WO2002042551A1 - Method for alkaline batch cooking of fiber material - Google Patents
Method for alkaline batch cooking of fiber material Download PDFInfo
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- WO2002042551A1 WO2002042551A1 PCT/FI2001/001010 FI0101010W WO0242551A1 WO 2002042551 A1 WO2002042551 A1 WO 2002042551A1 FI 0101010 W FI0101010 W FI 0101010W WO 0242551 A1 WO0242551 A1 WO 0242551A1
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- WIPO (PCT)
- Prior art keywords
- cooking
- digester
- impregnation
- liquor
- chips
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C1/00—Pretreatment of the finely-divided materials before digesting
- D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/26—Multistage processes
Definitions
- the invention relates to the field of alkaline pulping.
- alkaline cooking processes and especially kraft cooking are dominant in the production of cellulose or chemical pulp because alkaline cooking provides pulp fibers which are stronger than those from any other commercial pulping process.
- the lignocellulosic material typically chopped into wood chips, is treated in either batch or continuous digesters.
- Chip dimensions are of major importance in this context. The longer, wider and especially the thicker the chips are, the longer is the transportation distance to the centers of the chips
- Pores inside fresh wood chips are also partly filled with liquid and partly with air.
- the ratio is, among others, determined by the moisture content or dry content of wood.
- the air should be removed from the chips before they can be fully impregnated by cooking liquor. This is usually done by pre-steaming the chips.
- Typical heat-up times and at pressure times are 60 to 150 minutes and 60 to 120 minutes, respectively. Typical sum of heat-up and at pressure times is about 150 minutes.
- Displacement batch pulping processes were developed in the 80's, originally for the sake of energy economy. Following a batch cook, the black liquor was recovered, divided into fractions according to temperature and chemical content, stored and introduced into a di- gester charged with fresh lignocellulosic material in order to transfer the heat of the completed cook to a subsequent cook.
- the total duration of the black liquor impregnation stage in batch displacement processes is typically below 30 min at temperatures below 100 °C. Heating is carried out by displacement with a black liquor having a higher temperature than the impregnation liquor. Following these initial stages, white liquor is introduced, and a main cooking stage follows. Typically, the total duration of the hot liquor fill stage, temperature adjustment and the cooking stage is in the range 95-120 min.
- the Kamyr type energy savings are achieved by pre-heating the chips with steam obtained from flashing the hot black liquor.
- chips are preheated and air is removed from the chips to facilitate later liquor impregnation.
- the chip impregnation zone typically involves 30-60 min or shorter chip retention at a temperature of 115-130 °C and a high pressure to enliance the pre-impregnation of the chips and the ion transportation into the chips. Since penetration rates increase with increased pressure, impregnation stages operate at pressures that greatly exceed the liquor saturation pressure at the specified temperature, i.e.
- a countercurrent zone typically referred to as the hi-heat zone
- a countercurrent zone usually follows for 2-4 hours at temperatures of 130-160 °C.
- Contemporary continuous cooking as e.g. ITC, EMCC and Lo-solids cooking retains the cooking temperature, typically 150-160°C, all through the countercurrent zone, i.e. enlarging the cooking zone to the counter-current zone.
- These modern digesters have thus a total cooking zone of about 240-360 minutes.
- washing filtrate is pumped into the bottom of the vessel.
- the vessel bottom is also a blow dilution and cooling zone.
- Discharge temperature is typically 85-90 °C .
- the continuous processes offer, compared to conventional batch digesters: more space efficiency, less installed power, lower volumes of inlet streams and outlet stream, steady- state operation vs. batch fill and discharge cycles, energy efficiency, lower environmental impact and a first stage of brownstock washing.
