Hydrogen cyanide control

Recovery of hydrogen cyanide from coke-oven gases has been dormant in the early 1990s, but new methods involving environmental control of off-gas pollutants may be lea ding the way for a modest return to the recovery of cyanide from coke-oven gases (see Coal conversion process, carbonization). 

Most refiners employ continuous water wash as the principal mei of controlling corrosion and hydrogen blistering. The best sourc water is either steam condensate or well-stripped water from a water stripper. A number of refiners use ammonium polysulfat neutralize hydrogen cyanide and to control hydrogen stress crack... 

Although active safety is provided by the control systems mentioned above, passive safety is an additional important feature of a distributed plant. Due to the low inventory, even a total release of the reaction volume or an explosion would create no significant impact on the environment [139]. To prevent such scenarios, a total containment of the plant is envisaged it needs to be sealed for life . Hydrogen cyanide synthesis and chlorine point-of-sale manufacture are two examples for safety-sensitive distributed syntheses. 

Direct acidihcation of cyanide waste streams was once a relatively common treatment. Cyanide is acidified in a sealed reactor that is vented to the atmosphere through an air emission control system. Cyanide is converted to gaseous hydrogen cyanide, treated, vented, and dispersed. 

As a result of variation shown in toxicity, the evaluation of technologies applicable for discharge control, and treatment by some compounds within the industrial chemicals, the SIC 281 groups are further subdivided into 11 subcategories.23 They are aluminum fluoride, chlor-alkali, chrome pigments, copper sulfate, hydrofluoric acid, hydrogen cyanide, nickel sulfate, sodium bisulfate, sodium... 

Since the reaction mixture is acidified after the heating period, it is most convenient to carry out the reaction in a forced-draft hood in order to provide protection against hydrogen cyanide. If higher temperatures than those specified are used, the reaction may get out of control during the initial vigorous reaction. 

Carson, B.L., H.V.Ellis, B.L.Herndon, E.M.Horn, and L.H.Baker. 1981. Hydrogen Cyanide Health Effects. EPA-460/3-81-026, U.S. EPA, Office of Mobile Source Air pollution Control, Ann Arbor, MI. 

The modem concept of asymmetric induction is illustrated by the formulas in Fig. 1. As shown, the addition of hydrogen cyanide to the optically active aldehyde can lead to two diastereomers (1 and 2). If the process is under thermodynamic control, the formation of the more stable isomer will be favored that is, that isomer for which the non-bonded interactions between the newly formed cyano and the hydroxyl groups with the dissymmetric R group are weakest. On the other hand, the difference in the yields of 1 and 2 can be the result of kinetic control arising from a difference in the energies of the transition states—that state with the lower energy will form faster and lead to the product of higher yield. It is noteworthy that the tenets... 

Following chronic occupational exposure to 0.19-0.75 ppm hydrogen cyanide, 24-hour urinary levels of thiocyanate were 6.23 (smokers) and 5.4 pg/mL (nonsmokers) in exposed workers as compared with 3.2 (smokers) and 2.15 pg/mL (nonsmokers) in the controls (Chandra et al. 1980). This study demonstrates that tobacco smoking contributes to higher thiocyanate levels excreted in the urine. No studies were located regarding excretion of cyanide in animals after inhalation exposure to cyanide. 

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