阅读说明：本技术 一种特高压变压器用低钠离子含量绝缘纸及其制造方法 (Low-sodium ion content insulating paper for extra-high voltage transformer and manufacturing method thereof ) 是由 刘群华 曹春昱 刘�文 于 2019-04-11 设计创作，主要内容包括：一种特高压变压器用低钠离子含量绝缘纸及其制造方法,先对本色硫酸盐绝缘针叶木浆进行纯化处理,再采用组合打浆工艺进行打浆处理,再采用双圆网纸机通过双层复合抄造成原纸,原纸最后经超级压光而成。采用这样方法制造的绝缘纸钠离子含量低、撕裂度高、电气性能高。(The low-sodium ion content insulating paper for extra-high voltage transformer is produced through purifying unbleached sulfate insulating softwood pulp, pulping with combined pulping process, making paper with double-layer composite paper with double-cylinder paper machine, and final supercalendering. The insulating paper manufactured by the method has low sodium ion content, high tearing strength and high electrical performance.)

1. The low-sodium ion content insulating paper for the extra-high voltage transformer and the manufacturing method thereof are characterized in that: the method comprises the steps of purifying unbleached sulfate insulation softwood pulp, pulping by adopting a combined pulping process, manufacturing base paper by adopting a double-cylinder paper machine through double-layer composite papermaking, and finally performing super calendering on the base paper to obtain the base paper.

2. The insulation paper with low sodium ion content for the extra-high voltage transformer and the manufacturing method thereof as claimed in claim 1, wherein the purification process comprises the steps of firstly adopting acid treatment and then adopting magnesium salt treatment; wherein the acid treatment process comprises the following steps: defibering natural-color sulfate softwood insulation pulp, adjusting the concentration to 3%, carrying out acid treatment on the insulation wood pulp by using 1% hydrochloric acid (for absolute dry insulation wood pulp amount), wherein the treatment time is 30-60min, washing by using 60 ℃ desalted water with the first section of conductivity being less than 5.0 mu S/cm and the pH value being 7.0-7.5, and washing by using normal-temperature deionized water in the second and third sections; wherein the magnesium salt treatment process comprises the following steps: adjusting the concentration of the acid-treated insulating wood pulp to 3%, adding 2.5% magnesium salt (for the amount of absolutely dry insulating wood pulp) for treatment for 30-60min, washing the magnesium salt-treated paper pulp with deionized water for 3-4 periods until the pH of a water extract of the pulp is 6.0-7.0 and the conductivity is less than 3.0 mS/m.

3. The insulation paper with low sodium ion content for the extra-high voltage transformer and the manufacturing method thereof as claimed in claim 1, characterized in that the combined pulping process comprises the following steps: firstly, the purified insulation softwood pulp is mixed and concentrated to 3.5%, a disc refiner is adopted to pulp the pulp to 35-40 DEG SR, then the pulp is concentrated to 5-6%, and the pulp is continuously pulped to 70-75 DEG SR by a groove type stone knife beater to form pulp.

4. The insulation paper with low sodium ion content for the extra-high voltage transformer and the manufacturing method thereof as claimed in claim 1, wherein the meshes of the double cylinder paper machine are 90 meshes, the basis weights of the two layers of paper are the same, and the basis weight of each layer is 32-40g/m²Thickening the pulp on the screen<0.3 percent, and the drying curve adopts a drying mode from low to high to low, and the maximum temperature is not more than 105 ℃; after supercalendering, the thickness of the finished paper is 0.070-0.080mm, and the tightness is 0.90-1.00g/cm³The transverse tearing strength is more than or equal to 530mN, the content of sodium ions in ash is less than or equal to 15mg/kg, and the power frequency breakdown strength is more than or equal to 10.5 kV/mm.

Technical Field

The invention relates to the field of pulping and papermaking, in particular to low-sodium ion content insulating paper for an extra-high voltage transformer and a manufacturing method thereof.

