Temple-Inland, a major pulp and paperboard producer in Silsbee, Texas pumps large volumes of green liquor throughout their process. Green liquor is the paper industry's description for an aqueous solution of sodium carbonate, sodium sulfide, sodium hydroxide and sodium sulfate. This solution has the tendency to form carbonate scaling very quickly and thereby radically reduce the flow rates in pipe.Four years ago, George Pemble, a project engineer-group leader at Temple-Inland determined that they were experiencing as much as 50% downtime due to the scaling problem. "We were using basic carbon steel pipe" he reported, "and we were required to shut down our density control system for green liquor every other day and flush it for long periods. I decided that there must be a better way."
Working with a Plastic Lined Piping Systems local representative, Temple-Inland made the decision to design their density control system around Halar (ECTFE) lined pipe for three compelling reasons. First, ECTFE has good anti-stick characteristics and an extremely smooth surface finish. Second, it was able to handle the green liquor which is extremely caustic (pH=14). Third, it could operate in this system at 180-190°F. For these reasons, several hundred feet of ECTFE lined pipe and fittings were originally installed in 2-1/2" and 3" pipe sizes on two systems at the plant.
ECTFE is a versitile fluoropolymer that resists a wide variety of acids, bases and solvents in temperatures from sub zero to 300°F. Extruded liners in the straight sections and molded liners in the fittings have intergral flange faces. The liners are fusion bonded and locked in to prevent stress cracking and cold flow. The ECTFE lined pipe is available in sschedules 10 through 80 carbon steel pipe with liner thicknesses to 0.190". Standard sizes from 1" to 8" are available with various standard and special fittings.
Since the installation, George Pemble reports, "our carbonate scaling problem is basically gone. We now flush the system, very briefly, every other week to remove some soft sediment that collects in the pipe. We wouldn't be able to do what we are doing if it wasn't for the ECTFE lined pipe and fittings." Temple-Inland has recently installed two additional ECTFE lined pipe systems at this location for the same service.