阅读说明：本技术 一种从制浆黑液中提取半纤维素的方法 (Method for extracting hemicellulose from pulping black liquor ) 是由 施晓旦 李赛 赵吉 郑璐 于 2018-09-12 设计创作，主要内容包括：本发明公开了一种从制浆黑液中提取半纤维素的方法,包括如下步骤：将制浆黑液置于分离容器中,用筛网去除不溶解的悬浮物；加入絮凝剂和助凝剂,搅拌后沉降,排放下层细小纤维和泥沙；通过陶瓷滤膜,截留回收并经洗涤干燥后得到高纯半纤维素。本发明从制浆黑液中提取半纤维素,收率最高可达92％,处理的制浆黑液不需有机溶剂参与,不受浓度的影响,可处理的黑液范围较广,效率较高,环保,资源再利用,减少污染,反应过程直观,操作简便,成本低廉。(The invention discloses a method for extracting hemicellulose from pulping black liquor, which comprises the following steps: placing the pulping black liquor in a separation container, and removing insoluble suspended matters by using a screen; adding a flocculating agent and a coagulant aid, stirring, settling, and discharging lower-layer fine fibers and silt; and (4) passing through a ceramic filter membrane, intercepting and recovering, washing and drying to obtain high-purity hemicellulose. The method extracts the hemicellulose from the pulping black liquor, the yield can reach 92 percent, the treated pulping black liquor does not need organic solvent, is not influenced by concentration, has wider range of treatable black liquor, higher efficiency, environmental protection, resource reutilization, pollution reduction, intuitive reaction process, simple and convenient operation and low cost, and is environment-friendly.)

1. The method for extracting hemicellulose from pulping black liquor is characterized by comprising the following steps of:

step one, placing pulping black liquor in a separation container, and removing insoluble suspended matters by using a screen;

step two, adding a flocculating agent and a coagulant aid, stirring, settling, and discharging lower-layer fine fibers and silt;

and step three, passing the obtained upper layer solution through a ceramic filter membrane, intercepting and recovering, washing and drying to obtain high-purity hemicellulose.

2. The method of claim 1, wherein the pulping black liquor comprises wood pulping black liquor and herbaceous pulping black liquor, the solid content is 5-55 wt%, and the pH is 8.0-14.0.

3. The method of claim 1, wherein the mesh has a mesh size of 50 to 500 mesh.

4. The method of claim 1, wherein the flocculating agent is selected from at least one of sodium polyacrylate, cationic polyacrylamide, anionic polyacrylamide, nonionic polyacrylamide, polyacrylamide derivatives, acrylamide.

5. The method according to claim 4, characterized in that the flocculant is added in an amount of 0.01-1g per 1kg of pulping black liquor by mass.

6. The method of claim 1, wherein the coagulant aid is selected from at least one of polyaluminum chloride, polyferric chloride, and polyaluminum ferric chloride.

7. The method according to claim 6, wherein the coagulant aid is added in an amount of 0.01-1g per 1kg of the black pulping liquor by mass.

8. The method of claim 1, wherein the flocculant is a cationic polyacrylamide or an anionic polyacrylamide and the coagulant aid is polyaluminum chloride.

9. The method as claimed in claim 1, wherein the ceramic filter membrane is 15-25 KD.

10. The method of claim 1, wherein the temperature of the ceramic filter membrane passing in the third step is 60-80 ℃, and the pressure difference of the ceramic filter membrane passing is 2-3 bar.

Technical Field

The invention relates to the field of pulping and papermaking and biomass materials, in particular to a method for efficiently extracting and separating hemicellulose from pulping black liquor.

Background

The paper industry is an important traditional prop industry in China, and meanwhile, the paper industry is also an industry with large consumption of industrial energy and resources and serious pollution in China. According to data of the environmental sector in China in 2007: the water discharge of the paper industry is 31.8 billion cubic meters, which accounts for 18.4 percent of the total water discharge of the national industry; the COD discharge amount is 152.6 ten thousand tons, which accounts for 29.8 percent of the total discharge amount of the whole country. Among them, hemicellulose in black liquor is one of the main factors causing pollution.

On the other hand, hemicellulose can be used as a raw material for many high value-added products. Hemicellulose contains various saccharides including D-xylosyl, D-mannosyl, D-glucosyl, D-galactosyl, L-arabinosyl, 4-O-methyl-D-glucuronyl, D-galacturonyl, D-glucuronyl and the like, and a small amount of L-rhamnose, L-fucose and the like. Therefore, the hemicellulose is separated from the papermaking black liquor, and the alkali liquor is recovered, so that the pollution is eliminated, the waste is changed into valuable, and the social benefit and the economic benefit are very high.

