Heat Regeneration Should be Key Consideration
Many industrial processes require energy, but only a portion of that energy input is used for each operation such as pasteurisation or evaporation. Unused energy is wasted, but by using heat exchangers, it is possible to recapture most of this untapped energy through waste heat regeneration.
At HRS when we talk about heat regeneration, we mean the recovery of as much surplus heat (or cooling capacity) as possible after the primary function of the heat exchanger has been performed. ‘Recovery and re-use of industrial waste heat is an attractive concept that could simultaneously reduce energy costs and CO2 emissions.’¹
Given the importance of energy efficiency in reducing the use of fossil fuels and greenhouse gas (GHG) emissions, it can be argued that it is imperative to employ heat regeneration and recovery at every opportunity. As at least one paper has pointed out, ‘The use of excess heat could also be important to improve the economic and climate footprint feasibility of new processes… by avoiding the addition of new heat production capacity.’²
Benefits of Heat Regeneration
Heat recovery improves the energy efficiency of heat exchange processes, and so the greatest and most obvious benefit of heat regeneration (recovery) is that less energy is required for a particular heating or cooling operation. This obviously provides financial benefits but is also better for the environment compared to systems without heat recovery.
Repurposing recovered heat can also reduce the amount of heat required for certain processes. For example, if a material is pre-heated with recovered heat, then it may be possible to complete the necessary heating (for example for pasteurisation) using hot water from another source or part of the factory, instead of requiring a dedicated boiler to provide the necessary temperature rise.
By increasing the energy efficiency of the heat transfer process, heat recovery can also make it possible to reduce the size of the heat exchange equipment required or reduce the necessary processing time.
To determine the potential value of waste heat, and therefore determine what it can be used for, it is necessary to know a number a parameters about the process temperature, the product and heating (or cooling) medium being used, and the performance of the heat exchange process in terms of heat transfer area and flow rate, for example. It is therefore important to consider energy regeneration or recovery as early as possible. Heat recovery systems can be retrofitted to many processes, but their design is often a compromise and retrofitted solutions may involve excessive pipework and other connections.
It is also important to note that not all sources of waste heat, particularly those at low temperatures, may not be suitable for heat recovery or waste heat utilisation. Online calculators are available or any reputable heat exchanger designer or manufacturer will be happy to provide advice on what is feasible. The amount of time that a process runs for will also have an effect on the viability of any project; processes which run for longer periods will be more attractive for heat regeneration.
¹ The potential for recovering and using surplus heat from industry. Final report for DECC, 2014.