Method of Papermaking

Abstract

An inventive method of papermaking can be provided for creating an optimum wet end environment. In a preferred method, an aqueous solution of sodium hypochlorite acidified by hydrochloric acid to have a pH of greater than or equal to 4 and less than 7 and adjusted to have an effective chlorine concentration of 1,000 to 10,000 ppm, preferably 3,000 to 8,000 ppm is prepared and charged to a white water pit in a manner to be effective chlorine concentration therein to greater than or equal to 0.5 ppm. Before a step of papermaking, it is preferred that aqueous solution sodium hypochlorite having pH of greater than or equal to 4 and less than 7 is added continuously or intermittently to a raw material water with the expectation that at breaching a residual chlorine concentration becomes greater than or equal to 500 ppm.

Description

THE FIELD OF TECHNOLOGY

The invention relates to a method which could simplify the chemical treatment in the paper making and provide an optimum wet end environment.

THE BACKGROUND OF TECHNOLOGY

Under upsurge of the concern of the global environment problem and neutralization of the condition of the paper making, the feed condition of the pulp raw material is increasing rigorously. Among them, increment of the mix quantity about DIP or coated broke, not only causes a lower product rate, lower physical properties of a wet end concerning filter water or lower paper quality such as strength and size degree, etc, but also causes the paper making machine breakdown because of the dirty. In order to repress the productivity and operability mentioned above, usually many kinds of chemical agent or chemical in great quantities have been used, resulting in that the paper making machine become dirty more.

Moreover, together with neutralization of the paper making process, the slime trouble caused by microorganism also increases immediately and lowering effects of the aluminum sulfate causes the inclusions such as pitch, anion trash, etc to be accumulated inside the system continuously. Nowadays, how to deal with the dirty of the paper making machine has become the hardest problem in raising productivity and operation. In the system of paper making machine, the slime trouble caused by microorganism and the inclusions of pitch, anion trash, etc become main reasons of the dirty.

Therefore, we usually propose to use organic antibacterial agent such as slime controlling agent to control the slime trouble. On the other hand, against the inclusions of the pitch or anion trash problems, we usually propose to use scale controlling agent and pitch controlling agent.

However, in the system of the whitewater circulation in the paper making factory, during a bleaching process of the pulp, a reduction bleach agent is remaining therein and processing water is also coming from a smoke taking off sulfuric device, resulting in existence of much reductive materials, such as the sodium sulfite, potassium sulfite with high concentration. Also, latex used for a binding agent in a coating solution, once be corrupted, makes the quantity of the germ be increased, and it will produce some reductive smelling materials, such as hydrogen sulfide, mercaptan and etc.

In the system of the processed water, if there are reductive materials mentioned above, previous antibacterial agents react with the reductive materials firstly before they react with the microorganism germ body. Therefore, the antibacterial agents become not able to play a role. As a result, it will bring some barriers to the stable operation of the paper making machine. Also, it will produce such a reductive material as hydrogen sulfide when the starch and latex, etc are corrupted constantly. Thus, the function of the antiseptic agents will be obstructed significantly, which is nowadays a big problem.

As the antibacterial method on condition of the existence of the reductive material, we usually choose the chlorite or bromite (bromous acid salt) to oxidize and decompose the reductive material first, and then use the previous organic antibacterial agent (Japanese Patent Kokai Hei 6-142661), or to use the organic antibacterial agent which is not under the influence of the reductive material or combination materials mixed with organic antibacterial agent (Japanese Patent Kokai Hei 7-258002).

SUMMARY OF THE INVENTION

However, we first use the chlorine series inorganic antibacterial agent which will make the reductive material oxidized and decomposed completely, and then use the previous organic antibacterial agent. Thus, it will remain a lot of effective chlorine with strong oxidization property, so that the dyestuff added in the product is oxidized to influence the color phase of the paper and still decay the metals material such as pipe used during the white water circulatory system. And the new type organic antibacterial agent which is difficult to be influenced by the reductive material, is effective in actual papermaking processes with 5-20 mg/L reductive material, but when there are reductive materials with higher concentration, we need to increase the antibacterial agent with high concentration.

