Release of toxic gases in the process of cemented backfill with phosphorus waste

Aiming at the practical problem of toxic gases generated in the process of cemented backfill with phosphorus waste (phosphogypsum as aggregate and yellow phosphorus slag as the binder), sources and dynamics of gas generation and the method of gas inhibition were investigated by monitoring the gas generated in the aggregate, the binder and the cemented slurry stirring process. The main findings proved that the gases were mainly generated from the binder in an acidic circumstance, and the gas generation sequence is PCl3, PH3, NO, H2S, NH3, and CO. Furthermore, lowering the pH value of the cemented slurry would increase the gas yield. The original gas yield of the slurry without acid addition was only 6.3% of the maximum gas yield after acid addition. By analyzing the circumstances of gas generation, a method of directly adding alkaline CaO to the slurry to control the gas generation was proposed. The addition of 12 wt% CaO was noted to reduce the gas yield by 99%. When the pH of the backfill slurry reached 10, the gas generation could be controlled. The results have implications for ensuring the health of mining workers and decreasing environmental pollution.

Automated summary

This study examined the issue of toxic gas generation during the process of cemented backfill with phosphorus waste. The gases were found to be mainly generated from the acidic binder, with a generation sequence of PCl3, PH3, NO, H2S, NH3, and CO. Lowering the pH of the cemented slurry increased the gas yield, but the addition of 12 wt% CaO was able to reduce the gas yield by 99%. When the pH of the backfill slurry reached 10, gas generation could be controlled. These findings have implications for worker health and environmental pollution reduction.