Fuel From Coal/Biomass and Coal/Sewage Mixtures


We have posted several notes to you concerning the co-gasification potential of coal, biomass, and sewer sludge, with the goal of generating syngas, which can then, through several established, even well-known, catalytic processes be converted into liquid fuels and valuable raw materials for the chemical manufacturing industry.
 
Enclosed is yet more documentary evidence that our coal, and even our wastes, can be combined synergistically with biomass to provide both the needed raw materials with which to manufacture our liquid transportation fuels, and an inherent mechanism, the inclusion of biomass, which could, through established technologies, be intensively cultivated for the purpose of providing additional raw material for liquid fuel production, while at the same time recycling the Carbon emissions from combustion of that fuel.
 
The enclosed link will access another authoritative report on that subject. Some excerpts:
 
"Author(s):
C. Storm, H. Rudiger, H. Spliethoff, and K.R.G. Hein
Institut für Verfahrenstechnik und Dampfkesselwesen, (Institute for Process Engineering and Power Plant Technology) University of Stuttgart, Pfaffenwaldring 23, D-70569 Stuttgart, Germany
 
Biomass and sewage sludge are attracting increasing interest in power planttechnology as a source of carbon-dioxide-neutral fuels. A new way to reduce the consumption of fossil fuels could be the co-combustion or co-gasification of coal and biomass or coal and sewage sludge. In both cases, pyrolysis is the first step in the technical process. In order to obtain detailed informationabout the pyrolysis of coal/biomass and coal/sewage sludge mixtures as well as unblended fuels, the “Institute für Verfahrenstechnik und Dampfkesselwesen (IVD)” at the University of Stuttgart has carried out investigations using an electrically heated entrained flow reactor. The test runs provided information about fuel conversion efficiency, pyrolysis gas and tar yield, and composition of pyrolysis gas and tar. Besides gas and tar analysis investigations regarding the path of trace elements, like heavy metals, alkali, chlorine and nitrogen components, during the pyrolysis process varying different parameters have been carried out. The fuel nitrogen distribution between pyrolysis gas, tar, and char has been analyzed, as well as the ash composition, and, thus, the release of mineral components during pyrolysis."
 
This report actually concerns the co-generation of syngas which would then be, in the authors' concept, directly burned in a power plant to, cleanly, generate electricity. The technology for doing so is, again, well-understood, even established. Once the syngas is obtained, though, several options exist for it's use. It can be, as in this study, combusted directly for clean power generation; or, it can be further processed, via several well-known chemical pathways, such as Fischer-Tropsch conversion, into valuable chemicals for manufacturing, or into any of several liquid fuels: methanol, diesel, and even gasoline.

Plant Would Let Algae Turn Carbon Dioxide to Fuel


As we've detailed, CO2 can be directly recovered from the atmosphere, or coal plant flue gasses, and then chemically processed into useful hydrocarbons - up to and including gasoline.
 
But, we've also documented the use of algae, as cultivated in "bio-reactors" and "fed" with Carbon Dioxide, and other nutrients, from coal-fired power plants, to recycle emissions into useful substances.
 
There are many strains of algae, and they produce a variety of compounds. Herein is documented an effort undertaken by Dow Chemical and an algal science company, Algenol Biofuels, to produce ethanol by recycling Carbon Dioxide.
 
Some excerpts:
 
"Dow Chemical and Algenol Biofuels, a start-up company, are set to announce Monday that they will build a demonstration plant that, if successful, would use algae to turn carbon dioxide into ethanol as a vehicle fuel or an ingredient in plastics."     
 
(Note the "synergy" mentioned in the following excerpt.)                                                        

"The ethanol would be sold as fuel, the companies said, but Dow’s long-term interest is in using it as an ingredient for plastics, replacing natural gas. The process also produces oxygen, which could be used to burn coal in a power plant cleanly, said Paul Woods, chief executive of Algenol, which is based in Bonita Springs, Fla. The exhaust from such a plant would be mostly carbon dioxide, which could be reused to make more algae...."

Biomass to Synfuels

 
 
We submit this information in further support of our contention, our thesis, that coal and certain types of biomass can be converted into liquid fuels, at the same time, in the same, appropriately-designed and specified processing facility.
 
To belabor the point, and the word, combining coal and biomass is synergistic. Though not specified in this report, syngas yields of coal and biomass combined are higher than either pyrolyzed alone, as we've elsewhere documented. And, the biomass offsets the carbon released when the resulting liquid fuel is combusted.
 
