Production process for continuously preparing bentazone

The invention provides a production process for continuously preparing bentazone, which mainly aims at continuous production of bentazone and provides continuous operation of six processes of condensation, hydrolysis, dichloroethane removal by cyclization, cyclization reaction, methanol removal by cyclization and acidification of the bentazone production process. Continuity of three reaction processes of condensation, cyclization and acidification is achieved by adopting a multi-kettle series connection mode; a hydrolysis kettle, a liquid-liquid separation device and an extraction tower are combined to realize the continuity of the hydrolysis process; a falling-film evaporator is adopted to realize the continuity of the solvent dichloroethane removal process; water is added in advance, theboiling point difference between water and methanol is utilized, the cyclization methanol removal process is continuous in a solvent methanol removal mode through a rectifying tower, and thereby qualified methanol is obtaine