Runaway’ reaction filters

In a review of incidents involving explosive reactivity of liquid chlorine with various organic auxiliary materials, two involved hydrocarbons. A polypropylene filter element fabricated with zinc oxide filler reacted explosively, rupturing the steel case previously tested to over 300 bar. Zinc chloride derived from the oxide may have initiated the runaway reaction. Hydrocarbon-based diaphragm pump oils or metal-drawing waxes were violently or explosively reactive [8], A violent explosion in a wax chlorination plant may have involved unplanned contact of liquid chlorine with wax or chlorinated wax residues in a steel trap. Corrosion products in the trap may have catalysed the runaway reaction, but hydrogen (also liberated by corrosion in the trap) may also have been involved [9],... 

Safety. The MR is much safer than the MASR. (1) The reaction zone contains a much smaller amount of the reaction mixture (hazardous material), which always enhances process safety. (2) In case of pump failure, the reaction automatically stops since the liquid falls down from the reaction zone. (3) There is no need to filter the monolithic catalyst after the reaction has been completed. Filtration of the fine catalysts particles used in slurry reactors is a troublesome and time-consuming operation. Moreover, metallic catalysts used in fine chemicals manufacture are pyrophoric, which makes this operation risky. In a slurry reactor there is a risk of thermal runaways. (4) If the cooling capacity is insufficient (e.g. by a mechanical failure) a temperature increase can lead to an increase in reaction, and thus heat generation rate. 

For a study of methods of assessment of thermal runaway risk from laboratory to industrial scales [2], A more detailed but eminently clear treatment of this and other needful safety considerations on scaling reactions up to production has since been published [3], So slight a scale-up as replacing two charcoal filters by one bigger one may cause a fire because heat loss was reduced [4], A journal largely devoted to scale-up of organic chemical processes has been launched [5]. 

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