Combustion behavior of kraft black liquor droplets from hot water pretreated hardwood and softwood chips

This paper describes the combustion behavior of birch and spruce kraft black liquors obtained from an integrated forest biorefinery concept in which a hot water extraction of chips was performed before pulping. This pretreatment, aiming mainly at the recovery of various hemicellulose-derived materials, increased the concentrations of lignin and hydroxy acids in black liquors, compared with those in the reference black liquors without any process modification. On the other hand, the pretreatment decreased the concentrations of volatile acids and other organics (extractives and hemicellulose residues). Because of these characteristic changes, the total burning times (pyrolysis time plus char burning time) of the reference black liquors were somewhat longer than those of black liquors from the modified cooking process. The novel biorefinery based black liquors also swell more than the conventional ones. This phenomenon was primarily associated with the combined effect of high-molar-mass lignin fragments and hydroxy acids. All of the detected changes in combustion behavior were more intense for birch black liquors than for spruce black liquors.

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Evaporation of lignin-lean black liquor

TAPPI Journal ◽

10.32964/tj14.7.441 ◽

2015 ◽

Vol 14 (7) ◽

pp. 441-450

Author(s):

HENRIK WALLMO, ◽

ULF ANDERSSON ◽

MATHIAS GOURDON ◽

MARTIN WIMBY

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Black Liquor ◽

Salt Content ◽

Solubility Limit ◽

Lignin Removal ◽

Kraft Black Liquor ◽

Black Liquors ◽

The Heat Transfer Coefficient

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

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Organic materials in black liquors of soda-AQ pulping of hot-water-extracted birch (Betula pendula) sawdust

Holzforschung ◽

10.1515/hf-2014-0094 ◽

2015 ◽

Vol 69 (3) ◽

pp. 257-264 ◽

Cited By ~ 6

Author(s):

Joni Lehto ◽

Raimo Alén

Keyword(s):

Betula Pendula ◽

Degradation Products ◽

Cooking Time ◽

Hot Water ◽

Hydroxy Acids ◽

Monocarboxylic Acids ◽

Water Pretreatment ◽

Black Liquors ◽

Aliphatic Carboxylic Acids ◽

Hot Water Pretreatment

Abstract The chemical composition of black liquors obtained from the soda-AQ pulping of birch (Betula pendula) sawdust was studied as a function of cooking time, effective alkali content, and hot-water pretreatment of the sawdust prior to delignification. Special attention was paid on the formation of lignin-derived materials and low-molecular-mass carbohydrate-derived degradation products containing aliphatic carboxylic acids. In the case of the hot-water-pretreated feedstock, less acetic acid and formic acid and more nonvolatile hydroxy acids (especially monocarboxylic acids) were obtained. The observations can be interpreted as a result of the extensive removal of hemicelluloses during the hot-water pretreatment.

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Characterization of black liquors from kraft pulping of first-thinning Scots pine (Pinus sylvestris L.)

Holzforschung ◽

10.1515/hf.2010.005 ◽

2010 ◽

Vol 64 (1) ◽

Cited By ~ 3

Author(s):

Riikka Rautiainen ◽

Raimo Alén

Keyword(s):

Pinus Sylvestris ◽

Scots Pine ◽

Black Liquor ◽

Outer Part ◽

Short Fiber ◽

Kraft Pulping ◽

Hydroxy Acids ◽

Stem Wood ◽

Black Liquors ◽

Average Molecular Masses

Abstract Formation of hydroxy acids and soluble lignin fragments was investigated during conventional kraft pulping of first-thinning Scots pine (Pinus sylvestris L.) stem wood and its long-fiber outer part and short-fiber inner part. The results indicate that there are characteristic differences in the formation of hydroxy acids in these specific tissues, due to the slightly different contents of cellulose, hemicelluloses, and lignin. Notable are the differences in the formation of xylan-derived acids (2-hydroxybutanoic and xyloisosaccharinic acids) and glucomannan- and cellulose-derived acids (3,4-dideoxy-pentonic and glucoisosaccharinic acids). In contrast, no significant differences were found in the average molecular masses of the dissolved lignins in these black liquors. Finally, the black liquor from the outer part of first-thinning pine was shown to have similar properties as the black liquor from the reference mature wood material.

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Brownstock washing: A review of the literature

TAPPI Journal ◽

10.32964/tj13.1.9 ◽

2014 ◽

Vol 13 (1) ◽

pp. 9-19 ◽

Cited By ~ 1

Author(s):

RICARDO B. SANTOS ◽

PETER W. HART

Keyword(s):

High Efficiency ◽

Black Liquor ◽

Material Balance ◽

Kraft Pulping ◽

Wash Water ◽

Pulp Fibers ◽

Kraft Process ◽

Cooking Process ◽

Materials Used ◽

Entrapped Air

Brownstock washing is a complex, dynamic process in which dirty wash water or weak black liquor (dissolved organic and inorganic material obtained from the pulp cooking process) is separated from pulp fibers. The use of material balance techniques is of great importance to identify potential problems and determine how well the system is operating. The kraft pulping industry was the first known to combine pulp washing with the recovery of materials used and produced in the wood cooking process. The motivation behind materials recovery is economic, and more recently, environmentally driven. The chemicals used in the kraft process are expensive as compared to those used in the sulfite process. For the kraft process to be economically viable, it is imperative that a very high percentage of the cooking chemicals be recovered. To reach such high efficiency, a variety of washing systems and monitoring parameters have been developed. Antifoam additives and processing aids have also played an important role in increasing washing effectiveness. Antifoam materials help attain washing effectiveness by preventing entrapped air from forming in the system, which allows for an easier, unimpeded flow of filtrate through the screens and washers.

