• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    ABSTRACTThe present invention relates to a method for production of a paper productcomprising the following step:a) providing a chemical pulpb) adding Iignosulfonate to the chemical pulp such that a chemical pulpcomprising Iignosulfonate is obtainedc) beating the chemical pulp comprising Iignosulfonate obtained in step b)such that a beated chemical pulp is obtained, andd) producing a paper product from the beated chemical pulp obtained instep c) 13
    公开号:SE1151226A1
    申请号:SE1151226
    申请日:2011-12-20
    公开日:2013-06-21
    发明作者:Francois Lambert
    申请人:Domsjoe Fabriker Ab；
    IPC主号:
    专利说明:

    METHOD OF INCREASING THE EFFICIENCY OF A BEATING OF ACHEMICAL PULP Technical fieldThe present invention relates to the field of paper making, in particular it relates to anenergy efficient method of beating a chemical pulp.
    BackgroundWood is composed of cellulose, hemicellulose, lignin and extractives and is the most common raw material in papermaking. Typically, a paper making process includesdebarking and chipping of logs followed by a chemical or mechanical pulpingprocess. Chemical pulping can be an acidic process, such as the sulfite process oran alkaline process, such as the sulfate process (Kraft process). ln the Kraft process,wood chips are cooked in a mix of sodium hydroxide and sodium sulfide. Prior tocooking, the chips are normally first wetted and preheated with steam. This step isfollowed by a step of impregnation of the chips with black and white liquor,comprising sodium hydroxide and sodium sulfide. The chips are thereafter cooked ina digester for several hours, at a temperature between 130 °C to 180 °C, and duringthis process lignin and some hemicellulose is degraded and dissolved in the cookingliquid. The remaining cellulose fibers are blown or squeezed from the outlet of thedigester through an airlock. The swift change in pressure results in a suddenexpansion of the fibers, which leads to a further separation of the fibers. The resultingfiber suspension in water solution is called "brown stock" due to its brown color. Thebrown stock is thereafter washed in a series of brown stock washers, in order toremove degraded lignin and hemicellulose, as well as other contaminates such asspent cooking chemicals. The extracted liquid is called black liquor. Sodium andsulfur compounds from the black liquor is recovered and recycled in the process andthe remains are burned to produce energy. ln the sulfite process the extracted liquidis called red liquor, brown liquor or spent sulfite liquor. Lignosulfonate is a valuableproduct which can be recovered from the spent sulfite liquor. After the brown stockwashing steps a clean pulp is obtained and depending of the intended use of thepaper, the clean pulp can optionally be bleached. The pulp is next put through amechanical rubbing action called beating, which increases the bonding ability of thefibers so that most of the strength properties of the produced paper will be improved.
    Different fillers and other additives is thereafter added to the beated pulp to producea furnish. The additives can for example improve different characteristics of the paperand the filler can be added to reduce the amount of fibers in the paper which willreduce the costs. The furnish is finally fed or pumped into a paper machine. Thepaper machine typically consists of forming, press and dryer section. ln the formingsection the furnish is dewatered to form a paper web. After the forming section theweb enters the press section, the dewatering continues by pressing the web underload. Finally the paper is dried in the dryer section, using steam Summary of the present disclosure Cellulose fibers present in a chemical pulp, such as a sulfate pulp or a sulfite pulp aretypically straight, smooth, rounded and largely undamaged. These characteristicsmake the bonding between the fibers fairly weak. To be able to produce paper withhigh strength the contact area and thus the strength of the bonds between the fibersneed to be increased. This is achieved by a process known as beating wherein thepulp is subjected to a mechanical rubbing action which flattens the fibers andunravels microfibrils. Thereby the surface area and the hydrogen bonding potentialbetween fibers are greatly increased. lncreased beating of pulp therefore generallyincreases the strength of the pulp as well as the strength of a paper productgenerated from said pulp. However, the beating of the pulp is a highly energydemanding step and there is thus a need for improved energy efficient methods formaking paper from a chemical pulp. ln particular there is a need for improved energyefficient methods for beating of chemical pulps.
    The present inventors have discovered that the energy required for beating a pulp,such that the strength of the pulp reaches a certain value, can be vastly reduced iflignosulfonate is present in the beater during the beating process. Therefore theenergy needed for producing a paper product can be vastly reduced if lignosulfonateis added to the process such that the lingosulfonate is present in the beater.
