Gaseous fuels have been known since the mid-19th century. It was then that the famous engineer Lenoir built his first gas internal combustion engine. This device was primitive and worked without preliminary compression of the combustion chamber. Modern engines can not be compared with him. Today, the use of gaseous fuels is not limited to automobiles. This eco-friendly, cheap and affordable type of fuel is actively conquering more and more niches and is actively used in all sectors of the economy. This article describes the characteristics of the fuel. In general terms, the methods of their production and application are described.
General information
Gaseous fuel refers to a substance that is flammable. This quality and useful property is applied in various branches of science and technology. For example, more and more often the population and industry use gas-fired boilers. Carbon oxides (carbon dioxide), carbon dioxide vapors, as well as elements such as nitrogen, hydrogen, oxygen and other impurities may be present in various quantities in this fuel. Modern devices operating on gaseous fuels are very sensitive to the chemical composition of the working gas. If it does not comply with the standards recommended by the manufacturer, then the equipment is likely to fail and require expensive repairs.
All substances that make up the gases can be divided into combustible and non-combustible. The first, in addition to methane, are ethane, propane and butane. Explosive and, accordingly, combustible are carbon monoxide and hydrogen. Hydrogen is especially dangerous. For this reason, it is not recommended to store it in gas cylinders. The best solution is to purchase a hydrogen generator. This device releases hydrogen from distilled water as needed. Thus, the threat of detonation of a large volume of gas is eliminated.
The state is a monopolist in the wholesale trade of liquid and gaseous fuels. This indicates the strategic importance of this type of raw material.
Fuel classification by origin
Like liquid, gaseous fuels can be mined as minerals, and can be produced under artificial conditions. In the first case, such fuel is called natural, and in the second - artificial.
Specialists recorded differences in the composition of liquid and gaseous fuels produced from different regions. Due to differences in chemical composition, slight differences arise in the amount of heat generated during combustion. Natural gaseous fuel is almost completely (95-99%, depending on the field) consists of so-called methane (chemical formula - CH 4 ). Such fuel is called natural gas. And this is the cheapest source of energy today. It is for this reason that this type of energy is actively used in all sectors of the economy. However, all the advantages are overshadowed by the low level of safety of gaseous fuel vehicles. The media regularly receive disturbing news about accidents and human casualties as a result of violation of the rules of operation of gas installations.
The artificial types of gaseous fuels include substances obtained from the processing of solid or liquid fuels. Its most common and popular types are coke cracking gases. This group can also include luminous, water and mixed fuels. Depending on the chemical composition of a particular gas, the level of heat release during combustion varies over a wide range. Such substances are particularly explosive. For this reason, it is recommended to mix them with natural gas before burning. This measure increases the safety of the operation of gas-fired vehicles by an order of magnitude. These manipulations are carried out on specially equipped bases. Then, such gas is supplied to the end user in cylinders or otherwise. But despite the fact that such a mixture is less dangerous, it must nevertheless be handled with extreme care, in compliance with all norms and rules of working with pressure vessels and safety precautions. And this is not the only danger. This substance is toxic, and inhalation can cause serious consequences and even death.
Destination classification
Gaseous fuel is used both in thermal installations and in internal combustion engines. Accordingly, on this basis, it can be divided into motor fuel and boiler-furnace fuel.
Natural gas is traditionally used as boiler fuel . In rare cases, use artificial fuel. The same type of fuel, with only a few additives, is also used for refueling cars.
Natural gas description
It is difficult to overestimate the importance of this mineral for the economy of our state and the economic development of the world as a whole. Many cars, gaseous fuel boilers, power plants and combined heat and power plants use it. Based on the projected prices for blue fuel (as natural gas is sometimes called), state budgets are being imposed.
More than 90% of this gas consists of methane molecules (CH 4 ). In addition to methane, natural gas also contains butane with propane, nitrogen, carbon dioxide, water vapor and other impurities (they are considered harmful). In small quantities, natural gas also contains inert gases (helium and others). It is believed that the latter have a beneficial effect on machines, devices and mechanisms operating on gas, as well as improve the physics of fuel combustion processes. The suitability of the fuel for use, its quality is judged by the percentage of hydrocarbon components.
