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最近の世界的傾向として，特に北欧では回収ボイラーへ供給する燃焼黒液の濃度を高め，その発熱量を高くしてボイラーでの蒸気発生量を増大し，石化燃料の減少を達成している。我国における黒液の燃焼濃度は72―73％が主流であるが，これを75―80％に上昇させ省エネルギを図っている。中には85％で運転している工場も存在する。これら燃焼黒液濃度は黒液エバポレータで達成されるが，80％以上の高濃度を可能にしたのは晶析技術の開発による。Andritz社は黒液濃縮には多大の実績を有するが，15年前にこの技術開発に着手し，その技術を完成させ，既に20プラントを超える晶析技術を適用した高濃度エバポレータを納入している。晶析技術の概要は，回収ボイラーの電気集塵機で捕集されたESP灰を黒液に混合して濃縮するもので，濃度上昇と共に析出して来るナトリウム塩がESP灰の粒子に付着して成長するものである。つまり，ESP灰は種晶として機能する。又，黒液は濃度上昇と共にその粘性係数が高くなるが，高温処理による粘度低下によって高濃度濃縮を可能にする。

The optimal conditions of isothermal cooking (ITC) for yield improvement of hardwood kraft pulp were established using Acacia mearnsii wood in a laboratory. The addition of both 1% sulfur and 0.04% soluble anthraquinone on wood gave an about 4.5-5% higher pulp yield at a kappa number of about 17. The highest yield was obtained when 70% of total active alkali and 100% of both PS and AQ were added at the beginning, and successively, black liquor was exchanged with fresh white liquor containing the remaining 30% of total active alkali just after the cooking temperature reached 135°C. A linear correlation was observed between pulp yields and ratios of xylose to glucose (X⁄G ratios) , liberated from the pulps by an acid hydrolysis. This result means that a pulp yield can be estimated by knowing an X⁄G ratio of the pulp. However, it was indicated that the linear correlation for Acacia mearnsii can not be applied to cooking of different wood species.

In order to provide and share the technical information among Japanese pulp and paper industries. Pulping Technical Committee surveyed chemical recovery process operation in kraft mills of '99 fiscal year (Apr.'99 to Mar.'00), following the survey of kraft fiberline operations of '98. We received the answers from 33 mills, except one mill, out of 34 domestic kraft mills.This report summarizes result of the above investigation, concerning operational conditions and equipment of chemical recovery process which covers black liquor evaporator, recovery boiler, recausticizing and lime calcining.

In the kraft pulp making process, extracted lignin liquid (black liquor) contains various surfactive materials which are derived from lignin. That means black liquor tends to make foam so easily that the kraft pulp making process is troubled with foam at any time. If amout of foam occured, the efficency of brown stock washer would decrease and the whiteness of pulp would be under the fixed level. Furthermore. operation speed of brown stock washer would lower, which means the efficiency of pulp manufacuturing would decrease. There are mechanical method and chemical method for the foam trouble prevention. In the kraft pulp making process, chemical method is mainly adopted.

Life cycle environmental loads for woodfree paper containing nonwood pulp or deinked pulp were investigated (Environmental loads: CO2, SOx, NOx, and incineration ash). In this study, inventory data concerning wood pulp and deinked pulp were collected at Mitsubishi paper mill in Hachinohe. With regard to the inventory for nonwood pulp, data for bagasse pulp produced in Colombia and data for kenaf pulp produced in Japan were used. Environmental loads for woodfree paper made from the mixture of wood pulp and nonwood pulp or deinked pulp was compared with those for woodfree paper made from 100% wood pulp.CO2 emission for life cycle of woodfree paper containing bagasse pulp (except CO2 emission from the pith burning) was as large as that of woodfree paper made from 100% wood pulp, because the pith contained in bagasse may be regarded as the agricultural by-product. Since kenaf pulp was produced at the small pulping plant that has no energy recovery system from black liquor, CO2 emission for woodfree paper containing kenaf pulp was larger than that of other kinds of woodfree paper. In case of deinked pulp, the increase in content of deinked pulp in woodfree paper increased the consumption of fossil fuel, resulted in the increase of CO2 emission from fossil fuel. SOx emission for woodfree paper containing deinked pulp was smaller than that of other kinds of woodfree paper. There were observed little differences in NOx emission for these four kinds of woodfree paper. Incineration ash emission for woodfree paper was almost caused by coal used in the process of the woodfree paper production and by waste paper burning in the incineration process.For more detailed study, it is desirable to analyze a life cycle inventory by taking the land use for wood afforestation or non-wood cultivation and the value of agricultural by-products into account.