    Thus a first aspect of the invention relates to a method for production of a paperproduct comprising the following step:a) providing a chemical pulpb) adding lignosulfonate to the chemical pulp such that a chemical pulpcomprising lignosulfonate is obtainedc) beating the chemical pulp comprising lignosulfonate obtained in step b)such that a beated chemical pulp is obtained, and d) producing a paper product from the beated chemical pulp obtained instep c) A second aspect of the invention re|ates to a method of increasing the efficiency of abeating of a chemical pulp in an industrial process for production of a paper productcomprising the following steps:a) providing a chemical pulpb) adding lignosulfonate to the chemical pulp such that a chemical pulpcomprising lignosulfonate is obtainedc) beating the chemical pulp comprising lignosulfonate obtained in step b)such that a beated chemical pulp is obtained, andd) optionally producing a paper product from the beated chemical pulpobtained in step c) A third aspect of the invention re|ates to use of lignosulfonate for increasing theefficiency of a beating of a chemical pulp in an industrial process for production of apaper product.
    Brief description of the fiqures Figure 1a shows the energy needed for beating of a pulp to a tensile strength of 100Nm/g in the presence of 1 % lignosulfonate, 0.3 % lignosulfonate or in the absenceof lignosulfonate (ref). The y-axis shows the beating energy in kWh/ton.
    Figure 1 b shows the beating degree of a pulp beated to a tensile strength of 100Nm/g in the presence of 1 % lignosulfonate, 0.3 % lignosulfonate or in the absenceof lignosulfonate (ref). The y-axis shows the beating degree in degree Schopper-Riegler (°SR).
    Figure 2 a shows the tensile strength of a pulp beated with a beating energy of 100kWh/t in the presence of 1 % lignosulfonate, 0.3 % lignosulfonate or in the absenceof lignosulfonate (ref). The y-axis shows the tensile strength in Nm/s.
    Figure 2 b shows the compression strength of a pulp beated with a beating energy of100 kWh/t in the presence of 1 % lignosulfonate, 0.3 % lignosulfonate or in theabsence of lignosulfonate (ref). The y-axis shows the compression strength in Nm/s.
    Figure 3 shows the fiber length of the pulps after beating with different beatingenergy in the presence of 1 % Iignosulfonate, 0.3 % Iignosulfonate or in the absenceof Iignosulfonate (ref). The x-axis shows the beating energy in kWh/ton and the y-axisshows the fiber length in mm.
    Detailed descriptionThe present invention is based on the discovery that the energy required for the beating of a chemical pulp, such that the strength of the chemical pulp reaches acertain value, can be vastly reduced if Iignosulfonate is present in the beater duringthe beating process. Therefore the energy needed for producing a paper product canbe reduced if Iignosulfonate is added to the process such that the Iignosulfonate ispresent in the beater. Accordingly, a first aspect of the invention relates to a methodfor production of a paper product comprising the following step:a) providing a chemical pulpb) adding Iignosulfonate to the chemical pulp such that a chemical pulpcomprising Iignosulfonate is obtainedc) beating the chemical pulp comprising Iignosulfonate obtained in step b)such that a beated chemical pulp is obtained, andd) producing a paper product from the beated chemical pulp obtained instep c) ln a second aspect the invention relates to a method of increasing the efficiency of abeating of a chemical pulp in an industrial process for production of a paper productcomprising the following steps:a) providing a chemical pulpb) adding Iignosulfonate to the chemical pulp such that a chemical pulpcomprising Iignosulfonate is obtainedc) beating the chemical pulp comprising Iignosulfonate obtained in step b)such that a beated chemical pulp is obtained, andd) optionally producing a paper product from the beated chemical pulpobtained in step c) Exemplary embodiments of the first and second aspect are further described below.ln the art, mechanical pounding and squeezing processes of cellulosic fibers in apulp can some times be described as beating of a pulp and some times as refining ofa pulp. The term beating in the present disclosure covers all these different kinds ofmechanical pounding and squeezing processes of pulps. ln the present disclosure, the expression “increasing the efficiency of a beating of a chemical pulp” means thatless energy is needed in the beating step to produce a chemical pulp of a certainstrength. The strength of the pulp can for example be measured as a tensile strengthor a compression strength. ln the present disclosure the expression “industrialprocess” means that the process in not a laboratory experiment but that a significantand industrially relevant amount of pulp is beated in the beating step, such as forexample more than 500 kg/h such more than 1 ton/h.
