A method for calculating the final yield of an ethylene plant product

Abstract

The application discloses an ethylene device product final yield calculation method, and belongs to the technical field of ethylene production. The method comprises the following steps: step 1, determining the single-pass yield of the ethylene device; step 2, obtaining the cycle number of each cyclic cracking raw material; step 3, calculating the hydrogen consumption of the cyclic cracking raw material in the hydrogenation reaction in the cyclic cracking process; step 4, calculating the type and weight of the target product generated after the cyclic cracking raw material in the hydrogenation reaction in the cyclic cracking process; and step 5, calculating the final total yield of each target product. In the ethylene device product final yield calculation method, the cyclic cracking of multiple cyclic cracking raw materials in the ethylene device processing process is considered to generate target products multiple times, and part of the cyclic cracking raw materials will generate hydrogenation reactions in the cyclic cracking process, thereby causing the consumption of hydrogen in the target product. Compared with traditional mechanism models, the accuracy of the final yield calculation of the target product is improved.

Description

Technical Field

[0001] A method for calculating the final yield of ethylene plant products, belonging to the field of ethylene production technology. Background Technology

[0002] Ethylene plants are the leading petrochemical production facilities. Their production processes are relatively complex, involving both physical and chemical reactions, and encompassing both high-temperature (1300℃) and low-temperature (-170℃) processes. The main processes include several typical chemical unit processes such as cracking, quenching, compression, and separation.

[0003] The final target products of an ethylene plant include several types, such as ethylene, propylene, and hydrogen. The final yield of these target products is directly related to the product quality and output of the ethylene production plant. Furthermore, the total final yield of the target products is an important criterion for evaluating the ultimate profitability of the ethylene plant. Many factors influence the yield of an ethylene plant. For example, the complex sources of raw materials for ethylene plants, and the different supply models of suppliers, result in significant price differences and compositional variations among the various raw materials, which greatly affect the product distribution of the plant.

[0004] However, among the various factors affecting the final yield of an ethylene plant, the most easily overlooked is that during the reaction of the feedstock within the ethylene plant, several intermediate products are generated. These intermediate products are not output as the target product but are mixed with the feedstock and returned to the ethylene plant for further reaction to form the target product. Furthermore, the conversion rate of each intermediate product is different, therefore the number of cycles required before each intermediate product is completely consumed also varies, thus affecting the calculation of the final yield of the target product.

[0005] Existing mechanistic models, such as Pertosim developed by KBC, Spyro software from Des Nippon, and Coilsim software from East China University of Science and Technology, all rely on these models for calculations. The results are output as the single-pass cracking yield of a single feedstock, i.e., the single-pass yield. The contribution of a change in feedstock input to the overall plant output can only be determined by observing changes in the plant's overall input and output. Because plant operation is affected not only by feedstock structure and quality but also by process operation, operational stability, and equipment operating cycles, data comparisons can only provide a rough assessment of feedstock quality, resulting in poor accuracy. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a method for calculating the final yield of ethylene plant products that takes into account the need for repeated cyclic cracking of various circulating cracking feedstocks to produce the target product during the ethylene plant processing, and the fact that some circulating cracking feedstocks undergo hydrogenation reactions during the cyclic cracking process, thereby consuming hydrogen in the target product. Compared with various traditional mechanism models, this method improves the accuracy of the final yield calculation of the target product.

[0007] The technical solution adopted by this invention to solve its technical problem is: a method for calculating the final yield of ethylene plant products, characterized by including the following steps: The method for calculating the final yield of ethylene plant products is characterized by the following steps: Step 1: Determine the single-pass yield of the ethylene unit; Step 2: Obtain the number of cycles for each type of pyrolysis feedstock; Step 3: Calculate the amount of hydrogen consumed by the hydrogenation reaction of the circulating cracking feedstock during the circulating cracking process; Step 4: Calculate the type and weight of the target product generated after the cyclic pyrolysis feedstock undergoes the cyclic pyrolysis process; Step 5: Calculate the final total yield for each target product.

