Dryer For Mango Waste

January 12, 1999
Rev. February 2009

Vincent is currently manufacturing a small rotary drum dryer that is destined for the interior of Venezuela. It will be used to convert mango waste into a dry animal feedstuff. This will be done at a small plant that produces aseptic drums of mango puree from a plantation of 15,000 trees.

The waste, 40% of the delivered fruit, consists of peel and seeds. The material is quite nutritious; however, it spoils rapidly unless the moisture content is reduced to about 10%.

Prior to drying the waste, which has about 80% moisture, it will be shredded into small particles. This will improve the heat transfer within the dryer, allowing quick and uniform drying.

The dryer is a triple pass unit with a full rotating outer drum. The burner is specified for natural gas, with complete safety and operating controls. The furnace is a carbon steel shell lined with refractory fire brick. The mango is conveyed through the dryer drum by the hot gases from the furnace. The dried material is separated from these gases in a separation chamber located at the drum discharge. An induced draft fan draws gases and mango through the dryer and separation chamber.

The mango waste can be sticky, and there is a danger that it will stick to hot metal as it enters the first pass of the dryer. When this happens to a material it can dry out completely and begin to char. To prevent this situation from occurring provision has been made to blend some dried mango waste into the wet material being delivered from the puree extraction building. It is expected that the mixture of wet and dry material will lose its sticky nature and pass through the dryer in a proper manner.

The capacity of the dryer is small, only 2,500 pounds per hour of water evaporation. This will allow converting approximately 3,000 pph of mango waste into 650 pph of dried animal feed.

Selection of the equipment for this plant started with an inquiry for a screw press. It was hoped that a press would remove the moisture from the mango waste. An experiment was run in which lime was added to the waste, following the steps in Dan Vincent's 1940 patent. We found that, while lime breaks down citrus peel so that it can be pressed, it has no such effect on mango peel.

[February 2009 The use of this dryer was rapidly abandoned. Even in a country with fuel oil as cheap as it is in Venezuela, the cost of fuel exceeded the value of the animal feed which was produced. The experience helped Vincent decide to get out of the dryer business in 2007.]

Issue 88