阅读说明：本技术 用于分离造纸白水中聚乙烯醇的系统及方法 (System and method for separating polyvinyl alcohol from papermaking white water ) 是由 何占飞 王玥 于 2020-11-24 设计创作，主要内容包括：本发明涉及用于分离造纸白水中聚乙烯醇的系统及方法。该系统包括：第一反应池,构造成接收含有聚乙烯醇的造纸白水和碱性pH调节剂,以对含有聚乙烯醇的造纸白水进行pH调节；第二反应池,连接至第一反应池,且构造成接收经过pH调节的造纸白水和盐析剂,以析出部分聚乙烯醇；第三反应池,连接至第二反应池,且构造成接收经过盐析的造纸白水和絮聚剂,以使析出的聚乙烯醇产生絮聚,形成聚乙烯醇固形物；以及固液分离装置,连接至第三反应池,且构造成对含有聚乙烯醇固形物的造纸白水进行固液分离,从而分离出造纸白水中的聚乙烯醇。本发明能起到以下有益技术效果：能将含有较高浓度聚乙烯醇(100mg/L以上)的造纸白水处理至COD低于50mg/L。(The invention relates to a system and a method for separating polyvinyl alcohol from papermaking white water. The system comprises: a first reaction tank configured to receive the polyvinyl alcohol-containing papermaking white water and an alkaline pH adjuster to perform pH adjustment on the polyvinyl alcohol-containing papermaking white water; a second reaction tank connected to the first reaction tank and configured to receive the pH-adjusted papermaking white water and the salting-out agent to precipitate a part of the polyvinyl alcohol; a third reaction tank connected to the second reaction tank and configured to receive the salted-out papermaking white water and a flocculating agent to flocculate the precipitated polyvinyl alcohol to form polyvinyl alcohol solids; and a solid-liquid separation device connected to the third reaction tank and configured to perform solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solids, thereby separating the polyvinyl alcohol from the papermaking white water. The invention can achieve the following beneficial technical effects: can treat papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.)

1. A system for separating polyvinyl alcohol from papermaking white water, the system comprising:

a first reaction tank configured to receive the polyvinyl alcohol-containing papermaking white water and an alkaline pH adjuster to perform pH adjustment on the polyvinyl alcohol-containing papermaking white water;

a second reaction tank connected to the first reaction tank and configured to receive the pH-adjusted papermaking white water and a salting-out agent to precipitate a part of the polyvinyl alcohol;

a third reaction tank connected to the second reaction tank and configured to receive the salted-out papermaking white water and a flocculating agent to flocculate the precipitated polyvinyl alcohol to form polyvinyl alcohol solids; and

and the solid-liquid separation device is connected to the third reaction tank and is configured to carry out solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solid so as to separate the polyvinyl alcohol in the papermaking white water.

2. The system for separating polyvinyl alcohol from papermaking white water as claimed in claim 1, wherein the system further comprises a concentration device connected before the first reaction tank and configured to concentrate the papermaking white water.

3. The system for separating polyvinyl alcohol from papermaking white water of claim 1, further comprising a press device connected after or disposed within the solid-liquid separation device and configured to press polyvinyl alcohol solids.

4. The system for separating polyvinyl alcohol from papermaking white water according to claim 1, wherein the first reaction tank, the second reaction tank and the third reaction tank are the same reaction tank, and receive the alkaline pH adjusting agent, the salting-out agent and the flocculating agent in this order.

5. The system for separating polyvinyl alcohol from papermaking white water as claimed in claim 1, wherein the alkaline pH adjusting agent is sodium hydroxide, the salting agent is sodium sulfate, and the flocculating agent is borax.

6. A method for separating polyvinyl alcohol from papermaking white water, characterized in that the method comprises the following steps:

conveying the papermaking white water containing polyvinyl alcohol to a first reaction tank, and adding an alkaline pH regulator into the first reaction tank to regulate the pH of the papermaking white water containing polyvinyl alcohol;

conveying the pH-adjusted papermaking white water from the first reaction tank to a second reaction tank, and adding a salting-out agent into the second reaction tank to separate out part of polyvinyl alcohol;

conveying the salted-out papermaking white water from the second reaction tank to a third reaction tank, and adding a flocculating agent into the third reaction tank to flocculate the separated polyvinyl alcohol to form a polyvinyl alcohol solid; and

and carrying out solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solid so as to separate the polyvinyl alcohol from the papermaking white water.

