JPS6025558B2 - Processing method for alkaline pulp waste liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering an alkaline cooking chemical from the waste liquid after cooking and recovering anthraquinone or its derivative as a single substance during alkaline pulping using a cooking chemical containing anthraquinone or its derivative. It is something.

In recent years, much research has been conducted on adding anthraquinone or its derivatives (hereinafter collectively referred to as anthraquinone) to cooking chemicals to turn fibrous raw materials such as wood chips into pulp. solution,
It is known that adding a small amount of anthraquinone to an alkaline cooking process such as an oxygen-alkali cooking process is effective in terms of both improving pulp yield and promoting delignification. In this case, the amount of anthraquinone added is described as 0.001 to 10.0% by weight based on the cellulose material in the case of alkaline cooking of cellulose materials such as wood chips, for example, according to Japanese Patent Application Laid-Open No. 52-37803. has been
As the amount added increases, the effect of addition also improves.

Generally, anthraquinone is a synthetic organic compound starting from petroleum or coal, and conventionally most of it has been used as an intermediate for dyes.

Therefore, it is a relatively expensive chemical to be used as an agent for pulp production, and unless anthraquinone is recovered and reused, the amount of anthraquinone added will be subject to severe limitations. On the other hand, in general, to recover alkaline cooking chemicals from alkaline pulp waste liquid, a reduction type recovery furnace commonly used in the kraft steaming process is widely used.

In other words, alkaline pulp waste liquid usually has a solids concentration of 50~
After being concentrated to 65% by weight, it is introduced into a recovery furnace and burned at a temperature of 600 qo or more in the presence of oxygen to produce smelt, which is an inorganic melt. During this combustion, all organic substances in the waste liquid are decomposed into carbon dioxide gas and water, so when such conventional recovery methods are applied to alkaline pulp waste liquid containing anthraquinone, the organic compound anthraquinone is decomposed. It is impossible to recover it once it has been lost. Therefore, an object of the present invention is to provide a method for treating alkaline pulp waste liquid, which can recover alkaline cooking chemicals from anthraquinone-containing alkaline pulp waste liquid, and can also effectively and easily recover anthraquinones. It has been done.

That is, the method for treating alkaline pulp waste liquid according to the present invention involves concentrating an alkaline pulp waste liquid containing anthraquine or its derivatives, heating the obtained concentrated waste liquid to solidify it, and increasing the atmospheric temperature from i50qC during this solidification process. 4
Anthraquinone or its derivatives contained in the Tachibana collection gas is recovered by collecting and cooling the gas of volatile substances present between 0000 and 600°C. It is characterized by recovering alkaline cooking chemicals by burning and melting them at a temperature above.

In carrying out the present invention, anthraquinone-containing alkaline pulp waste liquid is first concentrated to a solids concentration of 50 to 65% by weight using a vacuum evaporator.

Next, this concentrated waste liquid is heated indirectly or directly in the presence of air within a temperature range in which most of the organic matter does not self-combust and the anthraquinone gasifies. As a result, only the anthraquinone can be gasified and separated before the combustion of the organic matter derived from the cellulosic substance progresses.
The gasification temperature of anthraquinone varies slightly depending on before and after the pulping reaction, and also varies depending on the gasification speed, pressure, etc., but it is usually between 15 and 0 to 4.
Gasification is completed up to 00°C.

Recovery of anthraquinone can thus be easily carried out by utilizing the sublimation property of anthraquinone. That is, since anthraquinone sublimes within the above temperature range and becomes a gaseous substance, anthraquinone can be solidified with high purity by cooling the once collected gaseous substance to 100 qo or less. Therefore, when a gaseous substance containing anthraquinone is passed through an indirectly water-cooled cooling tower, the anthraquinone will stick to the water-cooled wall, and the stuck anthraquinone can be removed from the system by scraping it off. In addition, gaseous substances containing anthraquinone are passed through a wet washing device such as a cyclone scrubber or a venturi scrubber, and washed with water or an aqueous solution such as steamed sea bream chemical to solidify only the anthraquinone and incorporate it into the aqueous solution. Anthraquinone can also be separated and recovered from other gaseous substances. After heating and solidifying the concentrated waste liquid as described above, the solidified product is further
It is burned at a temperature of 000 to 1100 qo to produce smelt, which is an inorganic melt.

