﻿The calorific value of various fuels: a comparative overview of the fuel in terms of calorific value

# The calorific value of different types of fuel: a comparison of fuel by calorific value + table of calorific value

Checked by a specialist: Vasily Borutsky
Author: Oleg Sysoev
Last update: June 2019

When a certain amount of fuel burns out, a measurable amount of heat is released. According to the International System of Units, the value is expressed in Joules per kg or m3. But the parameters can be calculated in kcal or kW. If the value is related to the unit of fuel, it is called specific.

What affects the calorific value of various fuels? What is the value of the indicator for liquid, solid and gaseous substances? Answers to these questions are detailed in the article. In addition, we have prepared a table showing the specific heat of combustion of materials - this information is useful when choosing a high-energy type of fuel.

## General information on calorific value

The energy release during combustion should be characterized by two parameters: high efficiency and the absence of the production of harmful substances.

Artificial fuel is obtained in the process of processing natural - biofuel. Regardless of the state of aggregation, the substances in their chemical composition have a combustible and non-combustible part. The first is carbon and hydrogen. The second consists of water, mineral salts, nitrogen, oxygen, metals.

According to the state of aggregation, fuel is divided into liquid, solid and gas. Each group additionally branches into a natural and artificial subgroup (+)

When 1 kg of such a “mixture” is burned, a different amount of energy is released. How much of this particular energy will be released depends on the proportions of these elements - the combustible part, humidity, ash content and other components.

The heat of combustion of fuel (TST) is formed from two levels - the highest and the lowest. The first indicator is obtained due to condensation of water, in the second this factor is not taken into account.

Lower TST is needed for calculating the need for fuel and its cost, with the help of such indicators heat balances are compiled and the efficiency of fuel-powered plants is determined.

TST can be calculated analytically or experimentally.If the chemical composition of the fuel is known, the Mendeleev formula is used. Experimental techniques are based on the actual measurement of heat during fuel combustion.

In these cases, a special burning bomb is used - a calorimetric bomb along with a calorimeter and a thermostat.

Features of the calculations are individual for each type of fuel. Example: TST in internal combustion engines is calculated from the lowest value, because the liquid does not condense in the cylinders.

TST is set using a calorimeter bomb. Compressed oxygen is saturated with water vapor. A sample of fuel is placed in such an environment and results

Each type of substance has its own TST due to its chemical composition. The values ​​vary significantly, the range of fluctuations is 1 000-10 000 kcal / kg.

Comparing different types of materials, the concept of conventional fuel is used; it is characterized by a lower TST of 29 MJ / kg.

## Calorific value of solid materials

This category includes wood, peat, coke, oil shale, briquette and pulverized fuel. The bulk of solid fuel is carbon.

### Features of different species of wood

The maximum efficiency from the use of firewood is achieved if two conditions are met - dry wood and a slow burning process.

Sliced ​​pieces of wood or cut into pieces up to 25-30 cm long so that the firewood is conveniently loaded into the furnace

Ideal for wood stove heating Oak, birch, ash blocks are considered. Good performance is characterized by hawthorn, hazel. But in conifers, the calorific value is low, but the burning rate is high.

How different breeds burn:

1. Beech, birch, ash, hazel difficult to melt, but they can burn raw due to their low moisture content.
2. Alder with aspen they do not form soot and “know how” to remove it from the chimney.
3. Birch tree It requires a sufficient amount of air in the furnace, otherwise it will smoke and settle with resin on the walls of the pipe.
4. Pine contains more resin than spruce, so it sparks and burns hotter.
5. Pear and apple tree it breaks more easily and burns perfectly.
6. Cedar gradually turns into smoldering coal.
7. Cherry and Elm smokes, and the plane tree is difficult to split.
8. Linden tree with poplar burn out quickly.

TST indices of different breeds strongly depend on the density of specific breeds. 1 cubic meter of firewood is equivalent to approximately 200 liters of liquid fuel and 200 m3 natural gas. Wood and firewood are low energy efficient.

### The effect of age on the properties of coal

Coal is a natural material of plant origin. It is extracted from sedimentary rocks. This fuel contains carbon and other chemical elements.

In addition to the type, the age of the material also affects the calorific value of coal. Brown belongs to the young category, followed by stone, and the oldest is considered anthracite.

Humidity is also determined by the age of the fuel: the younger the coal, the greater the moisture content in it. Which also affects the properties of this type of fuel.

The process of burning coal is accompanied by the release of substances polluting the environment, while the grate of the boiler is covered with slag. Another adverse factor for the atmosphere is the presence of sulfur in the fuel. This element in contact with air is transformed into sulfuric acid.

Manufacturers manage to minimize the sulfur content in coal. As a result, TJT differs even within the same species. Affects the performance and geography of production. As solid fuel, not only pure coal, but also briquetted slag can be used.

The greatest fuel ability is observed in coking coal. Stone, wood, lignite, and anthracite also have good characteristics.

### Characteristics of pellets and briquettes

This solid fuel is manufactured industrially from various wood and vegetable debris.

Shredded chips, bark, cardboard, straw are dried and with special equipment turns into granules. In order for the mass to acquire a certain degree of viscosity, a polymer - lignin is added to it.

Pellets differ in reasonable cost, which is influenced by high demand and features of the manufacturing process. This material can only be used in boilers designed for this type of fuel.

Briquettes differ only in shape, they can be loaded into ovens, boilers. Both types of fuel are divided into types of raw materials: from round logs, peat, sunflower, straw.

At pellets and briquettes There are significant advantages over other types of fuel:

• full environmental friendliness;
• the ability to store in almost any environment;
• resistance to mechanical stress and fungus;
• uniform and long burning;

Sustainable fuels are a good alternative to traditional heat sources that are not renewable and adversely affect the environment. But pellets and briquettes are characterized by increased fire hazard, which should be taken into account when organizing a storage location.