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Polysulfide-borohydride modification of southern pine alkaline pulping integrated with hydrothermal pre-extraction of hemicelluloses

TAPPI Journal ◽

10.32964/tj10.7.9 ◽

2011 ◽

Vol 10 (7) ◽

pp. 9-16

Author(s):

SUNG-HOON YOON ◽

HARRY CULLINAN ◽

GOPAL A. KRISHNAGOPALAN

Keyword(s):

Loblolly Pine ◽

Sodium Borohydride ◽

Kraft Pulping ◽

Hot Water ◽

Pulp Yield ◽

Paper Strength ◽

Southern Pine ◽

Two Stage ◽

Simultaneous Treatment ◽

Process Modification

We studied three process modifications to investigate their effects on the property and yield recovery capabilities of kraft pulping integrated with hemicellulose pre-extraction of southern pine. Loblolly pine chips were pre-extracted with hot water until the sugar extraction yield reached the targeted value of 10% and then subjected to conventional and modified kraft pulping. Modification included polysulfide pretreatment; polysulfide-sodium borohydride dual pretreatment, and polysulfide followed by polysulfide-sodium borohydride dual pretreatment two-stage pretreatments prior to kraft pulping. In the first modification, about 5% of the lost pulp yield (total 7%) caused by hemicellulose pre-extraction could be recovered with 15%-20% polysulfide pretreatment. Complete recovery (7%) was achieved with simultaneous pretreatment using 15% polysulfide and 0.5% sodium borohydride with 0.1% anthraquinone in polysulfide-sodium borohydride dual pretreatment. Two-stage pretreatment using recycled 15% polysulfide followed by simultaneous treatment of 6% polysulfide and 0.4%–0.5% sodium borohydride with 0.1% anthraquinone also achieved 100% yield recovery. Continuous recycling of 15% polysulfide employed in the two-stage process modification maintained its yield protection efficiency in a repeated recycling cycle. No significant changes in paper strength were found in handsheets prepared from the three process modifications, except for a minor reduction in tear strength.

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Organic material dissolved during oxygen-alkali pulping of hot water extracted birch sawdust

TAPPI Journal ◽

10.32964/tj14.4.237 ◽

2015 ◽

Vol 14 (4) ◽

pp. 237-244 ◽

Cited By ~ 1

Author(s):

JONI LEHTO ◽

RAIMO ALÉN

Keyword(s):

Acetic Acid ◽

Betula Pendula ◽

Cooking Time ◽

Hot Water ◽

Partial Hydrolysis ◽

Chemical Pulping ◽

Black Liquors ◽

Aliphatic Carboxylic Acids ◽

Hydrolysis Of ◽

Cooking Conditions

Untreated and hot water-treated birch (Betula pendula) sawdust were cooked by the oxygen-alkali method under the same cooking conditions (temperature = 170°C, liquor-to-wood ratio = 5 L/kg, and 19% sodium hydroxide charge on the ovendry sawdust). The pretreatment of feedstock clearly facilitated delignification. After a cooking time of 90 min, the kappa numbers were 47.6 for the untreated birch and 10.3 for the hot water-treated birch. Additionally, the amounts of hydroxy acids in black liquors based on the pretreated sawdust were higher (19.5-22.5g/L) than those in the untreated sawdust black liquors (14.8-15.5 g/L). In contrast, in the former case, the amounts of acetic acid were lower in the pretreated sawdust (13.3-14.8 g/L vs. 16.9-19.1 g/L) because the partial hydrolysis of the acetyl groups in xylan already took place during the hot water extraction of feedstock. The sulfur-free fractions in the pretreatment hydrolysates (mainly carbohydrates and acetic acid) and in black liquors (mainly lignin and aliphatic carboxylic acids) were considered as attractive novel byproducts of chemical pulping.

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Effect of Hot-Water Blanching Pretreatment on Drying Characteristics and Product Qualities for the Novel Integrated Freeze-Drying of Apple Slices

Journal of Food Quality ◽

10.1155/2018/1347513 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 8

Author(s):

Hai-ou Wang ◽

Qing-quan Fu ◽

Shou-jiang Chen ◽

Zhi-chao Hu ◽

Huan-xiong Xie

Keyword(s):

Electron Microscopy ◽

Freeze Drying ◽

Hot Water ◽

The Novel ◽

Rehydration Ratio ◽

Drying Time ◽

Drying Characteristics ◽

Promising Alternative ◽

Freeze Dried ◽

Apple Slices

The effect of hot-water blanching (HWB) on drying characteristics and product qualities of dried apple slices with the novel integrated freeze-drying (NIFD) process was investigated by comparing with 3 different FD methods. Compared with the NIFD process without HWB pretreatment (VF-FD), the NIFD process with HWB pretreatment (HWB-VF-FD) resulted in a significantly higher mass loss and more sufficient freezing in vacuum-frozen samples, significantly higher rehydration ratio (RR), higher shrinkage ratio (SR), smaller Vitamin C (VC) content and lower hardness and better apparent shape in freeze-dried samples, and fewer change to the color of the dried or rehydrated samples (p<0.05). Compared with the conventional FD process with HWB pretreatment (HWB-PF-FD), HWB-VF-FD cost significantly less processing time and FD time and obtained significantly higher RR (p<0.05), almost the equivalent SR, VC content, and hardness, and similar appearance in dried samples. The microstructure of apple cell tissues was analyzed by transmission electron microscopy and scanning electron microscopy to interpret the above differences in drying characteristics and product qualities. The results suggested that the NIFD process of apple slices with HWB pretreatment was a promising alternative method to decrease drying time, achieve similar product quality, and simplify the process steps of the conventional FD technology.

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