Investigation into the Materials and Methods for the Prevention and Control of Carbon Monoxide During Underground Coal Mine Blasting

Abstract

Constrained by the layout and air volume of coal mine ventilation systems, the efficiency of diluting CO through ventilation during excavation blasting is relatively low, rendering it difficult to reduce or eliminate CO at the source. Based on the precipitation method, this study developed a copper–manganese–tin (Cu-Mn-Sn) catalyst. The elimination performance of the water-resistant Cu-Mn-Sn catalyst was quantitatively characterized in terms of catalytic activity and instantaneous reaction rate. Moreover, an in situ CO elimination method for blasting at excavation faces was proposed. Based on the segmented integrated blasting hole structure design, a catalyst cartridge for CO elimination in blasting holes was developed. Field tests were conducted at the Xinbai Coal Mine of Huating Coal Industry Group in China, and the influences of the weight and arrangement mode of the catalyst cartridge on CO elimination efficiency were investigated. The experimental results demonstrate that when the mass of the catalyst cartridge is 35 g and the “dual-end charge” structure is employed, a CO elimination efficiency of 51.5% can be achieved, offering a practical and feasible active prevention and control scheme as well as a theoretical paradigm for CO control in coal mine excavation blasting.

1. Introduction

During the coal mining process, the underground environment is relatively confined with poor ventilation conditions, which results in the accumulation of CO to varying degrees [1,2]. In recent years, incidents of carbon monoxide CO exceeding the limit and poisoning caused by coal mine fires, gas/coal dust explosions, and blasting excavation have occurred frequently. According to incomplete statistics [3,4,5,6,7],

Table 1. Analysis of Coal Mine CO Poisoning Accidents in China.

Time	Location	Analysis of Accident Causes	Casualties
15 January 2025	Heichong Coal Mine, Yunnan	CO poisoning caused by irregular operations during the unsealing of sealed areas.	2 fatalities
20 April 2023	Shanjiaoshu Coal Mine, Guizhou	CO poisoning resulting from a conveyor belt fire in the mine	16 fatalities, 3 injuries
19 January 2021	Ruifeng Coal Mine, Guizhou	CO over-limit poisoning during the excavation process	3 fatalities, 1 injuries
27 September 2020	Songzao Coal Mine, Chongqing	CO poisoning resulting from a conveyor belt fire in the mine	16 fatalities, 38 injuries
5 November 2017	Guanyao Yongan Coal Mine, Shanxi	Exceedance of the limit concentration of CO in underground coal mines	3 fatalities, 3 injuries
15 January 2015	Chenli Coal Mine, Fujian	CO poisoning occurred among workers during equipment demolition work in the shutdown period	4 fatalities, 5 injuries

below shows the deaths of underground coal mine personnel caused by CO exceeding the limit in China over the past 10 years.

During the blasting excavation process in underground coal mines, the incomplete reaction of industrial explosives generates a large amount of CO, which seriously threatens the physical and mental health of underground coal mine workers. CO is a colorless, odorless and toxic gas, and its affinity for binding to hemoglobin (Hb) is 200–300 times higher than that of oxygen [8,9]. This high affinity causes CO to bind with Hb to form carboxyhemoglobin (COHb), thereby reducing the oxygen-carrying capacity of Hb. Due to the greater affinity of CO for Hb, it displaces oxygen from Hb binding sites, preventing red blood cells from effectively delivering oxygen to tissues. Consequently, the presence of CO leads to tissue hypoxia, which, if not promptly addressed, can result in tissue damage or even death [10,11,12]. In addition, according to the provisions of the Coal Mine Safety Regulations in China’s coal industry [13], the upper limit of CO concentration in underground coal mines is 24 ppm. Once the CO concentration exceeds this limit, it will seriously restrict the safe production of coal mines and even cause significant economic losses. At present, the commonly used method for controlling CO generated by blasting in coal mine driving faces is roadway ventilation dilution, but its effect is negligible and cannot address the hazards caused by excessive CO concentrations [14,15]. Therefore, the efficient and rapid elimination of CO plays a crucial role in the safe production of coal mines.

