Ways to save – Chemicals and plastics manufacturing
Ways to save
Optimise the use of existing equipment
A range of technologies are used in the chemicals and plastics manufacturing sector including motors, pumps and fans, air compressors, boilers, lighting and HVAC systems. Many plants have equipment that is used sub-optimally or is left on when not in use. Optimising the use of this equipment can yield energy savings for little or no cost.
Implement effective shut down procedures
Most manufacturing plants have energy overheads, such as energy-using equipment that is left on even when the plant is not producing anything. By analysing energy use in terms of the throughput, it should be possible to determine if energy use per unit produced (for example, kWh per tonne) is broadly consistent during the day, week or month. If it is not, then improving plant control can save energy.
Ensuring that all equipment is turned off when not in use is a simple way to reduce energy usage. PACIA has identified that one of the simplest energy savings has been switching off air-conditioning systems overnight and at weekends. Vinidex’s use of this measure at its O’Connor plant in Perth resulted in savings of $6,000 and 80 tonnes of CO2-equivalent per year.
Optimise operating temperatures and pressures
The percentage yield and rate of chemical reactions is highly dependent on temperature and pressure. It may be possible to achieve energy savings through reviewing the optimal temperatures and pressures for particular chemical processes.
Ongoing innovations in catalysts can lower the activation energy barrier for chemical reactions, which reduces the temperatures and pressures needed.
Energy savings can also be made by taking the following actions:
- Ensure chemical distillation is being carried out under optimum conditions and that the products are not being over-purified.
- Decrease processing temperature, optimise cooling temperature and set thermostats to an appropriate temperature – A one-degree celsius drop in average space temperature can cut fuel consumption by about 8%. Be mindful that storing polymer granules at low temperatures can lead to the formation of condensation when the granules are moved into a warmer factory space. This can result in greater drying requirements prior to processing.
- Monitor and adjust the pressure of equipment. Qenos reported through the EEO program – ‘The boiler feed water pumps produce a higher pressure than is needed to supply water to the furnace waste heat boilers. One of the boiler feedwater pumps is a steam turbine. Slowing the pump down will reduce steam usage by approximately 500 kg/hr while still having adequate supply pressure for boiler feedwater. There is no capital investment required. Labour/engineering costs to implement will be less than $2000 and deliver an energy reduction of 12,000 gigajoules and $30,000 per year in energy savings.'
Use advanced process control
Chemical and plastic process plants are complex and present an opportunity to minimise energy usage and maximise energy recovery through advanced process control (APC). APC is a systematic approach to enable dynamic optimisation of plant operations. APC involves installing hardware and software for capturing process operating data, analysing trends and developing strategies to optimise control of all relevant variables.
Organisations that have used APC include:
- Incitec Pivot Limited (IPL), who reported: ‘In 2008 IPL implemented advanced process control of its Ammonia Plant at Gibson Island. This project is saving approximately 0.1 GJ per tonne of ammonia manufactured or approximately 30,000 GJ per year. The project has also resulted in production gains of approximately 5 tonnes per day of extra ammonia by improving control close to process constraints.’
- Burrup Fertilisers Pty Ltd, who reported: ‘The cost estimation and payback calculations confirm that the payback period was within one year which will translate to annual energy savings of approximately 96,167 GJ. There is also an annual production increase of 3083 MT of ammonia, at an implementation cost of just over $300,000, payback period less than one year. The final scopes of works and implementation details of the project are currently in the development stages.’
Minimise heat loss from steam generation processes
One of the most common processes in industrial chemical plants is distillation to separate chemical mixtures. Significant energy is used in this chemical separation processes because large quantities of steam need to be generated. A substantial quantity of energy can be lost as heat through the production and distribution of steam requiring more energy to maintain boiler temperatures. Inefficient distillation and steam generation systems can also increase air-conditioning cooling loads.
Thermal insulation of pipes and taps and the replacement of defective steam traps are effective cost-saving measures in the distribution of steam. The amount of energy involved should also provide a strong incentive for minimising heat loss from boiler systems by insulating boiler valves, steam and condensate return pipes, and storage units.
Improve the efficiency of existing equipment
Motors systems are widely used in the chemicals sector to drive pumps, fans and air compressors. Because of their extensive use, they provide excellent opportunities for energy savings. It is also possible to cost effectively improve the energy efficiency of boilers and steam systems, as well as lighting and HVAC systems. The use of variable speed drives (VSD) can in some cases result in up to 50% energy savings with a three-year payback.
Optimising these technical systems, when coupled with best practice motor management, can generally deliver energy savings of between 30 to 60% cost effectively.
Maintain existing equipment
A large proportion of energy used by chemical companies is related to the operation of furnaces and boilers. The efficient use of this equipment depends on good control and regular maintenance to reduce energy wastage in steam distribution. Key maintenance tasks include:
Improve heat and power recovery
The use of heat recovery is very common in the chemicals industry. Many of the processes used in the industry require extreme temperatures and often need rapid changes in temperature.
