A method for cracking optimization of raffinate oil

Abstract

The application provides a cracking optimization method of raffinate oil, comprising the following steps: (1) performing cracking experiment test and steam cracking simulation on cracking raw materials, wherein the cracking raw materials comprise naphtha and raffinate oil, and the upper limit of the mixing of the raffinate oil in the cracking raw materials is determined according to the running state and running cycle of the device in the cracking experiment test; (2) collecting test product data in the cracking experiment test, and checking simulation product data of the steam cracking simulation by using the test product data to obtain checked simulation product data; (3) using the checked simulation product data, taking the upper limit of the mixing of the raffinate oil as one of boundary conditions, establishing a benefit maximization model, and solving the benefit maximization cracking operation condition by using cracking raw material physical properties, cracking raw material price, cracking product price and cracking operation data, wherein the cracking operation condition comprises the mixing ratio of the raffinate oil, and the economic benefit optimization and the profit increase can be realized.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to an optimization method for cracking raffinate. Background Technology

[0002] The petrochemical industry is a pillar industry of the national economy. Petrochemical products (referred to as petrochemical products) are widely used in all sectors of the national economy and play a vital role in promoting national economic development. Most intermediate and petrochemical products are based on low-carbon olefins and aromatics. The raw materials used in the production of low-carbon olefins (ethylene, propylene, butadiene) and aromatics (benzene, toluene, xylene) account for approximately three-quarters of the total raw materials consumed in petrochemical production. Among these, low-carbon olefins are the most fundamental and important raw materials in the petrochemical industry, and their production mainly relies on ethylene plants. Ethylene plants consist of cracking furnaces and separation units, with the cracking furnace being the leading production unit.

[0003] With the continuous growth of ethylene production capacity, the supply of high-quality cracking feedstocks (such as light hydrocarbons and naphtha) is becoming increasingly tight, and finding and developing new alternative feedstocks has become an important research direction for the industry. Rag oil is a byproduct of chemical production processes, mainly composed of alkanes and cycloalkanes, and theoretically can be used as a cracking feedstock.

[0004] However, in existing technologies, if raffinate is directly fed into a conventional cracking furnace for cracking, its unique composition can easily lead to excessively rapid coking in the furnace tubes, severely impacting the unit's operating cycle. Simultaneously, the yields of target olefins such as ethylene and propylene are lower than those of traditional high-quality feedstocks, resulting in poor economic efficiency. Consequently, no unit in actual production uses raffinate as a cracking feedstock.

[0005] Therefore, optimizing the cracking process of raffinate to enable its efficient and stable application in existing ethylene plants and improve the yield of high-value olefins is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an optimization method for the cracking of raffinate. By combining systematic experiments and simulations, the optimal blending scheme for raffinate is determined safely and efficiently, enabling seamless integration with traditional cracking units, effectively reducing raw material costs, and maximizing production efficiency.

[0007] To achieve this objective, the present invention adopts the following technical solution: This invention provides a method for optimizing the cracking of raffinate, the method comprising the following steps: (1) Conduct cracking experiments and steam cracking simulations on the cracking feedstock, which includes naphtha and raffinate. Based on the operating status and operating cycle of the device in the cracking experiment, determine the upper limit of the mixing of raffinate in the cracking feedstock.

[0008] (2) Collect the test product data in the pyrolysis experiment and use the test product data to verify the simulated product data of the steam pyrolysis simulation to obtain the verified simulated product data.

[0009] (3) Using the verified simulated product data, with the upper limit of the blending of raffinate as one of the boundary conditions, establish a benefit maximization model, and use the physical properties of the cracking feedstock, the price of the cracking feedstock, the price of the cracking products and the cracking operation data to solve the cracking operation conditions that maximize benefits. The cracking operation conditions include the blending ratio of raffinate.

[0010] Adding raffinate to existing pyrolysis feedstocks presents numerous challenges, including processing methods, proportions, and efficiency. This invention combines pyrolysis experiments with steam pyrolysis simulation, avoiding the risks of direct processing with the equipment, reducing testing uncertainties, and shortening testing time. Furthermore, by verifying the simulated product using experimental test data, a benefit-maximizing model is constructed to determine the blending ratio of raffinate and pyrolysis operating conditions, thereby improving pyrolysis efficiency.

[0011] Preferably, before step (1), the cracking optimization method further includes: conducting preliminary steam cracking simulations on raffinate oil with different olefin contents to obtain the simulated product distribution and simulated coking cycle of the raffinate oil cracking process under different olefin contents. Based on the simulated product distribution and simulated coking cycle, the upper limit of the olefin content in the cracking feedstock is determined.

[0012] Preferably, the input data for the preliminary steam cracking simulation includes the PIONA value of the raffinate oil.

