|Home||Energy Physics||Nuclear Power||Electricity||Climate Change||Lighting Control||Contacts||Links|
SYNTHETIC FUEL OPTIONS:
Governments will soon have to face the reality that CO2 emissions from combustion of fossil fuels have severe environmental consequences. However, there is no viable substitute for high energy density liquid hydrocarbons for fueling jet aircraft. These high energy density liquid hydrocarbons will have to be synthesized from electrolytic hydrogen and bio-matter feedstocks.
Use of off-peak and constrained non-fossil fuel electricity generation for production of synthetic liquid fuels is critical to reduction of overall CO2 emissions to the atmosphere and to electricity system stability in the absence of fossil fuel electricity generation. This web page examines the production of synthetic liquid fuel without emitting CO2 to the atmosphere.
Reference: Biofuels Heat Hydrogen ORNL October 2022
Synthetic Liquid Fuel
A useful fuel needs to have a high chemical binding energy per unit of mass. In theory:
4 Li + O2 = 2 Li2O
lithium + oxygen = lithium oxide
is a good fuel. However, lithium is very expensive for utility scale energy storage.
For stationary industrial applications an affordable synthetic liquid fuel combination is:
Na + Cl = NaCl
sodium + chlorine = salt
However, this reaction is unsuitable for most marine applications because sodium reacts explosively with water and chlorine is a gas at room temperature-pressure and is highly toxic. For use in batteries this reaction is made safer by reacting the chlorine with nickel and the sodium with sulfur. The result is a sodium-sulphur nickel-chloride battery which is the subject of another web page on this web site. A disadvantage of these batteries is that they must be kept hot all the time, which limits their applications.
Another possible fuel reaction is:
4 NH3 + 3 O2 = 2 N2 + 6 H2O
ammonia + oxygen = nitrogen + water
On paper this reaction appears attractive. However, the danger of ammonia should not be under estimated. Ammonia is a gas at room temperature-pressure. One breath of it causes life long disability. Ammonia might eventually be used as a marine fuel where the surrounding water can be used to capture any unreacted ammonia in the exhaust.
An advantage of NH3 is that it is much more suitable for seasonal energy storage than compressed H2 gas. According to: reference the NH3 can be electolyzed to give:
2NH3 + electricity = N2 + 3 H2
with only about (1 / 3) the amount of electricity as is needed to electrolytically split water.
The existing US ammonia production and transportation capacity is summarized in the following Ammonia Market Slide Set.
A good summary of ammonia as a fuel is contained in a chapter in Robert Hargraves book titled Electrifying the World
John Rudesill comments as follows:
Converting many large fossil fuel consuming transportation vehicles to ammonia fuel will inevitably increase releases of N2O which is not only a potent GHG, but is also a destroyer of ozone. The fix is probably to insist that any use of ammonia as fuel have at least a partial catalytic decomposer of the ammonia to release free H2 that will suppress NOx formation during ammonia combustion.
Files relevant to use of anhydrous ammonia as a combustable fuel are:
AMMONIA APPLICATION PAPERS
Anhydrous Ammonia Bulk Storage Regulations
Science and Technology of Ammonia Combustion
Storage and Handling of Anhydrous Ammonia
Industrial Ammonia Production Emits More CO2 Than Any Other Chemical Making Reaction
N2O is fairly stable and is more difficult to remove from combustion than NO and NO2 among other nitrogen oxide species. Complete decomposition of ammonia should largely prevent formation of NOx during combustion of the hydrogen. A small residual amount of ammonia may react with any NOx formed and reduce output to low amounts.
Another possible synthetic fuel reaction is:
2 CH3OH + 3 O2 = 2 CO2 + 4 H2O
methanol + oxygen = carbon dioxide + water
From a practical handling perspective methanol is still toxic but it is much safer and more convenient than ammonia or chlorine. Methanol is a liquid at room temperature-pressure. Biological systems have developed a natural tolerance to limited amounts of methanol. The disadvantage of methanol is that producing it without fossil carbon requires a large source of bio-carbon. Methanol has been proven as a marine fuel. A disadvantage of methanol is that its energy density is only about half that of oil. Hence methanol is not a good aircraft fuel.
An advantage of methanol is that it is easily produced on farms. Making it on farms conserves the soil phospherous. From farms it may be shipped to refineries via plastic pipelines. The farms can make hydrogen using interruptible electricity. The waste heat from the electrolysis process can be used to assist in heating the wood chips.
C6H12O6 + 6 H2 + heat = 3 CH3OH + 3 CO + 6 H2 = 6 CH3OH
Note that in reality the biomatter contains water so the output is dilute CH3OH. The water should be removed first by wood chip drying at farms and then by separation at a nuclear powered refinery where the heat is cheap.
CH3OH and C2H5OH AS ENGINE FUELS:
CH3OH has long been used to power model aeroplanes and racing cars. It works in 2 stroke glow plug engines. John Rudesill says:
A large fraction of the energy required to produce and dehydrate methanol and ethanol goes into distillation and dehydration. If a bioethanol plant only goes to 50% that energy term drops dramatically. Typical internal combustion engines waste more than enough heat to distill the 50% CH3OH product to >90% CH3OH which can be burned in a flex fuel engine. Brazil has long since abandoned 100% ethanol for fuel blending and they use the azeotrope that is ~93% EtOH. They have flex fuel motorcycles and cars that can go from pure EtOH azeotrope to pure hydrocarbon gasoline. Interestingly, the Honda flex fuel unit for Brazil is unknown to US Honda dealers. Building an on board still on a moving vehicle seems a bit crazy, but is trivial for major stationary or marine engines optimized for pure azeotrope ethanol. Here is a slide deck on Utilization of Waste Engine Heat to Drive Ethanol/Water Distillation which illustrates the process.
