JP2003342301A - Regeneration of spent acid and method for its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for regenerating the spent acid after being used for hydrolysis reaction in the process for manufacturing cellulose powder or crystalline cellulose powder by hydrolyzing pulp cellulose with a mineral acid and a process for manufacturing the cellulose powder or crystalline cellulose powder by using the regenerated spent acid. <P>SOLUTION: Cellulose powder or crystalline cellulose powder is manufactured by hydrolyzing pulp cellulose with a mineral acid. The spent mineral acid after the hydrolysis is regenerated by adding ozone generated with an ozone generator or waste ozone gas discharged from the ozone bleaching step in a pulp bleaching process. The regenerated acid alone or together with a newly added fresh mineral acid is used for the hydrolysis of pulp cellulose. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of regenerating a waste acid after a hydrolysis reaction in a step of hydrolyzing pulp cellulose with a mineral acid to produce a cellulose powder or a crystalline cellulose powder, The present invention relates to a method for producing a cellulose powder or crystalline cellulose powder pulp used.

[0002]

2. Description of the Related Art Cellulose powder and crystalline cellulose are
Used in rubber and plastic fillers, food additives, pressure sensitive paper compounding agents, industrial filter aids, welding rod shaping agents, etc. In these applications, high-whiteness cellulose powder and crystalline cellulose powder are required, and bleached virgin pulp such as softwood pulp and hardwood pulp is used as a raw material,
It is manufactured by chemically hydrolyzing and / or mechanically crushing these.

The acids used to hydrolyze bleached pulp are
Mineral acids such as sulfuric acid, sulfurous acid, nitric acid, hydrochloric acid and phosphoric acid.
Pulp cellulose is suspended in mineral acid adjusted to an appropriate concentration and reacted at high temperature. After completion of the hydrolysis reaction, the pulp hydrolyzate and the mineral acid are solid-liquid separated. The pulp hydrolyzate is washed to remove the adhering acid and then undergoes steps such as neutralization, drying, pulverization and classification to produce a cellulose powder or crystalline cellulose powder product.

The separated mineral acid is colored due to the denatured product of the hydrolyzed carbohydrate, but the acid concentration is still high enough that it is mixed with fresh mineral acid and reused several times in the hydrolysis reaction. It However, when the reuse is repeated, the content of the coloring substance in the separated mineral acid gradually increases, and the coloring substance adheres to the product of the cellulose powder or the crystalline cellulose powder, and the product whiteness standard cannot be maintained. Ultimately, this used mineral acid must be discarded. This acid is hereinafter referred to as waste acid. Due to the generation of waste acid, it is necessary to supplement the mineral acid used for hydrolysis in the form of new mineral acid, and there is a problem that the production cost increases accordingly. Also, since the waste acid is a high-concentration acid, it cannot be discharged as it is,
Alkaline chemicals are added to neutralize and then discharged. Therefore, there is a problem that the cost required for neutralization is high.

As a technique for reusing the waste acid, Japanese Patent No. 8849
No. 01, which contains by-product of the chlorine dioxide generator used as a bleaching agent for pulp, sulfuric acid as the main component, as well as sodium sulfate, chlorate, salt and chlorine dioxide. A technique for producing a high-whiteness cellulose powder by hydrolyzing cellulose with waste acid has been described and is already known. By this method, the number of reuses of the acid used in the hydrolysis reaction can be increased,
From the economical point of view, it is desired to increase the number of times of use.

Further, in the chlorine dioxide generator, the R2 method that produces by-produced sulfuric acid and chlorine as by-products that have been conventionally adopted in many pulp mills, the R3 method that does not produce by-produced acid, the R5 method, and SVP.
Method, the conversion to the SVP-Total HCl method is advancing. Also, as environmental regulations for pulp mills have increased, ECF that does not use chlorine as a bleaching agent in the pulp bleaching process.
Bleaching is becoming the norm and chlorine dioxide usage is increasing. From this situation, in the chlorine dioxide generator, R6 method, R7 method, SVP-Mars method, which does not produce by-produced acid and chlorine,
The R8 method, SVP-MeOH method, SVP-Lite method, SVP-H ₂ O ₂ method, etc. have been developed, and these methods are expected to become the mainstream in the future.
Therefore, even in manufacturing facilities that currently use chlorine dioxide generator waste acid for the hydrolysis reaction of cellulose, after the chlorine dioxide generator is upgraded to a new model, the chlorine dioxide generator waste acid can be used. Therefore, it becomes necessary to use the whole amount of the required acid as a new mineral acid, which increases the production cost of the cellulose powder or the crystalline cellulose powder. From this situation as well, it is desired to develop a new technology capable of reusing waste acid.

