Calcium shreds

Residential carpets are continuing to be more visible in MSW. Carpets are quite complex with polyamide/PP/PET face libers, PP backing, latex adhesive, and calcium carbonate as tiller. In addition, the recycled carpet will have a higher amount of dust particles. There have been efforts in the United States to collect residential carpet. As it is very difficult to separate the different components of the carpet, the reasonable way is to shred the carpets and pelletize it so that the pellets can be used in products such as plastic lumber. Only a small percentage of the face materials (nylonb and nylon 66) are recovered and recycled. 

Because of advanced computer control (auxostat mode) and an anaerobic culture, sterilization of the feed, aseptic techniques, and sparging of the broth are not required. Using standard equipment mills, waste paper would be shredded directly into the reactor. This avoids expensive pre-suspending of the paper in a separate tank, prevents microbial contamination of the feed stock, and circumvents difficult pumping of paper slurries. Once the acetic acid has been extracted, some of the broth could be recycled back to the reactor. If the product were mixed calcium/magnesium salts, the solution could be concentrated to form crystals and sold. While the process control is sophisticated, the overall system represents a low cost approach for the production of acetic acid mixed with small amounts of other acids. The obvious application is acetate salts for deicing of highways. 

U.S. Pat. No. 6,207,729 [69] describes a similar thermoplastic composition comprising shredded and sheared cellulosic materials (33-59% by weight) such as old newspapers, magazines, kenaf, kraftboard, and so on, HDPE (33-50%), calcium carbonate (11-17%), and a coupling agent (Eusabond lOOD, 2%). 

Working with shredded refuse, Pohland (1989) demonstrated that the readily accessible and reactive waste components are more effectively and predictably converted and removed under the influence of leachate recycle than with single-pass leaching, while Buivid et al (1981) showed leachate recycle to be most effective after addition of anaerobic sludge and calcium carbonate. Barlaz et al (1987 and 1989) concluded that leachate recycle without neutralisation stimulated the formation of acid products, but that neutralisation of the leachate decreased acid production and enhanced gas production. These laboratory studies... 

For a 70 kg-scale reaction, 260 pellets are made, size 2 in. long by 2 in diameter. Each of these contains 265 g of uranium dioxide and 135 g of shredded calcium, i.e. a 25 per cent excess of the latter. These are stacked in a mild steel crucible, 42 in. deep by about 15 in. diameter, in regular staggered layers up to a height of 26 in. The crucible has previously been lined with a layer of lime, 1 in. thick on the walls and 3 in. thick at the base. A graphite lid is placed over the charge and covered with a I-in. layer of... 

A carpet separation process is illustrated in Fig. 13.1. First the carpet is sorted by face fiber. A near infrared sensor can identify the face fiber within a second even though nylon 6 and nylon 66 have similar infrared spectra. These two types of nylon carpet must be separated since they are incompatible. Next a guillotine is used to cut the carpet into small enough pieces to feed a shredder. After shredding some of the latex, calcium carbonate and dirt will separate from the carpet. To improve the purity of the carpet, fine grinding is necessary. Then a density separator can be used to remove more filler and dirt. Since there is a significant difference in the densities of nylon and polypropylene, a density separator can be used to separate nylon face fibers from polypropylene backing fabrics. Hydrocyclones can separate these polymers rapidly. Sink-float baths can accomplish this... 

The shredded PVC waste (20 - 30 mm particle size) is burnt continuously together with brown coal dust, sand and calcium-chloride solution. Brown coal dust and sand improve the burn-out and the recovery of chlorine sand also bonds with heavy metals etc. in the slag. The third additive is a 30% calcium chloride solution, recirculated from the waste water unit. Under incineration conditions calcium chloride is converted to calcium silicate and HCl. 

During mastication food is shredded and broken up into small fragments which are mixed with saliva and formed into a bolus. This causes dissolution of soluble constituents, facilitates swallowing and initiates the digestion of starch by salivary amylase. What happens after the bolus has been swallowed is only of indirect interest to the dentist. However, although the nutrients mentioned in Section 3 are necessary for the health of the body as a whole, certain dietary constituents are believed to have a direct effect on the tooth-saliva-bacteria relationship and the incidence of dental disease. Chief among these are sugars, fluoride, calcium and vitamin D which are considered in more detail in other sections of the book. 

---