To meet their energy demands, more and more companies, commercial groups and households are becoming wood pellet-oriented consumers. Pellet transition tendencies gain in their popularity as pellet fuel is a more sustainable source of energy than fossil ones. RICHI Machinery makes detailed analysis of wood pellet output rates to find out the cost and energy efficiencies of wood fuel in comparison with coal fuel to prove their cost-effectiveness.
Biomass particles vs coal, which one is better for fuel
Wood pellets are good candidates to change coal combustion, which is considered to be of high environmental influence having great emissions of the greenhouse gas. In comparison, wood pellets are considered to be carbon neutral fuel with relatively high output rates as compared to its counterparts. According to the information provided by Richi Machinery, the energy outputs of wood pellets and coal do not differ considerably. The energy content highly depends on the content of moisture in the fuel, thus, wood pellets of high quality with relatively small moisture content rates, approximately 8-10% per unit, will show the efficiency of 19 Gj per tonne. At the same time, coal with no moisture content can produce 24.8 Gj per tonne. Being relatively cheap, the sustainability properties of charcoal are much poorer than those of wood pellets. That is why a lot of big power stations, for example Drax, switch to wood pellets preferring them to the more environmentally unfriendly coal. Moreover, Drax will not only be ecologically cleaner, but the conversion will play a vital role in the future success of the power station. CPF or so called carbon price floor introduced by the government of the United Kingdom has significantly increased the prices for the fossil fuel for electrical power generation. Hence, at the beginning the price for coal had been £0.44 ($0.75) per gigajoule, but rapidly increased up to £1.63 ($1.77) in 2016. That makes the combustion of coal very challenging in terms of economical efficiency.
Theoretically speaking, the thermal value of biomass pellets is 10% lower than the thermal value of coal. But in actually working situation, biomass pellets can be fully burned, and on the contrary, coal normally can not be fully burned, there are always 10%-15% combustible components in the combustion residues of coal. Therefore, in actual using situation, the thermal value of biomass pellet and coal are equal.
The ignition time of biomass pellets is much lower than coal. Biomass pellets is made of biomass materials such as wood shavings, wheat straw, etc. Coal is a kind of combustible organic rocks. Biomass pellets are much easier to ignite than coal, which means the start up time of the boiler is shortened by using biomass pellets.
Comparison of Combustion Performance of Biomass Pellet & Coal
The solid waste of biomass pellets is much lower than the solid waste of coal, which lower the slag discharge fee and the pollution of the environment. The solid waste of biomass pellets are ashes, the weight of biomass pellet solid wastes are about 0.4%-7% of the total biomass pellet weight. The solid waste of coal is the mixture of ash, alkali and residual coal, the weight of coal solid wastes are about25%-40% of the total coal weight.
Coal is one of the main sources of pollution to the atmosphere. There are a large quantity of granular carbon and toxic corrosive gas such as SO2 and CO. And the corrosive gas will cause the corrosion problem of the boilers, too. The main component of biomass pellets is C-H organism, there are no granular carbon in the smoke from burning biomass pellets. The smoke from burning biomass pellets are mainly C-H volatile gas, the discharge of SO2 and CO is nearly zero. The smoke color from burning biomass pellets is lower than Ringelman emittance Grade one. Using biomass pellets can significantly reduce the carbon dioxide emissions which helps protect the environment. Biomass pellets is known as “the clean fuel” around the world.
Using biomass pellets as the fuel of industrial boilers is cheaper than using coal. Moreover, it can also save time by using biomass pellets. Take a 0.5 ton boiler as an example, if we use biomass pellets as the fuel, the cost is 11% lower than the cost of using coal, and the time is 34% lower than the time of using coal.
The continuous combustion time of biomass pellets is 8-10 times compare to the loose biomass materials, which is definitely enough for the continuous combustion of industrial boilers.
1. Burn out rate comparison of biomass pellets and fire coal. Biomass pellet fuel has low density, loose texture and is easy to burn out. The density of coal is higher than that of biomass pellet fuel, which results in less residual heat of biomass pellet fuel than that of coal-fired carbon. Therefore, biomass pellet fuel burns more fully and has a higher utilization rate.
