Gibbs energy approach for aqueous processes with HF, HNO3, and CO2 ? CaCO3
Chemical thermodynamic calculations were used to represent vapor–liquid equilibria and chemical equilibria for aqueous systems with HF, HNO3, and CO2H2OCaCO3 solutions. The entropy production related to the dissolution reaction of calcite was calculated using multiphase thermodynamics and experiments carried out in this work. Modern simulation methods combined with experiments provide a useful tool for the research and design of new processes as well as evaluating changes in the operational conditions of chemical processes. These methods are used to study metallurgical, pulp, and paper industrial processes that involve the presented aqueous solutions. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1942–1947, 2004
Benefits of using carbon dioxide in the production of DIP containing newsprint
A papermaking system containing deinked pulp always comprises more or less calcium carbonate, which leads to a slightly alkaline environment. However, papermakers often like to operate at pseudo neutral pH due to several reasons. Conventionally in a pseudo neutral system, deinked pulp or paper stock is acidified by alum or sulphuric acid to a slightly acidic pH. Introduction of carbon dioxide gas to a DIP containing system is an alternative way to perform the acidification and at the same time affect the calcium carbonate chemistry. The possible reduction of the calcium ion content at pseudo neutral pH's provides an opportunity to implement new strategies in the control of dissolved and colloidal substances. In the presentation, changes in the wet end chemistry and their theoretical backgrounds are described for a case, where carbon dioxide has been introduced to a newsprint line using DIP. Aspects affecting dissolution of carbon dioxide gas in a paper stock and gas handling in an industrial environment are also discussed.
Differences in the length of initial hospital stay in very preterm infants
Aim: To investigate the effect of maternal, infant and birth hospital district related factors on the length of initial hospital stay in very preterm infants. In addition, rehospitalization rate within the first year from the initial discharge was studied.