Heating and combustion equipment manufacturer Riello continues to develop products to meet andexceed NOx emission regulations, and in 2023 is launching a new burner series in the UK which incorporatesinnovative and patented Ultra-Low NOx combustion head technology.
Legislation continues to drive down permissible NOx emission levels from combustion equipment, and there is increasing monitoring of appliance emissions to ensure compliance with multiple environmental and regulatory requirements.
Previously therehave been two principal means by which combustion NOx emission levels have been mitigated;either Flue Gas Recirculation (FGR) technology, or the application of premix burner technology. Each of these technologies is effective in reducing appliance NOx emission levels, but bothhave some limitations on their application.
FGR technology requires a higher degree of burner technology and the installation of extra ducting from the appliance flue to the burner. This adds to installation complexity and maintenance costs, and has some limits on operation with regard to minimum permitted recirculating flue gas temperature.
Premix technology has a relatively low maximum capacity limit of approximately 3,000 kW, and the configuration of the required long combustion head adds to installation and servicing costs.
The NEW Riello ULX Series of Ultra-Low NOx emission gas burners removes theseapplication barriers which prevent utilisation of the FGR and premix technologies andprovides a solution that can be applied on all boiler types* and at all operating temperatures.
(*The only current exception to this being appliances which incorporate a reverse flame combustion chamber configuration, as testing of the burners on these types of boilers is yet to be completed. It is well known however, that to permit ultra-low NOx emission combustion and deliver minimum emission levels,appliances with through-pass [3-pass] combustion chamber design enable substantially better performance than reverse flame designs.)
Essentially the NEW series burners are based on the tried and tested Riello RS pressure jet burner design principles, maintaining the reliability and robustness of those models. On first appearance they look very much likethose burner models that have been available for many years, but it is the innovative and patented combustion head technology of the Riello ULX series which ‘breaks new ground’ with regard to minimising NOx emissions.
Riello RS 510/E ULX Burner
The combustion head design of the Riello ULX series burnersincorporates both ‘staged air’introduction control in the ‘core’ of the flameand ‘internal flue gas recirculation’control in the external region,or periphery,of the flame.
The resultant reduction in NOx emission with this combustion head technology allows compliance with the requirements of the most stringent requirements worldwide, on multiple appliance types, including steam and high temperature hot water boilers.
Tests performed in the Riello Combustion Research Centre in Italy, and on appliances installed in multipleinternational locations have shown that with the right conditions, NOx emission levels of 30 mg/kWh (net CV),i.e. 30 mg/Nm3 @ 3% O2 flue gas reference, are readily achievable. This NOx emission level is significantly below the current Greater London Authority (GLA) requirements of 40 mg/kWh (gross CV).
All models of the NEW Riello ULX series of gas burners incorporate electronic cam, or direct digital control, of the air fuel ratio by means of independent servomotor driven regulation, maximising efficiency and simplifying commissioning and servicing.
Burner specification options for Variable Speed control of the combustion air fan and O2 combustion trim, are also available for further improvement in efficiency and reduction in electrical consumption and noise reduction.
The NEW Riello ULX series of gas burners is available for an operating capacity range from 350 kW to 4,600 kW, with further models extending the range to greater than 7,000 kW to be introduced following completion of field and approval testing. Additionally, dual fuel firing versions of the burner series, able to operate with gas or light oil, are being developed for future introduction to the market, so watch this space!
For details of the NEW Riello ULX series of gas burners please contact the Riello Limited Sales Team on 01480 432144.
Bernard Dawson – Technical Director, Riello Limited
This article can also be found in the issue below.