises:

[0007] S1, feeding heavy oil into a first riser to contact a first catalyst for catalytic cracking reaction to obtain a cracking product; introducing the cracking product into a first separator at the outlet of the first riser for first separation to obtain reaction oil gas and first spent catalyst;

[0008] introducing the first spent catalyst from the lower outlet of the first separator of the first riser into the stripping zone of the reactor arranged on the upper part of the first riser for stripping and then introducing it into a regenerator for regeneration to obtain first regenerated catalyst; introducing the first regenerated catalyst into the first riser for recycling;

[0009] S2, lifting the second catalyst introduced from the bottom inlet of the second riser to above the light hydrocarbon reaction bed in the second riser, and contacting it from top to bottom with at least part of the light hydrocarbon in countercurrent to perform catalytic conversion reaction to obtain process gas and second spent catalyst;

[0010] introducing the reaction oil gas obtained by first separation from the upper outlet of the first separator into the reactor, and introducing the process gas from the light hydrocarbon reaction bed into the reactor to mix with the reaction oil gas, and then sending it into the second separator at the upper part of the reactor for second separation, and sending the obtained oil gas into a fractionating column;

[0011] introducing the second spent catalyst as the first catalyst into the first riser for recycling.

[0012] Optionally, the method further comprises: injecting dilution steam from a middle portion of the first riser via a dilution steam nozzle; and a weight ratio of the heavy oil to the dilution steam is 1: (0.05-0.3), preferably 1: (0.1-0.18).

[0013] Optionally, the process gas from the light hydrocarbon reaction bed is introduced into the upper and / or lower portion of the dilute phase section of the reactor, mixed with the reaction oil, and then sent to a second separator in the upper portion of the reactor for a second separation, and the obtained oil gas is sent to a fractionating column.

[0014] Optionally, the heavy oil comprises at least one of wax oil, residual oil, and hydrocracking tail oil.

[0015] The first catalyst comprises: a CEP-1 catalyst and / or an ORBIT-3000 catalyst.

[0016] Optionally, the light hydrocarbon comprises at least one of mixed C4 light hydrocarbon, light gasoline, and propane.

[0017] The second catalyst comprises: a SAPO-34 catalyst.

[0018] Optionally, the reaction condition of the catalytic cracking comprises: a reaction temperature of 490-680°C, preferably 540-650°C; a reaction time of 1.5-6s, preferably 2-4s; a reaction pressure of 50-300kPag, preferably 80-200kPag; and a catalyst to oil ratio of 6-20, preferably 8-16.

[0019] An outlet temperature of the first riser outlet is 500-720°C, preferably 560-680°C.

[0020] A residence time of the reaction oil gas obtained by the first separation in the reactor with the process gas from the light hydrocarbon reaction bed is 1-4s, preferably 1.2-2.5s.

[0021] Optionally, the method further comprises: in step S2, after the light hydrocarbon is steam gasified and heated to 60-200°C, the light hydrocarbon is introduced from a second regeneration inclined pipe at the bottom of the second riser to below the light hydrocarbon reaction bed in the second riser.

[0022] The condition of the catalytic conversion reaction comprises: a reaction space velocity of 0.1-3h -1 , preferably 0.2-2h -1 ; a catalyst to oil ratio of 15-30, preferably 18-25; and a reaction temperature of 540-740°C, preferably 580-680°C.

[0023] Optionally, the method further comprises: in step S2, introducing the light hydrocarbon from the second riser bottom inlet to a gas distributor, and distributing the light hydrocarbon from bottom to top through the gas distributor;

[0024] The second catalyst introduced from the second regeneration spool at the bottom of the second riser is lifted to a distribution tank, and the second catalyst is distributed from top to bottom by the distribution tank;

[0025] The light hydrocarbon and the second catalyst are countercurrently contacted in a light hydrocarbon reaction bed for catalytic conversion reaction.