At present, the most thorough and effective method for treating CO is catalytic oxidation. Unlike physical adsorption, it is a chemical reaction that converts CO into CO₂ gas through an oxidation pathway, thus completely eliminating CO gas [16,17,18]. Current catalytic oxidation materials mainly include noble metal catalysts and non-noble metal catalysts. Noble metal catalysts (e.g., Pt, Pd, Ru, Au) exhibit excellent performance in CO oxidation reactions due to their outstanding low-temperature activity and stability [19,20]. However, their high cost and limited resource reserves have prompted researchers to develop high-performance non-noble metal alternative materials [21,22,23]. For example, Cu-Mn-based catalysts not only show excellent catalytic oxidation performance but also have cost-effectiveness and a relatively simple preparation process, thus being widely used in the field of air purification. Traditional Cu-Mn-based catalysts are susceptible to water vapor when eliminating CO in underground coal mines, which leads to the deactivation of the eliminant and results in poor elimination efficiency.

This study focuses on optimizing the water resistance of Cu-Mn-based catalysts and thoroughly investigating the influence mechanism of Sn doping on the CO catalytic process of Cu-Mn-Sn-based catalysts in humid environments. Meanwhile, aiming at the working conditions of coal mine blasting excavation, an in situ elimination method for blasting on the underground excavation face of coal mines is proposed, and engineering tests are carried out at the Huating Xinbai Coal Mine, which provides a strong guarantee for the safe production of underground coal mines.

2. Results and Analysis

2.1. Activity Analysis of CO Catalysts

In a dry environment, an experimental analysis was carried out on the reaction activity of the samples during the catalytic process. Based on Formula (4), the instantaneous reaction quantity of CO after the injection of the mixed gas was calculated. The curves depicting the relationship between CO concentration, instantaneous reaction quantity, and time for catalysts with varying Sn contents are presented in Figure 1 and Figure 2.

From the analysis, it can be deduced that the CO concentration of all samples demonstrates a pattern of initially increasing and subsequently decreasing, whereas the instantaneous CO reaction quantity presents an inverse pattern of initially decreasing and then increasing. This phenomenon is primarily ascribed to the dynamic occupation process of active sites on the catalyst surface. At the initial stage of the reaction, the active sites are abundant, and CO is rapidly adsorbed, leading to a decline in CO concentration and a relatively high reaction quantity. As the reaction progresses, the active sites gradually approach saturation, the reaction quantity decreases, and CO starts to accumulate. After a certain period, partial regeneration of active sites may occur, resulting in a recovery of the reaction quantity and a subsequent decrease in CO concentration.

The variation in Sn content exerts a significant regulatory influence on the catalytic behavior. Regarding the variation in CO concentration, as the Sn content increases, the time at which the concentration peak appears is postponed, and the peak height shows a tendency of first increasing and then decreasing. Among them, the Sn-5 to Sn-20 samples exhibit relatively high peak concentrations, indicating that an appropriate amount of Sn may affect the equilibrium between the initial generation and consumption of CO.

In terms of the variation in instantaneous reaction quantity, samples with an appropriate amount of Sn (especially 5–20 wt%) display a more pronounced recovery of the reaction quantity in the middle and late stages of the reaction, suggesting that their surface active sites possess better anti-deactivation performance. When the Sn content is further increased to 25–30 wt%, the decrease in CO concentration of the samples in the late stage of the reaction is relatively slow, and the recovery of the instantaneous reaction quantity is weak. This implies that an excessive amount of Sn may cover the active sites, leading to a reduction in the overall reaction efficiency.

The time points at which the CO concentration and the instantaneous CO reaction amount of each sample attained equilibrium were selected for analysis, as depicted in Figure 3 and Figure 4. Based on the aforementioned results and in conjunction with Figure 3 and Figure 4, it can be inferred that under dry reaction conditions, the incorporation of Sn exerts a substantial impact on the catalytic oxidation kinetics of CO by modulating the surface structure of the catalyst and the state of active sites. The catalyst with a Sn mass fraction of 20 wt% attains the optimal activity and the most favorable CO catalytic effect, achieving an excellent equilibrium between activity and stability.

2.2. Analysis of the Water Resistance of CO Catalysts

To assess the water resistance of samples with varying Sn contents, activity tests were conducted on the corresponding samples in a humid environment. The test findings indicated that the samples labeled Sn-0, Sn-10, Sn-25, and Sn-30 demonstrated low activity, and these samples in the humid state entirely lost their activity. In contrast, the samples labeled Sn-5, Sn-15, and Sn-20 had high activity, and their humid counterparts still retained partial activity. A mixed gas containing 1% CO was introduced into the reaction system, the variation in CO concentration was monitored, and the instantaneous reaction quantity was calculated. The results are presented in Figure 5 and Figure 6.