- Impregnation theoretically requires small chips, but modern continuous digesters are based on the principle of maintaining sufficient liquid circulation and a good displacement efficiency. This calls for chip properties that are in conflict with some of the basic requirements for ensuring uniform delignification. Thus, a large chip size must be used, which leads to inferior impregnation and further longer retention times in cooking and expensive technology. Thus, the pulp maker has been trapped by his own technology. It is stated, that the 30-60 min retention time at 115-130°C in impregnation zones of continuous mill digesters could never provide a completely uniform distribution of cooking chemical for all chips (mill chips) before the start of bulk delignification.
- a pulping process which comprises so-called "cold impregnation" as its main feature.
- a temperature of about 80-110 °C is specified, the time period being unlimited. However, an opti- mum of 2-3 hours is suggested. Pressure may be used in order to compress gas bubbles and cause sinking of the chips.
- the theory behind the cold impregnation stage is, that acid- generating processes within the chips shall be suppressed until the chips are filled with alkali sufficient to neutralize any acid released when reaction commences at higher temperatures, and the impregnation step is defined as resulting in "an alkali concentration suf- ficient to neutralize all acid produced".
- the proposed process preferably uses a conventional continuous digester like MCC, EMCC or Lo-solids digester.
- a conventional continuous digester like MCC, EMCC or Lo-solids digester.
- the retention times in the cooking stage are in the order of several hours, typically around 2-5 hours.
- the figures of the application show a residence time in the impregnation stage approximately of the same order as in the cooking stage.
- the proposed continuous processes have pulp strength advantages, the cooking stage still has a long retention time and low reaction temperature . This requires huge and expensive digesters designed for, from a technical point of view, high pressures and temperatures.
- Chip impregnation takes place at a pressure in excess of 10 bar, using cooking liquor. Subsequently, the chips are fed into a continuous digester having a steam zone where the chips are rapidly heated to 170-185 °C and thus cooked before entering a liquid zone where gradual cooling takes place prior to discharge.
- the paper teaches that the total cycle including impregnation is in the range of 30 to 45 minutes, mostly using impregnation temperatures of 130-150 °C.
- an improved, alkaline batch cooking process wherein the raw chip material is preheated and air purged, and impregnated with a liquor at a temperature no higher than the boiling point at atmospheric pressure of the impregnation liquor, at retention times of more than 60 minutes.
- Liquors including fresh cooking liquor are added to result in a concentration in the range from about 0.5 to 2.2 mol/1 as OH " ions; preferably said concentration is about 0.5 to 1.5 mol/1 as OH71 ions; more preferably said concentration is about 0.75 to 1.5 mol as OH71 ions.
- a liquid-to- wood ratio in the range of 3 to 10 m 3 /t odw (m 3 per ton oven dry wood) is to be maintained during the impregnation step; preferably said ratio is in the range of 3 to 6 m 3 /t odw.
- the impregnated material is subsequently transferred to a batch digester and heated to a temperature T2 of at least about 150 ° C, preferably in not more than 40 min (t 2 ), after which follows a cooking stage at a time t 3 with a maximum temperature T3 of no more than 185 °C, and a liquid-to wood ratio of at least 2.5 m 3 /t odw during a substantial part of the heating and cooking steps.
- the total of t 2 and t 3 shall not exceed 90 min.
- Fresh cooking liquor is added during the heating step, the cooking step or both. After the cooking step, the delignified material is cooled to a temperature where significant cooking reactions no longer occur.
- a temperature decrease to about 140 °C is sufficient to end the cooking step.
- the time ti for impregnation is above 120 min, and the temperature TI in the range from 70 °C to the boiling point at atmospheric pressure of the impregnation liquor.
- the total of t 2 and t is less than 80 min. More preferably, the total of t 2 and t 3 is less than 70 min. Even more preferably, the total of t 2 and t 3 is in the range 10-60 min.
- the liquid-to wood ratio during a substantial part of the heating and cooking steps is preferably at least 3 m /t odw; more preferably, it is at least 3.5 m It odw.
- batch digesters over 10 m 3 are used.
