Process Integration of a Gas to Liquid Plant and a Power Plant

Abstract

The gas-to-liquid (GTL) industry is vulnerable to the variation of the oil and gas market price. This shortcoming has forced future GTL projects to be suspended and even cancelled. As one of the measures to overcome the challenge the GTL industry faces, process integration of a GTL plant and a power plant via a F-T tail gas supply line is proposed. The process integration allows an integrated plant to adjust F-T tail gas distribution that affects the production rates of two products, oil and electricity. The first result shows that recycling F-T tail gas to the GTL plant is superior to supplying tail gas to the power plant in the perspectives of power generation and utility consumption. However, recycling all F-T tail gas to the GTL plant is not feasible due to the constraints that both plants require. One constraint is the requirement to reduce nitrogen compound build up in F-T tail gas, whereas the other constraint is the limitation of modified wobbe index range from gas turbine fuel specification. Since the latter constraint covers the former constraint, the modified wobbe index limitation governs the allowable range of F-T tail gas fraction. Despite the constraints, the integrated plant still has the flexibility on the adjustment of tail gas distribution. Within the feasible region, the integrated plant can be designed and operated by balancing multiple parameters including power generation, utility consumption and nitrogen compound buildup that have a trade-off relationship.