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Calorific value of various types of fuel: firewood, coal, pellets, briquettes. Fuel energy

Different types of fuel have different characteristics. This depends on the calorific value and the amount of heat released when the fuel is completely burned out. For example, the relative heat of combustion of hydrogen affects its consumption. Calorific value is determined using tables. They provide comparative analyzes of the consumption of different energy resources.

There is a huge amount of combustibles. each of which has its own pros and cons

Comparison tables

With the help of comparison tables it is possible to explain why different energy resources have different calorific values. For example, such as:

  • electricity;
  • methane;
  • butane;
  • propane-butane;
  • diesel fuel;
  • firewood;
  • peat;
  • coal;
  • mixtures of liquefied gases.

Propane is one of the popular types of fuel

Tables can demonstrate not only, for example, the specific heat of combustion of diesel fuel. Other indicators are also included in the comparative analysis reports: calorific value, volumetric densities of substances, price for one part of conditional power supply, efficiency of heating systems, cost of one kilowatt per hour.

In this video you will learn about how fuel works:

Fuel prices

Thanks to comparative analysis reports, the prospects for using methane or diesel fuel are determined. Gas price in a centralized gas pipeline tends to increase. It may be higher even than diesel fuel. That is why the cost of liquefied petroleum gas will hardly change, and its use will remain the only solution when installing an independent gasification system.

There are several types of names for fuels and lubricants (fuels and lubricants): solid, liquid, gaseous and some other flammable materials, in which, during the heat-generating reaction of oxidation of fuels and lubricants, its chemical heat energy is converted into temperature radiation.

The heat energy released is called the calorific value of various types of fuel during complete combustion of any flammable substance. Its dependence on chemical composition and humidity is the main indicator of nutrition.

Thermal susceptibility

Determination of the GTC of fuel is carried out experimentally or using analytical calculations. The experimental determination of thermal susceptibility is carried out experimentally by establishing the volume of heat released during fuel combustion in a heat store with a thermostat and a combustion bomb.

If necessary, determine the specific heat of combustion of fuel from the table First, calculations are made according to Mendeleev's formulas. There are higher and lower grades of OTC fuel. At the highest relative heat, a large amount of heat is released when any fuel burns out. This takes into account the heat spent on evaporating the water in the fuel.

At the lowest degree of burnout, the TTC is less than at the highest degree, since in this case less evaporation is released. Evaporation occurs from water and hydrogen when fuel burns. To determine the properties of the fuel, engineering calculations take into account the lower relative calorific value, which is an important parameter of the fuel.

The following components are included in the tables of the specific heat of combustion of solid fuels: coal, firewood, peat, coke. They include the values ​​of the GTC of solid flammable material. The names of fuels are entered in the tables alphabetically. Of all solid forms of fuels and lubricants, coking, hard coal, brown and charcoal, as well as anthracite, have the greatest heat transfer capacity. Low productivity fuels include:

  • wood;
  • firewood;
  • powder;
  • peat;
  • combustible shale.

Indicators of alcohol, gasoline, kerosene, and oil are entered in the list of liquid fuels and lubricants. The specific heat of combustion of hydrogen, as well as various forms of fuel, is released with the unconditional combustion of one kilogram, one cubic meter or one liter. Most often, such physical properties are measured in units of work, energy and the amount of heat released.

Depending on the degree to which the OTC of fuel and lubricants is high, this will be its consumption. This competence is the most significant parameter of the fuel, and this must be taken into account when designing boiler installations using different types of fuel. Calorific value depends on humidity and ash content, as well as from flammable ingredients such as carbon, hydrogen, volatile combustible sulfur.

SG (specific heat) of burnout of alcohol and acetone is much lower than classic motor fuel and lubricants and it is equal to 31.4 MJ/kg; for fuel oil this figure ranges from 39-41.7 MJ/kg. The indicator of combustion efficiency of natural gas is 41-49 MJ/kg. One kcal (kilocalorie) is equal to 0.0041868 MJ. The caloric content of different types of fuel differs from each other in terms of burnout. The more heat any substance gives off, the greater its heat transfer. This process is also called heat transfer. Liquids, gases and hard particles take part in heat transfer.

The combustion temperature of coal is considered the main criterion that allows you to avoid mistakes when choosing fuel. The performance of the boiler and its quality work directly depend on this value.

Temperature detection option

In winter, the issue of heating residential premises is especially relevant. Due to the systematic increase in the cost of coolants, people have to look for alternative options for generating thermal energy.

The best way to solve this problem is to select solid fuel boilers that have optimal performance characteristics and retain heat well.