[0026] Another aspect of the present disclosure provides a system for producing low-carbon olefins, which comprises a first riser, a reactor sleeved on the upper part of the first riser, a second riser arranged in parallel with the first riser, and a regenerator;

[0027] The second riser comprises a light hydrocarbon reaction bed configured to countercurrently contact the second catalyst with at least part of the light hydrocarbon for catalytic conversion reaction;

[0028] The first riser comprises a heavy oil inlet, a first catalyst inlet, a first regenerated catalyst inlet, and a cracking product outlet; the cracking product outlet of the first riser is provided with a first separator comprising a cracking product inlet, a reaction oil gas outlet, and a first spent catalyst outlet; the cracking product outlet of the first riser is in communication with the cracking product inlet of the first separator;

[0029] The reactor comprises a process gas inlet and a first spent catalyst outlet, and the lower part of the reactor is a stripping zone; the first spent catalyst outlet of the first separator is located above the stripping zone of the reactor;

[0030] The regenerator comprises a first spent catalyst inlet, a second catalyst outlet, and a first regenerated catalyst outlet; the first spent catalyst outlet of the reactor is in communication with the first spent catalyst inlet of the regenerator; and the first regenerated catalyst outlet of the regenerator is in communication with the first regenerated catalyst inlet of the first riser;

[0031] The second riser is provided with a light hydrocarbon reaction bed configured to countercurrently contact the second catalyst with at least part of the light hydrocarbon for catalytic conversion reaction;

[0032] The second riser comprises a light hydrocarbon inlet, a second catalyst inlet, a process gas outlet, a second spent catalyst outlet, and a process gas outlet;

[0033] The second spent catalyst outlet of the second riser is in communication with the first catalyst inlet of the first riser; the process gas outlet of the second riser is in communication with the process gas inlet of the reactor sleeved on the upper part of the first riser.

[0034] The first riser is provided with a first separator at the cracking product outlet of the first riser, and a first spent catalyst outlet of the first separator is located above the stripping zone of the reactor; and the upper portion of the reactor is further provided with a second separator.

[0035] Optionally, a coking drum is arranged in the regenerator.

[0036] The first spent catalyst outlet of the reactor is communicated with the first spent catalyst inlet of the regenerator via a first spent catalyst inclined pipe; and the first regenerated catalyst outlet of the regenerator is communicated with the first regenerated catalyst inlet of the first riser via a first regenerated catalyst inclined pipe.

[0037] The second regenerated catalyst inclined pipe is arranged at the bottom of the second riser as an inlet for introducing the second catalyst, and the second catalyst inlet of the second riser is communicated with the second catalyst outlet of the regenerator via the second regenerated catalyst inclined pipe.

[0038] The first spent catalyst outlet of the reactor is communicated with the first spent catalyst inlet of the regenerator via a first spent catalyst inclined pipe; and the first regenerated catalyst outlet of the regenerator is communicated with the first regenerated catalyst inlet of the first riser via a first regenerated catalyst inclined pipe.

[0039] The second catalyst inlet of the second riser is communicated with the second catalyst outlet of the regenerator via a second regenerated catalyst inclined pipe; and the second spent catalyst outlet of the second riser is communicated with the first catalyst inlet of the first riser via a second spent catalyst inclined pipe.

[0040] The first separator comprises at least one of a coarse cyclone separator and a fast separator.

[0041] The second separator comprises at least one of a single-stage cyclone separator and a two-stage cyclone separator.

[0042] The second riser is sequentially provided with a distribution trough, a light hydrocarbon reaction bed and a gas distributor from top to bottom; the distribution trough is used for downward distribution of the second catalyst and injection from above the light hydrocarbon reaction bed; and the gas distributor is used for upward distribution of the light hydrocarbon and injection from below the light hydrocarbon reaction bed.

[0043] By the technical scheme, the method and system for producing low-carbon olefins are provided, the method makes the light hydrocarbon and the second catalyst contact in the independent reaction bed in countercurrent to perform the catalytic conversion reaction, avoids the catalytic conversion reaction from being affected by the coked catalyst in the first riser, has high conversion efficiency, and improves the yield of the olefins; the separator is arranged at the outlet of the main riser to separate the reaction oil gas and the spent catalyst quickly, the reaction oil gas has a short residence time in the reactor, and the secondary cracking is avoided, and the yield of impurities such as methane and hydrogen is reduced; part of the light hydrocarbon is used to lift the second catalyst to the reaction bed, and dilution steam does not need to be injected, and the production cost is reduced.

[0044] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0045] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation on the present disclosure. In the drawings:

[0046] Figure 1 A schematic diagram of a system for producing low-carbon olefins in an embodiment of the present disclosure.