[0013] Preferably, the blending ratio of raffinate in the cracking feedstock is adjusted so that the olefin content in the cracking feedstock is within the upper limit of the olefin content in the cracking feedstock.

[0014] Preferably, the blending ratio of the residual oil in the cracking feedstock in the cracking experiment test and steam cracking simulation in step (1) is in the range of 5~30wt%.

[0015] Preferably, the pyrolysis feedstock in the pyrolysis experimental test and steam pyrolysis simulation includes a first pyrolysis feedstock, a second pyrolysis feedstock, and a third pyrolysis feedstock.

[0016] Preferably, the blending ratio of raffinate in the second pyrolysis feedstock is 5-10 wt% higher than that in the first pyrolysis feedstock.

[0017] Preferably, the blending ratio of raffinate in the third cracking feedstock is 5-10 wt% higher than that in the second cracking feedstock.

[0018] Preferably, the blending ratio of raffinate in the first cracking feedstock is 5-10 wt%.

[0019] Preferably, the blending ratio of raffinate in the second cracking feedstock is 10~20wt%.

[0020] Preferably, the blending ratio of raffinate in the third cracking feedstock is 20-30 wt%.

[0021] Preferably, the operating status of the device in step (1) includes the propylene tower processing capacity, the butadiene unit processing capacity, and the fuel gas balance capacity.

[0022] Preferably, the propylene tower processing capacity includes the maximum feed rate of the propylene tower and the separation efficiency of the propylene tower; Preferably, the separation efficiency of the propylene tower includes a propylene purity of ≥99.5wt% in the propylene discharge from the top of the propylene tower and a propylene content of ≤10wt% in the propane discharge from the bottom of the propylene tower.

[0023] Preferably, the butadiene unit processing capacity includes the maximum feed rate of the butadiene unit and the upper limit of butadiene content in the butadiene unit feed.

[0024] Preferably, the butadiene content in the butadiene unit feed is ≤50%.

[0025] Preferably, the fuel gas balance capacity includes: the fuel gas generated from pyrolysis is ≤ the sum of the maximum consumption of downstream fuel gas and the vented fuel gas.

[0026] Preferably, the volume ratio of the maximum consumption of the vented fuel gas and the downstream fuel gas to the sum of the vented fuel gas is ≤5%.

[0027] Preferably, the upper limit for blending residual oil in the cracking feedstock is determined by the decrease in the operating cycle time of the device being ≤5%.

[0028] Preferably, the test product data includes test product yield data.

[0029] Preferably, the test product yield data includes ethylene test yield data, propylene test yield data, and butadiene test yield data.

[0030] Preferably, the simulated product data includes simulated product yield data.

[0031] Preferably, the simulated product yield data includes simulated yield data for the entire product range, from hydrogen to fuel oil.

[0032] Preferably, the simulated product yield data includes simulated yield data for ethylene, simulated yield data for propylene, and simulated yield data for butadiene.

[0033] Preferably, the verification includes adding a correction coefficient to the model of the steam cracking simulation so that the deviation between the simulated product data and the test product data after verification is within the allowable deviation range.

[0034] Preferably, the allowable deviation is ≤1%.

[0035] Preferably, the benefit maximization model is: Target value = Product output × Product price - Raw material consumption × Raw material price - Utility consumption × Utility price

[0036] Preferably, the solution is obtained using a linear programming model.

[0037] Preferably, the solution process involves adjusting the physical properties of the pyrolysis feedstock, the price of the pyrolysis feedstock, the price of the pyrolysis products, and the pyrolysis operating conditions.

[0038] Preferably, the cracking optimization method further includes: calculating the break-even purchase price of raffinate and determining a procurement strategy.

[0039] Preferably, the calculation of the break-even purchase price of the raked oil includes: break-even purchase price of raked oil = (product revenue from raked oil - processing cost of raked oil) / purchase quantity of raked oil.

[0040] Preferably, the break-even purchase price of the raffinate is checked based on the different revenues of the raffinate under different cracking operation conditions, and the procurement strategy is optimized.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects: The pyrolysis optimization method for raffinate provided by this invention enables the pyrolysis of raffinate using a traditional pyrolysis unit. This not only does not affect the operation of the traditional pyrolysis unit, but also significantly improves economic efficiency and expands the economic benefits of the pyrolysis production process. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the pyrolysis production device system provided in an embodiment of the present invention.

