Linear Programming-based Approach to Scheduling of Crude Oil Operations in Refinery for Energy Efficiency Optimization

Abstract

For sustainable development, a refinery is required to save energy as much as possible so as to reduce the emission of greenhouse gas. In crude oil operations, oil transportation from storage tanks to charging tanks via a pipeline consumes a large portion of energy. It is vitally important to minimize energy consumption for this process. Since the oil flow resistance is proportional to the square of oil flow rate, the relation between energy efficiency and flow rate is nonlinear, which makes the problem complicated. The present invention addresses this important issue by formulating a linear programming model for the considered problem such that it can be efficiently solved. A real-world industrial case study is used to demonstrate the applications and significance of the proposed method.

Claims

1. A computer-implemented method for scheduling a crude oil operation process in a refinery, the oil operation process comprising one or more tasks DTSs for oil delivering from one or more storage tanks to one or more charging tanks, the refinery comprising a pipeline system used to transport crude oil from the storage tanks to the charging tanks, the pipeline system comprising a pipeline and a number of pumping stations, and a number of sets of machines in each of the pumping stations, the method comprising: determining, by a processor, the number of sets of machines n usable at each of the pumping stations, by minimizing energy consumption J for the process based on a linear programming model as follow: $Minimize .Math. .Math. J = \underset{i G}{.Math.} .Math. .Math. \underset{j N_{ki}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. C_{h} .Math. x_{ijh};$ $Subject .Math. .Math. to .Math. :$ $_{11} A_{11};$ $\underset{h S}{.Math.} .Math. .Math. x_{1 .Math. .Math. jh} = V_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1};$ $_{11} + {.Math.}_{g = 1}^{j} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{1 .Math. gh} / f_{h} + T_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1};$ $_{i .Math. .Math. 1} A_{i .Math. .Math. 1}, i G .Math. \ .Math. {1};$ $_{i .Math. .Math. 1}_{(i - 1) .Math. 1} + \underset{j N_{k (i - 1)}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{(i - 1) .Math. jh} / f_{h}, i G .Math. \ .Math. {1};$ $\underset{h S}{.Math.} .Math. .Math. x_{ijh} = V_{ij}, i G .Math. \ .Math. {1}, j N_{ki};$ $_{i .Math. .Math. 1} + \overset{j}{\underset{g = 1}{.Math.}} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{igh} / f_{h} + T_{ij}, j N_{ki}, i G .Math. \ .Math. {1};$ $x_{ijh} 0 .Math. .Math. and .Math. .Math._{i .Math. .Math. 1} 0;$ wherein: n is the number of sets of machines usable at each pumping station; S={1, 2, . . . , n} is a set of the number of sets of machines; d is a number of groups of DTSs; G={1, 2, . . . , d}; N.sub.ki={1, 2, . . . , ki}; DTS.sub.ij is a j-th DTS in Group iG and jN.sub.ki that is decided by a predetermined schedule; G.sub.i={DTS.sub.i1, DTS.sub.i2, . . . , DTS.sub.i(ki)}; V.sub.ij is an amount of oil to be transported in DTS.sub.ij; TK.sub.ij is a charging tank to be charged by performing DTS.sub.ij that is decided in the given schedule; A.sub.ij is a time point when TK.sub.ij starts to be charged by performing DTS.sub.ij as given by the schedule; B.sub.ij is a time point when the charging of TK.sub.ij ends as given by the schedule; T.sub.ij is a time point when TK.sub.ij charged by performing DTS.sub.ij begins to feed a distiller as given by the schedule; is an oil residency time; f.sub.i is a most energy-effective oil transportation flow rate when i sets of machines are used at each pumping station; C.sub.i is a cost coefficient when i sets of machines are used at each pumping station; x.sub.ijh is an amount of oil in DTS.sub.ij to be transported by using the most energy-efficient flow rate with h sets of machines being used at each pumping station, iG, jN.sub.ki, and hS; and .sub.i1 is a time point when TK.sub.i1 starts to be charged by performing DTS.sub.i1 after oil transportation rate is regulated.

