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Clamping Strategies for Ceramic-to-Metal Seals

IP.com Disclosure Number: IPCOM000021003D
Publication Date: 2003-Dec-16
Document File: 4 page(s) / 143K

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Clamping Strategies for Ceramic-to-Metal Seals

Oxygen can be recovered from air at high temperatures by passing hot, oxygen-containing gas, preferably air, over non-porous, mixed conducting ceramic membranes. These membranes, known in the art generically as ion transport membranes (ITMs), utilize an oxygen partial pressure differential across the membrane to cause oxygen ions to migrate through the membrane.

Membranes can be fabricated as tubes or flat plates that are arranged in modules for efficient contact with the hot compressed air. High-purity oxygen permeate and nitrogen-enriched non-permeate products are withdrawn from the modules. A comprehensive review of ion transport membranes is given by J. D. Wright and R. J. Copeland in Report No. TDA-GRI-90/0303 prepared for the Gas Research Institute, September 1990.

Ceramic membrane modules for oxygen production typically operate with a pressure differential between their exteriors and interiors. Product oxygen is collected either from the exterior or interior of the module, and these surfaces must be isolated to prevent contamination or product loss. Ceramic modules typically terminate in a tubular ceramic port through which the product oxygen is removed from the interior of the device. The product is conveyed or collected in metal piping/ductwork to a downstream delivery point. The transition between the ceramic tube and the metal piping/ductwork requires a ceramic-to-metal seal. Ceramic-to-metal seals are a key component of ceramic membrane devices (modules) for efficient oxygen production.

There are numerous seal designs. Most rely on some sort of mechanical clamping mechanism to force the ceramic against a metal flange or metal tube sheet. The transfer of force between the tubular ceramic port and the metal flange or tube sheet is often mediated by some type of gasket material.

The role of the clamp is to provide the minimum pressure to the ceramic and/or metal components at the ceramic-metal joint that will effect a good seal without applying excessive or uneven force. Either of the latter conditions could lead to ceramic component failure or loss of seal. In addition to purely mechanical considerations, ceramic membrane module seals and clamps must be designed to operate at temperatures up to 1100 C, depending upon whether the seal region is thermally isolated from the membrane module.

A number of conventional and unconventional approaches to creating an effective clamping device exist. The following examples of clamps for ceramic-to-metal seals are described below he...