Turning Acetylene Lime Slurry Into An Asset
[excerpt]

Pete Nofel, Editor

Disposing of acetylene generation co-products can be either an asset or an expense. Changing it from a waste item to a salable product can sidestep the regulatory thicket.

Roughly paraphrased, one of the laws of Thermodynamics states "You can't get something for nothing." So it is with acetylene generation. To generate acetylene, distributors must deal with co-generation products.

       As chemical reactions go, acetylene production is straightforward. Two parts water [H₂O] combined with one part calcium carbide [CaC₂] produces acetylene [C₂H₂], heat, and calcium hydroxide [Ca(OH)₂], suspended in water. The industry commonly refers to calcium hydroxide / water mix as carbide lime or lime slurry. Solid calcium hydroxide is left when water is removed either by evaporative drying or mechanical means.

       Solid lime or slurry can be either a boon or a bane for distributors generating their acetylene. In some instances, distributors sell the lime. Other distributors, because of a lack of a market for the lime slurry must treat it like a waste product. As a chemical waste, it falls under all of the federal, state, and local regulations that apply to industrial waste. But, as an industrial product, regulations are less rigorous.

Not quite B-9
      As industrial products go, lime is relatively benign. According to the Compressed Gas Association publication G-1.5 - 1991, second edition, Carbide Lime - Its Value and Its Uses, lime "first causes irritation and then more serious burns after prolonged exposure," because of its relatively high pH. Rinsing with water after casual contact with skin is all that's usually needed. The publication is available from the CGA, and may be ordered through the association's web site for $9 for members and $17 for non-members.

       T.K. Slaughter, plant manager for Gano Welding Supplies, Charleston, Ill., is a speaker for the Compressed Gas Association on lime accidents. Gano produces its acetylene and must deal with the lime slurry that is co-generated in the process.

      "It's something that you just don't want to leave on the skin for an extended period, but its toxicity is less than table salt," he said.

       Lime's alkalinity – 12.454 – is low enough so that it is below the federal standards for a caustic agent.

       Gano produces about 25 tons or more of lime per month.

       "The amount of lime produced is directly proportional to the amount of acetylene we generate," Slaughter said.

      Because calcium carbide is so reactive with water, acetylene production is nearly 99 percent efficient . . .

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