Internal versus external reforming of natural gas for fuel cell

Natural gas contain hydrocarbons molecules consisting of hydrogen and carbon. Using a device called a fuel processor or a reformer, hydrogen can be split off the carbon in a hydrocarbon relatively easily and then use hydrogen to drive fuel cell.The reforming may be done internally or externally.Internal reforming increases stack cost by about 33%, but in small units this increase is more than offset by the cost of the reformer and its heat and steam supply. In large systems, a single central reformer may be cost effective, since the rate of internal reforming decreases with pressure. The process may therefore not to be too effective in pressurized stacks that may be cost effective in the multi megawatt size range. The four percentage points will then be more than made up for by the use of a steam bottoming cycle. To a first approximation, it is reasonable to assume that the internal and external reforming systems may result in about the same costs. External reforming will also certainly allow multi fuel capability, since internal reforming has so far only been shown suitable for natural gas and methanol. Heavy fuels, such as fuel oils, will require higher steam carbon ratios and specialized reforming systems, which will lower system efficiency by about 3% points compared with the value for external reforming natural gas units.