An integrated crude oil scheduling and blending method with dynamic relaxation

Abstract

The present invention discloses a crude oil scheduling and blending integrated method with dynamic relaxation. This method introduces a relaxation strategy that can dynamically adjust the crude oil property constraints to help refining enterprises formulate crude oil scheduling and production scheduling plans that can be executed for a long time, aiming at the situation where the scheduling plan does not match the crude oil feed property constraints of the atmospheric and vacuum unit, resulting in the inability to continue scheduling and production scheduling. This method can guide the orderly implementation of crude oil scheduling operations, further improve the executability and flexibility of the crude oil blending and scheduling integrated system, and ensure the smooth transition and operation of crude oil scheduling and production and processing.

Description

Technical Field

[0001] The present invention relates to the field of crude oil scheduling and blending, and in particular to a crude oil scheduling and blending integration method which adopts a dynamic relaxation strategy to improve the executability and flexibility of crude oil scheduling. Background Art

[0002] The integration of crude oil blending and scheduling has become an effective method for refining enterprises to coordinate crude oil storage and transportation with processing production. By integrating crude oil blending and scheduling, it is possible to formulate production arrangements for a longer period of time (such as the next week) and achieve long-term continuous and stable production operation.

[0003] However, there are still some technical problems that need to be solved in the actual application of the integrated scheduling and blending scheme. Due to the increasing external dependence of my country's crude oil processing and the impact of oil price fluctuations in the international crude oil market, there are many types of imported crude oil for refining and chemical enterprises, and the amount of crude oil in different procurement batches is unbalanced. These problems have deepened the contradiction between crude oil scheduling and blending crude oil property control, resulting in scheduling difficulties, and even unable to obtain a complete cycle scheduling plan that meets the property requirements. In fact, when scheduling and scheduling, enterprise dispatchers often adopt the strategy of "loose in the distance and tight in the near" to address the above problems, that is, strictly control the current properties, and appropriately relax the properties a few days later. This is because there are always some uncertainties in the process of crude oil scheduling and processing. It is normal for enterprises to make adjustments in production. Strict feed property constraints have a positive effect on current production, but production constraints that are farther away can be appropriately relaxed so that scheduling and scheduling can continue.

[0004] In summary, refining and chemical companies are in urgent need of an improved integrated crude oil scheduling and blending system, which can adjust the constraints of production scheduling based on the experience of on-site process personnel and changes in the production process, thereby improving the feasibility and flexibility of crude oil scheduling and making the integrated crude oil scheduling and blending system closer to actual production needs. Summary of the invention

[0005] The purpose of the present invention is to provide an integrated crude oil scheduling and blending method with dynamic relaxation. When the crude oil scheduling and production plan conflicts with the feed demand of a constant pressure reduction unit (CDU), the method introduces a temporary scheduling plan using a dynamic relaxation strategy to replace the current plan. At the same time, combined with the experience of on-site process personnel, the optimal crude oil scheduling and production plan that can be executed for a long time is re-solved and the temporary plan is replaced to ensure that the scheduling and production process can operate sustainably and smoothly.

[0006] The present invention has the following steps:

[0007] (1) Determine the type and quantity of crude oil to be processed within a scheduling cycle based on the company's crude oil processing production needs and inventory, and determine the feed property constraints of the atmospheric and vacuum processing unit;

[0008] (2) Using a crude oil blending optimization model that takes inventory into consideration, the crude oil blending formula is optimized;

[0009] (3) Add existing blending formula constraints to the scheduling plan and formulate a crude oil scheduling plan;

[0010] (4) determining whether the scheduling plan matches the feed constraint of the atmospheric and vacuum device; if the scheduling plan meets the constraint, then continuing to execute the scheduling plan; otherwise, proceeding to step (5);

[0011] (5) Includes two operations performed simultaneously:

[0012] (5A) Abandon the original scheduling plan, switch the scheduling condition from normal state to emergency state, and introduce the dynamic relaxation strategy of blended crude oil property constraints according to the following formula to obtain the emergency crude oil scheduling plan:

[0013]

[0014] Where t is the scheduling optimization time step, represents the θth crude oil property in the scheduling optimization period corresponding to t, U θmax , U θmin Respectively The upper and lower limits of the allowable opt1 The setting value of the optimization time step is 1, that is, the properties must be within the allowable range within this time period, t opt2 To set the optimization time step to 2, is the dynamic relaxation factor of the θth crude oil property in the scheduling optimization period corresponding to t;

[0015] (5B) Reset the target feed properties, combine the inventory, and calculate the optimal crude oil scheduling plan that can be executed for a long time; (6) After obtaining the optimal crude oil scheduling plan in step (5B), terminate the emergency crude oil scheduling plan and continue to execute the optimal crude oil scheduling plan.

