Calcium Chloride is a common deicer used to melt ice and snow in the winter. But what most people don’t know is that it also works really well as a natural dehumidifier.
I purchased a large bag of Calcium Chloride at the hardware store for around $25. It weighs about 44 lb so it’s a good deal, and it’ll last a while. The product name is Dow Flake XTRA, 83-87% pure Calcium Chloride. See Figure 1.
I placed several pounds of the salt, spread evenly, in a large stainless steel tray I had lying around. The tray dimensions are roughly 60cm long x 60cm wide x 5cm deep. I placed a fan near it to blow air across the surface (Figure 2). I found it was better to use a fan without any housing around the blades that would direct the flow of air. With no housing the air flows across a larger area and I get greater moisture absorption.
As mentioned in other posts, Calcium Chloride salt is unique in that it readily absorbs moisture from the air. And by blowing air across it with a fan you get forced convection enabling the salt to absorb moisture from the air more quickly than it would without a fan. Due to the large area of the tray I get a significant moisture removal rate, rivaling that of an electric dehumidifier, and of course cheaper.
After a few days of the fan running constantly I get a substantial accumulation of water in the tray (Figure 3). I then decant this into a container (Figure 4). Since the tray has a lip around the top corners, decanting with no spillage is easy. Notice that the liquid Calcium Chloride brine is a slight pink color. This is due to the chemical makeup of this particular brand. Mind you, it’s not 100% pure so that may be the reason.
The brine can then be heated over a high heat such as with an outdoor barbecue or concentrated solar energy. This will evaporate the water leaving the salt behind. This will allow you to reuse the salt over and over again. My next post describes this: Separating Calcium Chloride From Water.