On the other hand, about the dirty problem of the paper making machine, we usually use a slime controlling agent, a scale controlling agent, a pitch controlling agent to deal with it. However, there are few environments where chemical agents could play the best role. With increasing the types of the chemical agent, we need to adjust the management method of the chemical agent mentioned above.

In view of the above problems, after our sharp research, the inventor of this invention found that, if the chlorine series oxidizing agent represented by an acidic hypochloric acid soda (acidic sodium hypochlorite) aqueous solution, is added to a white water after papermaking in the wet end environment, not only a strong bactericidal effect can be obtained in place of a conventional antibacterial agent, but also as the scale controlling agent and pitch controlling agent, there can realized reduction of the decomposition of the organic and the influence of anion trash which would be caused by the various admixture. Therefore, a first object of this invention is to provide a method wherein the chlorine series oxidizing agent could optimize the environment of paper making in condition of the acidity.

With the optimization of the papermaking environment, in the bleach process before the papermaking process, we can also use the chlorine series oxidizing series represented by an acidic hypochloric acid soda aqueous solution for simplifying the control of the paper making processes. Therefore, a second object of this invention is to use the same chlorine series oxidizing agent not only in the papermaking processes but also in the bleach processes. Also, with the optimization of the papermaking environment, the possibility of reuse the papermaking drainage also increases. Therefore, a third object of this invention is to deal with the papermaking drainage, so that the processed water can be reused as industrial water.

Therefore, according to a first aspect of the present invention is a method of papermaking which comprises subjecting a papermaking raw water to a treatment, adding some necessary chemical treating agents into a white water wherein in place of one or more of the chemical treating agents an aqueous solution containing ions of hypochlorous acid or chlorous acid adjusted to have pH of greater than or equal to 4 and less than 7 is prepared and charged continuously or intermittently into the white water with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of more than 0.5 ppm, more ideal is more than 1 ppm.

The dilution aqueous solution that contains ions of hypochlorous acid or chlorous acid, is one containing not only the hypochlorous acid and chlorous acid, but also their sodium or potassium salts in an acidic condition and also bromous acid, hypobromite and their sodium and potassium salt, etc. However, in this invention, it is preferred to use the sodium hypochlorite aqueous solution, having a concentration between 1000 ppm-10000 ppm, preferably 3000 ppm-8000 ppm, at a weak acidity scope of pH of 4-6.5, because they can show a strong disinfect property, a strong organic matter decomposition property, and a strong diselectrification property of anion trash.

In this invention, the purpose of adding a hypochlorous acid solution is not only to control the slime, but also to control the pitch and the anion trash. Therefore, it is preferable to add an aqueous solution containing ions of hypochloric acid or chlorous acid adjusted to have pH 4-7 continuously or intermittently into the white water after papermaking with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of less than 20 ppm, preferably less than 10 ppm. In the white water circulatory system, it is preferable to add an aqueous solution contains ions of hypochloric acid or chlorous acid to have a pH 4-7 into the circulating white water with the expectation that at the time of circulating a residual chlorine concentration in the white water is kept at the concentration of less than 5 ppm, preferably 0.1 to 3 ppm, and a residual chlorine concentration out of the white water circulation system is kept at the concentration of less than 1 ppm. On the other hand, in order to take the paper making drain in to make re-use after papermaking, it is preferable to add an aqueous solution containing ions of hypochloric acid or chlorous acid adjusted to have a pH 4-7 into the white water with the expectation that according to a value of BOD or COD in a waste water, a residual chlorine concentration in the waste water is kept at the concentration of more than 10 ppm. The waste water kept at the concentration of more than 10 ppm is re-used for processing water.

In a case of bleaching a papermaking raw water, an aqueous solution containing ions of hypochloric acid or chlorous acid adjusted to have pH of greater than or equal to 4 and less than 7 is charged continuously or intermittently into the white water with the expectation that at the time of bleaching a residual chlorine concentration in the papermaking raw water is kept at the concentration of more than 500 ppm. It can simplify several bleach steps, and it is easy to manage the medicine control. Moreover, preferably it can raise the processing effect in the papermaking mentioned above. The purpose of the bleach process is to simplify several bleach after de-lignin. However, the inventive bleaching method can be applied to the wastepaper after de-inking and the bleaching process may be applied at the same time of de-inking.