An investigation was carried out on the water poisoning resistance of samples with varying Sn contents in a humid environment. It was discovered that the regulation of Sn content is decisive in preserving the activity of the samples. The experimental findings demonstrate a non-linear correlation between Sn content and water poisoning resistance. Specifically, the Sn-0, Sn-10, Sn-25, and Sn-30 samples completely lost their activity in the humid environment, while the Sn-5, Sn-15, and Sn-20 samples still retained partial activity, which verifies their certain degree of water resistance. Among these samples, the Sn-20 sample displayed the optimal activity and stability, featuring the fastest CO conversion rate, the highest instantaneous reaction amount, and a relatively gentle trend of activity attenuation during the testing period. This indicates that this sample has the most favorable comprehensive performance under humid conditions.

3. Materials and Methods

3.1. Preparation Process of CO Catalysts

In this study, the precipitation method was mainly used for the preparation of CO catalysts. First, aqueous solutions of copper nitrate (Cu(NO₃)2·3H₂O), tin tetrachloride pentahydrate (SnCl₄·5H₂O), manganese nitrate (Mn(NO₃)₂), and sodium carbonate (Na₂CO₃) (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) were prepared separately. The prepared aqueous solutions of copper nitrate, tin tetrachloride pentahydrate, and manganese nitrate were thoroughly mixed uniformly according to the proportions in

Table 2. Experimental Conditions.

Serial Number	Mass Fraction (wt%)			Cu(NO3)2·3H2O (aq, 0.58 mol/L)	Solution Volume (mL)		Na2CO3 (aq 2.5 mol/L)
	Cu	Mn	Sn		Mn(NO3)2 (aq, 50 wt%)	SnCl4·5H2O (aq, 0.16 mol/L)
1	26.67	53.33	20.00	150	47.5	218.49	200

. Then, the temperature of the sodium carbonate aqueous solution was stably maintained at 70 °C by means of a thermostatic water bath, and vigorous stirring was carried out. Dilute nitric acid was used to adjust the pH value of the solution to 8.3, followed by continuous stirring for 4 h at a constant temperature of 70 °C using a water bath magnetic stirring device. After that, the precipitate was subjected to vacuum filtration using a circulating water multi-purpose vacuum pump and fully washed with distilled water. Subsequently, the precipitate was placed in a drying oven and dried at 110 °C, followed by calcination at 400 °C for 4 h. Finally, the calcined precipitate was ground into powder using a mortar to obtain the Cu-Mn-Sn-based catalyst. Then, the catalyst powder was screened through a vibrating sieve to ensure that its particle size was less than 300 meshes. A polyvinyl chloride (PVC) tube with a length of 10 cm, a diameter of 3 cm, and a thickness of 1 mm was selected to prepare the CO catalyst cartridge. A layer of waterproof membrane was wrapped around the outside of the CO catalyst cartridge to ensure its applicability in both dry and wet blast holes. The experimental flow chart is shown in Figure 7.

3.2. Activity Test of CO Catalyst

To enhance the water resistance of Cu-Mn-Sn catalysts, samples with Sn mass fractions of 0, 5%, 10%, 15%, 20%, 25%, and 30% were respectively prepared in accordance with the aforementioned experimental procedure, and activity tests were carried out via the dynamic approach. The schematic diagram of the experimental system for the activity test is presented in Figure 8. To guarantee the accuracy of the experimental results, air-tightness inspection and system verification were conducted on the experimental system prior to commencing the experiment to ascertain that the experiment could be executed normally. Initially, 10 g of the catalyst sample was placed within the reaction chamber, with 3 cm of filter cotton positioned at both the front and rear ends of the chamber to secure the sample. The temperature of the water bath tank was set at 25 °C, and after a 2 h stabilization period, the flow rate was adjusted to 80 mL/min using a flowmeter before initiating the experiment. The catalytic performance of the samples was characterized by activity and instantaneous reaction rate, respectively.

3.3. Analysis of Water Poisoning Resistance of CO Catalysts

Catalysts are susceptible to deactivation under the influence of water vapor during storage. The quantitative index of sample humidity can be employed to characterize the water absorption level of catalysts after being stored in a humid environment, thereby simulating the actual service conditions following underground storage in coal mines and further investigating the impact of environmental humidity on their catalytic performance.

