Acetylene gas production: Effect of carbide granule size on overall burn time in miners’ cap lamps

Question - What size of calcium carbide granule would result in the longest overall burn time in a carbide miner’s lamp?

Hypothesis – In the reaction of calcium carbide and water, decreasing the granule size of calcium carbide will increase the reaction rate due to an increased total surface area.

Background Information- Total surface area increases as granule size decreases Manipulation of reaction is generally done only through control of water flow Various sizes of calcium carbide is available Very little information available – (antiquated) Calcium carbide and water are flammable and explosive “Carbide cannons” use powdered calcium carbide

Reaction - Text and images for this page provided by Marcos & Jonathan Perez-Blanco, © 2004

Initial Model-

Assumptions – Heat of reaction and its effects on burn time are negligible Calcium carbide samples are consistent quality Water flow does not vary in lamp Variation of water volume at initiation of combustion has negligible effect on overall burn time

Calcium Carbide

Calcium carbide(CaC2) was classified by size and weighed into 20 gram samples

Equipment Used- Cross-section of lamp Carbide Miner’s Lamp Diagram Source: www.caves.org Cross-section of lamp Carbide Miner’s Lamp

Procedures- Lamp was loaded with weighed and screened sample Lamp was filled with water Water flow setting was set at a constant Lamp was lit and allowed to burn until flame was extinguished Each sample size was tested twice and burn time was averaged Flame length was measure at 30 minutes

Safety consideration – Due to safety concerns, the finest granule size 2-3mm was not tested Lamp was loaded with the sample and reacted without combustion Gas production was instantaneous and profuse Results most likely would have been short burn time and extreme flame length, aka. EXPLOSION!!!!!

Trend of average burn time -

Flame Length -

Culminating Argument- Claim - Decreasing CaC2 granule size reduces the overall burn time in carbide lamp by increasing the reaction rate. Support - As successively finer sizes of carbide were reacted in lamp, the burn time in minutes effectively decreased. Flame length was also measured and graphed to indicate reaction rate.

Revised Model -

Final Thoughts - Based on the sizes of calcium carbide granules tested, the ideal size which would maximize overall burn time would be 12mm. Further testing of granule sizes above 12mm would indicate if larger granule sizes work in this type of lamp.