To recover alkaline cooking chemicals from this smelt, conventional recovery methods can be used.
For example, the lime method, which is commonly used in the chemical recovery process in the soda steaming method and the kraft cooking method, can be applied as is to the present invention. As described above, in the conventional method of concentrating alkaline pulp waste liquid and then burning it to recover alkaline steamed chemicals, the present invention involves concentrating in an atmosphere at a temperature of 150°C to 400°C between the concentration step and the combustion step. Since it is only necessary to provide a step to solidify the waste liquid and it does not affect the cooking process in any way, it is suitable for not only kraft cooking, soda cooking, oxygen-alkali cooking, but also neutral sulfite cooking. It can be used to treat alkaline pulp waste liquid discharged in all steaming methods such as semi-chemical pulping methods.

However, especially when the present invention is used to treat soda cooking waste liquid, its effects become even greater.

That is, according to the above-mentioned Japanese Patent Application Laid-Open No. 52-37803, when 0.25% by weight or more of anthraquinone is added during the soda cracking of wood chips, the delignification rate and pulp yield are comparable to or better than kraft cooking. Better results are being obtained. This means that a cooking method that does not contain sulfur compounds as a source of bad odors can be achieved by the soda-digestion method in which anthraquinone is added as an auxiliary agent. Establishment of effective soda recovery methods and anthraquinone recovery and reuse methods is an essential condition for this to be implemented. Therefore, if the present invention is adopted in the waste liquid treatment process of this soda scale method in which anthraquinone is added as an auxiliary agent, anthraquinone and soda can be effectively recovered and reused. Soda cooking method can be implemented. In this case, even more effective soda recovery can be achieved by employing the method described in Samurai Publication No. 51-12724, which was proposed by Honde Tsuzuri as a soda recovery method.

In other words, this soda recovery method involves concentrating the waste liquid from soda evaporation, adding ferric oxide to it, burning it and melting it, and then pouring the resulting molten product into water to recover caustic soda directly as an extruded aqueous solution with high purity and high efficiency. At the same time, the ferric oxide obtained as the extraction residue will be recycled and reused. Therefore, in order to apply this soda recovery method to the present invention, after concentrating the soda cooking waste containing anthraquinone, ferric oxide is added, and this is heated to solidify, and during this solidification process, the ambient temperature is raised to 150°C. Gases of volatile substances existing between 40 and 0 are collected and cooled, while the solidified material obtained in the solidification step is further combusted at 700 and 90 and 0.
When the melt is poured into water, an aqueous solution of caustic soda is obtained as an extract. This makes it possible to recover anthraquinone as a single substance and to recover caustic soda directly without the causticization process. In order to heat and aggregate the waste liquid concentrate and further combust it according to the present invention, a Baijo furnace which has been conventionally used in the soda recovery process can be used. , a fixed culture furnace can be preferably used. These culture furnaces can create a temperature gradient within the furnace, so
Solidification area in the temperature range of 150o~400o and 60o
It is possible to separately provide more than 10 combustion zones within the furnace. The present invention will be explained below with reference to Examples.

Example 1 Five volumes of New Zealand pine chips 5009 were sealed in an autoclave, and 1% by weight of the chips was added using caustic soda as sodium oxide, and 5% by weight of anthraquinone powder was added to the chips at a liquid ratio of 1:5 and the maximum temperature. The pieces were cooked under conditions of 17 pi○, maximum temperature attainment time of 9, and maximum temperature holding time of 60 minutes.

After the milling, the waste liquid adhering to the original pulp was removed by centrifugation, and then the original pulp was washed using about 1 hour of hot water. The yield of selected pulp taken at this time was 50.8%.
The screen lees yield was 0.3% and the KAPPA value was 31.8. Subsequently, the centrifuged waste liquid and the refined waste liquid were mixed (approximately 3.4 times), one of which was collected and vacuum evaporated at a temperature of 70°C to concentrate it to a solid concentration of 65%.