- the heating and cooking time total in minutes may be expressed in relation to the digester volume N in m as follows: t 2 +t 3 ⁇ (0.09 N + 63) min when V > 100 m 3 , t 2 +t ⁇ 70 min when N is between 10 and 100 m .
- t 2 +t 3 ⁇ (0.09 N + 43) min when N > 100 m 3
- the heating time of a batch reactor is heavily dependent on size.
- a batch reactor of industrially significant size cannot be considered as a whole with regard to temperature, but each region within the reactor should ideally have the same temperature history.
- the material at the bottom reaches hot liquor displacement temperature long before the material at the top, but is correspondingly cooled earlier.
- the various parts of the digesters experience the same temperatures during approximately the same periods, but at a given point of time, the temperature may be different in various regions of the batch reactor.
- the heating step during period t 2 is preferably carried out by means of liquid displacement, whereby the amount of heat delivered to each region of chips is essentially uniform throughout the digester.
- the cooking step during period t 3 is preferably carried out by liquor exchange as e.g. liquid circulation or displacement.
- the cooling step is preferably carried out by means of liquid displacement.
- the average dry-solid of the material entering the impregnation stage is preferably over 40 %; more preferably said dry-solid is over 45 %.
- impregnation takes place at low pressure, for the present purposes defined as up to 5 bar.
- low pressure equipment may be used, which saves investment costs.
- Use of pressure may be required to ensure sinking of the chips in the liquid phase. If high pres- sure equipment is installed, it may be utilized as expedient.
- industrial wood chips are used as raw material for the process according to the invention. These commonly have an average length above 10 mm, typically 15-35 mm, and an average thickness above 2 mm, typically 3-7 mm.
- a digesting system for carrying out the process of the invention.
- the digesting system comprises at least one impregnation vessel, batch digesters in fluid communication with the impregnation vessel; transfer lines between the impregnation vessel and the bottom of each digester for transporting the impregnated material to the digester; a separator, comprising a withdrawal space, disposed in connection with each digester for separating a transport liquid from the impregnated material; first return lines attached to each separator to conduct the transport liquid from the separator back to the transfer lines; second return lines connected to the first return lines and to the impregnation vessel for transferring a portion of the transport liquid to an inlet of the impregnation vessel; and a supply line connected to an inlet of the impregnation vessel.
- the volume N of the impregnation vessel is larger than 1. 5 times the volume of each digester, preferably larger than 3 times the volume of each digester; more preferably larger than 5 times the volume of each digester.
- the specific effective alkali concentrations, temperatures and times used in a process according to the invention are dependent on the type of wood and the purpose of the product.
- Hardwood cooking generally requires lower maximum cooking temperatures than softwood cooking.
- Pulp for unbleached products also normally require lower cooking temperatures than for bleached products.
- the impregnation time depends mainly on the type of chips and raw material. Material hard to impregnate, and consequently requiring longer times, may consist of long and thick chips, or have a large proportion of low-porosity ma- terial. The type of equipment and the space available are other factors.
- Figure 1 shows schematically the time-temperature profile of prior art conventional batch cooking
- Figure 2 shows schematically the time-temperature profile of prior art displacement batch cooking
- FIG 3 illustrates schematically the time-temperature profile of prior art continuous cooking of the Kamyr type
- Figure 4 illustrates schematically the time-temperature profile of an embodiment of the invention
- FIG. 5 is a schematic representation of the tank farm required combined with a flowchart showing an embodiment of the invention and the various liquor streams occurring during the production cycle
- Figure 6 is a representation corresponding to Figure 5 showing an alternative embodiment of the invention
- Figure 7 is a representation corresponding to Figure 5 showing a further alternative embodiment of the invention
- Figure 8 shows the brightness achieved versus consumption of active chlorine in pulps prepared using the conditions set forth in Table 1,
- Figure 9 shows the brightness as a function of viscosity of pulps prepared according to the examples in Table 1,
- Figure 10 shows the active chlorine consumption against bleached yields in the examples according to Table 1, and
- Figure 11 shows the reject percentage as a function of impregnation time in pulp cooked to two kappa numbers according to the invention.