Since the beginning of the eighties, anaerobic effluent treatment plants have been applied in the paper industry. The UASB reactor has become the most popular reactor. It is operating on almost all types of paper industry effluents, but the largest numbers can be found in the paper recycling industry.When acid paper sizing was abandoned, circumstances for fresh water reduction improved considerably. so that process waters and resulting effluents became more concentrated in COD.Besides this, anaerobic plants have also become popular for the treatment of condensates from sulphite (SP) and sulphate (Kraft) mills as well as for TMP and CTMP effluents and even for black liquor from soda pulping and NSSC. Improvements to the conventional UASB reactor have further increased loading rates and reduced hydraulic retention times. The IC (Internal Circulation) UASB reactor can treat twice the COD loading of conventional UASB at hydraulic retention times of 2 hours or more and is replacing the role of UASB in the paper industry effluents.

In 1998 nonwood plant fiber pulp formed about 11% of total pulp produced in the world. People's Republic of China was the top producing country of the pulp and produced a good part of paper and board from the pulp. USA was the third producing country and Japan was the third importing country of the pulp. To cope with the difficulties on the growing demand for paper and board, fast-growing plant resources such as eucalyptus and kenaf are being watched with keen interest in the paper industry. In this paper kenaf and eucalyptus were both shown to be eco-plants with citing most reliable reports from USA and Japan on the annual yields of these plants. As for eco-pulping, neutral sulfite method that had been already developed by the author et al. as the most suitable cooking method for abaca in 1953 was shown to be applicable to kenaf, rice straw, jute and even softwood with several reports. It was found that neutral sulfite and neutral sulfite anthraquinone method of cooking produce pulp of increased yield, high brightness, high strength properties and no ill-smell, enable the recovery of heat energy and chemicals in black liquor and furthermore make it possible to convert recovered chemicals into original cooking chemicals without using any compound such as calcium and others.

The bubbling fluidized bed reactor of iron oxide direct causticizing process, which constitutes a main part in the process, was developed. In this process, high-grade iron oxide, whose diameter is 0.2-1.0mm was used as causticizing agent as well as bed material. Concentrated black liquor was fed over the bubbling iron oxide bed by means of spray nozzle at the temperature of 1, 173-1, 273K.Reacted sodium ferrite was hydrolyzed to recover sodium hydroxide and residue iron oxide was recycled. During the reaction in the bed as well as hydrolysis, iron oxide particle was gradually attritted so that the operation of fluidized bed became difficult. Compacting pelletizing of as much as 50% in weight of pulverized iron oxide powder was found to be effective not only for preservation of fluidized bed but for sodium recovery through process simulation as well as 40 hrs' continuous operation of 500 mm sq.bench scale test.

Nippon Paper Industries Co.. Ltd. Iwakuni Mill started up the high temperature and pressure recovery boiler having a reaction furnace of KP black liquor of 2700 T D capacity as dry solid basis in 1997. This boiler is the largest recoveryboiler in the world generating high temperature and pressure steam (10.3 MPa. 505 °C).This paper presents operation experience and running data after commercial operations of high temperature and pressure recovery boiler.

Among the countries using nonwood plant fiber as pulp raw materials, China is a leading country to use straw, reed, bamboo and so on (76.1% on total pulp ca. 10 million tons in 1992). However, the use of rice straw is quite small, because of a large amounts of ash, especially silica. Silica causes the scale trouble during the concentration of soda black liquor. Therefore, in order to use more rice straw for pulp production, silica trouble must be solved as soon as possible. On this point, it is also important to find the pulping method leaving silica in pulp.This paper presents the results of studies on the ash properties of straw and the behavior of rice straw ash in black liquor. The results are summarized as follows:(1) Crystalline structure of straw silica is the mixture of crystoballite and quartz type. It is interesting that the generated silica from sodium silicate in black liquor shows a diffuse, broad X-ray spectrum.(2) The ash in black liquor is removed by the addition of precipitant, namely CaO or CaO+CaCl2. The efficiency of CaCl2 addition is observed at the lower amounts of CaO addition (200% on silica) and shorter precipitation time (60 min. at 80°C). The efficiency of CaCl2 addition is not observed at higher CaO addition (300% on silica). The amounts of CaO precipitant and precipitation time can be decreased by the concentration of black liquor.(3) In order to remove separately ash and lignin in black liquor, two stage pH adjustments of black liquor are efficient.

