The invention relates to the field of
fine chemical engineering, and discloses a green process for preparing
chloramine T by a
continuous flow reactor. The method comprises the following steps: respectively pumping p-toluenesulfonamide, a
sodium hydroxide solution and a
sodium hypochlorite solution into a micro-channel mixer for instantaneous mixing, and carrying out chlorination reaction in a multi-stage
temperature control tubular reaction unit; the concentration of free
chlorine is detected on line at an outlet, and the flow rate of a
chlorine source is dynamically adjusted through a PID
algorithm, so that closed-
loop control is realized; the reaction liquid is directly crystallized and separated to obtain the product without alkali wash. The
system comprises a base solution and
chlorine source conveying subsystem, a micro-channel mixer, a multi-stage reaction unit, an online monitoring module, a central controller and a
crystallization unit. The
side reaction is inhibited from the source, so that the free chlorine is less than or equal to 0.5 mg / L, the alkali washing step is omitted, the COD (
Chemical Oxygen Demand) of the
wastewater is reduced by more than 80%, the product purity is more than or equal to 99.5%, and the productivity is improved by 3 times.