[0047] Figure 2 A schematic diagram of a system for producing low-carbon olefins in an embodiment of the present disclosure.

[0048] Figure 3 A schematic diagram of a conventional catalytic cracking process system in Comparative Example 1.

[0049] Figure 4 A schematic diagram of an enhanced catalytic cracking process system in Comparative Example 2.

[0050] BRIEF DESCRIPTION OF DRAWINGS

[0051] 1, reactor; 2, regenerator; 3, decoking tank; 4, first riser; 5, 5', second riser; 6, first riser outlet low pressure drop distribution plate; 6', first separator; 7, 7', distribution groove; 8, third reactor bed; 8', light hydrocarbon reaction bed; 9, heavy oil feed nozzle; 10, back-fining light gasoline, mixed C4 feed nozzle; 10', gas distributor; 11, dilution steam nozzle; 12, first regeneration inclined pipe; 13, 13', second regeneration inclined pipe; 14, first spent catalyst inclined pipe; 15', light hydrocarbon reaction dilute phase; 16', light hydrocarbon conversion process gas outlet. DETAILED DESCRIPTION

[0052] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended for illustration and explanation of the present disclosure and are not intended to limit the present disclosure.

[0053] In the present disclosure, the words "first", "second", "third" and the like used herein are merely used to distinguish different components and do not contain actual meanings such as sequence of connection. In the present disclosure, the orientation words such as "upper", "lower", "top" and "bottom" generally refer to the upper and lower, top and bottom in the normal use state of the device.

[0054] The first aspect of the present disclosure provides a method for producing low-carbon olefins, which comprises:

[0055] S1, feeding heavy oil into a first riser 4 to contact a first catalyst for catalytic cracking reaction to obtain a cracking product; introducing the cracking product into a first separator 6' at the outlet of the first riser 4 for first separation to obtain reaction oil gas and first spent catalyst;

[0056] The first spent catalyst is introduced from the lower outlet of the first separator 6' at the outlet of the first riser 4 to the stripping zone of the reactor 1 set on the upper part of the first riser 4, and then introduced into the regenerator 2 after stripping to obtain first regenerated catalyst; the first regenerated catalyst is introduced into the first riser 4 for recycling;

[0057] S2, the second catalyst introduced from the bottom inlet of the second riser 5' is lifted to above the light hydrocarbon reaction bed 8' in the second riser 5', and is in countercurrent contact with at least part of the light hydrocarbon from below the light hydrocarbon reaction bed 8' from top to bottom for catalytic conversion reaction to obtain process gas and second spent catalyst;

[0058] The reaction oil gas obtained by first separation is introduced from the upper outlet of the first separator 6' into the reactor 1, and the process gas from the light hydrocarbon reaction bed 8' is introduced into the reactor 1 to mix with the reaction oil gas, and then sent to the second separator at the upper part of the reactor 1 for second separation, and the obtained oil gas is sent to the fractionating column;

[0059] The second spent catalyst is introduced into the first riser 4 as the first catalyst for recycling.

[0060] According to an embodiment of the present disclosure, the method further comprises: injecting dilution steam from the middle part of the first riser 4 through a dilution steam nozzle 11 to control the reaction pressure and the catalyst-oil ratio of the catalytic cracking reaction in the first riser 4; the weight ratio of the heavy oil to the dilution steam is 1: (0.05-0.3), preferably 1: (0.1-0.18).

[0061] According to one embodiment of the present disclosure, the process gas from the light hydrocarbon reaction bed 8' is introduced into the upper and / or lower part of the dilute phase section of the reactor 1, mixed with the reaction oil gas, and then sent to the second separator in the upper part of the reactor 1 for the second separation, and the obtained oil gas is sent to the fractionating column.

[0062] According to one embodiment of the present disclosure, the heavy oil includes at least one of wax oil, residual oil and hydrogenated tail oil.

[0063] The first catalyst includes CEP-1 catalyst and / or ORBIT-3000 catalyst.

[0064] According to one embodiment of the present disclosure, the light hydrocarbon includes at least one of mixed C4 light hydrocarbon, light gasoline and propane.

[0065] The second catalyst includes SAPO-34 catalyst.