The excerpt, from Iowa State University:
 
(Please note mention both of syngas, and our old Coal-to-Liquid friends, Fischer and Tropsch)
 
"Biomass to Liquids (BTL) processes are being designed based on the thermo-chemical platform for converting biomass to biofuels. In an indirect liquefaction process, synthesis gas (syn-gas, CO+H2) is first produced via gasification of solid biomass or liquid bio-oil produced by the fast pyrolysis of biomass. Syn-gas can be converted to synthetic gasoline, jet-fuel or diesel using Fischer-Tropsch synthesis of hydrocarbons or synthetic alcohols, such as ethanol, through different catalytic processes. These gas to liquids (GTL) technologies, previously  utilizing coal or low-cost, remote natural gas as feedstock for liquid fuels production can be adapted for the conversion of bio-mass to liquids (BTL)."6-

Coal and Sewer Sludge to Liquid

 

According to information accessed via the link, this article is adapted from a technical paper presented at the 1998 International Gas Turbine & Aeroengine Congress & Exhibition in Stockholm, Sweden.
 
We presume you to know by now the significance of the word "syngas" in the title.
 
Some excerpts:
 
"Commercial Viability

Rheinbraun concluded that co-gasification of sewage sludge or loaded coke with dried brown coal offered significant potential for disposing of these wastes without impairing plant efficiency and emissions. The commercial viability was demonstrated by an assessment study that included major aspects such as feed rate, total investment, and methanol price in order to establish the criteria for the use of sewage sludge in the high-temperature Winkler gasification process.

                                                                 - - -
 
A separate part of the program, coal-biomass environmental studies, undertaken by CRE Group and Imperial College of the United Kingdom, and TPS Termiska Processer AB and Kungl Tekniska Hogskolan of Sweden, concentrated on the use of laboratory-scale experimental techniques to study the influences of several fuels on gasification behavior. The studies found that when coal and biomass or wastes were co-gasified, the overall level of tars generated was lower than for coal alone; the concentration of hydrocarbons in the range of C1 to C7 was increased, and product gas yields increased and char levels decreased, with co-gasification chars being significantly more reactive. In addition, the heightened char reactivity resulted in increased conversion of NO and NH3 to N2 ..."
 
As we've documented from other sources, in separate dispatches, the addition of biomass,and, in this case, sewage sludge, to coal for gasification improved the yield of syngas (i.e., "gas", above), and the presumed subsequent productivity of liquid fuel.
 
Moreover, the reactive by-products of the combined coal/biomass/sewer sludge gasification reduced the emission of undesirable Nitrogen Oxide, converting it into harmless Nitrogen gas and an ammonia radical that would be useful for fertilizer co-production.

Combined Coal/Biomass Pyrolysis

 

As we've suggested to be possible and feasible, experiments are being performed on the co-pyrolysis of coal and biomass, combined, to generate the raw materials for liquid fuels.
 
The development in the case we cite herein is taking place in China, home of the rather extraordinary coal-to-liquids industrialization program we've reported, and where, as we've also reported, they are using agricultural development to consume excess Carbon Dioxide.
 
The excerpt, with comment about their choices of both biomass and coal following: 

" Li Zhang, Shaoping Xu, Wei Zhao and Shuqin Liu

State Key Laboratory of Fine Chemicals, Department of Chemical Engineering, Dalian University of Technology, 158 Zhongshan Road, PO Box 33, Dalian 116012, China 

Abstract

An experimental study on co-pyrolysis of biomass and coal was performed in a free fall reactor under atmospheric pressure with nitrogen as balance gas. The coal sample selected was Dayan lignite, while the biomass used was legume straw. The operation temperature was over a range of 500–700 °C, and the blending ratio of biomass in mixtures was varied between 0 and 100 wt.%. The results indicated that there exist synergetic effects in the co-pyrolysis of biomass and coal. Under the higher blending ratio conditions, the char yields are lower than the theoretical values calculated on pyrolysis of each individual fuel, and consequently the liquid yields are higher. Moreover, the experimental results showed that the compositions of the gaseous products from blended samples are not all in accordance with those of their parent fuels. The CO2 reactivities of the chars obtained from the co-pyrolysis under the higher blending ratio (around 70 wt.%) conditions are about twice as high as those of coal char alone, even higher than those of biomass alone."

First, "straw" would suggest the dried stems of grasses or grains, consisting we would suppose, in large part, of cellulose - which we've previously documented to be compatible with coal as a co-feed for a suitably-designed gasification/liquefaction facility.

Second, the coal they are using is lignite, which will be lower in organic content and higher in ash than West Virginia bituminous, but which will be comparable in some ways to carbonaceous wastes found in some, especially older, WV coal mine spoil accumulations.

Third, the use of combining coal with cellulose appears to be synergistic: The "liquid yields are higher", with lower residual "char".

Finally, the combination is synergistic in another way, as well: The straw, as it grows, consumes the Carbon Dioxide that evolves when the fuel is combusted.