2. The method of claim 1, wherein the C.sub.n is given by n/f.sub.n.

3. The method of claim 1, wherein the energy consumption is minimized by regulating oil transportation rate.

4. A non-transitory computer-readable medium whose contents cause a computing system to perform a computer-implemented method for scheduling a crude oil operation process in a refinery, the oil operation process comprising one or more tasks DTSs for oil delivering from one or more storage tanks to one or more charging tanks, the refinery comprising a pipeline system used to transport crude oil from the storage tanks to the charging tanks, the pipeline system comprising a pipeline and a number of pumping stations, and a number of sets of machines in each of the pumping stations, the method comprising: determining, by a processor, the number of sets of machines n usable at each of the pumping stations, by minimizing energy consumption J for the process based on a linear programming model as follow: $Minimize .Math. .Math. J = \underset{i G}{.Math.} .Math. .Math. \underset{j N_{ki}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. C_{h} .Math. x_{ijh};$ $Subject .Math. .Math. to .Math. :$ $_{11} A_{11};$ $\underset{h S}{.Math.} .Math. .Math. x_{1 .Math. .Math. jh} = V_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1};$ $_{11} + {.Math.}_{g = 1}^{j} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{1 .Math. gh} / f_{h} + T_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1};$ $_{i .Math. .Math. 1} A_{i .Math. .Math. 1}, i G .Math. \ .Math. {1};$ $_{i .Math. .Math. 1}_{(i - 1) .Math. 1} + \underset{j N_{k (i - 1)}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{(i - 1) .Math. jh} / f_{h}, i G .Math. \ .Math. {1};$ $\underset{h S}{.Math.} .Math. .Math. x_{ijh} = V_{ij}, i G .Math. \ .Math. {1}, j N_{ki};$ $_{i .Math. .Math. 1} + \overset{j}{\underset{g = 1}{.Math.}} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{igh} / f_{h} + T_{ij}, j N_{ki}, i G .Math. \ .Math. {1};$ $x_{ijh} 0 .Math. .Math. and .Math. .Math._{i .Math. .Math. 1} 0;$ wherein: n is the number of sets of machines usable at each pumping station; S={1, 2, . . . , n} is a set of the number of sets of machines; d is a number of groups of DTSs; G={1, 2, . . . , d}; N.sub.ki={1, 2, . . . , ki}; DTS.sub.ij is a j-th DTS in Group iG and jN.sub.ki that is decided by a predetermined schedule; G.sub.i={DTS.sub.i1, DTS.sub.i2, DTS.sub.i(ki)}; V.sub.ij is an amount of oil to be transported in DTS.sub.ij; TK.sub.ij is a charging tank to be charged by performing DTS.sub.ij that is decided in the given schedule; A.sub.ij is a time point when TK.sub.ij starts to be charged by performing DTS.sub.ij as given by the schedule; B.sub.ij is a time point when the charging of TK.sub.ij ends as given by the schedule; T.sub.ij is a time point when TK.sub.ij charged by performing DTS.sub.ij begins to feed a distiller as given by the schedule; is an oil residency time; f.sub.i is a most energy-effective oil transportation flow rate when i sets of machines are used at each pumping station; C.sub.i is a cost coefficient when i sets of machines are used at each pumping station; x.sub.ijh is an amount of oil in DTS.sub.ij to be transported by using the most energy-efficient flow rate with h sets of machines being used at each pumping station, iG, jN.sub.ki, and hS; and .sub.i1 is a time point when TK.sub.i1 starts to be charged by performing DTS.sub.i1 after oil transportation rate is regulated.

5. The non-transitory computer-readable medium of claim 4, wherein the C.sub.n is given by n/f.sub.n.

6. The non-transitory computer-readable medium of claim 4, wherein the energy consumption is minimized by regulating oil transportation rate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Embodiments of the present invention are described in more detail hereinafter with reference to the drawings, in which:

[0068] FIG. 1 depicts the illustrative view of a general oil refinery;

[0069] FIG. 2 depicts the Gantt chart for distiller feeding schedule;

[0070] FIG. 3 depicts the Gantt chart for oil transportation schedule via a pipeline;

[0071] FIG. 4 depicts illustration of a pipeline system;

[0072] FIG. 5 depicts optimization of energy consumption by regulating the flow rate of DTSs;

[0073] FIG. 6 depicts the distiller feeding schedule for the case problem;

[0074] FIG. 7 depicts the oil transportation schedule for the case problem; and

[0075] FIG. 8 depicts the Gantt chart for the optimized oil transportation schedule.

