Page 298 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

270 Applied Process Design for Chemical and Petrochemical Plants

CLEAN AIR OUTLET GAS INLEl
I 1 1 1 t

FIRST
L
SUPPLEMENTARY
WATER INLET- SK THROP i
PIECES

SK SPR a
NOZZl .E
SECOND
PASS

SLOPED
SPLASH
INSPECTION PLATE

BAFFLE CLEAN
BOX GAS
OUTLET

I
i
SLUDGE OUTLET Figure 4-62. Spray scrubber-fume scrubber arranged for vertical
downflow. Courtesy of Schutte & Koerting Co.
Figure 4-61. Spray scrubber. Courtesy of The Ducon Co., Inc.

4. Humidification-aids in flocculation and agglomer- the various types of equipment illustrated in Figures 458
ation of particles. to 464.
Figures 464 and -64A use a floating valve variable ori-
5. Condensation-will cause particle size to grow if gas fice opening as used in distillation contacting on the one
cooled below its dew-point.
or more trays included in the manufacturer’s design. This
6. Dust Disposal-running film action of liquid washes provides for good contact to wet down the solid particles
dust and collected liquid out of scrubber. as well as scrub many water soluble gas/vapors in the
7. Gas Partition-segregates gas into small streams and incoming stream (such as chloride, sulfur, and nitrogen
segments when flowing through a liquid or foam. compounds). Heat and mass transfer can take place
under these conditions. The pressure drop through this
8. Electrostatic Precipitation-the electrical charging type unit typically ranges from 1 inch water to 2 inches of
of the liquid droplets may come about by the inter- water for a five-fold increase in gas flow rates. Particle
action of the gas and liquid streams. Not much removal can go as low as 0.5 micron to greater than 30
known of this action.
microns. Usually a wire mesh entrainment pad is mount-
ed in the outgoing “clean” vapors to knock out liquid
The separating ability of most units is limited to 5- entrained particles, not solids.
micron particles. However, some will take out 1 to 5p par-
ticles at a sacrifice in collection efficiency. Due to the Cloth or Fabric Bag Separators or Filters
peculiarities of each system as well as the equipment avail-
able to perform the separation, it is well to consult manu- Reference [55] provides additional details beyond the
facturers regarding expected performance. Quite often bag filter applications, and Reference [60] provides a
they will want to run test units, particularly on difficult technical and analytical review of flowing gas-solids sus-
separations. References [ 12,131 give good descriptions of pensions.