The preparation of a novel hydrogel based on crosslinked polymers for suppressing coal dusts

https://doi.org/10.1016/j.jclepro.2019.119343Get rights and content

Highlights

  • A dust suppression gel for coal transportation was studied and prepared.

  • The use of dust suppression gel reduces the water consumption of dust suppression.

  • The use of dust suppression gel improves the efficiency of dust suppression.

  • The wind erosion resistance of dust suppression gels was verified by simulation technology.

  • Dust suppression gel provides a new way to solve the problem of coal dust emission during coal transportation.

Abstract

Coal is one of the most important energy sources in China, and a lot of coal dust will be produced in the process of coal production and transportation. The coal dust generated will cause environmental pollution and waste of resources, and it can have adverse effects on human health. Water spraying is usually used to suppress coal dust in coal production and transportation, but the effect of this method is not lasting and a lot of water resources were wasted. In order to better solve the problem of coal dust pollution and waste of water resources, a new dust suppression gel was prepared by graft copolymerization of itaconic acid-acrylic acid polymer and bentonite. The properties of the dust suppression gels were comprehensively studied through chemical experiments, numerical simulation and field tests. The results showed that the wettability of the dust suppression gel to coal dust was 2 times that of the water. Because of the water retention property of the dust suppression gel, the use of dust suppression gel could save 90% of the dust-proof water consumption than that of spraying water. The dust suppression gel had excellent wind erosion resistance and could effectively reduce the occurrence of coal dust during coal transportation. The dust suppression gel is used for dust removal in fully mechanized mining face, and its efficiency is more than 9 times that of spraying water. In summary, the dust suppression gel prepared in this paper is suitable for dust prevention during production and transportation of the coal mining industry, and can effectively reduce the water consumption when dustproofing under the condition of improving dust removal efficiency. This study is of great significance to the sustainable development of coal mining industry and environmental protection.

Introduction

Coal dust is generated in the production, transportation, and loading of raw coal (Medeiros et al., 2012, Shchukina et al., 2017). According to the measured data of coal mine production site, the coal dust concentration in fully mechanized mining face exceeds 1000 mg/m3 (Cai et al., 2019, Chen et al., 2018, Cheng et al., 2012). Workers working in this high concentration coal dust environment for a long time are prone to pneumoconiosis (Cai et al., 2018, Wang et al., 2019; Li et al., 2019a, Li et al., 2019b). According to the data of the statistical bulletin on the development of health care in China in 2017, there are 22701 cases of occupational pneumoconiosis, accounting for 84.8% of the total number of occupational diseases. Pneumoconiosis is one of the most serious occupational diseases in China’s mining enterprises (Qin et al., 2018, Myriam et al., 2018, Zhang et al., 2018c). According to incomplete statistics, approximately 1900 deaths are reported every year, moreover, the death toll caused by pneumoconiosis is approximately 6 times greater than that from various mine disasters (Sun et al., 2018,2019a,b). In the process of coal transportation, a large amount of coal dust will be produced (Bao et al., 2018a; Zhang et al., 2018b), which will lead to the loss of coal and environmental pollution (Lodhia and Hess, 2014; Wang et al., 2019e; Zhang et al., 2018a). The production of coal dust not only causes waste of coal resources, but also causes serious pollution to the environment (Jin et al., 2018, Jin et al., 2019; Liu et al., 2018a; Nie et al., 2017c). Therefore, whether from the perspective of waste of resources or from the perspective of human health, the treatment of coal dust pollution is imminent (Nie et al., 2017, Nie et al., 2017; Peng et al., 2019a).

In the actual production process, the dust reduction measures commonly used in coal mines are spraying water (Han et al., 2019; Liu et al., 2019d). Although spraying a large amount of clean water has a certain inhibitory effect on coal dust (Wang et al., 2019h; Zhang et al., 2019), due to the lack of lasting inhibition effect and poor wind erosion resistance, the problem of coal dust pollution in construction site still exists, and in the process of dust control caused a large amount of waste of water resources (Northey et al., 2016).

