Method of producing unbleached pulp with very low chemical oxygen demand

FIELD: paper-and-pulp industry.

SUBSTANCE: invention relates to production of pulps used in binder-based articles. Method of invention comprises repetitive soaking and washing of unbleached pulp in water, which is maintained in alkaline state at elevated temperature to obtain cellulose product characterized by chemical oxygen demand not above 2.0 kg per 10 kg dry cellulose.

EFFECT: improved strength characteristics of products.

14 cl, 1 dwg, 2 ex

 

The technical FIELD

The present invention relates to a method of manufacturing pulp mass and, more particularly, to a method of manufacture of unbleached pulp mass, with low COD, which are used in products on the basis of knitting.

The LEVEL of TECHNOLOGY

The internal construction of houses and other structures usually are protected from environmental influences external facing materials. These facing materials are usually strips or panels of wood, concrete, brick, aluminum, stucco, wood, composite materials or zemanovaload composite materials. Known cementogenesis composite material is amendability facing material, which usually consists of cement, quartz sand, unbleached wood pulp and various additives. Amendability facing material has several advantages over other types of coating materials, such as wood cladding materials, and it is resistant to weather influences, relatively cheap to manufacture, fire-resistant and resists damage caused by rodents or insects.

Commodity facing strips or panels of cement, fiber reinforced, are manufactured using the method of Watseka (Hatschek). The method of Watseka was original is Ino developed for the production of composite materials, containing asbestos, but is currently used for the production of non-asbestos cement composites reinforced with cellulose fibers. According to this method, fibers unbleached pulp again turn into a mass of warm water at alkaline pH 11-12,5; then the fibers are refined and mixed with cement, quartz sand and other additives, to form a mixture. Cementownia mixture is deposited on the felt substrate, dehydrated under vacuum and cured in the form to receive sheets cement matrix reinforced with fiber.

The curing of the cement matrix is complicated because of the presence of sugars or other organic substances. These substances slow down the hydration reaction of the cement and thus slow down the shrinkage or curing mortar or concrete. Shrinkage of cement deliberately slowed down in concrete mixtures with long-term traffic to relieve stresses induced by temperature (heat) when used in large concrete structures, and for decorative finishes washing. When measuring the amount of these organic substances manufacturers zemanovaload facing materials have observed an inverse relationship between the amount of these substances in unbleached pulp and strength properties of the final product. One of the means for measuring the amount of the quiet substances is a test for chemical oxygen demand (COD). When considering the harmful effects of these substances on the strength properties it is obvious that in this area there is a need in the pulp with a very low COD. The present invention fulfills this need and provides further related advantages.

BRIEF description of the INVENTION

The present invention is a method of manufacturing a cellulose product containing unbleached pulp, which is soaked and washed only in alkaline water, and after soaking and rinsing it has a COD is not more than 2.0 kg per 1000 kg of dry pulp, and preferably not more than 1.8 kg per 1000 kg of the cellulose is produced by repeated soaking of unbleached pulp in alkaline water at elevated temperature for organic matter washed out of the fiber in water. Cellulose repeatedly soaked and washed in a period of not less than 220 minutes at an elevated temperature, whereby the pulp is maintained at a temperature of not less than 70°C for at least part of the above 220 minutes Later repeatedly soaked and washed pulp is preferably dehydrated and dried.

BRIEF DESCRIPTION of DRAWINGS

The foregoing aspects and many of the attendant advantages of the present invention will become more apparent after a more Glubokov the understanding by reference to the subsequent detailed description and the accompanying drawing, which illustrates the steps of a method of leaching in caustic alkali for use in the present invention.

A DETAILED DESCRIPTION of the PREFERRED OPTION IMPLEMENTATION

The present invention is a method of manufacturing cellulose with a low chemical oxygen demand (COD), which is in particular used for reinforcing zemanovaload products. Most preferably, this method is way sulphate cooking unbleached pulp. Other types of cellulose with a low COD and methods of obtaining such cellulose is described in patent application U.S. No. 10/209497 called "UNBLEACHED PULP WITH a VERY LOW COD" and patent application U.S. No. 10/209446 with the title "METHOD of production of UNBLEACHED PULP WITH a VERY LOW COD", the details of which are clearly incorporated herein by reference in its entirety. In addition, herein incorporated by reference in its entirety patent application U.S. UNBLEACHED PULP WITH a VERY LOW COD" No. 10/330529 contained in the files of the attorney and filed together with the present application. However, there may be used various cellulose fibers, which are made from wood and other raw materials. From all sources of wood pulp the pulp is the most widely used because of its availability and rates.