A part of the concentrated waste liquid was dried to absolute dryness at 100°C, then pulverized, ferric oxide was added at a molar ratio of 1.2 to the sodium oxide contained in this dry sample, and the mixture was thoroughly mixed. I collected the water and put it into an electric furnace. The heating rate in the electric furnace was 5° C./min, and the sample was left at a maximum temperature of 900° C. for 3 minutes. On the other hand, during the sunrise process, the temperature ranged from 150℃ to 40℃.
The gas generated between 0 and 0 was collected and quenched to below 4 psi to precipitate the anthraquinone contained in the gas as crystals. The obtained anthraquinone crystals were identified using a gas chromatograph (model GI800-F, model 5, manufactured by Yanagimoto Seisakusho).
%OV-17, ChromosorbW, 80-100
The purity of the anthraquinone obtained was recorded as 99% or more when compared with an anthraquinone reagent (special grade). In addition, the anthraquinone contained in the sample taken before firing in the electric furnace is calculated to be 9 of 375, but the actual weight of the precipitated crystals is 9 of 312, and the recovery rate is 83.2%. Met.

In addition, as a result of repeating the same experiment several times and examining the recovery rate of anthraquinone, 70 to 90% was recorded in all cases.
On the other hand, the molten material obtained by firing was poured into hot water of 95 qC and extracted for 30 minutes to obtain a caustic soda aqueous solution as an extract. The causticization rate at this time was 89.3%. In the above experimental procedure, the concentrated waste liquid was dried to absolute dryness in advance and heated in an electric furnace, but this was done for convenience in order to analyze anthraquinone.
As a practical operation, it is sufficient to heat the concentrated waste liquid to solidify it, and collect in a bottle the gaseous substance containing water vapor generated between 150 qo and 400 qo C during the heating process.
There is no need to heat the pre-dried product.

Example 2 A dried sample of the concentrated waste liquid obtained in the same manner as in Example 1 was analyzed using a thermogravimetric analyzer (Shimadzu TGA-1 without adding ferric oxide).
30M), and thermal decomposition was carried out to a maximum temperature of 100,000 at an overflow rate of 500/min.

Weight reduction from 150qC to 400qC
The amount lost during the period up to oo was 28.2 weight.

On the other hand, the same sample was extracted with dioxane with and without pyrolysis to 400°C, and then subjected to gas chromatography to identify anthraquinone. As a result, 150
It was found that anthraquinone accounted for 20% of the gas generated between oo and 400o.
As is clear from the above description, according to the present invention, conventional alkaline pulp waste liquid is concentrated, and this concentrated liquid is
In the method of recovering alkaline cooking chemicals by burning the concentrated waste liquid at
The anthraquinone contained in the waste liquid can also be efficiently purified by a simple method of heating the concentrated waste liquid at a temperature of ~400q○ to solidify it, and collecting and cooling the gaseous substances generated within this temperature range. It can be easily recovered with high purity.

Therefore, in order to carry out the present invention, it is possible to use culture furnaces that are commonly used for the recovery treatment of conventional alkaline pulp waste liquid. All you have to do is collect things in bottles.

By using the method for treating alkaline valve waste liquid according to the present invention, effective alkaline pulping using anthraquinone as an auxiliary agent becomes practical from an industrial and economic standpoint.

Claims (1)

[Claims] 1. Concentrate the alkaline pulp waste liquid containing anthraquinone or its derivatives, heat the obtained concentrated waste liquid to solidify it, and in the process of solidification, the atmospheric temperature rises from 150°C to 4.
The anthraquinone or its derivative contained in the collected gas is collected by collecting the gas of volatile substances existing between 00°C and cooling it, and the solidified product obtained in the solidification step is Furthermore, it burns at a temperature of over 600℃,
A method for treating alkaline pulp waste liquid, characterized by recovering an alkaline cooking chemical by melting it. 2 After adding ferric oxide to the concentrated waste liquid, it was heated to solidify it, then burned and melted, and the resulting molten product was poured into water to directly recover caustic soda as an aqueous extraction solution, and the resulting mixture was obtained as an extraction residue. 2. A method for treating alkaline pulp waste liquid according to claim 1, wherein ferric oxide is recycled and reused.