DETAILED DESCRIPTION

[0076] In the following description, a method for scheduling crude oil operations in refinery for energy efficiency optimization is set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.

[0077] It is commonly recognized that, to be competitive in a global market, an oil refinery should be well operated. Since the scheduling problem of a refinery is extremely complicated and challenging, much attention has been paid to this issue. In this research field, the main focus is on finding an efficient approach such that a scheduling problem is computationally solvable. In the existing methods, the objectives include maximizing productivity, minimizing oil inventory, minimizing changeover, and so on. However, no much work is found to take energy efficiency as an objective in scheduling an oil refinery. Due to the great effect of greenhouse on the global climate, an enterprise is required to be sustainable, i.e., energy efficiency is vitally important. The present invention addresses this issue in scheduling a refinery.

[0078] In a previous work, one presents a control-theoretic-based approach to the scheduling problem of crude oil operations, by which a schedule can be efficiently found. Based on the approach, the present invention studies the energy efficiency problem in crude oil operations. A linear programming-based method is proposed such that the problem can be efficiently solved. A real-world industrial study shows that, by the proposed method, significant energy can be saved.

[0079] Section A briefly introduces the process of crude oil operations and its short-term scheduling problem. Section B states the energy optimization problem in crude oil operations and presents the linear programming formulation for it. A real-world industrial case study is given to demonstrate the application and significance of the proposed method in Section C.

A. The Process and its Short-Term Schedule

[0080] Before presenting the problem discussed in the present invention and the method for it, one briefly introduces the processes of a refinery. An illustrative view of general/typical oil refinery processes can be depicted in FIG. 1. A refinery contains a number of storage tanks located at a port near the plant, a pipeline, a number of charging tanks in the plant, a number of distillers for oil distillation, and a variety of other production units. In the viewpoint of operations, there are two phases: 1) crude oil operations and 2) production. Crude oil arrives at the port through oil tankers by sea. It is then unloaded into storage tanks From the storage tanks, oil is delivered to charging tanks through the pipeline. Charging tanks are used to feed oil to the distillers for distillation. This process forms the first phase, called crude oil operations. The products obtained from distillation are further processed by other production units to obtain various components. These components are blended to form the final products, which is the production phase. A short-term scheduling problem for the process of crude oil operations is well recognized as being the most difficult in a refinery. That answers why one finds no implementable theory and software tools to enable industrial-size applications.

[0081] To meet the market demands, a refinery should process a number of crude oil types with different components. Each distiller can process some crude oil types, but not all, which in turn requires a tank (storage or charging tank) to hold one oil type at any time. Before oil can be processed by a distiller, brine must be separated from oil. To do so, it requires that, after filling a storage or charging tank, crude oil must stay in it for some time before it can be discharged. This is called an oil residency time constraint. Besides, any tank cannot be charged and discharged simultaneously. There is another requirement that a distiller must work continuously and cannot be stopped unless there is a planned maintenance. The above requirements pose a large number of constraints on the process of crude oil operations.

[0082] To schedule the process of crude oil operations is to decide the tasks to be performed and sequence them. A task is a discrete event for the process. In the execution of a task, oil is delivered in a continuous way, resulting in a hybrid system with both discrete-event and continuous processes. When a task is executed, the system is transformed from a state to another such that a task can be seen as a control command. Thus, the scheduling problem of crude oil operations is to determine the commands (tasks) and can be studied from a perspective of hybrid system control, as done in [Wu et al., 2008a, 2009, 2010a and b, 2011, 2012, and 2015a and b]. By the control-theoretic-based approach, a task is defined as follows.

