Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 19

Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 18

Feed cream is introduced centrally on to a wheel rotating at speed of 10 000 r.p.m.  The feed flows outwards over the surface, accelerating to the outer boundary of the atomizer. The cream on leaving the atomizer readily disintegrates into a spray of droplets

The droplets leave the wheel as shown in the Figure 4.1. At high rotating speed, the radial velocity component of the droplet is much smaller than the tangential (angle of release approaches tangent to the wheel edge). The droplet release velocity approaches
the wheel velocity at high rotating speed of the atomizer. The radial velocity is directly associated with the size of the droplet it forms (and hence rate of evaporation). Increased amounts of rotation speed of the atomizer results in spray having smaller
droplet size.

Under ideal conditions, the atomizer would spray the cream in small individual droplets of equal size such that heat and mass transfer rates and drying times are the same for all droplets in the spray. The operating variables significantly influence the
droplet size produced from the atomizer wheels (Masters, 1979). These variables include speed of rotation, wheel design, feed rate, viscosity of feed and air, density of feed and air and surface tension of feed.

For calculation of air feed and product enthalpies, the freezing point of water is used as the reference temperature (Masters, 1979). For all the assumption, please see chapter 3 (Process science section). The total amount of cream coming into the atomizer
is calculated from the total amount of product required i.e. 378.75kg/hr, assuming that the mass into the dryer product equals the amount of the dryer for a negligible hold up time.

Continued in part 19

Short URL: https://www.newspakistan.pk/?p=14308

Posted by Ahmed Tariq on Feb 29 2012. Filed under Sci-Tech. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry