BELL PERFORMANCE FUEL ISSUES SERIES: THE GOOD AND THE BAD ABOUT LPG
LPG in the United States is used mostly in home/industrial heating and cooking systems and large municipal transportation fleets. In both applications, LPG offers cleaner combustion at an inexpensive fuel cost. Although it is a much cleaner burning fuel than diesel or gasoline, contrary to long-held belief, LPG is not thoroughly without its fuel-related performance issues.
LPG, CNG and natural gas are all gaseous fuels composed of some of the same elements – propane and butane. LPG and “propane” are terms used interchangeably in the United States, but tend to average the same thing – a blend of 70% propane and 30% butane, with a few trace elements additional (like a mercaptan-kind smell agent so you can smell a gas leak). There can be minor differences in LPG blends sold between different states, including California, which has a associate of different specifications to dictate the ratio of propane and butane in the overall gas.
In crude oil refining, LPG is the first part that comes off the distillation tower, so it is always produced when crude oil is perfected to make gasoline and diesel. At normal temperatures, LPG is a gas but is usually cooled and compressed into cylinders for storage. Compressed LPG has an energy value 270 times of the same quantity of gaseous LPG.
LPG use is more popular in Europe and Asia than in the United States, as foreign consumers tend to be more ahead of the curve than US consumers for environmental concerns and the dispensing system is more developed. Use of LPG in the United States is confined mainly to home heating systems, industrial applications (like forklifts and industrial boiler strength generation), large municipal bus and transportation fleets, and small consumer product use like gas grills. LPG-powered transportation (cars, trucks and scooters) is much more shared in Europe and Asia.
For the United States to catch up in LPG use, dispensing infrastructure will have to greatly enhance – it is much more shared to find an LPG filling stop in Europe than it is in the United States. Expanding third world countries like China (now the 2nd largest economy in the world, passing Japan) and India rely heavily on LPG to fuel the transportation needs of their citizenry, in addition as to satisfy the growing global pressure to be more environmentally friendly. In response to this pressure, you have the Chinese centralized government mandating a 25% reduction in pollution emissions within the next five years. While the US has gravitated towards ethanol and biodiesel replaceable fuel blends to meet these demands, LPG fuels are central to plans to meet the mandates in these foreign countries experiencing explosive growth. GOOD POINTS ABOUT LPG FUELS
LPG molecules are small – 3 and 4-carbon chains compared to the 8-18+ carbon-chain molecules found in gasoline and diesel – and burn very cleanly compared to gasoline and diesel. This better combustion method less carbon buildup in the engine and longer life for both spark plugs and lubricating oil. This is a plus for all kinds of consumers who need to have maximum fuel value from their vehicles, large and small.
Fuel-combustion emissions are also pretty low for LPG compared to the popular automotive fuels – unburned hydrocarbon and particulate emissions are very very low, as are sulfur gas emissions and NOx (nitrogen oxide) emissions, which are both precursors for smog in polluted urban areas. Evaporative emissions (such as what happens when fuel is dispenses – some of the fuel escapes into the air) are very low due to the necessary closed LPG fuel delivery systems at dispensing stations.
LPG has a lower gross sulfur content than gasoline, reducing the possible for corrosion in storage systems.
These facts make LPG a favorite fuel for environmentally-conscious consumers, including local governments who confront mandates from their constituency and higher up in the governmental ladder to be more “green”. All of this adds up to the fact that LPG fuels are great for the ecosystem, except the carbon emissions they generate in the form of CO2.
LPG FUEL ISSUES
Because LPG is so clean burning most consumers and already some gas fuel dispensing professionals are unaware that LPG fuels aren’t without their fuel-related problems or room for improvement.
means Fuel Availability in the United States
Very few LPG-only consumer vehicles are sold in the USA each year. You can buy conversion kits that will turn your regular gasoline-powered means into a dual flex-fuel means that can switch between gasoline and LPG. Conversion kits cost $2000-$4000. Unfortunately, already if you choose to do this, the simple availability of means LPG fueling stations is a prohibitive problem in the US for further expansion of this kind of green fuel. California has the most means “propane” filling stations – about 600 of them. Across the nation, only 3% of the LPG used is sold for means use.
Mileage Range for Vehicles
Consumers in the United States who do have flex-fuel LPG vehicles can confront mileage range issues with their LPG tanks. Remember that compressed LPG has a different density than gasoline or diesel. A typical LPG car like the converted 2008 Honda Civic can get as much as 36 mpg. That’s great mileage. Unfortunately, because of the character of LPG compression, despite the 36 mpg (24 mpg city), the Civic can only go about 185 miles on a complete tank of LPG fuel.
place Buildup from Refinery-Sourced Impurities
LPG taken straight from the original source (the ground) is a clean combination of propane, butane and other hydrocarbon gases and does not contain double-bonded olefin impurities like propene (propane with a double-bond). The pure LPG fuel without impurities burns very cleanly to produce tremendous heat energy (21,000 BTUs per pound) with a minimum of deposits and unhealthy emissions like carbon monoxide.