ENERGY DENSE LIQUID FUELS:
A more energy dense aircraft fuel can be obtained by dehydration of methanol followed by hydrogenation.
2 CH3OH = C2H5OH + H2O
methanol = ethanol + water and
2 C2H5OH = C4H9OH + H2O
ethanol = isobutanol + water
C4H9OH + H2 = C4H10 + H2O
isobutanol + hydrogen = butane + water
Hence with addition of both hydrogen and energy methanol can be refined to produce butane or higher molecular weight hydrocarbons which can be used as aircraft fuel. In the various process steps the oxygen content of the feedstock is extracted by repeated dehydration.
LIQUID HYDROCARBON FUELS:
Liquid hydrocarbon fuels are integral to modern society. During the year 2004 residents of the Province of Ontario consumed about 15.7 billion litres of liquid hydrocarbon fuels. Energy dense liquid hydrocarbon fuels are used because they are convenient and because in combination with oxygen from the air their stored thermal energy is very high (~ 37.2 MJ / lit, ~ 44.8 MJ / kg). The high energy storage capacity of liquid hydrocarbon fuels allows most automobiles to travel about 600 km between fuel tank refills and allows large aircraft operational ranges of up to 15,000 km.
In 2010 over 90% of the liquid hydrocarbon fuel used in Ontario came from fossil feedstock. If mankind is to prevent atmospheric thermal runaway use of fossil carbon as a source of prime energy must be halted. However, there are numerous applications, such as fuelling: aircraft, surface vehicles going to remote locations, portable power tools (eg. tractors, chain saws), electricity generators at remote locations and heating at remote locations, where there is no practical substitute for energy dense liquid hydrocarbon fuels. Liquid hydrocarbon fuels also lend themselves for use in automatic appliances such as furnaces and water heaters at locations where no piped natural gas or district heat is available. Hence society must address large scale synthesis of liquid hydrocarbon fuels using non-fossil energy, biomass carbohydrate and water. Synthetic liquid fuels are not prime energy sources because production of a synthetic liquid fuel requires an amount of prime energy in excess of the chemical potential energy contained in the synthetic liquid fuel.
A significant constraint on use of ethanol as a liquid vehicle fuel in Canada is Low Temperature Phase Separation
LIQUID FUEL SYNTHESIS:
Biodiesel: A Review
In Cuba - Biodiesel from Jatropha.
Synthesis of Gasoline and Diesel From Forest Residue
Integrated Hydropyrolysis and Hydroconversion for Jet Fuel Production
Integrated Hydropyrolysis and Hydroconversion for Jet Fuel Production
In India Shell is testing a biomatter to synthetic liquid fuel production process.
In China a superior synthetic liquid jet fuel is being made from plant cellulose.
SLIDE SET BY CHARLES W FORSBERG:
Slides relating to a presentation by Charles W Forsberg titled: "Replacing liquid fuels with liquid Biofuels from Large Scale Nuclear Biorefineries" are available for download in pdf format from:
Nuclear hydrogen heat biorefinery Slide Set
Replacing Liquid Fossil Fuels and Hydrocarbon Chemical Feedstocks With Liquid Biofuels Using Nuclear Heat and Hydrogen
Nuclear Energy Drop-In Replacements for Gas Turbines, Natural Gas and Fossil Liquid Fuels
Practical issues constraining this biofuel production process are the costs of harvesting biomatter, the costs of on-site preprocessing of biomatter to reduce mass and recycle soil elements, transportation costs and the total annual tonnage of biomatter available for production of liquid fuels.
US Synfuel Scenarios
COMMENT ON LIQUID FUEL SYNTHESIS By John Rudesill:
The clever achievement I think they are utilizing starts in the initial pyrolysis step. They control the hydrolysis of the complex cellulose and hemicellulose to yield mono and disaccharides which can be hydrogenated over their special catalyst(s) to saturated long chain hydrocarbons with a cyclo pentane or hexane end groups. The lignin aromatic groups are saturated as well.
I will see if I can find out if my understanding is accurate. They brag about a large number of patents which likely are GTI IP at the beginning. The catalysts may be optimized by Shell CRI division. Hydrogenation processes are usually limited to <700 F due to rapidly increasing coking rates above that level. This is below 400 C so your FNR heat source fits. What is missing from their promotional material is how they simultaneously saturate the mono and disaccharides and grow the chain length. This will require a sophisticated at least multifunctional catalyst.
In hydrocracking, the normal result of olefinic products is overcome with the presence of H2. I don't think think GTI/Shell process involves cracking, but rather some sort of chain growth. It is not clear if they are using a modified Fischer-Tropsch chemistry. They well could be using H2 from water electrolysis powered by renewable electricity of cheap FNR juice.
Jet fuel specifications are formulated from several requirements. Energy density is important for its obvious relationship to efficiency. Pour point is important to maintain fluidity at the very low temperatures at cruising altitudes. Increasing energy density tends to raise the pour point. There are other issues with smoke, soot, and CO emissions that tend to increase with increasing aromaticity which favors less dense saturated molecules.
We thus have trades offs to consider. These engines can run on a wide range of fuels with some caveats in performance. Military aero turbines have been studied for a wide range of fuel molecules. The turbine manufacturers only honor their warranties if the engines are operated on specified fuels. It doesn't mean they won't operate on fuels outside of those boundaries. It is some sort of legal thing to satisfy FAA certifications.