This paper introduces the reduction of oil consumption in KP mill analyzing energy balance. Enargy sources of pulp and paper mills in Japan are 66.3% of purchased energy and 33.7% of supplied energy by own mill, where the black liquor percentage is 96.4%. In case of kraft pulp and paper mills energy sources are 15.8% of purchased energy and 84.2% of black liquor.Analyzing energy balance, we could operate the KP mill using black liquor only, if we save the energy by 6.6%.Case studies of save the energy which we are trying now, shows as follows ;(1) Making higher black liquor consistency.(2) Much more usage of cheaper electric power during the night time.(3) Aiming higher boiler efficiency.(4) Saving steam and electricity of process stages.(5) Aiming high efficiency of power generation.

KAWASAKI KJ-16500 S type soda recovery boiler having a reaction furnace of KP black liquor of 2, 700 T/D capacity as dry solid basis, designated for Nippon Paper Industries Co., Ltd. Iwakuni mill is now under construction. This boiler is the largest soda recovery boiler in the world generating high pressure and high temperature steam (105 kg/cm2·505°C) and a monumental project of KHI's a hundred years anniversary. This paper presents KHI's design concept, the newset technology, capability and reliability of composite tube for the soda recovery boiler.

製紙工場における圧力容器や配管は1年あるいはそれ以上の周期で点検が行われている。定検毎に損傷が調査・記録され, 1年以上の操業が可能か検討される。最近, いくつかの工程において急激な腐食の進行が起きていることが明らかになった。この論文で腐食性が増加する理由について, 特に蒸解釜とエバポレーターの腐食の問題について述べる。重要な要素の一つに, 高品質の製品を製造するための新しいプロセスの開発があげられる。既存の設備は時として設計条件からはずれた条件下で操業が行われる。他の重要な要因として, 環境問題への関心の高まりから, 外部への影響を最小限にするために工程をクローズド化することがあげられる。工程のクローズド化は, 薬液組成に影響を与えるとともに, 工程内に有害な薬品を蓄積させる。重要なパラメーターは, 例えば温度, pH, 電位, そして流速である。腐食の増加に伴い, 耐食性材料の改善が必要となり, 新しいグレードの鋼材を使用することも別な要因として考えられる。腐食速度の増大と損傷の広がりは, バッチ式蒸解釜, 連続蒸解釜, 黒液エバポレーター, 配管, 薬液貯槽, そして漂白設備等あらゆる設備で観察される。この論文では, 薬液組成, 腐食の種類, および腐食の発生する鋼材/媒体との組合わせ等から, 腐食の発生について述べる。

Soda lignin from rice straw was sulfomethylated, and the dispersion ability of sulfomethylated lignin was compared with that of commercial softwood lignosulfonate. The results are summarized as follows : (1) Black liquor from soda cooking of rice straw was adjusted to pH 8.2 with aq. sulfurous acid. Same mole of formaldehyde as sodium sulfite formed in black liquor was added, and then dissolved lignin was directly sulfomethylated (SML I). Sulfomethylated black liquor was separated by gel filtration method (SML II : 0.18 S/C6-C3).(2) SML I shows the similar standard dispersion number (SDN), regardless of max. temperature of soda cooking and reaction time of sulfomethylation.SDN of sulfomethylated liquor including SWL I, however, is inferior to that of lignosulfonate. This may be due to the low content of sulfonic acid group and low purity of SML I. In order to utilize straw soda lignin as dispersant, it is necessary to isolate soda lignin from black liquor and to sulfomethylate the isolated soda lignin.(3) The setting time of mortar with SML II show the relatively similar results to that of commercial lignosulfonate. SML I, however, requires a long period of the setting time. The utilization of SML I as the dispersant is impractical in mortar manufacture.(4) The dispersion effect with SML II was compared by the use of various types of additives. Among seventeen additives tested here, citric acid, gluconic acid, glucuronic acid and K, H-glucarate show the excellent SDN. Very high SDN shown by K, H-glucarate is worth noting.