[0043] 1. Cracking furnace; 2. Ethylene tower; 3. Propylene tower; 4. Quenching oil tower; 5. Quenching water tower; 6. First compression unit; 7. Alkali washing unit; 8. Drying unit; 9. High-pressure partial propane removal unit; 10. Low-pressure partial propane removal unit; 11. Three-stage C2 hydrogenation unit; 12. Butadiene unit; 13. First cold box; 14. Demethylation tower; 15. Partial ethane removal tower; 16. Third compressor; 17. Expander. Detailed Implementation

[0044] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0045] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0046] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] Those skilled in the art should understand that the present invention necessarily includes the necessary pipelines, conventional valves and general pump equipment for achieving complete process, but the above content is not the main inventive point of the present invention. Those skilled in the art can add layouts based on process flow and equipment structure selection, and the present invention does not make any special requirements or specific limitations in this regard.

[0048] It is worth noting that the pyrolysis production apparatus system targeted by this invention is prior art in the field, and can be applied to any existing pyrolysis production apparatus system, such as... Figure 1 As shown, the cracking production unit system includes a cracking furnace, an ethylene tower, and a propylene tower. Ethylene is obtained from the top of the ethylene tower and ethane from the bottom; propylene is obtained from the top of the propylene tower and propane from the bottom.

[0049] Furthermore, the pyrolysis production unit system also includes: a quench oil-water system, a first compression unit, an alkaline washing unit, an air-drying unit, a liquid-drying unit, a high-pressure partial propane removal unit, a low-pressure partial propane removal unit, a second compression unit, and a three-stage C2 hydrogenation unit. Along the material conveying direction, the pyrolysis furnace, the quench oil-water system, the first compression unit, and the alkaline washing unit are sequentially connected. The alkaline washing unit is connected to both the air-drying unit and the liquid-drying unit. The outlets of both the air-drying unit and the liquid-drying unit are connected to the high-pressure partial propane removal unit. The top outlet of the high-pressure partial propane removal unit is connected to the second compression unit, and the bottom outlet of the high-pressure partial propane removal unit is connected to the low-pressure partial propane removal unit. The second compression unit is connected to the three-stage C2 hydrogenation unit.

[0050] Furthermore, the cracking production unit system also includes a butadiene unit, the bottom outlet of the low-pressure partial propane removal unit is connected to the butadiene unit, and the top removal tower is provided with a mixed C4 outlet and an outlet for components above C5.

[0051] Furthermore, the cracking production unit system also includes: a first cold box, a propylene unit, an ethylene unit, a thermally integrated distillation system, a third compressor, an expander, a first demethylation tower, a second demethylation tower, and a partial deethane removal tower. The material outlets of the three-stage C2 hydrogenation unit are connected to the material inlets of the first cold box and the first demethylation tower, respectively. The top outlet of the low-pressure partial propane removal unit is connected to the material inlet of the propylene tower. The propylene generator and the ethylene generator are connected to the first cold box and the integrated thermal distillation system, respectively. The material outlet of the first cold box is connected to the first demethylation tower and the integrated thermal distillation system, respectively. The methane and hydrogen outlets of the integrated thermal distillation system are connected to the third compressor, which discharges fuel gas (hydrogen and methane). The cryogenic material outlet of the integrated thermal distillation system is connected to the second demethylation tower, and the top outlet of the first demethylation tower is connected to the second demethylation tower. The top outlet of the second demethylation tower is expanded through the integrated thermal distillation system, the first cold box, and the expander to obtain methane product. The bottom outlet of the second demethylation tower is connected to the ethylene tower, the top discharge of the partial ethane removal tower is connected to the ethylene tower, and the bottom discharge of the partial ethane removal tower is connected to the propylene tower.

[0052] This invention provides a method for optimizing the cracking of raffinate, the method comprising the following steps: (1) Conduct cracking experiments and steam cracking simulations on the cracking feedstock, which includes naphtha and raffinate. Based on the operating status and operating cycle of the device in the cracking experiment, determine the upper limit of the mixing of raffinate in the cracking feedstock.

[0053] (2) Collect the test product data in the pyrolysis experiment and use the test product data to verify the simulated product data of the steam pyrolysis simulation to obtain the verified simulated product data.

[0054] (3) Using the verified simulated product data, with the upper limit of the blending of raffinate as one of the boundary conditions, establish a benefit maximization model, and use the physical properties of the cracking feedstock, the price of the cracking feedstock, the price of the cracking products and the cracking operation data to solve the cracking operation conditions that maximize benefits. The cracking operation conditions include the blending ratio of raffinate.

[0055] Rag oil is an optional cracking feedstock. However, due to its low ethylene yield, high fuel gas production, and high olefin content, there are limitations in its processing when combined with existing cracking units, as well as questions about whether the efficiency of the processed products can be increased.

[0056] Adding raffinate to existing pyrolysis feedstocks presents numerous challenges, including processing methods, proportions, and efficiency. This invention combines pyrolysis experiments with steam pyrolysis simulation, avoiding the risks of direct processing with the equipment, reducing testing uncertainties, and shortening testing time. Furthermore, by verifying the simulated product using experimental test data, a benefit-maximizing model is constructed to determine the blending ratio of raffinate and pyrolysis operating conditions, thereby improving pyrolysis efficiency.

