Delignification Rate Research Articles

アルカリ・メタノール・アントラキノン蒸解 （第１報） 脱リグニン速度と選択性

The AMA (alkali-methanol-anthraquinone pulping) process was invented by Z. Abe of Kyushu University in 1982. The Organocell process was improved and changed to the same pulping process as AMA process. On Sept. 1992, Organocell started up a 150, 000 ton/yr Organocell mill in Germany.This investigation was carried out to get a better understanding about AMA. Delignification rates and selectivity in AMA were compared with these in kraft, alkali-methanol, and soda-anthraquinone pulping. Methanol extractives-free wood meal (24-48 mesh) of beech (Fagus crenata) and pine (Pinus densiflora) were used as raw materials. Each pulping was done under the same active alkali charge.The results were summarized as follows :(1) The delignification rate in AMA was faster than twice of that in kraft pulping.(2) Methanol and anthraquinone, respectively, accelerated the delignification in AMA.(3) Softwood as well as hardwood as raw materials was easily pulped by AMA.(4) The selectivity of AMA was better than that of kraft, alkali-methanol, and soda-anthraquinone pulping.(5) AMA process seems to be the best alternative to kraft pulping process.(6) The main subjects on AMA process are left as follows ; washing process, bleaching process and sequences, mechanism of delignification and pulping, chemicals recovery process, economic evaluation.

The Difference of Reactivity between Syringyl Lignin and Guaiacyl Lignin in Alkaline Systems

The difference of reactivity between syringyl lignin and guaiacyl lignin in alkaline systems were investigated by using syringyl and guaiacyl types of β-aryl ether lignin model compounds, softwood and hardwood dioxane lignins, and softwood and hardwood meals. In the lignin model study, β-aryl ether of syringyl lignin model was cleaved much faster than that of guaiacyl lignin model by soda and soda/anthraquinone treatment. The formation of coniferyl alcohol and sinapyl alcohol from guaiacyl lignin model and syringyl lignin model, respectively, was almost proportional to the cleavage of β-aryl ether under these conditions. Based on the model studies, coniferyl alcohol and sinapyl alcohol from isolated lignin and protolignin by soda and soda/anthraquinone treatments were determined in order to evaluate the extent of β-aryl ether cleavage in the terminal units of lignin. The results in both the dioxane lignins study and the wood meals study also indicate that β-aryl ether of syringyl lignin is cleaved much more easily than that of guaiacyl lignin and that there is no difference of reactivity of guaiacyl lignin in hardwood lignin and softwood lignin. This high reactivity of syringyl lignin may contribute the faster delignification rate of hardwood than softwood.

Kinetics of Neutral Sulfite Semichemical and Neutral Sulfite Semichemical-Anthraquinone Pulping

Abstract Delignification rate expressions for neutral sulfite semichemical (NSSC) and neutral sulfite semichemical anthraquinone (NSSC-AQ) pulping of black spruce have been developed. The rates take into account the effects of temperature and reaction times on the rates of delignification. NSSC in this study is defined by an alkali ratio [sodium sulfite/(sodium sulfite + sodium carbonate)] of 0.60 (expressed as sodium oxide) giving a final pulp yield between 55 and 60%. NSSC-AQ is identical to NSSC with the addition of anthraquinone. Reaction temperature and pulping chemical concentrations were held essentially constant in all kinetic experiments. Isothermal experiments were conducted in the temperature range between 165 and 180°C. A concentration of 150 g/L sodium sulfite with a liquor to wood ratio 62 were used.

Spectroscopic studies of bagasse butanol lignin

The IR spectra from 200 to 4000 cm −1 were studies of lignin precipitated from waste black liquor produced from the pulping of bagasse with butanol-water (1:1). The effect of different variables in the pulping process, such as temperature, time, additives and the kind of pulping process on the IR spectra of precipitated lignin were clarified. In general, increase in pulping temperature and time of organosolv pulping increases the degradation of precipitated lignin and the CO intensity increases. The addition of sodium hydroxide to organosolv pulping liquor enhances the rate of delignification and the lignin produced is less degraded. On the other hand, lignin produced from soda and kraft pulping processes is also less degraded than the lignin produced from the organosolv pulping process without the addition of sodium hydroxide. The absorbance bands of the various lignin groups, such as methoxyl, hydroxyl and carbonyl relative to the aromatic ring band at 1505 cm −1 were correlated to provide more information on the molecular structure changes of the butanol-water organosolv lignin.