FOSSIL FUEL DISPLACEMENT:
In urban applications energy derived from liquid fossil fuels can usually be displaced by electricity obtained from nuclear and renewable energy. However, in long distance transportation applications and in portable and remote applications the appropriate displacement measure is to replace liquid fossil fuels with synthetic liquid hydrocarbon fuels. Synthetic liquid hydrocarbon fuel production should use non-fossil fuel energy to convert biomass and water into liquid hydrocarbon fuels such as methanol, propane and gasoline without net emission of greenhouse gases.
Present biofuel production processes based on ethanol sacrifice two thirds of the carbon contained in the biomass feedstock to convert carbohydrates into alcohols or light oils. This sacrifice is made because:
1) At present biomass is still relatively inexpensive, in part due to government agricultural subsidies;
2) There is insufficient non-fossil fuel electricity generation;
3) Where there is sufficient non-fossil fuel electricity generation the energy is usually constrained rather than being provided on an interruptible basis to synthetic liquid fuel producers.
In the future the limited supply of biocarbon will likely make full utilization of the available biocarbon much more important. Hence the conversion of carbohydrates into liquid fuel should use electrolysis of water to provide sufficient hydrogen for full conversion of carbohydrate into an energy dense liquid fuel.
As synthetic liquid fuel usage increases the demand for biomass carbohydrate for liquid fuel production will increasingly impinge on the supply of carbohydrate for food. To minimize the impact of synthetic liquid fuel production on food production it is essential to incorporate 100% of the available biocarbon in crop and forest waste into the synthetic liquid fuel. The synthetic fuel production process contemplated herein is almost 100% efficient and is almost independent of the biomass type because the process does not rely on biochemical reactions.
The requirement for maximizing utilization of available waste biocarbon effectively rules out large scale use of bio-ethanol and bio-butanol processes, which emit large quantities of CO2. The requirement for maximizing use of available biocarbon also rules out simple destructive distillation of carbohydrate. The only fully biocarbon conserving process that produces liquid fuels is distillation of biomass followed by hydrogenation of carbon monoxide. Both steps form methanol. After methanol production the biomass feedstock residue is removed and recycled as a fertilizer to reuse the phosphorous, potassium and other critical plant growth enabling trace elements remaining in the biomass residue.
PRACTICAL SYNTHETIC FUEL:
In tropical countries such as Brazil fuel ethanol can be produced using only sunlight as a source of prime energy. However in Canada the growing season and the average sunlight level are not sufficient for economic large scale fuel ethanol production. Fuel alcohol production in Canada requires additional prime energy from other sources.
In Canada the synthetic liquid fuel that lends itself to on-farm production is methanol (CH3OH). Biocarbon efficient production of methanol requires large amounts of electricity for electrolysis of water to produce hydrogen. With sufficient hydrogen total methanol production is limited only by the amount of carbon contained in the biomass feedstock.
Methanol can be easily transported to a refinery where it can be hydrogenated and dehydrated to form energy dense liquid fuels such as propane, butane and synthetic gasoline.
In the absence of fossil fuels methanol will likely become the major primary liquid fuel. Methanol has been used as a fuel in high performance racing car engines for many years. However, methanol has a relatively low boiling point (64.7 degrees C) and is water soluble. In a refinery methanol can be dehyrated and hydrogenated to form propane, butane or gasoline which, as compared to methanol are less corrosive and have a higher energy density. Hence, for aircraft use methanol production can be followed by refinery conversion of methanol into a higher energy density liquid fuel.
Pure methanol is a good marine fuel. Pure methanol has the advantage that it completely dissolves in water. Hence if it is spilled into the ocean it rapidly dissipates and then is broken down by biological action. Hence methanol can be used in place of water betwewen the inner and outer hulls of ships.
In diesel engines the fuel is typically 5% oil and 95% methanol. At the top of the compression stroke the oil aids in igniting the methanol. The oil also assists in sealing the fuel injection valves.
From a capital perspective methanol is much easier to handle than is Liquified Natural Gas (LNG). Methanol is a liquid at room temperature and is available from storage at nearly every major port.
Methanol tanks use a noncombustable cover gas, typically nitrogen, over the methanol to prevent formation of an explosive air-vapor mixture.
METHANOL COMBUSTION AND CORROSION:
When methanol burns the flame is invisible. A methanol fire is extinguished with water. Methanol transport pipes usually have double walls to minimize handling risks. The inside surfaces of methanol tanks are painted to resist corrosion.
Current world wide methanol production is about 70 X 10^6 tonnes / annum. Most of that production is presently derived from natural gas.
Methanol production from biomass involves anaerobic heating of dry biomass, condensation of the resulting methanol vapor, pump extraction of the remaining carbon monoxide gas, high pressure hydrogenation of the carbon monoxide gas and condensation of the resulting methanol.
Economic bio-methanol production requires an enlightened electricity rate regulator that makes available to methanol producers otherwise constrained non-fossil electricity. At this time the Ontario government, the Independent Electricity System Operator (IESO) and the Ontario Energy Board are not so enlightened. Methanol production, which can be remotely interrupted by the IESO at any time, can potentially absorb all of the Ontario non-fossil constrained and reserve electricity generation caspacity. Until this electricity rate situation is resolved bio-methanol production and hence liquid fossil fuel replacement in Ontario will likely remain uneconomic.
