Adding value to coal as feedstock for a hydrogen plant

摘要

Coal is the largest fossil energy resource and, in spite of its 19th century image, coal has proven itself in the last quarter of the 20th century as a modern and remarkably cost-effective fuel for generating electric power. Today, with increasing concern over greenhouse gases, coal needs to overcome the obstacle of being the most carbon intensive energy source there is. To clear this hurdle and provide a modern and environmentally viable energy resource based on abundant coal reserves is the goal of Vision 21. The strategy of Vision 21 rests on the production of high quality gaseous fuels like hydrogen that could either leave the plant or be used in the production of electricity by highly efficient fuel cell stacks. Here the authors outline three processing steps, that combined or separately can greatly reduce greenhouse gas emissions from coal. First, they propose to perform the gasification and water-gas shift reaction for producing hydrogen from coal with calcium oxide as a getter for carbon dioxide. This provides an efficient means to collect the carbon dioxide for reuse or disposal. Simultaneously, the carbonation facilitates the formation of hydrogen and provides the energy necessary to drive the hydrogen producing reaction to completion. In the second step, the calcium oxide would be regenerated either by a conventional calcination process or, as they propose to investigate, in a solar furnace. The latter approach would lead to a novel hybrid solar/fossil power plant that derives about 30% of its energy output from solar energy. Finally, they propose to develop a solar driven process, that generates methanol from waste carbon dioxide. In a photolytic process, CO(sub 2) is broken up into CO and O(sub 2). The CO is then reacted with water in a conventional process to form methanol.