Shu Jiangzhou

Mathematical Modeling and Simulation of SWRO Process Based on Simultaneous Method

Reverse osmosis (RO) technique is one of the most efficient ways for seawater desalination to solve the shortage of freshwater. For prediction and analysis of the performance of seawater reverse osmosis (SWRO) process, an accurate and detailed model based on the solution-diffusion and mass transfer theory is established. Since the accurate formulation of the model includes many differential equations and strong nonlinear equations (differential and algebraic equations, DAEs), to solve the problem efficiently, the simultaneous method through orthogonal collocation on finite elements and large scale solver were used to obtain the solutions. The model was fully discretized into NLP (nonlinear programming) with large scale variables and equations, and then the NLP was solved by large scale solver of IPOPT. Validation of the formulated model and solution method is verified by case study on a SWRO plant. Then simulation and analysis are carried out to demonstrate the performance of reverse osmosis process; operational conditions such as feed pressure and feed flow rate as well as feed temperature are also analyzed. This work is of significant meaning for the detailed understanding of RO process and future energy saving through operational optimization.

Operational Optimization of Large-Scale Parallel-Unit SWRO Desalination Plant Using Differential Evolution Algorithm

A large-scale parallel-unit seawater reverse osmosis desalination plant contains many reverse osmosis (RO) units. If the operating conditions change, these RO units will not work at the optimal design points which are computed before the plant is built. The operational optimization problem (OOP) of the plant is to find out a scheduling of operation to minimize the total running cost when the change happens. In this paper, the OOP is modelled as a mixed-integer nonlinear programming problem. A two-stage differential evolution algorithm is proposed to solve this OOP. Experimental results show that the proposed method is satisfactory in solution quality.

Study on the Measurement of Air Resistance of Plate Fin Heat Exchanger in an Open Environment

Abstract A test system for the air resistance of plate fin heat exchanger (PFHE) in an open environment was developed. A combination of three nozzles is used to measure the air volume flowrate through the PFHE. The combination of three nozzles keeps the pressure difference between their two ends less than 800Pa, therefore a high precision measurement is implemented. The influence of temperature & humidity on the density of wet air in the open environment is discussed, and the variety of Reynolds number with the change of humidity is analysed. A compensation formula is present to cope with the fluctuation of temperature and humidity. An expert fuzzy-PID controller is developed to control the air volume flowrate with a faster speed and higher precision. The results show that the performance of the proposed measurement system is satisfied.

Research on air volume control algorithm for air resistance of plate fin heat exchanger

An air resistance test system is established for the plate fm heat exchanger. A fuzzy PID controller is proposed to realize the quick, accurate, and efficient control of air volume for the plate fin heat exchanger. The simulation results show that the proposed fuzzy PID controller not only can improve the control quality of system, but also the system has better dynamic tracking characteristics of the load change.

A Rescheduling Approach for a Large-scale Reverse Osmosis Desalination Plant under Uncertain Fresh Water Demand

Abstract The scheduling problem of a large-scale seawater reverse osmosis (SWRO) desalination plant is considered as a mixed-integer nonlinear programming problem (MINLP) over the time horizon. It is hard to find out the exact solution directly, especially when the working environment is changing. So, when the variables are changed, it is needed to find out a new scheduling plan quickly to meet the changes. In this paper, a rescheduling model of operational optimization of a large-scale SWRO is built, which is a bi-objective optimization with criterions of efficiency and stability. A rolling horizon approach (RHA) is used to make the solution meet the requirements of accuracy and rapidity. The framework of RHS is structured and a two-stage differential evolution (TSDE) algorithm is used to compute the solution. A simulation based on a real case with fluctuations in freshwater demand in Liuheng Seawater Desalination Plant in Zhejiang province was made, and the results show that the performance of the proposed algorithm is satisfied.

Rolling horizon scheduling procedure for SWRO desalination plant under uncertain freshwater demand

The rescheduling problem of seawater reverse osmosis (SWRO) desalination plant under uncertain freshwater demand is studied. A rescheduling model of this problem is built, which is a bi-objective optimization with criterions of efficiency and stability. A rolling horizon scheduling (RHS) procedure is used to solve this problem. The framework of RHS is structured. A differential evolution (DE) algorithm is used to compute the solution, and its steps are described. The simulation results of a large-scale SWRO desalination plant with fluctuations in freshwater demand show that the performance of RHS is satisfied.

A Dynamic Optimization Strategy for the Operation of Large Scale Seawater Reverses Osmosis System

In this work, an efficient strategy was proposed for efficient solution of the dynamic model of SWRO system. Since the dynamic model is formulated by a set of differential-algebraic equations, simultaneous strategies based on collocations on finite element were used to transform the DAOP into large scale nonlinear programming problem named Opt2. Then, simulation of RO process and storage tanks was carried element by element and step by step with fixed control variables. All the obtained values of these variables then were used as the initial value for the optimal solution of SWRO system. Finally, in order to accelerate the computing efficiency and at the same time to keep enough accuracy for the solution of Opt2, a simple but efficient finite element refinement rule was used to reduce the scale of Opt2. The proposed strategy was applied to a large scale SWRO system with 8 RO plants and 4 storage tanks as case study. Computing result shows that the proposed strategy is quite effective for optimal operation of the large scale SWRO system; the optimal problem can be successfully solved within decades of iterations and several minutes when load and other operating parameters fluctuate.