A percolation-theory model of lignin degradation

Lignin removal during pulping is the result of the chemical degradation of two distinct cross- linked lignin gel fractions (middle lamella and secondary wall) of different polydispersities, the values of which can be predicted by gelation models. Values of the cluster-size (polydispersity) exponent, T, were calculated using molecular-weight and gel-fraction scaling exponents obtained from the degradation data of five lignin-type models and seven pulping experiments. Results for the middle lamella agree with percolation- theory predictions (T = 2.17) for three-dimensional condensate gels. Also, low values of the cluster-size exponent obtained during secondary-wall degradation in whole wood were in agreement with predictions given for either three-dimensional diffusion-limited cluster-cluster aggregation processes (T = 2.00), or with percolation-theory predictions (T = 2.05) for networks arranged in two-dimensional monolayers. However, the degradation behavior of secondary-wall lignin during pulping of wood meal and sawdust was better described by the Flory-Stockmayer model of gelation (T = 2.501, a model which is applicable to networks having a low cross-linking density. Results for lignin-type model compounds were also interpreted with percolation and cluster-cluster aggregation models. 1.1. Delignification and Lignin Degradation. Lig- nin may be considered to be a cross-linked amorphous polymer network, or gel, of trifunctional monomers spanning two different regions of the fiber wall, which are the middle lamella and the secondary wall. The physical structure of these regions is different, and it is generally assumed that the local lignin structure reflects this difference. The respective rates of delignification of these two regions are indeed quite variable, and those variations are a function of pulping chemistry. In addition, the mac- romolecular properties of soluble (sol) lignin fragments resulting from the degradation of each network are also dissimilar and may be a function of the morphology of the network. Degradation corresponds to the breakdown of the lig- nin network per se in both the middle lamella and the secondary wall regions of the fiber; delignification, on the other hand, is the subsequent removal of soluble lignin fragments from both regions. Lignin degradation char- acteristics have been described by Szabo and Goring' with some success using the Flory theory of gelation,2 in combination with the topochemical model of delignifica- tion,l which empirically predicts the selective removal of treelike lignin fragments from the two regions. This selective removal was first observed by Bixlere3 The Flory theory assumes that intramolecular linkages are absent from the network. However, current knowledge about the nature of native lignin indicates that many lignin fragments do not have a treelike structure and have a significant amount of intramolecular linkages. In the present work, lignin degradation will be analyzed in terms of modern percolation concepts4* and compared to other suitable ge- lation models such as diffusion-limited cluster-cluster aggregation (CCA),4b*c the theory of which is well developed for rigid4blc cross-linked networks. It will be shown that there is good quantitative agreement between the prop- erties of flexible lignin fragments and those predicted by percolation theory for cross-linked networks of different polydispersities. Qualitative agreement with results pre- dicted by cluster-cluster aggregation for rigid networks will also be discussed.

Isothermal Reaction Kinetics of Kraft Delignification of Douglas-Fir

Abstract Kraft delignification of Douglas-fir (Pseudotsuga menziesii) wood meal was carried out under an instantaneous isothermal condition with a liquor-to-wood ratio of 50 to investigate the effects of reaction temperature and chemical concentration on the rate of delignification. The temperatures studied were in the range of 120 to 175°C. Three levels of [HO−l] and three levels of [HS−l] concentrations were investigated. In each case an efficient mechanical agitation of the pulping liquor was maintained and the delignification was extended to reach its completion. Using a nonlinear regression analysis on the delignification results, a single kinetics equation was resolved to describe the effect of temperature and chemical concentration on the rates of delignification for the initial, bulk, and final phases. This equation also revealed that the amounts of lignin removed due to the chemical reactions in the initial, bulk, and final phases were 18.8, 71.4, and 3.8%, respectively. About 6% of the total lignin was dissolved into the pulping solution before any significant chemical reaction occurred to the lignin core. The activation energies of delignification reactions in the initial, bulk, and final phases were 85.8, 123.8, and 110.0 kJ/mole, respectively. The Ln(pre-exponential factors) were 22.5, 30.5, and 23.4 m−l1 for the initial, bulk, and final phases, respectively. The rate of delignification was strongly affected by the presence of [HO−l] in the bulk and final phases. Whereas, [HS−l] had a significant effect on the rate of delignification only in the bulk phase. These chemical effects were also quantified.