BIOMASS FEEDSTOCK AND RESIDUE TRANSPORTATION:
One of the cost components of methanol production is transportation of biomass feed stock from the location where it is grown to the location where it undergoes the first stages of conversion into a synthetic liquid fuel. In some places the infrastructure originally built to service the pulp and paper industry can be used.
Sustainable large scale methanol production from biomass also requires ongoing replenishment of soil phosphorus and potassium. The required phosphorus and potassium is embedded in the waste product residue from the first stage of the methanol production process. This residue must be physically transported from the synthetic fuel production facility back to the biomass source and injected back into the soil to sustain large scale biomass production. Hence the first stage of the synthetic fuel production process needs to be physically close to the location where the biomass is grown.
COMPANION CARBOHYDRATE PRODUCTS:
Another major factor affecting the price of synthetic liquid fuel feed stock is demand for higher value carbohydrate products. For example, assume that the cost of logs delivered to a saw mill is $100 / tonne. Assume that the saw mill converts about 50% of the log weight into lumber. The other 50% of the log weight becomes chips and sawdust. If the saw mill can sell the lumber at $200 / tonne, then it can operate with a 30% gross profit margin if it can sell the chips and sawdust as synthetic fuel feedstock at $60 / tonne. However, if there is little demand for lumber, as prevailed in North America in 2009 - 2012, the only way the sawmill could operate with the same gross margin is to sell chips and sawdust at $130 / tonne. However, that price is too high for production of synthetic liquid fuels in competition with fossil fuels that are not subject to a fossil carbon tax.
A similar argument applies to biomass feed stock from agricultural waste. The biomass feed stock is only available at a competitive price if there is a market for the higher value agricultural product that generates the agricultural waste. This issue makes synthetic fuel production investments quite speculative because there is uncertainty as to future availability of specific biomass feed stock types at competitive prices. This risk can be eliminated by designing the synthetic fuel production process so that it can operate with many different types of biomass feed stock.
In order to make synthetic liquid fuel production economic bulk off-peak electricity is required at the locations where the synthetic liquid fuel synthesis takes place. These locations should be in close proximity to major farms and/or forest plantations. In short, every farm and forest plantation needs a three phase electricity service.
Nitrogen in a water soluble compound is essential for promoting growth of biomass. Nitrogen in the soil can be replaced via crop rotation with a nitrogen fixing plant type or via an ammonia or nitrate type fertilizer.
Sustainable large scale synthetic fuel production requires ongoing replenishment of soil nitrogen via fertilization or via crop rotation. Production of the nitrogen fertilizer requires production of ammonia. Production of ammonia requires energy, heat and hydrogen. Energy can come from wind, hydro-electric power, solar power or a nuclear reactor. Heat at the required temperature can come from electricity or from a liquid sodium cooled nuclear reactor. Hydrogen can come from electrolysis of water.
SUNLIGHT AND FRESH WATER:
Large scale biomass production is limited by simultaneous availability of both sunlight and fresh water. Lack of either prevents natural formation of biomass carbohydrate.
Growing plants use sunlight to combine water (H2O) and carbon dioxide (CO2) to form a class of chemicals known as carbohydrates. Common carbohydrates are isomers of C6H12O6 (starch and six carbon sugars), isomers of C5H10O5 (five carbon sugars) and cellulose (C6H10O5)n (long chain molecules). These materials have the net formation reactions:
6 CO2 + 6 H2O + sunlight = C6H12O6 (solid) + 6 O2 (gas)
5 CO2 + 5 H2O + sunlight = C5H10O5 (solid) + 5 O2 (gas)
n (6 CO2 + 5 H2O) + sunlight = (C6H10O5)n (solid) + n (6 O2) (gas)
Also present in biomass at 25% to 33% by weight is a complex phosphorus containing organic polymer known as lignin. Lignin forms plant cell walls which guide water flow, provide structural strength and protect the cellulose from microbial attack. Dry biomass contains significant amounts of nitrogen, phosphorus, potasium and trace elements that are chemically bound in the lignin. Plants take up these elements via water soluble chemical compounds contained in the soil. Agricultural biofuel production is sustainable only if there is a mechanism for recycling biomass residue to return these elements to the soil in water soluble form.
After harvesting, biomass must be cut, chopped or ground into small pieces to expose enough surface area to provide a satisfactory synthetic fuel production rate. The biomass needs to be dried. Dry biomass is a porous low energy density solid which is not a suitable fuel for vehicles and which is a difficult fuel to safely manage for automatic heating appliances such as furnaces. Dry biomass is bulky and is expensive to handle and transport.
To minimize biomass feedstock transportation costs the first stage of synthetic fuel production process should be located close to where the biomass feedstock is grown. The only suitable source of hydrogen that does not involve fossil fuel is electrolysis of water. This electrolysis requires a large input of inexpensive interruptible electricity. Electricity that is suitable for this application is electricity that is otherwise not generated due to constraint of nuclear or renewable generation or that is exported at an extremely low price. This electricity should be supplied to parties in Ontario under the terms of an Interruptible Electricity Service.
METHANOL PRODUCTION FROM BIOMASS:
Methanol (CH3OH) has long been used as a major chemical feedstock and as a fuel for portable cooking appliances and high performance automotive engines. In production of methanol for energy storage carbohydrate (C6H12O6) from biomass and hydrogen (H2) from electrolysis of water are chemically combined via a multi-step process in accordance with the chemical equations:
H2O + electricity => H2 (gas) + O2 (gas) + heat - electrolysis process
C6H12O6 + H2O (liquid) + mild heat => C6H12O6 + H2O (vapor) - biomass drying process
C6H12O6 + heat => 3 CH3OH + 3 CO - carbohydrate distillation process
3 CO + 6 H2 => 3 CH3OH - reforming process
The heat released by the first process step is used to drive the second and third processs steps. The hydrogen released by the second process step is used in the fourth process step. At present natural gas prices this methanol production methodology only makes economic sense with very low cost electricity.
