Lowering Kraft Black Liquor Viscosity by Ultrafiltration

Abstract

High viscosity is a major factor limiting the percentage total dissolved solids (%TDS) to which kraft black liquor (KBL), a spent pulping liquor, can be concentrated before it is burned to recover its fuel value and its inorganic chemicals. The effect on black liquor viscosity of removing high molecular weight lignin by ultrafiltration of 16% and 24% TDS liquors was studied.

Viscosities of ultrafiltration permeates were reduced relative to feed black liquors. When a permeate was concentrated to higher %TDS levels, its viscosity decreased yet further relative to feed samples evaporated to similar solids levels. Retentate viscosity was very high relative to both feed and permeate.

Ultrafiltration was carried out at 75[ddot]C using polysulfone membranes in a plate-and-frame or hollow fiber system. Flux rates varied greatly depending upon the specific liquor used. Flux was enhanced by increased temperature and increased linear velocity. The membrane molecular weight cutoff (MWCO) typically used was 50,000; increasing MWCO to 100,000 or 200,000 did not enhance flux.     

Combustion Properties of Birch (Betula pendula) Black Liquors From Sulfur-Free Pulping

Sulfur-free pulping has an environmental advantage over the traditional kraft process. This article describes the combustion properties of the black liquors produced from silver birch (Betula pendula) sawdust using three different cooking processes: two sulfur-free cooks (soda-anthraquinone and oxygen-alkali), and one reference kraft cook. It also considers the corresponding black liquors from an integrated forest biorefinery, in which a hot-water pretreatment of feedstock was performed prior to pulping. With the same cooking time, the total burning times for the sulfur-free black liquors were higher (15–55%) than those for the conventional kraft black liquors. However, no significant differences were noted between the total burning times for black liquors from pretreated feedstock and those from untreated feedstock. Especially in the case of untreated feedstock, the results showed that the kraft black liquors typically swelled more (25–45%) than the sulfur-free black liquors. It was further observed that the kraft and soda-anthraquinone black liquors from the untreated feedstock swelled more than those from the pretreated feedstock, while the oxygen-alkali black liquors swelled less.     

HEAT OF DILUTION AND ENTHALPY CONCENTRATION RELATIONS FOR SLASH PINE KRAFT BLACK LIQUORS

Enthalpy-concentration charts have been developed for different black liquors from the results of statistically designed pulping experiments for pulping slash pine in a pilot scale digester. Black liquors were considered as pseudobinary solutions and enthalpy-concentration relations over wide ranges of temperature were developed by using heat capacity data and heal of solution data for the liquors. Heats of dilution of black liquors were determined by an absolute calorimetric method at 80°C and then were used to establish a thermodynamic reference state for enthalpy calculation of black liquors. Heats of dilution for diluting slash pine black liquors from 80% to 5% solids are 175-260 kJ/kg solids, depending upon the cooking conditions. The effects of pulping variables on heats of dilution of black liquors are discussed.     

Behavior of Eucalyptus Wood Xylans across Kraft Cooking

Abstract

The 4-O-methylglucuronoxylans isolated from wood, pulp, and black liquor from six eucalyptus wood species were characterized. The ¹H nuclear magnetic resonance (NMR) studies revealed that all eucalyptus wood xylans contain O-2-substituted 4-O-methylglucuronic acid (MeGlcA) groups with hexose residues (9–26%). Their molecular weight (Mw) and polydispersity varied in the range of 26,083–28,405 g.mol^?1 and 1.13–1.17, respectively. The xylan retention during pulping increased with increasing degree of MeGlcA substitution in the xylose ring. An average of 54% xylans was retained in the pulp and the remaining 46% were degraded and/or dissolved in the black liquor (39% degraded and 7% dissolved). The average Mw of the xylans retained in the pulp and dissolved in the black liquor is influenced by pulp kappa number and averaged 20,134 and 14,778 g.mol^?1, respectively, at kappa 17. The average substitution degree of uronic acids, including MeGlcA and hexenuronic acids (HexA) in the xylans isolated from pulps (kappa 17) and black liquors were 1.05 and 1.13/10 xyloses, respectively. Of the total uronic acids present in the six original woods, an average of 36% w/w was retained in the pulps.     

