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Catalysts are the key to using biomass as fuel

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Catalysts are the key to using biomass as fuel

December 16, 2012 - 14:00
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BRUSSELS, Dec. 17, 2012 (RISI) -The elusive goal of a refinery with biomass as a feedstock has moved a step closer to reality, thanks to technology developed by the Gas Technology Institute (GTI) of Des Plaines, IL,and Houston-based Catalytic Research Institute (CRI).

The IH2technology makes use of proprietary catalysts developed through the cooperative efforts of CRI's affiliates in their research facilities in Bangalore, India, and manufactured by CRI affiliates in the US, Belgium and Germany.

Chicago-based GTI is a non-profit body that was originally established by a consortium of gas companies. Its current mandate is to develop energy solutions, typically working with a third party. It has a staff of 250 and holds more than 1,200 patents.

GTI and CRI have commercial agreements in place for joint development and novel R&D focused on catalyst development, and an exclusive worldwide license granted to CRI as the sole licensor of IH2technology.

CRI's involvement with GTI began three years ago. Mike Demaline, Global Business Manager for Renewable Fuels in the Forestry, Pulp & Paper sector explains, "We got involved because GTI knew they needed catalysts to develop the technology. As we familiarized ourselves with their process, we knew it had the potential to transform the industry by providing transportation fuel range hydrocarbons direct from biomass. We supplied the initial catalysts that GTI used and we knew we could significantly enhance the process by further developing proprietary catalyst lines."

With an eye on both sustainability and the bottom line, CRI realized agreements between the two organizations relative to IH2technology made perfect sense.

How about seaweed?

IH2is a catalytic thermo-chemical process designed to produce fungible liquid transportation fuels and/or blend stocks from lignocellulosic and other forms of biomass. Wood was GTI's initial choice because it knew the material and already had a concept in mind. Perhaps more importantly an abundant, sustainable supply could be readily available at a good price. However, the IH2process has been shown effective at the conversion of a broad range of other biomass types including seaweed, aquatic plants, algae, bagasse, corn stover and even municipal solid waste. Future work will examine customer specific feedstocks including miscanthus, jatropha and residues from sweet sorghum.

The feedstocks are fungible, meaning that the molecular structures present are the same as those in fossil-based fuels such as gasoline, jet fuel or diesel. Demaline says that at first, he expects the renewable hydrocarbons will be blended with traditional fuels. Independent life cycles studies suggest that the carbon footprint should be at least 94% lower than traditional fossil hydrocarbons on a seed to wheel basis.

The development of alternative fuels is important to the US as the government encourages the use of non-fossil based fuels. However, the US consumes 13.5 million barrels per day of liquid transport fuel , making goals non-fossil based fuels challenging to meet.

This may be evidenced by standards which originally set goals of 36 billion gal/yr of renewable fuel, which have been amended more recently to 25.7 billion gal/yr

A paper co-authored by GTI and CRI personnel shows possible scenarios of the IH2process using various feedstocks. For example, it shows a 2,000-bone-dry-ton wood feed/day plant could use stumps, branches, sawdust, bark and even the possibility to blend in various mill sludges. Hardwood or softwood, it makes no difference.

Research shows the IH2process can produce up to 92 gallons of liquid fuel per ton of wood feedstock (on a dry, ash-free basis). This totals 184,000 gal/day. The gasoline:diesel ratio would be expected to be 70:30.

It is a low-waste producing process. Product oxygen is below detectable limits and the total acid number or TAN is less than 0.03. Demaline points out this is very low and that most refineries invoke special procedures when processing crude oil with a TAN of more than two. Traditional pyrolysis oils have a TAN in excess of 100.

Still, to put it into perspective, to meet the amended fuel blend requirements of the US would potentially mean 400 such "bio-refineries" would needed by 2020 .

Demaline stresses that CRI and GTI are poised to meet the relevant challenges in the deployment phase. It will not be easy, since in full production, a 2,000-ton/day plant in a day would produce the equivalent of 12 hours' production of a world-scale fossil fuel refinery.

Moving ahead, Demaline states "We can make a dent in these numbers. The market is big because of the mandate."

The pilot plant produces sufficient product to allow fuel qualification

"Game changing" technology

So how does it work? Demaline says the IH2process is "game changing". The process equipment is not new or novel nor does it require special materials to construct. It can be refinery or mill integrated although the refinery integration model may have better economics.

Lignocellulosic biomass contains oxygen and this must be removed for it to become a hydrocarbon; that's why the catalytic thermo-chemical process is used. Breaking the carbon-oxygen bonds and replacing them with carbon-hydrogen bonds (and forming water as a result) creates heat (i.e. it is exothermic) that, for example, can be used to make high pressure steam for a paper machine dryer.

The oxygen from the biomass is removed primarily as water. The water is then used together with light gases produced by the process as the input to create all the hydrogen the system needs together with CO2. The CO2is referred to as "green" CO2because it comes from a non-fossil source. Demaline says this CO2may be captured to create a product for enhanced oil recovery, food or chemical products.

The cellulose and lignin molecules are turned into gasoline, jet fuel and diesel molecules. To get to the end product, there are various stages. The first is feed conditioning where the raw material is sized
(2-4 mm is optimum), mixed and dried.

The first stage reactor is a bubbling fluidized bed (BFB) but unlike a traditional BFB boiler, no sand is used. "Instead, we use advanced proprietary catalysts," Demaline explains. The BFB is loaded with the catalyst, which acts as a heat transfer mechanism.

Inside the BFB, the biomass meets the catalyst in the presence of a low-pressure hydrogen atmosphere. Hydrogen is produced in a hydrogen manufacturing unit (HMU).

The reaction takes seconds in the pressurized reactor. By the end of the first stage, the material is in vapor form and the vapor includes hydrocarbon molecules of varying length as well as the water.

The first stage takes out the majority of the oxygen. The second stage takes out the rest as well as undesirable trace elements such as sulfur and nitrogen.

A cyclone collects char and ash (about 10-12%), the char having an energy content of 11,000-12,000 BTU/lb.

The process requires a fossil fuel source such as natural gas only at startup. It is used in three places: to heat the first stage reactor; to pre-heat the feed to the second stage reactor and as an initial feed gas in the HMU. The process is self-sufficient and self-sustaining after startup, no longer requiring the need for natural gas addition.