A major problem in the design of pressure filters for use in high temperature applications is the maintenance of gas-tight seals between the inlet and outlet sides of the filter elements at the elevated operating temperatures. Filters must be fabricated and maintained at room temperatures, but the seals must remain effective as the temperature within the filter increases to a high level of say 1650 degrees F. or more. In addition, the different parts of the filter known in the prior art have been made of different materials which extend and contract by substantially different amounts as the respective temperatures vary. For example, where ceramic filter elements are supported by metallic structures special seals, such as described in U. S. Pat. No. 4,713,174, must be provided to maintain the integrity of the gas-tight seals. Where the filter elements are tubular and supported by a metal plate which separates the inlet and outlet sides of the associated filter tank, the support plate must be extremely thick, several inches, so as to support the weight of the filter elements when the support plate is at an elevated temperature. Moreover, such a plate exhibits substantial expansion between room temperature and the elevated operating temperatures. By way of example, a 304 stainless steel circular plate having a diameter of one-hundred ten inches at 70 degrees F. has a diameter of nearly one-hundred twelve inches at a temperature of 1,670 degrees F. Because of this substantial dimensional change, it has been necessary to provide special sealing structures, such, for example, as corrugated metal diaphragms, between the edges of the plates and the filter tanks to prevent the gas from passing around the edge of the plate from one side to the other.
USPTO Backgrounds
USPTO Backgrounds