The high anti-knock properties of methanol, combined with the possibility of its production from non-oil raw materials, make it possible to consider this product as a promising high-octane component of motor gasolines. The optimal addition of methanol is from 5 to 20%; at such concentrations, the gasoline-alcohol mixture is characterized by satisfactory operational properties and gives a noticeable economic effect. The addition of methanol reduces the heat of combustion of the fuel and the stoichiometric coefficient with insignificant changes in the heat of combustion of the mixture.

Due to the change in stoichiometric characteristics, the use of a 15% methanol additive (mixture M15) in the standard power supply system leads to a depletion of the air-fuel mixture by about 7%. At the same time, with the introduction of methanol, the octane number of the fuel increases (on average by 3–8 units for a 15% additive), which makes it possible to compensate for the deterioration of energy performance by increasing the compression ratio. At the same time, methanol improves the fuel combustion process due to the formation of radicals that activate oxidation chain reactions. Investigations of the combustion of gasoline-methanol mixtures in single-cylinder engines with standard and layer-by-layer mixture formation systems have shown that the addition of methanol reduces the ignition delay period and the duration of fuel combustion. In this case, the heat removal from the reaction zone decreases, and the mixture depletion limit expands and becomes maximum for pure methanol.

The peculiarities of the operational properties of methanol are also manifested when it is used in a mixture with gasoline. For example, the effective efficiency of the engine and its power increase, but the fuel efficiency is deteriorated. According to the data obtained on a single-cylinder installation, at e = 8.6 and n = 2000 min-1 for a mixture of M20 (20% methanol) in the region of k = 1.0-1.3, the effective efficiency increases by about 3%, the power - by 3-4%, and fuel consumption increases by 8-10%.

To cold start the engine with a high methanol content in the fuel mixture or low temperatures, electric heating of air or air-fuel mixture, partial recirculation of hot exhaust gases, additives to the fuel of volatile components, and other measures are used.

The addition of methanol to gasoline generally improves vehicle toxicity. For example, in studies carried out on a group of 14 cars with a mileage of 5,000 to 120,000 km, the addition of 10% methanol changed hydrocarbon emissions both upwards by 41% and downwards by 26%, which on average amounted to 1% increase. ¬nia. At the same time, CO and NOx emissions decreased on average by 38 and 8%, respectively, for the entire group of vehicles.

One of the most serious problems hindering the use of methanol additives is the low stability of gasoline-methanol mixtures and their especially sensitivity to water. The difference in the density of gasoline and methanol and the high solubility of the latter in water lead to the fact that the ingress of even small amounts of water into the mixture leads to its immediate stratification and precipitation of the water-methanol phase. The tendency to delamination increases with decreasing temperature, increasing water concentration and decreasing aromatics content in gasoline. For example, with a content of 0.2 to 1.0% (vol.) Of water in the fuel mixture, the delamination temperature rises from -20 to + 10 ° C, that is, such a mixture is practically unsuitable for operation. Below are the limiting concentrations of water Ccr in various gasoline-methanol mixtures:

To stabilize gasoline-methanol mixtures, additives are used - propanol, isopropanol, isobutanol and other alcohols. At a water content of 600 ppm, the clouding of a conventional M15 mixture begins already at -9 ° C, at -17 ° C, the mixture stratifies, and at -20 ° C, almost complete destabilization occurs. The addition of 1% isopropanol reduces the separation temperature by almost 10 ° C, while the addition of 25% maintains the stability of M15 mixtures even with a low content of aromatic compounds in gasoline down to almost -40 ° C in a wide range of water content.

Due to the high cost and limited production of stabilizers for gasoline-methanol mixtures, it was proposed to use a mixture of alcohols, mainly isobutanol, propanol and ethanol. Such a stabilizing additive can be obtained in a single technological cycle of joint production of methanol and higher alcohols. The addition of even small amounts of methanol changes the fractional composition of the fuel. As a result, the tendency to the formation of vapor plugs in the fuel supply lines increases, although with pure methanol this is practically excluded due to its high heat of vaporization. According to calculations, for a 10% mixture of methanol with gasoline, the formation of vapor plugs is possible at ambient temperatures by 8-11 ° C lower than for the base fuel. Correction of the fractional composition of the base fuel is possible by reducing the content of light components, taking into account the subsequent addition of methanol.

The corrosive activity of gasoline-methanol mixtures is much lower than that of pure methanol, but in some cases it is significant and strongly depends on the presence of water. For example, in mixtures containing 10-15% methanol, steel, brass and copper do not corrode, while aluminum corrodes slowly with a color change.

