Page 193 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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FIGURE 5.17 Blow-molding machine (Film)

5.5 Recycling of Bones

Bone recycling is a simple process where useful products can be extracted.
Minerals such as calcium powder for animal feed are extracted from the
bone itself. The base material for cosmetics and some detergent manufac-
turing needs are extracted from the bone marrow.
The bone recycling process passes through seven stages starting from
crushing and ending with packing. Figure 5.18 is a schematic diagram show-
ing the bone recycling process which goes through the following steps:

• Crushing: Bones are conveyed through an auger from the receiving
area to the crusher where bones are broken into pieces of about 10 cm
in length.
• Cooking: In the cooker, crushed bones are subject to saturated steam
supplied from a fire tube boiler via the steam line to cook bones with
fat and protein and kill any bacteria or pathogens.
• Centrifugal separator: In the centrifugal separator unit, bone mar-
row and fats are expelled out of a perforated tank leaving the crushed
bones in the bottom.
• Cooling: Crushed bones are cooled by circulating water in a cooler hop-
per. The circulating water is cooled in a forced draft-cooling tower.