Application
Due to its properties, such as high calorific value during combustion, residue-free combustion, harmlessness and safety when used correctly, and ease of use, propane is a versatile gas and is widely used both in industry and in everyday life. For industrial and domestic purposes, it is supplied as a technical propane-butane mixture. Butane (C4h20) is an organic compound of the alkane class. Today, the demand for SPBT is huge.
In production When performing gas-flame work at factories and enterprises: - in procurement production; – for cutting scrap metal; – for welding non-critical metal structures. For roofing work. For heating industrial premises in construction. For heating industrial premises (on farms, poultry farms, in greenhouses). For gas stoves, water heaters in the food industry. In everyday life - when cooking at home and camping; - for water heating; - for seasonal heating of remote premises - private houses, hotels, farms; - for welding pipes, greenhouses, garages and other household structures using gas welding stations.
Recently, it has been widely used as an automotive fuel, because cheaper and more environmentally friendly than gasoline. In the chemical industry, it is used in the production of monomers for the production of polypropylene. It is the raw material for the production of solvents. In the food industry, propane is registered as a food additive E944, as a propellant.
Coolant. A blend of dehydrated pure propane (R-290a) (a trade name for isobutane-propane blends) with isobutane (R-600a) does not deplete the ozone layer and has a low Greenhouse Potential (GWP). The mixture is suitable for functional replacement of obsolete refrigerants (R-12, R-22, R-134a) in traditional stationary refrigeration and air conditioning systems.
The quality indicators of liquefied hydrocarbon gases are determined according to GOST 10157-79.
Physical properties of LPG
The separation technology is based on different saturated vapor pressures and different pressures of the individual components. It is precisely due to the required gas elasticity and saturated vapor pressure that it becomes possible to use LPG as a source for heating, at which gas will begin to flow from the reservoir into the gas pipeline.
To achieve the necessary conditions, it is necessary to establish the optimal ratio of the liquid and vapor phases. The ability to maintain both liquid and gaseous states is a key feature of LPG.
During storage or transportation, part of the medium tends to go into the vapor phase, while the rest will remain in the form of a liquid. The difference in volume between the two phases is huge. For comparison, 1 m3 of a gaseous mixture is equal to 4 liters of liquefied gas, which means a decrease in volume by almost 250 times. Since the gas begins to expand when the temperature rises, when storing LPG, regulatory requirements should be taken into account - a gas tank (a special tank for storing LPG) or cylinders can be filled no more than 85%.
At a temperature of +20°C, the transition to the liquid phase for propane occurs at a pressure of 8.5 kgf/cm2, for butane at a pressure of 3.1 kgf/cm2. In this case, propane will not go into a gaseous state and will remain a liquid at a temperature of -43 ° C, and butane at a temperature of 0 ° C.
Thus, the ability of LPG to evaporate directly depends on the percentage of propane and butane, as well as on the air temperature. For example, at low ambient temperatures, the pressure of propane is higher than that of butane, and, consequently, its volatility is higher.
Summer and winter LPG mixtures
In previous years, special attention was paid to the ratio of the mixture of propane to butane in winter and summer:
- the winter version of the fuel provided for 70% propane, 30% butane;
- the summer version contained a smaller amount of propane - 50-60% and a larger amount of butane - 50-40%.
Studies have shown that at low ambient temperatures it is more efficient to use a mixture with a high propane content. At the same time, in the hot season, the amount of propane must be reduced. In summer, butane vaporizes much less rapidly, which reduces the risk of overpressure and prevents the relief valve from tripping.
At the moment, the division into summer and winter has become less relevant. Now the composition of LPG is calculated taking into account the individual characteristics of the object, which gives suppliers the opportunity to select the content of propane and butane for specific equipment. At the request of the Customer, the content of propane in the mixture can be increased up to 100%.
However, for the most efficient operation of gas equipment, it is necessary to carefully select the composition of liquefied petroleum gas. The correct ratio of the components of the propane-butane mixture provides sufficient overpressure in the tanks, guaranteeing uninterrupted hot water supply both in severe frosts and on hot days.
Chemical composition of LPG
There are two main ways to obtain LPG: from associated petroleum gas or from the condensate fraction of natural gas. The production process is carried out using an absorption-gas fractionation unit, which separates the gas into components:
- light hydrocarbons propane (C3H8) and butane (C4H10), which are the basis of LPG;
- hydrocarbons pentane (C5H12), methane (CH4) and ethane (C2H6);
- unsaturated hydrocarbons ethylene (C2H4), propylene (C3H6) and butylene (C4H8).
The content of propane and butane in the composition of LPG is at least 95%, the amount of unsaturated hydrocarbons is approximately 1%. Also in the composition is allowed the presence of isomeric compounds - isobutane and isobutylene.
The resulting propane-butane mixture is odorless, therefore, according to safety regulations, forced aromatization is carried out. A characteristic unpleasant odor is imparted by ethanethiol, which begins to be felt at 1/5 of the explosive concentration of LPG in the air.