Background

The insulating paper is an important insulating material in the transformer and is wound on the high-voltage winding coil and the low-voltage winding coil. In an oil-immersed transformer, an insulation structure of oil-immersed insulation paper is the most common main insulation, and the reliability of the insulation structure is directly related to the safety and stability of a power grid. Compared with the insulation paper imported from abroad, the difference of the transformer turn-to-turn insulation paper in China mainly shows that the paper has the problems of high sodium ion content, high ash content, low tearing strength and the like. Ash content of domestic insulation paper is generally 0.25%, while ash content of imported insulation paper is generally 0.19%; the sodium ion content of the domestic paper reaches 53.0mg/kg, while the sodium ion content of the imported paper is only 16.1 mg/kg; the transverse tearing strength of the domestic insulation paper is generally 460mN, and the tearing strength of the imported insulation paper is as high as more than 530 mN. If the content of sodium ions in the insulating paper is high, the conductivity of the water extract of the paper is high, the breakdown strength is reduced, the dielectric loss is increased, and the service life of the insulating paper is finally influenced. Insulating paper for transformers of 500kV and 750kV has been developed in China, but insulating paper for transformers of 1000kV or more still depends on import, and key core technologies of the insulating paper for transformers are urgently needed to overcome, such as raw material purification and refining, pulping treatment, raw material formula, structural design and forming and the like. The key technologies have decisive influence on the physical and electrical properties of the insulation paper, so that the influence factors on the electrical properties of the transformer insulation paper need to be deeply researched, the key core technologies are overcome, 1000kv insulation paper is developed, and the localization of the extra-high voltage insulation paper is realized.

Disclosure of Invention

In order to solve the problems, the invention aims to provide the low-sodium ion content insulating paper for the extra-high voltage transformer and the manufacturing method thereof, the process is simple and easy to operate, the product has high chemical purity, low sodium ion content, high tearing strength, excellent dielectric property and uniform structure, and can be produced in a large scale. The specific technical scheme is as follows:

(1) the unbleached sulfate insulation softwood pulp is subjected to acid treatment and magnesium salt treatment, and the washing mode is improved, so that the purity is further improved;

(2) the purified unbleached sulfate insulation softwood pulp adopts a combined pulping process condition, namely a pulping mode combining free pulping and sticky pulping, and a disc mill is used for cutting off to realize free pulping; the groove type stone knife beating machine is used for fully devillicating and brooming pulp fibers to realize sticky beating. The tearing degree of the paper subjected to the combined pulping treatment is higher;

(3) the prepared pulp is made into paper by a double-cylinder combined papermaking mode, so that the paper is uniform and compact in structure and free of holes;

(4) the paper is processed by extra press polish to realize higher tightness.

The acid treatment process of the unbleached sulfate softwood insulation pulp in the step (1) comprises the following steps: defibering the insulation wood pulp, adjusting the concentration of the insulation wood pulp to 3 percent, carrying out acid treatment on the insulation wood pulp by using 1 percent hydrochloric acid (the absolute dry insulation wood pulp amount) for 30-60min, washing the insulation wood pulp by using desalted water with the conductivity of less than 5.0 mu S/cm at 60 ℃ and the pH value of 7.0-7.5 at the first section, and washing the two and the three sections by using normal-temperature deionized water; the magnesium salt treatment process comprises the following steps: adjusting the concentration of the acid-treated insulating wood pulp to 3%, adding 2.5% magnesium salt (for the amount of absolutely dry insulating wood pulp) for treatment for 30-60min, washing the magnesium salt-treated paper pulp with deionized water for 3-4 periods until the pH of a water extract of the pulp is 6-7 and the conductivity is less than 3.0 mS/m.

The combined pulping process of the insulating wood pulp in the step (2) comprises the following steps: firstly, the purified insulation softwood pulp is mixed and concentrated to 3.5%, a disc refiner is adopted to pulp the pulp to 35-40 DEG SR, then the pulp is concentrated to 5-6%, and the pulp is continuously pulped to 70-75 DEG SR by a groove type stone knife refiner to form pulp.

The papermaking process of the insulating paper in the step (3) comprises the following steps: the meshes of the double-cylinder paper machine are both 90 meshes, the basis weights of the two layers of paper are the same, and each layer of paper has the basis weight of 32-40g/m²Thickening the pulp on the screen<0.3 percent, and the drying curve adopts a drying mode from low to high to low, and the maximum temperature is not more than 105 ℃.