Using a balance, accurately weigh 10 g of each of the aforementioned 8 samples and place them in trays. Subsequently, position the trays in a sealed container equipped with a humidifier. With the assistance of a humidity controller, adjust the humidity within the sealed container to 95% to mimic the humid underground environment of coal mines. At regular intervals, weigh each sample until its mass reaches a constant value. Then, remove the samples and transfer them to centrifuge tubes. The test bench is depicted in Figure 9, where 1–8 represent the trays containing the samples.

3.4. Characterization Indicators of Catalytic Oxidation Performance

3.4.1. Activity

Among these, the activity of the catalyst can be characterized by the activity per unit mass of the catalyst, which is considered the preferred indicator [24],

$$\xi \stackrel{ \mathrm{def} }{=}{\displaystyle \frac{d\xi }{dt}}$$

(1)

$\xi$ is the reaction rate, defined as

$$d\xi \stackrel{\mathrm{def}}{=}{\displaystyle \frac{\Delta n_{B_i}}{v_i}}$$

(2)

where $\Delta n_{B_i}$ is the variation of component $B_i$, mol.

In accordance with the ideal gas law,

$$pV=nRT$$

(3)

where $p$—pressure, Pa. $V$—gas volume, m³. $T$—temperature, K. $n$—amount of substance of the gas, and mol. $R$—molar gas constant, 8.314472 J·mol⁻¹·K⁻¹.

The variation of component $B_i$ is as follows:

$$\Delta n_{B_i}=n_{B_i}-n_{B_i}^0={\displaystyle \frac{P}{R\cdot T}}\cdot {\displaystyle {\int }_0^t{V}_{B_i}}dt$$

(4)

$$V_{B_i}={\displaystyle \frac{L}{60}}\cdot \left(c-c_0\right)\cdot t\cdot {10}^{-6}$$

(5)

Within the catalytic reaction system, when the rate of non-catalytic reactions is disregarded, the rate of the catalytic reaction is

$$s={\displaystyle \frac{1}{m}}\cdot {\displaystyle \frac{d\xi }{dt}}$$

(6)

where $n_{B_i}$ and $n_{B_i}^0$ represent the amount of substance (i) at time (t) and the initial time (t = 0) respectively, with the unit of mol. $v_i$ is the stoichiometric coefficient of the component, which is positive for products and negative for reactants. m denotes the mass of the catalyst, with the unit of g. s represents the activity of the catalyst, with the unit of mol·g⁻¹·s⁻¹. $V_{B_i}$ is the instantaneous volume variation of CO during the catalytic process, with the unit of m³. L stands for the flow rate of the mixed gas, with the unit of mL/min. t is the time required to reach reaction equilibrium, with the unit of s. $c$ represents the instantaneous CO concentration in the test, in percentage (%). $c_0$ is the initial CO concentration in the mixed gas, in percentage (%).

3.4.2. Instantaneous Reaction Rate

The instantaneous reaction rate denotes the quantity of CO substance altered per unit time throughout the catalytic process. The derivative of the CO reaction quantity with respect to time is computed [25], as presented below.

$$v_{CO}(t)={\displaystyle \frac{d\Delta n_{CO}}{dt}}$$

(7)

3.4.3. Catalytic Efficiency

Catalytic efficiency pertains to the efficiency of CO catalysis throughout the catalytic process. It is represented by the ratio of the total reaction quantity of CO to the total inlet quantity of CO in the experiment, and the calculation method is presented in Formula (8).

$$\eta ={\displaystyle \frac{n_{c{o}_{\lambda }}-n_{c{o}_{\mathrm{out}}}}{n_{c{o}_{\lambda }}}}\times 100\%$$

(8)

where $\Delta n_{CO}(t)$—amount of CO reacted, mmol. $v_{CO}(t)$—instantaneous reaction rate, mmol·t⁻¹. $\eta$—catalytic efficiency, %. $n_{c{o}_{\lambda }}$—amount of CO fed into the inlet during the catalytic process, mmol. $n_{c{o}_{\mathrm{out}}}$—amount of CO at the outlet during the catalytic process, mmol.

3.5. Catalyst Characterization Methods

To clarify the characterization analysis, water resistance mechanism, and relationships among relevant performance characteristics of the Cu-Mn-Sn catalyst, please refer to the published research in ACS Omega 2022, 7, 12,390–12,400 [23].

