Liaoning Xinda Talc Group Co., Ltd. — Cao Xinyu. 

The energy consumption of papermaking pulping accounts for 30% to 40% of the total energy consumption in the industry. High energy consumption has always been the core pain point for cost reduction and efficiency improvement in this sector! As a commonly used filler in papermaking, talc powder not only improves the performance of paper but also can reduce the energy consumption of pulping through its unique properties? Based on the research and practice of Xinda Talc Group, this article will fully explain the underlying logic of energy-saving in talc powder pulping. 

Abstract

The paper-making industry, as an important foundation industry of the national economy, faces challenges such as high energy consumption and strict cost control in its production process. Fillers, as an important component in the paper-making formula, have traditionally focused more on their improvement of paper's optical properties and printing adaptability, while paying insufficient attention to their hidden role in the core process of pulping and papermaking - the grinding process. Based on the research and practice of Liaoning Xinda Gypsum Group Co., Ltd., this paper deeply explores how the physical and chemical properties of gypsum powder affect the energy consumption of the grinding process and reveals its potential mechanism in reducing power consumption during the grinding process. The research shows that the flake structure, appropriate hardness, and surface properties of high-quality gypsum powder can significantly reduce the energy consumption of the grinding process by optimizing the friction between fibers, reducing ineffective shearing, and protecting the integrity of fibers. Xinda Gypsum Group verified the application value of gypsum powder as an "energy-saving filler" in the paper-making system through raw material selection, modification technology, and process adaptability research, providing new ideas and practical paths for the paper-making industry to reduce costs and increase efficiency. 

Key words

Talc powder; Papermaking; Pulping; Power consumption of grinding; Energy conservation and cost reduction; Liaoning Xinda Talc Group 

I. Introduction 

The papermaking industry is a high-energy-consuming sector. Among them, the pulping process is one of the most energy-intensive unit operations in the pulp and paper production process, accounting for approximately 30% to 40% of the total energy consumption of the entire pulp and paper production process [1]. The main purpose of pulping is to disintegrate and refine the fibers through mechanical action, increase the specific surface area of the fibers, and enhance the bonding force between the fibers, thereby improving the strength performance of the paper. However, the traditional pulping process often involves significant energy waste, mainly manifested as excessive fiber cutting, ineffective shearing, and energy loss due to equipment wear. Therefore, how to effectively reduce the energy consumption of pulping without affecting the quality of the paper sheet has always been a key issue in the technical research of the papermaking industry. 

Fillers are the solid substances added to papermaking ingredients in the largest quantity apart from fibers. They usually account for 10% to 30% of the dry weight of the paper slurry (the weight of the paper slurry after complete drying and without moisture). Their main function is to fill the gaps between fibers, improving the opacity, whiteness, and smoothness of the paper, and reducing production costs [2]. For a long time, talcum powder has been widely used in cultural paper, packaging paper, and household paper due to its low price, high whiteness, stable chemical properties, and strong covering power. However, regarding the role of talcum powder in the pulping process, existing research mostly focuses on its influence on the final performance of the paper, such as strength, bulk, and printing suitability, while there are relatively few systematic studies and reports on its "invisible" regulatory effect in the front-end process of pulping, especially regarding the "hidden" energy consumption control of pulping. 

Liaoning Xinda Calcite Group Co., Ltd. (hereinafter referred to as "Xinda Calcite Group") is a leading supplier of calcite products in China, and has been dedicated to the development of application technologies for calcite powder in the papermaking industry for a long time. In recent years, the company, leveraging its own resource advantages and technical accumulation, has conducted a series of experimental studies and application explorations on the correlation between the characteristics of calcite powder and the energy consumption of pulping. This article aims to, based on the research results of Xinda Calcite Group, systematically analyze the hidden mechanism of the role of calcite powder in the papermaking pulping process, quantify its impact on power consumption, and explore its potential and challenges for industrial application, with the aim of providing a new perspective and technical reference for energy conservation and consumption reduction in the papermaking industry. 

II. Characteristics of Talc Powder and Its Application in Papermaking Overview 

2.1 Basic Characteristics of Kaolin Powder 

Gypsum is a layered silicate mineral with the chemical formula Mg3 (Si4O10)(OH)2. Its crystal structure is a typical 2:1 layered structure, consisting of two layers of silicon-oxygen tetrahedra sandwiched between a layer of magnesium-oxygen octahedra. This unique crystal structure endows gypsum powder with a series of distinctive physical and chemical properties: 

Morphological characteristics: Talc powder is usually in the form of plate-like or scale-like crystals. The thickness of the plates varies from the micrometer level to the nanometer level. The layers are bonded together by van der Waals forces and can be easily peeled off to form thin sheets. This is the most distinctive feature that distinguishes talc powder from other fillers such as calcium carbonate and kaolin. 

Low hardness: The Mohs hardness is only 1, making it one of the softest minerals in nature. This characteristic ensures that it is unlikely to cause significant wear when in contact with other substances. 

Chemical stability: Strong resistance to acids and alkalis, does not react with most chemicals, good thermal stability, decomposition temperature up to 900℃. 

