Industrial boilers and the energy crisis

The wholesale cost of energy in the UK has risen dramatically in recent months. Gas prices have increased by over 400% due to strong global demand, at a time when supplies from major producers such as Russia have been cut. This has coincided with a number of other factors, such as the series of outages in electricity generation, including a major fire in the main IFA1 connector cable trough from which we import energy, plus low wind speeds for most of the year across Europe that have reduced the contribution from wind turbines. All of these factors are placing far greater demand on gas-fired power sources.

We’ve already seen the impact that rapidly rising energy costs can have, with smaller suppliers going out of business and the temporary closure of two fertiliser plants, creating a knock-on effect on the supply of CO2.

According to most industry forecasters, record energy costs are likely to be with us for some time, with continuing high levels of global demand, anticipation of a cold winter and an energy infrastructure that lacks sufficient resilience to provide the flexibility needed to meet both short and long-term fluctuations in demand.

The cost of boiler feedwater
Few industrial companies will have been immune from the effects of rapidly rising energy prices. For those that rely on large volumes of hot water and the use of live steam for their production processes, the situation is particularly acute.

Large industrial boilers – essentially anything generating more than 8 tonnes of steam per hour – use considerable amounts of energy. Although much of this is lost in the conversion to live steam, there are ways in which energy consumption can be significantly reduced. This is especially true for companies in regions of hard water or with high levels of total dissolved solids (TDS) in their water sources.

Typically, raw water sources used for supplying industrial boilers use some form of softening system to treat the water prior to heating. Although this can be effective in reducing the risk of boiler scaling it will not reduce TDS levels; indeed, softening can actually increase the concentration of dissolved solids. These can include inorganic salts, such as calcium, magnesium, potassium and sodium, plus carbonates, nitrates, bicarbonates, chlorides and sulphates.

The concentration of TDS in pressurised steam will cause bubbles in the steam to become increasingly stable, so that they fail to burst as they reach the surface of the water within the boiler. Depending on the pressure, boiler size and steam load, these bubbles can rapidly form as foam, which will then be carried over into the main steam lines. This carryover is both extremely wet and contains high concentrations of impurities, which will subsequently contaminate downstream pipework, heat exchangers, valves and steam traps.

There is a direct correlation between the purity of boiler feedwater and the number of boiler blowdowns required. Blowdowns are essential to remove impurities and maintain the efficiency, operating life and safety of the boiler, but at the same time add to operating costs as they waste heated water and energy.

It’s not unusual for blowdowns to consume around 10% of heated boiler water and for them to be carried out at frequent intervals. Each blowdown can therefore increase energy consumption by around 10%.

Boiler feedwater purification
The solution is to improve the quality of the boiler feedwater. Although this will require investment in additional water purification equipment, the payback can be remarkably fast. Even in times where energy prices are stable, payback can often be within months. For example, the blowdown costs for a standard 8 tonne/hour boiler in a live steam application with just a softening system in place, could be reduced by more than £50,000 p.a.

At a time where energy prices are rising fast, and look set to remain high, taking a fresh look at the potential savings from a simple improvement in boiler feedwater quality makes considerable sense.