Multiperiod Mixed-integer Nonlinear Programming Model Research Articles

Offshore oil production planning optimization: An MINLP model considering well operation and flow assurance

With the increasing energy requirement and decreasing onshore reserves, offshore oil production has attracted increasing attention. A major challenge in offshore oil production is to minimize both the operational costs and risks; one of the major risks is anomalies in the flows. However, optimization methods to simultaneously consider well operation and flow assurance in operation planning have not been explored. In this paper, an integrated planning problem both considering well operation and flow assurance is reported. In particular, a multi-period mixed integer nonlinear programming (MINLP) model was proposed to minimize the total operation cost, taking into account of well production state, polymer flooding, energy consumption, platform inventory and flow assurance. By solving this integrated model, each well's working state, flow rates and chemicals injection rates can be optimally determined. The proposed model was applied to a case originated from a real-world offshore oil site and the results illustrate the effectiveness.

MINLP Model for Reverse Osmosis Network Design under Time-Variant Operation Constraints

Reverse osmosis (RO) is a very well-established technology for water desalination. Commercial RO systems are composed of several numbers of RO passes with auxiliary equipment such as high-pressure pumps and pressure-exchanger units to facilitate the separation, and to deliver clean water. Available design models for the RO network represent mixed integer nonlinear programming (MINLP) formulations. In addition, the existing RO design MINLP models are static in nature. These models are not suitable for RO network design under time-variant constraints. In this study, a multiperiod MINLP model is detailed for the RO network design. High-level design decision variables are related to the RO network configuration and equipment sizing, which are independent of time. These decisions are modeled by discrete and continuous variables. Low-level time-variant decision variables are related to the RO network operation and modeled by continuous variables. The operation decision variables are constrained by the design variables through different time periods to satisfy water-demand constraints. In addition, several correlations are considered in this study to estimate water and RO transport properties during the separation process. Case studies are analyzed to show the application of the mathematical programming model.

Piecewise Linear Approximation Based MILP Method for PVC Plant Planning Optimization

This paper presents a new piecewise linear modeling method for the planning of polyvinyl chloride (PVC) plants. In our previous study (Ind. Eng. Chem. Res., 2016, 55, 12430−12443, DOI: 10.1021/acs.iecr.6b02825), a multiperiod mixed-integer nonlinear programming (MINLP) model was developed to demonstrate the importance of integrating both the material processing and the utility systems. However, the optimization problem is really difficult to solve due to the process intrinsic nonlinearities, i.e., the operating cost or energy-consuming characteristics of calcium carbide furnaces, electrolytic cells, and CHP units. The present paper intends to address this challenge by using the piecewise linear modeling approach that provides good approximation of the global nonlinearity with locally linear models. Specifically, a hinging hyperplanes (HH) model is introduced to approximate the nonlinear items in the original MINLP model. HH model is a kind of continuous piecewise linear (CPWL) model, which is proven to be...

Optimal Synthesis and Operation of Wastewater Treatment Process with Dynamic Influent

This work addresses the problem of optimal synthesis and operation of wastewater treatment processes considering multiscenario influent streams under different discharge standards and penalty rates of noncompliant emissions. We develop a general disjunctive programming model to address this problem, which is then reformulated as a multiperiod mixed-integer nonlinear programming model using hull reformulation for the disjunctions. To solve the resulting model to global optimality, we propose a Lagrangean-based decomposition algorithm. Numerical studies verify the effectiveness of the algorithm, and comparison studies provide useful management insights for policy makers.

Multiperiod Planning of a PVC Plant for the Optimization of Process Operation and Energy Consumption: An MINLP Approach

This work addresses the integrated optimization of both the plant-wide material processing system and the utility system for a polyvinyl chloride (PVC) plant. In the plant-wide material processing system, vinyl chloride monomer (VCM) production process and VCM polymerization process are optimized to determine production allocation and switching operation of parallel equipment as well as raw material supply arrangement. In the utility system, power generation/supply plan is determined by combined heat and power (CHP) units and the state grid. The nonlinear electricity consuming characteristics of calcium carbide production process, CHP process, and electrolysis process are modeled based on the industrial data. A multiperiod mixed-integer nonlinear programming (MINLP) model of a PVC plant by calcium carbide method is proposed with the intent to enhance the profit and reduce the energy consumption. The proposed MINLP model is successfully applied to two cases originated from a real-world industrial plant in ...

Designing a Total Site for an entire lifetime under fluctuating utility prices

This paper describes a synthesis of Total Site in order to obtain additional energy savings by process-to-process heat integration. Enhanced Heat Integration and economically viable designs can be obtained by establishing an appropriate trade-off between the operating cost and the investment. The aim of this work was to improve the modeling of the Total Site by including proper pressure levels selection for intermediate utilities, preheating of intermediate utilities because of incomplete condensate recovery, pipeline layout design, and optimal pipe design with optimal pressure/temperature drops and optimal insulation thickness and heat losses during transportation along the pipes. Additionally, future utility prices are considered when synthesizing the Total Site as they are expected to influence the trade-off between investment and operating cost. A stochastic multi-period mixed-integer nonlinear programming model for the optimal synthesis of Total Site over its entire lifetime has been developed by including all the above-mentioned design aspects.