[0057] In some embodiments, the naphtha in the cracking feedstock includes straight-run naphtha, light naphtha, and coking refined naphtha, and the naphtha is mixed with the raffinate before entering the feedstock storage tank; purchased naphtha may also be used in the feedstock storage tank.

[0058] This invention does not impose any special restrictions on the flow ratio of straight-run naphtha, light naphtha, and coking refined naphtha in naphtha. The ratio can be well known to those skilled in the art or based on the optimized results.

[0059] In some embodiments, the cracking products after the cracking reaction of the feedstock include any one or a combination of at least two of the following: hydrogen, ethane, ethylene, propane, propylene, mixed C4, butadiene, cracked gasoline, cracked diesel, or cracked fuel oil.

[0060] In some embodiments, prior to step (1), the cracking optimization method further includes: performing preliminary steam cracking simulations on raffinate oil with different olefin contents to obtain simulated product distribution and simulated coking cycle of raffinate oil cracking processing under different olefin contents. Based on the simulated product distribution and simulated coking cycle, the upper limit of olefin content in the cracking feedstock is determined.

[0061] Generally, by comparing the results of coking simulation, it has been confirmed that an olefin content of no more than 3% (wt) will not shorten the operating cycle of the cracking furnace.

[0062] In some embodiments, the olefin content of the raffinate is 2 to 8 wt%, for example, it can be 2 wt%, 2.7 wt%, 3.4 wt%, 4 wt%, 4.7 wt%, 5.4 wt%, 6 wt%, 6.7 wt%, 7.4 wt%, or 8 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In some embodiments, the isoalkane content of the raffinate is 58-65 wt%, for example, it can be 58 wt%, 58.8 wt%, 59.6 wt%, 60.4 wt%, 61.2 wt%, 61.9 wt%, 62.7 wt%, 63.5 wt%, 64.3 wt%, or 65 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] In some implementations, the input data for the preliminary steam cracking simulation includes the PIONA value of the raffinate oil.

[0065] The explanation provided is that the PIONA value refers to the mass percentage of alkanes, isoalkanes, alkenes, cycloalkanes, and aromatics in the oil product. Here, P represents alkanes, I represents isoalkanes, O represents alkenes, N represents cycloalkanes, and A represents aromatics.

[0066] This invention uses the PIONA value of the raffinate oil for simulation calculation. Compared with full component analysis, it does not require outsourced processing, is less time-consuming and lower in cost, and the calculation result using the PIONA value has an error within 1.5% compared with the full component analysis. For example, it can be 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.5% or 0.4%, etc., which is within an acceptable range.

[0067] Generally, conventional naphtha contains 30-45 wt% n-alkanes (P), 35-45 wt% isoalkanes (I), 0.1-1 wt% olefins (O), 10-20 wt% cycloalkanes (N), and 2-8 wt% aromatics (A).

[0068] In some embodiments, the blending ratio of raffinate in the cracking feedstock is adjusted so that the olefin content in the cracking feedstock is within the upper limit of the olefin content in the cracking feedstock.

[0069] In some embodiments, the blending ratio of the residual oil in the cracking feedstock in the cracking experiment test and steam cracking simulation described in step (1) is in the range of 5~30wt%, for example, it can be 5wt%, 8wt%, 11wt%, 14wt%, 17wt%, 19wt%, 22wt%, 25wt%, 28wt% or 30wt%, etc., but is not limited to the listed values. Other unlisted values ​​in this range are also applicable.

[0070] In some embodiments, the pyrolysis feedstock in the pyrolysis experimental test and steam pyrolysis simulation includes a first pyrolysis feedstock, a second pyrolysis feedstock, and a third pyrolysis feedstock.

[0071] In some embodiments, the blending ratio of raffinate in the second cracking feedstock is 5 to 10 wt% higher than that in the first cracking feedstock. For example, it can be 5 wt%, 5.6 wt%, 6.2 wt%, 6.7 wt%, 7.3 wt%, 7.8 wt%, 8.4 wt%, 8.9 wt%, 9.5 wt%, or 10 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] In some embodiments, the blending ratio of raffinate in the third cracking feedstock is 5 to 10 wt% higher than that in the second cracking feedstock. For example, it can be 5 wt%, 5.6 wt%, 6.2 wt%, 6.7 wt%, 7.3 wt%, 7.8 wt%, 8.4 wt%, 8.9 wt%, 9.5 wt%, or 10 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] In some embodiments, the blending ratio of raffinate in the first cracking feedstock is 5-10 wt%. Generally, a blending ratio of 10 wt% is preferred. Starting the test with a 10% blending ratio is based on the fact that the olefin content in the feedstock after blending is 1.5%, which is the upper limit for conventional naphtha and will not have a significant impact on furnace tube coking. The unit has relevant processing experience, facilitating testing. Simultaneously, the impact of raffinate on the overall product composition can be observed. Selecting a lower blending ratio makes it difficult to observe the impact of raffinate; for example, a 1% blending ratio may cause changes to be overwhelmed by changes in other parameters, making data collection ineffective.

