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WATER & WASTE TREATMENT CUT BOILER OPERATING COSTS BY 95%


As industry battles with soaring energy costs, Steve Mines, sales director at SUEZ Water Purification Technologies, looks at the operational efficiencies that can be made by changing the way an industrial boiler is fed


holesale gas prices hit new all-time highs in the winter of 2021, bringing not only the collapse of several energy suppliers that had become familiar names to consumers but also leaving business – especially in power-hungry sectors such as steel, glass and chemicals – to battle with soaring gas and electricity costs. Those costs look set to remain high in 2022 and the alternative – to switch to more polluting fuels – is really no option at all either environmentally or practically, given that the cost of oil has also seen sharp rises amid surging demand and tight supplies.


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For a practical example of the challenge to businesses amid the energy crisis look no further than boilers, which are commonly used to provide heat and steam throughout industry and depended upon to produce large volumes of live steam in breweries, food and beverage production and chemical plants. For example, food and beverage manufacturers need a reliable quality of live steam in cooking, humidification and sterilising to ensure that the food and beverages we buy taste good and are safe to consume. So how do businesses who rely on such regular, high volume boiler output manage during the energy crisis when the cost of operating boiler systems are rising still further? One effective way to manage costs is to change the way that a boiler is fed, and to understand why this


can make savings, we need to look at a typical boiler feed.


Most industrial boilers use a simple demineralisation or softening system to treat supply water, and this is a perfectly adequate solution in applications where, for example, there is minimal requirement for live steam and condensate return, and where the source water is relatively soft or levels of total dissolved solids (TDS) are low. However, boilers with steaming rates over 8 tonnes/hour that are fed by a simple demineralisation or softening system can be prone to many problems that regularly require time and money to fix. These boilers are typically at an increased risk of scaling and fouling, requiring greater use of chemicals (adding to the plant’s carbon footprint) and frequent blowdowns, both of which are costly for the business in terms of energy and factory downtime. Also, depending on how the wastewater from the blowdown process is handled, there may also be the additional cost of discharging to drain, or of placing additional burden on downstream waste handling systems. What are blowdowns and why are they needed? The salt and mineral deposits that collect in a boiler reduce heat transfer and flow rate, reducing its efficiency, and will eventually block the boiler’s tubes. To maximise the efficiency of the boiler, minimise downtime and prevent failure, these deposits must be


removed with blowdowns (draining) to prevent the formation of solid precipitates. This is critical in plants that are situated in a hard water region as feed water will contain high concentrations of dissolved salts, which will in turn cause faster scaling of boiler tubes and pipework. Clearly, the higher the level of TDS in the feed water, the greater the required frequency of blowdowns. BS2486, the standard for boiler operation and safety, stipulates that the maximum TDS level is 5,000 mg/l for fire tube boilers and 3,500 mg/l for water tube boilers. Once these levels are reached a blowdown must be carried out to prevent foaming, wet steam and carry-over, and to eliminate the risk of boiler damage and the safety of operational staff. While that catalogue of potential problems may look daunting, the good news is that there is a way for production and process engineers to protect against the rising cost of running industrial boilers that use live steam at a steaming rate of 8 tonnes/hr or more, and that is to install a reverse osmosis water treatment system. This is a water


purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from feed water. This can enable the business to run the boiler system at a fraction of the original cost, and improve boiler safety and efficiency into the bargain.


For example, in a boiler with a minimal condensate return that provides live steam at a rate of 8 tonnes/hr, uses softened feed water of 350 mg/l and has maximum TDS less feed of 4,650 mg/l, we estimate the running costs to be as much as £54,096. But with the addition of a reverse osmosis water treatment system, providing a feed of <20mg/l and maximum TDS less feed of 4,980 mg/l, the estimated cost per annum would be as little as £2,880, a saving of £51,216 per annum – almost 95% – simply by installing a reverse osmosis system alongside an existing demineralisation plant. With gas market prices having hit a new all- time high of £4.50 per therm at the end of 2021 – about nine times higher than they were 12 months earlier – ever rising energy costs remain likely to spell trouble for factories and businesses throughout 2022. In this economic climate, a potential annual saving of as much as 95% on the cost of running a boiler makes the investment in additional water purification equipment for boilers with steaming rates over 8 tonnes/hour an attractive option, with a fast ROI. And in some circumstances smaller boilers can also benefit from a RO system, so it’s always worth talking to a specialist about your specific requirements.


SUEZ Water Purification Technologies www.suezwatertechnologies.com


MARCH 2022 | PROCESS & CONTROL 39


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