The opportunities outlined for process heat focus on strategies that are broadly applicable across a wide range of process heating and steam system applications.
Many of them apply to assessing or optimising an existing system, as well as planning a new system.
For information on types of process heat and steam systems, see Technology background – Process heat, boilers and steam systems.
Reduce demand for process heat and steam services
Reducing requirements for process heat and steam services can involve a number of measures. These include minimising the amount of material to be heated through product design, managing reject rates and controlling the equipment transporting the item are some of the strategies which can be implemented. Consideration should also be given to whether greater precision can be applied in the heat process and management of heat loads. There are also alternatives to using heat and steam, particularly in chemical processes that could be investigated.
Some examples of opportunities in this area are outlined below.
Reduce the amount of material to be heated
If manufacturers can provide the same service or product through light-weighting of materials, they can reduce the amount of heat used per unit of product and possible material costs.
Minimising reject rates also reduces waste and wasted heat loss by reducing the heating needed to deliver a given quantity of saleable product. Reducing reject wastage (of defective goods) reduces the total amount of material processed, as well as avoiding wasted time, labour and energy. This may also reduce the frequency of production-line stoppages, cleaning and maintenance. It is worth noting that improved control of energy and material flows can help to reduce variability of production and therefore scrap rates.
In many cases, items to be heated are carried on conveyor belts or trolleys, or in containers. When heating the product, this conveying equipment is also heated. Reducing its mass, subject to feasibility, cuts heating energy requirements and can also shorten processing time.
Apply heat with greater precision
Accurate targeting, timing and control of heat application minimises the amount of heat needed. It may also allow for the downsizing of equipment and improvement in product consistency and quality. Microwave heating, lasers and infrared radiant heat are examples of technologies which can enable this.
Examples of how these technologies have been applied include the use of microwave technology:
- To apply heat to dewater fine coal particles in Australia; and
- For energy-efficient heating in high-temperature brazing in the United States.
Combining application of heat with other technologies can also reduce heating requirements. For example, depressurisation can be used to evaporate liquids at a reduced temperature. Reducing the amount of material to be heated can also make precision heating solutions more feasible.
Implement a load management strategy
A load management strategy for bringing the right-sized boilers online and offline to match the required loads can greatly increase energy efficiency. The required steam loads on a site can vary over time. On sites with several loads and boilers, fewer boilers operating at higher loads is generally more energy efficient than all boilers operating at lower loads.
Most boilers reach peak efficiency between 60–90% of load. Boilers with large standby losses, caused by insufficient insulation for example, will lose about the same amount of heat regardless of load and are therefore significantly more efficient at high loads. Boilers with small radiation heat losses are relatively more efficient at lower loads.
Favouring the most efficient and appropriately sized boilers assists in maximising energy efficiency. Intelligent control technologies can be used to automatically select the boiler and adjust the fuel feed to match the load. Simpler methods, such as shutdown timers, can also be used to take offline the boilers that become unloaded.
Consider using alternatives to lower heat and steam requirements
Many existing technologies demonstrate that it is possible to move beyond the use of heat to drive chemical and industrial processes.
Commercialised examples include:
- Enzyme-based detergents that operate at lower temperatures
- Manufacturing components using plastic composite materials instead of metals
- Ionic solvents
- New catalysts and fluxes that reduce the energy required to drive chemical processes or clean surfaces
- The use of pre-painted materials.
Specific examples include:
- Cement – Geopolymer cements can be used for many purposes for which standard Portland cement is currently used. Portland cement manufacture requires processes that reach over 1000°C. However, geopolymer cement can be made using waste streams at room temperature and has no need for industrial process heating.
- Organic fertiliser – Nitrogen-based artificial fertilisers are made through processes which require high temperatures (300–400°C) and pressures (200–300 atmospheres). Ammonia requires at least 28 GJ per tonne to produce. Conversely, organic fertiliser can be made with no external heat or energy sources, through vertical composting unit technologies, which utilise heat generated naturally from organic decomposition.
It is also possible to use alternative industrial processes to steam to deliver the same product while expending less energy. For example:
- Replacing steam with hot water where appropriate will reduce energy consumption by lowering the boiler water output temperature and reducing losses associated with managing high pressure steam.
- Recycling content in material manufacture contributes to energy savings because recycling processes can be run at lower temperatures compared to the full-cycle processing of raw materials.
- Optimising the water content of bricks before kiln-firing has been shown to significantly reduce the amount of heat and time required for the process.
Improve the efficiency of existing process heat systems
The energy efficiency of existing process heat systems can be improved through efficient heat production, heat containment (reducing heat losses), ensuring efficient heat transfer and increasing heat recovery.
