Crude Sulphate Turpentine Properties
Turpentine is a general term used for the volatile oils present in trees, primarily coniferous. Alpha- and beta-terpene are often found in the highest concentrations, while others at lesser but still significant concentrations include limonene, camphene, myrcene, and terpineol, among others.
Crude sulphate turpentine (CST) is a term used for turpentine recovered during the kraft pulping of wood. CST includes the terpenes, but it will also contain other substances released from the wood, as well as undesired by-products of the pulping process, such as alcohols and the odorous total reduced sulphur (TRS) compounds. The total fraction of non-terpene compounds found in CST can vary greatly, but for design purposes 30% is often used.
Red oil is CST recovered from foul condensate steam stripping systems. Red oils will contain higher levels of the odorous TRS compounds. CST will typically contain about 0.5 to 1% TRS, whereas the concentration in the red oils will be in the range of 5 to 10%. It is this higher level of contamination which give the Red oils their distinctive colouring.
CST is toxic and extremely flammable so caution must be used when handling it. CST recovered from the kraft pulping process is typically used as a fuel or sold as a by-product. CST dumped to sewer in large quantities can upset the effluent treatment system (it is toxic to the bugs in high concentrations). Whenever possible foul condensates containing high levels of CST should be recovered and treated, preferably in the turpentine recovery system, otherwise in the stripping system where it will eventually make its way to incineration with the stripper off gas (SOG).
Turpentine Recovery System
AHL’s turpentine recovery system includes a pressure vacuum relief valve, a cyclone entrainment separator, two condensers, an indirect vent gas cooler, a horizontal flooded decanter with weir box, and a flooded horizontal storage tank.
The cyclone separator removes both fiber and entrained black liquor, since the black liquor may cause emulsification of the condensate in the decanter. The primary condenser condenses mostly water with some methanol, while the second stage condenser condenses the blow-through containing turpentine from the primary condenser. The condensers are arranged as vertical shell units with the foul vapours condensing in the tubes for ease of cleaning, if necessary.
The use of two condensers in series has several benefits over a single condenser:
- Produces high-grade clean hot water from warm water.
- Produces high-grade contaminated hot water for re-use.
- Increases decanter efficiency.
- Reduces turpentine losses.
- Reduces stripping steam requirements.
The AHL turpentine by-product recovery system extends to the safe handling of the recovered turpentine to rail car loading and/or safe incineration in a kiln, boiler or incinerator.