WV Coal Member Meeting 2024 1240x200 1 1

Coke Oven Gas to Synfuel

We have documented in some general detail the indirect processes, such as Fischer-Tropsch, for coal liquefaction.
 
In brief summary, a "syngas" is generated by the thermal decomposition of coal in a low-oxygen atmosphere, which is then passed over an Iron-group metal or zeolite catalyst that condenses the syngas into liquid hydrocarbons, which, like crude oil, can then be refined into ethanol, methanol, diesel, gasoline, and other useful liquids.
 
That's a gross over-simplification, of course, but captures the rough outline of the process.
 
We're certain you're at least generally familiar with "coke" - the high-carbon residue produced by the low-oxygen roasting of coal - which is used in traditional steel-making processes.   
 
Coke ovens in steel and coal country were once fairly common sights, especially visible at night, when they appeared as dull orange spots glowering on the dark hills.  
 
The purpose of "coking" was to drive off the volatile components, including impurities like sulfur, so that a more pure, less contaminating, carbon product was produced for refining iron ore and making steel.
 
The volatile gases, driven from the coal by the coking process - the "coke oven gas" - are flammable. They were at first vented to the atmosphere - "flared"; but, later refinements allowed for them to be captured and used, either as fuel for the coke ovens themselves or as supplemental fuel for the steel mill furnaces.  
 
The coking process does generates other products, and the following link, from which the table below it is extracted, can provide more detail; with additional comment following:
 
 
 
Stream Destination Typical quantities, based on 1 million tons per year coke
Coke Oven Gas Used as fuel gas at the coke oven battery and steel works 50 million std.cu.ft./day
Flushing Liquor Recirculated back to the coke oven battery Varies with plant design
Waste Water Discharged to treatment plant Varies with plant design
Tar Sold as product 29,000 gallons/day
Ammonia/Ammonium Sulfate Sold as product 12 tons/day (as ammonia)
Light Oil (if recovered) Sold as product 12,500 gallons/day
Sulfur/Sulfuric Acid (if gas is desulfurized) Sold as product Varies with coal properties and local requirements
 
 
Our focus is on the organic products of coking, but you can see that other useful by-products are also generated.
 
Next, we direct your attention to:
 
 
An excerpt:

"The 120 000 t/a methanol project based on coke oven gas designed by the Second Design Institute of Chemical Industry started production in Kingboard (Hebei) Coking Co., Ltd. on Sept. 5. The product reached the standard for AA-grade products in the United States. The capacity of this unit is 40 000 t/a higher than the first methanol unit based on coke oven gas in China complete in Qujing, Yunnan province in December 2004."

What all this adds up to is this:  

In both indirect and direct (i.e., WVU's West Virginia Process) technologies for converting coal into liquid hydrocarbons suitable for fuel and plastics manufacturing, the coal, and it's intermediate products, must be "hydrogenated". WVU, in their direct coal liquefaction technique, as we understand it, use the solvent tetralin as the hydrogen donor. 

Indirect CTL processes, such as Fischer-Tropsch and Bergius, use hydrogen derived from the coal itself, but there isn't enough to "go around". Much carbonaceous "slag" is generated, and a lot of the carbon is wasted. It has been suggested, perhaps in some places experimented with or reduced to practice, that the inclusion of biomass, or even pure hydrogen electrolyzed from water, could enable the necessary hydrogenation.

Herein, we have illustrated the possibility that an otherwise objectionable, hydrogen-rich by-product of coal use in the steel industry, coke oven flue gas, can be captured and recycled, as is, according to the above citation, apparently being done in China, into the process of converting coal into liquid hydrocarbon fuels.

We'll note also the co-production of  fertilizer (ammonia), as well as other materials from which potential fuels could be derived - tar and light oil - in the coke-making process.

So, the possibility exists, as might be being realized in China, given the steel-making companies publicly known to be involved in their massive CoalTL industrialization program, to site, in an efficient and environmentally-beneficial way, a coal-to-liquid conversion facility next to a steel mill with an integral coking plant, to utilize coke oven gas as a co-feed in the synthesis of liquid hydrocarbon fuels, such as methanol, from coal.

As we've said many times: Our use of coal doesn't generate pollutants, just valuable by-products.