[0074] In some embodiments, the blending ratio of raffinate in the second cracking feedstock is 10-20 wt%, for example, it can be 10 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] In some embodiments, the blending ratio of raffinate in the third cracking feedstock is 20-30 wt%, for example, it can be 20 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] In some embodiments, the operating status of the apparatus in step (1) includes the propylene tower processing capacity, butadiene unit processing capacity, and fuel gas balance capacity.

[0077] In this invention, raffinate is added to the cracking furnace as a feedstock, resulting in an increase in propylene production compared to when raffinate is not present. Therefore, it is necessary to optimize the operating conditions of the propylene tower. Factors such as the overall butadiene unit processing capacity and fuel gas balance also need to be considered to adjust the proportion of cracking feedstock.

[0078] In some embodiments, the propylene tower processing capacity includes the maximum feed rate and the separation efficiency of the propylene tower. The maximum feed rate is not specifically limited and can be specifically defined according to different production units; for example, in some plants, the maximum feed rate is 73 tons / hour.

[0079] In some embodiments, the separation efficiency of the propylene tower includes a propylene purity of ≥99.5wt% in the propylene discharge from the top of the propylene tower and a propylene content of ≤10wt% in the propane discharge from the bottom of the propylene tower.

[0080] In some embodiments, the butadiene unit's processing capacity includes the maximum feed rate of the butadiene unit and the upper limit of butadiene content in the feed. The maximum feed rate of the butadiene unit is not specifically limited and can be specifically limited according to different production facilities; for example, in some plants, the maximum processing capacity of the butadiene unit is 46 tons / hour.

[0081] In some embodiments, the butadiene content in the butadiene unit feed is ≤50%.

[0082] In some embodiments, the fuel gas balance capability includes: the fuel gas produced by cracking is ≤ the sum of the maximum consumption of downstream fuel gas and the vented fuel gas.

[0083] In some implementations, the volume ratio of the vented fuel gas to the maximum consumption of downstream fuel gas and the sum of the vented fuel gas volumes is ≤5%. Ideally, fuel gas venting should be minimized to avoid any loss of fuel gas. The maximum consumption of downstream fuel gas is not specifically limited but can be determined based on different production units; for example, in some plants, the maximum consumption of downstream fuel gas may be 18 tons / hour.

[0084] In some implementations, the upper limit for blending raffinate in the cracking feedstock is determined by a decrease of ≤5% in the duration of the device's operating cycle.

[0085] The unit operating cycle refers to the duration during which the unit can operate continuously after startup. During operation, coking occurs inside the pyrolysis furnace. When the amount of coking is large, it leads to a decrease in the pyrolysis efficiency of the furnace, necessitating shutdown for decoking. This invention sets the upper limit for blending raffinate oil at a decrease of ≤5% from the normal operating cycle duration, thereby reducing frequent start-ups and shutdowns and improving production efficiency.

[0086] In some implementations, the test product data includes test product yield data.

[0087] In some embodiments, the test product yield data includes ethylene test yield data, propylene test yield data, and butadiene test yield data.

[0088] In some implementations, the simulated product data includes simulated product yield data.

[0089] In some implementations, the simulated product yield data includes simulated yield data for the entire product range, from hydrogen to fuel oil.

[0090] Preferably, the simulated product yield data mainly includes the yield data of high-value products such as ethylene, propylene, and butadiene, which are of particular interest.

[0091] In some embodiments, the verification includes adding a correction factor to the model of the steam cracking simulation so that the deviation between the verified simulated product data and the test product data is within the allowable deviation range.

[0092] In some implementations, the allowable deviation is ≤1%, for example, it can be 1%, 0.98%, 0.96%, 0.95%, 0.92%, 0.9%, 0.88%, 0.87%, 0.85%, 0.82%, or 0.8%, etc.

[0093] In some implementations, the benefit maximization model is: Target value = Product output × Product price - Raw material consumption × Raw material price - Utility consumption × Utility price

[0094] In some implementations, the solution is obtained using a linear programming model.

[0095] The linear programming model in this invention employs sensitivity analysis across multiple scenarios. By adjusting the prices of cracking products and downstream products, it simulates the revenue generated by raking oil under different market conditions. It also simulates the differences in raking oil revenue under different operating conditions of the unit, thereby more accurately determining the break-even price and procurement strategy.

