Black Liquor Recovery

Process Wood Chips into Pulp

Plant Name: Paper Facility
Industry:       Pulp and Paper
Product(s):   Coated wood-free, gloss, and silk mixed hardwood kraft pulp

Application

Cellulose fibers are separated in the kraft process, a chemical pulping process in which wood chips are fed into a large digester to be cooked at high pressure and temperature, and added proportionally with a chemical solution known as “white liquor,” 12.5% of sodium hydroxide (NaOH), sodium sulfide (Na₂S), and sodium carbonate (Na₂CO₃).

After digestion, the result is a brown paste, which is discharged to a pressure vessel. Due to the high concentration of lignin, the white liquor becomes “black liquor.” This black liquor returns to the recovery plant and cogeneration plant for regeneration.

Challenges

In this facility, there was a recurrent problem with the existing magnetic flow meter. The PTFE lining was being destroyed after a few days and the PFA lining was being destroyed after two months. The customer used a specific maintenance procedure just to change the flowmeter out every two months to maintain the process.

Solution

After investigation, Yokogawa found that the lining destruction/deformation was the result of fluid migration. Yokogawa proposed the following:

• The ADMAG TI PFA lining is superior against fluid migration compared to conventional PTFE and PFA linings.
• A metal retention grid, as a standard feature, withstands high slurry concentrations and avoids liner deterioration.
• Option “/H,” a vent, prevents lining damage.
• Dual-frequency excitation provides noise resistance, zero stability, and a faster response.

The first unit sold on this application is still in place and works very well. Following this success, ADMAG TI is now the standard at this facility.

Key Advantages

ADMAG TI – AXG Magnetic Flow Meters

• The AXG PFA flow tube design resists fluid migration.
• A retaining plate with injection molding ensures that liner deterioration does not occur.
• “/H” vent option prevents lining damage.
• Dual-frequency excitation provides noise resistance, zero stability, and fast response.

ADMAG AXG TI Family