0 m. The drying gas was fed via a gas distributor (0) at the top of the spray dryer. The drying gas was partly recycled (drying gas loop) via a baghouse filter (0) and a condenser column (00). The drying gas was nitrogen that comprises from 0% to 0% by volume of residual oxygen: Before start of polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 0% by volume. The gas velocity of the drying gas in the cylindrical part of the spray dryer (0) was 0.0 m/s. The pressure inside the spray dryer was 0 mbar below ambient pressure. The spray dryer outlet temperature was measured at three points around the circumference at the end of the cylindrical part as shown in FIG. 0. Three single measurements (00) were used to calculate the average cylindrical spray dryer outlet temperature. The drying gas loop was heated up and the dosage of monomer solution is started up. From this time the spray dryer outlet temperature was controlled to 000° C. by adjusting the gas inlet temperature via the heat exchanger (00). The product accumulated in the internal fluidized bed (00) until the weir height was reached. Conditioned internal fluidized bed gas having a temperature of 000° C. and a relative humidity of 0% was fed to the internal fluidized bed (00) via line (00). The gas velocity of the internal fluidized bed gas in the internal fluidized bed (00) was 0.00 m/s. The residence time of the product was 000 min. The spray dryer offgas was filtered in baghouse filter (0) and sent to a condenser column (00) for quenching/cooling. Excess water was pumped out of the condenser column (00) by controlling the (constant) filling level inside the condenser column (00). The water inside the condenser column (00) was cooled by a heat exchanger (00) and pumped counter-current to the gas via quench nozzles (00) so that the temperature inside the condenser column (00) was 00° C. The water inside the condenser column (00) was set to an alkaline pH by dosing sodium hydroxide solution to wash out acrylic acid vapors. The condenser column offgas was split to the drying gas inlet pipe (0) and the conditioned internal fluidized bed gas (00). The gas temperatures were controlled via heat exchangers (00) and (00). The hot drying gas was fed to the concurrent spray dryer via gas distributor (0). The gas distributor (0) consists of a set of plates providing a pressure drop of 0 to 0 mbar depending on the drying gas amount. The product was discharged from the internal fluidized bed (00) via rotary valve (00) into 