In the bleaching process, the inventive aqueous solution contains ions of hypochloric acid or chlorous acid can be used, in place of them it may contain not only the sodium hypobromite, but also the potassium hypobromite, etc. However, it is preferable to use an aqueous solution containing 1000-20000 ppm, preferably 3000-10000 ppm of sodium hypochlorite and adjusted to a pH of 4-7, preferably to a pH of 4.5-6.5. The bleaching process is preferably carried out at a pulp concentration of 3 to 30 wt. % in the papermaking raw water. When the concentration of the pulp is high, it is recommendable to add the solutions which contain the hypochlorite in many times. At the first stage, it is preferable to add the first hypochlorite solution of more than 3000 ppm and the second, the third solution with a lower concentration of hypochlorite. It is our surprising that the solution containing ions of hypochlorous acid can not only show a effective disinfect effect against microorganism within a scope of 4-6.5 of pH, but also shows a same strong bleach effect as ozone or chlorine dioxide.

The present invention is also a method of papermaking which comprises subjecting a papermaking raw water to a treatment of de-lignin and de-inking, bleaching a white water, papermaking the white water and then discharging a waste water treated by necessary chemical treating agents, wherein in place of one or more of conventional chemical agents an aqueous solution contains ions of hypochloric acid or chlorous acid adjusted to have pH of greater than or equal to 4 and less than 7 is charged continuously or intermittently into the white water in one or more of the all steps, measuring change of Oxidation-Reduction Potential before and after charging the aqueous solution in the white water and the waste water and finally controlling the charging amount of the aqueous solution automatically according to the measuring signal. For example, compared with the calibration curve which is prepared before, a suitable quantity of the solution can be controlled according to this comparing signal. In this invention, the solution containing ions of hypochloric acid or chlorous acid adjusted to have a pH of weak acid is charged continuously or intermittently. Therefore, by measuring the oxidation-reduction potential and the pH, the control accuracy can be raised. Thus, it is more preferred.

In a papermaking process after the bleaching process, the hypochlorous acid can exert the effective microorganism disinfects effects on condition that the pH is 4-6.5 and the concentration of the residual chlorine is more than 0.4 ppm. By controlling the quantity of bacteria less than 10⁴, it can exert effect of the slime control. But in this invention, we have to resolve the organic compound and pitch, etc and clean the anion trash, so it is more preferred to set the concentration of the residual chlorine at 0.5-1 ppm. However, if it exceeds 10 ppm, the hypochlorous acid solution can not be all consumed in the whitewater pit and will remain in the circulation white water. If remain a little, it will not influence the environment of papermaking. So we can set the concentration of the residual chlorine to less than 20 ppm.

The aqueous solution which contains ions of hypochloric acid or chlorous acid in the papermaking process can be instead of the electrolysis aqueous solution that contains ions of hypochloric acid or chlorous acid. But, it is preferred to use sodium hypochlorite or sodium chlorite which do not produce chlorine gas, and having the pH of 4-7 ppm, especially less than 6.5 ppm, and the concentration between 1000 and 20000 ppm, especially between 3000 and 10000 ppm. The aqueous solution that contains hypochloric acid can be made by the Steri Mixer made in HSP Co. Ltd at the spot. When made at the spot and for input, it is preferred to make the solution having a pH of 4 to 6.5 ppm, and a concentration between 5000 and 20000 ppm, especially between 5000 and 10000 ppm. When made at the other factory, it must be carried with the tank lorry, so it is preferred that the pH is from 5 to 6.5 ppm, the concentration is from 3000 to 8000 ppm.