STEADY SHEAR FLOW PROPERTIES OF HIGH SOLIDS SOFTWOOD KRAFT BLACK LIQUORS: EFFECTS OF TEMPERATURE, SOLIDS CONCENTRATIONS, LIGNIN MOLECULAR WEIGHT AND SHEAR RATE

The steady shear flow properties of several softwood kraft black liquors (slash pine) from a two level, four variable factorially designed pulping experiment were determined for solids concentrations from 50% to 85%, temperatures from 40°C to 140°C and shear rates up to 10,000 s-1 by using Instron capillary and Haake coaxial cylinder rheometers. It was shown that the slip velocity at the wall of the capillary is insignificant and that a two capillary method can be used to determine the viscosity of the samples. At high solids, black liquor can exhibit non-Newtonian behavior dependent upon temperature, solids concentrations, solids composition and shear rate. In general, the liquors behave as pseudoplastic fluids. The exact level of viscosity at any given condition is dependent upon the solids composition which will vary from liquor-to-liquor. The flow behavior of the liquors was described using power-law, Cross and Carreau-Yasuda models. Superposition principles developed for polymer melts and concentrated polymer solutions were applied to obtain reduced correlations for viscosity behavior of the liquors. By using a suitable reference temperature, related to the glass transition temperature of black liquors, a generalized WLF type shift factor was obtained for the liquors used in this study and can be used to obtain a reduced plot of viscosity behavior of other black liquors.     

Feasibility Studies on Palladium Extraction from Leach Liquors of Automotive Catalysts Using p-Diethylphosphonomethylthiacalix[6]arene

Feasibility studies for the recovery of Pd(II) from leach liquors of automotive catalysts using p-diethylphosphonomethylthiacalix[6]arene (1) and p-tert-butylthiacalix[6]arene (2) were conducted. Compound 1 was found to be a more efficient extractant than 2 for Pd(II) ions, indicating selective extraction of Pd(II) ions [E% = 98.4%] from the leach liquors. The majority of other metal ions present in the leached solution were not extracted except Zr(IV) ions [E% = 22%]. Stripping of the Pd(II) ions from the extractants was performed using acidic thiourea, thereby enabling the recycling of the extractants.     

Modified Kraft Pulping of Bagasse: Infrared Spectroscopy of Lignin

Abstract

The infrared spectroscopy of precipitated lignin from waste black liquors of bagasse pulping with kraft sulfite pulping process was investigated. Also the effect of anthraquinon and methanol addition in the soda, kraft and kraft-sulfite pulping liquor on the infrared specra of the precipitated lignin was studied. The presence of methanol in the pulping liquor causes an increase in the degradation as well as increase in the carboxylic group in the precipitated lignin. Also, the phenolic hydroxyl group in case of kraft lignin is higher than soda lignin. Presence of sulfite in the kraft-sulfite pulping liquor produces lignin hydroxyl groups.     

Liquid Lignin from the SLRPTM Process: The Effect of Processing Conditions and Black-Liquor Properties

CO₂ acidification of Kraft black liquors was performed at temperatures of 100–150°C and pressures of 5–8 bar in an investigation of the SLRP^TM process. At these conditions, a highly hydrated, lignin-rich liquid (vs. the usual solid) separated out to form a new phase. The solids content/ionic strength of the starting black liquor was found to be a key variable for controlling the bulk and molecular properties of the ?liquid-lignin” (LL) phase. For example, black liquors of lower ionic strengths (20% solids) produced LLs with lower ash contents and higher molecular weights, albeit in lower yields. In contrast, higher ionic strengths/solids content (40%) produced LLs in higher yields with higher aromatic and aliphatic hydroxyl contents. Temperature effects were significant only at the highest levels. The degree of hydration of the LL phase was found to be a useful measure of the water available for hydration of ionized/polarizable groups in lignin.     

Screening commercial available resins for simultaneous removal of two potential genotoxins from API methanolic streams

ABSTRACT

This paper explores potential API loss mitigation during purification in recrystallization mother liquors, by including a resin adsorption step, to remove potential genotoxin impurities (PGTIs). Mometasone furoate (Meta) is used as model active pharmaceutical ingredient (API) in the presence of 4-dimethylaminopyridine (DMAP) and methyl p-toluenesulfonate (MPTS) as two model PGTIs. AG 50W-X2 and IRA68 resins efficiently removed DMAP and MPTS from methanol solutions, respectively, with adsorptions higher than 93% and Meta binding below 2%. Removal of GTIs using these resins sequentially, or combining them in a single step, was also assessed, with superior results for the later approach.

Abbreviations: API, active pharmaceutical ingredient; DMAP, 4-dimethylaminopyridine; DMAP-Me, methylated DMAP; GTI, potential genotoxin impurity; Meta, Mometasone furoate; MPTS, methyl p-toluenesulfonate; PTSA, p-toluenesulfonic acid; TTC, threshold of toxicological concern.     