[0066] The specific types of the first catalyst and the second catalyst in the present disclosure are not particularly limited, and can be catalysts for catalytic cracking and catalytic conversion reactions commonly used in the art.

[0067] According to one embodiment of the present disclosure, the reaction conditions of the catalytic cracking include: the reaction temperature is 490-680℃, preferably 540-650℃; the reaction time is 1.5-6s, preferably 2-4s, more preferably 2-3s; the reaction pressure is 50-300kPag, preferably 80-200kPag; the catalyst to oil ratio is 6-20, preferably 8-16.

[0068] The outlet temperature of the outlet of the first riser 4 is 500-720℃, preferably 560-680℃.

[0069] The residence time of the reaction oil gas obtained by the first separation in the reactor 1 with the process gas from the light hydrocarbon reaction bed 8' is 1-4s, preferably 1.2-2.5s.

[0070] In the present disclosure, the residence time of the process gas from the light hydrocarbon reaction bed 8' in the dilute phase of the reactor 1 is short, and secondary cracking is not easy to occur, thereby causing excessive generation of methane and hydrogen.

[0071] According to one embodiment of the present disclosure, in step S2, the light hydrocarbon is introduced into the lower part of the light hydrocarbon reaction bed 8' in the second riser 5' from the second regeneration inclined pipe 13' at the bottom of the second riser 5' after being steam gasified and heated to 60-200℃.

[0072] The conditions of the catalytic conversion reaction include: the reaction space velocity is 0.1-3h -1 , preferably 0.2-2h -1; the reaction temperature is 540-740°C, preferably 580-680°C; the agent / oil ratio is 15-30, preferably 18-25.

[0073] According to one embodiment of the present disclosure, in step S2, the light hydrocarbon is introduced from the bottom inlet of the second riser 5' to the gas distributor 10', and is distributed from bottom to top through the gas distributor 10';

[0074] At least part of the light hydrocarbon is introduced from the second regeneration elbow 13' at the bottom of the second riser 5' to the second catalyst riser-distributor 7', and the second catalyst is distributed from top to bottom by the second catalyst riser-distributor 7';

[0075] The light hydrocarbon and the second catalyst are countercurrently contacted in the light hydrocarbon reaction bed 8' for catalytic conversion reaction.

[0076] In another aspect, the present disclosure provides a system for producing low-carbon olefins, which comprises a first riser 4, a reactor 1 arranged on the upper part of the first riser 4, a second riser 5' arranged in parallel with the first riser 4, and a regenerator 2;

[0077] The first riser 4 is configured to contact heavy oil and first catalyst therein for catalytic cracking reaction;

[0078] The middle part of the second riser 5' is provided with a light hydrocarbon reaction bed 8', which is configured to contact at least part of the light hydrocarbon and the second catalyst therein for countercurrent catalytic conversion reaction;

[0079] The outlet of the first riser 4 is provided with a first separator 6', and the first spent catalyst outlet of the first separator 6' is located above the stripping zone of the reactor 1; the upper part of the reactor 1 is provided with a second separator, and the lower part is provided with a stripping zone;

[0080] The first riser 4 comprises a heavy oil inlet, a first catalyst inlet, a first regenerated catalyst inlet, and a cracking product outlet;

[0081] The second riser 5' comprises a light hydrocarbon inlet, a second catalyst inlet, a second spent catalyst outlet, and a process gas outlet;

[0082] The reactor 1 comprises a process gas inlet and a first spent catalyst outlet, and the lower part of the reactor 1 is a stripping zone; the first spent catalyst outlet of the first separator 6' is located above the stripping zone of the reactor 1;

[0083] The regenerator 2 comprises a first spent catalyst inlet and a first regenerated catalyst outlet;

[0084] The cracking product outlet of the first riser 4 is communicated with the cracking product inlet of the first separator 6', the upper portion of the first separator 6' is provided with a reaction oil gas outlet, and the lower portion is provided with a first spent catalyst outlet; the first spent catalyst outlet of the first separator 6' is located at the upper portion of the stripping zone in the reactor 1;

[0085] The process gas outlet of the second riser 5' is communicated with the process gas inlet of the reactor 1, and the second spent catalyst outlet of the second riser 5' is communicated with the first catalyst inlet of the first riser 4; the first spent catalyst outlet of the first riser 4 is communicated with the first spent catalyst inlet of the regenerator 2, and the first regenerated catalyst inlet of the regenerator 2 is communicated with the first regenerated catalyst inlet of the first riser 4.