Surface properties: The surface of talcum powder is inert. The hydrophobicity and hydrophilicity can be adjusted through modification. The specific surface area is moderate. 

2.2 Traditional Applications of Kaolin Powder in Papermaking 

In traditional paper-making applications, kaolin powder mainly serves the following functions as a filler: 

Improve optical performance: High whiteness and excellent covering power can significantly enhance the whiteness, opacity and glossiness of the paper, thereby improving the reading experience. 

Improving physical properties: Appropriate amounts of talcum powder can enhance the bulk, breathability and softness of paper, giving it a better feel and stiffness. 

Reduce costs: As a low-cost mineral filler, it can effectively replace some fibers, thereby reducing pulp consumption and unit costs. 

Optimize printing adaptability: A smooth surface is conducive to the even transfer of ink, thereby improving the quality and efficiency of printed products. 

III. Influencing Factors of Energy Consumption in the Pulping Process and the Potential Mechanism of Kaolin Powder 

3.1 Main Components and Influencing Factors of Energy Consumption in the Grinding Process 

The energy consumption during pulping refers to the energy consumed by a unit of dry pulp during the pulping process, usually expressed in kWh/t. The energy consumption mainly consists of the following components: 

Fiber dissociation energy: The energy required to overcome the hydrogen bond forces between fibers and disperse them into individual fibers. 

Fiber fining energy consumption: The energy used to create fine fibers on the surface of the fibers, increasing the specific surface area and bonding area. 

Ineffective energy consumption: This includes the cutting and twisting of fibers, heat generated by friction, and mechanical losses during equipment operation. 

The key factors influencing the energy consumption of pulping include: the type and concentration of the pulp, the material and tooth shape of the grinding discs, the grinding gap, the throughput, and the properties of the additives in the pulp, etc. Among them, the regulatory effect of the additives in the pulp on the energy consumption of pulping is receiving increasing attention. 

3.2 Hypothetical Mechanism of the Impact of Kaolin Powder on Grinding Power Consumption 

Based on the unique properties of talcum powder, the research team of Xinda Talc Group has put forward several mechanism hypotheses regarding its potential "invisible" energy-saving effect during the pulping process: 

Mechanism 1: "Lubrication and Isolation" Effect: The flake-like structure and high lubricity of talc powder may adhere to the surface of fibers or fill the gaps between fibers during the pulping process. When fibers are subjected to compression and shearing by the grinding disc, the layers of talc powder can act like "microscopic ball bearings", reducing the intense direct friction between fibers and between fibers and the grinding plate, thereby lowering the ineffective frictional energy consumption. At the same time, the flake-shaped talc powder may form a physical isolation layer on the fiber surface, preventing excessive adhesion and strong binding between fibers, allowing the pulping process to focus more on the directional dissociation of fibers rather than intense kneading. 

Mechanism 2: "Stress Dispersal and Buffering" Effect: The low hardness characteristic of talc powder makes it an ideal stress buffering material. In the high shear stress field of pulping, hard particles (such as incompletely dispersed calcium carbonate aggregates or impurities) will intensify local stress concentration, leading to fiber breakage and energy loss. However, the soft layers of talc powder can absorb and disperse part of the impact energy, protecting the integrity of the fibers, reducing energy waste caused by excessive fiber cutting, and allowing more energy to be used for the effective refinement of fibers. 

Mechanism 3: "Interface Regulation and Friction Optimization" Effect: The plate-like morphology and surface properties of talc powder may influence the fluid dynamics behavior and interface friction characteristics of the pulping system. An appropriate amount of talc powder may alter the rheological properties of the slurry, making it more fluid and reducing the retention and reflux of the slurry in the grinding zone, thereby improving the pulping efficiency. Additionally, the interaction between talc powder and the surface of fibers (such as hydrogen bonds, van der Waals forces) may change the friction coefficient of the fiber surface, thereby affecting the energy transfer efficiency during pulping. 

Mechanism 4: "Selective Action" Effect: Kaolin powder may exert selective effects on different types of fibers or different parts of the fibers. For instance, it may be more likely to act on the primary wall and middle layer of the fibers, promoting the opening of these more porous structures, while having a relatively smaller impact on the strong and resilient parts of the secondary wall of the fibers, thereby achieving more precise and efficient fiber dissociation. 

The above presents the complete theoretical basis and potential mechanism by which talcum powder can reduce the power consumption of papermaking pulping. Are these mechanisms valid? What are the actual energy-saving effects of different specifications of talcum powder? Xinda Talc Group has provided clear answers through laboratory small-scale tests and industrial pilot tests. In the second part of the series, real experimental data and practical results will be used to fully verify the actual value of talcum powder's energy-saving effect in pulping. 

References

[1] Chen Kefu. Comprehensive Book on Pulp and Papermaking Engineering [M]. Beijing: China Light Industry Press, 2001. 

[2] Liu Wenxia, Qiu Huayu. Principles and Applications of Wet Chemistry in Papermaking [M]. Beijing: China Light Industry Press, 2010. 

[3] Zhang Meiyun, et al. Papermaking Fillers and Pigments [M]. Beijing: China Light Industry Press, 2015.