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Finding Opportunities to Reuse Flash Steam

The plumes of steam that are sometimes visible at food and beverage manufacturing plants can signify good news for manufacturers. The escaping energy these plumes represent can be captured and effectively recycled into the manufacturing process to achieve significant energy and water savings.

Key points:

• Flash steam is an unavoidable by-product of some manufacturing processes. It occurs when condensate is discharged through steam traps from a higher to a lower pressure.
• Manufacturers should initially take steps to identify where controllable steam losses occur and whether any loss can be avoided through maintenance, eg of steam traps.
• Once controllable losses have been eliminated, manufacturers can consider taking steps to recover energy, water, or both.
• On average, 10% of energy is lost through unavoidable steam plumes, this can represent a significant saving if flash steam is captured and re-used.
• If you need assistance in identifying your controllable losses from your unavoidable losses, reach out to a steam system specialist to assess the process improvements available to you.

Before taking steps to try and recover steam, it’s important that food manufacturers understand why they are experiencing steam loss. With this awareness, they can take steps to deal with preventable losses and/or choose to recycle energy from losses that are a natural part of the food production process. Within a food processing facility, steam losses can be divided into controllable losses and unavoidable losses.

• Controllable losses – These are ‘hidden’ losses, normally caused by a fault in the system, such as a malfunctioning steam trap or safety valve. A rigorous maintenance regime will help to minimise ongoing controllable steam losses. It is not practical to capture a controllable loss as it can often be eliminated by undertaking a simple maintenance procedure.

   

• Unavoidable losses ­– These are inherent losses in the food production process, caused by condensate moving from an area of high to low pressure, a natural part of any steam using process. This steam is known as flash steam. Although it is not possible to prevent this energy loss, it can be recovered and recycled to achieve savings through a reduction in fuel and water consumption.

Undertaking a steam trap survey

When aiming to optimise a steam system, it’s vital first locate and identify the controllable steam losses. A thorough survey, undertaken by a steam specialist, will give a clear picture of how the steam system is operating. From here, decisions can be taken to either undergo a maintenance regime to prevent controllable losses or prioritise the capture and transfer of flash steam back into the manufacturing process.

Recycling flash steam is not uncommon: as an inherent by-product of food and beverage production, flash steam occurs in processing plants across the industry. Flash steam occurs when condensate is discharged through steam traps from a higher to a lower pressure. This drop in pressure means some of the condensate re-evaporates, resulting in plumes of flash steam.

The benefits of recovering flash steam

Given that flash steam has an energy content and also represents lost water, a simple calculation can highlight significant savings. On average, around 10% of the mass of water used in the process is lost through flash steam. Furthermore, with the latent heat required to convert water into steam, over 50% of condensate energy can be lost to flash steam.* This means a much larger proportion of the residual energy content of the condensate is lost through flash steam when compared to the mass of condensate discharged by the process.

When a food manufacturer is considering the recovery of flash steam, an engineer will assess and understand the manufacturer’s processes in order to locate where this spare energy – as it should be considered – could be optimised in the production process. They will be able to identify synergies between the availability of flash steam and energy demands around the plant. This requires application of the correct technologies to maximise its re-use. With food manufacturing requiring a large volume of hot water, this can provide an ideal heat sink for most producers!

While flash steam is unavoidable, there are clear benefits to its recovery. To maximise the recycling process, manufacturers must be clear about where losses are occurring in the system, understand the steps they can take to control any unavoidable losses, and identify where in the system flash steam can be best re-used to achieve the fastest return on investment!

Want to learn more about this topic? Listen to Episode 2 of the Talking Steam: Focus on Food podcast 

* While only 10% of water mass (condensate) discharged from steam traps is lost as flash steam, the energy required to achieve the phase change from condensate to flash steam represents a significantly higher proportion of the total energy content available. In this case, 10% of the water mass lost can contain over 50% of the total energy available in the condensate – making it a worthwhile focus for capture and recycling into the system!