We Build a Better Mouse Trap

In the early 1970s Caldwell & MacKay came to the pulp and paper industry with, at the time, unheard of solutions to problems with chlorine waste removal. But with our expertise in science and engineering, and our knowledge of mass transfer and reaction kinetics set a new standard in bleach plant scrubber design.

To learn more about our innovations and expertise, click on at item below.

  • Materials of Construction

    Dual-Laminate Construction

    While good for mildly to moderately corrosive conditions, Fiberglass Reinforced Plastic (FRP) is less than ideal for use in the pulp and paper industry. Because of this, in the mid 1970s we introduced the concept of dual-laminate construction to pulp and paper. Dual-laminate construction consists of utilizing FRP as a base for structural integrity and as a secondary corrosion resistant layer. It is lined with PVC, CPVC, Kynar, or other similar materials to increase its corrosion resistance.

    Since the introduction of this process we have seen bleach plant scrubbers in operation for 20-30 years – a service life never before dreamed of in the pulp and paper industry.

    Alloy 926

    In addition to dual-laminate construction, in the 1970s we introduced the use of Hastelloy C-22, Titanium, and Alloy 926 metal fans in bleach plant scrubbers. Originally FRP fans were primarily used in the pulp and paper industry, but they had poor corrosion resistance, low hardness, and only 15,000psi yield strength. Today all of our bleach plant fans are made from Alloy 926 a strong (45,000-50,000psi yield strength), economical alloy.

  • Packed Tower Design & Improved Scrubber Technology

    We did not invent the packed tower, but we refined them and made them better. Initially scrubbers were made from FRP (fiberglass reinforced plastic) – a poor quality material that was easily susceptible to sunlight degradation – and utilized only 6ft of pack; which, despite conventional wisdom at the time, did not provide ample chlorine  and chlorine dioxide removal. To improve on the existing technology we:

    • Introduced Dual-Laminate Construction
    • Added 6-7ft of integral sumps – increasing residence time and approaching a once-thru basis
    • Were the first vendors in the country to offer 40-50ft packed bed heights – giving 99.5-99.9% waste removal
    • Introduced with equal distribution, low pressure spray nozzles. Spray headers are superior to drilled orifice or trough-type liquid distributors.
    • Added full 20 degree outlet cones to towers to improve flow dynamics through the demister zone
    • Redesigned the packing supports to create more open area resulting in less pluggage with solids in the tower