Monday, September 25, 2023
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Plant sustainability

Image Credit: Joseph Gage on Flickr (CC by 2.0)

Plant sustainability is a topic all on its own.

My opinion is this would centre on energy consumption, percent rework and percent of potential production. Every faucet of production requires energy, mainly electrical therefore efficiency in all of the drive systems for each device does affect cost per tonne produced. Getting them defined correctly for maximum required load, duty factor, motor size and ratings will lower costs per hour. Maximum production and minimum rework are goals that also greatly change the cost of tonnes produced. The major larger motor devices have the greatest impact and can more easily be reviewed and documented while the hundreds of smaller motors due add up to an impact level. Meeting the requirements of sanitation for petfood plants also have a cost and thus the plant design would also be of major importance also due to energy requirements to maintain the environment in each sector of production.

Monitoring, controlling and documenting critical process parameters fit in nicely having stated the above. Advanced production plants monitor everything and has an instant view of each device and its conditions are not unusual. In the case of motors heat, RPM, load would be a few which would allow notices of changes to prepare for possible replacement thus lower costs/increase profits by minimising downtime. Plant air filters, the fans blowing into or pulling through them will change motor load thus indicate filter load if you are not using air pressure sensors. We could outline multiple examples but some are noteworthy.

When your system is computer controlled and has all the monitoring systems you can see the flows from dry to liquid into the process. Having seen some issues in my time, when you see the pump delivery system fluctuate up and down you might have something to check, it obviously is searching for the set point but can’t hold it. A similar situation with a feeder screw from a loss in weight bin would not settle down. High RPM showed there was a blockage in the screw not allowing flow. Wonder where the missing screen piece for the screen went? Another note on feeder screws to a conditioning cylinder, if excess free steam is in the cylinder good chance over time some will escape back up the feeder screw. Check and clean on a schedule, build up changes the screws volume and capacity to convey.

Controlling a petfood system, it can be completely by hand or by computer control start to finish. Major comment on this topic from owners of petfood plants is that the computer control and monitoring system puts the plant back in managements hands. More predictable throughput hour in and out. Having worked in many plants of different control levels work but it is different for sure. Definitely by hand methods experienced operators learned what to do or more importantly what not to do! The effect however of non-computer controlled is the magnitude of rework. Let’s bypass the dry raw material section and make assumptions it is working OK and dust is not flying everywhere and separation exists from the production plant to this dusty area or the dust is contained or controlled. So basically, we have a dry ingredient stream, various liquid streams, steam, water both to multiple locations, fat, meats and other possibilities. How much waste of each do you think you might have if you did not control each with flowmeters with timing sequences etc. for this process? How many product changes per week? Well, the answer is most every new system is computer controlled to meet the demands and to be substantiable in this industry. In short, these systems pay for themselves in controlling the process and greatly reducing rework while keeping capacity up or give you a reason why it dropped.

Critical Control Process Parameters can cover many areas. Production, plant, emergency and many other topics which require a specific process. When you get down to it, they all relate to product quality and production. Everything needs to be working in unison to achieve the top end of production goals. Loss in Weight, liquid flow meters and timing allow for preconditions in today’s standards where there is virtually no waste out of the system including free steam. All is timed to begin as needed and the possibilities exist to monitor the material between the conditioner and extruder barrel for select parameters. Temperature mainly, with 77OC being the minimum for salmonella control. Same exit the extruder barrel but usually a bit higher temperature is desired. If all bacteria, moulds and spores are to be eliminated then about 125OC in this area. Note this can be controlled where the extruder temperature can be adjusted by controlling the system accordingly. Heat liable ingredients can thus be incorporated if desired in many cases. However, in making these changes the actual capacity of the system will most likely be lower due to the reduced load, moisture level increase, die open area and other changes associated with reducing temperature in the extrudate. Obviously, the last critical control point is the product in the bag. There are systems now that remove human contact from the product by using advanced monitoring and sample collection gear. Grabs samples convey to a testing unit and confirm the nutritional values by NRI, report density and moisture all on line in real time. Usually, a plant wide system where raw materials and samples mid line or select spots as before the dryer and after are taken as well.

Dextrinising, how is this associated with petfood production? Dextrinisation in our case is the reaction to starch by dry heat. It can happen when the extrusion process gets so hot and a bit on the dry side. Much like cookies, crackers or toast in the morning a slight burnt flavour due to oven use. Honestly back in the day it was felt/ noted that cats like a bit of this effect, much more then dogs. A system can be controlled to do this or to avoid this effect. One of the control points in petfood production. Systems exist to allow for production of a kibble or piece and then carefully set and dry in an oven like setting to develop textural and taste qualities.

Article contributed by Joseph P Kearns, Editor, International Petfood Magazine


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