[0008] Preferably, the circulating pyrolysis feedstock includes ethane, propane, acetylene, and methylacetylene.

[0009] Preferably, in step 4, based on the conversion rate of each cyclic pyrolysis feedstock participating in the pyrolysis process, the weight of each cyclic pyrolysis feedstock after each pyrolysis cycle, the weight and type of each target product generated after each pyrolysis cycle are calculated. After each cyclic pyrolysis feedstock is consumed, based on the number of times each cyclic pyrolysis feedstock participates in the pyrolysis cycle, the weight of the target product generated in each pyrolysis cycle in which each cyclic pyrolysis feedstock participates is obtained.

[0010] Preferably, in step 5, the formula for calculating the final hydrogen yield in the target product is: Hydrogen final yield = Single-pass hydrogen final yield + First cycle yield + Second cycle yield - 3 * (Single-pass acetylene yield / 2 * 2 / 26) - 3 * (Single-pass methylacetylene yield / 2 * 2 / 40) The first cycle yield represents the hydrogen yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the hydrogen yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0011] Preferably, in step 5, the formula for calculating the final ethylene yield in the target product is: Ethylene final yield = Single-pass ethylene yield + First cycle yield + Second cycle yield + Single-pass acetylene yield / 2 * 28 / 26 The first cycle yield represents the ethylene yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the ethylene yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0012] Preferably, in step 5, the formula for calculating the final yield of propylene in the target product is: Propylene final yield = One-pass propylene final yield + First cycle yield + Second cycle yield + One-pass methylacetylene yield / 2 * 42 / 40 The first cycle yield represents the propylene yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the propylene yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0013] Compared with the prior art, the beneficial effects of this invention are: In this method for calculating the final yield of ethylene plant products, the need for repeated cyclic cracking of various feedstocks during the ethylene plant processing to produce the target product is taken into account. At the same time, some of the cyclic cracking feedstocks undergo hydrogenation reactions during the cyclic cracking process, which consumes hydrogen in the target product. Compared with various traditional mechanism models, this method improves the accuracy of the final yield calculation of the target product.

[0014] In the calculation method of the final yield of the ethylene unit product, the nonlinear stepwise regression analysis method is used to perform several iterations of calculation on the circulating cracking feedstock, which can well reflect the final yield of the circulating cracking feedstock and more intuitively reflect the consistency of the ethylene unit from feedstock input to product output.

[0015] In the calculation method for the final product yield of this ethylene unit, the impact of alkyne conversion to alkanes on the output results was investigated. Multiple iterative calculations were performed until the ethane and propane outputs reached zero. The calculations were consistent with the actual material balance of the unit, ensuring the accuracy of the results.

[0016] This method for calculating the final yield of ethylene plant products overcomes the shortcomings of existing technologies by processing the calculation results based on the reaction principle of ethylene thermal cracking. A representative example is the commercial cracking furnace simulation and evaluation software for ethylene plants. By performing nonlinear data regression analysis on alkanes and correcting the kinetic parameters of alkynes, it supplements and improves the shortcomings of the mechanism model, which only calculates the single-pass yield. This deepens the data application of commercial cracking furnace evaluation software and makes the highly specialized calculation results more widely applicable to management fields such as operation, technology, planning, and finance. It is an innovation in the data optimization management of ethylene plants. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the method for calculating the final yield of ethylene plant products. Detailed Implementation

[0018] Figure 1 This is the preferred embodiment of the present invention, which is described below in conjunction with the accompanying drawings. Figure 1 The present invention will be further described below.

[0019] like Figure 1 As shown, a method for calculating the final yield of ethylene plant products includes the following steps: Step 1: Determine the single-pass yield of the ethylene unit; First, the single-pass yield of all products from the ethylene plant is determined using existing mechanistic models, including but not limited to: Pertosim developed by KBC, Spyro software from Technip, and Coilsim software from East China University of Science and Technology. Using the original weight of the feedstock and the single-pass yield of all products, the weight of each product after the single-pass conversion can be calculated.