- Figures 1 to 4 show the temperature profiles of prior art pulping methods compared to that of the present invention.
- region 1 of the curve represents the heat-up phase
- region 2 illustrates cooking at about the maximum temperature
- region 3 illustrates the discharge and cooling of the conventional batch digester.
- the duration of region 1 is 60 to 150 minutes, and that of region 2 60 to 120 minutes.
- the sum of region 1 and 2 is typically about 150 minutes.
- region 5 represents the impregnation phase
- region 6 the hot liquor fill phase, i.e. hot black liquor treatment and hot white liquor charge
- region 7 represents the temperature adjust- ment phase, usually carried out by circulating the digester content and heating
- region 8 illustrates the cooking phase at cooking temperature.
- Region 9 represents the displacement with cool wash liquid and region 10 represents the cold discharge.
- region 5 typically is typically about 30 minutes, but it can be 10 to 40 minutes depending on digester size, at a temperature below 100°C.
- Region 6 is typically about 30 minutes (can be 15 to 40 minutes depending on digester size).
- Regions 7 and 8 are typically 65 to 100 minutes. Thus, regions 6, 7 and 8 together typically represent 95 to 130 minutes.
- Region 9 is typically 45 minutes (can be 20 minutes to 60 minutes depending on, among other factors, digester size). The stages of regions 5-9 occur in the same batch equipment.
- region 11 represents the impregnation phase
- region 12 represents heating
- region 13 represents a cooking phase, which can occur in both concurrent and countercurrent modes.
- Region 14 represents displacement and cooling of the cooked material before discharge from the digester.
- Region 11 is typi- cally 30 to 60 minutes or shorter at a temperature of 115-130°C.
- Regions 12 and 13 are over 90 minutes, typically 240 to 360 minutes.
- FIG. 4 shows the advantageous temperature profile of the present invention.
- Region 20 represents the impregnation phase, which as can be seen is substantially extended relative to processes presently in use.
- Region 21 represents the heating-up phase.
- Region 22 repre- sents the short reaction time and region 23 the cooling of the cooked material before discharge from the digester. Between regions 20 and 21, feeding of the pre-impregnated material to the batch digester takes place.
- FIG. 5 is a schematic representation showing the various tanks used in an embodiment of the invention, and a flowchart of the process together with the liquor streams occurring and their relation to the tanks.
- Wood chips are pre-steamed (point 1) and charged into the im- pregnation vessel.
- the chips can preferably be pre-heated to a temperature of 95-110 C, the retention time at that temperature being preferably 5-40 min.
- the transfer method and equipment between the presteaming phase and the impregnation vessel depends on the counter-pressure in the impregnation stage.
- the residence time of the impregnation stage (point 2) is at least 60 minutes. It can be significantly longer, depending on the available size of equipment.
- impregnation times of more than about 24 h may be used for example when combining the impregnation stage with chip storage between the chipping unit and the cooking plant.
- the impregnation time rarely exceeds 120 hours in the same equipment.
- the impregnation equipment may be a down-flow vertical vessel or a horizontal conveyer type vessel with at least one inflow and at least one outflow point for the material, known to the person skilled in the art.
- Installed continuous digester vessels can be used e.g. when upgrading an existing plant.
- the impregnation device can be considered to be of the chip silo vessel type.
- Several vessels can be used in series or in parallel.
- the impregnation vessels are preferably dimensioned for a low pressure, i.e. pressure in the area from about atmospheric to 5 bar. Atmospheric conditions can be used. High-pressure equipment (over 5 bar design pressure) can be used when for example upgrading a plant to a method according to the invention.
- Liquor A is added to the stage.