Effect of epoxidised natural rubber latex oncarbon black–natural rubber interaction inbead masterbatch

Abstract

Epoxidised natural rubber has been synthesised and used to improve carbon black–natural rubber in the bead masterbatch prepared according to the acid precipitation technique. Scanning electron microscopy showed that carbon black (40 pphr) was well incorporated in the spherical beads. The presence of epoxidised natural rubber latex caused an increase in the amount of unextracted rubber (or bound rubber content) of carbon black–epoxidised natural rubber–natural rubber beads     

Thermochemical Conversion of Black Liquor in the Liquid Phase

Abstract

Black liquor from kraft pulping of pine wood was pressure heated (about 20 MPa) for 45 minutes at both 300 °c and 350 °c and in both the presence and absence of a reducing atmosphere. Variable amounts of organic-phase (40–64 % of the black liquor organics), water-soluble (14–70 %), and volatile (12–55 %) products were formed. The organic-phase product originates mainly from the lignin fraction of black liquor, whereas, during the treatments, the corresponding hydroxy acid fraction was primarily degraded into lower acid intermediates and volatile components. The effects of temperature and gas atmosphere (carbon monoxide, hydrogen or nitrogen) on the conversion of black liquor are discussed.     

Compatibilising effect of carbon black on morphology of NR–NBR blends

Abstract

It is proposed that a non-polar filler can reduce interfacial energies between polar and non-polar polymers. Experiments have been carried out to test this hypothesis using carbon black as the filler in blends of natural rubber (NR) and a nitrile rubber (NBR) with an acrylonitrile content of 45%. Blends of NR–NBR (70/30) were prepared in an internal mixer with varying amounts of carbon black. The dramatic decrease in domain size on addition of carbon black was nonetheless lower than that predicted. Further experiments showed that the amount of carbon black available at the interface for compatibilisation was influenced by preferential incorporation into the lower viscosity elastomer (NBR). Thus, elastomers of similar viscosity should be added to the mixer prior to the carbon black in order to maximise the amount of ‘free’ unwetted carbon black present when the elastomers are blended together. Blending experiments carried out under these conditions resulted in a morphology close to the prediction based on thermodynamic theory.     

Separation of Metals from Sulfated Deep-Sea Ferromanganese Nodules by Adsorbing Colloid Flotation

Abstract

Adsorbing colloid flotation (ACF) is applied to aqueous leach solutions of sulfated deep-sea ferromanganese nodules and their process tailings. Metal cations of Cu, Co, Ni, Mn, Al, and Zn are separated simultaneously by flotation with hydroxide collectors and cationic surfactants from the leach liquors of sulfated ferromanganese nodules. Applications of ACF to the nodule tailings also makes possible the recovery of residual Cu, Co, Ni, Ti, Zn, Al, Fe, Mn, and the separation of Pb and V, the most abundant toxic species in the nodules and tailings.     

The Use of Tri-n-octylamine for the Separation of Vanadium(V) from Acidic Sulfate Uranium Leach Liquors

Abstract

Extraction of vanadium(V) from acidic sulfate solutions by a mixture of tri-n-octylamine and tributylphosphate (used as modifier) dissolved in kerosene has been studied. The distribution coefficient of vanadium(V) increases with an increase in pH and vanadium(V) concentration. The presence of iron(III) in aqueous solution does not have any appreciable effect, while large amounts of sulfate ion depress the distribution coefficient. Uranium(VI) has a distribution different from vanadium(V). Based upon these results, a scheme for the separation of vanadium(V) from uranium leach liquors has been made and checked experimentally.     

THE INFLUENCE OF COMPOSITION ON THE SWELLING OF KRAFT BLACK LIQUOR DURING PYROLYSIS

During the drying and pyrolysis phases of kraft black liquor combustion, significant swelling of individual liquor particles occurs. Swollen volumes can reach 20 to 30 times the original volume during combustion. The swelling process can affect the combustibility of black liquor and the amount of carryover in a recovery furnace.

The composition of black liquor was found to have a large influence on swelling. A combination of sugar acids and kraft lignin swelled to a larger extent than when either component was pyrolyzed separately. A 1:1 ratio of these two components resulted in maximum swelling for the various ratios tested. The molecular weight of kraft lignin had an effect on swollen volume with higher molecular weight fractions producing lower swelling chars.