[0020] Step 2: Obtain the number of cycles for each type of pyrolysis feedstock; During the ethylene production process, after the feedstock enters the unit and undergoes a complete cracking process, in addition to the target product, various recycled feedstocks are generated. These recycled feedstocks include ethane, propane, acetylene, and methylacetylene. Ethane, propane, acetylene, and methylacetylene are not discharged from the ethylene unit but are returned to the cracking furnace for further reaction. As these recycled feedstocks continuously return to the cracking furnace, they are consumed at a certain conversion rate until their weight drops to a negligible level (e.g., 1 kg), at which point they are considered completely consumed. The target products include hydrogen, methane, ethylene, propylene, isobutane, n-butane, butene, butadiene, C5 hydrocarbons, benzene, aromatic raffinate, diesel oil, and heavy oil.

[0021] In this step, the number of times each cyclic pyrolysis feedstock participates in cyclic pyrolysis when it is completely consumed is obtained based on the conversion rate of each cyclic pyrolysis feedstock.

[0022] Step 4: Calculate the amount of hydrogen consumed by the hydrogenation reaction of the circulating cracking feedstock during the circulating cracking process; Before each pyrolysis cycle reaction, each type of recycled feedstock needs to be extracted from the mixed product through a hydrogenation reaction. After extraction, it is returned to the ethylene unit for pyrolysis cycle. Since hydrogen itself is one of the template products of the ethylene unit, the hydrogenation reaction consumes the hydrogen produced by the ethylene unit itself. Therefore, the recycled feedstock will also affect the final yield of the target product (hydrogen) of the ethylene unit.

[0023] Based on the conversion rates of ethane, propane, acetylene, and methylacetylene in the cracking process in existing technologies, the amount of hydrogen consumed by ethane, propane, acetylene, and methylacetylene in each cracking process can be calculated. Based on the number of cracking cycles in which ethane, propane, acetylene, and methylacetylene participate, the total amount of hydrogen consumed by ethane, propane, acetylene, and methylacetylene in their respective cracking cycles can be obtained.

[0024] Step 4: Calculate the type and weight of the target product generated from the recycled pyrolysis feedstock that has undergone hydrogenation reaction during the recycled pyrolysis process; Based on the number of cracking cycles participated in by ethane, propane, acetylene, and methylacetylene, the weight of each target product generated in each cracking cycle, and the weight and type of each product produced in each cracking cycle, can be obtained. After ethane, propane, acetylene, and methylacetylene are consumed, the weight of the target product generated in each cracking cycle, based on the number of cracking cycles participated in by each of ethane, propane, acetylene, and methylacetylene, can be obtained.

[0025] Step 5: Calculate the final total yield for each target product; Based on the target product generated from the recycled cracking feedstock participating in the cracking cycle and the amount of hydrogen consumed, calculated in steps 1 to 5 above, the final total yield of the target product of the ethylene unit is obtained: Hydrogen final yield = single-pass hydrogen final yield + first cycle yield + second cycle yield - 3 * (single-pass acetylene yield / 2 * 2 / 26) - 3 * (single-pass methylacetylene yield / 2 * 2 / 40); The first cycle yield represents the hydrogen yield of ethane and propane after completing their respective cracking cycles. The second cycle yield represents the hydrogen yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0026] Ethylene final yield = Single-pass ethylene final yield + First cycle yield + Second cycle yield + Single-pass acetylene yield / 2 * 28 / 26; The first cycle yield represents the ethylene yield of ethane and propane after completing their respective cracking cycles. The second cycle yield represents the ethylene yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0027] Propylene final yield = single-pass propylene final yield + first cycle yield + second cycle yield + single-pass methylacetylene yield / 2 * 42 / 40; The first cycle yield represents the propylene yield of ethane and propane after completing their respective cracking cycles. The second cycle yield represents the propylene yield of acetylene and methylacetylene after completing their respective cracking cycles.