    The present inventors have demonstrated that the addition of lignosulfonate to thebeating step can decreases the energy consumed in the beating of a sulfate pulpwith as much as 50 %. Accordingly, in one embodiment the addition of lignosulfonateadded in step b) decreases the energy consumed in step c) with at least 10% suchas at least 20% such as at least 35 % such as with about 50 %. lt is surprising thataddition of lignosulfonate can decreases the energy consumed in the beating with asmuch as 50 %, especially in the light of previous experiment where the effect oflignosulfonate as a beater additive in a beating of commercial hardwood unbleachedKraft pulp has been investigated in laboratory experiment. The conclusion of theseexperiments was that lignosulfonate need to be chemically modified by desulfonationand amination to accelerate the beating. Unfractionated unmodified lignosulfonatedid not show any positive effect of the beating at all, and a low molecular fraction ofthe lignosulfonate even had a negative effect on the beating (Levon et al. 1986). ltshould be mentioned that Levon et al. did not measure the actual strength of thepulp, such as the tensile strength or the compression strength. lnstead theacceleration effect on beating was measured as CSF (Canadian Standard Freeness).CSF which is a measure of the beating degree. lt should be mentioned that CSF isnot a direct measure concerning the strength properties of pulp but was consideredas an adequate estimation by Levon et al. lt should also be mentioned that thepresent inventor demonstrated that addition of lignosulfonate to the beating stepincreased the strength of the pulp at a lower beating degree.
    The strength of a pulp is an important feature since the strength of the pulp correlateswith quality parameters of the paper products produced from the pulp. For example,increased pulp strength generally leads to increased paper strength. Furthermore, ifthe strength of the pulp is high it is possible to use less fiber (i.e. pulp) and morefillers (e.g. clay and calcium carbonate) to obtain a paper product of a certain quality.Since the cost of the pulp is higher than the cost of the fillers, the total cost of thepaper product can be reduced. As mentioned above, the present inventors have alsodemonstrated that the beating degree is lower in a pulp beated in the presence of lignosulfonate compared to a pulp beated to the same strength in the absence oflignosulfonate. A lower beating degree makes it easier to dewater and/or dry the pulpwhich further saves energy in the process of production of a paper product. Sincedewatering of a pulp can be a limiting step of the paper production, the loweredbeating degree, mediated by beating in the presence of lignosulfonate, can increasethe production capacity of a paper mi|. Therefore, in one embodiment the methodaccording to the present invention can be a method for decreasing the energyneeded for dewatering and/or drying of a beated chemical pulp. ln anotherembodiment the method according to the present invention can be a method ofincreasing the production capacity of a paper mi|.
    The method according to the present invention is suitable both for high concentration(HC) beating and for low concentration beating (LC). HC beating is typicallyperformed at a pulp concentration of about 25-30 % (w/w) and LC beating is typicallyperformed at a pulp concentration of about 2-4% (w/w). LC-beating is very efficientfor increasing the strength of the pulp and of the finished paper product and thus in apreferred embodiment the beating in step c) is a LC beating. Accordingly, in oneembodiment the concentration of the pulp in step c) is between 1 and 5 % (w/w),such as between 2 and 4 % (w/w). ln an alternative embodiment the beating in stepc) is a HC beating and in one embodiment the concentration of the pulp in step c) isbetween 20 and 35 % (w/w), such as between 25 and 30 % (w/w).
    As discussed above, the present inventors have demonstrated that the addition oflignosulfonate to the beating step can decreases the energy consumed in the beatingof a sulfate pulp with as much as 50 %. Since the physical properties of the fibers indifferent types of chemical pulps are quite similar the method according to thepresent invention is suitable for any kind of chemical pulp. However, particularlysuitable pulps according to the present invention are sulfate pulps and sulfite pulps.Therefore, in one embodiment the chemical pulp is a sulfate pulp or a sulfite pulp andin a preferred embodiment the chemical pulp is a sulfate pulp.
