The present disclosure relates to an apparatus and a process for the preparation of chlorinated polyvinyl chloride (CPVC). The apparatus includes a chamber (16), at least one sparger tube (12), at least one agitator (2) and at least two baffles (18) fitted in the chamber and a plurality of irradiation sources (20) fitted inside the baffles in order to bring about accelerated photochlorination of polyvinyl chloride. The process includes reacting polyvinyl chloride (PVC) with chlorine in the presence of irradiation of wavelength ranging from 250 and 550 nm and power ranging from 0.01 to 0.04 Watt/ g of PVC, under agitation at a speed ranging from 100 to 1600 rpm, for a time period ranging from 2 to 12 hours, to obtain CPVC.