Abstract: A two-zone lime mud calciner is provided for processing lime mud from kraft pulp recovery operations. A conveyer is employed for conveying lime mud horizontally through the calciner. The first zone and second zone of the calciner each contains a dielectric hysteresis heating device for first drying the lime mud in the first zone and then decomposing the dried lime mud to lime and carbon dioxide. A co-current flow of purge air removes steam generated in the first zone and a counter-current flow of purge air removes carbon dioxide generated in the second zone with a vent being provided adjacent the upstream and of the second zone.

Abstract: Deinking by-product from wastepaper recycling operations and pulp mill clarifier sludge are incorporated into drywall or other gypsum-based building products, such as building blocks. The deinking by-product or pulp mill clarifier sludge is diluted and mixed with stucco (calcium sulfate hemihydrate). The resulting slurry preferably is subjected to an initial dewatering, following the on-set of hardening of the gypsum, and drywall or other building product is formed from the dewatered material. A significant loading of fibrous material in the drywall sheet or other gypsum product is achieved using the procedure, imparting improved flexural strength to the product. The preferred procedure also may be used to incorporate virgin or recycled wood pulp into the building product.

Abstract: Lime mud from kraft pulp recovery operations is processed using dielectric hysteresis heating, in a two-stage operation, in which wet lime mud first is dried then the dried lime mud is decomposed to lime and carbon dioxide. A two-zone lime mud calciner is employed in which the lime mud is conveyed horizontally, with drying being effected in the first zone and then decomposition being effected in the second zone. A co-current flow of purge air removes steam generated in the first zone and a counter-current flow of purge air removes carbon dioxide generated in the second zone.