- the liquor contains fresh alkali (point WLimp) and spent liquor from tank 4.
- the amount may be, for example, 30 per cent or more of the total fresh alkali to be added calculated as total titrable alkali (TTA) per charged unit of wood, but additional fresh alkali is invariably added in the cooking stage.
- Spent liquor (from tank 4) is added as needed, recycled from e.g.
- the effective alkali concentration of the added liquors is 0.5-2.2 mol OH " /l; preferably, in the range 0.5-1.5 mol OHJ1; more preferably, in the range 0.75-1.5 mol OHJ1.
- the impregnation liquor A is a mixture of fresh alkali and spent liquor.
- the fresh alkali and spent liquor can be added together at one addition point, or in sequences during the impregnation.
- Spent liquor can be added first, and then fresh alkali is added and some spent liquor withdrawn.
- Fresh alkali can also be added first and then spent liquor.
- Parts of spent liquor and fresh alkali can also be added first, and then fresh alkali is added together with some withdrawal of spent liquor.
- the fresh alkali used can be both caustisized liquor, normally referred to as white liquor, and uncaustisized liquor, normally referred to as green liquor, or also derivates of the above mentioned liquors, e.g. a mother liquor from crystallization of sodium carbonate from green liquor.
- the temperature of liquor A may require adjustment to hold the preferable temperature between 70 °C and its atmospheric boiling point.
- Impregnated material is transferred from the impregnation reactor to the batch digester via a transfer system (points 3 and 4), which may be one of various combinations of discharge systems in the outlet part of the impregnation vessel and feeding technology known to the person skilled in the art.
- the system is supplied with liquor Al as required e.g. for dilution.
- Transfer systems to be used are for example pumps, chamber feeders (e.g. of the high pressure (HP) feeder type), screws, scrapers and injectors etc., and combinations therof, known to the person skilled in the art.
- the digester is charged hydraulically by e.g. pumping from the bottom. Other methods, e.g. charging from the digester top after liquid separation, may also be used.
- Surplus liquor is removed at Al from for example the digester screen girdle, and is conducted to tank 4.
- hot black liquor B from tank 1 and hot white liquor C from tank 3 are charged in a hot liquor fill stage (point 5), initially displacing liquor A2 to tank 4 and then, as the temperature rises above boiling point, D to tank 2.
- the temperature is adjusted by means of circulation-based direct or indirect steam heating or direct steam heating of the digester (point 6.1).
- the effective alkali concentration of the cooking liquor can be 0.05- 0.7 mol OHJ1, preferably in the range 0.1-0.5 mol OHJ1.
- Cooking is completed, and the batch is cooled by displacing the cooking liquor with cooler liquor (point 7), e.g. wash filtrate E from tank 5, possibly containing also liquor from tank 4.
- Displaced liquor is divided according to temperature and chemical content into fractions BI and Dl, to tanks 1 and 2 respectively.
- the digester is discharged (point 8), preferably by pumping using additional filtrate F from tank 5 as re- quired.
- flow G filtrate from the wash plant, may be used to dilute the white liquor, which is conducted to tank 3 while being heated by black liquor from tank 2.
- Figure 6 is analogous to Figure 5, but no circulation heating is used in the digester, which consequently requires no heating circuit piping. Instead, the digester heating takes place using hot liquor displacement (point 5), whereby the temperatures of black liquor B and white liquor C are preferably adjusted by heat exchange before introduction into the digester. Liquors D and B displaced during the hot displacement stages are conducted to tanks 2 and 1, respectively, depending on temperature and/or chemical content. According to this embodiment of the present invention, also cooking is carried out by displacement (point 6).
- Figure 7 shows an embodiment where heating occurs by direct or indirect steam heating to the digester circulation or direct steam heating of the digester (point 6.1). Other differences are pressurized blow of the digester content at the end of cooking (point 8).