[0083] Definition 2.1:

[0084] A task (TS) is defined as TS={OT, SP, DP, V, , }, where OT denotes an oil type; SP the source from which the oil comes, DP the device to which the oil is delivered; V the amount of oil to be processed; and and the start and end time points for a task.

[0085] For easy implementation and simplicity for finding a schedule, the oil delivering rate in a task is set to be a constant, i.e., f=V/(). In crude oil operations, there are three types of TSs: UTSs for oil unloading from a tanker to storage tanks, DTSs for oil delivering from storage tanks to charging tanks, and FTSs for oil feeding to distillers. With the definition of TSs, a short-term schedule SCHD for crude oil operations can be described as

SCHD={UTS.sub.1,UTS.sub.2, . . . ,UTS.sub.w,DTS.sub.1,DTS.sub.2, . . . ,DTS.sub.x,FTS.sub.1,FTS.sub.2, . . . ,FTS.sub.k}(2.1)

[0086] Thus, the scheduling problem of crude oil operations is to find an SCHD such that all the aforementioned requirements and constraints are met, while some objectives are optimized. By maximizing the oil flow rate of a pipeline, such a schedule can be efficiently found by the control-theoretic-based approach to optimize productivity and oil type processing effectiveness [Wu et al., 2008a, 2009, and 2012]. A schedule for a scenario from a refinery obtained by using this approach is shown in FIGS. 2 and 3, where DS.sub.i represents Distiller i. In FIG. 2, distiller feeding schedule is given by presenting the case when a charging tank is used to feed a type of oil into a distiller. For example, during time interval [0, T.sub.1], Charging Tank #1 is used to feed Oil Type #1 into Distiller 1. While, in FIG. 3, an oil transportation schedule from storage tanks to charging tanks is given by presenting the case when a type of oil is charged into a charging tank. For instance, during time [0, A.sub.1], Oil Type #1 is charged into Charging Tank #2.

[0087] By observing the schedule shown in FIG. 3, during time [A.sub.2, A.sub.3], the pipeline is stopped and no oil is transported. Note that, in transporting oil via the pipeline, the oil flow resistance is proportional to the square of the oil velocity. This implies that the higher the oil flow rate in the pipeline is, the more energy is consumed. Thus, when there is idle time for the pipeline, one may reduce the oil flow rate to save energy if the obtained schedule is still feasible. Also, the transportation of some oil parcels can be delayed by reducing the oil flow rate without affecting the distiller feeding schedule. In this way, energy consumption can be further reduced. The problem is coped with in the next section.

B. Problem Formulation and Solution Method

[0088] As aforementioned, to find a schedule for crude oil operations is to decide a series of TSs and, by the control-theoretic-based approach, the oil delivering rate for each TS is set to be a constant. Since the scheduling problem of crude oil operations is extremely complicated, it is difficult to efficiently find such a schedule by optimizing productivity and energy consumption simultaneously. However, with the maximal oil transportation rate via a pipeline, a schedule to maximize the productivity can be efficiently found. Based on such a schedule, this section discusses how to optimize energy consumption by regulating the oil transportation rate in the obtained DTSs.

B.1 Problem Statement

[0089] Given a schedule with maximal oil transportation rate for DTSs, to minimize energy consumption, one examines whether some parcels of oil in the DTSs can be delayed without impact on the feasibility of the schedule. If so, one can delay the transportation of some parcels by reducing the transportation rate.

[0090] A pipeline system in a refinery used to transport crude oil from storage tanks to charging tanks can be illustrated by FIG. 4. It is composed of a pipeline and a number of pumping stations that provide the power for the oil transportation. There are a number of sets of machines in each pumping station. The power provided by the system is dependent on the number of sets of machines that are in operation at each station. When the oil transportation rate needs to be increased, one puts more sets of machines in operation. However, the oil transportation rate is not proportional to the number of sets of working machines and is nonlinear. Take an example from a refinery. When one set of machines is used at each pumping station, the transportation rate of the pipeline is 20,000 tons per day. When two sets of machines are used, the rate is 30,000 tons per day. If three sets are used, it is only 33,000 tons per day. With such a nonlinear relationship between the transportation rate and power, it is very complicated to optimize energy consumption for oil transportation.