To get the right fibers, wood pulp is the most preferred method is sulphate cooking. When using this method and taking into account the required properties of the composite material is the preferred source of wood fiber is long staple species of coniferous trees. Examples of such species are the following: southern pine, Douglas fir, spruce, Hemlock and pine Radiata. In addition to these sources of wood fibres can be used in other commodity types of pulp, including pulp made from short-fiber or long fiber species of trees, or recycled fiber pulp. You can use other fiber pulp from sawdust, shavings, chips from small particles of wood and other wood waste. The company Weyerhaeuser Company of Federal Way, Washington, sells one type of cellulose under the trademark TYEE. You can also use short wood fibers, which are normally obtained from deciduous trees, such as eucalyptus. Methods of obtaining these wood fibers are well known to experts in the field of pulp production. These fibers are supplied in the sale of a number of companies, including Weyerhaeuser Company. In addition to the sources of wood fibers and there are other natural sources of cellulose fibers, including straw, flax fiber, bast fiber, hemp fiber, etc. As wood fibers, these non-wood fibers that can the same be used to produce pulp for later use in zemanovaload composite materials. In addition, there may be used a combination or mixture of cellulosic fibers, such as a mixture of wood fibers, a mixture of wood fibers and other natural cellulose fibers or a mixture of other natural cellulose fibers.

With reference to the drawing unbleached pulp, preferably unbleached cellulose sulfate pulping to Kappa number, not exceeding 30 first passes through a conventional apparatus 1 for leaching of sulphate pulp and popmachine 2 for sulphate pulp. Unbleached pulp from mapmachine is in an alkaline condition and must be maintained in an alkaline condition (pH more 7,0) when it is processed in accordance with the present invention. Unbleached pulp from popmachine having a consistency of about 3-12%, may be filed in the diffusion column 3 and incubated for a certain period of time at a certain elevated temperature. The soaking operation is preferably carried out for at least 30 minutes at a temperature of at least 65°and more preferably at a temperature of about 70°C or higher. After exiting the first diffusion column 3 in the liquid pulp mass may be added a solution of sodium hydroxide to the extent necessary to maintain the pH greater than 7. Preferably, the consistency is reduced to approximately 4%. The liquid mass may be bezogene in press 4 to the consistency of about 30%, and then diluted to a consistency of 10%.

After press 4 or popmachine 2 if column 3 and press 4 are not used, the pulp is placed in a pool for the mass of high density or reservoir 5 for sulphate pulp, in which it can be within 15-430 minutes, but more preferably within 120 minutes the Purpose of the swimming pool for the mass of high density is to prevent the flow change when passing to subsequent operations.

After the pool 5 for the mass of high-density pulp is fed into the first of a sequence of 6 diffusion columns and units 7 for processing with consistency approximately 3-12%. Hot water and steam or only pairs are added to the pulp in the second sequence 60 diffusion columns for raising the temperature to a value preferably not less than 55°C. Then the cellulose sequentially soaked in the rest of diffusion columns of sequence 6. After soaking in every column 6 pulp is fed to the processing units 7. Preferably the pulp is soaked and washed or pressed multiple times, typically five (n=5) or six (n=6) times in the sequence of columns 6 and units 7, after which she goes in pool 8 for the masses. Each of the successive operations of soaking and diffusion of m which can take at least 15 min, but it can take up to 300 or more minutes These time periods include processing operations that follow each operation maceration. The exposure time depends on the size of the columns and the level of pulp in the columns.

