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Evaporation of process water from recycled containerboard mills, TAPPI Journal July 2023
ABSTRACT: The reduction of the specific effluent discharge volumes of paper mills leads to concentrated process waters that are difficult to treat. Evaporation is an effective water reclamation technology; however, its feasibility largely depends on the fouling behavior of the calcium rich process water. A pilot plant study was conducted to investigate fouling of an evaporator processing the production water from a recycled containerboard mill. The evaporator was operated continuously for five weeks at an evaporation temperature of 55°C and a differential temperature of 5°C, and with a recovery rate of approximately 90%. The calcium ion concentration of the circulating liquor exceeded 7,000 mg/L with a pH of 6. Despite the high fouling potential of the circulating liquor, the heat transfer coefficient did not decline over the investigated trial. The absence of deposits on large areas of the heating surfaces demonstrate that the process water does not generally form deposits under the conditions that were investigated. Calcium sulfate deposits were only found in areas where there was inadequate coverage of liquid over the heating surfaces.The findings show that evaporators can be used to effectively close the water system of recycled containerboard mills without fouling impacting the energy efficiency.
Journal articles
Magazine articles
Recovery boiler back-end heat recovery, TAPPI Journal March 2023
ABSTRACT: Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%•4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.
Journal articles
Breakup Mechanisms of Brittle Deposits in Kraft Recovery Boilers â?¢ A Fundamental Study, TAPPI JOURNAL September 2009
Breakup Mechanisms of Brittle Deposits in Kraft Recovery Boilers • A Fundamental Study, TAPPI JOURNAL September 2009
Journal articles
Modeling of Bagginess Due to Storage of Paper Reels With Ridges, TAPPI JOURNAL September 2009
Modeling of Bagginess Due to Storage of Paper Reels With Ridges, TAPPI JOURNAL September 2009
Journal articles
Hot-water pre-extraction from loblolly pine (Pinus taeda) in an integrated forest products biorefinery
Hot-water pre-extraction from loblolly pine (Pinus taeda) in an integrated forest products biorefinery, TAPPI JOURNAL June 2008
Journal articles
Effects of impregnation time on hardwood kraft pulp characteristics and papermaking potential â?¢ a mill study, TAPPI JOURNAL April 2010
Effects of impregnation time on hardwood kraft pulp characteristics and papermaking potential • a mill study, TAPPI JOURNAL April 2010
Journal articles
Online monitoring of inorganic cooking chemicals in white liquor by pulse voltammetry, TAPPI JOURNAL August 2010
Online monitoring of inorganic cooking chemicals in white liquor by pulse voltammetry, TAPPI JOURNAL August 2010
Journal articles
Study on the Chemical Modification Process of Jute Fiber, TAPPI JOURNAL February 2010
Study on the Chemical Modification Process of Jute Fiber, TAPPI JOURNAL February 2010
Journal articles
Superhydrophobic paper coating containing nonconventional clay, TAPPI JOURNAL November 2010
Superhydrophobic paper coating containing nonconventional clay, TAPPI JOURNAL November 2010
Journal articles
Editor's Note: PEERS Offers Industry Perspective, TAPPI JOURNAL October 2010
Editor's Note: PEERS Offers Industry Perspective, TAPPI JOURNAL October 2010