[0086] According to an embodiment of the present disclosure, a coking tank 3 is arranged in the regenerator 2 and is configured to make the first spent catalyst coke into the coking tank 3 for regeneration to obtain the first regenerated catalyst;

[0087] The second riser 5' is sequentially provided with a distribution tank 7', a light hydrocarbon reaction bed 8' and a gas distributor 10' from top to bottom;

[0088] The first spent catalyst outlet of the reactor 1 is communicated with the first spent catalyst inlet of the regenerator 2 via a first spent catalyst inclined pipe 14; the first regenerated catalyst outlet of the regenerator 2 is communicated with the first regenerated catalyst inlet of the first riser 4 via a first regenerated catalyst inclined pipe 12;

[0089] The second spent catalyst outlet of the second riser 5' is communicated with the first catalyst inlet of the first riser 4 via a second spent catalyst inclined pipe 17';

[0090] The first separator 6' includes at least one of a coarse cyclone separator and a fast separator; and the second separator includes at least one of a single-stage cyclone separator and a two-stage cyclone separator.

[0091] The distribution tank 7' makes the second catalyst downwardly distributed and injected from above the light hydrocarbon reaction bed 8'; and the gas distributor 10' makes the light hydrocarbon upwardly distributed and injected from below the light hydrocarbon reaction bed 8'.

[0092] The present disclosure will be further described below by way of examples, but the present disclosure is not limited in any way by the examples.

[0093] Example 1

[0094] The flow of the present embodiment refers to Figure 1 , the heavy oil is atmospheric residue, and the process is as follows Figure 1The experimental process of the system for producing olefins from heavy oil is as follows:

[0095] S1, the heavy oil is sent into the first riser 4 to contact with the first catalyst for catalytic cracking reaction to obtain a cracking product; the first catalyst is CEP-1 catalyst, and the reaction conditions of the catalytic cracking are as follows: the reaction temperature is 580 DEG C, the reaction time is 3 s, the reaction pressure is 0.128 MPag, and the catalyst to oil ratio is 12; the outlet temperature of the first riser 4 is 590 DEG C;

[0096] The cracking product is introduced into the first separator 6' at the outlet of the first riser 4 to perform the first separation to obtain reaction oil gas and first spent catalyst;

[0097] The first spent catalyst is introduced from the lower outlet of the first separator 6' at the outlet of the first riser 4 into the stripping zone of the reactor 1 arranged on the upper part of the first riser 4, is stripped, and is introduced into the regenerator for regeneration to obtain first regenerated catalyst, which is introduced into the first riser 4 for recycling;

[0098] The stripping temperature is 570 DEG C, and the regeneration conditions are as follows: 705 DEG C, 0.165 MPag;

[0099] S2, the second catalyst introduced from the bottom inlet of the second riser 5' via the second regeneration inclined pipe 13' is lifted to above the light hydrocarbon reaction bed 8' in the second riser 5', and at least part of the light hydrocarbon is introduced from below the light hydrocarbon reaction bed 8' to perform catalytic conversion reaction in countercurrent contact to obtain process gas and second spent catalyst; the light hydrocarbon is mixed C4 and light naphtha, the second catalyst is SAPO-34 catalyst, and the catalytic conversion reaction conditions include: the reaction temperature is 645 DEG C, the reaction time is 8 s, the reaction space velocity is 1.5 h -1 , and the catalyst to oil ratio is 20;

[0100] The reaction oil gas obtained by the first separation is introduced from the upper outlet of the first separator 6' into the reactor 1, the process gas from the light hydrocarbon reaction bed 8' is introduced into the lower part of the dilute phase section in the reactor 1, and after being mixed with the reaction oil gas, is sent into the second separator in the upper part of the reactor 1 to perform the second separation, and the obtained oil gas is sent into the fractionating column;

[0101] The second spent catalyst is introduced into the first riser 4 as the first catalyst for recycling, the dilution steam is injected from the dilution steam nozzle 11 in the middle part of the first riser 4, and the introduced second spent catalyst is lifted to the middle upper part of the first riser 4; the product yield of this embodiment is shown in Table 1.

