The Ring of Fire has left many of the farms around Grantville scrambling to train enough horses for the fall harvest. About half of the tractors that came through the Ring Of Fire were designed to burn gasoline and with the help of the agriculture department they will be converted to use pressurized natural gas in its place in 1631. Grantville has an abundance of natural gas; therefore, this conversion will put half of the modern equipment back into service for the first year. The tractors that are the topic of this article are farm size tractors, not the smaller lawn tractors people with large yards like to use for mowing their grass. The small lawn tractors are mostly gasoline, powered but with conversion to run on natural gas they will come in handy for a lot of other jobs outside the farming industry. Examples of those alternate uses include the drawing of wagons and carriages designed for horses or serving as stationary PTO sources to operate machinery where electricity is not easily available.
With the exception of the old steam tractor, which was being rebuilt for the county fair, the rest of the tractors that came through the Ring of Fire are diesel engined machines. These diesel machines are sturdy beasts of burden; some of them are 30 years old and still running well. Several of the farms have their own diesel fuel storage tanks and can keep their equipment in the field with a little extra effort. In addition to petroleum diesel in these farm grade tanks, some isolated farms and homes outside of town use heating oil #2 in oil furnaces. Heating oil #2 is almost identical to farm grade diesel fuel #2 and burns quite well in diesel engines.
The question of how to keep these diesel tractors and the modern diesel trucks and cars also in the area fueled is the central focus of this article. Four different fuel alternatives and one fuel additive are explored. First is the petroleum diesel that came through the Ring of Fire and additives to it, including propane. Direct use of biologically derived oil is a second method, and the easiest short-term solution. Third, for the long run beginning in late 1634 the most likely method will be to burn crude diesel refined from petroleum sources. This crude diesel is easy to make once petroleum is available. Until that time, however, it would be a waste to let the diesel engines in Grantville sit idle. Finally, there is bio-diesel, which is a form of diesel fuel made from biologically derived oil.
Two methods are available to extend the petroleum derived diesel in up-time tanks. The first method is mixing. Any diesel engine, modern or archaic, will function quite well on a mix of 75% petroleum refined diesel and 25% light vegetable oil. Of course, this presumes the availability of cheap vegetable oil, which may be problematic in seventeenth-century Germany. The second alternative, if a competent mechanic is available, is to add propane injection to the diesel engine. Propane injection, also known as fumigation, will give an increase in diesel combustion efficiency. The propane acts as a combustion catalyst during the power stroke of the cylinder. If you are not a good mechanic let an expert do the conversion, otherwise you may get the propane amount too high and cause severe engine damage. When a turbo-charged diesel engine is properly fumigated with propane it will get a boost in torque and fuel economy resulting from the more complete combustion of the liquid fuel. Typical tractor engines are not turbo-charged and will only receive a small boost in efficiency from propane fumigation; many diesel farm trucks and pick-up trucks on the other hand are turbo-charged and would greatly benefit. No information is available on propane fumigation for engines that burn unrefined plant or animal oils; however with diesel or bio-diesel the engine boost amounts to a 10% increase in fuel economy. Combined with a 25% light vegetable oil mix in the fuel, this will total up as a 38% increase in fuel economy per unit of petroleum derived diesel used. The propane tanks used for this fumigation are generally the same ones found on backyard barbecue grills. With proper treatment some propane can be recovered from raw natural gas and used to refill these tanks if the knowledge and ability to install them on the diesels is available.
One of the most surprising things to come to light in researching this article was how easy it is to produce propane and butane from raw natural gas. Both propane and butane may be adapted to power gasoline engines where they provide 80% of the range of an equal volume of gasoline. This is an increase in range of 240 to 1 over low-pressure natural gas. To refine butane and propane out of raw natural gas you can follow any of several methods. The easiest one to explain is condensation.
Butane vaporizes at just below the freezing point of water, and propane vaporizes at about 45 degrees F below that. Using a metal coil run through a freezer you can condense butane out of the raw natural gas at about 10 degrees below freezing. The liquefied butane is separated out through a drip tube and stored in a regular propane cylinder like those used on portable backyard barbecues. When removed from the freezer, the butane will naturally warm to ambient temperature but will remain a liquid in the tank due to vapor pressure. If sufficient (probably cascaded) freezing is available, the partially refined natural gas can then be fed through a second condensing coil in a much colder freezer at about –30 C where the propane condenses. The propane may also be stored as a liquid under pressure in another tank. Natural gas in the eastern USA averages about 10% butane-propane-ethane and 90% methane. Using the freezing condenser method above refines about 2% butane and 4% propane by volume from the raw natural gas.
The second method to conserve up-time diesel works best with older diesel engines, but with a relatively simple heating set it will work for modern diesel engines as well. The newer machines in the diesel group can run on straight vegetable oil (SVO), or the animal equivalent, with a simple tank and fuel system heater added. These modifications involve installing a simple resistance heating element in the fuel tank, very similar to the ones used in engine blocks for winter weather. This can even be an electric heating pad fastened onto the bottom of the fuel tank. When the engine is not running, the heating element can be connected to an electrical outlet, to maintain a hot liquid oil temperature in the fuel tank and fuel system. While the engine is running, the waste heat from the liquid cooling system takes over. A copper tube is wrapped around the exterior of the fuel tank and attached to the tractor cooling system between the engine block and the radiator. This copper tube forces the hot engine coolant to circle the fuel tank several times before going to the radiator and maintains the oil as a hot liquid.
Hot and thin waste cooking oil or fresh vegetable oil burns just fine in older diesel engines; those that predate late twentieth-century pollution controls can be expected to have zero problems. Lighter oils such as corn or soybean oil work best. If the oil is kept sufficiently hot and thin, tallow, butter or lard can also be used as fuel. If bio-diesel or stockpiles of fossil fuel derived diesel are available, it is recommended that a small diesel tank be added to the newer equipment. This will allow the more refined fuel to be utilized when starting the engine and bringing it up to full power. Once at full power, one can switch to the biologically derived unmodified fuel oil. About five minutes prior to shutting down the engine, it should be switched back to the refined fuel. While these modifications are not mandatory, they do ensure that the equipment will have very little problem with clogged fuel injectors. The refined fuel serves as a fuel system cleaner during startup and shutdown, purging the lines and filter. Using refined fuel in this supplemental tank requires less than one percent of the total fuel supply for the newer vehicle and keeps the fuel pump and filter full of refined fuel when the equipment is shut off. This in turn helps prevent any pitting or premature wear that in some rare cases may be caused by free fatty acids that are present in all unrefined biologically derived fuel oils. Of course, again, this technique is dependent on the availability of animal or vegetable fats.