Abstract: A molten carbonate fuel cell using molten carbonate as an electrolyte, carbonate ions as electric conductor, and feeding a hydrogen-enriched gas to the anode and a mixture of air and carbon dioxide gas to the cathode has its output fall by degrees with operation. It is surmised that one of the causes of this problem is ascribable to the fact that the molten carbonate electrolyte moves during operation to destroy equilibrium in the boundary between the electrolyte and electrodes. After studies for measures against the problem, the inventor found that the output of a fuel cell which has fallen can be improved by shutting off part or all of the raaction gases or reducing their feed for a while, and then restoring. The purpose of the present invention is to offer a high-performance stable-output molten carbonate fuel cell and its operation control method, incorporating the above findings in its operation control system.

Abstract: A feed liquid (sugar-containing liquid) is continuously fed to a fermenter packed with an immobilized microorganism, which is obtained by immobilizing an alcohol producing microorganism on a carrier, for alcohol fermentation. The fermentation liquid is continuously taken out of said fermenter and is heated to a temperature of 35.degree. to 80.degree. C. This liquid is introduced into a flash tank maintained at reduced pressure and is divided into an alcohol-containing steam and a liquid. The alcohol-containing steam is condensed and recovered as alcohol, while the separated liquid is cooled and is cycled back to said fermenter.