In the process industry, an efficient operation allows greater throughput of product, saving time and money. As technologies adapt and change, innovation becomes important in the development of ever more effective process heating operations. Often, advancements in process technology are made by creating customized solutions that combine manufacturing steps that previously required two or more machines.
One example of such innovation is a system that combines the drying and cleaning processes necessary in a glass recycling operation into a single machine. Because the glass is simultaneously dried and cleaned, handling is reduced, and breakage and product degradation is decreased. Also, the amount of capital equipment and necessary investment are reduced.
Combining processes can save a company time, money and energy without compromising the final product. Examples of combination units include drying and cooling units, screening and conveying units and, as mentioned, drying and cleaning systems. Combining technologies saves space and time while accomplishing the tasks to the same quality.
Glass recycling is a growing industry that reduces energy use and waste. For every 10 percent of recycled glass used in a new product, 2 percent of energy is saved compared to that consumed to create glass using all new materials. Reducing waste means less glass is sent to landfills and instead is used to create new products.
When recycling glass from the waste stream, the glass must be separated from other recyclables such as paper and plastic and cleaned. Typically, workers manually separate non-glass materials such as plastic bags and bottles from the glass to be recycled. Larger pieces of glass are broken into smaller pieces with hammers. Next, magnetic separators remove ferrous material from the line, leaving only a few, typically organic, substances comingled with the glass. Because the glass must be free of contaminants when it is melted during the recycling process, the contaminants are dried and separated from the glass before final sorting occurs. While these two process steps traditionally have been handled by two machines, the combination system can do both in a single step.
The combination unit is customized for glass recycling processes. In glass recycling plants, there is a possibility of undesired materials such as labels and corks contaminating the process. If these materials are not removed from the process flow, it can cause complications downstream. These complications can range from a reduction in product quality to damaging downstream process equipment.
It is also necessary to dry the product before the glass particles enter the screeners. Properly dried glass prevents screener blinding. Previously, the de-labeling and drying of glass was accomplished in two steps, performed by two different machines. The innovative technologies contained in the new unit combine the both these processes into a single machine, saving money, space and time.
The patented, custom-made dryer is based on a standard rotary drum dryer. The rotating drum is a perfect fit for glass recycling due to the ability to handle high moisture and multiple sizes of product. Rotary drum dryers are suitable for both coarse and fine particles, which is an advantage in glass recycling because the particle size distribution for recycled glass can range widely. The format of the machine also allows for high internal temperatures without high energy and airflow needs. This provides high drying temperatures with low heat losses. Rotary dryers are also insensitive to variations in the moisture content and the throughput. Rotary drum dryers are heavy machines that require minimum maintenance. In the event of a power outage, it is usually possible to resume operation when the power supply is restored. In the event the supply of drying air cuts out, the solid in the drum dryer is reliably conveyed by the rotation of the drum. Rotary dryers have a tolerance to operating faults with few wear/replacement items.
The glass and contaminants are fed into the rotating drum. As the glass enters the machine, the moisture content is mostly contained in the contaminants. This is due to the organic nature of the labels and corks, which allows water to be absorbed. In contrast to the organic material, the moisture on the glass is only surface moisture. A burner heats the center of the drum, eliminating organics and evaporating the surface moisture from the glass. As the glass tumbles through the rotary drum dryer, the specially designed internal paddles provide the basis for the product cleaning.
As the glass rubs against itself from the rotation of the drum and the action by the paddles, the organic material behaves very differently from the actual glass. Due to the difference in moisture content, the wet organic substances simply rub off of the glass. After the organic contaminants separate from the glass, the organics are continuously consumed by the dryer heat. Previously, these two processes of drying and cleaning were performed in two different machines.
In addition to combining the drying and cleaning processes, the combination unit allows gentle handling of the product through a patented design. A key benefit of combining process steps is to reduce unnecessary breakage and product degradation. Additional attention was given to the design of the unit to ensure optimized product handling. The key part of dryer, and where the innovation takes place, is the paddles around the side of the rotating drum that pick up and move the product as the machine rotates. This technology provides multiple important benefits over other dryer types as well as the cleaning process itself. The way that the product is moved inside the drum is very gentle and causes minimal breakage in the glass, which is important to reduce wasted product. The paddles also move the product directly into the middle of the unit where the hot air is being blown through by the burner. This provides an efficient drying process and reduces the time it takes to dry the glass.
In the case of this customized solution, removing one step actually takes the process one step ahead.