Gotaverken Energy AB in Sweden had developed the new black liquor recovery system, CHEMRECTM, which is based on black liquor gasification.The first commercial CHEMRETM kraft recovery booster plant, capacity 34 t·DS/h at Frovifors Bruk in Sweden was successfully started up in May 1991 and the continuous operation was initiated in August the same year.CHEMRECTM booster is one of the applications of the system and gives incremental recovery capacity expansion in mills where recovery boilers are undersized.In the paper, the development history of CHEMRECTM, the operating results at Frovifors are summarized and the new standard CHEMRECTM booster plant is introduced.

The No. 10 recovery boiler for Tomioka Mill was completed in May 1990 and KP plant No. 3 which was completed in August 1990.This boiler is a higher pressure, temperature, thermal efficiency and low pollutants emission recovery boiler of the largest class in Japan. 50% of the steam requirement in Tomioka Mill is produced by this boiler.At the first stage, the plugging that was characteristic of kraft recovery boilers occured in the supperheater and the evaporator. For the past two years, we have doing monthly burning tests of black liquor fuel.Now, with the experience of two years operation, we have improved the operation method of this recovery boiler. The following is the report of the No. 10 boilers operation.

On the process of chemigroundwood pulp manufacturing by neutral sodium sulfite, small part of black liquor, after cooking, has been usually recovered and great part has followed with cooked chips which are passed to fiberizing, screening in low consistency and washing processes. The majority of waste black liquor has been difficult to be recovered for its low concentration.Nowaday, many methods have been used…separating out black liquor from cooked chips by squeezing equipment, screw press etc. before fiberization…pressing out black liquor from fiberized chips by screw press and washing out dilute black liquor by vacuum drum washer to separate it from fiber…and so on.These methods above have many troubles which are low yield recovery of black lipuor if kept in high concentration, on the other hand low concentration with expensive recovery if kept in good washing.Recently the method of counter current washing chips through washing tower has been developed and gave high attention. Black liquor is recovered as relatively high yield and concentration by this method.At Futatsuka Mill, Tonami Paper Co., Ltd., chips are washed in global digester which is used for cooking, in counter currency to chips with two grades of black liquor in middle and low concentration and hot water on three stages by diffusion under pressure.We have succeeded to get black liquor in high concentration to be able to be mixed to kraft recovery process from chemigroundwood process and good washing.

Pilot plant test and its supplementary test have now been done as the last step of research and development of Direct Causticizing Technology to get the data for technological and economical estimation. The experiments are to be finished in March, 1987.This article deals with the characteristics of ferric oxide as the causticizing agent, which are- the particle size and pelletization, mixing with black liquor, makeup ratio, purity and the reactivity of ferric oxide, and their influence on the construction of chemicals recovery system by Direct Causticizing Technology. An example of its total process is illustrated.

As a member of the Research Association of Pulp and Paper Technology established in September, 1982, our group is engaged in improving the technology of high solids concentration of black liquor.Our studies are being carried out according to the following schedule.19831984 : Bench-scale experimemt (120 B.D. kg/hr) 1984 : Construction of pilot plant (417 B.D. kg/hr) 19851986 : Operation of pilot plantDisc Evaporator has been developed in order to obtain high concentration black liquor.By using Disc Evaporator, we have produced 8090% DS black liquor.Boiling point rise and viscosity of high solids black liquor are presented.The economic aspects are roughly considered, because the objective of bench-scale experiment is to identify possible means for concentrating black liquor to higher solids level.Pilot scale studies, in 1985, will define the economy and energy efficiency of Disc Evaporator.

Activated sludge treatment of diluted kraft black liquors (CODMn 2, 0002, 500ppm) prepared in laboratory from red pine (Pinus densiflora) and white birch (Betula platyphylla) was examined through a half liter batch process. The behavior of organic components in the black liquors were examined by fractionations and lignin isolation from both the treated and untreated black liquors. Results were as follows : (1) The removal of BOD5 was 9597%, while that of CODMn was 2630%. Absorbances at 280 nm and 400 nm increased slightly in avarage. The pH value after the activated sluge treatment increased from 7 to about 8.5.(2) The fractionation experiments indicated the removal of hydroxy acids which are the main contributors to BOD5 and other low molecular components which are difficult to be oxidized by KMnO4.(3) The isolated kraft lignin from treated black liquor showed an increase of molecular weight and a large increase of absorbance in both ultra violet and visible light regions through the activated sludge treatment. The absorbance increase of the whole treated black liquor, however, was not reflected by the large absorbance increase of isolated lignin, which indicates the existence of both color removing and color forming ability of activated sludge organisms.(4) Alum treatment of diluted black liquor is recommended to be performed prior to activated sluge treatment because of high alum dosage requirement and the color increase of lignin fraction.