What is propane
Propane, C3H8 and butane are organic compounds of the alkane class. A colorless, odorless gas. Very slightly soluble in water. Boiling point -42.1C. Freezing point -188C. Forms explosive mixtures with air at vapor concentrations from 2.1 to 9.5%. As a representative of hydrocarbon gases, it is flammable and explosive.
A small amount of propane is contained in natural gas, in industrial quantities propane is obtained in the process of high-temperature oil refining.
Since the gas itself practically does not smell, for safety and timely diagnosis of gas leaks by the human olfactory organs, odorants containing odorous substances are added to it. They are called "gas smells".
Where is propane used?
This gas is familiar to absolutely all modern people. Propane is used almost everywhere today. First of all, it concerns production processes.
So, propane technical gas is successfully used for gas-flame works at various production facilities. With its help, both metal cutting and structural welding are performed. When working with scrap metal, this gas is practically indispensable for the procurement of raw materials.
With no less success, propane is used in the production of thermal energy. Subsequently, the heat obtained with the help of propane technical gas is used to provide heat supply, both for industrial premises and for supplying heat to residential complexes.
In everyday life, propane gas finds its application in various fields of human activity.The most common way to use this gas is to use it as an energy carrier for gas stoves and gas water heaters. With its help, a person cooks food, heats water. Also in the individual housing sector, propane is used to organize space heating. For this, special equipment is installed. Propane gas is supplied to residential premises using gas pipelines. In some cases, the delivery of liquefied propane in special cylinders may also take place. The ratio between propane and butane in the mixture varies depending on the season - propane prevails in winter, and butane in summer.
Widely used as automotive fuel.
In the chemical industry, it is used in the production of monomers for the production of polypropylene.
It is the raw material for the production of solvents.
It is stored and transported in special containers (cylinders, tanks) without stabilizing additives at temperatures up to 50 °C.
What is the danger of propane?
First of all, its high explosiveness. The propane-butane mixture is about twice as heavy as air, therefore, when leaking, it does not evaporate, but accumulates and then one spark will be enough. And in a mixture with air, its explosiveness increases.
The second danger is that propane, getting into the air, mixes with it, displaces and reduces the oxygen content in the air. A person in such an atmosphere will experience oxygen starvation, and with significant concentrations of gas in the air, he may die from suffocation.
Propane - butane mixtures in liquid form corrode rubber, so it is necessary to carefully monitor the rubber products used in flame treatment equipment for metals, and, if necessary, replace them. The greatest danger of rubber corrosion exists in winter, when there is a high probability of liquid fraction getting into the hoses.
When working with propane-butane, it is not allowed to get the liquid fraction on the skin of the body, since frostbite occurs due to its rapid evaporation and heat removal.
Propane - butane seven has a large volumetric expansion coefficient. So for propane it is 16 times more than that of water, and for butane it is 11 times. Therefore, it is impossible to fill propane cylinders with a butane mixture of more than 85% by volume - it is very dangerous.
In general, we can say that for safety and peace of mind it is necessary to periodically monitor the maximum permissible concentration of gas in the room. If you feel a “smell of gas”, be sure to invite specialists to conduct an air examination.
Natural gas as a vehicle fuel
Propane or methane - what to choose?
Most cars that are switching to gas fuel use propane-butane. But how are things going with methane, because car manufacturers mass-produce cars using this fuel and consider it promising. So why is this happening.
Thirdly, natural gas reserves are huge, they will last for the next 150 years, and the price is 3 times cheaper than motor fuel. But keep in mind that the consumption of gas fuel will be slightly higher, because. one cubic meter of methane can drive as much as 1.1 liters of gasoline.
What are the disadvantages of methane? The main reason is the poorly developed infrastructure of methane gas stations - there are only 250 of them in Russia. It turns out that methane is more environmentally friendly, cheaper, safer than gasoline - and increases the engine life: it does not leave carbon deposits in the combustion chamber and does not wash off the oil film from the cylinder walls. But there are almost no gas stations. Therefore, another type of gas is preferable among private traders - it is propane-butane.
Pros and cons of propane-butane
Despite the fact that gas consumption is about 10-15% more than gasoline, the savings are significant. All costs for the purchase and installation of gas equipment pay off in 10-20 thousand kilometers, because the cost of propane-butane is one and a half times cheaper than gasoline.As a rule, there are no problems with refueling - the network of propane-butane gas stations is extensive throughout the country.
Gas equipment is actually an additional tank that increases the power reserve by 200-500 km. In operation, such a car will not cause trouble. The engine starts on gasoline and when the temperature reaches +25 ° C in the cooling system, it switches to gas fuel. Automation thereby ensures that the gas reducer does not freeze. In addition, the transition from one type of fuel to another can be made directly from the passenger compartment manually.
If you compare driving in the city, then there is no noticeable difference between driving on gas and gasoline. There will be no problems with starting off and reactions to the “gas” pedal, but in extreme modes, there is not enough power. Thus, operation on gas reduces the output of a serial engine with a capacity of 106 hp. up to 98 hp This can become uncomfortable when overtaking on the highway, but the solution is to switch to gasoline work in advance.
