The Regenerative Ceramic Burner system was first developed into a commercial product in 1982 by Hotwork Development Ltd based from an original concept from British Gas Midland Research Station. This led eventually to the Queen's Award for Technological Achievement in 1992. Thousands of Hotwork RCB systems have been used in a wide variety of applications (reference list available on request) such as steel reheating, forging, heat-treatment, aluminium melting and glass melting, which positions Hotwork Combustion Technology Ltd today as the most experienced designer of regenerative burner systems.

An RCB unit comprises at least two burners, two regenerators packed with alumina balls, a flow reversal system and associated controls, with each burner close coupled to a regenerator (or joined by a refractory-lined duct to suit space availability).

While one burner fires using air fed to the base of its regenerator, the other burner acts as an exhaust port by drawing off waste gases which preheat its regenerator.

When this regenerator is sufficiently charged, typically every 60-90 seconds, the reversing system alters the flow of combustion air and exhaust gases so that the regenerator which has stored thermal energy switches to firing mode and preheats the incoming combustion air, whilst the previously cooled regenerator is now heated up by the waste gases leaving the furnace through its associate burner (Figure 1 & Figure 2).

Figure 1: Typical regenerative burner layout

Figure 3: Temperature movements at the top and bottom of the regenerators

With the combustion air being preheated to 85-90% of the furnace temperature, the amount of fuel required by the process is considerably reduced. Figure 4 illustrates the fuel savings achievable at various furnace temperatures compared with cold air burners and recuperators.

The higher the process temperature, the higher the potential to save fuel. At reheating and forging temperatures, typically 1300-1400 ° C, fuel consumption can be reduced by 58-65%, whilst for melting aluminium where furnace temperatures reach 1150 ° C, fuel savings of up to 49% can be achieved.

Figure 4: Fuel savings compared with cold air burners and recuperators.

Low exhaust temp

With a high proportion of heat from the waste gases recovered by the regenerators, temperatures of waste gases are reduced to 150-200 ° C. Not only can a modestly powered exhaust fan of standard construction be used at these low temperatures but also there is no need for refractory-lined flues and chimneys or recuperator to be used. An eductor driven by air from the combustion air fan can be used as an alternative to the exhaust fan.

The ability of the regenerators to trap particulates from contaminated processes such as the melting of dirty aluminium scrap, combined with low exhaust temperatures, results in additional filtering equipment (bag plants) being considerably smaller. This is a clear advantage, from a capital outlay point of view, to bear in mind when opting for a regenerative system over a cold or warm air.

In the majority of cases, RCB systems operate with modulating control systems but other forms of control are available such as high/low, on/off or pulse firing.

Contact Hotwork Combustion Technology Ltd for a complete regenerative combustion package including the burners, the air, fuel and exhaust control components, the reversal logic and the control system, all on a turnkey basis for both new furnaces and for modernisation of existing furnaces.

Hotwork Combustion Technology burners are renowned for their excellent performance in terms of flame stability, velocity and turndown on ratio and fuel only control and the RCB Burner is no exception. It can deliver combustion gas velocities in excess of 90 m/s and can turn down to 10/1 on natural gas on ratio, which outperforms other regenerative systems. This results in rapid and uniform heat distribution inside a furnace as well as improved and controlled heat transfer to the load.

These features make the Low NOx RCB Burner ideal for applications such as forging and heat-treatment, where the load has to be heated in a controlled manner to comply with stringent quality assurance standards like Rolls Royce RPS953, or aluminium melting where the combination of convection and radiation results in improved melt rates.

The increase in productivity, improvement in product quality and reduction in levels of rejects all contribute to shortening the payback period.