2. Sulphur content comparison of biomass pellets and fire coal. The sulfur content of biomass pellet fuel is only 0.02%-0.12%, while the sulfur content of coal combustion is generally 0.5%-6%. So biomass pellet fuel is more environmentally friendly than coal, and there is no need to install desulfurization device.
3. Calorific value comparison of biomass pellets and fire coal. The carbon content of biomass pellet fuel is less, the highest carbon content of biomass pellet fuel is only about 50%, and the oxygen content of biomass pellet fuel is higher than that of fire coal, so the calorific value of biomass pellet fuel is lower than that of coal combustion.
Ten Contrasts between Biomass Pellets and Fire Coal
4. Ignition comparison of biomass pellets and fire coal. The hydrogen content in biomass pellet fuel is slightly higher, resulting in higher volatile matter. The carbon in biomass pellet fuel combines with hydrogen to form hydrocarbons with low molecular weight. After decomposition at a certain temperature, volatile matter is released. Therefore, biomass pellet fuel is easier to ignite than fire coal.
5. CO2 emissions comparison of biomass pellets and fire coal. The carbon dioxide emission of biomass pellet fuel is almost zero, while that of power plant boilers range from 2.36 to 2.37 tons of carbon dioxide per ton of coal, and that of industrial boilers is 2.6 tons of carbon dioxide per ton of coal. So biomass pellet fuel emits less carbon dioxide harmful gases than fire coal.
6. Ash and slag utilization situation comparison of biomass pellets and fire coal. The ash after burning biomass pellet fuel is a kind of high potassium fertilizer, which can make chemical fertilizer and realize the recycling of waste, while coal-burning cinder brings more hydrological and land pollution. So biomass pellet fuel has better ash and slag utilization than after coal combustion.
7. Combustion carrier comparison of biomass pellets and fire coal. In principle, biomass boilers specially designed for biomass pellet fuel can burn coal with higher combustion efficiency and lower emissions. Coal-fired boilers are generally backward in design and can not burn biomass pellet fuel without retrofitting. Moreover, the retrofitted coal-fired boilers have poor combustion efficiency and low utilization rate of biomass pellet fuel.
8. Comparison of thermal efficiency utilization of biomass pellet fuel and coal-fired boiler. The thermal efficiency of biomass pellet fuel boilers is as high as 85%, and that of coal-fired boilers is generally 65%. Therefore, coal-fired boilers waste more resources and have low utilization rate.
9. Price comparison of biomass pellets and fire coal. The price of biomass pellet fuel is lower than that of high-quality anthracite and sulfur-less coal, and the price of biomass pellet fuel is higher than that of low-quality coal. Comparing the comprehensive cost, the operating cost of biomass pellet fuel is almost the same as that of coal combustion.
10. Biomass pellet fuel combustion belongs to waste utilization, realizing resource recycling, and is harmless to environmental protection, while coal combustion brings more waste pollution and air pollution.
In order to confirm the economic and combustion performance of biomass pellets, we have compare the environmental protection property, heat value, boiler thermal efficiency, fuel consumption quantity, fuel price and operation cost of biomass pellets and other fuels. The boiler we used for the test is a one ton boiler, and the fuel price and operation cost is based on Chinese market. The result of this test has been placed in the following table. Hopefully, this contrast can help you get a visual understanding of biomass pellet fuel.
|Fuel||environmental protection property||heat value||boiler thermal efficiency||consumption quantity||price||operation cost|
|heavy oil||heavy pollution||8000kcal/kg||85%||88.8kg/h||¥4.70/kg||¥417/h|
|natural gas||pollution free||8000kcal/m²||86%||87kg/m³||¥4.50/m³||¥391.5/h|
|biomass pellet||pollution free||4200kcal/kg||81%||178kg/h||¥1.10/kg||¥195/h|
More and more industrial energy companies convert their basic source of energy in favour of wood pellets. This can be explained by the economic viability of the renewable source of energy. Firstly, the energy content of pellets is about 5 kW/kg (depending on the pellet quality - better quality - more heat - less consumption). These figures prove that wood pellets can easily substitute coal.
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