Why to buy a boiler with Lambda control !

Sense of lambda probe in the gasifications boilers.

Just as every modern car is equipped with a lambda probe, it is appropriate for perfect combustion that a modern gasification boiler can also be equipped with a lambda probe. We are aware of the importance of a lambda probe in a boiler, which is why we have designed our PYROGAS boilers so that they can also be offered with this equipment.

European technical standards for all devices that produce unwanted 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, such devices are now equipped with sophisticated electronic control technology.

One of the necessary conditions for a gasification boiler to emit emissions into the air through the exhaust-chimney pipe in every heating mode within the limit permitted by the standard and at the same time achieve high combustion efficiency is that, depending on the operating conditions and the country of destination, it must also be equipped with a lambda probe.

A 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 that is 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 firewood or wood briquettes - is continuously supplied with the optimal amount of air. The air supply to the boiler is divided into primary and secondary air oxygen. The quantity and ratio of these two components of the supplied air is important for achieving low-emission operation, high efficiency and uniform combustion without power fluctuations. Primary air is supplied to the primary refractory nozzle of the combustion chamber in the boiler through a separate channel and 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 have built-in rotary dampers, which can be mechanically adjustable or independently controlled by servomotors based on the evaluation, in the regulator, of the amount of oxygen in the flue gas. The entire process of air supply, combustion process and flow of flue gas through the boiler body to the flue gas duct can be ensured in a high quality by a boiler equipped with a lambda probe, 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. For the above reasons, the need and ratio of primary and secondary air supply to the combustion process constantly changes during heating in the boiler.

In boilers with fixed or manual adjustment of the amount of air supply and fan speed, it is quite difficult to achieve very low emissions and high efficiency in the long term, corresponding to the lowest limits in the European standard EN 303.5, or national deviations of some European Union member states. In order to eliminate these constantly changing effects on the combustion process, it is necessary for the boiler to be electronically controlled by a controller, which, based on continuous evaluation of the flue gas temperature, can control the fan speed and, when equipped with a lambda probe, the amount of oxygen in the flue gas with a sophisticated algorithm, automatically control the servomotors so that combustion is as perfect as possible. Such combustion when heated with wood or wood briquettes corresponds to an average of 5.26% residual oxygen, which represents the lambda value λ=1.35. If the boiler is equipped with a lambda probe, the controller controls its value and also visualizes the actual value.

The combustion process is an exothermic chemical process taking place in a refractory concrete combustion chamber at high temperatures of up to 1200ºC. Hot flue gases from the combustion chamber pass through the space around the walls of the hot water circuit of the boiler body, which are the water surfaces of the boiler and the water fins up to the chimney. This gradually transfers heat from the flue gases to the water jacket of the boiler body, which is then discharged into the heating medium - radiators, underfloor heating, hot water tank, storage tank, etc. The flow rate of the flue gases, the size of the water surface of the boiler body, the robustness, shape and quality of the refractory concrete combustion chamber and the time it takes for the flue gases to reach the boiler flue outlet are also important for the efficiency of the boiler. The lower the temperature of the flue gases at the boiler flue outlet, the higher the efficiency of the boiler.

In modern boilers, the sensible heat loss of flue gases /chimney loss/ can be at the level of 6-8%. With this value, as the main component of the boiler efficiency calculation, it is possible to achieve boiler efficiency above 89-93%, which corresponds to a flue gas outlet temperature of approx. 140 - 180 ºC. Higher efficiency above approx. 93%, or. lower flue gas temperature below 120 ºC, can, on the other hand, result in a deterioration of the chimney draft to the extent that the flue gases passing through the chimney begin to condense. Tar begins to form on the inner walls of the chimney, which can lead to its blockage, or even the risk of tar ignition and subsequent fire if regular cleaning is neglected.

In well-designed modern boilers, it is possible to achieve operating emission values ​​significantly lower than those specified in class 5 in EN 303.5, or. the Ecodesign requirements.