Heat losses from distribution and transfer equipment can generally be managed and reduced. In some cases, shifting from centralised to decentralised heating equipment can also be advantageous.
Some examples of opportunities in this area are outlined below.
Develop and use system energy models
Using an energy-mass balance model, quality process data and thermodynamic analysis techniques such as pinch analysis can help understanding of how the system works and identify opportunities to optimise performance. This is essential if large savings are to be captured, as energy waste at several points in a system can multiply its impacts, and complex feedback mechanisms can amplify energy waste. Restricting the scope for marginal improvement in single steps of the process will fail to capture the full potential benefits.
For example, many heating processes drive chemical reactions or phase-change processes that require little or no net energy. In other cases, heat drives chemical processes where the theoretical chemical energy requirement is much less than the typical amount of process energy used. For example, calcining alumina typically uses 3–5 GJ per tonne, yet the theoretical chemical energy requirement is only 0.5 GJ per tonne.
Comparing results from energy system models to real data can be very productive, as it helps to improve understanding of the fundamentals of the process, and to calibrate the models.
Pinch Analysis and other analysis techniques are outlined on the Energy Efficiency Assessments page of the EEX website.
For more information
Energy Savings Measurement Guide 2013 (Opens in a new window)
- Department of Industry
This guide provides detailed and best practice guidance on how to estimate, measure, evaluate and track energy efficiency opportunities. It provides in-depth information on capturing energy data, establishing an energy baseline, developing an energy mass balance, analysing potential energy efficiency opportunities and monitoring the performance of implemented energy efficiency initiatives. The resource was developed for large energy-using organisations, but the tools can be applied across multiple sectors and organisation sizes.
Use a whole of systems approach
All options to improve the efficiency of process heat systems should be considered as part of a detailed energy efficiency assessment. Each opportunity varies in its savings potential and payback period. These include:
- Efficient combustion of other heat generating equipment
- Increased heat transfer from heat sources, e.g furnaces and kilns
- Strategies to reduce heat losses
- Flue gas heat recovery
- Measurement, controls and process management
- Process models and design simulation
- Reduction in non-productive loads.
In addition, there are many technologies used in process heat systems which themselves can be made more energy efficient.
For more information
Optimise the use of a range of enabling technologies
There are a wide range of generic technologies used in process heat and steam systems which can be optimised. Common technologies used in process heat auxiliary systems include motor systems, pumps and fans. Technologies used in material handling systems that move product through heat related processes include conveyors, trolleys and pipes.
For more information on how to optimise these, see the EEX Technology pages for Motors and Motor Systems and Pumps and Fans.
Improve the efficiency of existing steam systems
The energy efficiency of steam systems can be improved by improving the efficiency of boilers and the reticulation system, point of use equipment and control systems used throughout the process.
There are many strategies to improve the efficiency by which steam is generated from boilers, such as:
- Identifying and repairing steam leaks and checking for gaps in insulation
- Optimising water treatment and total dissolved solids control to minimise blowdown
- Using steam traps and condensate return systems to reduce water loss by collecting condensation and returning it to the boiler
- Investing in blowdown heat recovery as the blowdown water contains significant energy that can be recovered
- Investing in heat recovery more generally. For example, heat loss from flue gas usually represents the largest source of inefficiency. Flue gas can be redirected into either an economiser, which transfers heat to boiler input water, or a pre-heater, which transfers heat into the boiler input air.
- Investigating opportunities to reintroduce flash steam, which is created when blowdown occurs. If the blowdown stream is directed to a flash steam vessel, it can be recovered for low-pressure steam applications or sent to the de-aerator
- Investing in boiler and burner management control systems
- Using digital combustion controls and oxygen trim
- Investing in variable speed drives for combustion air fans and coolant pumps
- Using solar thermal systems to pre-heat water before it enters the boiler
- Improving communication between the boiler room and operators.
Advances in chemistry, materials science and engineering, as well as the capacity to manipulate substances, means it is increasingly possible to either eliminate some heating processes or carry them out at lower temperatures.
Technical innovations include the use and production of enzyme-based detergents, micro-filtration, centrifuging, new catalysts and fluxes. Using non-metal materials, such as plastics and composites, in manufacturing processes is also reducing the need for high temperature production processes.
Computerised design and the use of new materials, including alloys and composites, are offering potential opportunities in the future to improve the efficiency of process heat and steam systems through better insulation, heat recovery and the internal lining of pipes and process heating hardware.
Cheaper sensors and smarter control systems also offer potential to improve the management and optimisation of heating processes.