Spray-drying process

A process for preparing a spray dried powder comprising

• (i) anionic detersive surfactant;
• (ii) from 0 wt % to 10 wt % zeolite builder;
• (iii) from 0 wt % to 10 wt % phosphate builder;
• and
• (iv) optionally from 0 wt % to 15 wt % silicate salt;
• wherein the process comprises the steps of:
• (a) forming an alkaline slurry in a mixer, the slurry comprising at least 5 wt % carbonate salt;
• from 0 wt % to 15 wt % water;
• and being essentially free of anionic surfactant, the slurry having a viscosity of from 10 to 60 Pas at a temperature of 70° C. and at a shear rate of 50s−1, wherein the alkaline slurry is shear thinning;
• and
• (b) transferring the alkaline slurry from the mixer through a slurry disintegration mixer and through at least one pump to a spray pressure nozzle;
• (c) contacting a viscosity increasing agent to the alkaline slurry after the mixer and before the spray pressure nozzle so as to increase the viscosity of the alkaline slurry to form a viscous alkaline slurry whose viscosity is at least two times higher than the viscosity of the alkaline slurry of step (a), step (c) being carried out at an average shear rate of from 10s−1 to 150s−1;
• (d) spraying the viscous alkaline slurry through the spray pressure nozzle into a spray-drying tower;
• (e) spray-drying the viscous alkaline slurry in form a spray-dried powder;
• and
• (f) optionally, contacting an alkalinity source with the alkaline slurry and/or the viscosity increasing agent, and/or the viscous alkaline slurry;
• and
• (g) spraying a nonionic detersive surfactant onto said spray dried powder.