Usually, when we make the aqueous solution with high concentration of sodium hypochlorite under hydrochloric acid acidity, if the pH descends to less than 4, there will be a chlorine gas, so we use a dilute hydrochloric acid of less than 30%, more preferably less than 15%, most preferably less than 10%. To mix with the aqueous solution of sodium hypochlorite of pH 4 to 6.5, more preferably pH 5 to 6 and the concentration of the effective chlorine of is diluted to from 3000 and 10000 ppm with water, so that we can produce the aqueous solution of high concentration sodium hypochlorite which is suitable for white water without producing chlorine. Especially, when we modulate the acidic aqueous solution of sodium hypochlorite, it is preferred to make pH much lowered below a predetermined value with a pH regulator such as the inorganic agent that do not affect the effective chlorine, for example KHCO₃, carbonic acid hydrogen potassium or NaHCO₃, carbonic acid hydrogen sodium.

As noted above, if we add the aqueous solution that contains ions of hypochloric acid or chlorous acid, which shows a weak acidity and the effective chlorine concentration of 1000 to 20000 ppm, more preferably 3000 to 10000 ppm to the white water of the wet end after the papermaking on condition of acidity. As shown in FIG. 3, the environment of the wet end of the papermaking can be improved by the present invention.

(1) It shows disinfect effect powerfully and need not addition of the slime controlling agent. And by keeping the concentration of the remain chlorine to 0.1-3, more preferably than 5 ppm, the papermaking from used paper can be realized, wherein number of bacterium in the circulating white water is controlled to be kept less than 10⁵, preferably 10⁴.

(2) It makes anions attached to the cellulose to be neutral, so that the dosage of the paper strengthen agent can be reduced by a degree of 20-35%.

(3) Oxidation of the hypochloric acid water can resolve ester part of the vinyl or acrylic compounds, etc. Thus, the dosage of the pitch control agents is reduced by a degree of 20-30%.

(4) It can decompose organic compounds and clean or reduce the influence of the various admixture anion trash, by which the effect of the chemical agent added to the breakdown processing can be improved with maximum

(5) It can decompose the organic matter such as hydrogen sulfide etc, so that we can get a good deodorant effect. And drainage COD can be also reduced by decomposition of the organic matter.

(6) By using the chlorine series oxidizing agent which is represented by acidic sodium hypochlorite solution, we can carry out the drainage with a further processing, and reuse it as the industry water.

(7) By using the inventive chlorine series oxidizing agent which is represented by acidic sodium hypochlorite solution to bleach the papermaking raw water after a treatment of de-lignin and de-inking, it can enhance the effect that mentioned above (1) to (6), and simplify the whole papermaking processes of the chemical agent treatment extremely.

(8) By measuring the redox potential of the aqueous solution that contains ions of hypochloric acid or chlorous acid adjusted to be weak acidity before and after discharging, together with the pH, it can control the total chemical agent management in the papermaking processes.

These and other objects and advantages will be apparent from the drawings and the following description of embodiments according to the present invention.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a schematic view of a white water circulation system provided with a hypochlorite water supply system.

FIG. 2 is a schematic view showing the specific examples of the control system in the invention.

FIG. 3 is a view showing mechanism of the method of papermaking according to the present invention.

FIG. 4 is a schematic view of the examples of the system in case of waste paper in the invention.

FIG. 5 is an outline view of the overall structure of the best way to deodorize of the paper making equipment in the invention.

FIG. 6 is a vertical view of an embodiment of the treatment room according to the present invention.

FIG. 7 is a side view of the structure of the treatment room mentioned above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Mixed the 10% dilution hydrochloric acid with the 12% sodium hypochlorite solution, in the range that the pH is 5-7, dilute the concentration of the effective chlorine to 3000-10000 ppm with water, (Sometimes we call it hypochlorous water in the following). At this time, use the manufacturing device of the aqueous solution that contains hypochloric acid—Steri Mixer which is made in HSP Co. Ltd.

EXAMPLE 1

FIG. 1 is the schematic view of the wet end environment control system of the white water circulation in the papermaking process used to a conventional wastepaper raw material. The whitewater after papermaking in the papermaking machine 100 should be sent to the whitewater pit 110 first in which the slime can be treated, then a part of it will be circulated to the stock inlet 150, the other part will be sent to the drainage pit 120. On the other hand, the pulp raw materials will be sent to the seed box 140 from the de-inking process pit 160, and through the screening pit 130, be sent to the stock inlet 150, finally arrive at the papermaking machine 100. Here is a white pit 110 in a papermaking machine 100, but usually there are four papermaking machines in tandem and there are layout of the white water pit 110(a), (b), (c) and (d) on every papermaking machine.

