Drying of Containers in the Food and Drinks Industry - The Future

THE BACKGROUND

The modern production lines in the Food and Drinks Industry demand high speed drying which is quiet, energy efficient, reliable and easy to clean and maintain, whilst providing a level of dryness which is a challenge to the laws of aero-thermodynamics and physics.

Any lay-person will understand the drying problems encountered with wet, glazed surfaces in the washing-up process and the dewatering and demisting of vehicle windscreens.

In the industrial process, the time available for these drying operations reduces from minutes to hundredths of a second. With the increase in line speeds there is an increased requirement for a studied approach to container drying – it is now a specialist subject in its own right. Simply trusting to a crude compressed air or blower driven solution will not be enough as drying expectations increase.

THE CHALLENGES

An investigation of drying equipment on food and drink lines will show that there are already many different approaches to drying problems. A canning factory may have followed the principle of ‘cheap capital cost, forget the running cost’. Their lines are loaded with colourful plastic nozzles, downloading air at an uneconomic rate and creating noise and spray into the surrounding area.

True costs of such solutions need careful scrutiny.

A bottling line with moisture problems at the coder and labeller has powerful air knife systems installed at the pasteuriser exits, all of 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.

A company with drying equipment installed to overcome condensation problems finds the equipment loses its advantage as the containers move back through humid air on their way to 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 are now receiving attention with such 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 perform to stated levels of dryness levels set to avoid stress corrosion of can-pulls, rusting of crown caps and other failures which result in poor product quality and rejection of products by the supermarkets.

HOW CAN IMPROVEMENTS BE ACHIEVED?



Energy sources for drying can be 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 costs over compressed air costs by airknife manufacturers.

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. An additional feature 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 currently under development at Secomak Ltd to exploit the advantages of this technology. Atomisation of water from surfaces and suction removal to a 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.

CONCLUSION
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.