Abroad, in carburetor engines, mixtures of 10–20% ethanol with petroleum gasolines, called "gazohol", have been used in practice. According to the ASTM standard, developed by the US National Alcohol Fuels Commission, gasohol with 10% ethanol is characterized by the following parameters: density 730-760 kg / m3, boiling temperature range 25-210 ° C, heat of combustion 41.9 MJ / kg, heat of vaporization 465 kJ / kg, saturated vapor pressure (38 ° C) 55–110 kPa, viscosity (-40 ° C) 0.6 mm2 / s, stoichiometric coefficient 14. Thus, by most parameters, gasohol corresponds to motor gasolines.

When using watered ethanol under conditions of low ambient temperatures, to prevent stratification, it is necessary to introduce stabilizers into the mixture, such as propanol, sec-propanol, isobutanol, etc. Thus, the addition of 2.5-3.0% of isobutanol ensures the stability of the ethanol mixture, containing 5% water, with gasoline at temperatures down to -20 ° C.

The greatest distribution of gasohol is in Brazil, where, since 1975, a government program has been carried out to use renewable sources of plant raw materials for the production of ethanol and its use as a vehicle fuel. The number of cars running on ethanol and gasohol in this country was in 1980. 2411 and 775 thousand pieces. respectively. By 2000, from the projected fleet of passenger cars in Brazil, 19-24 million units. on alcohol fuels should be operated from 11 to 14 million. In the United States on 1000 dispensers in 20 states, cars are filled with gasohol containing 10-20% ethanol.

In European countries with limited capacity for ethanol production and its high cost, more interest is shown in the use of methanol additives. The greatest use of methanol as a motor fuel and its components was obtained in the Federal Republic of Germany. As part of a three-year federal research program for alternative energy sources in the period 1979-1982. in the Federal Republic of Germany, more than 1000 vehicles were operated on alternative fuels, mainly methanol and gasoline-methanol mixtures. To operate on the M15 mixture, 850 vehicles were converted, on the M100-120 mixture, and 100 vehicles on diesel fuel with the addition of methanol. The M100 mixture is 95% methanol, the remaining 5% includes light gasoline fractions (usually isopentane), which are necessary to facilitate engine start-up. For winter operation, the content of gasoline fractions increases to 8-9%, while the water content in the mixture is allowed no more than 1%.

A mixture of M15 of 85% of gasoline fractions contains at least 45% of aromatic hydrocarbons; the content of tetraethyl lead in the mixture does not exceed 0.15 g / kg, and the water content is within 0.10% (practically 0.05-0.06%). Mixture M15 also contains anti-corrosion additives.

In a number of countries, methyl tert-butyl ether (MTBE) is used as an additive expanding the resources of high-octane gasolines. Its anti-knock efficiency is 3-4 times higher than that of alkyl gasoline, due to which it is possible to obtain a wide range of unleaded high-octane gasolines with the help of ether. Methyl tert-butyl ether is characterized by the following parameters: density 740 - 750 kg / m3, boiling point 48 - 55 ° С, saturated vapor pressure (25 ° С) 32.2 kPa, heat of combustion 35.2 MJ / kg, octane number 95-110 (motor method) and 115-135 (research method). Ether exhibits the greatest antiknock efficiency in the composition of straight-run gasolines and catalytic reforming of the usual mode.

Domestic gasolines A-76 and Ai-92 with additions of 8 and 11% methyl tert-butyl ether, respectively, meet the requirements of GOST 2084-77 in all respects and showed the best performance in terms of a set of qualification assessment methods. Gasolines with ether additives are characterized by good starting qualities and at lower engine speeds have higher actual octane numbers compared to commercial gasolines.

Fuel efficiency and power indicators of the engine when running on gasoline with ether are at the level of commercial gasoline. In this case, the toxicity of the exhaust gases is somewhat reduced, mainly due to the reduction in carbon monoxide emissions. Changes and irregularities in the state and operation of engine systems when using gasoline with ether are not observed.

Methyl alcohol could become a more environmentally friendly type of motor fuel. There are already precedents in this area.

So, in the early 90s. an experiment was carried out in Stockholm to test this type of fuel in public transport. The prime cost of methanol is less than that of gasoline, and it requires minimal readjustment of gasoline engines (it is produced by a catalytic method from natural gas). This type of motor fuel could be viewed from an economic point of view as very promising. The ecological effect of its application needs to be clarified, although during the experiment in Stockholm, a decrease in the gross emission of harmful substances was observed by almost 5 times.

A significant obstacle to the widespread use of methanol in Russia is the high hygroscopicity of methanol and difficulties with starting the engine in the cold season. Critics of methanol argue that converting natural gas to methanol releases the same amount of carbon dioxide as burning gasoline.