[0102] Example 2

[0103] The flow of this embodiment is shown in Figure 2The heavy oil was atmospheric heavy oil, the experimental process for producing olefins from heavy oil was the same as that of Example 1, except that the process gas from the light hydrocarbon reaction bed 8' entered the reactor 1 via the upper part of the dilute phase section in the reactor 1; the product yield of this example is shown in Table 1.

[0104] Comparative Example 1

[0105] The flow of this comparative example is shown in Figure 3 The feedstock oil used in this comparative example was the same as that used in Example 1, and the system shown in Figure 3 was used for the process of traditional catalytic cracking (FCC), and the details are as follows:

[0106] The catalytic cracking reaction is in the form of a riser plug flow and short contact of catalyst-gas. The feedstock oil is fully mixed, accelerated and stabilized with atomized steam in the feedstock oil nozzle 9, and finally sprayed into the first riser 4 at a certain speed to contact with the high-temperature regenerated catalyst from the regeneration inclined pipe 12, rapidly gasify and react. In the first riser 4, the catalyst flows upward together with the heavy feedstock oil and cracked oil gas, and as the flow proceeds, the macromolecular feedstock oil is cracked into small-molecular liquid products (gasoline and diesel oil) and smaller-molecular light hydrocarbon products (dry gas and liquefied gas). At the same time, the gum and asphaltene in the heavy feedstock oil generate coke which is attached to the catalyst. The first riser 4 outlet uses the first separator 6' to pre-separate the catalyst and the cracked oil gas. Most of the catalyst enters the stripping section at the lower part of the reactor 1, and the oil gas containing a small amount of catalyst enters the single-stage cyclone separator at the top of the reactor 1 via the coarse lift tube and the dilute phase of the reactor 1 for further separation. The spent catalyst is stripped and then enters the regenerator 2 via the spent inclined pipe 14 for continuous coking regeneration, and at the same time, the catalyst is heated and recycled back to the first riser 4. The key process parameters of this comparative example are shown in Table 1, and the product yield is shown in Table 3.

[0107] Table 1: Key Process Parameters:

[0108]

[0109] Comparative Example 2

[0110] The flow of this comparative example is shown in Figure 4 The system shown in Figure 4 was used for the process of producing olefins from heavy oil (CPP), and the details are as follows:

[0111] The combination reaction of the riser and the bed is adopted, two risers are arranged, i.e. the first riser 4 and the second riser 5, the first riser 4 is an inner riser, the feed is fresh raw oil, which is injected by the raw oil nozzle 9, and a large amount of dilution steam is injected to reduce the oil gas partial pressure and increase the catalyst to oil ratio C / O, the outlet temperature is 50-100℃ higher than that of catalytic cracking, the purpose is to crack heavy feed and produce naphtha (gasoline) components, and to provide raw materials for the third reactor bed; the second riser 5 is an outer riser, which is a catalyst riser, and creates suitable reaction conditions for the bed reaction, i.e. increases the overall catalyst activity of the bed, the lifting medium is all the light gasoline and mixed C4 recycled, the outlet temperature of the riser is as high as 620-670℃, the light gasoline and mixed C4 play a lifting role and basically do not convert in the riser; the third reactor is a bed reaction, the products and catalysts of the first riser 4 first reactor and the second riser reactor, as well as the stripping steam, pass through the third reactor, the weight hourly space velocity of the bed is controlled to be 2-4h -1 Propylene is mainly generated in this reaction environment. The key process parameters of the comparative example 1-2 are shown in Table 2, and the product yield is shown in Table 3.

[0112] Table 2: Key process parameters:

[0113]

[0114] As can be seen from the examples 1-2 and the comparative examples 1-2, the method and system for producing low-carbon olefins provided by the present disclosure make the light hydrocarbon and the second catalyst contact in a countercurrent manner to perform a catalytic conversion reaction, avoid the catalytic conversion reaction being affected by the coked catalyst in the first riser, have a higher conversion efficiency, and improve the yield of olefins; the separator is arranged at the outlet of the main riser to quickly separate the reaction oil gas and the spent catalyst, the reaction oil gas stays in the reactor for a short time, secondary cracking is avoided, and the yield of impurities such as methane and hydrogen is reduced; part of the light hydrocarbon is used to lift the second catalyst to the reaction bed, and dilution steam does not need to be injected, thereby reducing the production cost.