[0096] In some implementations, the solution involves adjusting the physical properties of the pyrolysis feedstock, the price of the pyrolysis feedstock, the price of the pyrolysis products, and the pyrolysis operating conditions.

[0097] In some implementations, the pyrolysis feedstock properties include PIONA value and distillation range.

[0098] In some implementations, the cracking optimization method further includes: calculating the break-even purchase price of raffinate and determining a procurement strategy.

[0099] In some implementations, the break-even purchase price of the raked oil is calculated as follows: Break-even purchase price of raked oil = (Product revenue from raked oil - Processing cost of raked oil) / Purchase quantity of raked oil.

[0100] In some implementations, the break-even purchase price of the raffinate is checked and the procurement strategy is optimized based on the different revenues of the raffinate under different cracking operating conditions.

[0101] The following detailed description uses specific examples.

[0102] Example 1 This embodiment provides a method for optimizing the cracking of raffinate oil. This method is applied to the following cracking production unit system: Figure 1 As shown, the cracking production unit system includes a cracking furnace, an ethylene tower, and a propylene tower. Ethylene is obtained from the top of the ethylene tower and ethane from the bottom; propylene is obtained from the top of the propylene tower and propane from the bottom.

[0103] The pyrolysis production unit system further includes: a quench oil-water system, a first compression unit, an alkaline washing unit, a drying unit, a high-pressure partial propane removal unit, a low-pressure partial propane removal unit, a second compression unit, and a three-stage C2 hydrogenation unit. Along the material conveying direction, the pyrolysis furnace, the quench oil-water system, the first compression unit, and the alkaline washing unit are sequentially connected. The quench oil-water system includes a quench oil tower and a quench water tower connected sequentially. The alkaline washing unit is connected to the drying unit, which includes an air-drying unit and a liquid-drying unit. The alkaline washing unit is connected to both the air-drying unit and the liquid-drying unit. The outlets of both the air-drying unit and the liquid-drying unit are connected to the high-pressure partial propane removal unit. The top outlet of the high-pressure partial propane removal unit is connected to the second compression unit, and the bottom outlet of the high-pressure partial propane removal unit is connected to the low-pressure partial propane removal unit. The second compression unit is connected to the three-stage C2 hydrogenation unit.

[0104] The cracking production unit system also includes a butadiene unit, the bottom outlet of the low-pressure partial propane removal unit is connected to the butadiene unit, and the top removal tower is provided with a mixed C4 outlet and an outlet for components above C5.

[0105] The cracking production unit system also includes: a first cold box, a propylene unit, an ethylene unit, a thermal integrated distillation system, a third compressor, an expander, a first demethylation tower, a second demethylation tower, and a partial deethane removal tower. The material outlets of the three-stage C2 hydrogenation unit are connected to the material inlets of the first cold box and the first demethylation tower, respectively. The top outlet of the low-pressure partial propane removal unit is connected to the material inlet of the propylene tower. The propylene generator and the ethylene generator are connected to the first cold box and the integrated thermal distillation system, respectively. The material outlet of the first cold box is connected to the first demethylation tower and the integrated thermal distillation system, respectively. The methane and hydrogen outlets of the integrated thermal distillation system are connected to the third compressor, which discharges fuel gas (hydrogen and methane). The cryogenic material outlet of the integrated thermal distillation system is connected to the second demethylation tower, and the top outlet of the first demethylation tower is connected to the second demethylation tower. The top outlet of the second demethylation tower is expanded through the integrated thermal distillation system, the first cold box, and the expander to obtain methane product. The bottom outlet of the second demethylation tower is connected to the ethylene tower, the top discharge of the partial ethane removal tower is connected to the ethylene tower, and the bottom discharge of the partial ethane removal tower is connected to the propylene tower.

[0106] Specifically, the pyrolysis optimization method includes the following steps: S1. Using the PIONA values ​​of raffinate oils with different olefin contents (approximately 8 wt% olefins and 62 wt% isoalkanes in the raffinate oil from Huizhou Refinery; 6 wt% olefins and 65 wt% isoalkanes in the raffinate oil from Gulei Tenglong Refinery) as input data, preliminary steam cracking simulations were conducted to obtain the simulated product distribution and simulated coking cycle of the raffinate oil cracking process under different olefin contents. Based on the simulated product distribution and simulated coking cycle, the upper limit of olefin content in the cracking feedstock was determined.

[0107] By comparing the coking simulation results, it was confirmed that the olefin content is not higher than 3% (wt), which does not shorten the operation cycle of the cracking furnace.

