Self-Optimizing Control Structure Design for a Staged Fischer-Tropsch GTL Process – Steady State Analysis

فاقد چكيده فارسي

GTL process is indirect conversion of natural gas to transportable liquid hydrocarbons through Fischer-Tropsch (FT) reactions. Long chain hydrocarbons (wax) is one of the main and valuable products in GTL processes. In this study, optimization of a staged GTL process while natural gas feed is a degree of freedom is considered with maximizing wax flowrate as the objective function. The target is to design a self-optimizing control structure which works near optimum in a wide range of operation without the need to update the controlled variables (CVs) setpoints or change the control loops. Maximum possible throughput and the bottleneck of the process are found. Five self-optimizing CVs (SOC variables) including four active constraints are proposed for optimal operation of this process at maximum throughput point. Five manipulated variables (MVs) are proposed to control these SOC variables. CO2 recovery percentage from fresh synthesis gas is the only unconstrained degree of freedom, which is proposed as the throughput manipulator (TPM) of this plant. TPM sets the production rate of the process