カルボキシメチル化及びメチル化によるＴＭＰの保水値とシート強度の挙動

The object of this paper is to examine the influence of the changes in water retention value (WRV) of Douglas fir TMP by post-chemical substitution on the sheet density and the sheet strength.TMP classified 42 wire mesh was modified by carboxyme-thylation and methylation to the various degree of substitution. Then, yeild, degree of substitution (DS) of the introduced groups, WRV, heat of wetting, crystallinity, sheet density and sheet strengths of each modified TMP were determined.The following results were obtained.1. Weight increase of TMP after carboxymethylation or methylation increased only a little and the rate of delignification during these reaction was relatively small.2. WRV and heat of wetting of carboxymethylated TMP (CM-TMP) increased with an increse in DS of carboxymethyl group, while methylated, TMP (M-TMP) gave the maxima of WRV and heat of wetting at 0.37 of DS of methoxyl group. WRV of CM-TMP showed the greater value than that of M-TMP.3. The crystallinity of CM-TMP and M-TMP fibers decreased with an increase in DS of carboxymethyl or methoxyl group. The decrease of crystallinity becomes more remarkable by carboxymethylation than by methylation.4. Density of CM-TMP handsheets increased with an increase in WRV, while the density of M-TMP handsheets showed a maxima at 0.82 of DS of methoxyl groups.5. An increase in TMP sheet density caused by the carboxymethylation and methylation results in the increase in tensile strength and burst factor of the handsheets. The both strengths of M-TMP showed a maximum at 0.37 of DS of methoxyl group. On the other hand, it was found that CM-TMP or M-TMP handsheets showed a maximum value with the tear factor.6. It can be seen from the scanning electron photomicrograph that the enhance in TMP flexibility and conformability followed by swelling with the process of carboxymethylation or methylation results in increase in the relative bonded area between the fibers in the handsheets.

Soda-anthraquinone pulping of sorghum stalks

Soda-AQ pulping of sorghum stalks increased the rate of delignification and the pulp yield and improved the strength properties compared to soda pulping, but the effect of AQ addition (0·13% on oven-dry raw material) was less pronounced than for tropical hardwoods. The wet-depithing of the stalks contributed considerably to the yield and strength properties, while the alkali consumption and rejects were decreased. Addition of guar gum (0·5% on oven-dry pulp), after beating, as wet-end/dry-strength agent, improved the drainage and strength properties. The soda-AQ pulping makes pulping of sorghum stalks much more attractive and feasible, once the other technical constraints are overcome by employing the recent techniques developed for other agricultural residues.

ＴＭＰの保水値とシート強度のサルファイト蒸解による変化

The object of this paper is to examine the influence of the changes in WRV of TMP follwed by post-sulfite cooking on the sheet density and the sheet strength.TMP classified over 42 wire mesh were treated with three types of sulfite liquor ranging from pH 4 to pH 13. Then, yield, sulfur content, water retention value, heat of wetting, crystalline index, sheet density and sheet strength were determined with the post-cooked TMP. The following results were obtained.1. Yield was greater than 77%. Sulfur content showed small value, for instance, it showed only 0.52% for TMP treated for 3 hrs. with alkaline sulfite. TMP treated with alkaline sulfite has relatively greater sulfur content than those with bisulfite and neutral sulfite. Yield of TMP post-cooked with alkaline sulfite, with neutral sulfite and bisulfite decreased in that order. Changes of pentosan content by the sulfite cooking were relatively few compared with those of lignin. The rate of delignification in bisulfite cooking was much higher than those in neutral and in alkaline sulfite cooking. About 30% of lignin were eluted out for 3 hrs..2. TMP post-treated with alkaline sulfite and bisulfite had greater WRV than those with neutral sulfite. TMP post-treated with sulfites for 3 hrs. showed WRY of 140 to 158%.3. Apparent density of the TMP handsheets increased with an increase in WRV. Those with alkaline sulfite showed the greatest value. The apparent sheet density were highly dependent on pH during post-sulfite cooking compared with sulfo group content.4. An increase in TMP sheet density caused by the post-sulfite cooking results in an increase in tensile strength and in burst factor of the sheets. When comparing at the same yield, TMP post-treated with neutral sulfite showed a greater strength than those with alkaline and bisulfite. On the other hand, TMP post-treated with alkaline sulfite showed a maximum value with the tear factor.5. It can be seen from the scanning electron photomicrograph that the enhance in TMP flexibility and conformability followed by swelling with the progress of the post-sulfite cooking results in an increase in the number of fiber to fiber bonds.