Natural gas is not only a valuable type of fuel, but also a raw material for a number of industries. So, from the methane that it contains, large chemical plants produce hydrogen. For such a reaction to occur, it must be oxidized. In addition to hydrogen, acetylene is produced from it. All kinds of aldehydes, methyl alcohol (a very toxic and dangerous substance), ammonia, acetone, acetic acid and so on are produced on the basis of these substances. However, the fact remains that the main field of application of natural gas is the combustion of gaseous fuels with the goal of various drive mechanisms (machine engines) and boiler plants.
The main properties of gases
All gases (not only fuel) are united by a relatively insignificant indicator of density. For the natural gas under consideration and its artificial analogues, its value is kept in the region of 0.8 kilograms per cubic meter. The density of liquefied gaseous fuel is slightly higher and is approximately 2.3 kilograms per cubic meter.
Gases are mostly toxic substances. Toxicity increases with increasing content of carbon oxides and sulfur compounds with hydrogen in the gas. With the content of one or more percent of the described harmful gases in the atmosphere, in three minutes a person will inhale a lethal dose of a poisonous substance.
The gases in question are explosive. Moreover, with an increase in the percentage of carbon monoxide and hydrogen, the danger of detonation increases. An interesting feature: when the content of these substances is more than 74%, the probability of gas detonation is practically zero.
Key fuel characteristics
In a comparative analysis of a particular type of fuel, experts operate on the following concepts: fuel moisture, sulfur content, ash (residue), emitted heat of combustion and heat production.
Heat production refers to a temperature sufficient for the combustion process with a minimum oxygen content. At the same time, additional heating of neither air nor the combustible mixture is carried out.
The solid residue of the fuel combustion field is called ash. She can no longer burn. Slag is the same ash, only after reflow. The formation of this substance negatively affects the operation of the entire system, clogs the fuel equipment. Therefore, this indicator is important to consider when designing.
An important indicator is moisture. It negatively affects the characteristics of the fuel. Its presence causes an increase in exhaust emissions, a decrease in the efficiency of the installation.
The products of combustion of sulfur and its compounds cause and activate corrosion processes on the surfaces of the steel parts of engines and exhaust systems. In addition, they have a negative impact on the environment and human health. Therefore, this indicator is also very important to consider.
Calorific value is a very important characteristic. It is taken into account in the calculation and design of equipment and allows you to determine fuel consumption. This value is determined experimentally. For these purposes, a special calorimeter is used. A known quantity (mass) of fuel is burned and a change in the water temperature of the calorimeter is recorded. Further, it is enough to substitute the obtained information into the formula and calculate the calorific value.
Associated gas
If natural gas is produced from boreholes, then associated gas is a by-product of oil production. The methane content in such a gas is slightly lower than in traditional natural gas. However, the combustion of gaseous fuels produces comparable heat.
Side gas (associated) is also produced by metallurgical plants. At these facilities, fuel is emitted in stoves. These are the so-called coke oven and blast furnace gases. Typically, these gases are burned locally (fed to the furnace or boiler station). A similar by-product is produced in deep mines, which often leads to disasters.
Dry gas distillation
Artificial gas is obtained by additional processing of solid (liquid) fuel. In this way, the so-called generator gas and dry distillation gas can be obtained.
During dry distillation, fuel decomposes under the influence of high temperatures. In this case, it is necessary to exclude the access of the oxidizing agent (air). After a series of steps, the starting fuel decomposes into the actual gas, resin and coke compounds. The exact composition of the products formed depends on the initial composition of the fuel and the process conditions (primarily on temperature).
