A refrigerated gas plant (RGP) produces sales gas (SG), which is the preferred fuel of power plants. Sustaining SG production at an optimum cost is crucial to an RGP posed with operational challenges. These challenges may be alleviated by adopting a model predictive control (MPC) scheme. In this research, a 2x2 constrained MPC scheme was developed. RGP process dynamics were approximated by first-order-plus-time-delay models. Performance of the MPC scheme was compared with a decentralised proportional integral (PI) control scheme in set point tracking. Although the PI controller seemed to perform better than the MPC controller, its performance was achieved at a higher operating cost and hence reduced RGP profit.