[0016] Preferably, the dynamic relaxation factor introduced in the scheduling constraint process in step (5A) is Calculated according to the following formula:

[0017]

[0018] In the formula Indicates that the result of the internal expression calculation is rounded up, ν θ is the weight of the dynamic relaxation factor in the θth crude oil property constraint.

[0019] Preferably, the specific steps for obtaining the optimal crude oil scheduling plan in step (5B) are as follows:

[0020] (5B-1) Process personnel reset the target properties of the blended crude oil fed to the atmospheric and vacuum unit based on the actual oil storage conditions.

[0021] and input the target properties into the crude oil blending optimization unit;

[0022] (5B-2) using a crude oil blending optimization method that takes into account the scheduling inventory to optimize according to the re-given target properties, and solving for a crude oil blending formula that can be used for long-term continuous production scheduling of crude oil scheduling;

[0023] (5B-3) The crude oil blending formula generated in step (5B-2) is input into the crude oil scheduling unit, and the optimal crude oil scheduling and production plan that can be executed for a long time is obtained through optimization.

[0024] Preferably, t opt1 Take 3 days, that is, 72 hours, t opt2 Take 7 days, that is, 168 hours.

[0025] Beneficial effects:

[0026] The present invention discloses a crude oil scheduling and blending integrated method with dynamic relaxation. The method introduces a relaxation strategy that can dynamically relax the crude oil property constraints to help refining enterprises formulate crude oil scheduling and production scheduling plans that can be executed for a long time, aiming at the situation where the scheduling plan does not match the crude oil feed property constraints of the atmospheric and vacuum unit, resulting in the inability to continue scheduling and production scheduling. The method can guide the orderly implementation of crude oil scheduling operations, further improve the executability and flexibility of the crude oil blending and scheduling integrated system, and ensure the smooth transition and operation of crude oil scheduling and production and processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of a crude oil scheduling and blending integrated method with dynamic relaxation of the present invention;

[0028] Figure 2 It is the crude oil dispatching plan obtained by introducing dynamic relaxation into the tank farm within the plant;

[0029] Figure 3 It is the crude oil scheduling solution obtained by introducing dynamic relaxation into CDU;

[0030] Figure 4 It is the crude oil dispatching plan after re-optimization of the tank farm within the plant;

[0031] Figure 5 It is the crude oil scheduling plan after CDU re-optimization.

[0032] Specific implementation process

[0033] The following is a combination of the accompanying drawings and specific examples to illustrate the implementation effect of the method in the integration of crude oil scheduling and blending through a specific operation process. This implementation case is implemented based on the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0034] This paper studies and analyzes a real case of insufficient crude oil reserves in a certain refinery to demonstrate the feasibility and flexibility of this method in practical application. The enterprise has two CDUs (CDU1 and CDU2), and this case is explained using CDU2 as an example. The enterprise requires that the crude oil blending and scheduling integrated system can provide scheduling results for the next 7 days (168 hours), that is, t opt2 =168.

[0035] (1) The inventories in this case are the inventory in the terminal tank area and the storage in the plant tank area. The inventory in the terminal tank area is shown in Table 1:

[0036] Table 1 Beginning inventory of tanks in the terminal tank area

[0037]

[0038] The initial inventory of the tank area in the factory is shown in Table 2:

[0039] Table 2 Initial inventory of tanks in the factory tank area

[0040]

[0041]

[0042] For the sake of verification, this case only considers three key properties of crude oil: relative density, sulfur content and acid value. The CDU2 feed property requirements are shown in Table 3:

[0043] Table 3 Target property range of CDU2 feed blending crude oil

[0044]

[0045] The weights in the crude oil property constraints in the dynamic relaxation scheme are set to ν θ =[0,0.3,0.1], the property constraint weight is determined by on-site process personnel.