[0115] Table 3: Product yield of examples 1-2 and comparative examples 1-2:

[0116]

[0117] Table 3 is the yield result of each product of examples 1-2 and comparative examples 1-2, it can be seen that after using the system for producing low-carbon olefins provided by the present disclosure, the diene yield is obviously improved, the yield of impurities such as methane and hydrogen is reduced (the diene yield is increased by 2.85 percentage points, and the methane and hydrogen are decreased by 2.50 percentage points), and dilution steam does not need to be injected, thereby reducing the production cost.

[0118] The preferred embodiments of the present disclosure are described in detail above with reference to the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0119] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

[0120] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed in the present disclosure.

Claims

1. A process for producing low carbon olefins, characterized by, The method comprises: S1, feeding heavy oil into a first riser (4) to contact a first catalyst for catalytic cracking reaction to obtain a cracking product; introducing the cracking product into a first separator (6') at the outlet of the first riser (4) for first separation to obtain reaction oil gas and first spent catalyst; introducing the first spent catalyst from the lower outlet of the first separator (6') at the outlet of the first riser (4) into the stripping zone of the reactor (1) arranged on the upper part of the first riser (4) for stripping and then into a regenerator (2) for regeneration to obtain first regenerated catalyst; introducing the first regenerated catalyst into the first riser (4) for recycling; S2, lifting the second catalyst introduced from the bottom inlet of the second riser (5') to above the light hydrocarbon reaction bed (8') in the second riser (5'), and performing catalytic conversion reaction from top to bottom with at least part of the light hydrocarbon introduced from below the light hydrocarbon reaction bed (8') to obtain process gas and second spent catalyst; introducing the reaction oil gas obtained by the first separation from the upper outlet of the first separator (6') into the reactor (1), and introducing the process gas from the light hydrocarbon reaction bed (8') into the reactor (1) to mix with the reaction oil gas, and then feeding into the second separator at the upper part of the reactor (1) for second separation, and the obtained oil gas is fed into a fractionating column; the second spent catalyst is introduced into the first riser (4) as the first catalyst for recycling.

2. The method of claim 1, wherein, The method further comprises: injecting dilution steam from the middle part of the first riser (4) through a dilution steam nozzle (11); The weight ratio of the heavy oil to the dilution steam is 1: (0.05-0.3).

3. The method of claim 2, wherein, The weight ratio of the heavy oil to the dilution steam is 1: (0.1-0.18).

4. The method of claim 1, wherein, The process gas from the light hydrocarbon reaction bed (8') is introduced into the upper and / or lower part of the dilute phase section of the reactor (1) to mix with the reaction oil gas, and then fed into the second separator at the upper part of the reactor (1) for second separation, and the obtained oil gas is fed into a fractionating column.

5. The method of claim 1, wherein, The heavy oil comprises at least one of wax oil, residual oil and hydrogenated tail oil; The first catalyst comprises: CEP-1 catalyst and / or ORBIT-3000 catalyst.

6. The method of claim 1, wherein, The light hydrocarbon comprises at least one of mixed C4 light hydrocarbon, light gasoline and propane; The second catalyst comprises: SAPO-34 catalyst.

7. The method of claim 1, wherein, The reaction conditions of the catalytic cracking include: reaction temperature 490-680℃, reaction time 1.5-6s, reaction pressure 50-300kPag, catalyst to oil ratio 6-20; The outlet temperature of the first riser (4) is 500-720℃; The residence time of the reaction oil gas obtained by the first separation and the process gas from the light hydrocarbon reaction bed (8') in the reactor (1) is 1-4s.

8. The method of claim 7, wherein, The reaction conditions of the catalytic cracking include: reaction temperature 540-650℃, reaction time 2-4s, reaction pressure 80-200kPag, catalyst to oil ratio 8-16; The outlet temperature of the first riser (4) is 560-680℃; The residence time of the first separated reaction oil gas in the reactor (1) with the process gas from the light hydrocarbon reaction bed (8') is 1.2-2.5s.

