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Waste heat recovery

For many industrial and commercial sectors, waste heat minimisation and recovery offers the most significant single opportunity to reduce total fossil fuel consumption and improve energy efficiency. It can also mean lower maintenance costs and improved productivity of furnaces, ovens and boilers.

Generation technologies that harness waste heat, such as co-generation and waste heat to power (WHP), have the potential to produce electricity below the price charged by the electricity provider. These technologies reduce dependency on external energy inputs.

Companies should be aware of any forecasted increase in costs of fuels, such as natural gas, as this will affect the choice of fuel for new co-generation facilities.

Identify heat losses

Before implementing waste heat recovery technologies, it is necessary to identify heat losses common to heating equipment. These include:

  • flue/exhaust gas releases
  • air infiltration
  • wall conduction
  • radiation in existing furnaces, ovens, and boilers

System pipework and storages should be insulated to optimise their operation.

Maintenance and monitoring

Energy savings can be achieved by ensuring good maintenance and monitoring of the performance of heat recovery technologies and systems.

Monitor the performance of waste heat recovery technologies to ensure that you are optimising energy and financial savings.

Ensure the system is tested under a range of loads and in line with the manufacturer’s instructions.

Ensure a regular maintenance schedule is conducted in-house or by the equipment supplier.

Innovations

Wider application of waste heat recovery

The US Department of Energy has found many potential energy savings exist through the latest heat exchange technologies. Advances in construction have yielded equipment that can be used in environments previously too extreme.

Materials used in the construction of new heat exchangers have made them more resistant to corrosion. Advanced design has also made them more tolerant of higher temperatures and pressures. This means more heat from the process can be captured and utilised leading to energy savings.

An example of this is the manufacture of nitric acid or sodium hydroxide (caustic soda).

Low temperature waste heat recovery

Several new technologies are being developed to address opportunities for low temperature waste heat recovery and conversion. One possibility is to convert waste heat into electricity, normally to be consumed onsite.

One of the solutions to generate electricity from low temperature heat otherwise dispersed into the environment is the Organic Rankine Cycle (ORC). With plants available in a wide range of sizes, there are already a number of successful installations of ORC in cement, glass and metal sectors worldwide.

According to the Australian Institute for Refrigeration, Air Conditioning and Heating (AIRAH), the economics of heat pumps in the industrial context have improved due to gas price escalation, technology development and early stage economies of scale.

Waste heat as low as 45°C can easily be recovered by special heat pumps to produce output temperatures in excess of 100°C, suitable for commercial and industrial applications traditionally dependent on gas for heating.

Use of heat pumps may even prove a stepping stone towards complete replacement of boilers and steam systems in the long term. Research is underway to develop systems capable of more than 160°C.

Read more

Waste heat recovery case studies

Waste Heat Recovery: Technology and Opportunities in U.S. Industry (PDF 4.7MB)  US Department of Energy