The reliability of fuel cell systems, such as a solid oxide fuel cell (SOFC) system, greatly depends on the presence and concentration of undesirable constituents in the fuel stream. Undesirable constituents, such as moisture, oxygen, siloxanes, and sulfur (including sulfur compounds), may degrade the fuel cell stack's performance and cause irreversible damage resulting in decrease efficiencies and costly replacement. Specifically, when using natural gas as a fuel, fuel cell systems require desulfurization. Passing fuel through desulfurizer sorbent beds is one way to remove sulfur and sulfur compounds from fuel prior to use in a fuel cell.
However, the sorbent beds (e.g., absorbent and/or adsorbent beds) have a finite life and once the sorbent bed is exhausted, sulfur may pass through the sorbent bed without being adsorbed and reach the fuel cell stack, causing permanent damage. Even if sorbent beds are replaced prior to exhaustion, there may be underutilized portions of the sorbent bed increasing the cost of sorbent bed replacement. Additionally, other undesirable constituents not filtered by the desulfurizer sorbent beds may cause damage to the fuel cell stack, shortening its operational life.
In addition, general sorbent beds include large vessels to contain loose sorbent material. The vessels are oriented vertically, and a gas is fed through either the top or bottom of the vessel, in order to assure proper dispersion of a gas through the sorbent material. Accordingly, in order to replace the sorbent material, the entire vessel must be disconnected and removed, which is a difficult and time consuming process.