Spices are normally ground in closed circuit with vibrating screens to meet a wide variety of particle size specifications. Some grinding mills such as high-speed comminutors are equipped with screens through which the material must pass, but the selection of a screen to meet the required specification usually results in producing an excessive quantity of fines. Single-pass grinding is also inefficient in terms of power consumption and most mills are capable of higher capacity when operated closed circuit with an efficient classifier. Air-swept fixed beater, double roller, cage and hammer mills are all used in spice reduction and any one plant may find it necessary to operate with several types because of the different grinding characteristics encountered when processing a wide variety of spices.
METHOD AND RESULTS
Most spice plants use a grinding circuit for several spices and the equipment must be designed and arranged for quick and complete cleanup and possess sufficient flexibility to handle a wide variety of grinds. For example, Savory is ground in high-speed comminutors to produce a final product that will all pass a 4 mesh ( opening 0.2023") screen. A 10 HP comminutor is the size most frequently used in spice plants and it would be fitted with a 3/8" diameter perforated screen when grinding Savory. Mill output is directly fed by gravity to a single-deck Kason Separator equipped with a 4 mesh screen. Oversize is recycled to the mill and -4 mesh product is received in drums for transfer to the packaging department. The arrangement described will produce approximately 1000 lbs. per hour of finished product and since recycle avoids over grinding the product is relatively free of fines. Nutmeg, Mace, Pepper, Cloves and other oily spices are produced by this system without difficulty because of the Kason's special anti-blinding device which keeps the screen clear at all times.
1. A spice plant may handle as many as 20 different products in one grinding system and complete cleanup along with screen change must be effected quickly to avoid excessive labor. Circular, highly polished stainless steel Kason's are ideal for this application since there are no "dead" areas for product accumulation. Screen cloths are mounted in a unitized assembly and change can be effected in 15 minutes or less.
2. Most conventional vibrating screens will clog quickly when operating on oily spices. The Kason avoids this with its unique motion and special anti-blinding device insuring maximum production and recycle grinding of truly oversize material.
3. Kason spice classifiers are equipped with metal dust covers and by connecting feed, oversize and product discharge spouts to the system with flexible rubber connectors the entire operation will be dust-tight. This is particularly important in spice mills in order to avoid product contamination.
4. Kason's require minimum head room and in most instances it is simple to arrange for gravity feed from the grinding mill.
Usually single-deck Kason's to separate oversize from product but occasionally double-deck machines are used to produce two grades of spices simultaneously.
Sanitary, highly polished type 316 stainless construction at all points of material contact.
Stainless steel wire screen cloth to meet the specifications of any spice.
Metal dust cover and discharge spouts equipped with flexible neoprene connectors.