Tips for optimising condensate return systems in boilers

Condensate return systems are an often overlooked part of a boiler system that allows you to recover valuable BTUs within your system. The sole purpose of a condensate return system is to collect condensate from different points in the system and return it to the boiler to save energy.

But why worry about condensate return in steam installations? The use of a condensate return system in conjunction with boiler and boiler feedwater preparation improves efficiency and reduces costs in the following ways:

• The condensate has passed through the chemical treatment process in the boiler. Returning the condensate to the boiler or feed water reduces the total dissolved solids (TDS) in the system. It may result in less chemical treatment and may reduce the blowdown loss.
• When the condensate returns to the boiler or feed water system, its temperature varies from 54ºC to 104ºC depending on the duration of the return system and other factors. This return temperature is much higher than the average temperature of the feed water and make-up water (10ºC to 16ºC). As a condensate return system it can significantly reduce the amount of money needed to produce steam.
• Another benefit of a condensate return system is that it can reduce the amount of make-up water needed in your boiler. Helping to reduce your water consumption and improve savings.

How condensate return systems can be improved

• Vapour trap surveys

  The Condensate is discharged from the equipment through steam traps.. A steam trap simply allows condensate (condensed steam also known as water) to pass through while retaining (or trapping) the steam. This ensures that steam that has not yet given up its energy remains in the system while the condensate is removed.

  As you can imagine, a malfunctioning or incorrectly sized steam trap can wreak havoc on your condensate return system. A steam trap that has gone bad can be left open or closed. As one of the few moving parts in your steam system, it is important to perform regular inspections of steam traps.

  By ensuring that the steam traps are properly sized and function properly, you can keep your condensate return system running efficiently. A faulty steam trap can cause water hammer (noisy noises). The water hammer excessive will result in breakage of additional piping, hangers, valves and pipe fittings. Note: High pressure traps should be tested quarterly.

• Capture flash steam

  After the condensate passes through a steam trap, a pressure change occurs. This causes some of the condensate to become flash steam. This is another area where many companies may be losing money. If this flash steam is vented to the atmosphere, you are losing the valuable BTUs it contains. Instead, collect the steam in a flash vessel and use it to heat somewhere in the system. Also be sure to recover any condensate created when the revaporate gives up its energy and use that as well.

• Detect leaks and corrosion

  The condensate pipe has to deal with a higher concentration of carbonic acid than the rest of the system. This is because CO2 dissolves more easily in the cooling condensate. This can lead to corrosion of the steel which can eventually lead to leaks. Check your system for leaks and repair any that are found immediately to ensure that savings do not escape from your pipes.

• Insulate the pipe

  Insulation can normally reduce energy losses in a 90% and help ensure adequate steam pressure in plant equipment. Any surface above 48°C should be insulated, including boiler surfaces, steam and condensate return piping and fittings.

  The better you can help condensate retain its heat, the more efficient your system will be. That's why insulation is a no-brainer. It allows condensate to hold its heat longer, resulting in less work for the boiler and ultimately saving you money.

  Check your entire system and make sure all pipes are insulated. Repair uninsulated areas to ensure that you do not lose large amounts of heat as condensate returns.

• Return of contaminated condensate

  In some cases, there may be a risk of contamination if condensate returns to the boiler. If it is contaminated with corrosive liquids, for example, it is not suitable for boiler feed water. This is due to the dangers of foaming, scaling and corrosion.

  Condensate contamination detection equipment can detect changes in the conductivity of condensate. When a change in the desired conductivity occurs, sensors recognise that the condensate is contaminated. A controller then signals a discharge valve to open. This allows the condensate to flow to the drain or an economiser, rather than back to the boiler.

Example of guarantee of condensate return systems in boilers

Consider a steam system that returns an additional 10,000 euros per hour (e/h) of condensate at 82°C after distribution modifications. Assume this system operates 8,000 hours per year with an average boiler efficiency of 80% and a make-up water temperature of 13°C. The plant's water and sewer costs are €0.002 per gallon (€/gal) and the cost of water treatment is €0.002/gal. The fuel cost is € 8.00 per million Btu (€ 8.00 / MMBtu). Assuming a flash steam loss of 12%, * calculate the total savings.

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