- Table 1 shows the results of, on the one hand, comparative cooking experiments (1-4) using various typical conditions for prior art continuous and batch cooking, and on the other hand experiments (5-11) using conditions according to the present invention.
- the chips were impregnated with white liquor (liquor (EA charge of 33.7 % NaOH calculated on wood, EA 122 g NaOH/1 and sulfidity 30 %) at a liquor-to-wood ratio of 4 m 3 per ton of dry wood at 90 °C, 60 minutes and atmospheric pressure. After impregnation of the chips, and removal of excess liquor, the impregnated chips were then subjected to steaming and the temperature of the chips was initially raised to 100 °C for 20 min and subsequently treated at 175 °C for a total of 36 min, including heating-time of 7 minutes. After cooking the digester content was cooled with water. After the cook the pulp was wet disintegrated and screened. Kappa number, yield, reject, brightness were determined on the cooked pulp.
- Example 4 show laboratory simulation data of a process simulated according to prior-art displacement batch cooking of industrial Eucalyptus.
- 4.5 kg eucalyptus chips (oven dry basis) were metered into a chip basket positioned in a 26-liter jacketed displacement digester with liquor circulation.
- the same chip raw material as shown in Example 3 were used.
- the chips were pre-steamed for 10 minutes at 100 °C.
- impregnation liquor fill at 80°C was conducted with an impregnation liquor containing 0.29 mol OH71 of EA.
- hot black liquor treatment oc- curred for 20 minutes with a HBL containing 0.205 mol OH71 of EA and a temperature of 148°C.
- Example 5 Production of eucalyptus kraft pulp in accordance with an embodiment of the present invention.
- Example 5 The experiment was carried out as disclosed in Example 5, but the impregnation time was 60 min and the cooking conditions were adjusted to give about the same kappa number as in Example 5.
- Example 6 The experiment was carried out as disclosed in Example 6, but the cooking conditions were adjusted to give a higher cooking kappa number.
- Example 8 The experiment was carried out as disclosed in Example 7, but the impregnation time was adjusted to 180 minutes and the cooking conditions were adjusted to give slightly higher kappa number than in Example 7.
- Example 9 The experiment was carried out as disclosed in Example 8, but the impregnation time was adjusted to 3 days and the cooking conditions were adjusted to give slightly higher kappa number compared to Example 8.
- Example 10 The experiment was carried out as disclosed in Example 6, but the impregnation pressure was adjusted to 10 bar and the cooking conditions were adjusted to give slightly higher kappa number compared to Example 6.
- Example 11 The experiment was carried out as disclosed in Example 8, but the impregnation pressure was adjusted to 10 bar and the cooking conditions were adjusted to give slightly lower kappa number compared to Example 8.
- Table 1 shows the cooking characteristics of Eucalyptus hardwood chips, unbleached pulp results and the subsequent oxygen delignification, ECF bleaching and PFI beating results. All oxygen delignifications, ECF bleachings, PFI beatings and tests were performed in the laboratory.
- the effect of impregnation time is shown in Figure 11.
- the reject percentage is shown as a function of impregnation time as pulp is cooked according to the invention to kappa numbers 20 and 25 using a total heat-up and cooking time of 25 min. It is seen, that a satisfactory level is reached when 1 hour impregnation residence time is used; a further half per cent decrease is achieved by extending impregnation with a further hour. The improvement due to extension to even three days is marginal. However, table 1 shows that the bleaching chemical consumption is significantly lower and bleached pulp viscosity is higher when using 3 days impregnation.
- the reject level depends on the impregnation time and kappa number target (see figure 10 showing reject levels of pulps at kappa numbers 20 and 25 and impregnation times of 0-3 days using a retention time of 25 minutes in heating and cooking)
- the reject level is independent on impregnation pressure in the range 0.5 bar to 10 bar for pre-steamed chips implementing that low-pressure impregnation equipment can be used in impregnation - higher unbleached screened yield
- Example 7 used more NaOH in oxygen delignification, but the additional cost for this is minor since oxidized white liquor from the recovery cycle, i.e. low-cost NaOH, is usually used in oxygen delignification. - considerable lower active chlorine chemical consumption in ECF bleaching by about 50-65 %
- the hot black liquor stage and hot white liquor stage displaced the IL.
