www . refrigerationandaircon . co . za RACA Journal I January 2025 3
News
GREEN TAXES INCREASE THE NEED FOR LOAD-BALANCED , SMARTER STEAM
Supplied by AES
As the debate around emissions , affordability and ‘ green ’ taxes on exports to the EU scales up , it is not yet certain how emissions will be measured .
Whether it is the South African government ’ s recently signed carbon tax legislation , or the advent of ‘ green ’ import taxes imposed by the European Union ( EU ), South Africa ’ s manufacturing sector faces considerable sustainability challenges , according to Dennis Williams , commercial director of Associated Energy Services ( AES ), a leading operations and maintenance service provider to the steam and boiler sector .
As the debate around emissions , affordability and ‘ green ’ taxes on exports to the EU scales up , Williams points out that it is not yet certain how emissions will be measured , whether improvements made to existing energy plants will be recognised by the relevant authorities – or if manufacturing companies will find themselves forced to make a complete switch-over to alternative fuels . “ This would certainly come as a blow to South African manufacturers that still rely on fossil fuels ,” he observes . AES believes that a company ’ s sustainability journey begins with maximising what can be achieved with existing energy plants .
“ By managing combustion and ensuring that this is ultraresponsive to the changing requirements of each manufacturing plant , both costs and emissions can be optimised . However , different fuel types react differently to fluctuating steam demands . For example , as gas combustion systems provide a high range of turndown , they respond extremely quickly . Solid fuel combustion systems such as coal and biomass react more slowly to changes in steam demand ,” he explains .
He adds that because there is a given amount of solid fuel in the combustion furnace at any one time , whatever changes in steam demand occur will require a change in the amount of fuel being fed into the furnace – together with the amount of oxygen required to maintain effective combustion .
“ The problem arises where there are multiple boilers online and suddenly , there is a substantial steam demand peak . On regular auto-control , they ramp up to follow that peak and eventually catch up . However , when it subsides , there is a massive amount of thermal inertia in these boilers . It is very difficult to quickly counteract this , and this is wasteful in terms of one ’ s ability to burn coal effectively .”
All images supplied by AES
AES operations personnel at the boiler control system panel .
BALANCING THE LOAD AES ’ s load balancing system enables multiple solid-fuel boilers to work together to effectively and efficiently deliver steam on demand . Key to this is understanding a company ’ s steam load . If it is flat with only gradual changes , loads can easily be followed . Sudden spikes and drops in steam demand are unfortunately more difficult to control .
A co-ordinated approach , using the overarching load-balancing control system , effectively coordinates steam demand across multiple boilers and ensures optimisation of the online capacity to deliver the demand efficiently and effectively , Williams advises : “ We control how each of those boilers is synchronised to follow the load – and reduce when the load reduces . This system achieves optimised efficiency and improves the assets ’ ability to maintain pressure control by applying analysis to demand changes to sequence boiler loads effectively .”
These systems are very much data driven . Setpoint inputs are carefully adjusted to ensure the narrowest steam pressure control band possible is achieved , so that steam pressure remains stable . The key metrics within the operating model can be adjusted to meet the unique requirements of each site – and accommodate the number of boilers that need to be load-balanced .
Furthermore , instrumentation really comes to the fore in measuring the efficiency of combustion based on the constituents of the flue gas coming out of the boiler . “ We rely on levels of carbon
www . refrigerationandaircon . co . za RACA Journal I January 2025 3