• N₂ adsorption–desorption: Measured by BET method to analyze specific surface area, pore size distribution, and total pore volume;
• XRD: Rigaku Ultima IV diffractometer to determine crystal phase composition and crystallization degree;
• SEM: ZEISS MERLIN Compact scanning electron microscope to observe surface morphology and pore structure;
• XPS: Al Kα excitation source to analyze surface element valence states;
• FTIR: Nicolet iS50 spectrometer to characterize surface hydroxyl and water adsorption characteristics.

For detailed results, please refer to the published study, “Effect of Sn on the CO Catalytic Activity and Water Resistance of Cu-Mn Catalyst” [23].

4. Principle and Field Experiment of In Situ CO Removal Technology

4.1. Project Overview

The Xinbai Coal Mine under China Huating Coal Industry Group is an underground coal mine. The auxiliary transportation inclined roadway of the 35,203 upper gateway is a rock roadway, which is arranged on the floor of Coal Seam 6–2. In accordance with the ventilation design scheme of the mine, during the excavation of the auxiliary transportation inclined roadway of the 35,203 upper gateway, two FBD No. 6.0 counter-rotating axial flow local fans and one BPJ1-78/560SF flameproof and intrinsically safe dual-power variable frequency governor for coal mine fans are selected. The diameter of the matched air duct is 600 mm, the air volume is set at 220 m³/min, and the maximum ventilation distance reaches up to 450 m. The roadway section is designed as a semi-circular arch, with a net width of 4000 mm, a net height of 4300 mm, and a maximum net cross-sectional area of 12.28 m². The layout particulars of the 35,203 driving roadway are presented in Figure 10.

4.2. Technical Principle of In Situ CO Elimination in Blasting Holes

The in situ CO elimination technology within blasting holes is a CO control technology developed based on the concept of “source catalytic conversion”, and its operational principle is “heat-driven catalytic oxidation”. This technology harnesses the high temperature generated instantaneously during blasting to activate the oxygen-vacancy active sites on the catalyst surface. It facilitates the adsorption of CO molecules onto these active sites and promotes electron transfer, thereby enabling the rapid oxidation of CO to CO₂. The activation energy for this process is directly supplied by the blasting thermal energy, and the reaction duration is highly consistent with that of the blasting shock wave, achieving synchronization between the generation and elimination of pollutants.

The structural design of this technology employs a segmented integrated layout, as depicted in Figure 11. Electronic detonators and wires, mining emulsion explosives, catalyst cartridges, and columnar yellow clay are sequentially arranged within the blasting holes. Three sticks of emulsion explosive are placed in each blasting hole. The electronic detonator is inserted into the emulsion explosive at the bottom of the hole, and finally, the hole mouth is sealed with yellow clay. The catalyst cartridge is encapsulated in a moisture-resistant polyvinyl chloride (PVC) pipe and connected to the emulsion explosive to ensure that the catalyst released by the fragmentation of the catalyst cartridge at the moment of blasting can directly contact the blasting fumes generated by blasting. This structure not only does not impede the rock-breaking effect of blasting but also can utilize the thermal radiation and shock wave from the explosive section to ensure the rapid activation of the catalyst.

To ensure the reliable performance of the catalyst under harsh underground mining conditions—including high humidity, dust, and intense blasting shock—a systematic packaging design was developed for the catalyst cartridge. The key technical specifications are outlined below.

(1)

Casing Material and Structure

A flame-retardant and anti-static polyvinyl chloride (PVC) tube was selected as the outer casing. The tube dimensions are 10 cm in length, 3 cm in inner diameter, and 1 mm in wall thickness. The material operates within a temperature range of −10 to 150 °C and exhibits a compressive strength of ≥5 MPa, complying with coal mine explosion-proof standards. This design ensures mechanical integrity under blasting impact and typical underground loads.

(2)

Waterproofing and Sealing

The outer surface of the PVC tube was wrapped with two layers of polytetrafluoroethylene (PTFE) waterproof membrane (0.1 mm thick). Joints were sealed with silicone sealant, achieving an overall waterproof rating of IP67. This effectively isolates the catalyst from water ingress in blast holes, preventing deactivation due to moisture.

(3)

Internal Immobilization and Vibration Resistance

A 3 cm thick quartz wool layer was placed at both ends of the PVC tube to immobilize the catalyst powder (particle size < 300 mesh). This configuration buffers vibration, preventing powder compaction, agglomeration, or loss, thereby ensuring uniform dispersion of the catalyst upon detonation.

