Dynamic simulation of the sour water stripping process and modified structure for effective pressure control

As a result of stringent government regulations regarding air and water Pollution, the sour water stripping process has emerged as an important process in petroleum refineries and coke-making works industries. The dynamics of the sour water stripping process have not been revealed as sour water is a weak electrolyte and has nonlinear characteristics. Moreover, in a real plant, there are several problems such as plugging, excessive use of steam, and difficulty in controlling the column pressure. This paper tries to solve these problems and examines controllability. Steady state simulation is used to find the optimal operating conditions. However, the results from the steady state simulation cannot be applied to the actual system directly since the concept of controllability is ignored. Dynamic simulation is used to examine the controllability and the capability of disturbance rejection and to cope with abnormal situations which may occur in real plant. In the actual system, when the ammonia composition in feed increases, the column pressure increases rapidly. The conventional process cannot control the column pressure properly and the system becomes unstable. The proposed structure, with an inter-cooler, gives better performance than the conventional one.