[Problems to be Solved by the Invention]

[0007] The problem to be solved by the present invention is to regenerate a waste acid after a hydrolysis reaction in the step of producing a cellulose powder or a crystalline cellulose powder by hydrolyzing pulp cellulose with a mineral acid, and the regenerated waste. It is to provide a method for producing a cellulose powder or a crystalline cellulose powder using an acid.

[Means for Solving the Problems]

In the process of producing pulp powder or crystalline cellulose powder by hydrolyzing pulp cellulose with mineral acid, waste acid after hydrolysis reaction is discharged from ozone generated in an ozone generator or from ozone bleaching stage of pulp bleaching process. It is regenerated by adding ozone exhaust gas. Regenerated waste acid is used alone or new mineral acid is added to it to hydrolyze pulp cellulose.

DETAILED DESCRIPTION OF THE INVENTION

A method of regenerating the waste acid after the hydrolysis reaction in the step of producing pulp powder or crystalline cellulose powder by hydrolyzing pulp cellulose with a mineral acid, which is the first invention, will be described. Regardless of the grade of cellulose powder or crystalline cellulose powder produced from pulp cellulose as a raw material, that is, regardless of the bulk specific gravity of the product, the average particle size, the degree of crystallinity, etc., the waste acid after the hydrolysis reaction of pulp cellulose is Can be applied to the present invention.

Acids usable in the present invention include sulfuric acid, sulfurous acid,
Mineral acids such as nitric acid, hydrochloric acid and phosphoric acid are preferred, with sulfuric acid being preferred. Organic acids such as formic acid and acetic acid are oxidatively decomposed by the addition of ozone, and the acid concentration decreases. Also, since ozone is consumed by organic acids, the decomposition of coloring components in waste acid,
It cannot be used because the decolorizing effect is significantly reduced.

The mixture of pulp hydrolyzate and waste acid, which has undergone the hydrolysis reaction, is separated into pulp hydrolyzate and high-concentration waste acid by a solid-liquid separator such as a vacuum rotary drum type filter, and pulp hydrolysis is performed. The substance flows to the next step of washing, neutralization, drying, crushing, and classification steps, and waste acid is recovered.

Ozone gas is blown into the waste acid collected in the tank to decompose the coloring components contained in the waste acid by the oxidizing action of ozone. Ozone gas can be generated by a known method in an ozone generator using air or oxygen as a raw material, and this ozone gas can be used in the present invention,
In the ozone bleaching stage of pulp, ozone exhaust gas discharged after bleaching with this ozone gas can also be used. Furthermore,
A mixture of both can also be used as the ozone gas of the present invention.

The method of blowing ozone into the waste acid in the tank is not particularly limited, but the decomposition reaction of the coloring substance progresses as the contact area between the waste acid and ozone gas increases, so that the ozone gas becomes microcolloidal air. Such a blowing method is preferable, and specifically, a method in which a blowing port is provided at the bottom of the tank and a turbine capable of dispersing the blown ozone gas by a mechanically strong shearing force to form a micro-colloidal air is preferable.

The ozone concentration in the ozone gas is in the range of 0.1 to 20% (weight of ozone / volume of gas). Since the minimum amount of ozone added is required for the decomposition or decolorization of coloring substances contained in waste acid, if the ozone concentration is less than 0.1%, the volume of ozone gas added to waste acid becomes too large. Micro-colloidal air is unlikely to be formed, the reaction efficiency between ozone gas and waste acid is reduced, and the decomposition or decolorization of the coloring substance becomes insufficient. On the other hand, there is currently no practical device that can generate ozone gas with an ozone concentration exceeding 20%.

The amount of ozone added to the waste acid is in the range of ozone weight / waste acid volume = 10 to 500 ppm, preferably 10 to 300 ppm, more preferably 10 to 200 ppm. The amount of ozone added
If it is less than 10 ppm, the decomposition and decolorization of the coloring matter are insufficient.
The effect of decomposition and decolorization by ozone reaches a peak at 500 ppm, so it is not necessary to add more than 500 ppm.

Since the attack speed of ozone to the colored substance in the waste acid is extremely fast and the reaction of decomposition and decolorization occurs immediately, the reaction time between the waste acid and ozone may be in the range of 10 seconds to 60 minutes. It is preferably 30 seconds to 30 minutes, more preferably 30 seconds to 10 minutes. If it is less than 10 seconds, the decomposition and decolorization of the colored substance are insufficient.