The thickness of the low-sodium ion content insulating paper for the extra-high voltage transformer is 0.070-0.080mm, and the tightness is 0.90-1.00g/cm³The transverse tearing degree is more than or equal to 530mN, and the conductivity of the water extract is<1.8mS/m, the content of sodium ions in ash is less than or equal to 15mg/kg, the dielectric loss tangent (tg, 100 ℃) of dry paper is less than or equal to 0.19%, the ash is less than or equal to 0.20%, and the power frequency breakdown strength is more than or equal to 10.5 kV/mm.

The invention emphasizes the purification process of the insulating wood pulp and special pulping process conditions. The purification process is a combination of acid treatment and magnesium salt treatment, and the washing process is improved. The insulation paper for the extra-high voltage transformer generally adopts unbleached sulfate softwood pulp as a raw material, and the ash content of unpurified paper pulp is high. The ash in the pulp is divided into attachment ash, exchange ash and inert ash, the attachment ash content is the largest, the exchange ash content is the smallest, and the inert ash is the most difficult to remove. Most of the ash in the pulp after cooking can be removed by washing and selecting, but about half of the ash remains, and the insulating paper made by the pulp after cooking directly has poor electrical performance. Further purification of the cooked commercial insulation slurry is therefore required. The invention adopts a method combining acid treatment and magnesium salt treatment to purify commercial insulating wood pulp, and mainly improves and innovates the influence of acid dosage and washing process thereof, magnesium salt dosage and washing process thereof on the conductivity and pH value of the pulp water extract, the content change of sodium ions in insulating paper and the electrical property. The special pulping process is a pulping mode combining free state and viscous state. Wherein the free pulping is a pulping mode mainly by transversely cutting off fibers, and is characterized by short pulping time, quick water filtration and loose and porous paper-forming structure; the sticky beating is a beating mode mainly comprising longitudinal fiber splitting and fibrillation, and is characterized by long beating time, compact paper quality and strong physical properties of finished paper. The two are combined together, the pulping time can be shortened, the energy consumption is reduced, and the paper can be compact in structure, uniform in structure and excellent in performance.

Detailed Description

For a further understanding of the invention, preferred embodiments of the invention are described below with reference to the examples.

Embodiment 1 of the present invention:

1) defibering the insulation wood pulp, adjusting the concentration of the insulation wood pulp to 3 percent, carrying out acid treatment on the insulation wood pulp by using 1 percent hydrochloric acid (the absolute dry insulation wood pulp amount) for 30min, washing the insulation wood pulp by using desalted water with the first section of electric conductivity of 4.5 mu S/cm and the pH value of 7.0-7.5 and at 60 ℃, and washing the two and three sections of the insulation wood pulp by using normal-temperature deionized water; then magnesium salt treatment is carried out: adjusting the concentration of the acid-treated insulating wood pulp to 3%, adding 2.5% magnesium salt (for the amount of absolutely dry insulating wood pulp) for treatment, wherein the treatment time is 30min, then washing the magnesium salt-treated paper pulp with deionized water for 3 sections until the pH value of a water extract of the pulp is 6.3 and the conductivity is 2.5 mS/m.

2) Adjusting the pulp concentration of the purified insulation softwood pulp to 3.5%, pulping the pulp to 35-degree SR by using a disc refiner, concentrating the pulp to 5%, and continuously pulping to 70-degree SR by using a groove type stone knife refiner to obtain pulp.

3) Making base paper by a double-cylinder paper machine with 90 meshes, wherein the basis weights of two layers of paper are the same and are respectively 32g/m²(ii) a And performing super calendering on the base paper to obtain finished paper.

The processes of the steps 1), 2) and 3) are all carried out by adopting desalted water.

The basis weight of the insulation paper with low sodium ion content for the extra-high voltage transformer prepared in the embodiment is 64g/m²0.070mm in thickness and 0.91g/cm in tightness³The transverse tearability is 546mN, the conductivity of the water extract is 1.7mS/m, the content of sodium ions in ash is 14mg/kg, the dielectric loss tangent (tg, 100 ℃) of dry paper is 0.17%, the ash content is 0.16%, and the power frequency breakdown strength is 11.5 kV/mm.