7. The method for separating polyvinyl alcohol from papermaking white water as claimed in claim 6, wherein the method further comprises: the papermaking white water containing polyvinyl alcohol is concentrated before being transferred to the first reaction tank.

8. The method for separating polyvinyl alcohol from papermaking white water as claimed in claim 6, wherein the method further comprises: after solid-liquid separation of the papermaking white water containing the polyvinyl alcohol solid matter, the polyvinyl alcohol solid matter is pressed.

9. The method for separating polyvinyl alcohol from papermaking white water according to claim 6, wherein the first reaction tank, the second reaction tank and the third reaction tank are the same reaction tank, and the alkaline pH adjusting agent, the salting-out agent and the flocculating agent are added in this order.

10. The method of claim 6, wherein the alkaline pH adjusting agent is sodium hydroxide, the salting agent is sodium sulfate, and the flocculating agent is borax.

Technical Field

The invention relates to the technical field of papermaking, in particular to a system and a method for separating polyvinyl alcohol from papermaking white water.

Background

The use of polyvinyl alcohol in papermaking is mainly surface coating, especially for the production of various specialty papers, such as glassine, wrapping paper, etc. The polyvinyl alcohol is returned to the water system of the paper machine via the broke system during the production process. The treatment of paper making white water is usually an aerobic biochemical process, usually a primary sedimentation tank-a balancing tank (pH adjustment) -a denitrification tank (denitrification) -an aeration tank (COD removal) -a secondary sedimentation tank-a disc filter (removal of suspended matter).

When the concentration of the polyvinyl alcohol in the papermaking white water is lower than 100mg/L, the polyvinyl alcohol can be degraded through biochemical treatment, but when the concentration is higher, foam is formed in an aeration tank due to the foamability and the film forming property, the biochemical process can be inhibited after the pollution is wrapped, and meanwhile, the polyvinyl alcohol cannot be settled, so that the COD (chemical oxygen demand) in the papermaking white water exceeds the discharge standard (the discharge standard is that the COD is usually lower than 50 mg/L).

At present, no mature technical scheme for treating papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) until COD is lower than 50mg/L exists in the papermaking industry.

Disclosure of Invention

An object of the present invention is to provide a system for separating polyvinyl alcohol from papermaking white water, which can solve the problems of the prior art and treat papermaking white water containing polyvinyl alcohol at a high concentration (more than 100 mg/L) to a COD of less than 50 mg/L.

The above object of the present invention is achieved by a system for separating polyvinyl alcohol from papermaking white water, comprising:

a first reaction tank configured to receive the polyvinyl alcohol-containing papermaking white water and an alkaline pH adjuster to perform pH adjustment on the polyvinyl alcohol-containing papermaking white water;

a second reaction tank connected to the first reaction tank and configured to receive the pH-adjusted papermaking white water and a salting-out agent to precipitate a part of the polyvinyl alcohol;

a third reaction tank connected to the second reaction tank and configured to receive the salted-out papermaking white water and a flocculating agent to flocculate the precipitated polyvinyl alcohol to form polyvinyl alcohol solids; and

and the solid-liquid separation device is connected to the third reaction tank and is configured to carry out solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solid so as to separate the polyvinyl alcohol in the papermaking white water.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: can treat papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the system further includes a concentration device connected before the first reaction tank and configured to concentrate the paper white water.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: after the concentration of the papermaking white water containing the polyvinyl alcohol, the papermaking white water is more suitable for subsequent treatment, so that the papermaking white water containing the polyvinyl alcohol with higher concentration (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

Preferably, the system further comprises a squeezing device connected after or disposed within the solid-liquid separation device and configured to squeeze the polyvinyl alcohol solids.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the pressed solid polyvinyl alcohol can be conveniently treated as common industrial waste.