9. The method of claim 1, wherein, In step S2, the light hydrocarbon is introduced into the lower part of the light hydrocarbon reaction bed (8') in the second riser (5') from the second regeneration inclined pipe (13') at the bottom of the second riser (5') after being vaporized by steam and heated to 60-200℃; The conditions of the catalytic conversion reaction include: a reaction space velocity of 0.1-3h -1 ; a reaction temperature of 540-740℃; and a catalyst-oil ratio of 15-30.

10. The method of claim 9, wherein, The conditions of the catalytic conversion reaction include: a reaction space velocity of 0.2-2h -1 ; a reaction temperature of 580-680℃; and a catalyst-oil ratio of 18-25.

11. The method of claim 1, wherein, In step S2, the light hydrocarbon is introduced into the gas distributor (10') from the bottom inlet of the second riser (5'), and is distributed from bottom to top through the gas distributor (10'); At least part of the light hydrocarbon introduced from the second regeneration inclined pipe (13') at the bottom of the second riser (5') is lifted to the distribution tank (7'), and the second catalyst is distributed from top to bottom by the distribution tank (7'); The light hydrocarbon and the second catalyst are countercurrently contacted in the light hydrocarbon reaction bed (8') for catalytic conversion reaction.

12. A system for producing low carbon olefins, characterized by, The system comprises a first riser (4), a reactor (1) sleeved on the upper part of the first riser (4), a second riser (5') arranged in parallel with the first riser (4), and a regenerator (2); The first riser (4) comprises a heavy oil inlet, a first catalyst inlet, a first regenerated catalyst inlet, and a cracking product outlet; the cracking product outlet of the first riser (4) is provided with a first separator (6'), which comprises a cracking product inlet, a reaction oil gas outlet, and a first spent catalyst outlet; the cracking product outlet of the first riser (4) is in communication with the cracking product inlet of the first separator (6'); The reactor (1) comprises a process gas inlet and a first spent catalyst outlet, and the lower part of the reactor (1) is a stripping zone; the first spent catalyst outlet of the first separator (6') is located above the stripping zone of the reactor (1); The regenerator (2) comprises a first spent catalyst inlet, a second catalyst outlet, and a first regenerated catalyst outlet; The first spent catalyst outlet of the reactor (1) is in communication with the first spent catalyst inlet of the regenerator (2); the first regenerated catalyst outlet of the regenerator (2) is in communication with the first regenerated catalyst inlet of the first riser (4); The second riser (5') is provided with a light hydrocarbon reaction bed (8'), which is configured to allow the second catalyst to be countercurrently contacted with at least part of the light hydrocarbon for catalytic conversion reaction; The second riser (5') comprises a light hydrocarbon inlet, a second catalyst inlet, a second spent catalyst outlet, and a process gas outlet; The second spent catalyst outlet of the second riser (5') is in communication with the first catalyst inlet of the first riser (4); the process gas outlet of the second riser (5') is in communication with the process gas inlet of the reactor (1) sleeved on the upper part of the first riser (4); The upper part of the reactor (1) sleeved on the upper part of the first riser (4) is provided with a second separator.

13. The system of claim 12, wherein, The regenerator (2) is provided with a coking drum (3). The first spent catalyst outlet of the reactor (1) is communicated with the first spent catalyst inlet of the regenerator (2) via a first spent catalyst inclined pipe (14); the first regenerated catalyst outlet of the regenerator (2) is communicated with the first regenerated catalyst inlet of the first riser (4) via a first regenerated catalyst inclined pipe (12); The second catalyst inlet of the second riser (5') is communicated with the second catalyst outlet of the regenerator (2) via a second regenerated catalyst inclined pipe (13'); The second spent catalyst outlet of the second riser (5') is communicated with the first catalyst inlet of the first riser (4) via a second spent catalyst inclined pipe (17'); The first separator (6') comprises at least one of a coarse cyclone separator and a fast separator; The second separator comprises at least one of a single-stage cyclone separator and a two-stage cyclone separator; The distribution groove (7'), the light hydrocarbon reaction bed layer (8') and the gas distributor (10') are sequentially arranged in the second riser (5') from top to bottom; The distribution groove (7') distributes the second catalyst downward and injects from above the light hydrocarbon reaction bed layer (8'); the gas distributor (10') distributes the light hydrocarbon upward and injects from below the light hydrocarbon reaction bed layer (8').

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