- the amount of hot black liquor was 4.0 1 per kg o.d. wood and EA 0.45 mol/1.
- the conditions in the hot black liquor and hot white liquor stage were: Total time 30 min, temperature 5 °C below cooking temperature and pressure 7.0 bar. Then temperature adjustment and cooking by circulation 5 followed.
- the hot white liquor was also split charged, so that 70%> was charged at the hot black liquor fill and 30% after 15 min at cooking temperature. The cooking time was varied by having different cooking temperatures. At the target H-factor, displacement liquor was pumped into the digester cooling the pulp.
- the conditions in the final displacement were: Temperature 80°C, time 50 min and total amount of liquor 7.0 1/kg o.d. wood. After 0 the cook, the pulp was wet disintegrated and screened. Kappa number, yield, reject, brightness and viscosity were analyzed on the pulp.
- Example 14 Production of softwood kraft pulp by using displacement kraft batch technology according to an embodiment of the invention.
- a hot black liquor and hot white liquor fill stage followed immediately.
- the hot black liquor and hot white liquor displaced the spent impregnation liquor.
- the amount of hot black liquor was 4.2 1/kg o.d. wood and EA 0.45 mol OH " /l.
- the conditions in the hot black liquor and hot white liquor fill stage were: Total time 30 min, temperature 5 °C below maximum cooking temperature and pressure 7.0 bar. Then temperature adjustment and cooking by circulation followed. The total heating and cooking time was 70 min.
- At the target H-factor displacement liquor was pumped into the digester, cooling the pulp.
- the conditions in the final displacement were: Temperature 80°C, time 50 min and total amount of liquor 6.7 1/kg o.d. wood.
- the pulp was wet disintegrated and screened. Kappa number, yield, reject, brightness and viscosity were de- termined on the pulp.
- the heat-up and cooking time can be reduced by over 50 %> compared to a prior art process at the same kappa number and reject level (sum of coarse and fine reject).
- Decrease of total cycle time by at least 40 min, which for a reference installation with total cycle time of 220 min means a production increase of at least 18 %.
- a lower number of batch digesters or lower total batch digester volume can be used to reach a given production level.
- Examples 16 to 18 show that the same production can be made with a total batch digester volume of 2400 to 2800 m 3 using a lower number of digesters.
- the examples show, that the volume ratios between the individual batch digesters and the impregnation vessel are about 2 to 6.8.
- Impregnation retention time min 60 120 180 Impregnation vessel, m 700 1370 2050
- the present invention offers the following surprising benefits over a state-of-the-art cooking process: - A lower number of batch digesters can be used which also means less pressure vessels, piping, instruments etc. - A lower total batch digester volume can be used to reach a given production level.
- an impreg- nation vessel which according to the invention can be designed for much lower pressure and temperature conditions.
- the building requirements are much lower with a method according to the invention as the digester is preferably filled with chips hy- draulically from the bottom.
- the chip silo and capping valve above the batch digesters can also be eliminated.
- the ratio between the impregnation vessel digester volume is important in order to obtain sufficient pre-impregnation.
