1. WET FILM (PACKED TOWER) SCRUBBERS
November 25th, 2015
WET FILM (PACKED TOWER) SCRUBBERS
Application in the chemical synthesis of chlorine dioxide
Alvaro M. Gonzalez Vogel
Puu Environmental Engineering 1

2. INTRODUCTION Liquid phase scrubber + packing material.
Both phases provide energy for the gas-liquid contact.
The packing material to provide a large contact area between the phases, turbulent mixing, and sufficient residence time for the gas to contact the liquid.
Particles may accumulate, plugging the void spaces in the packed beds.
Wet-film scrubbers are not used when particle removal is the only concern.
Variables affect absorption efficiency: Gas velocity, Liquid injection rate, Packing size, Packing height.

3. TOWER DESIGN Countercurrent flow Cocurrent flow
Crosscurrent arrangement

4. PACKING MATERIAL
Packing material provides a large surface for contact of the gas and liquid phase.
The size, quantity, shape, and material would depend on the following characteristic: Cost, low pressure drop, corrosion resistance, Large specific area, Mechanical strength, Weight, Arrangement.
Trademark packing material

5. EXHAUST GAS AND LIQUID DISTRIBUTION
Exhaust Gas Distribution:
Addition of support trays (plates or grids) for the packing material  Distribution baffle.
Liquid Distribution:
Even distribution of liquid phase to avoid flooding
Three types: Perforated tube, weir distributor, and spray nozzles.
Perforated tube distributor
Trough and weir distributor

6. PULP BLEACHING
Chlorine dioxide

7. ClO2 SYNTHESIS
Chemical Process

8. ClO2 SYNTHESIS
Chemical Process

9. ClO2 SYNTHESIS Chlorine dioxide Absorber:
Bulk absorption of ClO2
Chlorine dioxide Absorber:
Super Intalox ®, Ceramic Saddles
Bottom section: 2 inches diameter.
Top section: 1 inch diameter  Higher surface area.
Fresh water from the middle, diluate ClO2 (2 g/l) from the top of the absorber.
Final ClO2 concentration: 8 g/l.
Exhaust gas is send to a vacuum ejector and then to the scrubber for full recovery of ClO2.

10. Absorption of residual ClO2
ClO2 SYNTHESIS
Absorption of residual ClO2
Chlorine dioxide Scrubber:
Super Intalox ®, Plastic Saddles
Bottom section: 2 inches diameter.
Top section: 1 inch diameter  Higher surface area.
Intermediate gap for homogenization of gas and reduction of clogging.
Final ClO2 concentration: 2 g/l.
Exhaust gas is send to the atmosphere.

11. ClO2 SYNTHESIS Chlorine dioxide Recovery:
Conclusions
Chlorine dioxide Recovery:
High removal efficiency is required (expensive chemical)
No particles in the exhaust gas
Good solubility of chlorine dioxide gas in water
Oxidant and acidic compound
Removal efficiency impact
on a pulping mill economy
2 Stage scrubber system seems to be a good design for full recovery of ClO2
Chlorine dioxide
2.5
US$/kg
Consumption 15
kg/BDt
Daily prodction
3,000
BDt/d
Annual production
1,065,000
BDt/y
39,937,500
MUS$/y
-5% recovery
1,996,875