387261 Hydrogen Production from Renewable and Waste Oils
Fuel cells are a high efficiency, small footprint, low noise technologies that can be used to generate electricity for mobile and stationary power. While considerable advances have taken place in the development of fuel cells that can use hydrocarbons and other feeds (e.g. direct methanol FC), the best feedstock is still pure hydrogen. The most common technologies for hydrogen production at industrial scales are steam methane reforming (SMR), steam naphtha reforming, hydrocarbon partial oxidation (POX) and to a lesser extent gasification. In general, petroleum naphtha is the heaviest feedstock that can be used in conventional fixed bed tubular steam reformers, and even then high steam to carbon ratios are required to avoid catalyst coking. While heavy oils such as petroleum residuum, oil sand bitumen and waste oil can be gasified, gasification plants are expensive and require an air separation plant if nitrogen is to be avoided in the syngas. These heavy feedstocks cannot be steam reformed using conventional fixed bed processes.
TDA Research Inc. has developed a new technology based on chemical looping steam reforming that generates hydrogen from low cost heavy feedstocks such as vacuum residuum, oil sand bitumen, raw biomass pyrolysis oil, etc., at a cost that is considerably lower than hydrogen produced using conventional technologies (SMR, POX or gasification). In TDA’s process the heavy feed is steam reformed using a nickel catalyst to produce syngas without catalyst deactivation and without the need for an oxygen plant (required when using gasifiers). Residuum and other difficult feedstocks can be steam reformed using nickel catalysts without deactivation because the system uses two fluidized beds with periodic catalyst regeneration using air. Heavy feed and steam are fed into a fluidized bed steam reformer where syngas is generated at ~870°C using a Ni catalyst. The syngas typically contains ~70 vol% H2 (dry basis). Because the contact time in the steam reformer is on the order of minutes, not enough carbon builds up to cause irreversible catalyst deactivation. The catalyst is then regenerated in a separate fluidized bed by burning off the coke (and any sulfur) with air. In the laboratory, this is done using a single reactor with a nitrogen purge between reforming and regeneration steps; however, in an industrial setting, a circulating fluidized bed system would be used. Burning off coke in the regenerator reheats the catalyst to ~900°C for the next reforming step (a small amount of raw feedstock can be burned in the regenerator to increase the temperature if there is not enough coke on the catalyst to generate the required heat). The hot nickel catalyst returning to the reformer is present as catalytically inactive NiO but is quickly reduced to catalytically active nickel metal by the hydrocarbons in the feed and steam reforming resumes.
TDA has conducted extensive testing using atmospheric and vacuum residuum, raw biomass pyrolysis oil and dilbit (oil sane bitumen diluted with 30% condensate to make it fluid) with no catalyst deactivation in over 600 hours of testing. Steam to carbon ratios are typically between 3 and 5, even when steam reforming petroleum residuum.
See more of this Group/Topical: Topical Conference: Advanced Fossil Energy Utilization