Maximize condensate return, capture blowdown heat, and add flue‑gas economizers. The result: double‑digit cuts in fuel and water use, with paybacks often under a year.
In oil refineries, the cheapest energy is the energy you don’t waste. Condensate — the hot water formed when steam gives up heat — is essentially hot, distilled feedwater. Efficient steam systems typically recover 75–80% of it (www.scribd.com). Because condensate holds a high fraction of the steam’s sensible heat (often ~25% of the steam enthalpy — sensible heat is the temperature-related part of heat content) (www.scribd.com), returning it avoids reheating cold makeup water (replacement water added to the system).
The economics are clear. A Spirax Sarco analysis shows that a boiler evaporating 10,000 kg/h steam (8,400 h/yr) that lost all condensate would waste roughly £91,700 in fuel, £51,200 in makeup water, and £37,800 in wastewater charges per year — about 10.7 TJ (terajoules) of fuel and 84,000 m³ of water (www.scribd.com). Each 1% of condensate recovered would then proportionally save ~£1,800 in fuel, £512 in water, and £378 in effluent costs (about 840 m³ water and its treatment) (www.scribd.com; www.spiraxsarco.com). In practice, most refineries target >90% condensate return.
One case study from Indonesia (a fish‑feed plant) reported that implementing 100% condensate recovery via a flash tank (a vessel that depressurizes hot liquid to generate flash steam) raised boiler efficiency by 55.6% and cut both coal and makeup‑water demand dramatically — saving about Rp 25.3 billion/year (≈US$1.7 million/yr) with a one‑month payback.
Condensate return: energy, water, chemicals
Recovered condensate also reduces blowdown (necessary purging of boiler water to control total dissolved solids, or TDS) and chemical use. Because condensate is pure water, returning it means the boiler receives pre‑treated low‑TDS feed, allowing higher cycles of concentration (how many times dissolved solids are concentrated before blowdown). This cuts required continuous/shot blowdown and thus saves the heat and chemicals otherwise dumped (www.scribd.com; www.scribd.com). Industry guides emphasize these gains — for example, recovering the discharge from a single steam trap “can pay for itself in a remarkably short period” by avoiding makeup water, fuel and effluent costs (www.scribd.com).
Disposal of hot condensate often incurs effluent treatment costs or regulatory limits on discharge temperature (www.scribd.com; www.scribd.com). By contrast, unused condensate must be replaced by cold feedwater requiring full heating plus water treatment. In short, each kg of condensate reused saves the fuel that would heat that kg from ambient (~20–25 °C) to steam plus the water‑treatment such kg of makeup would need (www.scribd.com; www.scribd.com).
Returned condensate, when polished after heat‑exchange cooling, aligns with the goal of sending low‑TDS feed to the boiler (see /products/condensate-polisher). Reductions in treatment chemicals also flow through boiler programs (/products/boiler), and controlling cycles depends on accurate dosing hardware (/products/dosing-pump).
Blowdown heat recovery systems
Refinery boilers must purge water to control dissolved solids. Rather than wastefully dumping hot blowdown water (often >150 °C), modern systems recover its heat. Simple flash tanks (atmospheric or intermediate pressure) separate flash steam from blowdown; more advanced schemes use heat exchangers to preheat feedwater or deaerator water (a vessel that strips dissolved gases from feedwater) with blowdown condensate. Heat recovery from blowdown can capture up to ~70–90% of the thermal energy in the blowdown stream (michaelsenergy.com).
Michaels Energy reports that “up to 90% of the energy used to heat the blowdown water can be recovered as useful heat,” with project paybacks often <1 year (michaelsenergy.com). In a typical case (50,000 lb/h boiler at 80% efficiency with 5% blowdown), a flash‑tank + exchanger system could recover ~9.5 therms/hour (a therm is a unit of heat energy), about 0.81 MW, equating to ~$100,000/yr savings at $1.20/therm (michaelsenergy.com). Similarly, a 6 t/h oil‑fired boiler (10.5 bar) with 2% blowdown (~120 kg/h) will flash overall ~338 kg/day steam, saving roughly 7.7 tons of furnace‑oil fuel per year when that flash steam is returned (www.forbesmarshall.com).
Beyond fuel, blowdown recovery saves water treatment and reduces effluent. Captured flash steam displaces fresh steam demand, and heat‑recovered condensate reduces cold makeup needed. It also avoids regulatory problems: cooling blowdown to sewer can require large cooling water or violate discharge‑temperature limits. Surveys note that both flash economizers and heat‑exchanger blowdown recoverers often pay back in under a year (michaelsenergy.com; www.nationwideboiler.com).
Flue‑gas economizers (stack heat recovery)
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Flue‑gas economizers are heat exchangers on the exhaust stack that preheat feedwater. By extracting heat from stack gas (either above or below acid dewpoint), economizers can raise feedwater temperature by tens of °C, cutting fuel needs. Best‑practice installations in refineries and power plants typically lower stack exit temperatures by 50–100 °C. Natural Resources Canada notes that a proper economizer can reduce exhaust gas from ~135 °C to ~77 °C, lifting effective boiler efficiency from under 80% to nearly 90%.
In a controlled test, adding an economizer that cooled flue gas by ~103 °C increased a fire‑tube boiler’s efficiency from 77.23% to 84.55% — a 7.3 percentage‑point gain (www.researchgate.net). Typical practical gains are on the order of 5–8% efficiency (absolute); industry sources often quote up to 8% net fuel reduction by economizers (www.nationwideboiler.com). In one refinery study, heating feedwater from 147.8 °C to 150.7 °C cut fuel use by about 0.3% (www.researchgate.net).
Combined impact and payback metrics
Taken together, these measures — maximizing condensate return, installing economizers, and recovering blowdown heat — can cut a refinery boiler’s fuel and water usage by double‑digit percentages. For decision‑makers, the metrics are straightforward: each percentage point of condensate recovered yields proportional savings on fuel (e.g., ~£917/year per percent in the Spirax example — www.scribd.com) and water, while earlier Spirax figures also show ~£1,800 per percent in fuel, £512 in water, and £378 in effluent costs saved (www.scribd.com; www.spiraxsarco.com). Adding economizers avoids millions of Btu/h in thermal losses natural-resources.canada.ca), and blowdown recovery can save on the order of $100,000/yr for moderate‑sized boilers (michaelsenergy.com). In practice, payback periods for these investments are often just a few years or less (michaelsenergy.com; www.nationwideboiler.com). In dollar terms, a 5–8% improvement in boiler efficiency can save tens or hundreds of thousands of dollars per year in fuel for large units.
Sources: Data from industry case studies and guides (www.scribd.com) (www.scribd.com) (michaelsenergy.com) (michaelsenergy.com) (www.researchgate.net) (www.nationwideboiler.com natural-resources.canada.ca) (Spirax Sarco, Forbes Marshall, Michaels Energy, research literature, etc.). All values are drawn from these references.
