Coupling power generation with syngas-based chemical synthesis

Renewable electricity generation is on the advance worldwide. Fossil-fuel power plants have to compensate for the growing intermittency in the electric grid by operating with highly flexible loads. During periods of strong penetration by renewable energy sources, this will lead to more frequent power plant shutdown and startup events at the expense of lifetime and economic efficiency. A further improvement in load elasticity (lowering the minimum load) can be achieved by coupling power generation with syngas-based chemical synthesis as a power sink with additional synergies, as already described in the literature. For the first time, this work uses simulation to investigate how this concept influences the load-dependent power plant process - referring to an existing and a future coal-fired power plant, each combined with different chemical synthesis scenarios. The major finding is the identification of interfaces and the discovery that the streams of steam, residue and gases thus can be handled well across the load. One benefit is a saving in coal feed by the external heat input, allowing CO2 emissions at the power plant to be mitigated, although there is a slight loss in efficiency via coupling. The key advantage is a notable lowering in the minimum power feed to the electric grid (in this study by 5-23%) which in turn can improve the power plant's availability significantly.