Glass is brittle, hard and abrasive, making it more like rock than metal when it comes to recycling. In fact, the designs of many glass crushers evolved from equipment used in the rock and mineral processing industries.
Impact breakers are most commonly used, and they break the glass by hitting or throwing it against a hard surface. The end product from a glass crusher can be anything from cullet often used for remelting, to a sand-like product.
While the sand-like product may be too small for remelting, it has many other uses. Sometimes called “glas-sand,” it can substitute for sand in sandblasting, sandbags, or for landfill cover. It can also be used in place of aggregate for roads, in “glasphalt,” and for landscaping.
American Pulverizer Company (APC) manufactures 80 different glass breakers, of three types, in multiple sizes, with processing capacities of 100 lbs. per hour up to 180 tons per hour.
James Holder, sales engineer, said “theories used today are the same theories that were used 50 years ago, but better alloys are available to us today. We’ve learned what alloys are best suited for the glass market.” He explained that high-nickel and high-chrome alloys are very wear resistant, making them ideal alloys.
Holder explained that APC makes pre-breakers, lump breakers and hammermills for the glass industry. Pre-breakers reduce glass to a 3” to 4” nominal size. They have a vertical shaft with breakers bars that impact the glass.
Lump breakers reduce the glass to a 1” to 2” nominal size, using a horizontal shaft with steel breaker fingers. They have stationary combs and optional screens to ensure correct end product size. Hammermills produce the finest end product, reducing the glass down to a 10-20-mesh size.
Cynthia Andela, president of Andela Products, Ltd., (APL) explained that they manufacture a wide range of crushers as well as complete systems.
Along with standard glass crushing equipment, they manufacture specialized crushers including one as small as a dishwasher for tight spaces, large machines designed to handle automotive windshields, and machines for CRT processing. They can also engineer custom systems to suit their customers’ needs.
APL’s glass pulverizers produce an end product that resembles fine sand or gravel, with no sharp edges. Andela described the glass pulverizer’s action as “like a tornado” where the glass gets whirled around, breaking it, then falls through a screen as a clean product, while contaminants stay behind.
Andela described their pulverizer as “flail-type mill” which is similar to a hammermill, “but the hammers are flexible so they deflect, so something like a milk jug can go through without being forced to be ground up.”
APL’s glass breaker reduces glass to cullet size, ideal for remelting. Besides breaking glass, it separates glass from co-mingled streams, whether it is simply caps and labels or a mixed incoming stream.
APL’s glass pulverizers and glass breakers are both designed so they only break glass while leaving the contaminants whole, which Andela called “selective reduction.”
Ron White, general manager at C. S. Bell (CSB) described the glass breaking process using impact hammers and wear-resistant plates: “hammers hit the glass, glass hits the breaker plates and breaks it even more.”
The hammers are made of wear-resistant alloys for longer wear, and are free-swinging, on a horizontal shaft. White explained that the free-swinging hammers do more than break glass. “If something large gets in there that doesn’t need to be in there, the hammer gets out of the way,” thus reducing the possibility that an errant object might jam the machine, or cause excess wear or damage.
CSB makes three models of glass crushers as well as complete systems, and White said that the company “can do customization or build from the ground up” to fit the customer’s needs. Input can be increased up to 30” wide, and crushers can be modified to produce sand-sized output.
Not all glass crushers have recycling as the primary goal, White explained. Some crushers are destined for in-house disposal of containers, which must be destroyed for security purposes. Examples are bottles used in the pharmaceutical industry where the bottle or its residual contents must be destroyed.
CSB’s three basic crushers are destined for processing beverage containers, however. The three models are rated to process 2, 4 or 13 tons per hour, and output cullet-sized glass suitable for remelting.
Compactors, Inc. (CI) manufactures floating glass crushers – they sell a lot of them to the cruise industry where reducing the size of waste bottles is important. Their crushers can be conveyor or hand-fed, depending on the customers’ needs, and the output is usually one inch or smaller. Screens can be used to sort out and re-process larger pieces, if required.
Mike Pierson, president of CI, said that they can customize the crushers, to accommodate smaller pharmaceutical products or to make the machines “taller, shorter, wider – whatever they need.” CI fits a niche for smaller markets and for smaller materials, “more bottles and containers, not the bigger plates,” Pierson said. The crushers can process two to four tons of glass per hour.
Stedman Machine Company (SMC) offers two glass crusher models: the Grand Slam and the V-Slam. The Grand Slam comes in a variety of sizes, while there are two V-Slam machines available. Dave Grimes, sales manager at SMC said that they can make other machines as well, it “depends on what you’re starting with and what you want to end up with.”
The Grand Slam is what Grimes described as the “primary crusher.” It is a horizontal shaft impactor that accommodates up to 12” feed for gallon bottles and reduces the glass to a 6-8 mesh size. Various models can process 10 to 500 tons of glass per hour.
The secondary crusher, the V-Slam, is a vertical shaft impactor. It accepts a maximum 1” feed and reduces the material to a 20-mesh size. It processes 40 to 50 tons per hour. “The finer you grind, tonnage goes down,” Grimes explained.
The crushers use “blow bars” made from a high-chrome alloy for maximum life of the bar and run at a comparatively lower speed, because higher speed causes greater wear. “Stedman crushers last for years,” Grimes said.