The specific heat of combustion of coal is a physical quantity that shows how much heat can be released during the complete combustion of a kilogram of fuel. In order for the boiler to operate for a long time, it is important to select the correct fuel for it. The specific heat of combustion of coal is high (22 MJ/kg), so this type of fuel is considered optimal for efficient boiler operation.

Characteristics and properties of wood

Currently, there is a tendency to switch from installations based on the gas combustion process to solid fuel heating household systems.

Not everyone knows that creating a comfortable microclimate in the house directly depends on the quality of the chosen fuel. Let us highlight wood as a traditional material used in such heating boilers.

In harsh climatic conditions, characterized by long and cold winters, it is quite difficult to heat a home with wood for the entire heating season. When the air temperature drops sharply, the owner of the boiler is forced to use it to the limit of its maximum capabilities.

When choosing wood as a solid fuel, serious problems and inconveniences arise. First of all, we note that the combustion temperature of coal is much higher than that of wood. Among the disadvantages is the high rate of combustion of firewood, which creates serious difficulties when operating the heating boiler. Its owner is forced to constantly monitor the availability of firewood in the firebox; a fairly large amount of it will be required for the heating season.

Coal options

The combustion temperature is much higher, so this fuel option is an excellent alternative to conventional firewood. We also note the excellent heat transfer rate, the duration of the combustion process, and low fuel consumption. There are several types of coal, related to the specifics of mining, as well as the depth of occurrence in the bowels of the earth: hard, brown, anthracite.

Each of these options has its own distinctive qualities and characteristics that allow it to be used in solid fuel boilers. The combustion temperature of coal in a furnace will be minimal when using brown coal, since it contains a fairly large amount of various impurities. As for heat transfer indicators, their value is similar to wood. The chemical combustion reaction is exothermic, the calorific value of coal is high.

Coal has an ignition temperature of 400 degrees. Moreover, the calorific value of this type of coal is quite high, so this type of fuel is widely used for heating residential premises.

Anthracite has maximum efficiency. Among the disadvantages of such fuel, we highlight its high cost. The combustion temperature of this type of coal reaches 2250 degrees. No solid fuel extracted from the bowels of the earth has such an indicator.

Features of a coal-fired furnace

Such a device has design features that involve the pyrolysis of coal. does not belong to minerals, it has become a product of human activity.

The combustion temperature of coal is 900 degrees, which is accompanied by the release of a sufficient amount of thermal energy. What is the technology to create such an amazing product? The essence lies in a certain processing of wood, due to which a significant change in its structure occurs and excess moisture is released from it. A similar process is carried out in special ovens. The operating principle of such devices is based on the pyrolysis process. A charcoal furnace consists of four basic components:

  • combustion chambers;
  • reinforced foundation;
  • chimney;
  • recycling compartment.

Chemical process

After entering the chamber, gradual smoldering of the firewood occurs. This process occurs due to the presence in the firebox of a sufficient amount of oxygen gas that supports combustion. As the smoldering progresses, a sufficient amount of heat is released and excess liquid is converted into steam.

The smoke released during the reaction goes to the secondary processing compartment, where it burns completely and heat is released. performs several important functional tasks. With its help, charcoal is formed, and a comfortable temperature is maintained in the room.

But the process of obtaining such fuel is quite delicate, and with the slightest delay, complete combustion of the wood is possible. It is necessary to remove charred pieces from the oven at a certain time.

Application of charcoal

If the technological chain is followed, an excellent material is obtained that can be used for full heating of residential premises during the winter heating season. Of course, the combustion temperature of coal will be higher, but such fuel is not affordable in all regions.

Charcoal combustion begins at a temperature of 1250 degrees. For example, a smelting furnace runs on charcoal. The flame that is formed when air is supplied to the furnace easily melts the metal.

Creating optimal conditions for combustion

Due to the high temperature, all internal elements of the furnace are made of special refractory bricks. Fireproof clay is used for their installation. If special conditions are created, it is quite possible to obtain a temperature in the furnace exceeding 2000 degrees. Each type of coal has its own flash point. After reaching this indicator, it is important to maintain the ignition temperature by continuously supplying excess oxygen to the firebox.

Among the disadvantages of this process, we highlight heat loss, because part of the released energy will escape through the pipe. This leads to a decrease in the temperature of the firebox. In the course of experimental studies, scientists were able to establish the optimal excess amount of oxygen for various types of fuel. Thanks to the choice of excess air, you can count on complete combustion of the fuel. As a result, you can count on minimal losses of thermal energy.

