Use or not use a buffer tank with pellet boiler, or why is an automatic boiler house often cheaper than a properly made manual boiler house?
Using a conventional solid top without pellet burner and without a buffer, it is extremely dangerous and economically unprofitable, since in the smoldering mode, the efficiency of a solid fuel rapidly drops, and this is especially true for boilers with afterburning of combustion products!
As we wrote earlier - everything solid fuel boilers to achieve maximum efficiency, they work in a narrow range of temperatures and powers. The width of the range for different types of TT boilers varies, but all the same, the main drawback is that the narrow zone of stable operation is practically invincible and is the main problem of solid fuel heating. The second and significant problem is security. Placed masonry of fuel, in various types of combustion (top, bottom, long-term, pyrolysis, and the like) has a common disadvantage - the fuel cannot be quickly extinguished. The masonry heats up, a pyrolysis (thermal decomposition) gas is released, which burns generating heat, in some solid fuel boilers the gas burns upwards, in others downwards, which does not significantly affect the controllability of the process. If the power supply is cut off or if the heating system is unable to take off, abruptly take away all the heat released from the fuel tab - the boiler temperature inevitably begins to rise. The options for solving this situation are multifaceted, but they all boil down to a simple idea - heat dissipation, and as the most economically sound way - heat dissipation into an accumulator or buffer capacity (depending on the tasks). It is the volume of the container that is a kind of brake. Even a completely closed air supply to the boiler does not extinguish the fuel and heat continues to be released. It is precisely because of the safety and economic component in the utilization of excess heat that buffer and heat storage tanks have become widespread. Moreover, a conflict arises - the TT boiler operates optimally in hot mode, when the supply is in the range of 75-85 * C, the return flow is at least 65 * C, while there is a small margin to the boiling zone of the coolant, and the fuel burns most efficiently, but the temperatures of the smoke gases also rise (efficiency falls with emissions to the street). Heat, as we already wrote, is discharged into the heat accumulator. By closing the air blowing - the situation can be aggravated by the fact that a lot of unburned carbon appears, which is precisely the basis of tar and tar on the walls of the boiler and chimney. With a sufficient amount of it, the chimney can flare up and lead to a fire, destruction of the chimney structure, and other negative consequences. Those. extinguishing the boiler in this way is not recommended and even dangerous under the confluence of circumstances.
There are masses of craftsmen among the people trying to prove that boilers without a buffer tank are not dangerous, they can be successfully operated, they give a lot of examples. But the regulatory framework and rules for the operation of solid fuel boilers - work without a buffer tank is strictly prohibited. This is labor protection, written by the lives of people, and engineering calculations and economic justifications.
We are often as producers pellet boilers we are faced with the opposite opinion when the standards of the classical boiler TT norms are applied to the pellet boiler. Namely, the need to install at least a buffer tank and a heat accumulator. This misconception often pushes people to additional costs, for no apparent reason. The essence is simple - for normal operation of a pellet boiler or a pellet burner installed in a TT boiler, the installation of additional heat accumulators or buffer tanks is not required, unless otherwise provided by the project and the needs of the heating system. For example, in greenhouse complexes, to compensate for sudden temperature drops, it is simply vital to install a capacious heat accumulator, but this is not necessary for pellet burner.
Let's take a simple example. A household boiler weighs an average of 200-300kg. When the power supply is cut off, there is approximately 300-500 grams of fuel in the nozzle of the pellet burner (let's say with a margin of 50 kW), which, under the ideal combination of circumstances, can produce a maximum of 2.5 kW of heat. This energy is enough to heat a mass of 300 kg from 85 * C to 92 * C (i.e. only 7 * C). We did not take into account the heat escape from the smoke gases, the reduced combustion intensity in the absence of intensive blowing by the fan, and in any case the microcirculation present in the system. All these factors will reduce the already small delta. Those. we see that even in the most difficult case, the situation cannot get out of control. At the same time, the automation of the pellet burner has a number of additional protection systems against boiler overheating, and we also take into account the mandatory presence of relief valves.
All these factors and the exact dosage of fuel with modern automation equate the flexibility of a pellet boiler, its automation, and the response to a change in the heating system to a gas boiler, which itself does not require a buffer tank.
From this it follows that in a pellet boiler room there is no need for most devices inherent in a manual loading boiler room!
Best regards - FOCUS team