Uses of Shell Products
The more important uses for nut shell products, together with their specifications for particle size, are shown in Table 1.
Table 1.—Uses for ground nut shells and fruit pits
+————————————————————————+——————————+ | Applications | Size | | | | | Deburring, cleaning, burnishing and polishing | | | in metal stamping, electroplating and | No. 10 to No. 50 | | plastics industries | | | Soft-grit blasting | No. 10 to No. 30 | | Fillers for plastics and plywood adhesives | Finer than No. 100 | | Insecticide diluents and carriers | Finer than No. 140 | | Explosives | No. 10 to No. 100 | | Fur cleaning | No. 10 to No. 100 | | Poultry litter and mulch (almond and peanut) | 1/4 to 3/4 inch | | Fillers for fertilizers (almond and peanut) | Finer than No. 20 | +————————————————————————+——————————+
Experience shows that no matter how nut shells or fruit pit shells are ground both under- and oversize particles will be produced. The hard, friable character of most of the nut shells makes their reduction to fine size particles less difficult than for tough materials, such as corncobs, or fibrous materials such as woods. Shells from almonds because of their bulk and very fibrous nature are somewhat less convenient to handle than other shells. Good business practice shows that sales outlets should be found for each fraction so that grinding expenses can be kept at a minimum.
Because there are some differences in physical characteristics of nut shells and fruit pits all shell products do not necessarily meet the same specifications, nor have the same uses.
Industrial Cleaning and Finishing
Oil, dirt, corrosion products, stain, paint, grease and the like can be removed from metal surfaces by air-blasting with soft grits prepared from shells of walnuts, pecans, peach pits, and similar residues. This method was developed originally for the Navy to use grits from corn-cobs for cleaning aircraft engines and parts. The method is inexpensive and foolproof because surfaces are cleaned without change of dimensions. No pitting or abrasion, such as produced by sand blasting, occurs. The method is particularly useful with mild steel, nonferrous metals, alloys, and parts that must be maintained at close tolerances. Modifications of the blast method are used in finishing molded plastics, metal die-castings, and machined parts. One manufacturer of precision instruments states that his company saves $100,000 a year in finishing parts with shell grits.
Many stamped metal articles and molded plastics are deburred, cleaned, burnished, and polished by tumbling in drums containing shell grits. Various grades of grits are required depending upon the nature of the pieces being finished.
Fillers for Plastics and Plywood Glues