(4)

Connection and Synergistic Activation Mechanism

The cartridge was connected to the emulsion explosive via an M20 × 1.5 threaded interface. This ensures synchronous rupture of the cartridge upon detonation, enabling rapid mixing of the catalyst powder with blasting fumes and facilitating in situ CO oxidation.

(5)

Storage Stability

The packaged cartridges can be stored under dry conditions (relative humidity ≤ 60%, temperature 5–35 °C) for up to 6 months. Accelerated aging tests confirmed no significant loss of catalytic activity under these storage conditions.

4.3. Field Test Design

The experiment designated the area adjacent to Chamber No. 2 of the 35,203 rock roadway as the experimental site. Catalyst cartridges were manufactured using the aforementioned CO catalyst powder and PVC pipes. Subsequently, the experimental effects of cartridges loaded with 10 g, 20 g, 30 g, and 40 g of the catalyst were analyzed. In total, 60 blasting holes were arranged at the tunneling face, with a consistent charge quantity per hole for each blasting operation. The catalyst cartridges were filled into the blasting holes in the manner depicted in Figure 11a, and the experiments were carried out in accordance with the steps outlined in Figure 12. Among these arrangements, the CO sensor was positioned 40 m away from the tunneling face and connected to a secondary display device, which was capable of real-time display of the CO concentration and was placed in Chamber No. 3 of the tunneling roadway. After each blasting, the data from the CO sensor were recorded, and the optimal mass of the CO catalyst was determined through comparative analysis.

Regarding the arrangement pattern of catalyst cartridges in the blasting holes, three design schemes were proposed, as shown in Figure 11a–c, to screen out the optimal layout structure suitable for engineering applications. A total of 60 blasting holes were arranged at the tunneling face, and three groups of experiments were designed according to the methods presented in Figure 11. The hole depth of Group a and Group b was 1500 mm, whereas that of Group c was 1800 mm. Among the parameters, the length of the catalyst cartridge was 300 mm, the diameter of the cartridge was 30 mm, the diameter of the blasting hole was 400 mm, the length of the emulsion explosive was 200 mm, and the length of the stemming clay was 500 mm. The experiments were conducted following the steps in Figure 12. After each blasting, the data from the CO sensor were recorded, and the optimal mass of the CO catalyst was obtained through comparative analysis.

4.4. Analysis of Results

Under normal ventilation conditions, at a distance of 40 m from the driving face, the CO concentrations in the roadway airflow under the action of catalyst cartridges with masses of 10 g, 20 g, 30 g, and 40 g were respectively measured. Continuous monitoring was conducted for 30 min, the data were recorded and organized, and the results were plotted as presented in Figure 13. Fitting was carried out on the peak CO concentrations in the roadway corresponding to catalyst cartridges of different masses, and the fitting results are shown in Figure 14.

As depicted in Figure 13, when the masses of the CO catalyst cartridges within the blasting holes at the driving face are 10 g, 20 g, 30 g, and 40 g respectively, the peak CO concentrations in the roadway are 697 ppm, 656 ppm, 541 ppm, and 556 ppm in succession. Evidently, as the mass of the CO catalyst in the blasting holes increases, the peak CO concentration in the roadway exhibits a gradually decreasing tendency. Nevertheless, when the masses of the CO catalyst are 30 g and 40 g, the disparity in the peak CO concentrations in the roadway is relatively minor.

A fitting process was carried out between the different peak concentrations and the masses of the catalyst cartridges to derive the fitting formula. It can be deduced from Figure 14 and the fitting formula that there exists an optimal value of 35 g within the range of 30–40 g for the mass of the catalyst cartridge. That is to say, when the mass of the CO catalyst per blasting hole is 35 g, the peak CO concentration in the roadway attains the minimum value of 519.5 ppm, which is most appropriate for the blasting operation at the roadway driving face. Additionally, it can also be discerned from Figure 13 that as the mass of the CO catalyst increases, the duration of the peak CO concentration in the roadway gradually shortens. However, when the masses of the CO catalyst per blasting hole are 30 g and 40 g respectively, the durations are comparable, basically remaining at approximately 5.2 min. Therefore, to attain the optimal effect of the in situ CO elimination test in the blasting holes at the roadway driving face, the mass of the CO catalyst in each blasting hole is specifically chosen as 35 g.

