The Thermal Combustion ‘Balancing Act’

From carbon taxes to export tariffs, cost containment to security of supply and sustainability, companies are under increasing pressure to switch to greener fuel sources. However, warns leading steam and boiler operations and maintenance service provider, Associated Energy Services (AES), this pivotal change has some potentially serious knock-on effects.

For AES Commercial Director Dennis Williams and Projects Director Gavin Evezard, legal drivers and corporate head office decisions may initiate the process – but a fuel source switch needs to be case-specific. The ‘plus’ side to this is that carefully considered upgrades, such as the kind which AES manages for its clients, will not only see more effective combustion and better fuel efficiency. They will also enhance productivity and even relationships with communities in areas surrounding clients’ operational sites – ultimately future-proofing their energy plant. However, options must always be logistically and financially viable.

Williams and Evezard note that global commitments made by South Africa in terms of climate change tend to centre on so-called ‘big business’ – rather than on companies further down the supply chain, which are (typically) under immense pressure to contain costs and manage risk. These businesses are constantly juggling the demands of various stakeholders – government, investors, employees and even decision-makers at a multinational level – but will ultimately have to confront the thermal combustion and fuel source conundrum head-on.

Not all biomass is created equal

Because of the low energy density of biomass, it ironically often emits more CO₂ per ton of steam than some conventional fossil fuels. “The use of biomass – timber for example – generates a higher tonnage of CO₂ per unit useful energy than coal does, and this is a function of fuel qualities (composition, moisture content) and overall thermal efficiency. However, it has been accepted that the carbon in biomass derives from photosynthesis, has been removed from the atmosphere – and is not CO₂ stored in the earth as coal or oil – it is deemed to be carbon-neutral,” Williams explains.

Evezard also notes that the potential opportunity for a switch to biomass is region-specific so there is not a ‘one size fits all’ approach when switching to greener fuels:  “Technology selection based on the biomass available is critical.” Furthermore, space requirements for storing the more bulky biofuels present an added complication – as does long-term supply and pricing, together with potential logistics costs associated with long- distance transportation thereof.

“For industrial thermal applications, the operational cost of a biomass plant may be similar or slightly higher than for a fossil fuel plant. Having said that, the capex required to install that equipment is significantly higher than for an equivalent fossil fuel plant. The maintenance costs are also greater, because of the need for physically larger furnaces and boilers and more materials handling equipment is required to move four to five times more fuel volume when compared to an equivalent fossil fuel plant,” he continues.

The bigger picture

Alternatives to biomass also come with their challenges. While the capital cost of converting to liquid natural gas (LNG) is lower, accessibility is questionable and the energy costs are high. More cutting-edge options – such as green ammonia, green hydrogen and transferring solar and wind energy into a tangible fuel pool – are some way down the track. Those looking to change need to consider what is available now.

Overall, Williams says that AES is fuel-agnostic and always aims to operate a plant as efficiently as possible: “Inefficient thermal combustion and energy plant operation has a negative impact on resource use and emissions. Our involvement results in a ‘more output for less input’ approach. A key starting point for clients to consider is that they get a 100% saving for every unit of energy that their process plants do not need to consume. Energy auditing is a good starting point.”

Evezard adds that companies can also look at some ‘low-hanging fruit’ or very accessible energy savings, by addressing the issue of equipment that is not insulated, the scheduling of how heat is used – and operational equipment which is not in production and on standby for days or hours.

However, it is sustainable sourcing of biomass which remains the greatest challenge. Locally, large paper companies have installed massive energy plants, impacting on the availability of biomass in significant parts of the country. Consequently, clients who secure their biomass supply early are most likely to benefit, leaving latecomers to find other options.

In addition to monitoring technology and supply developments, AES can leverage its almost 30 years of experience in implementing thermal combustion solutions to provide the best one for each client’s business, says Williams.

“We are in a unique position, where our substantial collective experience on projects and operations can provide a client with a technical solution and capex offering. We furthermore guarantee the project outcomes when it comes to performance, efficiency, output and emissions. At the same time, we can provide clients with a steam and boiler operations and maintenance service level agreement with ongoing performance guarantees.”