Fast Degas Carbon Dioxide Evaporator

Two reasons exist for the rapid degassing of Hydrogen cooled generators. The first is an upset condition which could cause an unsafe condition or generator failure if the Hydrogen is not removed. The second is the time savings that can be recognized by reducing the time required to fully purge the generator and refill during an unplanned or planned outage. A generator bearing fire is an example of the first condition where the ability to remove the Hydrogen and purge with Carbon Dioxide rapidly would result in a significant reduction in the risk of a catastrophic situation. Current purge operations typically require many hours for the gas change from Hydrogen to Carbon Dioxide during maintenance outages. This new system reduces the time required for this step to less than 20 minutes. Times for refilling can also be reduced by similar amounts. This time can be extremely valuable during peak generation periods. The Carbon Dioxide vaporizer systems that have been installed previously have been limited by the rate they can vaporize the Carbon Dioxide and feed the gas to the generator without freezing. The system described uses flow controls, a large heater and backup Carbon Dioxide storage to perform the necessary operations quickly. The system can be operated manually or fully automatic. Automatic operation is preferred for the safety concerns since any fire or other upset would likely occur in the area of the equipment and time would be of the essence. The system described has been installed and tested in a number of operating plants and is performing satisfactorily.