In the hypochlorite water supply system 200, according to the direction of the arrow 170, the hypochlorous water is supplied continuously for the white water pit (a), (b), (c) and (d). There measurement devices D1-D4 are arranged on all pits which is to measure the concentration of the residual chlorine in the white water, and the measurement signal 80 is feedback to the water supply system of the hypochlorous water, and the supply is adjusted. The measurement device is made up of an oxidation-reduction potential meter, but it is preferred to use the meter with a pH meter. We have to prepare a calibration curve based on change of oxidation-reduction potential caused by a residual chlorine before and after charging and compare a measuring signal with the calibration curve to adjust the supply of the hypochlorous water. Control of the supply may be done. Furthermore, we also can measure out the residual chlorine at suitable positions in the whitewater circulatory system.

As shown in FIG. 2, the hypochlorous water supply system 200 can be made. Namely, from the solution tank 1 with sodium hypochlorite or sodium chlorite and diluted hydrochloric acid tank 2, through a constant rate pump 3 and 4, the aqueous solution of the diluted hydrochloric acid and sodium hypochlorite are sent to the mixer 5 and 6. In addition, industrial water is supplied to the mixer 5 and 6 from the other channels. Here, the aqueous solution of the diluted hydrochloric acid and sodium hypochlorite is mixed with the industrial water to be diluted. So that, the pH is adjusted to 4-6.5 and the concentration is adjusted to 1000-10000 ppm, more preferably 3000-8000 ppm. The aqueous solution of the dilute sodium hypochlorite is adjusted in the mixer 5 and 6 and supplied by the pipe of the whitewater pit 110 or the chest discharge pit that connect to the water end. At this pipe, there is provided a generated water header, and a control valve at the generated water header. The generated water header is used to adjust the quantity of the aqueous solution of the dilution sodium hypochlorite to be charged in the whitewater pit of water end or the chest discharge pit. 10 is a power control panel, it controls the quantity of the water, the hypochlorous acid soda, the chlorite soda and the dilute hydrochloric acid that is supplied to the mixer, and it also control the control valve of the pipe 9 so that to control the quantity of the hypochlorous acid that supplied to the whitewater pit 110, drainage pit 120. Furthermore, 7 is the hypochlorous acid auxiliary tank, 8 is the dilute hydrochlorous acid auxiliary tank.

Usually, a measuring device which is used to measure the concentration of the residual chlorine in whitewater is attached to the whitewater pit or chest drainage pit, send this measuring signal to the power control panel 10, so that the input is used to adjust the amount of dilute aqueous solution of the dilute sodium hypochlorite or chlorite to be charged in the whitewater pit of water end or the chest discharge pit. However, it is preferred to control the concentration of the residual chlorine at a range of 0.1-3 ppm at most 5 ppm in whitewater circulation system, on the other hand it is preferred to control the concentration of the residual chlorine under 1 ppm out of the whitewater circulation system.

By adjusting the concentration of the residual chlorine mentioned above, in the papermaking for a waste paper, we can control the number of the bacteria under 10⁵, preferably 10⁴. Moreover, it can be found that the concentration of the residual chlorine does not cause production of a harmful tri-halomethane.

In addition, in this example mentioned above, the aqueous solution containing sodium hypochlorite of 6000 ppm with hydrochlorous acid is prepared at the spot and used. However, a high concentration aqueous solution of 3000 to 10000 ppm has a good nature of storage, so it can be stored in the tank and be used.

EXAMPLE 2

The kind of the waste paper to be used: the waste paper that recovered from the office (the first-class and middle-waste are mixed together), will be bleached as following before papermaking:

Analysis and evaluation/whiteness: JIS-P8123 (Hunter method)

Residual ink quantity: By using a microscope (10 times) and image analysis device (LA-525 made by Piaz Company), the area of ink at the scope of a certain vision is indicated by ratio (%).

