Method of measuring nitrogen trichloride in a process for the safe

Abstract

Polychloroisocyanurate products are produced in a continuous process which reacts a cyanuric acid component with a chlorinating agent in a reaction mixture to which a purge gas is fed to remove in an effluent gas, any nitrogen trichloride produced along with other by-products. The effluent gas is fed to a gas analyzer such as a gas chromatograph which determines the concentration of NCl.sub.3 present and compares it with a predetermined upper limit. If this upper limit is equalled or exceeded, the gas analyzer activates means to flood the reaction mixture with purge gas to prevent explosive amounts of nitrogen trichloride from being present in the reaction mixture. The gas analyzer may also control the feed rate of the cyanuric acid component and the chlorinating agent. The pH of the reaction mixture is also continuously measured in a pH analyzer having means to control the flow rate of the purge gas and reactants should the predetermined pH limits for the reaction be attained or exceeded. Also, the available chlorine concentration of a cyanuric acid containing effluent from a stripping unit is determined by an available halogen monitor which controls the feeding of acid to the stripper and prevents contamination of the effluent. A safe, non-polluting process is provided which greatly reduces the risk of an explosion because of the formation of nitrogen trichloride.