Comparison of specific gravity, boiling point rise (BPR) and vaporization rate between high solids (70-90%) AP and KP black liquor of softwoods (Douglas fir from North America, Domestic red pine) and hardwoods (Eucalyptus from Tasmania, Domestic oak) were carried out. Specific gravity of black liquor is temperature and solids concentration dependent and it made very little difference except for that of Eucalyptus AP and KP.Boiling point rise of AP and KP black liquor of softwoods and hardwoods depends upon solids concentration and residual alkali content whether that is AP or KP black liquor of softwoods and hardwoods. AP black liquor of softwoods has higher residual alkali content and higher BPR than KP black liquor, which is caused by higher active alkali charge by a factor of about We found very little difference between AP black liquor of hardwoods and KP black liquor of softwoods & hardwoods. Vaporization rate of AP black liquor of softwoods and hardwoods is nearly equal to or a little lower than that of KP black liquor.

Research Association of Pulp and Paper Technology (RAPPT) consists of 18 pulp and paper making companies and 8 machinery companies was established in September, 1982 for the purpose of effective promotion of technical development of the pulp and paper industry in Japan.To develop the new energy saving method RAPPT researched Direct Causticizing Process, High Solid Concentration of Black Liquor Process, High Consistency Paper Making Process and High Efficiency Drying Process. Expected data were obtained after laboratory test and pilot plant test.

Soda quinone (AP) and kraft cooking were carried out using softwoods (Douglas fir from North America, domestic red pine) and hardwoods (Eucalyptus from Tasmania, domestic oak). Black Liquor obtained were concentrated to the extent of 70-90% solids concentration in the laboratory in order to compare with the various physical and chemical properties of AP and KP black liquor. This articls deals with the viscosity of high solids AP and KP black liquor measured by “Flow Tester”.AP black liquor has higher viscosity about 5-10 fold than KP black liquor at the same concentration and temperature. Viscosity of AP and KP black liquor of various softwoods and hardwoods is classified to three groups and viscosity of each groups differs by a factor of 5-10 times.To investigate the reason for the difference of viscosity of AP and KP black liquors, the influence of four factors was checked.(1) residual alkali (2) ash content as organic/inorganic ratio (3) molecular weight of lignin (4) lignin content in black liquor.Molecular weight and molecular weight distribution of lignin were not recognized as the cause for the difference of viscosity of AP and KP black liquor. Viscosity of softwoods black liquor is profoudly affected by the difference of residual alkali which is caused by the difference of alkali charge in the AP and KP cooking

Properties of white liquor in Direct Causticizing process by ferric oxide and behavior of inorganic impurities which were leached from iron ore and accumulated in white liquor were investigated.Iron ore was reused 20 times in Direct Causticizing reaction and residual inorganic impurities were measured. About 66% of Al2O3 and only 5% of SiO2 is leached at the first cycle. NaCl, Na2SO4, KCl and K2CO3 has very little influence on Direct Causticizing reaction between Fe2O3 and Na2CO3.

Small-scale pilot-plant experiments were conducted on the evaporation of decalcified sulfite spent liquor (I) in a long-tube vertical evaporator. The evaporator used had only one heating tube 2.54cm in ID and 3.5m in length (heating surface 0.28m2). The feed concentration was varied from 10 to 50% (by wt.). In all cases, the feed rate was 34±2l/h, the boiling point was 95±1.0°C., and the temperature drop was 10.0±1°C. Also, for purposes of comparison, kraft black liquor (II) was evaporated under similar conditions in the same evaporator.The over-all heat-transfer coefficients U (kcal/m2h°C) in the evaporation of I from given initial concentrations were as follows : (The initial and final concentrations in weight per cent are given in order in parentheses.) 2, 800 (10, 20%), 2, 600 (20, 30%), 2, 400 (27, 40%), 2, 100 (36, 50%), and 1, 700 (45, 60%). The boiling point rises were 2.7, 4.0 and 5.0°C., respectively, at concentrations of 40, 50 and 55%. The values of U in the evaporation of II under similar conditions were nearly equal to the corresponding values found in the experiments with I. The boiling point rises were 4.0, 6.4 and 8.0°C respectively, at concentration of 4.0, 50 and 55%.

