Innovation Into Commercial Production
Traditional Methods of Solvent Disposal
Offset lithographic printing involves the transfer of ink from a plate to an intermediate blanket (usually rubber or plastic), and then to paper or some other medium. While the image plate is most often used only once or a few times before being disposed of, the rubber blanket is designed to be reused indefinitely. This requires cleaning the blanket of residual ink, paper dust, and other debris between different print runs. The cleanliness of the blanket directly impacts the quality of the printing.
Since the most common inks are petroleum-based, effectively removing these inks without damaging the blanket is usually accomplished with petroleum-based solvents including mineral spirits, naphtha, Stoddard solvent, as well as xylene and benzene.
The blanket wash solution may be mixed with water and applied through an automatic spray system, with the used solvent/water/ink runoff being captured in a catch basin, or applied manually with wipers dampened with wash solution. The wipers may be reusable or disposable.
Disposable wipers are less efficient at cleaning and are prone to leaving debris that degrades printing performance. They pack less efficiently than cloth wipers and thus cost more to transport. After use they are consigned to landfills that accept hazardous waste, or are incinerated.
Reusable wipers are transported to laundry facilities where the contaminated solvent/water solution is extracted.
The solution, either collected from an automatic spray system or extracted from reusable wipers, is typically transported as hazardous waste to a cement kiln where it’s blended with the fuel supply and burned. (See Figure 1.) Although the water content is not high enough to prevent combustion, it does reduce the BTU value of the blended fuel.
In all cases, the solvent quickly volatilizes and releases VOC gases into the atmosphere.
The C.L.E.A.N. Loop Innovation
C.L.E.A.N.’s Closed Loop Solvent Recycling System is a unique and proprietary process that intercepts hazardous solvent waste from the printing industry in two ways:
In the case of reusable cloth wipers, the used solvent laden towels are stripped of their solvents through a proprietary system using steam distillation. This service is provided by our alliance partner G&K Services Canada Inc.
Solvent from automatic blanket wash systems is shipped directly to C.L.E.A.N.’s reclamation facilities where it’s separated through a series of flash and fractional distillations. It is then further remanufactured into a new industrial raw material which is formulated into new Water Miscible ND-300 blanket and roller wash products.
Further to the above, the reclaimed solvents undergo a series of rigid quality control tests. Only when they fully meet exacting specifications are the formulations blended and resold to the printing industry at a reduced cost. (See Figure 2.) As well further reductions are passed onto the printer for their waste streams to be transported and put back into the program. As more printers participate, the waste stream stock increases providing further cost reductions to the printers on their purchases of the blanket and roller wash. This award winning program (link to award) currently reduces 1,305 tonnes of VOCs annually in Canada. Our goal is to triple this number by the end of 2017.
As an integral function of this process, hazardous waste that would otherwise be released to the environment is returned to productive use while passing on substantial savings and sustainability for the participating printers.
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