Alkali consumption of aliphatic carboxylic acids during alkaline pulping of wood and nonwood feedstocks

The carbohydrate degradation products have been examined, which are formed during the conventional kraft pulping of a softwood, hardwoods, bamboo, and wheat straw as well as soda and soda-anthraquinone pulping of wheat straw. The focus was on “volatile” acids such as formic and acetic acids and “ nonvolatile ” hydroxy monocarboxylic and dicarboxylic acids. The different consumption profiles were obtained for the charged alkali required for the neutralization of these aliphatic acids depending on the feedstock and the cooking method. The relative composition of the acid fraction in the black liquors of softwood and hardwood and nonwood feedstocks showed characteristic variations. However, in the case of wood kraft pulping, the variations in cooking conditions (effective alkali 19 – 21 % and cooking temperature 155 – 170 ° C) had no significant effect on the acid composition. The total amount of volatile and hydroxy acids formed during pulping at a typical target κ number level for each feedstock ranged from 78 to 174 kg ton -1 based on o.d. feedstock. It was highest in birch kraft pulping and lowest in wheat soda-anthraquinone pulping.peerReviewe

Role of lignin and sodium carbonate on the swelling behavior of black liquor droplets during combustion

A partial removal of lignin from black liquor (BL) by carbonation and lignin precipitation was studied. In lignin-lean BL droplets during combustion in a laboratory furnace at 800°C in stagnant air, the maximum swelling was decreased. This observation was interpreted as showing that the lignin content decrement is due mainly to removal of higher molar mass (HMM) lignin and that the Na2CO3 content of the BL is increased. Stepwise precipitation experiments with industrial softwood and hardwood kraft BLs by carbonation (resulting in pH decrement from 13 to 9) indicated that a fraction of HMM lignin (MM >10 kDa) with a higher amount of carbohydrates precipitated more prominently and earlier than the fraction with lower molar mass (LMM) lignin (MM 10 kDa) and BL-originated aliphatic carboxylic acids were performed and found that the mixture of medium MM fraction (MM 5–10 kDa) swelled more than the other lignin fractions. The addition of Na2CO3 to BL also reduced the maximum swelling of a BL droplet.peerReviewe

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.peerReviewe

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.peerReviewe

Combustion properties of spruce black liquor droplets : Sulfur-free pulping and influence of hot-water pretreatment

Hot-water pretreatment of lignocellulosics prior to sulfur-free alkaline pulping is an interesting approach for recovering value-added carbohydrate- and lignin-derived materials. This paper investigated the chemical composition variations and combustion properties of the black liquors (BLs) from three different cooking processes: two sulfur-free soda-anthraquinone (soda-AQ) and oxygen-alkali (O2-NaOH) cooks and kraft cook, before and after hot-water pretreatment of the spruce sawdust. Relatively less aliphatic acids but more lignin were present in the BLs after hot-water pretreatment as cooking time prolonged. In general, the burning time decreased as follows: soda-AQ BL > O2-NaOH BL ≅ kraft BL. With the same cooking time, the increase in the total burning time for soda-AQ BLs compared with kraft BLs was 11-17% (without pretreatment) and 25-39% (with pretreatment). Compared to kraft BLs with the same cooking time, the swelling for soda-AQ and O2-NaOH BLs decreased by 8-25% and 4-23%, respectively.peerReviewe

A comparative study of advanced oxidative processes : Degradation of chlorinated organic compounds in ultrafiltration fractions of kraft pulp bleaching effluent

Oxidative pre-treatment methods such as the Fenton oxidation, ozonation, and photocatalytic treatment have been compared in reducing adsorbable organic halogens (AOX) and chlorophenolic compounds in untreated kraft pulp bleaching effluent. Their efficiency was also studied on effluent ultrafiltration fractions. The Fenton treatment removed all analyzed chlorophenolic compounds from the effluent. Ozonation and photocatalysis appeared to be much less effective methods. The efficiency of the Fenton oxidation appeared to be more pronounced in higher molecular weight effluent fractions. This suggests a novel design, where the filtration stage can be placed after the oxidation, and the high- -molecular weight fraction is returned to the Fenton treatment.peerReviewe

Molecular spectra of liquors as method of studying delignification process

FTIR-spectra of dried compounds of black liquors after aspen kraft cooks of different duration were obtained. Twelve samples corresponding to changing H-factor value in limits 4-1010 were investigated. The parameters of selected bands corresponding to lignin fragments vibrations were calculated using mathematical treatment methods. It was revealed that the positions and bandwidths of these lignin bands did not change. During cook at the first stage (H-factor values 4-200) their intensities strongly increased with different rates. During the next time period when the H-factor values were more than 200 a slow phase with small changes of the bands intensities were revealed. The IR-spectra of black liquors can help to understand kinetic of hardwood kraft cook in detail throughout evaluating content and structure of dissolved lignin using bands intensities.peerReviewe

Increasing survival and growth of Scots pine seedlings with selection based on autumn coloration

This study evaluates the possibility of using autumn coloration of young Scots pine (Pinus sylvestris L.) seedlings as an indicator of adaptation to harsh climate conditions. One-year old seedlings from natural stands with different origins and seed orchards were classified as “red/reddish” and “green” based on the needle color after artificially increased night length in nursery and then measured after 14 years in field trials. In almost all the studied groups seedlings classified as “red/reddish” had significantly higher survival rate than seedlings classified as “green”. The survival of “red/reddish” was 14.2% higher than “green” among natural stand seed material and 56.2% among seed orchard material. During the study period the survival difference between “red/reddish” and “green” seedlings tended to increase. The seedling color had limited connection with the height growth, even though the trees classified as “red/reddish” were slightly taller than those classified as “green”. However, the total productivity over all field trials, described here as a heightsum, of “red/reddish” trees was 15% higher than productivity of “green” trees from natural stand material, and 61% higher than those from seed orchard material. It seems that controlled selection based on autumn color can be utilized within seed crops of different types with the aim to increase the adaptability of seed material to different environmental conditions.</ja:p

Chemical Characterization of Okra Stalk (Abelmoschus esculentus) as Potential Raw Material for Biorefinery Utilization

In the present work, okra stalk (Abelmoschus esculentus) was chemically characterized to evaluate its appropriate exploitation as a biorefinery feedstock. The chemical composition of this renewable lignocellulosic material yielding maximum up to 120 tons per hectare was primarily determined by methods of wood chemical analysis. In terms of its main organic constituents, its dry matter contained 65.0% carbohydrates (cellulose, hemicelluloses and other polysaccharides), 20.5% lignin and 5.0% extractives. In addition, thermogravimetric analyses revealed that the content of proteins and inorganics was 6.6 and 3.3% of the dry matter, respectively. Among the inorganic elements determined by inductively coupled plasma atomic emission spectroscopy, calcium was shown to be the dominant one, with a concentration of 17.2 mg/g, followed by magnesium, silica and potassium. The analytical data indicated that the stalk of okra plant with a high crop yield would be a potential feedstock as such or together with other similar feedstocks for versatile biorefinery purposes, including pulping and manufacturing of chemicals.peerReviewe