Binderless Fiberboard Made from Primary and Secondary Pulp and Paper Sludge

Pulp and paper sludge is valuable in fiberboard manufacturing because primary sludge (PS) contains fibers and secondary sludge (SS) has adhesive properties. We evaluated properties of binderless fiberboard made from conventional pulp and paper mill sludge sources using a factorial design in which the factors were SS:PS ratio (1:9, 2:8, and 3:7) and pulping process (thermomechanical [TMP], chemical-thermomechanical [CTMP], and kraft). Sludge was collected, refined, dried, and characterized for chemical composition and fiber length. Internal bond strength of CTMP panels increased 90% and thickness swell of TMP panels improved 92% with increasing SS content from 10-30%. IR Fourier transform and X-ray photoelectron spectroscopy analyses were conducted to better understand these results. Increased bonding was attributed to presence of proteins and lignin on the sludge fiber surface, which enhanced adhesion during hot pressing, whereas surface contamination decreased bonding efficiency. The TMP formulation at SS:PS ratio 3:7 met the ANSI requirement for basic hardboard. All other formulations were not dimensionally stable enough to meet the standard. The CTMP source resulted in the highest mechanical properties, and thickness swell was similar for the TMP and CTMP pulping processes. The kraft source produced low-integrity and dimensionally unstable panels

Medium-Density Fiberboard Produced Using Pulp and Paper Sludge from Different Pulping Processes

Pulp and paper sludge can be recycled in the manufacture of medium-density fiberboard (MDF) because it contains wood fibers. A comparative study was conducted to evaluate the properties of MDF made from virgin fibers mixed with different pulp and paper sludge sources. A factorial design was used in which factors were mill pulping processes, thermal-mechanical pulping (TMP), chemical-thermal-mechanical pulping (CTMP), and kraft pulping, and percentage of sludge mixed with virgin fibers (0, 25, 50, and 75%). Virgin fibers were obtained from paper birch wood, an underutilized species. Chemical composition, physical characteristics, pH, and buffer capacity of sludge were measured. MDF properties decreased mostly linearly with sludge content. Panel properties negatively correlated with the proportion of nonfibrous material such as ash and extractives. TMP and CTMP sludge sources produced panels of similar quality, and kraft sludge produced the lowest quality. It was concluded that the amount of sludge that can be incorporated into MDF without excessive decrease in panel quality depends on the pulping process. At 25% sludge content, all panels met ANSI quality requirements for MDF used for interior applications

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020