The main disadvantage is a significant reduction in the volume of the trunk. An additional tank is installed in the spare wheel niche, and the spare wheel itself will have to be moved to the trunk. In hatchbacks, the gas cylinder is generally in the cabin. This negates the design advantages that allow you to increase the volume of the trunk by folding the rear seats.
Another negative: gas is potentially more dangerous than gasoline. Of course, well-installed equipment does not cause trouble for the owner
However, close attention should be paid to its technical condition. Note that the gas is explosive only in a 5-10% ratio with air, and it is impossible to create such a concentration in the open air.
And even more so in a moving car.
Less significant disadvantages of refueling a car with gas fuel include some deterioration in the acceleration dynamics of the car (by 5%), which, however, is offset by a slight increase in gas consumption. In addition, the burning time of gas is longer than that of gasoline, and the temperature in the combustion chamber is higher.
How it works
When used as an engine fuel, propane and methane work similarly. The main difference between these gases is that propane is stored in liquid form, while methane is stored in gaseous form. Propane becomes gaseous when it is released from a gas cylinder. Burning one gallon of propane typically releases about 8.4 x 104 BTUs of energy. In America, the GGE ratio is sometimes used to evaluate the efficiency of alternative fuels, equal to the ratio of the energy in BTUs generated by burning one gallon of gasoline to the energy in BTUs, generated by burning one gallon of alternative fuel. The GGE ratio of propane (let's call it Gp) can be determined by the following formula: Gp = (1.25 x 104)/8.4 x 104 =1.5.
The combustion of one gallon of gasoline produces energy equal to approximately 1.25 x 105 Btu, which is 1.5 times the energy that is released by the complete combustion of one gallon of liquid propane. In different countries, this value may vary depending on the type of fuel and the degree of its purification. Economic indicators depend on the price of alternative fuel, the price of gasoline, the efficiency of a gasoline engine, the efficiency of an engine running on alternative fuel.
To compare two fuels based on the GGE 138 factor, you can use not only units of measurement such as gallons and BTUs, but also, for example, liters and joules. Applying this second pair of units to estimate the energy released by propane and gasoline, we get the same value Gp = 1.5, since this is a dimensionless quantity that determines the ratio of two parameters, and its value does not change if both parameters are expressed in the same and the same units of measurement.
Propane-powered vehicles have the same horsepower, speed, and acceleration as methane-powered vehicles.It takes about the same time to fill the tank of a propane engine as it takes to fill the tank of a fossil fuel engine. Most propane-powered vehicles in use today have had conventional gasoline or diesel engines modified. However, some manufacturers are already offering new models of vehicles with propane engines. There are thousands of propane filling stations in the US, but they are not as common as gasoline and diesel filling stations.
Molar mass of propane
Propane CH 3 CH 2 CH 3 It is a colorless, odorless, flammable gas. Propane melting point - 187.69 ° C, boiling point - 42.07 ° C, density at 20 degrees - 0.5005 g / cm 3 (at saturated steam pressure), ignition temperature 465 °, explosive limits in a mixture with air 2 , 1 - 9.5 vol.%, calorific value of gas to liquid water and CO 2 120.34 kcal/kg. ( 25 ° C), heat capacity 17.57 cal/deg. mol.
Propane is found in natural gases, associated gases of oil production and oil refining, for example, in catalytic cracking gases, in coke oven gases, in gases for the synthesis of hydrocarbons from CO and H 2 according to Fischer-Tropsch.
Propane is isolated from industrial gases by: distillation under pressure, low-temperature absorption in solvents under pressure, adsorption with activated carbon, molecular sieves.
Propane forms a hydrate with water 3 H 8 . 6 N 2 O with a critical decomposition temperature of + 8.5 °; decomposes at 1 atm. (0°). According to its chemical properties, propane is close to other lower homologues of the methane series.
Propane dehydrogenation on chromium catalysts at high temperature or in the presence of O 2 and iodine produce propylene. Thermal and photochemical chlorination of propane produces mainly monochloropropanes. Propane mixtures with Cl 2 explosive (explosion limits 8 - 42% C 3 H 8 ).
By mild oxidation of propane, propionic acid, acetaldehyde, and acetic acid are obtained; by nitration at high temperature, nitropropanes, as well as nitroethane and nitromethane, are obtained. When converted from H 2 O at high temperatures on the catalysts get H 2 , CO and CO 2 . Alkylation of propane with ethylene at high temperatures and 300 atm. isopentane is produced. In the presence of peroxides at elevated temperatures and pressure, propane reacts with ethylene chlorine derivatives; with trichlorethylene, for example, one obtains 1,1-dichloro-3-methylbutene-1:
Propane is used as a solvent for the dewaxing and deasphalting of petroleum products, in the polymerization of vinyl esters and for the extraction of fats. Propane is also used to produce soot; with oxygen - for cutting metal. Mixed with bottled butane, propane is widely used as a household gas and as a smokeless fuel for cars.