Graft copolymerization of acrylamide onto unbeaten and beaten pulp (N. B. KP) were carried out by the ceric ion method. Using the grafted pulp of various degree of grafting, grafted pulp papers were prepared and following result were obtained. 1) The pulp papers could be manufactured from the hydrophilic acrylamide grafted pulp fiber by neither beating nor addition of binder. 2) The strength properties of papers made from unbeaten grafted pulp were obtained following results. Breaking length at first increased with increasing degree of grafting, reached maximum value at the degree of grafting about 50%, and then fell off again. The maxima in burst factor and tear factor were the degree of grafting about 30-50% and 20-30%, respectively, 3) The degree of grafting of beaten pulp tended to decrease with increasing degree of beating. 4) The relationship between the stregth of the various beaten grafted pulp papers and the degree of grafting were obtained following results. Breaking length and burst factor of papers showed maxima values, and tear factor diminished with increasing degree of grafting.

The treatment of industrial waste liquor has given rise to an important problem in chemical industry especially pulp and paper industry lately.The research has been carried out in order to put the recovering method of chemicals from SCP black liquor by pyrolysis to practical use.Experimental installation is a series of arrangements composing of a reactor, cyclones and a condenser. The reactor of 200mm in internal diameter and of 4.5m in length was used and it was heated by means of electric heating from the outside.The effect of temperature of reactor wall exerting on the yield and component of products and the sticking probability of scale to reactor wall was examined in this report.The results obtained were summerized as follows.1) The most desirable result is obtained at the reactor wall temperature of approximately 700°C2) The produced gases containing H2, CO2, CH4, H2S, CO, C2H4 have a calorific value of about 3000kcal/kg.3) In the solid residue, Na2CO3 is a major inorganic compouet and a certain quatity of Na2SO4 and carbon is contained, but only trace of Na2S and Na2SO3 is found.4) The sticking of scale to reactor wall is never at approximately 700°C.

This paper reports the combustion and smelt production of semichemical pulp spent liquors (solid matter content 54.9%) as using heavy oil of auxiliary fuel by spray method and the calorific value's estimation of mixture of spent liquor solids and lignin as auxiliary fuel. Semichemical pulp spent liquors were burnt well and smelts were produced and flowed out successfully. The principal components of smelts are Na2C03, Na2S and sulfidity of white liquor will become 2430%, if Na2CO3 in green liquors are caustisated. It was estimated that the calorific value of mixture is equal to, or more than kraft pulp black liquor solids.

Aiming at recovering sodium compounds from KP black liquor, separation of sodium and lignin has been made by means of electrodialysis of ion exchange membranes which have the characteristics of ion selectivity and concentrating capacity. The aparatus consists of 25 cells each of which being Cation exchange membrane - Spacer - Anion exchange membrane - Spacer, and platine-plated stainless electrodes were used. The separation was done at dilute section circulating the sample black liquor with batch process, and its total sodium decreased from initial concetration of 44.7g/l (as Na2O) to 5.6g/l (as Na2O) after the period of 8 hours, and it was found that the balance between the two alkali concentrations had migrated to the side of the concentrated black liquor. In addition, there are several experimental methods for accelerating the velocity of sodium removal from spent sulfate liquor.

In order to obtain a good pulp with suitable qualities for wrapping purpose, the bagasse should be sufficiently depithed before digestion and also the SiO2 in the black liquor be removed. The usual differences between bagasse pulp and wood pulp of the same freeness are as follows:-1. Extracts with 10% NaOH sol : greater2. Beating time : shorter3. Bursting resistance : higher4. tearing resistance : slightly lower5. Folding endurance : higher6. Opacity : lower

When mixture of concentrated kraft pulp black liquor (solid content about 50%) and sodium sulfide was heated for 3 hours at 300°C, crude dimethyl sulfide which is comparable to 3.45% of solid component was prepared.According to gas chromatographic analisis, the crude dimethyl sulfide contained, as impurities, methyl mercaptan, ethyl mercaptan and unknown substance. The crude dimethyl sulfide could not purify by only fractional distillation.The results are described in the Table 2 and Fig. 6.