In the presence of an appropriate catalyst the fourth step of this chemical reaction proceeds at a temperature of 250 degrees C and a pressure of 50 to 100 bar.
This method of methanol production does not liberate CO2 and uses available biomass about three times more efficiently than does bio-ethanol production. The main process issues are safety related relating to the use of high pressure high temperature hydrogen.
With minor burner head changes and adequate combustion exhaust venting methanol can replace other liquid fuels in heating appliances. Agricultural and forest product producers could potentially use methanol to reduce their consumption of liquid fossil fuels and to supplement their income. Unlike ethanol, methanol is not potable and hence avoids numerous regulatory issues related to illicit use.
Methanol is easily stored and transported in corrosion resistant containers. Methanol can be sold to a refinery as a feedstock for producing other hydrocarbons. A major advantage of methanol for energy storage is that at low concentrations its health effects are minimal. Existing life forms on Earth have evolved to tolerate low concentrations of methanol because methanol naturally occurs in the atmosphere and the environment.
The key to economic methanol production is an interruptible electricity rate for hydrogen production via electrolysis of water. This IES rate must make economic sense for participating agricultural and forest product producers. Methanol production is a potential IES load that is available year round and that has the potential to absorb all the available IES energy.
The details of liquid hydrocarbon synthesis from biomass are quite complex. However, from an energy perspective the overall thermal-chemical reactions can be simplified to ten steps:
Step #1 - Electrolysis of Water:
(water) + (electricity) = (hydrogen gas) + (oxygen gas) + (heat)
6 H2O + 6 (electricity) = 6 H2 + 3 O2 + (heat)
Step #1 is done at a high temperature/pressure with conductivity control to minimize the electrical energy requirement. The heat output from Step #1 is also an input to Step #2. The hydrogen gas output from Step #1 is an input to Step #4B.
Step #2 - Air Drying of Biomass:
(damp harvested biomass) + (heat) = (dry carbohydrate) + (water vapor)
C6H12O6 + liquid H2O + (heat) = C6H12O6 + H2O vapor
Step #2 is done in the temperature range 20 C to 80 degrees C and at atmospheric pressure to extract as much of the water vapor as possible from the biomass.
Step #3 - Further Drying of Biomass:
The biomass is loaded into an airtight low pressure reaction chamber and is gradually heated up to about 120 degrees C. The released water vapor is piped to heat exchangers used for Step #2 before being vented to the atmosphere.
The steam escape splits the biomass which increases the exposed biomass surface area. The required heat is obtained from Step #1 and Step #4B. The liquid water evaporated in Step #2 is typically 10% to 25% of the initial biomass by weight. The dry C6H12O6 output from Step #2 is an input to Step #3.
When the temperature reaches 120 degrees C extract air and water vapor from the low pressure reaction chamber containing the biomass using a mechanical vacuum pump.
Step #4A - Distillation of Carbohydrate:
(plant carbohydrate) + (heat) = (methanol) + (carbon monoxide)
C6H12O6 + heat = 3 CH3OH + 3 CO
This step is done at a low pressure. Solid residue remains in the reaction chamber. CH3OH is trapped in an external condenser. The CO flows onwards and is pumped into a high pressure high temperature reaction chamber to perform step #4B. Periodically the solid residue is extracted from the low pressure reaction chamber for use as a fertilizer.
Step #4B - Hydrogenation of Carbon Monoxide:
(hydrogen gas) + (carbon monoxide) = (methanol)
3 CO + 6 H2 = 3 CH3OH
This reaction takes place at a high temperature and pressure. After the reaction has run the CH3OH gas must be piped to a condenser where the pressure will drop. The remaining unreacted CO and H2 gases must be recycled.
The net Step #4 reaction is:
6 H2 + C6H12O6 = 6 CH3OH vapor
= 6 CH3OH liquid + latent heat
Step #4B is done at about 50 - 100 bar and at about 250 degrees C over a copper, zinc oxide and alumina catalyst to realize the desired reaction product. There should be a slight surplus of hydrogen to drive the reaction to completion.
Step #5 - Condensation of methanol vapor
The methanol vapor output from Step #4 is condensed to become liquid methanol. Depending on the efficiency of water extraction at Step #2 amd Step #3 it may be necessary to execute another stage of water extraction. The CH3OH then goes into storage for direct use or can be used as an input to Step #8. The latent heat output from Step #5 is used to assist with Step #2. Note that Step #4B once running is a net exothermic chemical reaction.
Note that the condensation of Step #5 takes place in a cool condenser that is external to the reaction chamber of Step #4 so that the reaction chamber and its contents remain hot.
Step #6 - Hydrogen Extraction:
The remaining hydrogen is pumped from the Step #5 condenser to the hydrogen storage tank.
Step #7 - Recycling of Phosphorous and Potassium:
After completion of Step #4A there is remaining solid biomass residue containing phosphorous and potassium in the low pressure reaction chamber. Air is admitted to the Step #4A reaction chamber and the solid biomass residue is removed and is transported back to the biomass source location to be returned to the ground as fertilizer.
Step #8 - Transportation of Methanol:
After completion of Step #5 the liquid methanol is stored for use on the farm where it is produced or is transported to a central refinery via tanker truck/railway tanker/lake tanker/pipeline. All the tanks and piping containing methanol must be suitably plated or lined to prevent corrosion by methanol. There cannot be any aluminum components in the methanol transportation circuit.