[0091] It is known that given the number of sets of machines to be used, there is a most energy-efficient oil transportation rate. In other words, to minimize energy consumption, given the number of sets of machines, its corresponding most energy-efficient flow rate should be applied. Hence, there are only several selections on oil transportation rate for the amount oil for each DTS. To do so, given a DTS={OT, SP, DP, V, , }, one divides V into n parcels V.sub.1, V.sub.2, . . . , and V.sub.n such that each parcel is delivered with different rate as shown in FIG. 5. Nevertheless, the feasibility needs to be guaranteed, i.e., when a charging tank is scheduled to be charged, it must be emptied, and when the oil in a charging tank is scheduled to be fed into a distiller, the oil residency constraint must be satisfied. Specifically, for the schedule given in FIGS. 2 and 3, by regulating the oil transportation rate of DTSs, Charging Tank #5 can be charged only after time point T.sub.4 and its charging should be ended Q time units earlier than time point T.sub.8 with Q being the oil residency time.

[0092] In summary, to minimize energy consumption for oil transportation via a pipeline, for each DTS={OT, SP, DP, V, , }, one needs to optimally divide V into n parcels V.sub.1, V.sub.2, . . . , and V.sub.n such that they are transported with flow rate level 1, 2, . . . , and n, respectively. A linear programming-based method can be developed to achieve this purpose.

B.2 a Linear Programming-Based Method

[0093] Given a short-term schedule for crude oil operations obtained by the control-theoretic-based approach, assume that there are k DTSs, each of which is used to charge a charging tank. These DTSs are sequenced such that DTS i+1 should be performed just after DTS i. Then, these DTSs are divided into d groups such that, in group G.sub.i, there are ki DTSs with k1+k2+ . . . +kd=k. One uses DTS.sub.ij to denote the j-th DTS in group G.sub.i, and A.sub.ij and B.sub.ij to denote time points when DTS.sub.ij starts to charge a charging tank and ends the charging, respectively. Note that A.sub.ij and B.sub.ij are given by the schedule obtained by the control-theoretic-based approach, i.e., they are known. Then, for the grouping, one has B.sub.ij=A.sub.i(j+1), i.e., in the same group, the DTSs are performed one after another without interruption. However, B.sub.i(ki)<A.sub.(i+1)1 must hold. In other words, between groups G.sub.i and G.sub.(i+1), the pipeline is schedule to be idle for some time. Based on this grouping of DTSs, one presents the following notations to formulate the considered problem.

[0094] Parameters and sets [0095] n: the number of sets of machines usable at each pumping station; [0096] S={1, 2, . . . , n}: the set of the number of sets of machines; [0097] d: the number of groups of DTSs; [0098] G={1, 2, . . . , d}; [0099] N.sub.ki={1, 2, . . . , ki}; [0100] DTS.sub.ij: the j-th DTS in Group iG and jN.sub.ki that is decided by a given schedule; [0101] G.sub.i={DTS.sub.i1, DTS.sub.i2, . . . , DTS.sub.i(ki)}; [0102] V.sub.ij: the amount of oil to be transported in DTS.sub.ij; [0103] TK.sub.ij: the charging tank to be charged by performing DTS.sub.ij that is decided in the given schedule; [0104] A.sub.ij: the time point when TK.sub.ij starts to be charged by performing DTS.sub.ij as given by the schedule; [0105] B.sub.ij: the time point when the charging of TK.sub.ij ends as given by the schedule; [0106] T.sub.ij: the time point when TK.sub.ij charged by performing DTS.sub.ij begins to feed a distiller as given by the schedule; [0107] : the oil residency time; [0108] f.sub.i: the most energy-effective oil transportation flow rate when i sets of machines are used at each pumping station; [0109] C.sub.i: the cost coefficient when i sets of machines are used at each pumping station;

Decision Variables

[0110] x.sub.ijh: the amount of oil in DTS.sub.ij to be transported by using the most energy-efficient flow rate with h sets of machines being used at each pumping station, iG, jN.sub.ki, and hS; [0111] .sub.i1: the time point when TK.sub.i1 starts to be charged by performing DTS.sub.i1 after oil transportation rate is regulated.