Preferably, the first reaction tank, the second reaction tank and the third reaction tank are the same reaction tank, and receive the alkaline pH adjusting agent, the salting-out agent and the flocculating agent in this order.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the simplified system structure can also treat the papermaking white water containing higher concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the alkaline pH regulator is sodium hydroxide, the salting-out agent is sodium sulfate, and the flocculating agent is borax.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: by selecting proper alkaline pH regulator, salting-out agent and flocculating agent, the papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

The above object of the present invention is also achieved by a method for separating polyvinyl alcohol from papermaking white water, comprising the steps of:

conveying the papermaking white water containing polyvinyl alcohol to a first reaction tank, and adding an alkaline pH regulator into the first reaction tank to regulate the pH of the papermaking white water containing polyvinyl alcohol;

conveying the pH-adjusted papermaking white water from the first reaction tank to a second reaction tank, and adding a salting-out agent into the second reaction tank to separate out part of polyvinyl alcohol;

conveying the salted-out papermaking white water from the second reaction tank to a third reaction tank, and adding a flocculating agent into the third reaction tank to flocculate the separated polyvinyl alcohol to form a polyvinyl alcohol solid; and

and carrying out solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solid so as to separate the polyvinyl alcohol from the papermaking white water.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: can treat papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the method further comprises: the papermaking white water containing polyvinyl alcohol is concentrated before being transferred to the first reaction tank.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: after the concentration of the papermaking white water containing the polyvinyl alcohol, the papermaking white water is more suitable for subsequent treatment, so that the papermaking white water containing the polyvinyl alcohol with higher concentration (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

Preferably, the method further comprises: after solid-liquid separation of the papermaking white water containing the polyvinyl alcohol solid matter, the polyvinyl alcohol solid matter is pressed.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the pressed solid polyvinyl alcohol can be conveniently treated as common industrial waste.

Preferably, the first reaction tank, the second reaction tank and the third reaction tank are the same reaction tank, and the alkaline pH adjuster, the salting-out agent and the flocculating agent are added in this order.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the simplified system structure can also treat the papermaking white water containing higher concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the alkaline pH regulator is sodium hydroxide, the salting-out agent is sodium sulfate, and the flocculating agent is borax.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: by selecting proper alkaline pH regulator, salting-out agent and flocculating agent, the papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

Drawings

Fig. 1 is a schematic diagram of the composition of a system for separating polyvinyl alcohol from papermaking white water according to one embodiment of the present invention.

List of reference numerals

101: a first reaction tank;

102: a second reaction tank;

103: a third reaction tank;

104: a solid-liquid separation device.

Detailed Description

While specific embodiments of the invention will be described below, it should be noted that in the course of the detailed description of these embodiments, in order to provide a concise and concise description, all features of an actual implementation may not be described in detail. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions are made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be further appreciated that such a development effort might be complex and tedious, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, and thus should not be construed as a complete understanding of this disclosure.

Unless otherwise defined, technical or scientific terms used in the claims and the specification should have the ordinary meaning as understood by those of ordinary skill in the art to which the invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "a" or "an," and the like, do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalent, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, nor are they restricted to direct or indirect connections.

Fig. 1 is a schematic diagram of the composition of a system for separating polyvinyl alcohol from papermaking white water according to one embodiment of the present invention.

As shown in fig. 1, a system for separating polyvinyl alcohol from papermaking white water according to an embodiment of the present invention includes:

a first reaction tank 101, the first reaction tank 101 configured to receive the papermaking white water containing polyvinyl alcohol and an alkaline pH adjuster to perform pH adjustment on the papermaking white water containing polyvinyl alcohol;

a second reaction tank 102, the second reaction tank 102 being connected to the first reaction tank 101 and configured to receive the pH-adjusted papermaking white water and the salting-out agent to precipitate a part of the polyvinyl alcohol;

a third reaction tank 103, the third reaction tank 103 being connected to the second reaction tank 102 and configured to receive the salted-out papermaking white water and a flocculating agent to flocculate the precipitated polyvinyl alcohol to form polyvinyl alcohol solids; and

a solid-liquid separation device 104, the solid-liquid separation device 104 is connected to the third reaction tank 103, and is configured to perform solid-liquid separation on the papermaking white water containing the polyvinyl alcohol solids, thereby separating the polyvinyl alcohol in the papermaking white water.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: can treat the papermaking white water containing higher concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50mg/L (meeting the discharge standard).