An office waste paper is put into the pulper and dissociated therein. The condition of the pulper is 4.5% of pulp concentration, the temperature is 26° C. and NaOH is 1.0%. Then, the waste paper pulp is dehydrated by the screw press until the pulp concentration reaches 18%, and the pulp of the waste paper is kept in an aging tower for 12 hours. Then, dilute the concentration of the pulp to 3.5% and extract the pulp from the aging tower, then dedust in the Jonson screen and FN screen, then, clean it in the extractor. Then, after dehydrated until reach 31% by the screw press, add the aqueous solution which contains sodium hypochlorite of 3000 ppm at pH of 5. Then after kneading in the shredder, and making it stay in the bleach tower, the condition of the bleach tower is the concentration of the pulp of 29%, temperature of 36° C. and the bleaching time is 10 hours. Then, dilute the concentration of the pulp to 3.5% and extract the pulp from the bleach tower and clean in the extractor. After dehydrated until reach 31% by the screw press, add the aqueous solution which contains the hypochlorite acid soda and the pH is 5, 3000 ppm, then kneading in the shredder, and make it stay in the bleach tower. The condition of the bleach tower is kept at the pulp concentration of 28%, the temperature of 40° C., the bleaching time of 10 hours. Then, dilute to 3.5% after bleach, extract from the bleach tower and sent it to the machine chest after adjusting the pH. Then, dedust it by the cleaner after adjusting the concentration of the pulp, then carrying out the same papermaking process as the Example 1.

Comparison Example 1

As Example 2, a pulp material water is subjected to a series of processes such as alkali processing, dehydrating, aging, dust-removing, cleaning and dehydrating and reaches to the concentration of the pulp to 15%. Then, the pulp water is mixed the sodium hypochlorite by a medicine mixer, and then is subjected to a process of cleaning. The results are shown in Table 1.

TABLE 1
	Whiteness (%)	Residual ink quantity (%)
Implementation	183.1	0.002
Comparison	173.8	0.36

The method in the invention, compared with the method of the bleach of the hypochlorite at the condition of alkaline after alkali processing, can give it more whiteness.

EXAMPLE 3

Put a kraft pulp (the whiteness is 47.2%, the kappa number is 9.9) with absolute dry mass 80.0 g after the alkali oxygen bleaching to the plastic bag. Add the 1000 ppm aqueous solution of sodium hypochlorite at pH of 4.5 after adjusting the concentration of the pulp until 10% by the ion exchange water, immersed for 60 minutes at the room temperature, as the first stage bleaching. After diluting the pulp to 3% with the ion exchange water, dehydrate and clean it with the Buchner funnel. Put the pulp into a plastic bag, adjust the concentration of pulp to 10% with the ion exchange water, then add the 3000 ppm solution of sodium hypochlorite at pH of 5, immersed for 90 minutes at the room temperature as the second stage bleaching. After adjusting the concentration of the pulp to 3% by dilute of the ion exchange water, there form the pulp mat by the Buchner funnel. Then dehydrate it with the squeeze pulp machine and obtain the (the concentration of 30.0%) pulp.

Then, put the pulp mentioned above to a plastic bag, add the 1500 ppm solution of sodium hypochlorite at pH of 6 after adjusted the concentration to 10% by the ion exchange water. Processed for 180 minutes at normal temperature, then it will be bleached finally. From this method, we obtain the bleaching pulp having the whiteness of 80%. Measure the value of the potassium permanganate, the quantity of the hexenuronic acid of the bleaching pulp and the PC value of the bleach pulp sheet made by the bleaching pulp that after 48 hours, and get the result of 3.0-4.0.

Comparison Example 2

Except using a sodium hypochlorite alkali solution instead of hypochlorous acid, the operation is carried out in a same manner as the Example 2. The pulp after dealing with the alkali sodium hypochlorite solution is not bleached absolutely. Thus, the whiteness is not well.

EXAMPLE 4

FIG. 4 is a flow chart of waste paper recycled paper. Put the 3000 ppm solution of sodium hypochlorite at pH of 5-6 into the whitewater pit, scum pit and pulp pit, considering the water quantity therein. And adjust it to make the whitewater pit, the scum pit to be 20-30 ppm and the pulp pit to be 10-5 ppm.