Combined heat and power recovery technologies offer significant potential to improve the energy efficiency of existing processes at chemical and plastics plants.
Install more effective heat exchangers
A theoretical study by the US Department of Energy identified significant potential to improve the degree to which heat exchangers could recover more heat and energy from chemical processes.
Recent innovations in the construction of heat exchangers has enabled heat to be recovered from processes that were previously too extreme to deal with, such as very high temperatures and pressures, and chemically hazardous environments.
This has enabled more heat to effectively be captured and utilised in processes such as the manufacture of nitric acid or sodium hydroxide (caustic soda).
For more information
Invest in cogeneration
Energy assessments of the chemicals sector have shown the potential for significant energy savings from investing in cogeneration. Studies in the US chemicals sector have found that combined heat and power systems, such as cogeneration, could enable a 44% reduction in greenhouse gas emissions.
In Australia, Qenos has invested $45 million in cogeneration technology at its olefins site at Altona. This facility will meet Qenos’s electricity demand at that plant and will be capable of producing over a third of its steam requirements. This builds on Qenos’s company-wide efforts since 1995, which have reduced greenhouse gas emissions by 40%, largely through a focus on energy efficiency.
Recover waste heat and ensure boilers have condensate return
Energy and water loss can be minimised by using steam traps, which collect condensed water and return it to the boiler. This saves water and helps to conserve the heat of the water in the boiler, because the returned condensate is much hotter than feedwater and may not require treatment.
See the Process Heat, Boilers and Steam Systems technology page for more information.
Implement process innovation and equipment upgrade
Energy analysis and best practice case studies demonstrate that significant savings can be achieved through innovations in chemical manufacturing processes and upgrades to more energy efficient equipment.
Upgrade equipment to improve process efficiency
It is possible to significantly improve the overall energy efficiency of chemical and polymer processes through upgrading existing plant equipment.
Steam cracking for olefin production is the most energy consuming process in the chemicals industry, but significant energy reductions are possible. The use of state-of-the-art technologies, such as improved furnace and cracking tube materials and cogeneration using furnace exhaust, can save as much as 20% of total energy.
The remainder of the energy is used for separation of the ethylene product, typically by low-temperature distillation and compression. Up to 15% total energy can be saved in this process by improved separation and compression techniques, such as absorption technologies for separation. Catalytic cracking also offers the potential for reduced energy use, with a saving of up to 20% of total energy.
Consider alternatives to steam distillation
One of the most energy-intensive operations in the chemical industry is distillation separation. Most of the external energy and heat loss in distillation units occur in condensers, which are usually cooled by water or air. In many of the processes, a relatively few distillation columns and heat exchangers are responsible for the bulk of energy and heat losses. These losses could be minimised by improved heat integration, such as cooling the condensers with other process streams or by using waste heat to raise steam.
Another approach is to use alternative separation technologies such as reactive distillation and membrane separation:
Use solar thermal systems for water heating
Solar water heating is well suited to help save energy by preheating boiler feedwater in steam boilers for a wide range of chemical and plastic manufacturing plants. Boiler feed can be heated in solar panels up to 80ºC before being fed to the boiler.
For more information
Purchase and replace equipment with more energy efficient models
It is worth analysing whether there have been innovations in the core equipment used by your business. Over time, innovations often occur that substantially improve the efficiency of equipment compared to when you made your original purchase.
For example, polystyrene manufacturer Andpak (Aust) Pty Ltd based in Sunraysia, Victoria, has reduced energy use by 60% while also increasing production by more than 40%, through investment in more efficient moulding machines. The new moulding machines require significantly less steam than other technologies, requiring less energy to run.
Significant energy efficiency improvements can be achieved through the upgrading and replacement of many types of equipment and ensuring new equipment is correctly sized such as motors, pumps and fans, compressed air and lighting.
- US Department of Energy (2006) Chemical Bandwidth Study – Exergy Analysis: A Powerful Tool for Identifying Process Inefficiencies in the US Chemical Industry. US DOE ↩
- US Department of Energy (2006) Chemical Bandwidth Study – Exergy Analysis: A Powerful Tool for Identifying Process Inefficiencies in the U.S. Chemical Industry. US DOE↩
- US Chemicals Industry (2000) ‘Vision2020 Chemical Industry of The Future Technology Roadmap for Materials’. US Chemicals Industry↩
- Anastas, PT and Warner, J C (2000) Green Chemistry: Theory and Practice,OxfordUniversityPress:New York. Anastas, PT and Zimmerman, JB (2003) Design through the Twelve Principles of Green Engineering. Environmental Science and Technology 2003, 37(5) ↩
- Argonne National Laboratories (2001) Ethyl Lactate Solvents: Low-Cost and Environmentally Friendly. Argonne National Laboratories Office of Technology Transfer ↩
- See PACIA media release ↩