The technology of automobile power plants with methanol is well known and developed. The first widespread methanol fuel is M85 gasoline - (a mixture of 85% methanol and 15% gasoline). Pure methanol poses problems during cold starting of the engine, so 15% gasoline is added to increase the fuel volatility and ease of starting. Fuel M-85 has an octane number of 100 (for gasoline - 87-95). The higher octane rating provides smoother combustion at a higher compression ratio than in carbureted engines (knock bases). The higher compression ratio results in an efficient engine design in which power consumption can be optimized. It is no coincidence that for a number of years, pure methanol with an octane number -PO has been used in racing cars. Methanol also provides a higher flame front speed than gasoline, which increases engine rpm and improves engine efficiency.

In addition, having a higher evaporation temperature, methanol allows the engine to cool faster, so that a conventional liquid-cooled radiator can be replaced with an air-cooled radiator, which saves weight.

Oxygen-containing additives to gasoline can be considered as an intermediate link in resolving the issue of replacing fuel. Although they somewhat reduce the calorific value of the fuel, this is offset by an increase in the octane number and a decrease in the emission of harmful substances into the environment. These additives include methanol (methyl alcohol CH3OH) and methyl tert-butyl ether (MTBE - CH3OS (CH3) 3). Due to the introduction of oxygenated additives in the United States, sales of lead gasoline decreased from 45% in 1983 to 5% in 1990.

In any modern car, you can use a mixture of 90% gasoline and 10% methyl alcohol without any alterations - the so-called gasohol, which is not inferior to high-quality leaded gasoline, with lower emissions of pollutants.

Ethanol. Fuel obtained by fermentation of various crops. Due to the relatively high cost and advantages of other alternative fuels, ethanol is unlikely to be widely used in the future.

Like methanol, ethanol has a high octane number and can be used to improve engine performance.
Ethanol has been widely used in the United States for the past 10 years and is used as a 10% additive in gasoline. Brazil uses ethanol produced from sugar cane. It is known as B-100 and needs some gasoline additions when used in colder climates than Brazil.

In the future, ethanol may be produced from water if the technology is affordable.

When using methanol as a fuel, it should be noted that the volumetric and mass energy intensity (heat of combustion) of methanol (specific heat of combustion = 22.7 MJ / kg) is 40-50% less than that of gasoline, however, at the same time, the heat output of alcohol-air and gasoline fuel-air mixtures during their combustion in the engine, it differs slightly due to the fact that the high value of the heat of vaporization of methanol improves the filling of the engine cylinders and reduces its heat density, which leads to an increase in the completeness of combustion of the alcohol-air mixture. As a result, the engine power is increased by 7-9%, and the torque by 10-15%. Race car engines running on methanol with a higher octane rating than gasoline have a compression ratio greater than 15: 1 [ source not specified 380 days], while in a conventional spark-ignition ICE, the compression ratio for unleaded gasoline is typically less than 11.5: 1. Methanol can be used both in classic internal combustion engines and in special fuel cells to generate electricity.

Separately, it should be noted an increase in the indicator efficiency when a classic ICE is running on methanol compared to its operation on gasoline. Such an increase is caused by a decrease in heat losses and can reach several percent

Flaws

Methanol etchant aluminum. The problem is the use of aluminum carburetors and fuel injection systems for internal combustion engines. This applies mainly to raw methanol, which contains significant amounts of formic acid and formaldehyde impurities. Technically pure methanol containing water begins to react with aluminum at temperatures above 50 ° C, but does not react at all with ordinary carbon steel.

Hydrophilicity. Methanol draws in water, which causes stratification of gasoline-methanol fuel mixtures.

Methanol, like ethanol, increases the plastic vapor permeability of some plastics (eg HDPE). This feature of methanol increases the risk of an increase in the emission of volatile organic substances, which can lead to a decrease in the concentration of the zone and an increase in solar radiation.

Reduced volatility in cold weather: engines running on pure methanol can have problems starting at temperatures below + 10 ° C and have increased fuel consumption before reaching operating temperature. However, this problem can be easily solved by adding 10-25% gasoline to methanol.

The low level of methanol impurities can be used in existing vehicle fuels using proper corrosion inhibitors. T. n. The European Fuel Quality Directive allows the use of up to 3% methanol with an equal amount of additives in gasoline sold in Europe. China today uses over 1,000 million gallons of methanol per year as a vehicle fuel in low-level blends used in existing vehicles, as well as high-level blends in vehicles designed to use methanol as a fuel.

In addition to the use of methanol as an alternative to gasoline, there is a technology of using methanol to create on its basis a coal suspension, which in the USA is commercially named "methacoal". This fuel is offered as an alternative to fuel oil, which is widely used for heating buildings (Fuel oil). Such a suspension, in contrast to water-carbon fuel, does not require special boilers and has a higher energy consumption. From an environmental point of view, such fuels have a lower carbon footprint than traditional synthetic fuels derived from coal using processes where part of the coal is burned during the production of liquid fuels.

Comparison of the physicochemical properties of methanol and gasoline

Methanol as a motor fuel has a high octane number and a low fire hazard. At the moment, this type of fuel is most widespread in the United States. For many years, the most common brand M-85 (85% mixture with gasoline), as well as M-100 (pure methanol) have been produced here.