In figure, 301 is a hydrochloric acid tank, equipped with the 10% dilute hydrochloric acid. 302 is a tank of solution of sodium hypochlorite, equipped with the 10% aqueous solution. Send the dilute hydrochloric acid and the sodium hydrochlorite aqueous solution to the reserve tank 307, 308 of the first and the second high concentration (3000 ppm) of sodium hypochlorite generator 305, 306 (the Steri Mixer made by HSP company) by pump 303, 304. In the first and second Steri mixer 305, 306, dilute the aqueous solution of the dilute hydrochloric acid and the aqueous solution of sodium hypochlorite with a river water to produce the 3000 ppm aqueous solution of sodium hypochlorite at pH of 5-6.

This aqueous solution of sodium hypochlorite is sent to the pulp pit 310 first by the pump 309 and then to the pulper containing the wastepaper and water. Considering the water 20 quantity and bactericidal effects therein, adjust the concentration to 10-1 ppm. However, it is preferred to start with the high concentration at the beginning.

Then, sent the pulp to the chest tank 311 and 311 and put the pulp into the papermaking machine 312 from the white pit 313. Because the white pit is circular, considering the water quantity and bactericidal effects, put the 3000 ppm aqueous solution of hypochlorous acid soda into the white pit, and adjust it to 100-10 ppm, especially 30-20 ppm. In addition, for the chest discharge pit 314, it is preferred to do the same disinfection and deodorization as the pulp pit 1. For the chest tank 311, we can also do the same process of disinfection and deodorization.

The drainage that comes from the chest tank 311 and papermaking machine 312 is recovery at the chest discharge pit 314 and treated at the drainage treatment pit 315. Recycle sludge and put them to sludge treatment pit 316. Recycle scum go by the sludge pit 318 by the sludge sent back device 317. On the other hand, emit the drainage after sludge treatment at the sludge treatment device 316.

In the scum recovery system that mentioned above, considering the water quantity and bactericidal effects, put the 3000 ppm acidic aqueous solution of sodium hypochlorite into the white pit, and adjust the sludge tank to 100-10 ppm, especially 30-20 ppm.

EXAMPLE 5

FIG. 5-FIG. 7 are schematic views showing best methods for deodorant the papermaking equipment. In the figure, there is the 12% sodium hypochlorite solution in hypochlorous acid reserve tank 410 and the 9% dilute hydrochloric acid in serve tank 411. The sodium hypochlorite solution and the dilute hydrochloric acid in 410, 411, which are sent to the auxiliary tank 421, 422 that in manufacture device 420, which made high concentration sodium hypochlorite solution through pipelines 414, 415 and pumps 412, 413.

There, pipelines 423, 424 extending from the auxiliary tank 421, 422 and the pipeline 423, 424 are connected into the generator 425. In the generator 425, mix 9% solution of diluted hydrochloric acid with 12% solution of the sodium hypochlorite.

Moreover, there is connected a water pipeline 429 to the generator 425. There are mounted a filter 4210 and a pressure reducing valve 4211 in the middle part of the water pipeline 429. The water that filtrated the inclusions by filter 4210 and reduced to 0.25 Mpa by the pressure reducing valve 4211 is supplied to the generator 425. And dilute the hydrochloric acidity aqueous solution of sodium hypochlorite of high concentration by water to the available chlorine of 1000-10000 ppm for example 6000 ppm and pH of 5-6.

In the generator 425 in this example, there can be made 2000 L of acidic high concentration sodium hypochlorite solution having the concentration of the available chlorine of 6000 ppm and pH of 5-6 per every hour.

The high concentration sodium hypochlorite solution is stored in the reserve tank 427 and sent to the scrubber 430 by the send pump 428. In the scrubber 430, the solution is sprayed to be the droplet with the average particle size in scope of 10 μm-70 μm by the vibration of ultrasonic and sent to the many spit exit 432 in the treatment room 440 (dealing space) by the blower 431.

At the entrance 440B of the treatment room 440, there connected the pipeline 441 that come from the equipment of papermaking factory. There layout a fans 442 that drove by motor 442A at the middle part of the pipeline 441. The fans 442 transmit the foul air in the factory into the treatment room 440.

