Pulp and paper
Smelt dissolving tank
Also known as SDT, smelt dissolving tanks, dissolving tank.
A smelt dissolving tank (SDT) receives molten smelt discharged from the recovery boiler bottom and dissolves it into weak wash water to form green liquor (the alkaline solution sent on to the recausticising plant). Internal agitators and shatter jets break the smelt stream into small droplets to control the otherwise-violent quench reaction.
SDT vent stack
The dissolution is exothermic and steamy. SDT vent gas carries sodium-rich fume that condenses on the vent stack walls as a fine sticky deposit. Over time the build-up narrows the stack and disrupts vent flow.
Sonic-horn duty
Sonic horns mounted on the SDT vent stack keep the sodium-fume deposit from consolidating, preventing the periodic outages otherwise needed for vent cleaning.
Related terms
Related terms
- Smelt (recovery boiler)Smelt is the molten sodium carbonate and sulphide mixture that accumulates in the bottom of a kraft recovery boiler. It is dissolved into green liquor and recausticised to pulping reagent.
- Recovery boilerA recovery boiler burns kraft black liquor to generate steam, electrical power and recovered pulping chemicals. Iconic application for sonic horns on superheater cleaning.
- RecausticisingRecausticising converts green liquor (sodium carbonate) and burnt lime back into white liquor (sodium hydroxide and sulphide) for re-use in kraft pulping.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.