Although ozone not absorbed by waste acid may be released to the atmosphere as it is, in consideration of the environment and working environment, after decomposing residual ozone into oxygen through an ozone decomposing device, it is released to the atmosphere. May be released. It is desirable that there is no residual ozone in the waste acid after decomposition and decolorization of the coloring substance. If ozone remains in the waste acid, residual ozone leaks into the air during storage of the ozone-treated waste acid or transfer of the waste acid to the pulp cellulose hydrolysis reaction tank, which worsens the indoor working environment. There is concern about the situation.

A method for producing a cellulose powder or a crystalline cellulose powder, which is a second invention, wherein the waste acid regenerated by the above method is used in a hydrolysis reaction of pulp cellulose will be described. The pulp cellulose raw material that can be used in the present invention is bleached virgin pulp such as softwood pulp and hardwood pulp. The pulp may be used in the present invention in a fluid state or sheet form. When using liquid pulp from the pulp bleaching process as the raw material, it is necessary to increase the concentration before adding it to the hydrolysis reaction tank, it is concentrated with a dehydrator such as a screw press or belt filter, and a predetermined amount is added to the reaction tank. To be done. When a dry sheet of pulp is used as a raw material, the pulp is disintegrated by a crusher such as a roll crusher and then put into a reaction tank.

Since a part of the acid is consumed in the hydrolysis reaction of pulp cellulose and the acid is further attached to the pulp hydrolyzate and flows to the next step, the acid concentration of the recycled waste acid is lower than the acid concentration before the reaction. is doing. There are various grades of cellulose powder or crystalline cellulose powder to be produced, and the degree of hydrolysis is different for each grade. As one method of adjusting the degree of hydrolysis, the acid concentration charged into the reaction vessel may be changed for each product grade. Therefore, when the acid concentration during the reaction is the same as or lower than the recycled waste acid concentration, the recycled waste acid itself or the recycled waste acid is diluted before use. When the acid concentration at the time of reaction is higher than the recycled waste acid concentration, a new mineral acid is added to the recycled waste acid to adjust the concentration to a predetermined value, and the recycled waste acid is charged into the reaction tank.

The hydrolysis of pulp cellulose can be carried out under known reaction conditions. Specifically, the pulp concentration is 3 to 10% solids by weight, the acid concentration is 5 to 30% by weight, and the reaction time is 30 minutes to 3%.
Time, reaction temperature is 80-100 ℃.

After completion of the hydrolysis reaction of pulp cellulose,
In the dehydration step, solid-liquid separation is made into pulp cellulose hydrolyzate and waste acid. After washing the pulp cellulose hydrolyzate,
It is neutralized by adding an alkaline agent, dried by a dryer, mechanically ground by a grinder, and classified to obtain a product having a predetermined average particle size. The waste acid is stored in a tank and sent to a regeneration treatment process by adding ozone.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present application is not limited to the examples. The test method and the method for measuring the quality of cellulose powder and crystalline cellulose powder in the examples are shown below. COD measurement of waste acid: According to JIS K0101, COD by potassium permanganate at 100 ° C was measured. Chromaticity measurement method of waste acid: The chromaticity was measured by a colorimetric tube according to JIS K0101. Product whiteness test method: According to JIS P8123, the whiteness was measured using a Hunter whiteness meter. Waste acid after hydrolysis of pulp cellulose (collected at Yufutsu Mill of Nippon Paper Industries Co., Ltd.) was used. COD is 3,900ppm, chromaticity is 47
It was 2 ppm. The original mineral acid is sulfuric acid. Sulfuric acid concentration is 11.2
It was weight%.

[0023]

[Example 1] AT type ozone generator using PSA oxygen as a raw material
(Ozonia, Chlorine Engineers)
A 7.0% concentration of ozone gas was added to the waste acid. The ozone gas was blown from the bottom of the container containing the waste acid, and at the same time, the turbine gas was vigorously stirred to make the ozone gas into micro-coidal air. Reaction time is 10 minutes. The amount of ozone added was adjusted by adjusting the flow rate of ozone gas blown. The amount of ozone added was 25, 50, 100, 200, 500 ppm. The results of COD of waste acid are shown in Table 1 and FIG. 1, and the results of the chromaticity of waste acid are shown in Table 2 and FIG.

[0024]

[Table 1]

[0025]

[Figure 1]

[0026]

[Table 2]

[0027]

[Fig. 2]

From the results of Tables 1 and 2 and FIGS. 1 and 2, it is understood that COD and chromaticity of waste acid can be removed by adding ozone. COD
Although the degree of decrease in chromaticity is greater than the extent of decrease, this is due to ozone decomposing the colored structure part of the coloring component in waste acid, resulting in a decrease in chromaticity, but this decomposition product is still the molecular structure measured as COD. This is probably because the condition is maintained.