[0112] Given a schedule obtained by the control-theoretic-based approach, the above listed sets and parameters are known except C.sub.i. To formulate the addressed problem, one needs to determine C.sub.i. Assume that one unit power is consumed per one time unit when one set of machines is used at each pumping station. Then, when n sets of machines are used, the power consumed per one time unit is n units. Thus, the power consumed for transporting one unit of crude oil via a pipeline is n/f.sub.n, i.e., C.sub.n=n/f.sub.n is the cost coefficient. Then, one formulates the problem as follows.

[00002] $\begin{matrix} Minimize .Math. .Math. J = \underset{i G}{.Math.} .Math. .Math. \underset{j N_{ki}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. C_{h} .Math. x_{ijh} .Math. .Math. Subject .Math. .Math. to & (3.1) \\ _{11} A_{11} & (3.2) \\ \underset{h S}{.Math.} .Math. .Math. x_{1 .Math. jh} = V_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1} & (3.3) \\ _{11} + {.Math.}_{g = 1}^{j} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{1 .Math. gh} / f_{h} + T_{1 .Math. .Math. j}, j N_{k .Math. .Math. 1} & (3.4) \\ _{i .Math. .Math. 1} A_{i .Math. .Math. 1}, i G .Math. \ .Math. {1} & (3.5) \\ _{i .Math. .Math. 1}_{(i - 1) .Math. 1} + \underset{j N_{k (i - 1)}}{.Math.} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{(i - 1) .Math. jh} / f_{h}, i G .Math. \ .Math. {1} & (3.6) \\ \underset{h S}{.Math.} .Math. .Math. x_{ijh} = V_{ij}, i G .Math. \ .Math. {1}, j N_{ki}, & (3.7) \\ _{i .Math. .Math. 1} + \overset{j}{\underset{g = 1}{.Math.}} .Math. .Math. \underset{h S}{.Math.} .Math. .Math. x_{igh} / f_{h} + T_{ij}, j N_{ki}, i G .Math. \ .Math. {1} & (3.8) \\ x_{ijh} 0 .Math. .Math. and .Math. .Math._{i .Math. .Math. 1} 0 & (3.9) \end{matrix}$

[0113] Since C.sub.n represents the power consumed for transporting one unit of crude oil, by Objective (3.1), the total energy consumption is minimized by regulating oil transportation rate. Constraint (3.2) guarantees that oil transportation can be done when a charging tank is available as specified by the given schedule. Constraint (3.3) states the conservativeness property of crude oil in a DTS. Constraint (3.4) guarantees that the time delay by regulating the oil transportation is in a permissive arrange such that the oil residency time constraint is satisfied. Constraint (3.9) presents the non-negative requirement.

[0114] As above discussed, between two Groups G.sub.(i1) and G.sub.i, there is an idle time, or one has A.sub.i1>B.sub.(i1)(k(i1)). However, after delaying the transportation of oil of DTSs in G.sub.(i1), this may no longer hold. Since a pipeline cannot be used to perform two DTSs simultaneously, a DTS in G.sub.i can be performed only after all the DTSs in G.sub.(i1) have been executed. Constraints (3.5) and (3.6) state that when a DTS in G.sub.i is performed, the pipeline is available, and at the same time, charging tank TK.sub.i1 that is necessary for performing DTS.sub.i1 is released. Constraints (3.7) and (3.8) have the same meaning as that of (3.3) and (3.4).

[0115] Notice that the domain of x.sub.ijh's and .sub.i1's is real number, and the objective and constraints are linear. Hence, this is a linear programming formulation and can be efficiently solved by commercial software tools.