Alkaline Sulfite-Anthraquinone Pulping of Bagasse

Depithed Mexican bagasse was pulped by using the alkaline sulfiteanthraquinone pulping process. The effects of the addition of small amounts of ethanol and varied amounts of AQ as well as different alkali ratios were investigated. 20 minute cooking time results in pulps with good yields, high brightness and excellent strength properties. Despite of the short cooking time, delignification can be performed to extremely low kappa numbers without pulp degradation which provides and easy bleaching. The addition of a small amount of ethanol retards the delignification rate and increases the rejects and the strength properties of the pulp, but after bleaching the improvement in strength is negligble. With respect to yield, reject content and physical properties of the pulp, the optimum alkali ratio (Na_2SO_3: total alkali) is 0.75 and the favourable amount of AQ is 0.05 to 0.1% based on o.d. bagasse. Pulp bleaching can be done in two or three stages with chlorine or hypochlorite yielding high brightness and good pulp strengths.

Reaction kinetics in oxygen bleaching

AbstractThe oxygen bleaching of wood pulp takes place in a heterogeneous system involving oxygen (gas), water (liquid), and fiber (solid). Inconsistent effects of process variables (reaction temperature, alkali concentration, and oxygen pressure) on the overall oxygen delignification rate of wood pulp in various reacting systems have been reported in the literature.An apparent intrinsic reaction rate model, excluding the interphase mass transfer effects, has been developed based on oxygen bleaching experiments in an agitated and ultralow‐consistency (solids content) reactor. The apparent intrinsic reaction rate model shows a faster delignification rate than those reported in the literature. The degree of inadequate delignification observed in the literature data is likely to be caused by insufficient mass transfer of bleaching chemicals to fibers.

アルカリ性サルファイト・キノン蒸解におけるリグニンの挙動

The sulfite-quinone cooking has been investigated as an alternative to the kraft process in terms of delignification, pulp yields, and pulp qualities. However, behaviors of lignin in this cooking have not been clarified, and there are few studies in which delignification selectivity and pulp qualities were compared at given delignification rates and H-factors with those of the soda-quinone and the kraft-quinone cookings. In this study, yezo spruce/saghalien fir mixed chips and beech chips were cooked by the three kinds of cookings under the conditions where the delignification at a given H-factor (cooking temp. : 170°C cooking time : 2 h) were equal. Pulp yields, handsheet strength properties, and characteristics of lignins in those pulps and black liquors were compared, and behaviors of lignin and mechanism of delignification in the sulfite-quinone pulping were discussed. In these experiments, 1, 4-dihydro-9, 10-dihydroxyanthracene sodium salt (DDA) was used as a quinone additive, and this sulfite-quinone cooking was called the alkaline sulfite-DDA cooking because sodium hydroxide, sodium sulfite, and DDA were used as cooking chemicals. The results are summarized as follows : (1) The alkaline sulfite-DDA cooking of yezo spruce/saghalien fir wood gave pulp of almost the same kappa no. 50 as the soda-DDA and the krart-DDA cookings. At kappa no. 50, the total pulp yields of the former were higher than those of the latter. However, the screened pulp yields of the alkaline sufite-DDA cooking were almost the same as those of the kraft-DDA cooking and slightly lower than those of the soda-DDA cooking because of its higher yields of screen rejects.(2) This cooking of beech wood gave pulp of kappa no. 26.4, but it had no advantage of pulp yields compared with the soda-DDA and the kraft-DDA cookings.(3) The contents of sulfonic acid group of lignin in pulps given by this cooking were about 0.1-0.2/phenyl propane unit.(4) Handsheet strength properties of this cooking were almost the same as those of the kraft-DDA cooking.(5) Gel chromatography indicated that the dissolved lignin of this cooking was richer in low-molucular lignin fractions than those of the other cookings.(6) Alkaline nitrobenzene oxidation of screened pulps and black liquors of this cooking gave higher yields of vanillin (soft wood) or vanillin and syringaldehyde (hard wood) than those of the others.(7) In the alkaline sulfite-DDA cooking, the condensation of lignin was depressed by the addition of sodium sulfite. This must be a reason why delignification is accelerated together with the increase of solubilyty of lignin with the cleavage of β-ether linkages by quinone compounds and the sulfonation by sulfite.