[0028] The yield of other target products is equal to the sum of the single-pass yield of the corresponding target product and the yield of each of the first cycles (the yield of the corresponding target product of ethane and propane after completing their respective cracking cycles) and the yield of the second cycle (the yield of the corresponding target product of acetylene and methylacetylene after completing their respective cracking cycles).

[0029] The following compares the single-pass yield and final yield of the target product when naphtha, cracked tail oil, light hydrocarbons, and ethane are used as feedstocks in an ethylene plant: Table 1. Statistics on the single-pass yield and final yield of various target products using naphtha as raw material. Table 2. Statistics on single-pass yield and final yield of various target products using cracked tail oil as feedstock. Table 3. Statistics on single-pass yield and final yield of various target products for light hydrocarbon feedstocks. Table 4. Statistics on single-pass yield and final yield of various target products using ethane as feedstock. Comparative example: Table 5 Comparison of Key Results of Annual Ethylene Unit Material Balance Yield and Final Yield Calculations As shown in Tables 1 to 4 above, among all target products, the final yields of ethylene, propylene, and butadiene are significantly higher than their single-pass yields, while the final yields of ethane and propane are 0%, meaning that ethane and propane do not appear in the final product yield of the cracking process. This is consistent with the actual situation. Furthermore, as shown in Table 5, the output material balance results are almost identical to the calculation model results of this invention, which can well reflect the reliability of the final product yield calculation method of this ethylene plant.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for calculating the final yield of products from an ethylene plant, characterized in that: Includes the following steps: Step 1: Determine the single-pass yield of the ethylene unit; Step 2: Obtain the number of cycles for each type of pyrolysis feedstock; Step 3: Calculate the amount of hydrogen consumed by the hydrogenation reaction of the circulating cracking feedstock during the circulating cracking process; Step 4: Calculate the type and weight of the target product generated after the cyclic pyrolysis feedstock undergoes the cyclic pyrolysis process; Step 5: Calculate the final total yield for each target product; In step 5, the formula for calculating the final hydrogen yield in the target product is as follows: Hydrogen final yield = Single-pass hydrogen final yield + First cycle yield + Second cycle yield - 3 * (Single-pass acetylene yield / 2 * 2 / 26) - 3 * (Single-pass methylacetylene yield / 2 * 2 / 40) Wherein, the first cycle yield represents the hydrogen yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the hydrogen yield of acetylene and methylacetylene after completing their respective cracking cycles. In step 5, the formula for calculating the final yield of ethylene in the target product is as follows: Ethylene final yield = Single-pass ethylene yield + First cycle yield + Second cycle yield + Single-pass acetylene yield / 2 * 28 / 26 Wherein, the first cycle yield represents the ethylene yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the ethylene yield of acetylene and methylacetylene after completing their respective cracking cycles. In step 5, the formula for calculating the final yield of propylene in the target product is as follows: Propylene final yield = One-pass propylene final yield + First cycle yield + Second cycle yield + One-pass methylacetylene yield / 2 * 42 / 40 The first cycle yield represents the propylene yield of ethane and propane after completing their respective cracking cycles; the second cycle yield represents the propylene yield of acetylene and methylacetylene after completing their respective cracking cycles.

2. The method for calculating the final yield of ethylene plant products according to claim 1, characterized in that: The circulating pyrolysis feedstock includes ethane, propane, acetylene, and methylacetylene.

3. The method for calculating the final yield of ethylene plant products according to claim 1, characterized in that: In step 4, based on the conversion rate of each cyclic pyrolysis feedstock acetylene and methylacetylene participating in the pyrolysis process, the weight of each cyclic pyrolysis feedstock after each pyrolysis cycle, the weight and type of each target product generated after each pyrolysis cycle are calculated. After each cyclic pyrolysis feedstock is consumed, based on the number of times each cyclic pyrolysis feedstock participates in the pyrolysis cycle, the weight of the target product generated in each pyrolysis cycle in which each cyclic pyrolysis feedstock participates is obtained.

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