C. Industrial Case Study

[0116] This section uses a real-life scenario from a refinery in China to show the application of the proposed method. The refinery is located at the southern China and is one of the largest refineries in China. It has three distillers and a pipeline for delivering oil from storage tanks to charging tanks. These distillers are designed for different types of oil, multiple types of oil should be processed. The distance from the storage tanks to charging tanks is about 20 kilometers, so is the pipeline. The maximal oil processing capacity of the three distillers is 375 tons, 230 tons, and 500 tons per hour, respectively. For the pipeline, there are three sets of machines at each pumping station. If one set, two sets, and three sets of machines are put into operation, the corresponding most energy-efficient oil transportation rate via the pipeline is 20,000 tons, 30,000 tons, and 33,000 tons per day (or 833.333 tons, 1250 tons, and 1375 tons per hour), respectively.

[0117] As a routine, the refinery needs to present a short-term schedule every 10 days. The case presented here is one of the scenarios and a schedule is found by the control-theoretic-based method [Wu et al., 2008a, 2009, and 2012]. For the case problem, since the total oil processing capacity is 375+230+500=1105 tons per hour that is less than 1250 tons per hour by using two sets of machines at each pumping station, one can treat 1250 tons per hour as the maximal oil transportation rate via the pipeline for scheduling the process. In this way, the obtained schedule is shown in FIGS. 6 and 7.

[0118] For the obtained schedule, there are nine DTSs and they form two groups with G.sub.1={DTS.sub.12, DTS.sub.13, DTS.sub.14} and G.sub.2={DTS.sub.21, DTS.sub.22, DTS.sub.23, DTS.sub.24, DTS.sub.25}. Note that, among the DTSs, the oil transported to Charging Tanks #128 and #127 by performing DTS.sub.24, DTS.sub.25 is not processed during the current scheduling horizon but for the next horizon and the time when it is processed is unknown. Hence, one does not need to consider these two DTSs for energy reduction.

[0119] From the given schedule, by ST standing for storage tanks, one has DTS.sub.11={#2, ST, #180, 20000, 0, 16}, DTS.sub.12={#2, ST, #181, 20000, 16, 32}, DTS.sub.13={#1, ST, #127, 34000, 32, 59.2}, DTS.sub.14={#1, ST, #182, 20000, 59.2, 75.2}, DTS.sub.21={#6, ST, #116, 34000, 92.8, 120}, DTS.sub.22={#6, ST, #117, 34000, 120, 147.2}, DTS.sub.23={#1, ST, #129, 9000, 147.2, 154.4}, T.sub.11=130.4 hour, T.sub.12=217.4, T.sub.13=72, T.sub.14=162.7, T.sub.21=164, T.sub.22=232, and T.sub.23=216.03. Also by definition, one has C.sub.1=1/f.sub.1=0.0012 and C.sub.2=2/f.sub.2=0.0016. For this case problem, one has =6 hours. Then, one can formulate the linear programming model for the problem as follows.

Minimize J=C.sub.1(x.sub.111+x.sub.121+x.sub.131+x.sub.141+x.sub.211+x.sub.221+x.sub.231)+C.sub.2(x.sub.112+x.sub.122+x.sub.132+x.sub.142+x.sub.212+x.sub.222+x.sub.232)

subject to

[0120] .sub.110

[0121] x.sub.111+x.sub.112=20000

[0122] .sub.11+x.sub.111/833.333+x.sub.112/1250+6130.4

[0123] x.sub.121+x.sub.122=20000

[0124] .sub.11+x.sub.111/833.333+x.sub.112/1250+x.sub.121/833.333+x.sub.122/1250+6217.4

[0125] x.sub.131+x.sub.132=34000

[0126] .sub.11+x.sub.111/833.333+x.sub.112/1250+x.sub.121/833.333+x.sub.122/1250+x.sub.131/833.333+x.sub.132/1250+672

[0127] x.sub.141+x.sub.142=20000

[0128] .sub.11+x.sub.111/833.333+x.sub.112/1250+x.sub.121/833.333+x.sub.122/1250+x.sub.131/833.333+x.sub.132/1250+x.sub.141/833.333+x.sub.142/1250+6162.7

[0129] .sub.21.sub.11+x.sub.111/833.333+x.sub.112/1250+x.sub.121/833.333+x.sub.122/1250+x.sub.131/833.333+x.sub.132/1250+x.sub.141/833.333+x.sub.142/1250

