Air
Sustainable, conscientious, "clean" practices designed for use at KCG
Establishing good air quality systems can be complicated work, the general approach involves measurements in 2 places. Inside the building (where the people are working) and outside (where the air is exhausted). The first thing that must be done is to design the process to generate as little air contamination as possible using the mildest materials that you can (example: don't use harsh chemicals to clean things if you can use gentle ones, don't use a cleaner that needs to be incinerated (burned) to be disposed of when you can use a cleaner that can be purified and reused) in as controlled an environment as possible. Once you have the air contamination as low as you can get it, then you address the worker's exposure level. The air flow past him while he is working must be high enough to keep the dust or solvent or oil from building up in the room. You suck as much air out of the room per minute to keep ahead of the build up. Lots of different ways to figure this stuff out, generally it is calculated in terms of "room changes per hour" and a variety of air velocity measurements. Once you have sized the blowers and ventilation systems to remove the air from the work area at the right rate, now you work on the emissions control end of things.
For our shop floor, we are dealing mostly with oil from our CNC machines. We have a huge ventilation system that sucks air through all of the machines and into a 2 foot diameter pipe where it goes out into our mist eliminator. This machine has a series of mesh filters of various types that trap the oil droplets (and even the small amount of smoke that we make) and collects them into a big trap for us to recover and reuse. We measure our air quality inside the shop floor, in front of our most powerful machines and outside near the exhaust duct coming out of the mist eliminator. We selected our mist eliminator based exclusively on its oil trapping performance. It was the best we could find.
In our polishing area, dust and lint are the problem, while not considered serious environmental impact materials, they sure weren't there when we built our buildings here in Shasta Lake, CA, and they shouldn't be there because of us. Our polishing room exhaust goes through a large collector and out into a cyclone separator. This system whirls the dirty air around inside a cone shaped tube, the dust and lint hit the walls of the tube and fall down into a collection drum. The clean air is then sent back into the polishing room through a bunch of filter bags that remove any super fine particulate that may have gotten through the cyclone. The cool thing about this setup is that in the summer we don't wind up blowing all of the cool air outside. Because of the size of this room and the volume of air that we are moving, if we didn't bring the air back inside, we wouldn't be able to open the door to the area because of the vacuum we would create. Fun stuff.
Anodizing aluminum generates mostly water vapor in the air stream. Since nearly everything on the anodizing line is acidic, we use a counter flow water scrubbing system. The water in our scrubber is kept at a just barely basic pH (to neutralize the acid in the air stream) just the slightest bit more basic than tap water. We can make this work because of the size and type of scrubber that we have. The system is super simple. Dirty air gets sucked into the bottom of a 15 foot tall vertical tube to be exhausted from the top. The tube is packed full of little plastic things that look like Christmas tree ornaments. The water is pumped in as a heavy spray at the top of the tube so that it rains down through all of the plastic Christmas tree ornaments. Dirty air is going up, clean water is going down. The acid in the air stream contacts the water and is neutralized to form a salt.
The air continues out through an exhaust and the salt builds up in a pool that we clean out regularly. Because the anodizing line has chemicals in it that contain nickel and small amounts of chrome, anything that could have either of those materials in it must be considered hazardous waste and must be given to an authorized and approved hazardous waste handler for disposal. If there was anyway to do this process without generating hazardous waste, we would do it. There is no way given current technology. Any anodized aluminum that you have ever seen was processed using the same general chemistry, with the same waste products, no way around it right now. We are always on the lookout for a new way.
More on this in the water section.