コバルト錯体添加酸素アルカリ蒸解 かくはん速度の脱リグニンにおよぼす影響

In order to clalify the effects of agitation rate on the oxygen delignification of white birch Asplund pulp, the relationship between the change of oxygen content in a cooking liquor during the course of cooking under a constant oxygen pressure and Kappa number of the pulp was investigated.The rapid consumption of oxygen dissolved in cooking liquor resulted from the significant increase in the delignification rate during the early stage by the addition of Co-salen [Cobalt (II) Bis-(salicylidene)-ethylenediamine] as a oxidizing catalyst.(Table I and Fig. 3). Thus, the dissolved oxygen content decreased, and the pulp was under oxygen shortage temporarily in the case of the agitation rate below 300rpm.(Fig. 2). But the delignification rate was slowed down during the late stage of cooking, compared with the early stage, and the consumption of oxygen was decreased simultaneously.(Fig. 3). The oxygen content in cooking liquor was increased cosequently and kept constant at various levels during the late stage.(Fig. 2).Therefore, it needed a high agitation rate to compensate for the rapid consumption of oxygen during the early stage of delignification. But the agitation rate could be decreased considerably on the late stage.(Fig. 4).This phenomenon was confirmed by investigating the correlation of the oxygen pressure, instead of the agitation rate, to the delignification.(Fig. 5).

Oxidative Pretreathent with Hydrogen Peroxide Prior to Alkaline Pulping

Abstract Oxidative pretreatment of Southern pine wood with alkaline hydrogen peroxide increased its rate of delignification during subsequent kraft and soda-AQ pulping. Effective pretreatment required the removal of transition metals prior to oxidation at high pH (12), low teaperature (50°C) and short reaction time (<45 min.). Compared with reference pulping, pretreatment with 1.4% H2O2 and 3.3% NaOH on wood reduced pulping time to 35 kappa number by 30 minutes (at 170°C). Pre-oxidation resulted in pulp with yield-kappa number and viscosity-kappa number relations equal to or greater than those of corresponding reference pulp. For both kraft and soda-AQ pulp, bleachability, in terms of chemical charge and final viscosity, was unaffected by pre-oxidation while total bleached yield was increased by about 2% on wood. Handsheet strengths for unbleached and bleached kraft pulp were unaffected by oxidative pretreatment whereas those for unbleached soda-AQ pulp were improved to kraft-like levels. However bleached...

針葉樹材および広葉樹材のアルカリ性サルファイト・キノン蒸解における脱リグニン速度 ソーダキノンおよびクラフト蒸解との比較

The delignification rate constants were calculated as observed (pseudo) first-order reactions, and the effects of [OH-] and [SO32-] on the rate constants were evaluated in the Salkaline sulfite cooking with and without DDA (1, 4-dihydro-9, 10-dihydroxy-anthracene sodium salt). The delignification rates were also compared with those for kraft and kraft-DDA cookings.In the alkaline sulfite-DDA cooking of spruce and beech wood meals under the same conditions, the delignification rate constants for beech were not necessarily higher than those for spruce wood meals. This is quite different from the general observation for the soda, soda-DDA, kraft, kraft-DDA cookings, in which beech is higher than spruce. Especially in the case of beech, the delignification was not accelerated when the sodium sulfite concentration was increased from 0.4 M to 0.8 M. The addition of DDA could increase the effect of [32-] on the delignification in the alkaline sulfite cooking while it was not the case for [SH-] in the kraft cooking. Total alkali charge was higher in the alkaline sulfite-DDA cooking than those in the soda-DDA, kraft, kraft-DDA cookings to have a given rate constant.

