Control Valve Solution for the Causticizing Section in the Pulp and Paper Industry
Application Description
The causticizing section is the core unit for alkali recovery in chemical pulping: green liquor and milk of lime react here to regenerate white liquor for cooking, with high-solids lime mud as a by-product. Media are strongly alkaline, carry fibre, deposit scale and abrade under widely fluctuating conditions, so valve reliability governs recovery efficiency and continuous operation of the whole line.
Application Focus
Incorrect material or structural selection leads quickly to body corrosion, scaling, stiction and loss of control, causing leakage and off-ratio causticizing that directly hits recovery efficiency and line stability. The key duties are as follows:
1. Severe acid and alkali corrosion: media swing widely across the process and carry solids that scour internal parts. The body must resist corrosion and trim must be hard; soft seats prone to ageing and damage are excluded to avoid seat failure and leakage.
2. Fibre fouling causes stiction: black liquor and white liquor carry long wood fibres that collect in the flow path and on sealing faces, forming hard scale that produces stiction and stroke deviation and can seize the valve completely.
3. Hard particle abrasion: lime mud cakes into hard lumps that score the trim continuously, widening sealing clearances, degrading control accuracy and shortening service life.
Solution Overview
A purpose-built V-port ball valve has been developed for causticizing duty. Principal features:
1. An extended stuffing box with double packing and a lantern ring, backed by a wave spring that maintains preload, automatically compensates for seat wear and keeps sealing reliable.
2. The V-notch in the ball shears against the seat, cutting long fibres and scraping deposits from the ball surface to prevent wear and stiction.
3. A flanged split seat can be removed without special tools for fast maintenance, while a disc spring provides dynamic loading that follows process fluctuations to keep the seal tight.
4. Special bearings withstand high temperature and corrosion with self-lubricating, low-friction operation, and block particles from entering clearances to prevent seizing.
5. A splined stem-to-ball connection carries high loads and resists contamination, suiting high differential pressure service while preserving control accuracy and stability.
Customer Value
The V-port ball valve is engineered for black liquor, white liquor and alkaline causticizing liquor - highly corrosive, abrasive, scaling and widely fluctuating duties.
1. It removes the leakage, stiction, wear and repeated failure typical of conventional valves, avoiding product loss and unplanned shutdowns and cutting the combined cost of maintenance, spare parts and lost output.
2. Stable, accurate control optimises key recovery parameters and raises alkali recovery while reducing energy use and supporting environmental compliance. Long service life also underpins line upgrades, consistent product quality and output, and stronger competitiveness.
Related Products
ZJHV V-Port Ball Valve: the rotating V edge shears fibres and stock lumps and carries them away without build-up on the sealing faces; designed for abrasive and scaling duty.