Embodiment 2 of the present invention:

1) defibering the insulation wood pulp, adjusting the concentration of the insulation wood pulp to 3 percent, carrying out acid treatment on the insulation wood pulp by using 1 percent hydrochloric acid (the absolute dry insulation wood pulp amount) for 45min, washing the insulation wood pulp by using desalted water with the first section of electric conductivity of 4.5 mu S/cm and the pH value of 7.0-7.5 and at 60 ℃, and washing the two and three sections of insulation wood pulp by using normal-temperature deionized water; then magnesium salt treatment is carried out: adjusting the concentration of the acid-treated insulating wood pulp to 3%, adding 2.5% magnesium salt (for absolute dry insulating wood pulp amount) for treatment, wherein the treatment time is 45min, then washing the magnesium salt-treated paper pulp with deionized water for 4 sections until the pH value of a water extract of the pulp is 6.6 and the conductivity is 2.4 mS/m.

2) The purified insulation softwood pulp is subjected to size mixing and concentration to be 3.5%, the pulp is pulped to be 37-degree SR by a disc refiner, the pulp is concentrated to be 5.5%, and the pulp is continuously pulped to be 72-degree SR by a groove type stone knife beater to form pulp.

3) Making base paper with a double cylinder machine with 90 meshes, wherein the basis weights of the two layers of paper are the same and are respectively 36g/m²(ii) a And performing super calendering on the base paper to obtain finished paper.

The processes of the steps 1), 2) and 3) are all carried out by adopting desalted water.

The basis weight of the insulation paper with low sodium ion content for the extra-high voltage transformer prepared in the embodiment is 72g/m²0.075mm in thickness and 0.96g/cm in tightness³The transverse tearability is 575mN, the conductivity of the water extract is 1.5mS/m, the content of sodium ions in ash is 12mg/kg, the dielectric loss tangent (tg, 100 ℃) of dry paper is 0.16%, the ash content is 0.16%, and the power frequency breakdown strength is 12.5 kV/mm.

Embodiment 3 of the present invention:

1) defibering the insulation wood pulp, adjusting the concentration of the insulation wood pulp to 3 percent, carrying out acid treatment on the insulation wood pulp by using 1 percent hydrochloric acid (the absolute dry insulation wood pulp amount) for 60min, washing the insulation wood pulp by using desalted water with the first section of electric conductivity of 4.5 mu S/cm and the pH value of 7.0-7.5 and at 60 ℃, and washing the two and three sections of the insulation wood pulp by using normal-temperature deionized water; then magnesium salt treatment is carried out: adjusting the concentration of the acid-treated insulating wood pulp to 3%, adding 2.5% magnesium salt (for absolute dry insulating wood pulp amount) for treatment, wherein the treatment time is 60min, then washing the magnesium salt-treated paper pulp with 4 sections of deionized water until the pH value of a water extract of the pulp is 6.7 and the conductivity is 2.3 mS/m.

2) The purified insulation softwood pulp is subjected to size mixing and concentration to be 3.5%, a disc mill refiner is adopted to pulp the pulp to be 40-degree SR, then the pulp is concentrated to be 6%, and a groove type stone knife refiner is adopted to continue pulping to be 75-degree SR to obtain pulp.

3) Making base paper by a double-cylinder paper machine with 90 meshes, wherein the basis weights of two layers of paper are the same and are respectively 40g/m²(ii) a And performing super calendering on the base paper to obtain finished paper.

The processes of the steps 1), 2) and 3) are all carried out by adopting desalted water.

The basis weight of the insulation paper with low sodium ion content for the extra-high voltage transformer prepared in the embodiment is 80g/m²0.080mm in thickness and 1.0g/cm in tightness³The transverse tear resistance is 602mN, the conductivity of the water extract is 1.6mS/m, the content of sodium ions in ash is 13mg/kg, the dielectric loss tangent (tg, 100 ℃) of dry paper is 0.16%, the ash content is 0.17%, and the power frequency breakdown strength is 12.0 kV/mm.

The invention provides the low-sodium ion content insulating paper for the extra-high voltage transformer and the manufacturing method thereof. The principles and embodiments of the present invention are described herein using specific examples, which are presented only to assist in understanding the method and core concepts of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall into the protection scope of the claims of the present invention.