WORKPLACE SAFETY
HOW TO INCREASE FIRETUBE BOILER EFFICIENCY
By Etienne Fourie, technical sales manager, Babcock Wanson T
here is no denying that process heating sys- tems that are widely used across industry are large consumers of energy. With sky high energy prices to contend with and Net Zero on the horizon, efforts to reduce energy consumption, improve efficiency and reduce emissions are centre stage. In the case of large organisations, assess- ment of the energy used within their buildings, in- dustrial processes and transport is mandatory under the Energy Saving Opportunities Scheme (ESOS). But of course, businesses of all sizes can benefit from improved energy management. When it comes to Firetube boilers, manufacturers of these systems have been working hard to im- prove overall efficiency and control of boilers and burners. Here we look at the key developments that, combined, could increase your Firetube boiler efficiency by 45 per cent - a substantial figure.
VARIABLE SPEED DRIVE
Electric motors represent around 50 per cent of global electricity consumption. In the EU alone, there around eight billion electric motors in use. Whilst many motors are very small and use little electricity, those in industry are often large and major consumers of electricity.
Motors used on boiler feed pump and combus- tion air blowers traditionally operate at a con-
stant speed. In the case of pump applications, the motor is used alongside a modulating control valve to control the pressure or flow of water. With the air blower, the motor is accompanied with variable inlet vanes or a modulating outlet damper to control the pressure or flow of air. However, boilers are rarely operated continu- ally at full capacity, so maintaining the motor at the same speed at all times is wasteful. Where process load demands are variable, motors can be fitted with a variable speed drive (VSD) which can increase efficiency by up to 30 per cent (based in reduced electrical consumption). A VSD is an electronic device used to adjust the rotation speed of an electric motor according to the needs of the application. In a Firetube boiler they can be used to vary the pump or fan speed according to demand, ramping up or down the frequency and voltage to the motor, reducing overall energy consumption.
A further benefit to be had from the use of a VSD is equipment longevity. The inherent soft- start function of a VSD, means the motor starting current can be reduced, which decreases thermal and mechanical stresses.
FLUE GAS AND CONDENSING ECONOMISERS Economisers are essentially heat exchange de- vices that extract the residual heat from the ex- haust gas generated by the combustion process. That recovered heat is usually fed back into the process, typically to the boiler feed water thereby optimising the overall efficiency of the plant in the most compact and cost-effective manner. By using economisers, you can expect to increase efficiency of your Firetube boiler by 15-20 per cent. Babcock Wanson offers a broad range of exhaust gas economisers perfectly matched to the boiler to which they will be fitted, incorporating ultra-robust extended surface tubes, which ensure the best practicable heat transfer and allow boiler thermal efficiencies of 98 per cent and greater to be achieved. So efficient are they, that the return on investment can be as little as a single year. Different types of economisers are available to meet a wide variety of processes and site needs, including economisers that can be mounted in a drawer in the back box of the boiler and those suitable for mounting in casing on the smoke out- let, plus economisers with feed water exchanger,
22 WINTER 2024 | INDUSTRIAL COMPLIANCE
and those that come with fumes / water / com- bustion air exchanger. One aspect that is import- ant, especially when operating on an interruptible gas supply, is that the economiser is able to work with both natural gas and Class D Fuel Oil.
MICRO MODULATING BURNER
By swapping to one of the latest generation of micro-modulating burners you can improve operational efficiency of a Firetube boiler by five per cent.
Traditional burners are often imprecise and not well matched with the boiler. The new style micro-modulating burners, such as our Optimo range, achieve very accurate control of low excess air levels throughout the turndown range resulting in an excellent combustion efficiency no matter what the process load.
Furthermore, the latest burners have been de- signed with a very high turndown ratio, enabling the burner to adjust its output to meet the needs of the process. This avoids the costly energy losses incurred by continual stop/start cycles.
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