Chromium cement plant

Even after decades, the chromium emissions of a former cement plant induced a significant increase in the Cr content of wild and cultivated plants, without triggering phytotoxic nutritional damage in the flora, fauna and humans (Table 8.16). 

Tannins occur in many plants and are separated by extraction. At present, only quebracho extract is used as a mud thinner in significant quantity in the United States. Quebracho is an acidic material and performs best at high pH. It is an excellent thinner for lime-treated and cement-contaminated muds. However, it is not effective at high salt concentrations. Sulfomethylated tannin products are functional over a wide range of pH and salinity and have either been treated with chromium for good thermal stabiUty (58) or are chrome free. Concentrations of tannin additives are ca 1.5—18 kg/m (0.5—6 lb/bbl). 

Cement-producing plants, because cement contains chromium Industrial cooling towers that previously used chromium as a rust inhibitor Waterways that receive industrial discharges from electroplating, leather tanning, and textile industries... 

Tab. 6.16 Effects of emissions of a former cement and incandescent phosphate plant on chromium contents in wild and cultivated plants (pg dry matter)...

From about 1950, Shell 205 and similar catalysts based on alkalized iron and chromium oxides were used exclusively for styrene productioa As plant capacities were rapidly expanded, efforts were increased to improve the performance of the catalyst. Higher potash levels were introduced and cement binders were used to increase strength and selectivity. Ethylbenzene conversion, which was still about 30-50% in the 1950 s, was increased to at least 60% by 1960. Better plant designs were developed and reactors with up to three beds were introduced. One of the first higher selectivity catalysts included vanadium pentoxide with the conventional chromium oxide and potash. Improvements often led to different catalysts being used in a single reactor to optimize operation. 

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