Specifically, the system for separating polyvinyl alcohol in papermaking white water can treat the papermaking white water containing high-concentration polyvinyl alcohol (more than 100mg/L, for example, more than 100-10000 mg/L), effectively separate part of the polyvinyl alcohol, and form solid polyvinyl alcohol to be discarded (or recycled for industrial process), so that the concentration of the polyvinyl alcohol in the treated papermaking white water is lower than 100mg/L, and the COD (chemical oxygen demand) is ensured to be lower than 50mg/L (meeting the discharge standard).

Preferably, the system further includes a concentration device connected before the first reaction tank 101 and configured to concentrate the paper white water.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: after the concentration of the papermaking white water containing the polyvinyl alcohol, the papermaking white water is more suitable for subsequent treatment, so that the papermaking white water containing the polyvinyl alcohol with higher concentration (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

Preferably, the concentration device is a tubular membrane filtration concentration device, and the concentration of the polyvinyl alcohol in the papermaking white water is concentrated to 5000-10000 mg/L. Preferably, the concentration device is made of a material which has strong pollution resistance and is easy to clean and meets the requirement that the retention rate of polyvinyl alcohol is higher than 75%. Preferably, the concentration device is a multi-stage concentration device. More preferably, the concentration device is a two-stage concentration device.

Of course, it will be understood by those skilled in the art based on the present disclosure that the concentration device is not limited to a tubular membrane filtration concentration device, and other types of concentration devices can be used as long as the concentration requirement is satisfied without departing from the scope of the present invention.

Preferably, the amount of the alkaline pH adjuster is controlled so that the pH in the first reaction tank 101 is maintained at 8.5 to 10.

Preferably, the conveyance of the paper making white water from the first reaction tank 101 to the second reaction tank 102 and from the second reaction tank 102 to the third reaction tank 103 may be an overflow type.

Preferably, the salting-out agent is added in an amount of 0.6 to 1.0 mass% with respect to the polyvinyl alcohol content. More preferably, the salting-out agent is added in an amount of 0.8% (by mass, relative to the polyvinyl alcohol content).

Preferably, the residence time of the paper making white water in the second reaction tank 102 is 15 to 30 minutes.

Preferably, the flocculating agent is added in an amount of 0.2 to 0.5 mass% relative to the polyvinyl alcohol content. More preferably, the flocculating agent is added in an amount of 0.35% (mass% relative to the polyvinyl alcohol content).

Preferably, the mass ratio of the addition amount of the salting-out agent to the addition amount of the flocculating agent is 2.0: 1-2.6: 1. more preferably, the mass ratio of the addition amount of the salting-out agent to the addition amount of the flocculating agent is 2.3: 1.

preferably, the residence time of the paper making white water in the third reaction tank 103 is 15 to 30 minutes.

Preferably, the first reaction tank 101, the second reaction tank 102 and/or the third reaction tank 103 are heated.

Preferably, the system further comprises a pressing device connected after the solid-liquid separation device 104 or disposed within the solid-liquid separation device 104 and configured to press the polyvinyl alcohol solids.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the pressed solid polyvinyl alcohol can be conveniently treated as common industrial waste.

Preferably, the solids of the polyvinyl alcohol after pressing are 10-20% dry.

Preferably, the first reaction tank 101, the second reaction tank 102 and the third reaction tank 103 are the same reaction tank, and receive the alkaline pH adjuster, the salting-out agent and the flocculating agent in this order.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the simplified system structure can also treat the papermaking white water containing higher concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the alkaline pH adjusting agent is sodium hydroxide, the salting-out agent is sodium sulfate, and the flocculating agent is borax.