    A particularly suitable lignosulfonate according to the present invention is a soft woodlignosulfonate prepared from spent sulfite liquor obtained in a sulfite pulping process.The present inventors have demonstrated that addition of such a lignosulfonate tothe beating process can decrease the energy consumed in the beating with as muchas 50 %, without any need for a fractionation or chemical modification of thelignosulfonate. Thus, in one embodiment the lignosulfonate is a soft woodlignosulfonate and in a preferred embodiment the lignosulfonate added in step b) has been prepared from spent sulfite Iiquor obtained in a sulfite pulping process. ln oneembodiment at least part of the lignosulfonate is added to step b) without anyfractionation of the lignosulfonate and in another embodiment at least part of thelignosulfonate is added to step b) without any chemical modification of thelignosulfonate molecules. However it is possible that the energy efficiency of thebeating process can be even further improved if the lignosulfonate is of a certainmolecular weight. For example it is possible that a high molecular weight faction insome cases can decrease the energy consumed in the beating more than if forexample a non-fractionated lignosulfonate is added. Such high molecular fractions oflignosulfonate can for example be obtained by filtering the lignosulfonate through a20 kDa membrane cut-off filter or a 30 kDa membrane cut-off filter, or through a 40kDa membrane cut-off filter, or through a 50 kDa membrane cut-off filter. ln mostcases this is however less preferred given the good results of an unfractionatedlignosulfonate and given the costs associated with fractionation of the lignosulfonate.The average molecular weight of an unfractionated lignosulfonate prepared fromspent sulfite Iiquor is typically in the range 1-100 kDa. Thus ln one embodiment theaverage molecular weight of the lignosulfonate is 1-100 kDa, such as 5-75 kDa, suchas 10-60 KDa. lt is also possible that introduction of chemical modifications in thelignosulfonate can increase the efficiency of the lignosulfonate as a beater additivebut this is also less preferred considering the good results of an unmodifiedlignosulfonate and considering the costs generally associated with introduction ofchemical modifications.
    Lignosulfonate is a valuable product which can be recovered from the spent sulfiteIiquor. Typically isolation of lignosulfonate from spent sulfite Iiquor involves the stepof removing water from the spent sulfite Iiquor by evaporation. Thereby thick spentIiquor having a dry matter content of about 60-70 % can be obtained. ln the industry,this lignosulfonate fraction can be used directly either as fuel in a sulfite pulpingprocess or it can be sold as a valuable product. Alternatively the lignosulfonate canfurther be spray dried to obtain a dry lignosulfonate product. The present inventorshave realized that it is beneficial if the lignosulfonate is added to the beating step in aliquid form since this will facilitate mixing of the lignosulfonate with the pulp. This willin turn further increase the efficiency of the beating. Therefore, in one embodimentthe lignosulfonate added in step b) is thick spent Iiquor which has been obtained byelimination of at least part of the water present in the spent sulfite Iiquor. ln anotherembodiment the elimination of at least part of the water present in the spent sulfiteIiquor has been achieved through evaporation. ln a preferred embodiment the dry matter content of the lignosulfonate added in step b) is in a range 20-60 %, such as30-50 %.
    The present inventors have further rea|ized that in some cases high levels of sugarsor sugar acids in the lignosulfonate might have a negative effect on the beating.Sugars can be removed from the lignosulfonate by subjecting the spent su|fite Iiquorto fermentation. Therefore, in one embodiment the method further comprises a stepof fermenting the spent su|fite Iiquor to decrease the amount of sugars in thelignosulfonate. ln one embodiment the amount of sugars and/or sugar acids in thelignosulfonate added in step b) is below 10% such as below 5%. ln one embodimentthe amounts of sugar acids introduced to the chemical pulp during step a), b) and/orc) is less than 90 g/ ton beaten pulp.
    The most common lignosulfonates obtainable from a su|fite process is sodiumlignosulfonate, magnesium lignosulfonate ammonium lignosulfonate and/or calciumlignosulfonate. For economical reasons it is preferred to use any of theselignosulfonates. Thus, in one embodiment the lignosulfonate is selected from sodiumlignosulfonate, magnesium lignosulfonate, ammonium lignosulfonate and/or calciumlignosulfonate. ln a preferred embodiment the lignosulfonate is sodiumlignosulfonate.
