ANDRITZ GROUP
PULP & PAPER products
Pulp production
Pre-hydrolysis continuous cooking

ANDRITZ pre-hydrolysis continuous cooking

The most advanced way to produce dissolving pulps

The key to successful dissolving pulp production is efficient removal of the hemicelluloses in the fiber source without damaging the actual cellulose. The Pre-Hydrolysis Vessel (PHV) designed and delivered by ANDRITZ is state-of-the-art technology to produce high-quality dissolving pulp and other valuable by-products at the lowest cost.

Continous Lo-Solids cooking with pre-hydrolysis vessel. Shandong Sun Honghe Paper, China.

Older methods for pre-hydrolysis of kraft pulp were less than ideal

There are significant challenges in the removal of hemicelluloses when producing dissolving pulp with a continuous cooking system. Achieving stable production and avoiding the precipitation of by-products from the cooking reaction were common difficulties in older systems that led to operational and quality issues.

The PHV: advanced and effective cooking for dissolving pulps

ANDRITZ took a fresh look at the process and re-designed its cooking system to make the removal of hemicellulose much more effective. The foundation for modifying the process and producing new equipment components is based on years of experience in producing pulps for paper grades. The ANDRITZ Pre-Hydrolysis Vessel (PHV) has gained rapid acceptance and has been delivered to several mills in Asia where viscose fiber growth is the highest.

The PHV utilizes autohydrolysis for efficient hemicellulose removal. This allows the recovery of the hydrolysate, which contains dissolved hemicellulose, in a water solution. The process is simplified and costs are reduced since autohydrolysis does not require additional chemicals in order to start the hydrolysis reaction.

The ANDRITZ Pre-Hydrolysis Vessel (PHV) can be retrofitted to existing continuous cooking installations. Installation and operational costs are likely to be much lower than traditional cooking systems for dissolving pulps. Fiber yields are expected to be several percentage points higher than batch technologies due to excellent selectivity of the principle reactions and controlled, sustainable recovery of by-products.

Current practice for handling the hydrolysate is to neutralize it and combust it with the bulk black liquor. However, in the future, this valuable stream could be processed for energy production or as a building block in other added-value products, further improving the economics of the overall pulping process.

Processes and technologies available from ANDRITZ

Diamondback chip pre-steaming
TurboFeed chip feeding
Pre-hydrolysis treatment
Lo-Solids cooking
Clean steam technology
Hydrolysate treatment
Laboratory simulations and investigations

3d model of a fiberline with pre-hydrolysis vessel

Diamondback chip bins. Klabin S.A., Brazil

ANDRITZ chip feeding and pre-steaming

Efficient, reliable systems for continuous cooking.

ANDRITZ PULP & PAPER continues to be an innovator in technologies for chemical pulp fiberlines. TurboFeed and Diamondback are excellent examples. The TurboFeed technology eliminates traditional investments in high-pressure feeding equipment, which also eliminates the costs of periodic rebuilds of the equipment. The Diamondback is today’s standard for pre-steaming wood chips for optimum impregnation without moving parts to eliminate plugging or hang-ups in the chip flow.

ANDRITZ pre-hydrolysis continuous cooking

The most advanced way to produce dissolving pulps. The key to successful dissolving pulp production is efficient removal of the hemicelluloses in the fiber source without damaging the actual cellulose. The Pre-Hydrolysis Vessel (PHV) designed and delivered by ANDRITZ is state-of-the-art technology to produce high-quality dissolving pulp and other valuable by-products at the lowest cost.