According to the technical scheme, the system for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: by selecting proper alkaline pH regulator, salting-out agent and flocculating agent, the papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

The method for separating polyvinyl alcohol from papermaking white water according to one embodiment of the present invention comprises the steps of:

conveying the papermaking white water containing polyvinyl alcohol to a first reaction tank 101, and adding an alkaline pH regulator into the first reaction tank 101 to regulate the pH of the papermaking white water containing polyvinyl alcohol;

conveying the pH-adjusted papermaking white water from the first reaction tank 101 to the second reaction tank 102, and adding a salting-out agent to the second reaction tank 102 to precipitate a part of polyvinyl alcohol;

conveying the salted-out papermaking white water from the second reaction tank 102 to the third reaction tank 103, and adding a flocculating agent into the third reaction tank 103 to flocculate the precipitated polyvinyl alcohol to form a polyvinyl alcohol solid; and

the papermaking white water containing the polyvinyl alcohol solids is subjected to solid-liquid separation (for example, using a solid-liquid separator 104) to separate the polyvinyl alcohol from the papermaking white water.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: can treat papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the method for separating polyvinyl alcohol from papermaking white water according to an embodiment of the present invention further comprises: the papermaking white water containing polyvinyl alcohol is concentrated before being transferred to the first reaction tank 101.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: after the concentration of the papermaking white water containing the polyvinyl alcohol, the papermaking white water is more suitable for subsequent treatment, so that the papermaking white water containing the polyvinyl alcohol with higher concentration (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

Preferably, the method for separating polyvinyl alcohol from papermaking white water according to an embodiment of the present invention further comprises: after solid-liquid separation of the papermaking white water containing the polyvinyl alcohol solid matter, the polyvinyl alcohol solid matter is pressed.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the pressed solid polyvinyl alcohol can be conveniently treated as common industrial waste.

Preferably, the first reaction tank 101, the second reaction tank 102 and the third reaction tank 103 are the same reaction tank, and the alkaline pH adjuster, the salting-out agent and the flocculating agent are sequentially added.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: the simplified system structure can also treat the papermaking white water containing higher concentration polyvinyl alcohol (more than 100 mg/L) until the COD is lower than 50 mg/L.

Preferably, the alkaline pH adjusting agent is sodium hydroxide, the salting-out agent is sodium sulfate, and the flocculating agent is borax.

According to the technical scheme, the method for separating the polyvinyl alcohol from the papermaking white water has the following beneficial technical effects: by selecting proper alkaline pH regulator, salting-out agent and flocculating agent, the papermaking white water containing high-concentration polyvinyl alcohol (more than 100 mg/L) can be better treated until the COD is lower than 50 mg/L.

The inventor has performed three experiments on the papermaking white water containing different concentrations of polyvinyl alcohol by using the system and method for separating polyvinyl alcohol from the papermaking white water according to the present invention. In the three experiments, the concentration of polyvinyl alcohol only in water is different, the other experimental parameters are basically the same, the pH value in the first reaction tank 101 is adjusted to 9.0, the addition amount of the salting-out agent is 0.8%, the retention time of the paper making white water in the second reaction tank 102 is 30 minutes, the addition amount of the flocculating agent is 0.35%, the retention time of the paper making white water in the third reaction tank 103 is 30 minutes, the alkaline pH adjusting agent adopts sodium hydroxide, the salting-out agent adopts sodium sulfate, and the flocculating agent adopts borax.

The results of the experiment are shown in table 1.

TABLE 1

From the above experimental results, it can be seen that the system and method for separating polyvinyl alcohol in papermaking white water according to the present invention can treat papermaking white water containing high concentration of polyvinyl alcohol (above 100 mg/L) so that the concentration of polyvinyl alcohol in the treated papermaking white water (i.e., the concentration of polyvinyl alcohol in the effluent) is less than 100mg/L, and ensure that COD is less than 50mg/L (meeting discharge standards).

While particular embodiments of the present invention have been described above, it will be understood by those skilled in the art that they are not intended to limit the invention, and that various modifications may be made by those skilled in the art based on the above disclosure without departing from the scope of the invention.