Control of O₂ in thermal oil boilers


Energy efficiency

One of the techniques used for energy efficiency is the provision of digital modulating burners with continuous oxygen control. This enhancement results in an increase in performance of around 2% and a consequent reduction in fuel consumption. Furthermore, this system ensures a reduction in combustion product emissions and enhanced operational safety.

The burner and its controller are responsible for the optimum regulation of the amount of fuel and air for combustion. Excess air facilitates the absence of unburned substances. However, this excess air also reduces the performance of the boiler-burner unit. In brief, this is a system which maintains the oxygen at the minimum percentages, thereby ensuring an optimum performance, the absence of unburned substances and safe combustion.

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The system comprises a continuous oxygen sensor located in the boiler´s thermal fluid pipe. This equipment should be designed to support high combustion fume temperatures. This O₂ sensor continuously informs the digital combustion controller which maintains the inflow of oxygen in the burner at the lowest levels in accordance with safety requirements.

Burner Management System

The BMS – Burner Management System – is responsible for optimising the fuel – oxidiser mixture, as a percentage of O₂. Ideally, this oxygen percentage needs to be reduced to a minimum in order to achieve maximum combustion efficiency. As mentioned previously, this would favour the presence of unburned substances and increase the risk of soiling the thermal oil boiler´s combustion chamber. The aim of this BMS is the digital control of combustion within the optimum parameters as means of achieving maximum performance. This BMS defines the correct position of the burner´s servomotor.

The percentage of O₂ in the fumes of thermal oil boilers depends on a number of factors, as illustrated in the table below:

MagnitudeVariation in magnitudeVariation in O₂ in the fumes
Combustion air temperature10 K0,50%
Air pressure10 mbar0,20%
Air humidity2%0,40%
Fuel PCI7,50%1,50%
Combustible gas pressure10%7% (of the burner power)

We at Pirobloc use O₂ control in our thermal oil boilers in addition to other options which provide our equipment with the maximum safety, reliability and efficiency.