An Efficient Multiperiod MINLP Model for Optimal Planning of Offshore Oil and Gas Field Infrastructure

In this paper, we present an efficient strategic/tactical planning model for offshore oilfield development problem that is fairly generic and can be extended to include other complexities. The proposed multiperiod nonconvex MINLP (mixed integer nonlinear programming) model for multifield site includes three components (oil, water, and gas) explicitly in the formulation using higher order polynomials, avoiding bilinear and other nonlinear terms. With the objective of maximizing total NPV for long-term planning horizon, the model involves decisions related to FPSO (floating production, storage, and offloading) installation and expansions, field–FPSO connections, well drilling, and production rates in each time period. The model can be solved effectively with DICOPT for realistic instances and gives good quality solutions. Furthermore, it can be reformulated into an MILP after piecewise linearization and exact linearization techniques that can be solved globally in an efficient way. Solutions of realistic in...

Synthesis of multi-stream heat exchanger network for multi-period operation with genetic/simulated annealing algorithms

The multi-period synthesis of multi-stream heat exchanger network (MSHEN) can be formulated as a mixed integer nonlinear programming (MINLP) model and the obtained MSHEN is over-synthesized for all operational period. In this paper a novel strategy for synthesizing flexible MSHEN under multi-period operation that involves specified changes in stream temperatures and flow rates is presented. In the first stage, the multi-period MSHEN is over-synthesized by the temperature–enthalpy ( T– H) diagram method based on the stream pseudo-temperature. Compared with the superstructure-based multi-period MINLP model, the decision variables of the simultaneous multi-period NLP model proposed are only the stream heat transfer temperature difference contributions. The model features that the size and the complexity of the problem are reduced significantly and the feasibility of the initial feasible solutions are guaranteed, which will enhance the calculation efficiency of the problem. In the second stage, the optimal MSHEN obtained in the first stage is improved to overcome the problem of over-synthesis. The structure of the over-synthesis MSHEN is retained and each heat exchanger area is optimized considering the multi-period operation in order to make the MSHEN less costly. The objective in both stages is the total annual cost of MSHEN and the global solution can be guaranteed by genetic/simulated annealing algorithm (GA/SA) at high probability. Finally, two examples are illustrated to demonstrate the performance of the strategy for multi-period MSHEN synthesis.

A Lagrangean Decomposition Heuristic for the Design and Planning of Offshore Hydrocarbon Field Infrastructures with Complex Economic Objectives

In this work, we present a multiperiod mixed-integer nonlinear programming model for the long-term design and planning of offshore hydrocarbon field infrastructures with complex economic objectives. We show that when complex fiscal rules, such as tariff, tax, and royalty calculations are added to the model, substantial increases in the net present value of the project are obtained. However, including these calculations leads to more than an order of magnitude increase in the computational effort required. To address this problem, we propose a specialized heuristic algorithm that relies on the concept of Lagrangean decomposition. We present an iterative scheme where feasible solutions are postulated from the Lagrangean decomposition, and multipliers are updated through a subgradient method. Results show that for moderately sized models up to 2 orders of magnitude of reduction in solution time is obtained compared to the full-space solution. Larger problems that could not be solved in 5 days of computation ...

An Iterative Aggregation/Disaggregation Approach for the Solution of a Mixed-Integer Nonlinear Oilfield Infrastructure Planning Model

A multiperiod mixed-integer nonlinear programming model for offshore oilfield infrastructure planning is presented where nonlinear reservoir behavior is incorporated directly into the formulation. Discrete decisions include the selection of production platforms, well platforms and wells to be installed/drilled, and the drilling schedule for the wells over the planning horizon. Continuous decisions include the capacities of the platforms and the production profile for each well in each time period. For the solution of this model, an iterative aggregation/disaggregation algorithm is proposed in which logic-based methods, a bilevel decomposition technique, the use of convex envelopes, and aggregation of time periods are integrated. Furthermore, a novel dynamic programming subproblem is proposed to improve the aggregation scheme at each iteration in order to obtain an aggregate problem that resembles the disaggregate problem more closely. A number of examples are presented to illustrate the performance of the proposed method.

A multiperiod MINLP model for the synthesis of flexible heat and mass exchange networks

This paper addresses the problem of how to synthesize mass and heat exchange processes, in which stream flowrates and their inlet compositions and temperatures may vary according to a set of discrete values. A unified hyperstructure representation of mass and heat exchange alternatives is introduced to account for all mass and heat integration possibilities. A multiperiod mixed integer nonlinear programming (MINLP) model is then developed, where a total annualized cost is minimized by balancing capital investment cost (of the heat and mass exchange equipment and their interconnections) to operating cost (of the hot-cold utilities, mass separating agents, etc.). As illustrated with the example problems, the proposed model can be effectively employed for the synthesis of flexible heat exchanger networks (HENs) and mass exchanger networks (MENs) separately or, for the synthesis of separation processes involving both heat and mass transfer.