Environment and chemical process modeling/design engineering laboratory is focusing on the current issues about energy, environment, and chemical processes using process system engineering approaches. The main research themes are process modeling, process design, and optimization for designing the best operating condition and design candidate in full-scale chemical systems. These researches have been conducted through programming languages such as MATLAB, Simulation programs for describing chemical processes are developed based on the modeling equations. Energy and cost optimization can be carried out from the developed simulation program. Our current research topics are seawater/brackish water desalination system with high energy-efficiency/low cost, water/electricity production system using low-grade thermal energy, hydrogen/water nexus system, and crystallization process modeling.