Because the raw materials from which glass is made are indigenous to most areas of the world and are generally inexpensive, glass has become an important material for a variety of applications. Even with the proliferation of plastics, glass continues to be the material of choice for use in making many types of containers and windows. Indeed, millions of tons of glass are produced annually.
Although the unique properties of glass render it suitable for use in a variety of applications, disposal of glass following its intended use presents some significant problems. Indeed, approximately eight percent of all municipal solid waste in the United States consists of glass. As environmental efforts to promote recycling increase, the amount of glass which is recovered from the solid waste stream will also continue to increase. In the United States alone, over one million tons of glass are recovered annually for recycling. One factor limiting the amount of recycling which is done is the lack of effective and convenient recycling opportunities in many areas.
The principal use of broken or refuse glass, generally called "cullet," is by glass container manufacturers. Cullet is generally understood to include 1/4 inch to 1/2 inch glass particles. Although it is possible to manufacture some glass products using 50 percent cullet or more, most glass containers are manufactured using 20 to 30 percent cullet.
To meet strict manufacturing specifications, however, all cullet must be sorted by color, crushed to a size suitable for the furnace, and separated from bits of aluminum and other contaminants. These requirements, combined with the relative high cost of transporting cullet, make it difficult to produce high-quality cullet at a price which renders viable the recycling of glass.
Glass fiber, commonly used in insulation and similar products, is manufactured in a process which produces large quantities of glass fiber waste. When glass fiber waste is ground in conventional glass grinders, respiratory fibers are produced. Respiratory fibers are fine fibers having sharp, splintered ends which are inhaled into the lungs and which can harm the sensitive lung tissues. Long-term exposure to respiratory fibers can be extremely hazardous to ones health. Because of the risks associated with producing respiratory fibers, manufacturers of glass fiber dispose of the glass rather than grind and recycle it.
Because of the limited options for recycling glass, most scrap glass is disposed of merely by discarding it. As it becomes more difficult to utilize landfills as an alternative to recycling, increased emphasis has been placed on identifying effective and viable recycling options for glass.
Because no viable method of recycling glass presently exists, large quantities of waste glass, including glass fiber, are generated annually which contribute to the filling of landfills.
It would be an advancement in the art to provide an apparatus for recycling waste glass fibers which quickly and inexpensively converts the waste glass fiber into a form which can be safely handled.
It would be an advancement in the art if such apparatus could produce comminuted glass free from contaminants such as grinding compounds.
It will be appreciated that there is a need in the art for apparatus and methods for comminuting waste glass fibers, including respiratory fibers, into a useful fiber reinforcement material.