[0108] S2. Based on the preliminary steam cracking simulation results, the proportion of raffinate oil in the total feed to the cracking furnace is determined to be 10wt%, 20wt%, and 30wt%. Cracking experiments and steam cracking simulations are conducted on the cracking feedstocks with raffinate oil proportions within these ranges (the remainder being naphtha). Based on the unit's operating conditions and operating cycle during the cracking experiments, the upper limit for the blending of raffinate oil in the cracking feedstock is determined. The unit's operating conditions include the separation status of the propylene tower, the processing capacity of the butadiene unit, and the fuel gas balance.

[0109] Specifically, with a blending ratio of 10%, the initial test was based on the premise that the olefin content in the feed after blending was 1.5%, which is the upper limit of conventional naphtha and would not have a significant impact on coking in the cracking furnace. The unit had relevant processing experience, which facilitated the testing. At the same time, the impact of raffinate on the overall product composition could be observed. Selecting a lower blending ratio would make it difficult to observe the impact of raffinate. For example, a blending ratio of 1% might cause the changes to be overwhelmed by changes in other parameters, making it impossible to collect data effectively.

[0110] When a 20% blending ratio is used, the olefin content is around 2%, which poses a challenge to the operation of the unit. If a significant impact is found during processing, the blending ratio will be reduced to 15%, and operation will continue to be monitored.

[0111] The unit briefly operated at a 3% olefin content (for approximately 10 days) under abnormal conditions, and issues such as shortened operating cycles and processing limitations were observed. Therefore, a 30% blending ratio was set as the maximum test blending ratio.

[0112] S3. Collect the test product data from the pyrolysis experiment and use the test product data to verify the simulated product data of the steam pyrolysis simulation to obtain verified simulated product data. The verification includes adding a correction coefficient to the steam pyrolysis simulation model so that the deviation between the verified simulated product data and the test product data is within the allowable deviation ≤1%. Both the simulated product data and the test product data are yield data for ethylene, propylene, and butadiene products.

[0113] S4. Calculate the break-even purchase price of the raffinate oil. The calculation of the break-even purchase price of the raffinate oil includes: Break-even purchase price of raffinate oil = (Product revenue from raffinate oil - Processing cost of raffinate oil) / Purchase quantity of raffinate oil. Using the verified simulated product data, and taking the upper limit of raffinate oil blending as one of the boundary conditions, establish a benefit maximization model. The benefit maximization model is as follows: Target value = Product output × Product price - Raw material consumption × Raw material price - Utility consumption × Utility price

[0114] A linear programming model was used to solve for the optimal cracking operation conditions that maximized benefits by utilizing the physical properties of the cracking feedstock, the price of the cracking feedstock, the price of the cracking products, and the cracking operation data. The cracking operation conditions included the blending ratio of the raffinate and the processing temperature of the cracking furnace.

[0115] The specific model parameter settings and adjustments are as follows: When solving linear programming problems, the properties of P, N, and A in the PIONA model can be adjusted to simulate the differences in properties of different raw material mixtures. Ultimately, the model results will reflect the differences in benefits brought about by the blending of different raw materials.

[0116] For raw material prices, different tiered pricing can be set to reflect the discount differences for different purchase volumes and different sources.

[0117] Different pricing systems can be set for cracked products, based on different naphtha market benchmarks, to reflect price differences under strong and weak market conditions.

[0118] Different load limits can be set for the devices and equipment in the model, reflecting the differences in processing capacity under different operating cycles.

[0119] Specifically, the current cost of purchasing residual oil is 60-70 yuan / ton lower than that of naphtha (taking 60 yuan / ton as an example). The total product revenue is 31 yuan / ton lower than that of naphtha. Therefore, the additional processing revenue per ton is: 60-31=29 yuan / ton. Based on an annual processing capacity of 6 million tons and a blending ratio of 10%, the additional revenue generated annually is 29×600×0.1=17.4 million yuan.

[0120] This shows that most cracking units do not consider raffinate as a suitable cracking feedstock, resulting in abundant raffinate resources on the market at relatively low prices. This invention combines SPYRO model simulation and actual unit measurements in the optimization of raffinate processing, avoiding processing risks, reducing testing uncertainties, and shortening testing time. Furthermore, by applying the measured data to the LP model (linear programming model), a suitable processing scheme and purchase price were determined, ultimately achieving a significant improvement in cracking efficiency and demonstrating broad application prospects.

[0121] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for optimizing the cracking of raffinate, characterized in that, The pyrolysis optimization method includes the following steps: (1) Conduct cracking experiments and steam cracking simulations on the cracking feedstock, which includes naphtha and raffinate. Determine the upper limit of raffinate in the cracking feedstock based on the operating status and operating cycle of the device during the cracking experiments. (2) Collect the test product data in the pyrolysis experiment and use the test product data to verify the simulated product data of the steam pyrolysis simulation to obtain the verified simulated product data; (3) Using the verified simulated product data, with the upper limit of the blending of raffinate as one of the boundary conditions, establish a benefit maximization model, and use the physical properties of the cracking feedstock, the price of the cracking feedstock, the price of the cracking products and the cracking operation data to solve the cracking operation conditions that maximize benefits. The cracking operation conditions include the blending ratio of raffinate.