The main extraction methods for extracting hemicellulose at present are a water extraction method and an alcohol analysis method. For example, chinese patent CN1923855A entitled "a method for recovering hemicellulose from pulping black liquor" discloses a method for extracting hemicellulose, which mainly comprises the following steps: mixing plant fiber, alkali and water, putting the mixture into a reaction kettle with a stirring device and a heating system, heating the temperature of the reaction kettle to 35-85 ℃, stirring the mixture for 10S-10 MIN at the rotating speed of 300-2000 RPM, and filtering or centrifuging the mixture by a conventional method to obtain filtrate or supernatant, namely hemicellulose extracting solution; adding 80-95% ethanol with 2-3 times of volume of the hemicellulose into the hemicellulose extracting solution to precipitate soluble hemicellulose, conventionally filtering, collecting a product, and drying to obtain the hemicellulose. In the extraction method of the hemicellulose, a large amount of ethanol needs to be added for sedimentation, so the cost is high, and the method is not suitable for pulping black liquor. Therefore, the research and development of a novel low-cost, high-efficiency and environment-friendly method for extracting and separating hemicellulose from the pulping black liquor has great significance for the whole papermaking industry.

Disclosure of Invention

The invention aims to provide a method for extracting hemicellulose from pulping black liquor, which aims to solve the defects in the background art, improve the resource recycling of the hemicellulose in the pulping black liquor and solve the problems of high pollution and low resource utilization rate of the conventional papermaking black liquor.

The invention is realized by the following technical scheme:

a method for extracting hemicellulose from pulping black liquor comprises the following steps:

step one, placing pulping black liquor in a separation container, and removing insoluble suspended matters by using a screen;

step two, adding a flocculating agent and a coagulant aid, stirring, settling, and discharging lower-layer fine fibers and silt;

and step three, passing the obtained upper layer solution through a ceramic filter membrane, intercepting and recovering, washing and drying to obtain high-purity hemicellulose.

The pulping black liquor comprises various wood pulping black liquors and herbaceous pulping black liquors, and the main components comprise hemicellulose, lignin and alkali liquor. Preferably, the pulping black liquor has a solid content of 5-55 wt% (25 ℃), and a pH of 8.0-14.0.

The screen meshes with different specifications can be selected according to the particle size of insoluble substances in the pulping black liquor. Preferably, the aperture of the screen is 50-500 meshes, and is preferably 200-500 meshes.

The flocculating agent is selected from at least one of sodium polyacrylate, cationic polyacrylamide, anionic polyacrylamide, nonionic polyacrylamide, polyacrylamide derivatives and acrylamide, and preferably cationic polyacrylamide or anionic polyacrylamide.

For the convenience of addition and use, the flocculant can be generally prepared into an aqueous solution with the mass percent concentration of 0.05-5%. The addition amount of the flocculant is 0.01-1g per 1kg of pulping black liquor by mass, and the preferable addition amount is 0.01-0.5 g per kg of pulping black liquor.

The coagulant aid is selected from at least one of polyaluminium chloride, polyferric chloride and polyaluminium ferric chloride, and preferably polyaluminium chloride.

For convenience of addition and use, the coagulant aid can be prepared into an aqueous solution with the mass percentage concentration of 1-5%, and the addition amount is 0.01-1g per 1kg of pulping black liquor by mass, and the preferable addition amount is 0.01-0.5 g per kg of pulping black liquor.

Preferably, the ceramic filter membrane is 15-25 KD.

Further preferably, the temperature of the ceramic filter membrane passing through the step three is 60-80 ℃, preferably 65-75 ℃, and the membrane pressure difference is 2-3 bar.

The hemicellulose intercepted and recovered by the ceramic filter membrane is washed by deionized water for 0-3 times, dried for 3-5h at the temperature of 60-100 ℃ to obtain high-purity hemicellulose, and then the high-purity hemicellulose is placed into a vacuum bag for storage.

The filtrate passed through the ceramic filter membrane is further treated or returned directly to the paper mill.

Compared with the prior art, the method has the following beneficial effects:

1. the hemicellulose is extracted from the pulping black liquor, and the yield is generally over 85 percent and can reach 92 percent at most.

2. The treated black pulping liquor does not need organic solvent, is not influenced by concentration, and has wider range of treatable black pulping liquor and higher efficiency.

3. Environmental protection, resource recycling and pollution reduction.

4. The reaction process is visual, the operation is simple and convenient, and the cost is low.

Detailed Description

The invention is illustrated below by means of specific examples, without being restricted thereto.