針葉樹材のキノン添加亜硫酸ナトリウム・ホルムアルデヒド蒸解

A new cooking process with sodium sulfite, formaldehyde, and a quinone compound (1, 4-dihydro-9, 10-dihydroxyanthracene sodium salt: DDA) was devised in order to produce soft wood semichemical and chemical pulps which are superior to neutral sulfite and kraft pulps, respectively. In this studies, this process was evaluated in terms of the optimum compositions of cooking liqnor, delignification selectivity, and pulp qualities.The results were as follows:(1) The addition of formaldehyde to a sodium sulfite-DDA solution accelerates delignification of yezo spruce. The optimum molar ratio of formaldehyde to sodium sulfite for delignification is in the range of 0.15-0.70.(2) Delignification selectivity in sodium sulfite-formaldehyde-DDA cooking is better than that in neutral (weakly alkaline) sulfite-DDA cooking. Lignin-free yields by the former cooking are 2-5% higher than those by the latter at a given delignification.(3) Delignification rate of yezo spruce in this cooking is comparable to that in kraft-DDA cooking, when the dose of DDA is increased to 0.5% on o.d. wood. Lignin-free yields by the former are 9-10% higher than those by the latter at a given delignification.(4) Yezo spruce/saghalien fir pulp produced by this cooking has higher tensile and burst indices, and higher brightness than kraft-DDA pulp.

酸化鉄法直接か性化技術 Ｉ ソーダキノン蒸解 ２ Ｌ材のソーダキノン蒸解

Laboratory studies for direct causticizing process by ferric oxide in soda quinone pulping of hardwoods (eucalyptus, beech and oak) were carried out in comparison with kraft and borate kraft pulping. DDA was used as quinone with addition of 0.05-0.15% as AQ by weight on wood. Pulp yield and Kappa number were determined, and the quinone addition of 0.05-0.1% in soda quinone pulping increased the delignification rate to equal that of kraft and borate kraft pulping at the sulfidity of 25% without reducing pulp yield. Bleachability of sode quinone pulp was slightly lower than that of kraft and borate pulp except beech pulp, and the viscosity of bleached soda quinone pulp was 2-6 cp lower than that of kraft pulp. The pulp properties of soda quinone pulp were nearly equal to those of kraft and borate kraft pulp. The difference of pulp properties of soda quinone and kraft pulp of hardwoods are smaller than those of softwoods in previous report.

Degradation of Lignin by Cyathus Species

The ability of 12 Cyathus species to degrade C-labeled lignin in kenaf was studied. The sum of C released into solution plus C released into the gas phase over a 32-day fermentation period was used to determine average daily rates of lignin biodegradation. Cyathus pallidus. C. africanus, and C. berkeleyanus delignified kenaf most rapidly. C. canna showed the greatest preference for lignin degradation over other plant components, and its rate of lignin degradation was only slightly lower than the three most active species. The apparent ability of fungi to metabolize low-molecular-weight lignin breakdown products correlated well with their overall delignification rates. C. stercoreus metabolized degradation products of lignin from wheat straw better than those from kenaf lignin, based on the amount of low-molecular-weight products left in solution.

シミュレーションによるＫＰ蒸解条件の考察

This report concerns applications of cooking reaction rate equations developed from the data based on 3n typed orthogonal arrays to some cases of kraft pulping. First, the correlation of mill chip thickness with hand made chip thickness was determined by cooking experiments and the corresponding calculations. Second, the optimum cooking conditions were discussed to be expected increasing carbohydrate yield. In one case, taking the selectivity coefficient as a parameter, (CH.)-(T. L.), the best condition for each variable was proved. In another case, taking the ratio of decarbohydrate rate to delignification rate, VcH./VT. L., some interesting trends for cooking conditions were obtained. Two Temperature cooking and Injection cooking were verified as profitable methods in increasing carbohydrate yield. Third, it was pointed out that the deviation of chip thickness in mill chips must be the cause in decreasing carbohydrate yield.

クラフト蒸解に関する速度論的研究 ＩＶ 脱リグニン挙動の速度式による記述

It is known that the kraft cook can be separated into three stages; initial phase, bulk delignification phase and final phase. A chemical reaction is a rate-determining step for delignification under the condition in which the chip thickness is below certain value, except in the initial phase. Delignification rate in the two stages, bulk delignification phase and final phase, was studied.Assuming that the delignification is reversible reaction, it was found that the delignification rate in the two stages, bulk delignification phase and final phase, could be expressed as a single kinetic equation. In addition, the effect of reaction temperature and concentration of cooking chemicals on the delignification rate was revealed quantitatively. The rate equation, which was established in the previous report for effective alkali consumption by wood components, was applied to the kinetic equation of delignification in order to determine the numerical solution. These numerical solutions fit to the experimental results successfully. While this method involves some assumption, it is useful to describe the delignification rate quantitatively under the condition of timevarying liquor concentration.