Step #9 - Dehydration and Reforming of Methanol In A Refinery:
(methanol) + (heat) + (catalyst) + (anhydrous chemicals) = (propane, gasoline) + (captured water) + (latent heat)
Step #9 is done in a central refinery at a high temperature (600 C), high pressure and with appropriate catalysts and anhydrous chemicals to realize the desired ratios of reaction products. Step #9 also requires input energy to vaporize the methanol and then raise the methanol vapor to about 600 C. The reaction products of Step #9 are condensed and density separated. The heat output from Step #9 obtained by condensation of the reaction products is fed back as an input to Step #9. One way of executing Step #9 is to use electrolytic hydrogen as the anhydrous chemical.eg:
6 [CH3OH] + 2 H2 = 2 C3H8 + 6 H2O
Step #10 - Water Purification:
The captured water from Step #9 will contain small amounts of toxic hydrocarbons. These toxic hydrocarbons must be carefully removed before the captured water is discharged to the environment. This step requires repeated fluid processing under conditions that provide a very high separation factor.
The biomass input to Step #2 is a process input. The propane or gasoline output from Step #9 is a net process output. The oxygen gas output from Step #1 is a byproduct that can be sold or vented to the atmosphere.
The above chemical equations allow estimation of the energy and feedstock inputs required to make methanol without net emission of CO2 to the atmosphere. The advantages of propane and gasoline over methanol are higher energy density and less corrosion.
An advantage of methanol is that it can be produced on a farm using relatively unsophisticated equipment. The main issues in on farm methanol production are carbon monoxide, hydrogen and pressure vessel safety. It is essential that the reaction chambers and piping be well sealed against CO and H2 leaks. It is essential that no hydrogen leaks backward into the low pressure reaction chamber.
Similarly, it is essential that air be fully removed from the high pressure reaction chamber before any hydrogen is admitted. Similarly, it is essential that gaseous hydrogen be fully removed from the high pressure reaction chamber before any air is admitted. There must be instrumentation to monitor the H2, CO and CH3OH partial pressures.
ON-FARM METHANOL PRODUCTION EQUIPMENT:
The hydrogen is generated in an electrolytic cell that operates at a pressure of about 10 bar and at close to the boiling point of water. The hydrogen bubbles up into a hydrogen storage tank that also operates at about 10 bar. The temperature and pressure in the electrolytic cell are maintained by thermostat/pressure sensor controlled circulation of the water through external radiators. To maintain liquid balance in the electrolytic cell the oxygen discharge valve is regulated to keep the liquid level on the oxygen side equal to the liquid level on the hydrogen side. A makeup water pump is used to maintain the water level in the electrolytic cell. A high pressure limit shuts off the electricity if the hydrogen pressure becomes too high. The storage tank hydrogen discharge valve is normally closed and opens only when a hydrogen transfer to or from the reaction chamber is required.
The biomass should be pre-dried in a storage chamber that is heated by process waste heat.
The reaction chambers should be thermally insulated to minimize the loss of process generated heat.
For on-farm bio-methanol production the practical Step #4A reaction chamber material is commercially available steel pipe in the size range 24 inch to 48 inch diameter. The maximum safe Step #4A reaction chamber operating temperature is limited by the properties of available elastomeric gaskets, which have maximum operating temperatures in the range 260 C to 320 C.
The maximum safe Step #4B working pressure is typically about 100 bar. The seals must be rated for use with hot methanol. The interior of the reaction chamber should be plated to resist corrosion by hot methanol.
The most labour intensive part of the methanol production process is repeated: removing the low pressure reaction chamber end cap, removing biomass residue, loading new biomass and resealing of the low pressure reaction chamber end cap. The end cap is heavy but can be supported by a chain hoist running on an I beam track. The low pressure reaction chamber should be mounted like a teeter-totter to facilitate liquid draining, biomass residue dumping and biomass loading. A vacuum pump removes air from the low pressure reaction chamber before heating commences.
For safety the low pressure reaction chamber operates close to atmospheric pressure. The high pressure apparatus should be subject to a periodic hydraulic pressure test to at least 1.5 times its maximum working pressure. The assembly and its safety controls should be TSSA approved.
The amount of methanol produced per reaction chamber load is limited by the amount of dry biomass that can be loaded into the low pressure reaction chamber. The seasons when this methanol production apparatus can effectively be used are the seasons when interruptible off-peak electricity is available for low cost electrolytic hydrogen production. For maximum overall throughput there should be a hydrogen storage tank larger in volume than the Step #4A reaction chamber volume and there should be an external vapor condenser with a magnetically coupled pump for hydrogen return from the Step #5 vapor condenser to the hydrogen storage tank.
At the end of each methanol production cycle the hydrogen remaining in the high pressure reaction chamber flows into the external CH3OH vapor condenser and then is pumped back into the hydrogen storage tank. From a safety perspective it is of paramount importance that all the hydrogen be removed from the high pressure reaction chamber and the external vapor condenser before any air is admitted. In principle air can find its way into the high pressure reaction chamber via the low pressure reaction chamber. To prevent this happening the low pressure reaction chamber is operated at slightly above one atmosphere so that air does leak into the low pressure reaction chamber via an imperfect gasket seal on the loading door.
