Process for filtering 2-acrylamido-2-methylpropane sulfonic acid

A continuous process for filtering a suspension of 2-acrylamido-2-methylpropane sulfonic acid crystals by means of a rotary pressure filter equipped with a drum, a surface of which is provided with cells covered with a filter medium, said drum rotating within a fixed concentric cylinder comprising at least three zones sealed from each other, respectively a filtration zone, a washing zone and a discharge zone, each zone opening onto the cells, the process comprising the following steps:

• a) supplying the filtration zone with a suspension of 2-acrylamido-2-methylpropane sulfonic acid crystals and filtering said suspension in the cells until a cake is formed,
• b) supplying the washing zone with a washing solution and washing the cake formed in the cells,
• c) discharging the washed cakes from the cells at the discharge zone;
• and
• wherein, a depth of the cells covering the filter medium is between 6 and 150 mm and in that a pressure of between 1 and 10 bars is applied in the filtration and washing zones.