[0046] (2) In this case, the preset crude oil blending formula for CDU2 at the beginning, i.e., hour 0, is Kuwait: Basra Heavy: Castile = 0.2:0.2:0.6. Since the processing flow rate of CDU2 is 1000 t / h, the instantaneous processing volume of Kuwait, Basra Heavy, and Castile is 200 t / h, 200 t / h, and 600 t / h, respectively. Combining Tables 1 and 2, it can be concluded that the total amount of the terminal tank area and the plant tank area during the entire crude oil scheduling cycle is only 16,000 m 3 That is, 14,560 tons of Basra weight is only enough for CDU2 to process continuously for 72 hours.

[0047] (3) Combination Figure 1 , Phase 1: The integrated system uses the scheduling optimization method of crude oil transportation process considering online blending. The inventory of the tanks in the plant in the first 71 hours is sufficient for crude oil scheduling to be scheduled according to the preset crude oil blending formula. At this time, the integrated system is in a normal state, that is, the scheduling optimization has not failed and continues to operate. When the timeline reaches 71 hours, due to the exhaustion of Basra heavy oil reserves, the original integrated system can no longer provide a scheduling plan, resulting in the crude oil scheduling plan it provides being unable to reach 168 hours. At this time, the integrated system will enter an emergency state.

[0048] (4) Phase II (relaxed plan for temporary emergency execution): The crude oil scheduling optimization method considering dynamic relaxation is used to generate a crude oil scheduling plan that is accurate for the first three days and fuzzy for the next four days as a temporary alternative. To this end, set t opt1 = 70h, the alternative crude oil scheduling scheme is given as Figure 2 and Figure 3 As shown, Figure 2 Changes in the receipt and payment of oil in the factory storage tanks, Figure 3 The situation of CDU processing different crude oils. It can be seen that detailed scheduling operations have been given after the 71st hour, which confirms that when the crude oil stored in all tank areas is not enough to schedule production for a long time according to the preset crude oil blending formula, the crude oil scheduling optimization method considering dynamic relaxation can adaptively adjust the CDU2 feed properties to obtain an accurate crude oil scheduling plan for 70 hours, avoiding the situation where no complete scheduling plan is available. In the 71st hour, due to the intervention of dynamic relaxation, a crude oil blending formula with looser properties began to be used for CDU2 processing. Comparing the 72nd to 96th hours with the 96th to 168th hours, it can be seen that after the intervention of dynamic relaxation, due to the dynamic relaxation factor As time passes, dynamic relaxation gradually relaxes the property requirements, the crude oil blending formula changes, and the scheduling plan also changes accordingly, thus ensuring the continuity and integrity of the generated scheduling plan.

[0049] (5) Phase 2 (long-term scheduling and production plan planning): While implementing the temporary plan, the on-site process personnel reset the CDU2 target feed properties, as shown in Table 4:

[0050] Table 4 Target values ​​of CDU2 feed blending crude oil before and after adjustment

[0051]

[0052] The crude oil scheduling inventory when production cannot be continued in the 71st hour is shown in Table 5:

[0053] Table 5 Cumulative dispatch inventory of each oil type in the tank area of ​​the factory (t = 71h)

[0054]

[0055] (6) The integrated system uses the crude oil blending optimization method considering the scheduling inventory. According to the target value set by the process personnel, the preset property constraints and the scheduling inventory of the tank storage tank in the plant, the crude oil blending optimization is performed on the case, and a new crude oil blending formula is given as [Kuwait crude oil: Fordyce crude oil: Castile crude oil = 0.4679: 0.0290: 0.5031], corresponding to the respective instantaneous crude oil processing capacities of 467.9 t / h, 29.0 t / h and 503.1 t / h. Its properties are shown in Table 6:

[0056] Table 6 Key properties of crude oil blending formula after re-optimization

[0057]

[0058] (7) The integrated system inputs this blending formula into the crude oil transportation process scheduling optimization method considering online blending, and then re-optimizes and solves it to obtain the optimal crude oil scheduling plan that can be scheduled for a long time, as shown in the following figure. Figure 4 and Figure 5 All scheduling operations included in the re-optimized crude oil scheduling plan meet the process requirements and can complete the long-term crude oil scheduling work of 7 days (168 hours).