The material data is as follows:
Name = hydrogen
Enthalpy of combustion = 141.86 MJ / kg, Atomic Weight = 1.008, Molecular Weight = 2.016
Atomic Weight = 12.011
Name = oxygen
Atomic Weight = 15.9999, Molecular Weight = 31.9998
Name = water
Enthalpy of formation = -285.83 kJ / mole, MP = 0 C, BP = 100 C,
Molecular Weight = 2(1.008) + 15.9999 = 18.0159
Name = carbohydrate
Enthalpy of formation = -1271 kJ / mole, Enthalpy of combustion = -2805 kJ / mole
Name = methanol
Enthalpy of combustion = 19.7 MJ / kg, MP = -97 C. BP = 64.7 C
Industrial electrolysis processes are not 100% efficient. Typical efficiencies are in the range of 56% to 73%. According to Hydrogenics the practically relaizable electrolytic hydrogen production rate is in the range 17.17 gm / kWh to 18.22 gm / kWh. The cost of industrial off-peak electricity in Ontario is presently about $.055 / kWh. Hence the marginal cost of producing electrolytic hydrogen with off-peak or otherwise constrained non-fossil electricity is in the range:
$0.055 / kWh X 1 kWh / (.01822 kg H2) = $3.01866 / (kg H2)
$0.055 / kWh X 1 kWh / (.01717 kg H2) = $3.20326 / (kg H2)
A key issue is the presence of another on-peak load which takes up the peak demand charge. Methanol production is not economically viable with on-peak electricity.
The combustion enthalpy of hydrogen is: 141.86 MJ / kg. Based on Hydrogenics data the electrical energy required to electrolyze hydrogen is in the range:
(1 kWh / 18.22 gm) X (1000 Wh / kWh) X 3600 s / h X 1000 gm / kg
= 197.585 MJ / kg
(1 kWh / 17.17 gm) X (1000 Wh / kWh) X 3600 s / h X 1000 gm / kg
= 209.668 MJ / kg
Thus the efficiency of the Hydrogenics equipment is in the range:
141.86 / 209.668 = 0.6766
141.86 / 197.585 = 0.7180
THERMAL ENERGY CONTENT OF CH3OH:
The thermal energy content of CH3OH is 19.7 MJ / kg.
Note that part of the fuel thermal energy content of synthetic methanol is provided by the electricity via added hydrogen and part is provided by the carbohydrate feedstock.
Recall that the net methanol synthesis reaction is:
C6H12O6 + 6 H2 = 6 CH3OH The atomic weights of hydrogen (1.008), carbon (12.011) and oxygen (15.999) in the above synthesis equations show that the molecular weight of methanol is given by:
[(12.011) + 4(1.008) + (15.999)] = 32.042
However, as biomass naturally grows only about 70% of its mass is usable carbohydrate. The balance is lignin that in may be unusable for supplying biocarbon to the synthesis reaction. Hence the amount of dry biomass required to make 1 kg of methanol is:
(100 / 70) X 937.08 = 1338.69 gm dry biomass
There are substantial costs involved in growing biomass, harvesting it, debarking it, and in lignin removal. The remaining material, which typically contains about 10% water, costs about $450 / tonne (eg. white rice). Hence the cost of the dry carbohydrate is about:
($450 / tonne) X (1 tonne / 0.9 tonne carbohydrate) = $0.50 / kg
A key issue in synthetic fuel production is use of efficient agricultural techniques to reduce the cost of the dry carbohydrate feedstock. In synthetic fuel production, unlike lumber or paper production, there is little concern about cellulose fiber quality. The dominant issue is the cost of cellulose. If the synthetic fuel production facility is located close to where the biomass is grown a larger fraction of the biomass can be used without concern about rot, fungus formation, etc. Possibly the dry carbohydrate cost can be reduced to about $0.30 / kg.
A saw mill can debark green logs and reduce them to fine wood chips (saw dust) at a cost of $130 / tonne of wood chips. The moisture content of these wood chips is 40%. The lignin content is about 30% of the remainder. Hence the cost of the contained dry carbohydrate is:
$130 /(0.7 X 600 kg) = $0.3095 / kg carbohydrate.
COST OF FEEDSTOCKS:
Production of 1 kg of bio-methanol requires 937.08 gm of carbohydrate plus
(1000 - 937.08) = 62.92 gm of hydrogen.
The cost of material inputs required to make 1 kg of methanol is in the range:
(937.08 gm carbohydrate X $0.3095 / 1000 gm carbohydrate) + (62.92 gm hydrogen X $3.01866 / 1000 gm hydrogen)
= $0.290 + $.190
= $0.48 / kg methanol
(937.08 gm carbohydrate X $0.50 / 1000 gm carbohydrate) + (62.92 gm hydrogen X $3.20326 / 1000 gm hydrogen)
= $0.46854 + $0.201549
= $0.6701 / kg methanol
This cost does not include any of the costs related to financing the methanol production equipment, operating the equipment, maintaining the equipment and storing, distributing and selling the methanol product.
By comparison the purchase price of methanol made from fossil fuels varies from:
($227.99 / 55 US gal methanol) X (.3326 US gal methanol / kg methanol) = $1.38 / kg methanol in a single drum shipment
to as low as $0.46 / kg in multi-tonne shipments.
Methanol (CH3OH) is not an ideal fuel because it corrodes aluminum. Methanol also attacks certain rubbers. Methanol also does not have the high energy density of propane or gasoline. When burned in a non-condensing boiler methanol loses significant latent heat via stack loss due to the high water vapor content in the combustion exhaust gas exhaust. However, producing methanol is relatively simple. From an environmental perspective methanol is relatively safe because most life forms on planet Earth have evolved to be tolerant to the small concentrations of methanol that naturally occur in the environment.