Preferably, sequential soaking in diffusion columns 6 took place over 220-420 min, in any case, at an elevated temperature not lower than 55°C. Also preferably, the temperature in most of the columns 6 was above 70°C. Preferably, the total time soaking in the diffusion column 3, the pool for the mass 5 and the diffusion columns 6 was not less than 220 min (0-30 min in the diffusion column 3, 0-30 min in the pool 5, 220 min in diffusion columns 6) and not more than 660 min (0-60 min diffusion in column 3, 660 min in diffusion columns 6). Usually, however, the soaking occurs within approximately 330-420 min (0 min in the diffusion column 3, 330-420 min in diffusion columns 6).

After repeated soaking and processing pulp it can be sent to the pool store 8. The pulp can be maintained in the pool-vault 8 to 430 minutes However, it is generally preferable that the pulp was stored in the water storage pool 8 for about 100 min, if the pool store 8 is used. In this pool-store pulp masses who saves a concentration of about 10%. After this, the pulp is fed in the usual manner in a conventional press-Pat 10 and the dryer 11. After drying pulp in the form of sheets, it is cut to size and routed to the storage 12 for further shipment to the customer.

Unbleached washed cellulose obtained by the method according to the present invention, COD has no more than 2.0 kg 1 metric ton (1000 kg) and preferably not more than 1.8 kg per 1000 kg of the COD level is much lower than that achieved in conventional wood-pulp plants and, in particular, wood-pulp plants producing unbleached sulphate pulp. Also preferably, the cellulose obtained by this method had a Kappa number, not more than 30 and preferably not more than 25±3. The Kappa number is a measure of the lignin content in the pulp.

One of the most essential features of the present invention is that the pulp must be maintained in an alkaline condition as it was when the first operation of its soaking in column 3 and before the operation of a pulp drying. Preferably, the pH was maintained at the level not less than 8.0 and more preferably in the range of from 9 to 11 during the entire process, from soaking in the first diffusion column 3 and during all subsequent operations soaking in columns 6 and processing units 7. Pre is respectfully, for these operations the pH was maintained in the range from 10.0 to 11.0. Then the pulp is passed through a press-Pat 10 and the dryer 11. During these operations, the pH may be reduced, for example, up to 8.0-8.5 and below. In certain circumstances you may want to add alkaline solution (20% by weight aqueous sodium hydroxide) after the first diffusion columns 3 or after one of the columns 6. It was found that the addition of alkali in an amount not less than 2 kg 1 metric ton, and more preferably 4 kg 1 metric ton, will be sufficient to maintain the alkalinity of the pulp above pH 8.0 during the whole process. It is usually necessary to add alkali only at the initial stages of the process. For example, when bandwidth is approximately 25-40 tons per hour, you need to add 4 kg of alkali per 1000 kg of pulp during the initial period of 24-48 hours, when the pulp is passed through the first column 3 at a multi-day process (up to ten days). This will maintain alkalinity above pH 8.0 during the whole process, including the stage of drying.

The alkali may be added by line 3.2 after column 3, if it is used. Alternative or in addition, the alkali may be added by line 3.4 after one of the columns 6. In one embodiment of the present invention the column 3 and press 4 not used throughout the world is, and the alkali is added after the first or second column 6.

In one preferred embodiment, the present invention is carried out in the installation of blanching, which is usually included in the installation for production of Kraft pulp and used for transformation of unbleached pulp bleached pulp. Typical installation blanching usually contains a sequence of five or more oxide reactors, which are added various bleaching agents such as chlorine dioxide. Oxide reactors may have different flow characteristics, for example the downward flow upward flow, or combinations thereof. Reactor for oxygen delignification (diffusion column 3) can be located before the sequence of reactors blanching (diffusion column 6). In accordance with the present invention, the installation blanching is modified for use with the present invention by initial cutoff of the supply of bleaching agents in the bleaching reactor, and thereafter, the supply of bleaching agents in the bleaching reactors sequentially switches off when the pulp is sequentially supplied to the reactor blanching.

