Heat Recovery: the Unsung Hero on the Road to Net Zero

As the year unfolds, businesses and society alike face many challenges and uncertainty. The energy markets continue to remain volatile, with conflict in Europe having a marked impact on energy security around the globe. And, we are already seeing the effects of climate change, with unpredictable events occurring more and more. 

What is certain is that to achieve our universal aim of reaching net zero targets, a determined focus on innovation and action will be needed. Businesses are already taking the lead, realising that there is more to do, but less time to meet these goals.

Echoing the efforts of forward-thinking businesses, governments too are beginning to rise to the challenges ahead. This year sees the EEG 2023 come into force in Germany (an amendment to the Renewable Energy Sources Act¹). Its aim is for 80% of the country's electricity consumption to come from renewable energy by 2030, and for power generation to be virtually free of greenhouse gases (GHG) by 2035.

There is also a new German Energy Efficiency law currently being considered by the Federal Government². If passed, this would require companies that consume more than 10 Gigawatt hours (GWh) of energy per year to implement energy management schemes. Smaller companies using 2.5 GWh will have to conduct energy audits, whilst all companies must either avoid waste heat in production processes or use it themselves, if economically feasible.

It is not only Germany that views efficiency as critical to a potential net zero future. Last September, the Biden-Harris administration in the US published its Industrial Decarbonization Roadmap. As in Germany, around 30 per cent of industrial process heat requirements in the USA are accounted for by steam production.

Efficiency in Practice: Heat Recovery in your boilerhouse

A major benefit to focusing on efficiency is that it involves action, now, not tomorrow, and without major changes to infrastructure. The case for improving efficiency in steam systems could not be clearer. Steam remains vital to many processes and is the most significant end-use of energy in the industrial sector. However, in our experience, many businesses are not aware of the untapped opportunities to improve steam's efficiency.

At the core of any steam system is the generation of steam, and whatever your current fuel, that will most likely come from a boiler. All boilers witness continuous evaporation as part of their normal operation. This gradually increases the number of dissolved solids inside, which has to be managed to avoid damage both to the boiler and the connected steam system.

The usual way to deal with this is something called boiler blowdown. This is further divided into two categories: bottom blowdown (also known as intermittent blowdown), and continuous blowdown. Either method effectively blows through any unwanted deposits by releasing some of the boiler's capacity. Where this is treated simply as a necessary operation, with no attempt to recover the heat and water involved, it is a significant waste of energy.

But, particularly with the larger volumes involved with continuous blowdown, this energy may be captured and used. Naturally, the specific nature of a steam system determines the potential for recovery and energy savings, but even in a simple heat recovery circuit, the payback period could be as little as a few months.

Where more sophisticated circuits are developed (as in the diagram below), flash steam and blowdown heat are used to heat and deaerate the feedwater, annual savings can run into the tens of thousands. And that's against a modest investment.

Schematic diagram of a blowdown flash installation with receiver