[0130] .sub.2192.8

[0131] x.sub.211+x.sub.212=34000

[0132] .sub.21+x.sub.211/833.333+x.sub.212/1250+6164

[0133] x.sub.221+x.sub.222=34000

[0134] .sub.21+x.sub.211/833.333+x.sub.212/1250+x.sub.221/833.333+x.sub.222/1250+6232

[0135] x.sub.231+x.sub.232=9000

[0136] .sub.21+x.sub.211/833.333+x.sub.212/1250+x.sub.221/833.333+x.sub.222/1250+x.sub.231/833.333+x.sub.232/1250+6216.03

x.sub.ijh0 and .sub.i10

[0137] This problem is solved by using CPLEX with x.sub.111=x.sub.121=x.sub.141=x.sub.212=x.sub.222=x.sub.232=0, x.sub.112=20000, x.sub.122=20000, x.sub.131=17000, x.sub.132=17000, x.sub.141=20000, x.sub.211=34000, x.sub.221=34000, and x.sub.231=9000. The obtained schedule is illustrated by the Gantt chart in FIG. 8, where an orange bar presents that the oil is transported by using two sets of machines, while a green bar represents that one set of machine is used. By this schedule, A.sub.ij's and B.sub.ij's are modified as A.sub.12=16, A.sub.13=32, A.sub.14=66, B.sub.14=90, A.sub.21=92.8, A.sub.22=133.6, A.sub.23=174.4, and A.sub.24=185.2 such that it is feasible. Notice that A.sub.14+6=72=T.sub.13 to guarantee that the Oil Type #1 charged to Charging Tank #117 is usable at time T.sub.13. To do so, Oil Type #2 charged into Charging Tanks #180 and #181, and part of Oil Type #1 charged to #117 should be transported by using two sets of machines, otherwise an obtained schedule is infeasible.

[0138] By the obtained schedule, one has J=228. However, by the schedule given in FIG. 8, one has J=273.6. This implies that the objective is reduced by (273.6-228)/273.616.7%, i.e., significant energy is saved.

[0139] There are high fusion oil types whose fusion point is higher than 30 C. Hence, when such oil types are transported from one place to another via a pipeline, they need to be heated. Then, they are stored in tanks and cool down. When they are to be processed, they need to be heated again. Also, when the middle products come just from a device, they are very hot. Then, they are stored in tanks and cool down. However, when they go to the next processing step, they need to heat up. In this way, large amount of energy is consumed, which can be greatly saved if the operations are properly scheduled.

[0140] The embodiments disclosed herein may be implemented using general purpose or specialized computing devices, computer processors, or electronic circuitries including but not limited to digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA), and other programmable logic devices configured or programmed according to the teachings of the present disclosure. Computer instructions or software codes running in the general purpose or specialized computing devices, computer processors, or programmable logic devices can readily be prepared by practitioners skilled in the software or electronic art based on the teachings of the present disclosure.

[0141] In some embodiments, the present invention includes computer storage media having computer instructions or software codes stored therein which can be used to program computers or microprocessors to perform any of the processes of the present invention. The storage media can include, but is not limited to, floppy disks, optical discs, Blu-ray Disc, DVD, CD-ROMs, and magneto-optical disks, ROMs, RAMs, flash memory devices, or any type of media or devices suitable for storing instructions, codes, and/or data.

[0142] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Linear Programming-based Approach to Scheduling of Crude Oil Operations in Refinery for Energy Efficiency Optimization

Inventors

Cpc classification

Classification Explorer

Y02P90/80

GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Classification Explorer

Y02P80/10

GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Classification Explorer

F04B23/04

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

Classification Explorer

Y02P30/00

GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Classification Explorer

G06Q10/0631

PHYSICS

Classification Explorer

F04B2205/09

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

Classification Explorer

F04B49/065

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

Classification Explorer

F04B2207/041

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

International classification

Classification Explorer

G05D7/06

PHYSICS

Classification Explorer

G05B15/02

PHYSICS

Abstract

Claims

Description