42 the de laval type nozzle 30 described above allows the full expansion of the exiting cleaning agents when the length 42 l n of the diverging section 40 is defined in accordance with the following equation equ1 where the d t represents the throat diameter of throat 35 in inches u03b8 represents the divergent angle in degrees and l n the length 43 of the divergent segment in inches the exit diameter d e in equation 1 of the nozzle is defined by the following equation equ2 where m represents the mass flow of the cleaning agent in kilograms seconds v represents the specific volume of the fluid cleaning agent in meters cubed kilogram and u03b4h represents the enthalpy in kilojoules kilogram the full expansion nozzles of the present invention incorporate smaller throat diameters 38 which mathematically result in shorter divergent section lengths l n as is apparent from mathematical equation 1 the decrease in mass flow resulting from a smaller throat area of throat 38 is countered by volume of the exiting jets of fluid of a plurality of the smaller full expansion nozzles obtaining a mass flow equivalent to a single conventional sootblower nozzle but permitting the fluid to exit at a.