The distillation process, which takes place at high temperatures (in the region of 1000 - 1100 degrees Celsius), is called coking. In this case, the decomposition products are actually gas (coke oven) and coke. The density and heat of combustion of the obtained gas are relatively low (0.5 kilograms per meter per cubic meter and 16,000 kilojoules per meter cubic, respectively). One ton of coal in this treatment is converted to 350 cubic meters of gas. This indicator may vary and depends on the process conditions and on the chemical composition and origin of the feedstock (coal).
There is also a low-temperature dry distillation. It consists in processing solid fuel with temperatures in the region of 500 degrees Celsius. Gas with this method produces a minimum amount (not more than 30 meters cubic from one ton of raw materials). The main product in this case is resin, which is further used in the production of motor oils and fuels.
Gas production by gasification of solid fuel
One of the common methods for producing gaseous fuels is the so-called gasification. It consists in the chemical-thermal treatment of solid fuels (combined exposure to high temperatures and chemical treatment). Atoms of carbon contained in solid fuels interact and react with water and steam to form a gas (fuel). In the process of gasification, dry distillation also proceeds. A gas generator is a device for the gasification of solid fuels (primarily coal). This device produces the following substances: methane, hydrogen and carbon monoxide. In addition to the voiced gases, non-combustible substances are also produced (carbon dioxide, oxygen with nitrogen, and water vapor).
Designs of gas generators - a huge variety. The layout and list of nodes depends primarily on the type of feedstock. In general, it is a cylinder with metal walls. It has openings for ventilation (air intake) and for the output of the produced gas. Air supply is forced, using powerful fans. The design should include a hatch for the operator. Fuel is loaded through the roof. Thus, outwardly this unit painfully reminds everyone of the well-known "potbelly stove". However, there is one difference - the lack of a chimney.
The gas generator is only the basis of the entire installation, the core, so to speak. If you look at the schemes of such equipment, it will become clear that all the other components and devices are designed to bring the gas to its normal state (cleaning, cooling, and so on).
Benefits of using and using gas
The composition of gaseous fuels makes it possible to effectively use it as an alternative to traditional gasoline, fuel oil and diesel. Oil reserves are depleted. According to experts, it will last for several decades. Gas reserves are much greater. Thus, the active introduction and use of gas equipment in all sectors of the national economy will allow, if not solve, then at least postpone the acute problem of hydrocarbon deficiency.
The second, and very important advantage is the relative purity of the gas combustion products in comparison with the exhausts of gasoline units. In other words, gaseous fuel powered vehicles are more environmentally friendly and do not pollute the environment so much. In megacities and large cities, this problem is especially acute. Therefore, the authorities are striving to transfer the entire fleet of urban public transport to new environmental standards.
The third advantage is the ability to adjust the engine to personal needs and preferences, by adjusting the composition of the mixture. In the future, this will allow not to overpay the extra money.
A fourth advantage is to increase the useful life of the engine and increase the time between the complete replacement of engine oil. After all, gas, unlike petroleum products, does not remove grease (oil) from the surfaces of the rubbing parts of the mechanism (engine).
Fifth, the gas mixture has a much greater detonation ability compared to traditional fuels. This can significantly increase the engine power of the vehicle.
Sixth - unlike solid and liquid, gaseous fuels do not need to be heated before injection. This positively affects both the reliability of the entire system, and all performance indicators without exception.
Seventh advantage: with the use of gas, the injection into the cylinders becomes more uniform. Thus, the smoothness of the stroke and the operation of the driving mechanisms is increased, and the wear of highly loaded parts is reduced.
Unfortunately, far from always all the described advantages are achieved. Most often, vehicle owners convert gas engines to gas fuel in order to save money on the difference in fuel costs. However, the engine was designed for gasoline or diesel. Hence the not very coordinated work of all parts. Engineers calculated that when switching a car from gas to gas, the engine loses about 20 percent of its power. To compensate for the loss, many owners increase the compression ratio of the combustion chamber space. This significantly reduces engine life. Another measure is the installation of a turbocharging system. But significant money will have to be invested in this event. The operation of the engine or boiler room on liquid and gaseous fuels demonstrates completely different performance indicators. Moreover, the advantage is far not on the side of solid fuels.