    The present inventors have demonstrated that addition of 1% lignosulfonate to abeating process of a chemical pulp can decrease the energy consumed in thebeating step with about 50 %. However the effect of addition of lignosulfonate isevident at much lower concentrations. Since lignosulfonate is a colored polymer, itcan some times be preferred to add lower amounts of lignosulfonate to the pulp. Forexample if a high amount of lignosulfonate is added in a process of producing whitepaper, more bleach chemicals will be needed. However in most cases it is preferredthat the concentration of lignosulfonate is above 005% (w/w). Thus in oneembodiment the concentration of lignosulfonate in step c) is at least 0.05 % (w/w)such as at least 0.1 % (w/w), such as at least 0.3 % (w/w). ln one embodiment theconcentration of lignosulfonate is between 0.05 to 5 % (w/w), such as 0.1 to 3 %(w/w), such as 0.3 % to 1 % (w/w). For clarity reasons it should be pointed out thatthe concentration of lignosulfonate mentioned in the present disclosure is in relationto the amount of pulp. For example the expression “addition of 1% (w/w)lignosulfonate” in the present disclosure means that 10 kg lignosulfonate is added to1 ton of pulp. ln the beating step the concentration of pulp is usually about 2 to 4 %.This means that if the concentration of lignosulfonate is 1% (w/w) in relation to the amount of pulp, and the beating process is performed at a pulp concentration of 4 %,the actual concentration of lignosulfonate in the beating step is 0.04 %.
    The Iignosulfonate can be added to the process at any step upstream of the beatersprovided that the Iignosulfonate will not be removed from the process by for examplea washing step prior to the beating. Therefore, in one embodiment, at least part ofthe Iignosulfonate is added to a clean pulp in a step prior to the beating step but aftera brown stock washing step. However, it is preferred that the Iignosulfonate is addedin a step close to the beating, for example directly to the beater. Addition ofIignosulfonate directly to the beater facilitates a good mixing of the lignosulfonate withthe pulp which further increases the efficiency of the beating. Therefore, in oneembodiment at least part of the Iignosulfonate is added directly to the beater in a pulpand/or paper mill. Typically about 10 ton pulp / hour is beated in an industrial beatingprocess in a pulp and/or paper mill. ln one embodiment at least 100 kg pulp such asat least 1 ton pulp, such as at least 10 ton pulp is beated in step c). ln oneembodiment at least 100 kg pulp/hour such as at least 1 ton/ hour such as at least 10ton/hour is beated in step c). The beating step can be performed in any pulp-beateror pulp-refiner known to the skilled person. Examples of such beaters and refinersinclude disc refiners and cone refiners. Thus, in one embodiment the beating in stepc) is performed in a disc refiner and/or cone refiner and in one embodiment theIignosulfonate is added directly to a disc refiner and/or a cone refiner.
    A third aspect of the invention relates to use of Iignosulfonate for increasing theefficiency of a beating of a chemical pulp in an industrial process for production of apaper product. The embodiments of the first and second aspect apply to the thirdaspect mutatis mutandis ExamplesA sulfate pulp from a paper mill having a kappa value of 52 and was beated in an Escher-Wyss cone refiner in the presence of 1 % or 0.3 % Iignosulfonate or in theabsence of Iignosulfonate. The Iignosulfonate was an unfractionated soft woodIignosulfonate prepared from spent sulfite liquor obtained in a sulfite pulping process(Domsjö fabriker AB, Sweden). The beated pulps were shaped in to sheets having asurface weight of 150g/m2. The pulp sheets were analyzed for tensile strength andcompression strength. The fiber length and the beating degree were also analyzed.
    Example 1 The pulps were beated as described above to a tensile strength of 100 Nm/g. As canbe seen in figure 1a, the energy needed for beating a pulp to a tensile strength of 100Nm/g was reduced with about 50 % by addition of 1 % lignosulfonate (w/w) and withabout 20 % by addition of 0.3 % (w/w) lignosulfonate to the pulp. The beating degreewas also decrease in the pulps beated in the presence of lignosulfonate, see figure1b. A low beating degree is desired since this can save energy in the precedingdewatering and drying steps.
    Example 2 The pulps were beated as described above with a beating energy of 100 kWh/t.
