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The following information will help you to understand the history of displacement cooking systems.  [中文]

Displacement Batch Digester Development History

Where did Displacement Batch Digesting Start ?

In the 1980’s a company in Sweden, the Radar Company, started experimenting with collecting the black liquors from the digester before the pulp stock was removed with the hope of reusing the residual heat contained in the liquors for subsequent use in future cycles. The method that was invoked to accomplish this was to displace the hot liquors in the digester with other cooler liquors before the pulp product was removed. The displaced liquors were stored in a tank farm that was comprised of pressure vessels and atmospheric tanks. The liquors were diverted to the different vessels in the tank farm according to their temperature. The primary goal of this additional equipment and complexity was to reduce energy costs. Serendipitously, it was discovered that there were other benefits to this method due to residual chemicals in the recycled liquors. These chemicals increased the selectivity of the cooking reactions which subsequently increased the pulp fiber strength while allowing the removal of more lignin from the furnish in the digester (i.e. cooking to a lower kappa number). This decreased the lignin removal requirement downstream in the bleach plant. They marketed this system as RDH, an acronym for Radar Displacement Heating.

What are the Commercial Systems Offered ?

The owner of Radar at that time, Rauma Repola of Finland, sold Radar to the Beloit Corporation in the USA with an agreement to retain the use of Radar’s RDH® technology that was developed to that point in time.  Simultaneously with the Radar activity, Sunds Defibrator of Sweden was developing and marketing a displacement technology under the name of Cold Blow.  The retained use of the Radar RDH technology at Rauma Repola along with ideas from the Cold Blow system were marketed by Sunds Defibrator under the name of SuperBatch, who had become a subsidiary of Rauma Repola after the sale of Radar to Beloit.  Sunds Defibrator paid royalties to Beloit to use the Radar technology.  The Beloit system, Radar's original system, was still marketed under the acronym RDH, but Beloit changed the reference to Rapid Displacement Heating.  Further RDH developments by Beloit yielded modifications to their systems which were referred to by various titles such as:  RDH Stage II, RDH Stage III, RDH IIIM, and RDH 2000.  Sunds, today absorbed into the Metso Company, still maintains the name SuperBatch™ for all their modern batch cooking systems.  Other companies have also attempted this blend of batch cooking with recycle liquor management under different trade names (eg. EnerBatch and CBC from an Austrian company), but the RDH family and SuperBatch offerings have been the most successful.  It is interesting to note that no two of these installed displacement batch systems from any supplier are exactly the same, as each installation has had process modifications to enhance heat recovery, chemical recovery, chip impregnation, and production rates as the technical requirements and availability of capital have dictated at that installation.

Who Owns the Technology ?

The basic patent for displacement technology was owned by Beloit until their disbandment in 1998, at which time it was purchased by GL&V of Canada.  This basic patent does not cover countries in Asia Pacific, and will expire worldwide shortly.  The other related patents that Beloit owned were also purchased by GL&V of Canada, but they only cover a few countries in the world and almost none in Asia Pacific.  CabTec International respects patent protection and does not offer unauthorized technology.  The information concerning patents as well as an electronic search function can be accessed at various government websites, including the US Patent Office and the Canadian Patent Office.

DDS History DDS Theory DDS Performance DDS Process Diagram DDS vs. RDH Disp Dig Patents

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