The use of methanol as a fuel in our country has received increased attention since the days of L.A. Kastandov, who specifically for the study of this problem created an independent institute "GosNIImetanolproekt". However, when using methanol as a fuel, a number of technical problems arise associated with significant differences in the properties of methanol and gasolines.

The heat of combustion of methanol is 2.24 times less than that of gasoline. Methanol has a higher latent heat of vaporization, low vapor pressure, low boiling point, increased hygroscopicity and an increased tendency to form azeotropic mixtures with some constituents of gasoline, as well as an increased tendency to incineration.

In addition, methanol is highly corrosive to metals and some plastics. Methanol vapors are more toxic than gasoline vapors and cause severe poisoning when ingested, blindness and even death.

Thus, the use of pure methanol as a fuel (fuel M-100) for internal combustion engines requires significant reconstruction of the vehicle engine and careful handling.

The positive properties of methanol include its high detonation resistance and higher combustion rates of air-fuel mixtures. At the same time, the low heat of combustion does not reduce the power indicators of the engine, since their determining factor is not the heat of combustion of the fuel, but the heat of combustion of a unit mass of the fuel-forming mixture, which is 3-5% higher in methanol-air mixtures than in gasolines. It should be said that this requires 2.3 times more methanol.

The high latent heat of vaporization of methanol (3.66 times higher than that of gasoline) has a qualitative effect on the mixture formation process. First of all, this fact is the reason for the worst starting qualities of a cold engine at low temperatures. On the other hand, this property of methanol leads to a decrease in the thermal stress of engine parts and an increase in the weight filling of the cylinders with a fresh charge, which contributes to an increase in engine power.

Among other things, when using methanol, atmospheric pollution is significantly lower, carbon formation on the working surfaces of the combustion chamber and less coking of the parts of the cylinder-piston group are lower.

The level of emissions of harmful substances when using gasoline as fuel, M-85 and M-100

Emissions, mg / km	Petrol	M85	M100
∑ Hydrocarbons (THC)	161,59	111,87	124,30
CO	733,37	683,65	870,11
NOx	490,99	379,12	285,89
Benzene	7,79	4,38	0,32
Toluene	33,66	8,66	2,11
1-3 butadiene	0,19-0,50	0,44	2,05
Formaldehyde	4,78	13,87	21,76
Acetaldehyde	0,94	10,02	0,27

For methanol to be used as a fuel, its prices need to be affordable. Currently, the domestic and world markets are experiencing extremely high prices for methanol. This does not contribute to its widespread use in this area.

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When using methanol as a fuel, it should be noted that the volumetric and mass energy content of methanol is 40-50% less than that of gasoline, however, the heat output of air-alcohol and gasoline-air fuel mixtures during their combustion in the engine differs slightly due to the fact that the high value of the heat of vaporization methanol improves the filling of the engine cylinders and reduces its heat density, which leads to an increase in the completeness of combustion of the alcohol-air mixture. As a result, the increase in engine power increases by 10-15%. Race car engines running on methanol with a higher octane rating than gasoline have compression ratios in excess of 15: 1, while conventional spark ignition ICEs typically have a compression ratio of 11.5: 1 for unleaded gasoline. Methanol can be used both in classic internal combustion engines and in special fuel cells to generate electricity.

Flaws:

• methanol etches aluminum. The problem is the use of aluminum carburetors and injection systems for supplying fuel to the internal combustion engine.
• hydrophilicity. Methanol draws in water, which causes clogging of the fuel supply systems in the form of jelly-like toxic deposits.
• methanol Like ethanol, it increases the plastic vapor transmission capacity of some plastics. This feature of methanol increases the risk of increased VOC emissions, which can lead to a decrease in ozone concentration and an increase in solar radiation.
• reduced volatility in cold weather: Methanol engines may have problems starting and consume more fuel before reaching operating temperature.

The low level of methanol impurities can be used in existing vehicle fuels using proper corrosion inhibitors. T. n. The European fuel quality directive allows the use of up to 3% methanol with an equal amount of additives in gasoline sold in Europe. China today uses over 1000 million gallons of methanol per year as a vehicle fuel in low-level blends used in existing vehicles, as well as high-level blends in vehicles designed to use methanol as a fuel. In addition to the use of methanol as an alternative to gasoline, there is a technology of using methanol to create a coal suspension on its basis, which in the USA has the commercial name "metacol". This fuel is offered as an alternative to fuel oil, which is widely used for heating buildings. Such a suspension, in contrast to water-carbon fuel, does not require special boilers and has a higher energy consumption. From an environmental point of view, such fuels have a lower carbon footprint than traditional synthetic fuels derived from coal using processes where part of the coal is burned during the production of liquid fuels.