Superabsorbent polymers are obtained by the polymerization of acrylic acid and its salts. Industrial processes for the production of superabsorbent polymers require many labor- and capital-intensive steps in several vessels. This paper presents a new process that synthesizes superabsorbent polymer in a single vessel, a modified spray dryer. Very fast polymerization is obtained with appropriate reactants and initiators, selected from 150 different combinations. Preheating and using the heat of neutralization of the acrylic acid greatly accelerate polymerization. A new, ultra-rapid reactor quickly mixes two streams of reactants and initiators to provide fine droplets of polymerizing liquid. A two-stage mixer provides the best results: two flat jets of liquids are first impacted at high velocity, and a high velocity gas jet is applied to the resulting liquid stream to form a spray of fine droplets and enhance drying. The compact reactor is located within the inlet region of a standard spray dryer that can deliver dry particles of superabsorbent. Preliminary experiments in a modified pilot-plant spray dryer gave superabsorbent polymer with a conversion rate higher than 65%.