[0059] Compared with the crude oil scheduling scheme given by the crude oil scheduling optimization method considering dynamic relaxation, the crude oil blending formula in the re-optimized crude oil scheduling scheme has fewer switching times, and it was only switched at the 71st hour during the whole process. The blending formula will not be switched later, and the CDU2 feed properties are more stable. Since the crude oil blending formula is used, which has been confirmed by the on-site process personnel with the new optimization target and re-optimized by the blending optimization method, the generated crude oil scheduling scheme can well guide the orderly implementation of crude oil scheduling operations and ensure the smooth operation of crude oil production and processing technology.

Claims

1. A crude oil scheduling and blending integrated method with dynamic relaxation, characterized in that The dynamic relaxation strategy of the blended crude oil property constraints that change over time is introduced into crude oil scheduling to improve the feasibility and flexibility of crude oil scheduling. The following steps are involved: (1) Determine the type and quantity of crude oil to be processed within a scheduling cycle based on the company's crude oil processing production needs and inventory, and determine the feed property constraints of the atmospheric and vacuum processing unit; (2) Using a crude oil blending optimization model that takes inventory into consideration, the crude oil blending formula is optimized; (3) Add existing blending formula constraints to the scheduling plan and formulate a crude oil scheduling plan; (4) determining whether the scheduling plan matches the feed constraint of the atmospheric and vacuum device; if the scheduling plan meets the constraint, then continuing to execute the scheduling plan; otherwise, proceeding to step (5); (5) Includes two operations performed simultaneously: (5A) Abandon the original scheduling plan, switch the scheduling condition from normal state to emergency state, and introduce the dynamic relaxation strategy of blended crude oil property constraints according to the following formula to obtain the emergency crude oil scheduling plan: Where t is the scheduling optimization time step, represents the θth crude oil property in the scheduling optimization period corresponding to t, U θmax , U θmin Respectively The upper and lower limits of the allowable opt1 The setting value of the optimization time step is 1, that is, the properties must be within the allowable range within this time period, t opt2 To set the optimization time step to 2, is the dynamic relaxation factor of the θth crude oil property in the scheduling optimization period corresponding to t; (5B) Reset the target feed properties, combine the inventory, and calculate the optimal crude oil scheduling plan that can be executed for a long time; (6) After obtaining the optimal crude oil scheduling and production scheduling plan in step (5B), the emergency crude oil scheduling and production scheduling plan is terminated and the optimal crude oil scheduling and production scheduling plan is continuously executed.

2. The integrated crude oil scheduling and blending method with dynamic relaxation according to claim 1, characterized in that The dynamic relaxation factor introduced in the scheduling constraint process in step (5A) Calculated according to the following formula: In the formula Indicates that the result of the internal expression calculation is rounded up, ν θ is the weight of the dynamic relaxation factor in the θth crude oil property constraint.

3. The integrated crude oil scheduling and blending method with dynamic relaxation according to claim 1, characterized in that The specific steps for obtaining the optimal crude oil scheduling plan in step (5B) are as follows: (5B-1) Process personnel reset the target properties of the blended crude oil fed into the atmospheric and vacuum unit according to the actual oil storage conditions, and input the target properties into the crude oil blending optimization unit; (5B-2) using a crude oil blending optimization method that takes into account the scheduling inventory to optimize according to the re-given target properties, and solving for a crude oil blending formula that can be used for long-term continuous production scheduling of crude oil scheduling; (5B-3) The crude oil blending formula generated in step (5B-2) is input into the crude oil scheduling unit, and the optimal crude oil scheduling and production plan that can be executed for a long time is obtained through optimization.

4. The integrated crude oil scheduling and blending method with dynamic relaxation according to claim 1, characterized in that t opt1 Take 3 days, that is, 72 hours, t opt2 Take 7 days, that is, 168 hours.

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