Other components were found to reduce the swelling of black liquors. Extractives interfered with the swelling by appearing to change the deformable properties of the pyrolyzing material. Inorganic salts acted as a diluent.

Analysis of the surface characteristics of chars revealed that good swelling chars were composed of small bubbles 50 to 150 microns in diameter. Poor swelling liquors did not exhibit this phenomenon. The formation of bubbles was found to be initiated at 240°C, which closely corresponded to the thermal decomposition temperature of a sugar acid. Kraft lignin appeared to have a major influence on the fluid properties of the pyrolyzing particle. The composition of black liquor determines to a large extent surface forces present in black liquor; these forces are thought to be responsible for the extent to which kraft black liquors deform and swell during pyrolysis.     

Structural Changes in Lignin During Kraft Cooking Part 3. On the Structure of Dissolved Lignins

Two series of pine kraft lignins were prepared by a) normal kraft cooks to different pulp yield levels and precipitation of the lignins from the black liquors by acidification and b) by successive acidification of the black liquor obtained from a flow-through cook. All the lignins were extensively purified, subjected to elemental and methoxyl analysis and subsequently acetylated.

Quantitative ¹³C-NMR analysis was carried out on acetylated samples and the results were combined with the results of phenolic group determination by means of aminolysis and with elemental analysis data. The various acetylated lignins were also subjected to analysis by size exclusion chromatography.

All results are discussed with reference to known features of kraft cooking and of kraft lignins.     

Electrical Properties of Precipitated Lignins from Different Black Liquors

Abstract

Some corelations over the structure and dielectric properties of precipitated lignins from different waste black liquors of various modified soda and kraft pulping of bagasse have been discussed. The dielectric and the electrical properties at the same temperatures and frequencies ranges for the tested samples showed some differences which seems to be attributed to the difference in the structure and intermolecular interaction between lignin molecules. These differences are discussed on the basis of the molecular structure obtained from the infrared spectra. The conduction mechanism in the case of kraft and kraft sulfite lignins is due to electron transfer from the valence band to the conduction band by thermal activation.     

SO2-Ethanol-Water (SEW) Pulping: I. Lignin Determination in Pulps and Liquors

Abstract

Quantitative determination of lignin in SO₂-ethanol-water (SEW) pulps and spent liquors is described. The methods developed for conventional sulfite pulping are successfully applied to the SEW process. Linear correlations between Klason/total lignin content and kappa number are found over a wide pulp yield range for spruce, beech, and wheat straw. Lignin content of the spruce spent SEW liquors is determined using either hydrogen peroxide to remove SO₂ and dilution by 3% sulfuric acid or simply by dilution with 0.1M sodium hydroxide. The recommended wavelength is 280 nm. The experimentally found values for the extinction coefficient of dissolved lignin in 3% sulfuric acid and in 0.1M NaOH are 19 and 23 L/(g·cm), respectively. The interference of furanic compounds is eliminated by reduction with sodium borohydride.     

Soil and Water Decontaminaton by Extraction with Surfactants

Abstract

Samples of soil from contaminated sites and industrial sludges and residues were treated in the laboratory by extraction with water solutions containing surfactants and other additives. The contaminants included coal tar, PCBs, hydrocarbons, chlorinated hydrocarbons, nitrotoluenes and heavy metals. Some of the samples contained highly complex mixtures of organic and heavy metal contaminants. Reduction of the contaminant levels to less than 1 ppm was typically attained by the extraction treatment. The contaminant-laden wash liquors were purified by ultrafiltration, followed by air flotation. The cost of treatment by a commercial-scale, integrated process, consisting of the extraction and wash liquor purification steps, was estimated to be in the range of $50 – $80 per ton of treated soil, depending on soil matrix properties, chemical composition of the contaminants, and other site-specific factors.     

Studies on conductivity of nitrile rubber and its blends with NR,EPDM, and PVC

Abstract

Nitrile/butadiene rubber has been made electrically conducting by the incorporation of acetylene black. The change in conductivity and mechanical properties with varying amounts of acetylene black was studied. Nitrile rubber was blended with NR, PVC, and EPDM and their conductivity and mechanical properties were determined after incorporation of acetylene black. On comparison it was found that NBR-NR blends are more conducting than NBR-PVC and NBR-EPDM blends. Blends of NBR-NR containing varying amounts of NR and NBR were prepared with the same amount of acetylene black, and their properties were also studied. A blend of 80:20 NBR/NR was studied in detail by varying the concentration of acetylene black. It was found that electrical conductivity depends on the degree of dispersion of acetylene black in the polymer matrix.