Unfortunately a portion of the LPG typically obtainable in the marketplace has been produced by cracking methods at a refinery (to maximize the more profitable products of gasoline and diesel) and contains unstable molecules called alkenes and olefins. Cracking processes include the chemical splitting of longer molecules into shorter ones – the refinery will divided the heaviest molecules (like heavy fuel oil) to create more gasoline and diesel. While doing this, additional supplies of LPG are produced alongside this. But these additional yields of LPG are not pure LPG fuel, because they contain cracked molecules from being part of the other cracking course of action.
These cracked LPG fuels contain alkenes (molecules with reactive un-saturated double-bonds) which tend to react with each other, water and other molecules from the fuel and ecosystem (S, O, N) to produce longer-chain polymers, which end up as heavy-end deposits. These unstable molecules contain double-bonds which cause them to react with other molecules in the fuel and the surrounding ecosystem (including oxygen and sulfur) to form long polymer molecules. These deposits, because they are longer chains, are heavier and do not dissolve well in LPG fuels, as propane is a poor solvent for such species. Hence they will precipitate out of the fuel before and during vaporization. Once this happens, these deposits cannot be re-dissolved into the fuel.
These heavy deposits will build up in vaporizers and converters, the vaporizer lines, the fuel injectors and injector metering orifices and the burners. This is true whether it’s a means or a home heating system powered by propane. Due to the heavy character of the deposits, they tend to stay and build up in the areas where they first fall.
The Effect of LPG Deposits on Performance
Once these areas experience place buildup, it affects the fuel flow rate and the air/fuel mixing, making the system much less efficient and raising the emissions produced. You can also see a progressive reduction in the fuel efficiency of the system, whether heating or automotive. Not only is this because deposits cause the fuel to burn less efficiency, but deposits can also have a sponge-like effect, soaking up LPG fuel and releasing it more slowly over time, which deviates from how the system was designed to function.
In a means that burns LPG for fuel, place buildup from olefins causes the octane requirement by the engine to increase. This is because these deposits also build up in the combustion chamber and the cylinder spaces, changing the quantity within the cylinder, which is slightly what determines octane requirement for correct firing of the fuel at the correct cylinder position. LPG fuel typically has a very high octane rating, 96-100. So the effect of deposits on this rating is truly amplified and greater in an LPG-burning engine than a regular gasoline engine designed to perform well on 87 or 89 octane gasoline.
A system with place buildup may typically experience difficulty starting up in cold weather. As deposits build up in a furnace or vehicular system, they start to affect how well the fuel vaporizes and how well it flows by the fuel delivery system. This is especially an issue with LPG in the winter, which must start up closest. These kind of deposits will hinder how well this fuel vaporizes and performs in cold weather. This can be an issue if the fuel vaporizer gets fouled with deposits – the fuel doesn’t vaporize well enough to perform as it should.
When used in vehicular applications (cars and trucks), LPG proves to be a dry fuel that doesn’t provide the same kind of lubrication for basic fuel delivery parts that liquid fuels can. Over time, LPG drivers tend to find excessive use on certain basic engine parts. Valves, injectors and compression rings can be the most shared parts affected.
In furnace systems, some built-up deposits can be abrasive and may break off in the turbulent air flow of the fuel delivery system. When this happens, they can use on metal surfaces and cause damage. This typically happens slowly over a long period of time, but can end up leaving you with costly repair bills for system maintenance.
To prevent excessive use on vehicular and industrial or home furnace system parts, it can be advantageous to treat the LPG fuel with a lubricant. Water and Moisture Collection
Contrary to perception, water and moisture can get into the LPG fuel via the supply chain. When this happens, fuel fouling can consequence as the fuel undergoes oxidation while reaction with the oxygen in the water. Oxidation responses cause the pure propane/butane molecules to react and polymerize (stick together), forming heavy deposits that can sink to the bottom of the tank or be carried with the LPG fuel into downstream storage containers where they end up accumulating and causing deposits in the vehicles and furnace systems that ultimately burn the fuel.
LPG and other compressed gases are excellent choices for consumers looking for a clean fuel that is comparatively friendly for the ecosystem, burning with low emissions and soot output. Vehicles running on LPG fuel (if you can find them) have low emissions and get high miles per gallon (although the quantity of LPG which can be stored in a means is less than a gasoline or diesel fuel tank capacity). LPG’s problems are pretty minor compared to biodiesel or ethanol and can be resolved pretty easily if the fuel supplier additizes the LPG fuel.