2. The pyrolysis optimization method according to claim 1, characterized in that, Before step (1), the cracking optimization method further includes: conducting preliminary steam cracking simulation on raffinate with different olefin contents to obtain the simulated product distribution and simulated coking cycle of raffinate cracking processing under different olefin contents; and determining the upper limit of olefin content in the cracking feedstock based on the simulated product distribution and simulated coking cycle. Preferably, the input data for the preliminary steam cracking simulation includes the PIONA value of the raffinate oil.

3. The pyrolysis optimization method according to claim 1 or 2, characterized in that, The blending ratio of raffinate in the cracking feedstock is adjusted so that the olefin content in the cracking feedstock is within the upper limit of the olefin content in the cracking feedstock. Preferably, the blending ratio of the raffinate in the pyrolysis experimental test and steam pyrolysis simulation in step (1) is in the range of 5~30 wt%; Preferably, the pyrolysis feedstock in the pyrolysis experimental test and steam pyrolysis simulation includes a first pyrolysis feedstock, a second pyrolysis feedstock, and a third pyrolysis feedstock; Preferably, the blending ratio of raffinate in the second cracking feedstock is 5-10 wt% higher than the blending ratio of raffinate in the first cracking feedstock; Preferably, the blending ratio of raffinate in the third cracking feedstock is 5-10 wt% higher than the blending ratio of raffinate in the second cracking feedstock. Preferably, the blending ratio of raffinate in the first cracking feedstock is 5-10 wt%; Preferably, the blending ratio of raffinate in the second cracking feedstock is 10-20 wt%. Preferably, the blending ratio of raffinate in the third cracking feedstock is 20-30 wt%.

4. The pyrolysis optimization method according to any one of claims 1 to 3, characterized in that, The operating status of the device in step (1) includes the propylene tower processing capacity, butadiene unit processing capacity, and fuel gas balance capacity. Preferably, the propylene tower processing capacity includes the maximum feed rate of the propylene tower and the separation efficiency of the propylene tower; Preferably, the separation efficiency of the propylene tower includes a propylene purity of ≥99.5wt% in the propylene discharge from the top of the propylene tower and a propylene content of ≤10wt% in the propane discharge from the bottom of the propylene tower. Preferably, the butadiene unit processing capacity includes the maximum feed rate of the butadiene unit and the upper limit of butadiene content in the butadiene unit feed; Preferably, the butadiene content in the butadiene unit feed is ≤50%; Preferably, the fuel gas balance capacity includes: the fuel gas produced by cracking is ≤ the sum of the maximum consumption of downstream fuel gas and the vented fuel gas; Preferably, the upper limit for blending residual oil in the cracking feedstock is determined by the decrease in the operating cycle time of the device being ≤5%.

5. The pyrolysis optimization method according to any one of claims 1 to 4, characterized in that, The test product data includes test product yield data; Preferably, the test product yield data includes ethylene test yield data, propylene test yield data, and butadiene test yield data; Preferably, the simulated product data includes simulated product yield data; Preferably, the simulated product yield data includes simulated yield data for the entire product range, from hydrogen to fuel oil.

6. The pyrolysis optimization method according to any one of claims 1 to 5, characterized in that, The verification includes adding correction coefficients to the model of the steam cracking simulation so that the deviation between the simulated product data and the test product data after verification is within the allowable deviation. Preferably, the allowable deviation is ≤1%.

7. The pyrolysis optimization method according to any one of claims 1 to 6, characterized in that, The benefit maximization model is as follows: Target value = Product output × Product price - Raw material consumption × Raw material price - Utility consumption × Utility price 8. The pyrolysis optimization method according to any one of claims 1 to 7, characterized in that, The solution is obtained using a linear programming model. Preferably, the solution process involves adjusting the physical properties of the pyrolysis feedstock, the price of the pyrolysis feedstock, the price of the pyrolysis products, and the pyrolysis operating conditions.

9. The pyrolysis optimization method according to any one of claims 1 to 8, characterized in that, The cracking optimization method further includes: calculating the break-even purchase price of raffinate and determining the procurement strategy.

10. The pyrolysis optimization method according to any one of claims 1 to 9, characterized in that, The calculation of the break-even purchase price of the raffinate oil includes: Break-even purchase price of raffinate oil = (Product revenue from raffinate oil - Processing cost of raffinate oil) / Purchase quantity of raffinate oil; Preferably, the break-even purchase price of the raffinate is checked based on the different revenues of the raffinate under different cracking operation conditions, and the procurement strategy is optimized.

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