Energy efficient multi-stage water gas shift reaction

In a process for the energy efficient content of a multi-stage water gas shift reaction including the steps of furnishing a carbon monoxide-containing feed gas stream and water to a high-temperature shift reactor stage for exothermically and catalytically reacting a portion of the carbon monoxide and water to produce a carbon dioxide and hydrogen enriched exhaust gas stream and introducing said exhaust gas stream into a low-temperature shift reactor stage for exothermically and catalytically reacting said exhaust gas stream to produce a product gas stream further enriched in carbon dioxide and hydrogen and cooling said product gas stream, the improvement comprising:

• furnishing said feed gas stream to said high temperature shift reactor stage at an inlet temperature such that the temperature of the exhaust gas stream is at the maximum temperature at which the integrity of the catalyst is maintained;
• passing a heat exchange fluid in heat transfer relationship with said feed gas stream and successively passing said heat exchange fluid in heat transfer relationship with at least said exhaust gas stream to recover thermal energy therefrom by concurrently cooling said feed and exhaust gas streams and heating said heat exchange fluid;
• and
• converting at least a portion of said recovered thermal energy to mechanical energy.

In a process for the energy efficient conduct of a multi-stage water gas shift reaction including the steps of furnishing a carbon monoxide-containing feed gas stream and water to a high-temperature shift reactor stage for exothermically and catalytically reacting a portion of the carbon monoxide and water to produce a carbon dioxide and hydrogen enriched exhaust gas stream and introducing said exhaust gas stream into a low-temperature shift reactor stage for exothermically and catalytically reacting said exhaust gas stream to produce a product gas stream further enriched in carbon dioxide and hydrogen and cooling said product gas stream, the improvement comprising:

• introducing said feed gas stream upstream of said high-temperature shift reactor stage at a temperature substantially above said high-temperature shift reactor feed gas inlet temperature,
• furnishing said feed gas stream to said high temperature shift reactor stage at an inlet temperature such that the temperature of the exhaust gas stream is at the maximum temperature at which the integrity of the catalyst is maintained;
• passing water in heat transfer relationship with at least said higher temperature feed gas stream and said exhaust gas stream to recover thermal energy therefrom by concurrently cooling said feed and exhaust gas streams and heating said water;
• heating said water by heat exchange relationship with said higher temperature feed gas stream and said exhaust gas stream, said heated water being vaporized to steam by said heat exchange relationship with said feed gas stream and said steam being superheated by said heat exchange relationship with said exhaust gas stream.