There is arranged a partition in the treatment room 440, to make a tortuous path 440D bent-extending from the entrance 440B of the treatment room 440 to the exit 440C.

Further, in the exit 440B of the treatment room 440, there is a photocatalyst deodorant device 443. In the photocatalyst deodorant device 443, there is installed a vector such as the wire mesh bearing the photocatalyst. At the same time, there also is installed a ultraviolet lights (no icon). When the UV-A wave (wavelength 300 μm˜400 μm) irradiate the photocatalyst, such as the film of titanium dioxide, there will be the e⁻ (electronic) and h⁺ (positive hole) in the film of titanium dioxide. The h⁺ (positive hole) generate to be the OH (Hydroxy), and decompose the odor ingredients with its oxidation ability (2 times Oxygen).

For example, when deodorizing the odor from the papermaking factory equipment, the dilute hydrochloric acid and sodium hypochlorite solution is sent to the generator 425, and are mixed, and at the same time, sent the water without inclusions to the generator 425 to dilute and make 2000 L per hour of high concentration sodium hypochlorite aqueous solution with hydrochloride acidity having available chlorine concentration (6000 ppm) and the pH of 5-6. The high concentration sodium hypochlorite aqueous solution is sent to the scrubbers 430, through the ultrasonic vibration, the droplet with the average particle size in scope of 10 μm-70 μm is sprayed. The droplet with high concentration sodium hypochlorite solution is sent to the many spit exit 432 of the treatment room 440 by blower 431, then to be sent to the treatment room 440.

On the other hand, when a fan 442 of the pipeline 441 is driven by a motor 442A, the foul air in the factory is sent to pipeline 441, and transmitted into treatment Room 440. This air flows to the export 440C by the crank pathway 440D of the treatment room 440. This air is deodorized by contacting the droplet with the high concentration sodium hypochlorite solution, and be sent from the entrance of treatment room 440 to photocatalyst deodorant device 443. Finally it will be emitted to the atmosphere after further deodorizing by the photocatalyst.

THE INDUSTRIAL AVAILABILITY

To sum up, this invention is effective in the papermaking not only a used wastepaper, but also for the virgin pulp. However, in the case of the latter, because the bacteria number, pitch and organic compounds species are different from the wastepaper pulp, it is preferred to adjust the concentration of the acidic sodium hypochlorite aqueous solution considering the status of the spot.

Claims

1. A method of papermaking which comprises subjecting a papermaking raw water to a treatment of de-lignin and de-inking and adding some necessary treating agents into a white water wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of more than 0.5 ppm.

2. A method of papermaking according to claim 1, which further comprises a step of bleaching a papermaking raw water wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of bleaching a residual chlorine concentration in the papermaking raw water is kept at the concentration of more than 500 ppm.

3. A method of papermaking according to claim 1, which further comprises making the white water circulating wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of less than 20 ppm, preferably less than 10 ppm.

4. A method of papermaking according to claim 1, which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that at the time of circulating a residual chlorine concentration in the white water is kept at the concentration of less than 5 ppm, preferably 0.1 to 3 ppm.

5. A method of papermaking according to claim 1, which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that at the time of circulating a residual chlorine concentration out of the white water circulating is kept at the concentration of less than 1 ppm.

6. A method of papermaking according to claim 1, which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that according to a value of BOD or COD in a waste water a residual chlorine concentration in the waste water is kept at the concentration of more than 10 ppm.

7. A method of papermaking according to claim 6, wherein the waste water kept at the concentration of more than 10 ppm is re-used for processing water.

8. A method of papermaking from used paper, wherein number of bacterium in the circulating white water is controlled to be kept less than 105, preferably 104.

9. A method of papermaking which comprises subjecting a papermaking raw water to a treatment of de-lignin and de-inking, bleaching a white water, papermaking the white water and then discharging a waste water treated by necessary treating agents, wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water in one or more of the all step, change of oxidation-reduction potential before and after charging the aqueous solution in the white water and the waste water is measured and the charging amount of the aqueous solution is automatically controlled according to the measuring signal.

10. A method of paper making according to claim 9, wherein pH value before and after charging the aqueous solution in the white water and the waste water is measured together with the oxidation-reduction potential.