Industrial boilers: reduce OPEX, cut Carbon and boost productivity
Boilers, providing heat and steam, are used throughout industry. Where large volumes of live steam are essential, such as in breweries, food and beverage production and chemical plants, the cost of operating boiler systems can often be high – and with the rising cost of gas and oil, these costs are only set to rise still further.
Most industrial boilers use a simple demineralisation or softening system to treat supply water. In certain applications, for example, where there is minimal requirement for live steam and condensate return, where the source water is relatively soft or levels of total dissolved solids (TDS) are low, then a demineralisation plant can provide an acceptable solution.
For many applications, however, the reverse is true, especially for boilers with steaming rates over 8 tonnes/hour. The problems can vary, but typically include frequent blowdowns, with associated downtime and high fuel bills, an increased risk of boiler scaling and fouling, with greater use of chemicals, and the subsequent impact on your carbon footprint. Depending on how the wastewater from the blowdown process is handled, there may also be additional cost of discharging to drain, or of placing additional burden on downstream waste handling systems.
Do you need a reverse osmosis system for your industrial boiler?
Although every installation will be different, requiring a customised ROI calculation, it’s possible to apply several general rules to determine if a reverse osmosis (RO) system will improve the efficiency of your demineralisation plant and provide a realistic return on investment.
What you need to know:
- Boiler output: typically, this needs to be in excess of 8 tonnes/hour for an RO system to provide an effective solution (note that in some circumstances smaller boilers can also benefit from a RO system, so it’s always worth talking to our specialists about your specific requirements).
- Live steam: if a large volume of live steam is being used, with a low level of condensate return, then considerable quantities of make-up water will be required.
- Water hardness: if your source water is drawn from a hard water region, generally above 200 – 1500µS/cm, then it will contain high concentrations of dissolved salts, which will cause faster scaling of boiler tubes and pipework.
- TDS levels: BS2486, the standard for boiler operation and safety, stipulates that the maximum TDS level for fire tube boilers is 5,000 mg/l 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 damage to the boiler and the safety of operational staff. Clearly, the higher the level of TDS in the feed-water, the greater the frequency of blowdowns; TDS has to be measured in both the feed and make-up water.
Example calculation of cost savings
The following example and the figures used are intended only as a simple guide of how to calculate the possible costs savings from installing a RO system with an existing water demineralisation unit. If you would like to carry out an exact calculation of your water treatment system please talk to one of our specialists.
Calculation of Boiler Blowdown - assumptions:
- Live steam
- Minimal condensate return
- Steaming rate: 8,000kg (8 tonne/hr)
- Softened feed water: 350 mg/l
- Feed water: 500µS/cm or 350 mg/l
- Boiler maximum TDS: 7,000 µS/cm or 5,000 mg/l
- Boiler maximum less feed TDS: 4,650 mg/l
Cost with softener only:
- Concentration factor: 13.28 (4,650 ÷ 350)
- % Blowdown: 7.52% (350 ÷ 4,650 x 100)
- Volume of blowdown: 602 kg/hr (8,000 x 350 ÷ 4,650)
- Cost of blowdown: 4,508 tonne/annum @ £12/tonne
- Estimated cost per annum: £54,096
Cost with combined RO and softener, with an RO feed of <20 mg/l; boiler maximum TDS minus feed TDS: 4,980 mg/l
- Concentration factor: 249 (4,980 ÷ 20)
- % Blowdown: 0.4% (20 ÷ 4,980 x 100)
- Volume of blowdown: 32 kg/hr (8,000 x 20 ÷ 4980)
- Cost of blowdown: 240 tonne/annum @ £12/tonne
- Estimated cost per annum: £ 2,880
This calculation shows that potential savings of £51,216 can be made each year, simply by installing a reverse osmosis system alongside an existing demineralisation plant.
This is a significant amount and can make the investment in additional water purification equipment an attractive option, with a fast ROI.
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