Solid fuel heating equipment is represented today by a whole group of devices. Each solid fuel boiler manufactured today by domestic and foreign manufacturing companies is a completely new, high-tech heating device. Thanks to the introduction of technical innovations into the design of heating devices and equipping with automatic control devices, it was possible to significantly increase the efficiency and optimize the operation of solid fuel boilers.
In heating devices of this type, the traditional principle of operation is used, similar to the version of stove heating that is well known to us. The main action is due to the process of generating thermal energy released during combustion in the boiler furnace of coal, coke, firewood and other fuel resources, followed by heat transfer to the coolant.
Like other devices that provide the generation and transmission of energy, boiler equipment has its own efficiency. Let us consider in more detail what the efficiency of units operating on solid fuel is. We will try to find answers to questions related to these parameters.
What is the efficiency of heating devices
For any heating unit, whose task is to heat the internal space of residential buildings and structures for various purposes, an important component was, is and remains the efficiency of work. The parameter that determines the efficiency of solid fuel boilers is the efficiency factor. Efficiency shows the ratio of the spent heat energy, issued by the boiler in the process of burning solid fuel, to the useful heat supplied to the entire heating system.
This ratio is expressed as a percentage. The better the boiler works, the higher the interest. Among modern solid fuel boilers there are models with high efficiency, high-tech, efficient and economical units.
For reference: as a rough example, consider the heat generated by sitting near a fire. The thermal energy released during the burning of firewood is able to heat the space and objects limited around the fire. Most of the heat from a burning fire (up to 50-60%) goes into the atmosphere, giving no benefit other than aesthetic content, while neighboring objects and air receive a limited amount of kilocalories. The efficiency of the fire is minimal.
The efficiency of heating equipment is highly dependent on what type of fuel is used and what are the design features of the device.
For example: when burning coal, firewood or pellets, different amounts of thermal energy are released. In many ways, the efficiency depends on the technology of fuel combustion in the combustion chamber and the type of heating system. In other words, each type of heating devices (traditional solid fuel boilers, long-burning units, pellet boilers and pyrolysis devices) has its own technological design features that affect the efficiency parameters.
The operating conditions and the quality of ventilation also affect the efficiency of the boilers. Poor ventilation causes a shortage of air, which is necessary for the high intensity of the combustion process of the fuel mass. The condition of the chimney affects not only the level of comfort in the interior, but also the efficiency of heating equipment, the performance of the entire heating system.
The accompanying documentation for the heating boiler must have the equipment efficiency declared by the manufacturer. Compliance with the real indicators of the declared information is achieved due to the correct installation of the device, strapping and subsequent operation.
Rules for the operation of boiler devices, compliance with which affects the value of efficiency
Any type of heating unit has its own optimal load parameters, which should be as useful as possible from a technological and economic point of view. The process of operation of solid fuel boilers is designed in such a way that most of the time the equipment works in the optimal mode. To ensure such work allows compliance with the rules for the operation of solid fuel heating equipment. In this case, you must adhere to and follow the following points:
- it is necessary to observe acceptable modes of blowing and operation of the hood;
- constant control over the intensity of combustion and completeness of fuel combustion;
- control the amount of carryover and failure;
- assessment of the state of surfaces heated during fuel combustion;
- regular cleaning of the boiler.
The listed points are the necessary minimum that must be adhered to during the operation of boiler equipment during the heating season. Compliance with simple and understandable rules will allow you to obtain the efficiency of an autonomous boiler declared in the characteristics, improve the operation of a solid fuel boiler.
We can say that every little thing, every element of the design of the heating device affects the value of the efficiency. A properly designed chimney and ventilation system provide optimal air flow into the combustion chamber, which significantly affects the quality of combustion of the fuel product. The work of ventilation is estimated by the value of the coefficient of excess air. An excessive increase in the volume of incoming air leads to excessive fuel consumption. Heat escapes more intensively through the pipe along with combustion products. With a decrease in the coefficient, the operation of the boilers deteriorates significantly, and there is a high probability of the occurrence of oxygen-limited zones in the furnace. In such a situation, soot begins to form and accumulate in large quantities in the furnace.
The intensity and quality of combustion in solid fuel boilers require constant monitoring. The loading of the combustion chamber must be carried out evenly, avoiding focal fires.
On a note: coal or firewood is evenly distributed over the grate or grate. Combustion should take place over the entire surface of the layer. Evenly distributed fuel dries quickly and burns over the entire surface, ensuring complete burnout of the solid components of the fuel mass to volatile combustion products. If you correctly put the fuel into the furnace, the flame when the boilers work will be bright yellow, straw-colored.
During combustion, it is important to prevent failures of the fuel resource, otherwise you will have to face significant mechanical losses (underburning) of the fuel. If you do not control the position of the fuel in the furnace, large fragments of coal or firewood that have fallen into the ash box can lead to unauthorized ignition of the remains of the fuel mass products.
Soot and tar accumulated on the surface of the heat exchanger reduce the degree of heating of the heat exchanger. As a result of all these violations of operating conditions, the useful amount of thermal energy required for the normal operation of the heating system decreases. As a result, we can talk about a sharp decrease in the efficiency of heating boilers.
