A trained operator was blending water, sand, anhydrite, lime, cement, pulverized fly ash, and powdered aluminum in a mixing chamber to produce material for making concrete building blocks. In the blending process, sand and water are mixed to form a slurry, and then the powders are dispensed automatically into the mix by a computer-controlled system. Finally, a slurry of glycol-coated aluminum powder is added in the last few seconds before the mix is discharged into a car, and then molds are filled from the car. Adding aluminum to the mixture results in a small amount of hydrogen gas evolution, which disperses from the car into the surrounding ventilated area and out through roof vents. In addition to being an ingredient of the mix, water also helps to keep the mixture cool.
Forty-six hydrogen cylinders were accidentally charged with air instead of additional hydrogen during recharging operations at a synthetic liquid fuels laboratory. Cylinders were manifolded in batches of 10 or 12 to the utility compressor outside the laboratory. In normal operations, partly used cylinders containing hydrogen at a pressure of 800-900 psi were recharged to a pressure of 2000-2100 psi. Since the contaminated cylinders contained a highly explosive mixture of about 40% hydrogen and 60% air, it was decided to release the compressed gas to the atmosphere outside the building after grounding the cylinders. Two of the cylinders were successfully discharged, but an explosion occurred while the third cylinder was being discharged. Two chemical engineers were killed by the blast, view more