Chemical and Pulping Ltd

DDS Process & Control

Pulp & Paper Company Info 中文Chinese Gate Español Site Map

This page describes the major differences between RDH and DDS.

Proprietary Advanced Process and Control

Digester Discharge

Displacement batch digesters are not pressurized after the cooking is completed due to the displacing of the hot spent cooking liquors to the tank farm.  Therefore, the pulp in the digester can not be 'blown' or flashed to a blow tank similar to conventional batch digesters because most of the energy has been displaced to the tank farm.  The technique used to empty the digester is to pump the contents from the digester.  However, as the level of the digester decreases the NPSHa decreases, the pulp consistency varies and the tendency for high consistency pulp clumps creates a constantly varying suction environment to the discharge pump.  The DDS control system has minimized these challenges with fuzzy logic control (FLC).

Tank Farm Management

The tank farm is used to store chemical and thermal energy contained in the hot spent cooking liquors for reuse.  The tank farm serves the digesters, which need to produce pulp without disruption.  The DDS cooking system uses model predictive control (MPC) to predict the levels in the tank farm which are used to make adjustments to the flows between the tankage as well as to the digester scheduler.

Digester Channeling

The flow of liquid in the digester must remain in a plug flow profile with an interface zone between the different fluids as thin as possible.  The DDS cooking system uses multi-variable control (MVC) to maintain plug flow inside the digester.

Piping Techniques

Digester Discharge

The DDS cooking system has minimized suction head variations to the discharge pump by using new piping configurations.

Temperature Variations

The DDS cooking system uses various piping connections for liquor segregation to minimize temperature variations in the accumulators.

Home Up DDS Process & Control DDS Delignification

This site was written, designed, programmed and uploaded by Chemical and Pulping Ltd who takes no responsibility for any inaccuracies, despite their best efforts to minimize errors and omissions.    This site is protected by copyright.    © Copyright Chemical and Pulping Ltd 2005     Last modified: 22 Aug 2010