By comparing the CO elimination effect in the roadway under the traditional ventilation mode with that when using the optimized catalyst cartridge mass of 35 g and plotting the concentration curve (as shown in Figure 15), it can be observed that under the traditional ventilation mode, the peak CO concentration in the roadway reaches as high as 967 ppm. After placing the CO catalyst cartridges in the blasting holes, the maximum CO concentration in the roadway is 549 ppm. In comparison with the traditional ventilation mode, the CO elimination efficiency is 43.2%, and the elimination effect is remarkable. Meanwhile, the alarm time is reduced to 20% of the original. The aforementioned effects indicate that the catalyst comes into contact with carbon monoxide during the blasting process, thereby realizing the elimination of carbon monoxide.

The experiment conducted a comparison between three typical arrangement methods of catalyst cartridges and the traditional ventilation dilution method. These three methods are the “Orifice charge”, “Bottom charge”, and the “Dual-end charge”. The collected data on CO concentration were plotted, and the results are presented in Figure 16. As can be observed from Figure 16, when the orifice charge method was employed, the peak CO concentration in the roadway reached a maximum of 549 ppm at 11 min; under the bottom charge method, the peak concentration reached 682 ppm at 13 min; and the dual-end charge method reached 469 ppm at 10 min. In comparison with the orifice charge and bottom charge, the CO conversion efficiency of the dual-end charge increased by 17% and 34% respectively, and the time efficiency improved by 10% and 30% respectively. When compared with the traditional ventilation mode, the dual-end charge reduced the peak concentration in the roadway from 967 ppm to 469 ppm, achieving an elimination efficiency of 51.5%, thereby demonstrating the optimal effect.

In the single charging mode of either orifice or bottom, the catalyst can only function in local regions. Although the orifice charge can intercept the escaping gas, it cannot intervene in the high-concentration CO generated in the high-temperature core area of blasting. Although the bottom charge can react at the source of CO generation, the CO gas driven by the explosion shock wave will rapidly pass through the catalyst cartridge, resulting in insufficient contact reaction time. The dual-end charge structure establishes a coordinated elimination system of “source catalysis-path interception”. The bottom cartridge acts directly on the reaction zone in the initial stage of the explosion to immediately eliminate the primary CO; the orifice cartridge is located on the inevitable path of the explosion gas expanding and diffusing out of the hole, performing secondary elimination of the escaped CO. This spatial hierarchical arrangement effectively prolongs the reaction time of the gas–solid two phases and enhances the effective mixing degree of the catalyst and CO gas by optimizing the flow field distribution.

5. Conclusions

This research endeavors to put forward a novel material and methodology for the prevention and control of CO during blasting excavation in coal mines. Initially, a Cu-Mn-Sn catalyst was synthesized, and its activity and resistance to water poisoning were analyzed. Subsequently, a catalyst cartridge with moisture-proof properties was developed, and the placement approach of the catalyst cartridge in blasting holes was investigated. Finally, on-site tests were conducted at the Xinbai Coal Mine of Huating Coal Industry Group, China, to verify the CO elimination effect in the roadway. The primary conclusions are as follows:

(1)

The elimination performance of the water-resistant Cu-Mn-Sn eliminator was quantitatively characterized by means of catalytic activity and instantaneous reaction rate, and the influence mechanisms of dry and humid environments on the catalytic oxidation of CO by the Cu-Mn-Sn catalyst were explored. The results indicate that when the tin content is 20%, the catalytic oxidation effect of carbon monoxide is optimal in both dry and humid environments.

(2)

An in situ CO elimination method for blasting holes at the driving face was proposed. Based on the principle of “heat-driven catalytic oxidation”, this method realizes the instantaneous synchronization of CO generation and elimination through the design of a segmented integrated blasting hole structure, offering a feasible active prevention and control scheme for CO prevention and control during coal mine excavation blasting.

(3)

Field investigations have confirmed that the “dual-end charge” structure of CO catalyst cartridges can effectively mitigate the hazard of blasting-derived CO. By leveraging the spatial synergistic effect between the hole bottom and hole orifice, this structure couples the explosive gas flow field, significantly extends the gas–solid reaction time, and enhances the elimination efficiency. It provides an innovative solution and theoretical paradigm for green blasting in coal mines and active gas purification in confined spaces.