Conclusion

The comparative value of a fuel is assessed by its calorific value, measured in calories. Taking into account the characteristics of its different types, we can conclude that hard coal is the optimal type of solid. Many owners of their own heating systems try to use boilers that run on mixed fuel: solid, liquid, gaseous.

Any fuel, when burned, releases heat (energy), quantified in joules or calories (4.3 J = 1 cal). In practice, to measure the amount of heat released during fuel combustion, they use calorimeters - complex laboratory devices. The heat of combustion is also called calorific value.

The amount of heat obtained from burning fuel depends not only on its calorific value, but also on its mass.

To compare substances by the amount of energy released during combustion, the specific heat of combustion is more convenient. It shows the amount of heat generated during the combustion of one kilogram (mass specific heat of combustion) or one liter, cubic meter (volume specific heat of combustion) of fuel.

The units of specific heat of combustion of fuel accepted in the SI system are kcal/kg, MJ/kg, kcal/m³, MJ/m³, as well as their derivatives.

The energy value of the fuel is determined precisely by the value of its specific heat of combustion. The relationship between the amount of heat generated during the combustion of fuel, its mass and specific heat of combustion is expressed by a simple formula:

Q = q m, where Q is the amount of heat in J, q is the specific heat of combustion in J/kg, m is the mass of the substance in kg.

For all types of fuel and most combustible substances, the values ​​of the specific heat of combustion have long been determined and compiled into tables, which are used by specialists when calculating the heat released during the combustion of fuel or other materials. There may be slight discrepancies in different tables, which are obviously explained by slightly different measurement techniques or different calorific values ​​of similar combustible materials extracted from different deposits.

Coal has the highest energy intensity among solid fuels - 27 MJ/kg (anthracite - 28 MJ/kg). Charcoal has similar indicators (27 MJ/kg). Brown coal has a much lower calorific value - 13 MJ/kg. It also usually contains a lot of moisture (up to 60%), which, when evaporated, reduces the total heat of combustion.

Peat burns with a heat of 14-17 MJ/kg (depending on its condition - crumbled, pressed, briquette). Firewood dried to 20% humidity releases from 8 to 15 MJ/kg. At the same time, the amount of energy received from aspen and birch can vary almost twice. Pellets from different materials give approximately the same indicators - from 14 to 18 MJ/kg.

Liquid fuels differ much less in their specific heat of combustion than solid fuels. Thus, the specific heat of combustion of diesel fuel is 43 MJ/l, gasoline - 44 MJ/l, kerosene - 43.5 MJ/l, fuel oil - 40.6 MJ/l.

The specific heat of combustion of natural gas is 33.5 MJ/m³, propane - 45 MJ/m³. The most energy-intensive gaseous fuel is hydrogen gas (120 MJ/m³). It is very promising for use as fuel, but to date no optimal options for its storage and transportation have been found.

Comparison of energy intensity of different types of fuel


When comparing the energy value of the main types of solid, liquid and gaseous fuels, it can be established that one liter of gasoline or diesel fuel corresponds to 1.3 m³ of natural gas, one kilogram of coal - 0.8 m³ of gas, one kg of firewood - 0.4 m³ of gas.

The heat of combustion of a fuel is the most important indicator of efficiency, but the breadth of its distribution in areas of human activity depends on the technical capabilities and economic indicators of use.

    specific heat of combustion- specific heat capacity - Topics oil and gas industry Synonyms specific heat capacity EN specific heat ...

    The amount of heat released during complete combustion of 1 kg of fuel. The specific heat of combustion of fuel is determined experimentally and is the most important characteristic of fuel. See also: Fuel Financial Dictionary Finam... Financial Dictionary

    specific heat of combustion of peat by bomb- Higher heat of combustion of peat, taking into account the heat of formation and dissolution of sulfuric and nitric acids in water. [GOST 21123 85] Inadmissible, not recommended calorific value of peat for a bomb Topics peat General terms properties of peat EN ... ... Technical Translator's Guide

    specific heat of combustion (fuel)- 3.1.19 specific heat of combustion (fuel): The total amount of energy released under regulated conditions of fuel combustion. Source …

    Specific heat of combustion of peat by bomb- 122. Specific heat of combustion of peat by bomb Higher heat of combustion of peat taking into account the heat of formation and dissolution of sulfuric and nitric acids in water Source: GOST 21123 85: Peat. Terms and definitions original document... Dictionary-reference book of terms of normative and technical documentation

    specific heat of combustion of fuel- 35 specific heat of combustion of fuel: The total amount of energy released under specified conditions of fuel combustion. Source: GOST R 53905 2010: Energy saving. Terms and definitions original document... Dictionary-reference book of terms of normative and technical documentation

    This is the amount of heat released during complete combustion of a mass (for solid and liquid substances) or volumetric (for gaseous) unit of a substance. Measured in joules or calories. Heat of combustion per unit mass or volume of fuel, ... ... Wikipedia

    Modern encyclopedia

    Heat of combustion- (heat of combustion, calorie content), the amount of heat released during complete combustion of fuel. There are specific heats of combustion, volumetric heats, etc. For example, the specific heat of combustion of coal is 28 34 MJ/kg, gasoline is about 44 MJ/kg; volumetric... ... Illustrated Encyclopedic Dictionary

    Specific heat of combustion of fuel- Specific heat of combustion of a fuel: the total amount of energy released under specified combustion conditions...