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Priority Applications (3)
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AU2002223715A AU2002223715A1 (en) | 2000-11-24 | 2001-11-21 | Method for alkaline batch cooking of fiber material |
EP01997587A EP1339913A1 (en) | 2000-11-24 | 2001-11-21 | Method for alkaline batch cooking of fiber material |
US10/432,656 US20040089431A1 (en) | 2000-11-24 | 2001-11-21 | Method for alkaline batch cooking of fiber material |
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FI20002586A FI20002586A (en) | 2000-11-24 | 2000-11-24 | Process for alkaline batching when cooking fiber material |
FI20002586 | 2000-11-24 |
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WO2002042551A1 true WO2002042551A1 (en) | 2002-05-30 |
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US (1) | US20040089431A1 (en) |
EP (1) | EP1339913A1 (en) |
AU (1) | AU2002223715A1 (en) |
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CA3079732A1 (en) * | 2017-10-17 | 2019-04-25 | Auburn University | Phenols as additives in kraft pulping |
US20230374730A1 (en) * | 2022-05-17 | 2023-11-23 | Bracell Bahia Specialty Cellulose SA | Apparatuses, methods and systems for yield increase in a kraft cooking plant |
CN115305738A (en) * | 2022-08-22 | 2022-11-08 | 华南理工大学 | LCP cleaning pulping method |
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US5183535B1 (en) * | 1990-02-09 | 1996-02-06 | Sunds Defibrator Rauma Oy | Process for preparing kraft pulp using black liquor pretreatment reaction |
US6248208B1 (en) * | 1995-06-02 | 2001-06-19 | Andritz-Ahlstrom Inc. | Pretreatment of chips before cooking |
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- 2000-11-24 FI FI20002586A patent/FI20002586A/en not_active IP Right Cessation
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2001
- 2001-11-21 US US10/432,656 patent/US20040089431A1/en not_active Abandoned
- 2001-11-21 WO PCT/FI2001/001010 patent/WO2002042551A1/en not_active Application Discontinuation
- 2001-11-21 EP EP01997587A patent/EP1339913A1/en not_active Withdrawn
- 2001-11-21 AU AU2002223715A patent/AU2002223715A1/en not_active Abandoned
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US3215588A (en) * | 1963-08-15 | 1965-11-02 | Lummus Co | Continuous impregnation, cooking, and washing of fibrous material |
US3664918A (en) * | 1969-12-09 | 1972-05-23 | Pulp Paper Res Inst | Vapor phase pulping of water saturated lignocellulosic materials |
US4190490A (en) * | 1974-04-03 | 1980-02-26 | Domtar Inc. | Impregnation and digestion of wood chips |
WO1991012368A1 (en) * | 1990-02-09 | 1991-08-22 | Sunds Defibrator Rauma Oy | Process for preparing kraft pulp |
US5635026A (en) * | 1995-11-13 | 1997-06-03 | Ahlstrom Machinery Inc. | Cooking cellulose material with high alkali concentrations and/or high pH |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011138634A1 (en) * | 2010-05-04 | 2011-11-10 | Bahia Specialty Cellulose Sa | Method and system for high alpha dissolving pulp production |
AU2010202496B2 (en) * | 2010-05-04 | 2015-04-16 | Bahia Specialty Cellulose Sa | Method and system for high alpha dissolving pulp production |
US8535480B2 (en) | 2010-05-06 | 2013-09-17 | Bahia Specialty Cellulose Sa | Method and system for pulp processing using cold caustic extraction with alkaline filtrate reuse |
US8734612B2 (en) | 2010-05-06 | 2014-05-27 | Bahia Specialty Cellulose | Method and system for high alpha dissolving pulp production |
WO2012006396A1 (en) * | 2010-07-07 | 2012-01-12 | Andritz Inc. | Chip feed and steaming system and method for batch digester |
CN103352385A (en) * | 2013-06-28 | 2013-10-16 | 汶瑞机械(山东)有限公司 | Energy-saving and environment-friendly displacement cooking process for wood and bamboo raw materials |
Also Published As
Publication number | Publication date |
---|---|
US20040089431A1 (en) | 2004-05-13 |
EP1339913A1 (en) | 2003-09-03 |
FI20002586A0 (en) | 2000-11-24 |
FI20002586A (en) | 2002-05-25 |
AU2002223715A1 (en) | 2002-06-03 |
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