Liquid Waste Stream Remediation
Condensate Stripping
Steam stripping of foul process condensates is recognized as an efficient method for the removal of methanol and Total Reduced Sulphur (TRS) compounds. Methanol is formed during the pulping process through a reaction with the lignin in the wood. TRS compounds, principally hydrogen sulphide and methyl mercaptan along with other compounds are also formed during pulping.
Every A. H. Lundberg Systems stripping system contains the same basic components including a feed tank, fibre filter, condensate preheater, stripper column with rectification section and a reflux condenser.
Since the stripping process is energy intensive, maximizing energy recovery at its highest state is essential. The heat is recovered in the reflux condenser. The energy may be recovered by heating boiler feed water, heating process water, or by heating black liquor. Furthermore, the stripping system can be integrated into the black liquor evaporator system, allowing the use of evaporator steam in lieu of fresh steam. Alternately, the system can include a steam reboiler at the stripping steam inlet thereby recovering fresh steam condensate.
Optional system enhancements can include a secondary condenser and storage tank downstream of the reflux condenser to selectively condense and store liquid methanol from the stripper off gas for use as an auxiliary fuel.
The preferential method for stripper energy recovery and system integration is a matter of study for each mill.