Many studies and practical applications have shown that chemical dust suppression is the most effective method of dust suppression in many different situations (Li et al., 2018, Worzakowska, 2018; Wang et al., 2018b). Researchers around the world have studied chemical dust suppression methods. For example, Xu et al. (2018) studied the auxiliary effect of surfactant on coal dust control, and obtained the key factors affecting its dust removal efficiency. In addition, Omane et al. (2018) studied the dust suppression efficiency of water and selected chemical surfactants (salts, non-chlorinated reagents and polymers) at different temperatures, and obtained the influence of temperature on the dust suppression effect of surfactants. Dang et al. (2017) fabricated a mixture of oxidized corn starch and gelatin based on degraded gelatin and oxidized corn starch, and conducted simulated experiments in an airtight, indoor dust-emission test facility. Their results showed that the dust suppression rates for 2.5 and 10 μm dusts can reach up to 68.2% and 78.7% respectively. However, the particle size range of coal dust is 0.2–200 μm and the maximum distribution frequency is 30 μm (Liu et al., 2018c), so the inhibition effect of this gelatin mixture on coal dust is limited (Wang et al., 2018a,2019c). Gonzalez et al. (2019) have found through research that using 6H2O·MgCl2 brine effectively reduces water consumption used for dust suppression in haul roads, demonstrating that the use of 6H2O·MgCl2 byproduct is a very promising material for addressing water management issues in the mining industry. However, 6H2O·MgCl2 is slightly harmful to drinking water sources, which limits its application area.

Although the above scholars continue to study and improve chemical dust suppression methods, there is still no chemical dust suppression method suitable for coal production. Spraying clean water is still the main dust-proof measure in coal mine production (Nie et al., 2016; Peng et al., 2019b; Wang et al., 2019b). Therefore, it is of great significance to study and prepare a kind of environmental protection, high efficiency and water saving dust suppressant.

Graft copolymerization is an easy and effective way to enhance and modify molecular structures via chemical modification (Zhang, 2018; González and Igarzabal, 2017; Nie et al., 2017a). Under the influence of an initiator, proper graft monomers can be selected to trigger a graft copolymerization reaction (Liu et al., 2019e; Lv et al., 2019). Subsequently, the graft compound’s favorable characteristics can be transferred to the graft copolymer, and a polymer product with combined optimized properties can be obtained (Hu et al., 2017). Bentonite is a nonmetallic mineral, which mainly consists of montmorillonite (Bao et al., 2018b) and possesses a strong adsorption ability that mainly comes from the physical and chemical adsorption (Frohlich et al., 2019). The chemical adsorption, which is often irreversible and more stable compared to the physical adsorption (Saleh et al., 2018), comes from the chemical bonds between the adsorbents and adsorbates (Xu et al., 2014, Liu et al., 2015). If bentonite is chemically modified (e.g. hydroxylation), the solubility can be greatly enhanced (Wang et al., 2019a; Liu et al., 2018d). In the meantime, additional capabilities can be integrated to bentonite via chemical modification. Due to these properties, bentonite has become the ideal choice for the preparation of a coal dust suppressant (Li et al., 2017, Kyzas et al., 2018).

In order to effectively solve the problem of coal dust pollution and waste of water resources in coal production and transportation. In this paper, a kind of dust suppression gel was prepared by using graft copolymerization of itaconic acid and acrylic acid as raw material. In order to ensure the practical application effect of the dust suppression gel, the dust suppression efficiency and the dust suppression water consumption during the application of the dust suppression gel were quantitatively analyzed. Analysis was conducted using three types of study: a laboratory study, a numerical simulation study and a field study. The specific objective of the laboratory study is to measure the water holding capacity of the coal dust treated with dust suppression gel, so as to understand the water saving ability of the dust suppression gel. The specific goal of the simulation study is to obtain the wind erosion rate of coal dust in the high speed airflow field through simulation, so as to ensure the actual effect of using dust suppression gels in the high-speed transportation of coal. The specific goal of the field study is to determine the dust suppression efficiency of the dust suppression gel in fully mechanized coal mining face. Finally, we found that the prepared dust suppression gel has good water retention ability and can effectively reduce the concentration of coal dust in fully mechanized coal mining face when applied.

Section snippets

Materials and equipment

The materials and equipment used in this study are as follows.

Single factor experiments

In this paper, using water as reaction medium, a series of single factor experiments were conducted. By changing the amount of bentonite, itaconic acid to acrylic acid ratio, amount of crosslinking reagent, initiator concentration, and neutralization degree, the product’s water absorption rate was analyzed. Based on the results, the reaction condition was optimized for each factor. Table 1 shows the parameters in single-factor experiments. Fig. 5 summarizes the single factor experimental

Conclusions

Coal dust pollution and waste of water resources are the biggest risks faced by mining industry. There is still no reasonable and effective way to deal with these problems. In order to solve the above problems, using IA and AA as graft monomers, an environmentally friendly dust suppressant gel was fabricated by preparing an IA-co-AA with IA and AA monomers and chemically modifying the bentonite.

1. A single factor experiment was conducted to obtain the optimum condition for the dust suppressant

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work has been funded by the National Key R&D Program of China (2017YFC0805201), National Natural Science Foundation of China (NO. 51874191 and 51404147), the Focus on Research and Development Plan in Shandong Province (NO.2017GSF20111), the China Postdoctoral Science Foundation (NO.2015M570601 and 2017T100503), the Graduate Science and Technology Innovation Project (No. SDKDYC190347).

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