Carbon Recycling for Converting Coke Oven Gas to Methanol for the Reduction of Carbon Dioxide at Steel Mills
Now as the future availability of crude oil is increasingly called into question, methanol is receiving renewed interest since it can be readily made from remote natural gas and from the world’s extensive coal and biomass resources. Much work was done previously around the world to identify the proper ways to design and modify vehicles to use methanol either as a neat fuel or in blends with gasoline. Extensive fleet tests were also conducted, with the majority occurring in the U.S. where methanol vehicles were sold commercially in the early 1990s. This report presents several significant findings from that work and experience.
Methanol has a long history of use in racing vehicles where it is valued both for its power producing properties and its safety aspects (methanol is harder to ignite, creates less radiant heat, and burns without producing black smoke). Methanol use in non-racing vehicles has been much less successful. There was significant interest in using methanol as a gasoline blending component for its octane value and emissions characteristics in the U.S. when lead was phased out of gasoline and more stringent emission standards were established. Several methanol/cosolvent blends were approved for use but the oxygenate methyl tertiary butyl ether (which used methanol in its manufacture) was preferred. During the 1980s and through much of the 1990s, most gasoline in Western Europe contained a small percent of methanol, usually 2-3%, along with a cosolvent alcohol. Gasolines used in European Union countries are allowed to have 3% methanol, but it is being challenged by ethanol (allowed up to 5% now with a proposal to go up to 10%) which is valued for its low greenhouse gases. Today, China is the leader in using methanol as a transportation fuel where between 3 and 5 million tons were used last year.
Using methanol as a gasoline blending component represents the most expeditious way to use large amounts of methanol as a transportation fuel. Methanol addition increases octane value and will cause decreases in hydrocarbon, toxic, and carbon monoxide emissions. Most modern fuel systems with feedback control should be able to accommodate low-level methanol blends (up to 10%) without difficulty, though exceptions are possible. Using low-level methanol blends does require good house-keeping practices in transport, storage, and dispensing, to assure that water addition is minimized to prevent phase separation. Adding methanol to gasoline increases vapor pressure which could lead to increases in evaporative emissions during warm weather. Addition of a cosolvent (typically higher alcohols) ameliorates both these issues and adjustment of the gasoline specifications can eliminate the increase in vapor pressure. Careful tailoring of the gasoline used to make methanol blends can maximize the benefits of methanol addition and increase gasoline refining efficiency.
In the early 1980s, there was considerable interest in using methanol as a fuel for both petroleum displacement and air quality reasons. To achieve the quickest displacement and largest impact on air quality, it was desired to use methanol neat or near-neat as a transportation fuel. In the U.S., fleet demonstrations of methanol vehicles were very successful given the vehicles’ low emissions, 20% increase in power, and 15% increase in energy efficiency. However, the decrease in vehicle range (the fuel tank could not be expanded sufficiently to counteract the decrease in methanol heating value) and the sparse number of methanol refueling facilities caused methanol vehicle drivers great anxiety. This directly led to the development of methanol flexible fuel vehicles (FFVs) which could use methanol or gasoline in the same tank through the use of an alcohol fuel.