Thermal machines in thermodynamics, these are periodically operating heat engines and refrigeration machines (thermocompressors). A type of refrigeration machine is heat pump.

Devices that perform mechanical work using the internal energy of fuel are called heat engines (heat engines). For the operation of a heat engine, the following components are required: 1) a heat source with a higher temperature level t1, 2) a heat source with a lower temperature level t2, 3) a working fluid. In other words: any heat engines (heat engines) consist of heater, refrigerator and working fluid .

As working fluid gas or steam are used, since they are well compressed, and depending on the type of engine, there may be fuel (gasoline, kerosene), water vapor, etc. The heater transfers a certain amount of heat (Q1) to the working fluid, and its internal energy increases due to this internal energy, mechanical work (A) is performed, then the working fluid gives off a certain amount of heat to the refrigerator (Q2) and is cooled to the initial temperature. The described diagram represents the engine operating cycle and is general; in real engines, the role of a heater and a refrigerator can be performed by various devices. The environment can serve as a refrigerator.

Since in the engine part of the energy of the working fluid is transferred to the refrigerator, it is clear that not all the energy it receives from the heater is used to perform work. Respectively, efficiency engine (efficiency) is equal to the ratio of the work done (A) to the amount of heat it receives from the heater (Q1):

Internal combustion engine (ICE)

There are two types of internal combustion engines (ICE): carburetor And diesel. In a carburetor engine, the working mixture (a mixture of fuel and air) is prepared outside the engine in a special device and from it enters the engine. In a diesel engine, the fuel mixture is prepared in the engine itself.

ICE consists of cylinder , in which it moves piston ; there are in the cylinder two valves , through one of which the combustible mixture is admitted into the cylinder, and through the other, exhaust gases are discharged from the cylinder. Piston using crank mechanism connects with crankshaft , which begins to rotate with the translational movement of the piston. The cylinder is closed with a lid.

The internal combustion engine operating cycle includes four bars: intake, compression, stroke, exhaust. During intake, the piston moves down, the pressure in the cylinder decreases, and a combustible mixture (in a carburetor engine) or air (in a diesel engine) enters it through the valve. The valve is closed at this time. At the end of the intake of the combustible mixture, the valve closes.

During the second stroke, the piston moves up, the valves are closed, and the working mixture or air is compressed. At the same time, the gas temperature rises: the combustible mixture in a carburetor engine heats up to 300-350 °C, and the air in a diesel engine - up to 500-600 °C. At the end of the compression stroke, a spark jumps in the carburetor engine and the combustible mixture ignites. In a diesel engine, fuel is injected into the cylinder and the resulting mixture spontaneously ignites.

When a combustible mixture is burned, the gas expands and pushes the piston and the crankshaft connected to it, performing mechanical work. This causes the gas to cool.

When the piston reaches the lowest point, the pressure in it will decrease. When the piston moves upward, the valve opens and exhaust gas is released. At the end of this stroke the valve closes.


Steam turbine

Steam turbine It is a disk mounted on a shaft on which the blades are mounted. Steam enters the blades. Steam heated to 600 °C is directed into the nozzle and expands in it. When steam expands, its internal energy is converted into kinetic energy of the directed movement of the steam jet. A jet of steam comes from the nozzle onto the turbine blades and transfers part of its kinetic energy to them, causing the turbine to rotate. Typically, turbines have several disks, each of which transfers part of the steam energy. The rotation of the disk is transmitted to a shaft to which an electric current generator is connected.

When different fuels of the same mass are burned, different amounts of heat are released. For example, it is well known that natural gas is an energy-efficient fuel than wood. This means that to obtain the same amount of heat, the mass of wood that needs to be burned must be significantly greater than the mass of natural gas. Consequently, different types of fuel from an energy point of view are characterized by a quantity called specific heat of combustion of fuel .

Specific heat of combustion of fuel- a physical quantity showing how much heat is released during complete combustion of fuel weighing 1 kg.