Process and apparatus for continuous mixing of slurry with removal of entrained bubbles

#1. Field of the System

#This system relates to devices and processes for continuously preparing mixtures of powdered solids in liquids, further relates to processes for continuous removal of entrained bubbles from such mixtures. The system is particularly useful for the preparation of bubble-free slurries of finely ground polyurethane-foam particles in polyol, and for the preparation of new polyurethane articles that contain the finely ground polyurethane-foam particles.

#2. Background

#FIG. 1 is a process-flow diagram showing a process for the continuous production of substantially bubble-free slurry.

#FIGS. 2A and 2B show a simplified schematic diagram of a mixer according to the present system.

#FIG. 3 is a simplified schematic diagram of the mixer of FIG. 2 integrated with a mix tank.

#Those of ordinary skill in the art will realize that the following description of the present system is illustrative only and not in any way limiting. Other embodiments of the system will readily suggest themselves to such skilled persons.

#A schematic diagram of a process of the present disclosure 100 is shown in FIG. 1. Solid powder 105 (supplied for example in bulk bags) is conveyed by suitable means 110 (for example, a flexible screw conveyor) to the hopper of a powder feeder 120. For instance, the powder feeder may be a loss-in-weight belt or screw feeder. The powder feeder 120 delivers powder at a known and controlled rate to the mixer 200 (for example the disclosed mixer described in detail below) in tank 250. A liquid component (for example, polyol) is added to tank 250 through inlet 251. This liquid component is added at a known and controlled rate, for example by means of a non-cavitating positive-displacement pump 170, with a known and controlled speed of rotation, drawing from a tank (not shown) or other source of liquid 130. Alternatively, the rate of liquid addition can be measured with a flow meter. The ratio of powder addition rate to liquid addition rate to the mixer/tank is controlled to a predetermined value.

#The mixer 200 in tank 250, as described in detail below, performs the function of thorough mixing of the powder into the liquid, with good dispersion and wet-out of the powder. The mixed slurry, which also generally contains entrained bubbles, exits tank 250 through a screen plate 253 and an outlet 254. Drain valves 260 are provided throughout the process for cleanup and shutdown. Tank 250 may have a vent 259, a continuous-level sensor 258, a high-level sensor 256, and a low-level sensor 257 for measurement and control (see FIG. 6) of the liquid level in the tank.