Studies were made on the preparation of high purities of sodium sulfate and hydrogen sulfide.Material for testing was smelt (17.5% of Na2S ; 52.5% of Na2CO3 ; 3.12% of Na2S2O3 ; 14.7% of Na2SO4 ; 3.52% of Na2SO3 ;0.05% of Fe2O3 and Al2O3; 0.63% of SiO2, etc.) obtained from the combustion of a NSSC black liquor in a KP type recovery furnace. Several effective methods were found out, but Process D was the simplest of all.Process DThe smelt was dissolved by water to prepare an aqueous solution (a green liquor). The green liquor was treated with 6N-H2SO4 to prepare an acid solution while generating hydrogen sulfide (83.4% of H2S ; 13.6% of CO2

In this paper was described an experimental study of recovery method of lignin and NaOH from black liquor.Crude lignin was precipitated from black liquor by CO2 at pH 7.5 and centrifugated. The yield of the deposit was 43% of wood. The lignin content of the deposit, when purified 72% H2SO4 was found to be 45.2%. From the supernatant liquor which contains 7% Na2CO3, NaOH was recovered by CaO. The yield was 18.5% per Na2O of black liquor : Elementary analysis, infrared spectrum, DTA, and TGA-DTA-GC of the alkali lignin and of HCl process lignin did not show marked difference.

This paper describes species variation of pulping timbers in color and COD of spent liquors from neutral sulfite pulping in connection with water pollution problems. Thorough investigation were made with certain hardwood species like Shii (Castanopsis cuspidata), Shide (Carpinus sp..) and Kagonoki (Actinodaphne lanciforia), common in Japan and certain southern tropical wood species like Red lauan (Shorea sp.), White lauan (Pentacme sp.) and Kapur (Dryobalanops sp.).Spent liquor from the cooking of both individual species and species mixture were analysed in each stage of the pulping processes. The digested chips were separated from cooking liquors (black liquor) and washed with one liter of distilled water (washings). And they were refined on a laboratory defibrator in three steps (defibration liquors) and each spent liquor was subjected to the routine spent liquor analysis searching for the main features of pollution characteristics.As a summary of the tests carried out, it may be stated that the effect of the species variation of pulping timbers in color and volume of the black liquor is considerably of high value, but there are no great differences in COD. Especially, volume of the black liquor has been found to be highly proportional to the apparent specific gravity of timber species. The distribution of solid, total color and COD in each stage of the pulping processes differed among timber species, because of the diffence of the apparent specific gravity of wood species. In the case of Lauan species, for example, color and COD were chiefly originated from the washings and the first defibration liquor rather than black liquor.On all wood species used, the contribution of black liquor reaches at most 50% of total color and COD of over all spent liquors produced, and the recovery of black liquor and especially the first defibration liquor are very important for the treatment of water pollution problems. It should also be mentioned that color of spent liquors and the pulp yield increase, as the pH of black liquors of hardwood cooking increases. Southern tropical wood, however, dose not show this relationship. Under the constant pulp yield, variation of the maximum temperature of digestion dose not influence on color and COD of spent liquors. But bark removal has the effect of lower coloration and higher COD of spent liquors. In the case of cooking of species mixture, the volume, color and COD of black liquors are manifestly represented as the mean values of those obtained from the individual cooking of each species.

Condition necessary for oxidation of lignin by air have been studied. Variables considered : time of reaction, temperature, weight of air, isolation method of pure vanillin. Vanillin was identified as an important product of the reaction when carried out at high temperature.Studies were made on the use of crude alkali lignin from black liquor of soda pulp waste liquor as raw material for the production of vanillin. The results indicated that air oxidation was as amenable to crude alkali lignin as alkali nitrobenzene oxidation. Optimum conditions yield of vanillin was about 6.90% of lignin (in vanillin 2, 4-dinitrophenyl-hydrazone, 7.53%).Isolation method of pure vanillin depending upon condition by sublimation have been discovered, and yield of pure vanillin was 4.80% of lignin (purity 90.2%).