[0029]

Example 2 The ozone gas of Example 1 was bleached with ozone at a concentration of 7.0% generated by an AT type ozone generator (Ozonia Co., Ltd., Chlorine Engineers Co., Ltd.) using PSA oxygen as a raw material to produce ozone with a medium concentration. The waste acid was treated in the same manner as in Example 1 except that the ozone exhaust gas discharged later was replaced. The composition of this ozone exhaust gas is shown in Table 3. The chromaticity results are shown in Table 4 and FIG.

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Figure 3]

From the results of Table 4 and FIG. 3, Example 1 was also applied to the ozone exhaust gas discharged from the ozone bleaching stage of the pulp bleaching process.
It can be seen that the chromaticity of waste acid can be removed in the same manner as in.

[0034]

Example 3 Waste sulfuric acid regenerated with an ozone addition amount of 25 ppm in Example 1 was supplemented with fresh sulfuric acid to adjust the sulfuric acid concentration to 12.0%. The acid hydrolyzed the pulp. A predetermined amount of the recycled waste acid after the concentration adjustment was put into a reaction tank, and the hardwood dry sheet pulp disintegrated by a crusher was put into the reaction tank and reacted under the following conditions. Acid concentration: 12% by weight, pulp concentration: 5% by weight of solid content, temperature: 95 ° C, reaction time: 80 minutes. After the reaction,
Solid-liquid separation was performed with a filter, and sodium hydroxide was added to the separated hydrolyzate to neutralize it. Then, it was dried with a dryer and mechanically pulverized with a pulverizer, and finally coarse particles were removed with a classifier to obtain a product. This whiteness was measured. The results are shown in Example 3 of Table 5.

[0035]

[Comparative Example 1] The whiteness of the product was measured in the same manner as in Example 3 except that only fresh sulfuric acid was used as the acid for hydrolysis. The results are shown in Comparative Example 1 in Table 5.

[0036]

[Comparative Example 2] The whiteness of the product was measured in the same manner as in Example 3 except that only waste acid that had not been treated with ozone was used as the acid for hydrolysis. The results are shown in Comparative Example 2 in Table 5.

[0037]

[Table 5]

From the results shown in Table 5, the whiteness of the product manufactured by using the waste acid regenerated by decomposing and decolorizing the coloring matter by ozone treatment of the waste acid is the same as the whiteness of the product manufactured only with fresh sulfuric acid. It is equivalent, and it can be seen that the regenerated waste acid can produce a high-whiteness cellulose powder or crystalline cellulose powder.

[0039]

INDUSTRIAL APPLICABILITY In the step of hydrolyzing pulp cellulose with a mineral acid to produce cellulose powder or crystalline cellulose powder, ozone generated in the ozone generator in waste acid after the hydrolysis reaction or ozone bleaching step of pulp bleaching step It can be regenerated by adding ozone exhaust gas discharged from The regenerated waste acid can be used alone or a new mineral acid can be added thereto to hydrolyze pulp cellulose.

[Procedure amendment]

[Submission date] June 18, 2002 (2002.6.1)
8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

[0037]

[Table 5]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsugu Nishi             143 Yufutsu, Tomakomai City, Hokkaido Nippon Paper Co., Ltd.             Inside the company Yufutsu factory (72) One inventor, Hara             143 Yufutsu, Tomakomai City, Hokkaido Nippon Paper Co., Ltd.             Inside the company Yufutsu factory F-term (reference) 4C090 AA06 BA21 BB36 BB52 CA31                       DA28 DA31                 4L055 AD08 BB18 CB47 FA20 FA22

Claims (3)

[Claims] 1. A process for producing waste powder after hydrolysis reaction by adding ozone to waste acid after hydrolysis reaction in the step of producing pulp powder or crystalline cellulose powder by hydrolyzing pulp cellulose with mineral acid. How to play. 2. The method for recycling waste acid according to claim 1, wherein the ozone added to the waste acid is ozone exhaust gas discharged from the ozone bleaching stage of the pulp bleaching step. 3. In the step of hydrolyzing pulp cellulose with a mineral acid to produce a cellulose powder or crystalline cellulose powder, waste acid after the hydrolysis reaction is ozone or ozone exhaust gas discharged from the ozone bleaching stage of the pulp bleaching step. A method for producing a cellulose powder or a crystalline cellulose powder, characterized in that the waste acid regenerated by adding the above is used in the hydrolysis reaction of pulp cellulose.