    As can be seen in figure 2a and 2b, addition of 0.3 % or 1 % (w/w) lignosulfonate tothe beating step increases the tensile strength (figure 2a) and compression strength(figure 2b) of the beated pulp.
    Example 3 The pulps were beated as described above and the fiber lengths of the pulps afterbeating with different beating energy were analyzed. As can be seen in figure 3, thefiber length is apparently unaffected by addition of lignosulfonate.
    REFERENCESLevon et al. “Acceleration of the beating of pulp by the use of modified Iignosulfonate”Mokuzai Gakkaishi (1986), 32(12), 1011-16
    权利要求:
    Claims (10)
    [1] 1. Method for production of a paper product comprising the following step: a) providing a chemical pulp b) adding lignosulfonate to the chemical pulp such that a chemical pulpcomprising lignosulfonate is obtainedbeating the chemical pulp comprising lignosulfonate obtained in step b)such that a beated chemical pulp is obtained, andproducing a paper product from the beated chemical pulp obtained instep c) C) d) Method of increasing the efficiency of a beating of a chemical pulp in an industrial process for production of a paper product comprising the following steps:a)b) providing a chemical pulp adding lignosulfonate to the chemical pulp such that a chemical pulpcomprising lignosulfonate is obtained beating the chemical pulp comprising lignosulfonate obtained in step b)such that a beated chemical pulp is obtained, and optionally producing a paper product from the beated chemical pulpobtained in step c) C) d) Method according to any of the previous claims wherein the addition oflignosulfonate added in step b) decreases the energy consumed in step c) withat least 10% such as at least 20% such as with about 50% Method according to any of the previous claims wherein the chemical pulp is asulfate pulp or a sulfite pulp Method according to claim 4 wherein the chemical pulp is a sulfate pulp Method according to any of the previous claims wherein the lignosulfonate is asoft wood lignosulfonate Method according to any of the previous claims wherein the lignosulfonateadded in step b) has been prepared from a spent sulfite liquor obtained in asulfite pulping process Method according to any of the previous claims wherein at least part of thelignosulfonate is added to step b) without any fractionation of thelignosulfonate. Method according to any of the previous claims wherein at least part of the lignosulfonate is added to step b) without any chemical modification of thelignosulfonate molecules 11 10) Method according to any of the previous claims wherein the dry matter contentof the lignosulfonate added in step b) is in a range 20-60%, such as 30-50% 11) Method according to claim 7 further comprising a step of fermenting the spentsu|fite Iiquor to decrease the amount of sugars in the lignosulfonate 12) Method according to any of the previous claims wherein the amount of sugarsand/or sugar acids in the lignosulfonate added in step b) is below 10% such asbelow 5% 13) Method according to any of the previous claims wherein the concentration oflignosulfonate in step c) is at least 0.05 % (w/w) such as at least 0.1 % (w/w),such as at least 0.3 % (w/w) 14) Method according to any of the previous claims wherein at least part of the Iignosulfonate is added directly to the beater in a in a pulp and/or paper mill. 15) Use of Iignosulfonate according to any of the previous claims for increasingthe efficiency ofa beating ofa chemical pulp in an industrial process forproduction of a paper product 12
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    同族专利:
    公开号 | 公开日
    WO2013095266A1|2013-06-27|
    SE536595C2|2014-03-18|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US2849314A|1953-03-02|1958-08-26|Permanente Cement Company|Process of treatment and products from waste sulfite liquors|
    US3079353A|1957-03-04|1963-02-26|Gossol Inc|Lignosulfonate derivative|
    SE446888B|1979-08-23|1986-10-13|Alby Klorat Ab|Method for producing lignocellulose material with improved strength, drainage ability, and malleability|
    JPH04119187A|1990-08-31|1992-04-20|Matsushita Electric Works Ltd|Beating method for pulp|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1151226A|SE536595C2|2011-12-20|2011-12-20|Method for increasing the efficiency of grinding a chemical pulp|SE1151226A| SE536595C2|2011-12-20|2011-12-20|Method for increasing the efficiency of grinding a chemical pulp|
    PCT/SE2012/051387| WO2013095266A1|2011-12-20|2012-12-13|Method of increasing the efficiency of a beating of a chemical pulp|
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