The future of container drying
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The modern production lines in the Food and Drinks Industry demand high speed drying which is quiet, energy efficient, reliable, easy to clean and maintain, whilst providing levels of dryness that challenge the laws of aero-thermodynamics and physics.
Lay persons will understand the drying problems encountered with wet, glazed surfaces in the washing-up process and dewatering and demisting of vehicle windscreens.
In the industrial process, the time available for these drying operations reduces from minutes to hundredths of seconds. Increasing line speeds require a studied approach to container drying, it is now a specialist subject in its own right. Simply trusting to crude compressed air or blower driven solutions will not be enough as drying expectations increase.
The challenges
Investigations of drying equipment on food and drink lines show that there are many different approaches to drying problems.
Canning factory may have followed the principle of ‘cheap capital cost, forget the running cost’. Lines are loaded with colourful plastic nozzles, downloading air uneconomic rates, creating noise and spray into the surrounding area. True costs of such solutions need careful scrutiny.
Bottling lines with moisture problems at the coder and labeller have powerful air knife systems installed at the pasteuriser exits, which are either stopped or lifted out of the way due to individual bottles being knocked over on the conveyor. Container handling is an essential part of the modern drying system.
Companies with drying equipment installed to overcome condensation problems find the equipment loses its advantage as the containers move back through humid air towards the next operation. Maintenance of suitable ambient conditions surrounding the containers is essential.
Drying equipment manufacturers scratch their heads and ponder the request from their customers ‘for completely dry’ containers.
Drying specifications now receive attention with developments as the Can Manufacturers Code for dryness and the Brewers and Licensed Retailers Association Code for crown caps.
The new evolution of dryers will have to achieve levels of dryness set to avoid stress corrosion of can-pulls, rusting of crown caps and other failures which result in poor product quality and product rejection by retailers.
How can improvements be achieved?
Energy sources for drying are compressed or blown air, or a combination of both, with heaters and air driers also playing their part.
Compressed air emerging from drilled holes has given this energy source a bad name, not helped by extravagant claims for blown air over compressed air costs.
There are many specific advantages of compressed air. Rapid response with true ‘supply on demand’ capability, energy efficient high-gain Coanda air amplifiers such as ringjets and focused drying onto problem areas of modern container shapes are all in the compressed air armoury.
Additional features of compressed air is its ability to be conditioned to ‘desert dryness’ as it combines with ambient air. This produces unique drying ability, particularly to water films and condensate.
A new concept of ‘psychrometric drying’ is under development at Secomak Ltd to exploit the advantages of this technology.
Atomisation of water from surfaces and suction removal to drain for recycling are also compressed air capabilities.
Blower driven air knife systems lead the way in overall surface drying, but need to balance energy and noise requirements. Optimisation of current systems with a focus on airknife and impeller design using computational fluid dynamics (CFD) will build on the use of the latest high-speed motors using ceramic hybrid bearings.
Belt free transmission from motor to impeller is already available to reduce maintenance requirements. New approaches will enable manufacturers to meet tougher noise legislation and further energy initiatives. Blower systems need to follow the technology of ‘intelligent control’ which is already used in the compressor industry.
Drying is at an interesting and exciting stage and will need to rise to the challenge of the requirements of the food and drinks industry as it expands and develops in the twenty-first century. Secomak is at the forefront of this applied research and offers optimised solutions for dryness, noise, environmental impact running and capital cost.
Authors
David J Dell is product development manager at Secomak Ltd and senior lecturer in aerodynamics and acoustic engineering at the University of Hertfordshire.
Further information
Secomak Ltd
Email: info@secomak.com
Website: www.secomak.com
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