If you wish, you can arrange the production of fuel briquettes with your own hands, more details - in this article.

## Liquid Parameters

Liquid materials, like solid ones, are decomposed into the following components: carbon, hydrogen, sulfur, oxygen, nitrogen. The percentage is expressed by weight.

From oxygen and nitrogen, internal organic fuel ballast is formed, these components do not burn and are included in the composition conditionally. External ballast is formed from moisture and ash.

High specific heat of combustion is observed in gasoline. Depending on the brand, it is 43-44 MJ.

Similar specific heat values ​​of combustion are also determined for aviation kerosene - 42.9 MJ. In terms of calorific value, diesel fuel also falls into the category of leaders - 43.4-43.6 MJ.

Since gasoline has more TST than diesel fuel, it should have higher consumption and efficiency. But diesel fuel is 30-40% more economical than gasoline

Relatively low TST values ​​are characterized by liquid rocket fuel, ethylene glycol. The minimum specific heat of combustion is distinguished by alcohol and acetone. Their performance is significantly lower than that of traditional motor fuels.

## Gaseous fuel properties

Gaseous fuel is composed of carbon monoxide, hydrogen, methane, ethane, propane, butane, ethylene, benzene, hydrogen sulfide and other components. These indicators are expressed as a percentage by volume.

The greatest heat of combustion is hydrogen. Burning, a kilogram of substance emits 119.83 MJ of heat. But it is characterized by a high degree of explosion hazard.

High calorific values ​​are also observed in natural gas.

They are equal to 41-49 MJ per kg. But, for example, pure methane has a calorific value of more than 50 MJ per kg.

## Comparison Chart

The table shows the values ​​of the mass specific heat of combustion of liquid, solid, gaseous types of fuel.

 Type of fuel Units rev. Specific heat of combustion MJ kw kcal Firewood: oak, birch, ash, beech, hornbeam kg 15 4,2 2500 Firewood: larch, pine, spruce kg 15,5 4,3 2500 Brown coal kg 12,98 3,6 3100 Coal kg 27,00 7,5 6450 Charcoal kg 27,26 7,5 6510 Anthracite kg 28,05 7,8 6700 Wood Pellet kg 17,17 4,7 4110 Straw pellet kg 14,51 4,0 3465 Sunflower pellet kg 18,09 5,0 4320 Sawdust kg 8,37 2,3 2000 Paper kg 16,62 4,6 3970 Vine kg 14,00 3,9 3345 Natural gas m3 33,5 9,3 8000 LPG kg 45,20 12,5 10800 Petrol kg 44,00 12,2 10500 Diz. fuel kg 43,12 11,9 10300 Methane m3 50,03 13,8 11950 Hydrogen m3 120 33,2 28700 Kerosene kg 43.50 12 10400 Fuel oil kg 40,61 11,2 9700 Oil kg 44,00 12,2 10500 Propane m3 45,57 12,6 10885 Ethylene m3 48,02 13,3 11470

From the table it can be seen that the highest TST indicators of all substances, and not just from gaseous ones, have hydrogen. It refers to high-energy fuels.

The product of hydrogen combustion is ordinary water. In the process, furnace waste, ash, carbon monoxide and carbon dioxide are not emitted, which makes the substance environmentally friendly fuel.But it is explosive and has a low density, so this fuel is difficult to liquefy and transported.

## Conclusions and useful video on the topic

About the calorific value of different species of wood. Comparison of indicators per m3 and kg

TST is the most important thermal and operational characteristic of fuel. This indicator is used in various fields of human activity: heat engines, power plants, industry, when heating homes and cooking.

Calorific values ​​help to compare different types of fuel according to the degree of energy released, calculate the required mass of fuel, save on costs.

Is there anything to supplement, or have questions about the calorific value of different types of fuel? You can leave comments on the publication and participate in discussions - the contact form is in the bottom block.

No (7)
Yes (36)
1. Alice

Yes ... maybe we will live to see hydrogen boilers becoming commonplace - a dream!
Of course, drowning with main gas is the best option, but, unfortunately, in our vast country it is not accessible to everyone. And if you choose between coal and pellets, I choose pellets. Coal also emits a lot of harmful substances in the combustion process, and then slag needs to be put somewhere else. And the whole country pours it on the road in winter, and then breathes carcinogenic dust in spring, and then wonders why it is so sick.
Ashes from pellets can be fertilized garden, well, or a lawn - whoever has what.

2. Alexander

The best firewood comes from deciduous trees - oak, birch. Of birch, the most versatile and popular firewood is that it gives enough temperature, burns evenly, without a lot of smoke. Oak gives the most heat when compared with trees growing in our country. Aspen is good for clearing a chimney. I do not recommend drowning with conifers - because of the resins they give a lot of smoke.

• Val42

I think it’s extremely unprofitable now to heat only with wood. The only where applicable is the bathhouse. And if we take the heating of a village house, then coal, whoever says anything, is still ahead of all types of fuel, with the exception of main gas. Gas in cylinders, gas holder, firewood, pellets, briquettes - all have cons. Somewhere a high price, somewhere a bureaucracy with a bunch of permits and passing checks. And in coal, I do not see any significant minuses. Of course, someday gasification is not in words, but in fact it will reach our villages and the relevance of coal will decrease, but it will not be soon.

3. Steepan

For gasoline, diesel fuel, oil, kerosene ... data on KGS 😉

• Expert
Vasily Borutsky
Expert

Yes, thanks, thanks! Corrected.

4. Leonid

In the table, kcal is energy and kW is power. For example, 2500 kcal is 2.9075 kWh. Or am I wrong?