In a preferred embodiment, the alkali is introduced into the pulp mass along the line of 3.4 in the amount of 4 kg per metric ton of pulp. During this the cycle is very important, the temperature was maintained at 55°With or higher, and most of the columns preferably above 70°C. This is achieved by adding steam into the column in an amount necessary to maintain the above temperature. After soaking in each reactor bleaching the pulp is passed through a conventional washing or pressing units (units 7 for processing), which are usually located after each bleaching reactor. In one embodiment, during the washing and pressing consistency can be increased to 30% or up to 4%. Preferably for washing the pulp with fresh water, but if necessary can be used in white water or clean hot water from used wood stock setup.

After washing the pulp from the last reactor blanching it is placed in the tank, which is typically used for storage of bleached pulp (tank 8). Then it sequentially diluted to a consistency of about 1.5% and is fed into the hopper of the machine 10. Dehydrated sheet obtained by press-Pat, then passed through the dryer 11, for example a dryer Flacca (Flakt). After drying, the sheet is cut, stacks, stored and dispatched to the customers.

If desired, the pulp machine and dryer may not be used, is the pulp may be filed directly in the jet drying cylinder. At the outlet of the jet dryer get dried split fiber used in some products based binders. One inkjet drying cylinder, suitable for use in the present invention, the unit is "Fluid Energy Aljet Model Thermajet X0870L", manufactured by Fluid Energy Processing and Equipment Company. It is also possible not to apply the stage of drying, and use the pulp mass is not subjected to drying.

The following examples are intended only for clarity and is not intended to be any limitation of the scope of the invention.

EXAMPLE 1

Chemical oxygen demand (COD) is defined as follows. The sheets of pulp obtained in accordance with the preferred embodiment of the present invention, which has just been described, torn or cut into small pieces (squares with sides about 4 cm). These small pieces are mixed, and the humidity is measured in accordance with Tappi conditions T412 om-94. Then carefully otesyvajutsja 40 g of pulp by weight of absolutely dry sample. Prepares 2000 ml of 0.01 normal sodium hydroxide solution using distilled or demineralized water and sodium hydroxide laboratory grade purity. After this, the pulp is placed in a 2000 ml of 0.01 normal solution of Hydra is xida sodium, placed in the tie-breaker and ground for 15 minutes at a rotational speed of 3000 rpm in the British apparatus for assessing pulp" (or British chopper)described in the Tappi 205 sp-95. Liquid the pulp is then filtered immediately after grinding using filter paper Whatman No. 3. The filtering process is quite long, so a large portion of the filtrate passes through the filter. For the analysis of COD separated 250 ml of the filtrate. The sample is preserved with the use of 2.5 ml of 50%sulphuric acid. After that, the COD of the filtrate is measured using the titration method described in the publication "Standard Methods for the Examination of Water and Wastewater (Standard methods of examination of water and waste water, 20th Edition, 1998, Method #5220C, "Closed Reflux, Titrimetric Method". After this is determined by the value of COD in kg per metric ton of pulp based on the absolutely dry weight of pulp.

Samples of pulp were randomly selected in several production cycles by passing through the installation of bleaching with five columns (n=5). Originally unbleached pulp from southern pine was treated in the apparatus 1 for leaching of sulphate pulp and popmachine 2 when the consistency of approximately 10% at the outlet of popmachine, then it was submitted to the pool store. Then the pulp was fed a modified installation the ku blanching, which is modified by the initial cutoff of the supply of bleaching agents in the bleaching reactor, and thereafter, the supply of bleaching agents in the bleaching reactors sequentially switches off when the pulp is sequentially supplied to the reactor blanching. After each of the first two columns in sequence, the pulp was processed in the press washing machines. After each of the last three columns of the pulp was processed in a diffusion washing machines. Each press of washing machines consistency pulp varied from about 10% to about 30%, after which it decreased by dilution to 10%.

The rate of passage of pulp through a modified installation blanching was 29 tons per hour. Alkali was added after the first column at a rate of 4 kg per 1 metric ton of pulp. The exposure time in five consecutive vascular blanching was 30, 75, 30, 45 and 150 min, respectively. The temperature in five consecutive vascular blanching was 75°C, 75-80°C, 75-80°C, 75-80°and 75-80°C, respectively. Samples of the pulp were taken during production cycles after drying oven Flacca and checked for COD in the manner described above. Samples a, b, C, D, E, F, G, H and I were taken during the day ol the production period. The results are shown below.