To produce a fuel suitable for bulk consumer use methanol should be further upgraded to propane or an equivalent energy dense liquid fuel like gasoline in accordance with the chemical equation:
6 CH3OH + 2 H2 = 2 C3H8 + 6 H2O
In this equation the relative weights of the components are:
6 [12.011 + 4(1.008) + 15.999] = 192.252
2 [2(1.008)] = 4.032
2 [3(12.011) + 8(1.008)] = 88.194
Hence 1 kg of methanol yields:
1 kg X (88.194 / 192.252) = .4587 kg propane
1 kg X (4.032 / 192.252) = 0.02097 kg hydrogen.
Thus production of 1 kg of propane requires:
(1 / .4587) kg methanol + (0.02097 / .4587) kg hydrogen
= 2.18007 kg methanol + 0.045716 kg hydrogen
= 2.18007 [.93708 kg carbohydrate + .06292 kg hydrogen] + 0.045716 kg hydrogen
= 2.0429 kg carbohydrate + .182886 kg hydrogen
= 2.0429 [1 / ,7] kg dry biomass + .182886 kg H2 [1 kWh elec/ .01717 kg H2]
= 2.9184 kg dry biomass + 10.651 kWh elec
= 2.9184 [1 / 0.6] kg wood + 10.651 kWh elec
= 4.864 kg wood + 10.651 kWh elec
= 4.864 kg wood [1 tonne / 1000 kg X $130 / tonne] + 10.651 kWh [$.055 / kWh]
= $.63232 + $0.5858
Thus the cost of inputs alone for making propane and like energy dense liquids from biomass and hydrogen is about $1.22 / kg.
The equipment amortization cost, operating cost, maintenance cost, transportation cost and sales cost, etc are additional.
COMMERCIAL SYNTHETIC LIQUID FUELS:
In certain markets synthetic liquid fuels are being made from electrolytic hydrogen and biomass feedstocks. For example, during the production of lumber sawmills convert about half of the available wood mass into chips. These chips, together with electrolytic hydrogen, are an excellent feedstock for producing synthetic high energy density non-fossil hydrocarbon fuels.
COST COMPARISON WITH FURNACE OIL:
The cost of delivered number 2 fuel oil in Ontario is about $1.12 / litre plus HST. Its density is 0.85 kg / litre. Hence its cost without tax is ($1.12 / litre) X (1 litre / 0.85 kg) = $1.317 / kg.
The financial viability of agriculture to produce biomass for fuel production is determined by:
1. Market demand for high value carbohydrate products such as lumber that inherently produce biomatter waste;
2. Proximity of a large ongoing source of biomatter waste;
3. The prices of liquid fuels and their substitutes;
4. Access to a market with liquid fueled vehicles and liquid fuel heating;
5. The incentives or taxes related to synthetic hydrocarbon fuels and fossil carbon emissions;
6. The cost of synthetic fuel production equipment;
7. The competing uses that a farmer has for his land, irrigation water and financial capital;
8. The cost of off-peak electricity.
9. The presence of other on-peak coincident electricity loads to absorb the costs of electricity transmission/distribution.
ENERGY REQUIREMENT IN ONTARIO:
The above analysis shows that the electrolysis electricity requirement for displacing 2004 liquid fossil fuel used in Ontario is about:
15.7 X 10^9 litres / year X (0.85 kg / lit) X 10.651 kWh / kg
= 142.14 X 10^9 kWh / year
To totally displace combustion of fossil fuels in Ontario it is also necessary to displace both natural gas and coal which is still used for applications such as steel production.
By comparison, total annual electricity production in Ontario in 2004, including electricity produced by combustion of fossil fuels, was about 151 X 10^9 kWh / year. The total amount of nuclear and renewable electricity generation has to be almost tripled to completely displace all existing fossil fuel consumption. In constructing this new non-fossil electricity generation it is essential to keep the cost of the resulting electricity as low as possible. Each synthetic fuel refinery must be located as close as practical to a large supply of biomass, close to an electricity transmission line and close to a supply of cooling water.
A constraining issue is the natural rate of formation of the required total amount of required biomass. This biomass rquirement is estimated as:
15.7 X 10^9 lit / year X .85 kg fuel / lit X 4.864 kg wood / kg fuel
= 64.91 X 10^9 kg wood / year
= 64.91 X 10^6 tonne wood / year
In the year 2006, during which lumber and pulp production in Canada peaked, Statistics Canada indicates that the total Canadian lumber production was 81.2 X 10^6 m^3 and total Canadian pulp production was 23.4 X 10^6 tonnes. Allowing for the average density of the wood, the average water content of the wood and the average ratio of wood chips to lumber production suggests that the total available dry biomatter in Canada suitable for methanol production is about 10^8 tonnes per year. Just to meet the Ontario synthetic liquid fuel requirement biomatter production and harvesting in Canada must become significantly more efficient. Clearly world wide per capita use of liquid hydrocarbon fuels will have to sharply decrease.
This calculation indicates that in the future biomass production and harvesting will be a major industry. Meeting the present Ontario liquid fuel requirement with synthetic liquid fuel requires about 5 tonnes of dry biomass per person per year.
As carbon based fuels increase in price it may be necessary for mankind to adopt a non-carbon portable chemical fuel technology, perhaps based on liquid ammonia. This chemical alternative poses serious risks in accident situations and will require extensive public education.
This web page last updated January 9, 2023.
|Home||Energy Physics||Nuclear Power||Electricity||Climate Change||Lighting Control||Contacts||Links|