PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 5, Number 2, 2019
WASTE TREATMENT The effect of dried paper- mill sludge on cement hydration, Jurgita Malaiškienė et al, Journal of Thermal Analysis and Calorimetry , 2019, online. In the paper, the impact of paper-mill sludge dried at 75 °C (PS) on cement hydration is being analysed. The used specimens were made of CEM I 42.5 R cement and the added PS replaced 0%, 5%, 10% and 15% by mass of cement. The results of calorimetric measurements of the mixtures and the compressive strength were analysed (W/(C + PS) = 0.35). SEM and XRD tests were carried out after 3, 14, 28 and 56 days of curing W/(C + PS) = 1. PS was found to extend the induction period of the cement hydration and delay the time of the secondary heat release effect, especially in specimens with the highest content of the PS. The total heat release (after 96 h) measurement results showed that the highest total heat evolved from specimens without the PS. The total liberated heat gradually increased with the increase in the PS content in the cement paste mixture. In the specimens with 15% of PS, the total heat release decreased by 20%, as compared to the control specimen without the additive. XRD test results revealed that the standard minerals listed below were formed in cement stone: ettringite, calcite, portlandite, and calcium aluminium silicate hydrate. SEM tests revealed significant changes in cement stone microstructure caused by the increase in the PS in cement paste. The compressive strength of specimens with PS waste was found to be considerably lower in the initial stage of hardening; however, when samples hardening time is increased up to 56 days, the difference between the values of compressive strength for specimens 5% of PS and the control specimens decreases. Technical Feasibility of Zero Waste for Paper and Plastic Wastes, Deepak K. Sharma et al, Waste and Biomass Valorization , 10 (5), pp.1355 – 1363. Complete material recovery followed by recycling of paper and plastic waste streams is crucial for the success or failure of achieving zero waste targets. The highest recovery of material from paper and plastic waste streams reported in the U.S. and Europe are 85 and 73% respectively. However, this means there is still a remaining 15 and 27% of paper and plastic waste which is not recycled or reused indicating it is not possible to completely recycle all paper and plastic. Investigating the limitations that impede recovery and recycle identifies other avenues for engineering a zero-waste process. This study discusses the effects of various properties of paper and plastics on their quality and recycling rates. Furthermore, we present a thorough analysis of the estimated recovery for paper and plastic wastes in processing facilities. The results show that the recovery rate obtained from a traditional material recovery facility (MRF) is lower than that obtained from a combined MRF and a modern mixed-waste processing facility (MWPF). However, the MWPF is still being commercialized, posing a practical limitation in recycling operation. This paper focuses on delineating major technical issues underlying the limited recycle of paper and plastic as well as the limitations to collection systems. For example, in the U.S. the state-of-the-art recycling equipment used for paper had a stagnant recovery rate (~ 46,000 tonnes) from 2008 to 2013 of 66.4% although the amount of paper available for recycle is near 70,000 tonnes. Plastic recycling is a similar case where nearly 79% can be technically recovered due to problems associated with specific property requirements for final recycled products. Importantly, these limitations are independent of the actual market available for the recycled material.
Technical Abstracts
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