Dynamic modeling of multi-effect desalination with thermal vapor compressor plant

• Multi-Effect Desalination (MED) is one of the most common techniques that provides a considerable quantity of potable water.
• The aim is to obtain a dynamic model for MED plants in such a way that the behavior of the system in different working conditions is predicted.
• The model is simulated with the MATLAB/SIMULINK software to simulate the transient behavior of the MED plants under various conditions.
• This model is validated with actual data from an industrial plant that operate in the South of Iran.

This paper aims to develop a mathematical dynamic model for multi-effect desalination (MED) with thermal vapor compressor plant. The developed model is based on coupling the dynamic equations of material, salt and energy balance of the system. Towards this, the plant is divided into three main subsystems; evaporators (effects), condenser and thermo-compressor. Moreover, each effect is considered to be a dynamic system of order three that represents the dynamic behavior of the evaporator. Using material, salt and energy balance physical relations, three dynamic equations are obtained for each effect where they are modified to get the state equation of the effect. This procedure is repeated for the condenser while in the thermo-compressor only static equations are considered due to its fast dynamic. The proposed model is validated by actual data of an operating plant in Kish Island (in south of Iran). The transient and steady state behavior of the model is more investigated by simulating some conditions like applying disturbance and changing the operating point which can be happened in real conditions. Due to high performance of the proposed model, it can be used in optimal designing of the MED plants and control applications as well.