Why a boiler with a Lambda probe?

The importance of the lambda probe in gasification boilers. 

Just as every modern car is equipped with a lambda probe, every modern gasification boiler should be equipped with a lambda probe. We are aware of the importance of the lambda probe in boilers, which is why our PYROGAS boilers already have a lambda probe as standard equipment.

European technical standards for all devices that produce harmful emissions during their operation /especially CO, CO2, NOx, OGC, dust, etc./ set very strict limits due to the constantly deteriorating environment due to the leakage of these emissions into the air.

To ensure that the limit values ​​are not exceeded during operation /see table below/, such devices are now equipped with sophisticated and structurally complex electronic control technology.

One of the essential conditions for a gasification boiler to emit emissions into the air through the exhaust-chimney pipe within the standard limit in every heating mode and at the same time achieve high combustion efficiency is that it must be equipped with a lambda probe.

The lambda probe is a ceramic, electrochemical oxygen analyzer, mounted in the outlet of the boiler flue connected to an electronic controller. The role of the lambda probe is to measure the amount of oxygen in this pipe and transmit this value in the form of an electrical signal to an electronic controller structurally capable of evaluating this value during boiler operation and subsequently controlling the entire combustion process so that the burning fuel - in our case, burning fuel wood, or wood briquettes, is continuously supplied with the optimal amount of combustion air, which is divided into primary and secondary air oxygen in the boiler and the optimal ratio of these two components with the highest possible efficiency and uniformity of combustion without power fluctuations. The primary air in the boiler is supplied to the primary refractory concrete nozzle of the combustion chamber through a separate channel, and the secondary air is supplied directly to the combustion chamber through another separate channel, thus ensuring perfect burnout of the burning gases. Primary air, together with the fan, mainly contributes to the boiler's performance, and secondary air is important for low-emission combustion. Both channels usually have built-in rotary dampers, which are automatically and independently controlled by servomotors based on the evaluation of the amount of oxygen in the flue gas in the regulator. The entire process of air supply, combustion process and flue gas flow through the boiler body to the flue gas duct can be ensured in a high quality manner and under all operating conditions, i.e. after the boiler is fully loaded with fuel, its gradual consumption during combustion, fuel burn-out, different quality and type of wood /always max. 20% moisture/, different chimney draft, etc. only by a boiler equipped with a lambda probe. For the above reasons, during heating in the boiler, the need and ratio of primary and secondary air supply to the combustion process are constantly changing. In boilers with solid or It is not reliably possible to achieve very low emissions and high efficiency in the long term, corresponding to the lowest limits in the European standard EN 303.5, by manually adjusting the amount of air supply and fan speed. In order to eliminate these constantly changing influences on the combustion process, it is necessary for the boiler operation to be electronically controlled by a regulator, which, based on continuous evaluation of the amount of oxygen in the flue gases with a sophisticated algorithm, automatically controls the servomotors and fan speed so that combustion is as perfect as possible. Such combustion when heated with wood or wood briquettes corresponds to 5.3% residual oxygen measured by a lambda probe in the flue gases, which represents a lambda value of λ=1.35.

The combustion process is a chemical process taking place in a refractory concrete combustion chamber at high temperatures of up to 1200ºC. The hot flue gases from the combustion chamber then pass through the hot water circuit of the boiler body, which is the water surfaces of the boiler and the water fins or tube sheets to the chimney. The flow speed of the flue gases, the size of the water surface, the robustness and shape of the refractory concrete combustion chamber and the time until the flue gases reach the mouth of the boiler flue are also important for the efficiency of the boiler.

In well-designed modern boilers with a lambda probe, it is possible to achieve emission values ​​even in the long term lower than those specified in class 5 in EN 303.5, /see table below/ with an efficiency of 88-93%.