Factors on which the efficiency of boilers depends
Boilers with a high efficiency value are currently represented by the following heating equipment:
- units operating on coal and other solid fossil fuels;
- pellet boilers;
- pyrolysis devices.
The efficiency of heating devices, in the furnace of which anthracite, coal and peat briquettes are used, averages 70-80%. Significantly higher efficiency of pellet devices — up to 85%. Loaded with granules, heating boilers of this type are highly efficient, giving out a huge amount of thermal energy during the combustion of fuel.
On a note: one load is enough for the device to operate in optimal modes up to 12-14 hours.
The absolute leader among solid fuel heating equipment is a pyrolysis boiler. These appliances use wood or wood waste. The efficiency of such equipment today is 85% or more. The units also belong to highly efficient long-burning devices, but subject to the necessary conditions — the moisture content of the fuel should not exceed 20%.
Important for the value of the efficiency is the type of material from which the heater is made. Today on the market are models of solid fuel boilers made of steel and cast iron.
For reference: The first is steel products. To reduce the market value of the unit, manufacturing companies use the main structural elements made of steel. For example, the heat exchanger is made of high-strength heat-resistant black steel 2-5 mm thick. The heating tubular elements used to heat the main circuit are made in the same way.
The thicker the steel used in the construction, the higher the heat transfer characteristics of the equipment. Accordingly, the efficiency increases.
In steel devices, an increase in efficiency is achieved by installing special internal partitions in the form of pipes — main flow stages and smoke dividers. Measures are forced and partial, allowing to slightly increase the efficiency of the main device. Among the models of steel solid fuel boilers, it is rare to find devices with an efficiency above 75%. The service life of such products is 10-15 years.
Foreign companies, in order to increase the efficiency of steel heating boilers, use the bottom combustion process in their models, with 2 or 3 traction flows. The design of the products provides for the installation of tubular heating elements to improve heat transfer. Such equipment has an efficiency in the range of 75-80%, and can last longer, 1.5 times.
Unlike steel units, cast-iron solid propellant apparatuses are more efficient.
The design of cast iron units uses heat exchangers made of cast iron alloy of a special grade, which has a high heat transfer. Such boilers are most often used for open heating heating systems. Products are additionally equipped with grates, thanks to which an intensive selection of thermal energy is carried out directly from the burning fuel placed on the grates.
The efficiency of such heating devices is 80%. Consideration should be given to the long service life of cast iron boilers. The service life of such equipment is 30-40 years.
How to increase the efficiency of solid fuel heating equipment
Today, many consumers, having a solid fuel boiler at their disposal, are trying to find the most convenient and practical way to increase the efficiency of heating equipment. The technological parameters of the heating devices, set by the manufacturer, lose their nominal values over time, therefore, various methods and means are being sought to improve the efficiency of boiler technology.
Consider one of the most spectacular options, the installation of an additional heat exchanger. The task of the new equipment is to remove thermal energy from volatile combustion products.
In the video you can see how to make your own economizer (heat exchanger)
To do this, we first need to know what the temperature of the smoke at the outlet. You can change it with a multimeter, which is placed directly in the middle of the chimney. Data on how much additional heat can be obtained from volatile combustion products is necessary to calculate the area of an additional heat exchanger. We do the following:
- we send firewood of a certain amount to the firebox;
- we detect how long it takes to burn a certain amount of firewood.
For example: firewood, in the amount of 14.2 kg. burn for 3.5 hours. The flue temperature at the outlet of the boiler is 460 0 FROM.
In 1 hour, we burned down: 14.2 / 3.5 \u003d 4.05 kg. firewood.
To calculate the amount of smoke, we use the generally accepted value — 1 kg. firewood = 5.7 kg. flue gases. Next, we multiply the amount of firewood burned in one hour by the amount of smoke obtained by burning 1 kg. firewood. As a result: 4.05 x 5.7 = 23.08 kg. volatile combustion products. This figure will become the starting point for subsequent calculations of the amount of thermal energy that can be used additionally to heat the second heat exchanger.
Knowing the value of the heat capacity of volatile hot gases, as 1.1 kJ / kg., We make a further calculation of the heat flow power if we want to reduce the temperature of the smoke from 460 0C to 160 degrees.
Q \u003d 23.08 x 1.1 (460-160) \u003d 8124 kJ of thermal energy.
As a result, we obtain the exact value of the additional power provided by volatile combustion products: q = 8124/3600 = 2.25 kW, a large figure that can have a significant impact on improving the efficiency of heating equipment. Knowing how much energy is wasted, the desire to equip the boiler with an additional heat exchanger is fully justified. Due to the influx of additional thermal energy to work on heating the coolant, not only the efficiency of the entire heating system increases, but the efficiency of the heating unit itself increases.
Despite the abundance of models of modern heating equipment, solid fuel boilers continue to be one of the most efficient and affordable types of heating equipment. Compared to electric boilers, which have an efficiency of up to 90%, solid fuel units have a high economic effect. The increase in efficiency on new models allowed this type of boiler equipment to come close to electric and gas boilers.
Modern solid fuel vehicles are able not only to operate for a long time, using affordable natural fuel resources, but also have high performance characteristics.