Coal To Liquid (CTL)
Coal to liquid is not new, in world war II, germany and japan used this technology to produce replacement fuels. In 1944 germany produced 124 thousend barrels in day replacement fuels, also in apartheid in south Africa, CTL fuels produced for jets and other use.
The recent (2011-2014) high prices of oil and natural gas in world are leading to an increased interest in technologies such as coal gasification, which convert lower value hydrocarbon feed stocks into higher value end products. There are numerous CTL projects worldwide and Figure 1 provides a broad overview of the various CTL projects. Blue color in the figure denotes the CTL plants that are in current operation and green color denotes the CTL projects that are in design or under construction. Only in America, it is estimated by the year 2035, 500 thousand barrels per day of liquid fuel produced from coal.
Figure 1: production of liquid fuels from coal in different countries in 2011
CTL plant consists of gasifier unite, water gas shift unite, cleanup unite, fischer tropsch unite and waxcracking unit.
In the gasifier, pure oxygen and slurry coal entered to produce synthesis gas.
Then in water gas shift, steam added to synthesis gas to react with carbon monoxide and produce hydrogen and carbon dioxide. This unite designed to increase the H2/CO ratio that needed in fischer tropsch unite.
Cleanup unite used to remove H2S and ammonia.
Synthesis gas reacted in fischer tropsch reactor to hydrocarbon chains produced. The probability for such long chains is demanded to reactor temperature, catalyst and other reaction condition.
Produced wax in fischer tropsch reactor can be decomposed to naphtha and diesel if market requires.