Dra. Narváez-Dinamarca, Ana

Polygeneration systems have been shown to be a flexible arrangement which can meet seasonal product demands for electric power, fuels and chemicals. This is especially relevant for small markets such as isolated small-medium size communities demanding electricity, and fuels. This work is focused on the feasibility of a polygeneration system based on a single-step DME plant to produce 200,000 tonnes/year of DME and 200 MW of electricity. An economic analysis is carried out to assess different configurations and feedstocks for syngas production. The DME-production was simulated at different possible recycle ratios and under the condition of potentially reduced catalyst performance. In all cases, the once-through polygeneration system showed significant improvement over all other configurations e up to 11.6% reduction in the amount of synthesis gas required to produce DME and power e with a corresponding reduction in “wasted” feed leaving as effluent CO2. The flexibility of an integrated system meant that, in cases of decreased catalyst activity or selectivity, the advantages of the integrated system over standalone configurations are even greater e up to 18.6%. Moreover, polygeneration systems show further economic advantages depending upon the selling price of electricity for both fossil fuel and biomass sources of the syngas feedstock.

The feasibility and attractiveness of the integrated production of chemicals and electrical power is dependent upon on the nature of the products and their demands. This study focuses on the small-to-medium scale combined production of methanol (200,000 tonnes/year) and electrical power (200 MW). The integrated system considers both recycle (recycle ratio = 5) and once-through (no recycle) modes of methanol synthesis. The results of simulations show that, when compared to separate stand-alone plants for methanol and power production, the integrated systems show lower consumption of total fresh synthesis gas for recycle and once-through operation of 2.8% and 3.7%, respectively. In addition, simulations show that the advantage over stand-alone plants increases further in the face of decreasing catalyst activity or selectivity, rising to over 10% in several scenarios. This is because the off-spec material from methanol production in an integrated plant can be diverted to the power generation section of the plant. These savings in operating costs are over and above the substantial capital cost savings which can be realized in the design of a once-through integrated plant.