Method and apparatus for ultrasonic sizing of particles in suspensions

A method of monitoring the particle size distribution of particles in a suspension under dynamic conditions, comprising the steps of:

• transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension which attenuates the pulse;
• receiving the attenuated pulse after it has passed through the suspension;
• developing a first signal representative of the attenuated first pulse;
• digitizing the first signal with a high speed analog-to-digital converter to form a time domain signal;
• applying a Fourier.trensform to convert the time domain signal to an equivalent frequency domain signal, or spectrum, for each signal;
• converting the spectrum into dB to express the attenuation as a function of frequency;
• reflecting the first pulse with a reflector;
• detecting a first echo of the first pulse that has traveled over a first path length and determining the spectrum of the first echo;
• detecting a second echo of the first pulse that has traveled over a second path length and determining the spectrum of the second echo;
• determining the difference between the first echo spectrum and second echo spectrum and dividing said difference by the difference between the first path length and second path length to obtain an attenuation corrected for system variations.

A method of utilizing particle size monitoring to control a process for precipitating particles, comprising:

• to collect data continuously about the attenuation of an ultrasonic pulse passed through a master batch of a solution which has a particle size that is changing;
• generating a signal when the particle size reaches a predetermined attenuation value;
• withdrawing a sub-batch of solution after the signal is generated;
• predetermining a concentration of a second solution to be added to the withdrawn sub-batch based on the measured attenuation signal at the time of withdrawal;
• adding said predetermined concentration of second solution to the sub-batch to precipitate particles.