SAMPLECOD (kg per meter. tonne)
And1,5
In1,65
1,5
D1,6
E1,5
F1,6
G1,6
N1,5
I1,3

The pulp produced in accordance with the above example, suitable for use in products based binders, such as panels, trims, decorative tiles and ceramic tiles with excellent strength properties. Cellulose can be entered in these products in an amount of about 6-10% by weight using the method of Watseka. More preferably, the cellulose can be entered in these products in an amount of about 8% by weight.

EXAMPLE 2

Samples of pulp were randomly selected in several production cycles by passing through the installation of bleaching with six columns. Originally cellulose TYEE was processed in the apparatus 1 for leaching of sulphate pulp and popmachine 2 with consistency approximately 10-12%. Then the pulp was fed pool store 5 for the mass of high density. She was is diluted to a consistency of about 4% of clean hot water. After storage 5 the pulp was fed a modified installation blanching. After each of the six columns in the sequence of the pulp was processed in washing machines. In each of the washing apparatus consistency pulp was changed from about 4% to about 10%, after which it declined by dissolving up to 4%.

The rate of passage of pulp through a modified installation blanching was 15 tons per hour. Alkali was added after the second column at a rate of 4 kg per 1 metric ton of pulp. The exposure time in six consecutive vascular blanching was 45, 15, 60, 120, 60 and 120 min, respectively. The temperature in six consecutive vascular blanching was 55°, 65°C, 75-80°C, 75-80°C, 75-80°and 75-80°C, respectively. Samples of the pulp were taken during production cycles after drying oven Flacca and checked for COD in the manner described above. Samples of the pulp were taken in production cycles after drying oven Flacca and tested on COD in the manner described above. Samples a, b and C were taken during a one-day production period. The results are shown below.

SAMPLECOD (kg per meter. tonne)
And1,47
In1,37
1,42

The pulp produced in accordance with the above example, suitable for use in products based binders, such as panels, trims, decorative tiles and ceramic tiles with excellent strength properties. Cellulose can be entered in these products in an amount of about 6-10% by weight using the method of Watseka. More preferably, the cellulose can be entered in these products in an amount of about 8% by weight.

Although the preferred embodiment of the invention has been illustrated and described, it will be clear that it can be made various changes without departing from the essence and scope of the present invention.

1. The method of manufacture of unbleached sulfate pulp, including repeated soaking and washing of unbleached pulp in water, which is supported in an alkaline condition at a high temperature to obtain a cellulose product, which has a chemical oxygen demand (COD) is not more than 2.0 kg per 1000 kg of dry pulp.

2. The method according to claim 1, characterized in that the cellulose has a COD of less than 1.8 kg per 1000 kg of dry pulp.

3. The method according to claim 1, characterized in that the cellulose repeatedly soaked and washed within the e less than 220 minutes

4. The method according to claim 3, characterized in that the pulp is maintained at a temperature of not less than 70°C for at least part of the above 220 minutes

5. The method according to claim 1, characterized in that the cellulose before leaching has a Kappa number, not more than 30.

6. The method according to claim 1, characterized in that the said pulp after washing has a Kappa number, not more than 30.

7. The method according to claim 6, characterized in that the said pulp after washing has a Kappa number, not more than 25±3.

8. The method according to claim 1, characterized in that the repeated soaking and rinsing are carried out in columns and washing machines multistage installation bleaching, and bleaching agents are not served in the installation blanching.

9. The method according to claim 1, characterized in that the alkali is added to the pulp during the soaking and rinsing.

10. The method according to claim 9, wherein the alkali is sodium hydroxide.

11. The method according to claim 9, characterized in that the alkali is added in the amount of 4 kg per 1000 kg of dry unbleached pulp.

12. The method according to claim 1, characterized in that the pulp is maintained at a pH of not less than 8,0.

13. The method according to claim 1, wherein the pulp comprises cellulose derived from Douglas fir.

14. The method according to claim 1, wherein the pulp comprises cellulose, obtained from the small hours of the IC wood.



 

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