New Respirable Dust Suppression Systems for Coal Mines

Dust suppression in coal mines is a worldwide problem which has not been solved effectively. The applica-tion of negative pressure secondary dust removal (NPSDR) is a breakthrough in the coal mine safety field. In this paper,NPSDR technology and ultrasonic dust suppression systems are introduced. High pressure water is supplied to the NPSDR device which is mounted on the shearer. A negative pressure field is formed in the device. At the same time,the dusty air around the shearer drum will be sucked into,and purged from,the NPSDR device by the negative pressure field. An ultrasonic dust suppression system uses water and compressed air to produce micron sized droplets which suppress respirable coal dust effectively. The NPSDR technology can be used for shearer dust suppression while ultra-sonic dust suppression can be applied in areas such as the transportation positions. These dust suppression methods have the following advantages: high efficiency,wide applicability,simple structure,high reliability and low cost.

Effects of proper drilling control to reduce respirable dust during roof bolting operations

Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.

Development of a roof bolter drilling control process to reduce the generation of respirable dust

The drilling operation in the roof bolting process,especially in hard rock,generates excessive respirable coal and quartz dusts,which could expose the roof bolting operator to continued health risks.Previous research has shown that the amount of respirable dust produced is dependent on the main drilling parameters,specifically the drilling rotational and penetration rate.In this paper,a roof bolter drilling control process was proposed to reduce the generation of respirable dust.Based on the analysis of laboratory drilling test results,a rational drilling control process(adjusting rotational and penetration rates)to achieve the optimal drilling parameter for different rock types was proposed.In this process,the ratio between specific energy and rock uniaxial compressive strength was used as the index to determine the optimal operation point.The recommended drilling operation range for the rock type used in the experiment was provided,and the reduction in respirable dust generation was demonstrated.By following this control process,the drilling efficiency can be monitored in real time,so the system can stay in a relatively high-energy efficiency with less respirable dust production from the drilling source.This algorithm is targeted to be incorporated into the current roof bolter drilling control system for drilling automation so that a safe and productive drilling operation can be conducted in a healthy working environment.

Migration law of respirable dust on a super-long fully mechanized double-shearer working face

In order to understand the migration law of respirable dust and gain reasonable design parameters for dust control on a super-long double-shearer fully mechanized working face, this paper describes research carried out using a numerical simulation package(Fluent) based on gas-solid coupling dispersed multiphase flow model and field measurement to research different technology modes, dust distribution law at different intervals where shearers work in opposite directions on the lower 9303 face, No. 2 Jining Mine,Yankuang Coal Mining Co. Results show that the concentration of dust 3–6 m away from the shearers working in the same directions was large, while the impact area of respirable dust near the shearer increased significantly to 5–6 m with the distance between two shearers working in opposite directions.The concentration of dust on a double-shearer face was considerably higher than that of a face with one shear under the combined effect of wind speed on the face and disturbed wind around the shearer, while the dust concentration near the shearer on the return side was considerably higher than that on the inlet side. The concentration of dust on a double-shearer face along the airflow declined slowly so that dust was hard to control. Simulation results confirmed the results of field measurement, which could provide reference for dust prevention design.

Association between Respirable Dust Exposure and Respiratory Health Concerns among Workers in Apparel Processing Companies in Export Processing Zone (EPZ) in Machakos County, Kenya

Apparel processing is an essential industry in providing clothing needs for the population. The Export Processing Zone (EPZ) in Kenya employs many employees. Garment processing releases respirable dust particles, thus exposing workers to risks to the respiratory system. The study determined the respirable dust health concerns among workers in Apparel Processing Companies (APCs) in EPZ in Machakos County, Kenya. A cross-sectional descriptive design was employed where four companies were studied. Three hundred and sixty-seven participants were selected through systematic random sampling. Data was collected using questionnaires and Interview guides. The study established that workers were exposed to respirable dust PM2.5 ranging from 40.89 ± 24.0 μg·m−3 to 87.49 ± 45.2 μg·m−3 with a mean of 65.61 ± 31.5 μg·m−3. While PM2.5 ranged from 63.59 ± 21.2 μg·m−3 to 313.41 ± 468.0 μg·m−3. With a mean of 104.02 ± 26.0 μg·m−3. Workers complained of different respirable dust-related diseases. The most prevalent conditions were sneezing and coughing (86.4%), chest pains (41.1%), blocked chests (36.8%), and allergic reactions to dust (18.3%). The APC should develop an OSH management system that includes;a dust management policy, dust monitoring, Risk Assessments, Engineering controls installations, medical examination, Training on dust management, PPE provision, and use enforcement.

Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

Field study results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control

A 3rd generation roof bolter canopy air curtain(CAC)has been developed and constructed by J.H.Fletcher&Co.,Inc.As with the previous generation of the CAC,this design uses the principle of providing uniform airflow across the canopy area as recommended by the National Institute for Occupational Safety and Health.The new modifications include a plenum that is constructed of a single flat aluminum plate,smaller-diameter airflow openings,and a single row of perimeter nozzles designed to prevent mine air contaminated by respirable dust from entering the CAC protection zone.Field testing was conducted on this new 3rd generation design showing reductions in coal mine respirable dust exposure for roof bolter operators.Dust control efficiencies for the CAC for the left bolter operator(intake side)ranged from approximately 26%–60%,while the efficiencies for the CAC for the right bolter operator(return side)ranged from 3%to 47%.

Chemistry and particle size distribution of respirable coal dust in underground mines in Central Eastern Europe

Despite international efforts to limit worker exposure to coal dust,it continues to impact the health of thousands of miners across Europe.Airborne coal dust has been studied to improve risk models and its control to protect workers.Particle size distribution analyses shows that using spraying systems to suppress airborne dusts can reduce particulate matter concentrations and that coals with higher ash yields produce finer dust.There are marked chemical differences between parent coals and relatively coarse deposited dusts(up to _(500)μm,DD_(500)).Enrichments in Ca,K,Ba,Se,Pb,Cr,Mo,Ni and especially As,Sn,Cu,Zn and Sb in the finest respirable dust fractions could originate from:(i)mechanical machinery wear;(ii)variations in coal mineralogy;(iii)coal fly ash used in shotcrete,and carbonates used to reduce the risk of explosions.Unusual enrichments in Ca in mine dusts are attributed to the use of such concrete,and elevated K to raised levels of phyllosilicate mineral matter.Sulphur concentrations are higher in the parent coal than in the DD_(500),probably due to relatively lower levels of organic matter.Mass concentrations of all elements observed in this study remained below occupational exposure limits.

Surface characteristics and wetting mechanism of respirable coal dust

In this study,FTIR and XPS spectroscopy,specific surface area and pore size analyses,wetting and other experimental means have been applied to investigate respirable coal dust surface properties and wetting mechanism.The research shows that coal dust surface structures,chemical and element compositions are changed in the refining process of coal dust.Compared with large particle coal dust,respirable coal dust is a weak hydrophilic and strong hydrophobic substance.The reason:the smaller the particle size of coal dust,the more unsaturated its surface.The absorption of air is strong and it is easy to form an air film on coal dust surfaces. Coal dust contact with water is actually a compound contact of liquid in contact with a solid and gas in contact with a solid. The smaller the particle size,the larger the pore volume and the higher the degree of surface roughness,the larger the area of gas in contact with a solid and the worse the coal dust wettability.Another reason is that the changes in the composition of atoms on the dust surface and structures affect coal dust wettability.The results of this study establish a theoretical basis for the invention of effective reduced-dust technology.

A systematic review of occupational exposure to respirable coal mine dust(RCMD)in the U.S.mining industry

Cumulative inhalation of respirable coal mine dust(RCMD)can lead to severe lung diseases,including coal worker's pneu-moconiosis(CWP),silicosis,mixed dust pneumoconiosis,dust-related diffuse fibrosis(DDF),and progressive massive fibrosis(PMF).Statistics from the number of reported cases showed a significant decrease in the progression of respiratory diseases in the 1990s.However,an unexpected increase in the number of CWP cases was reported in the late 1990s.To date,there has been no comprehensive systematic review to assess all contributing factors to the resurgence of CWP cases.This study aims to investigate the effects of various mining parameters on the prevalence of CWP in coal mines.A systematic review using the preferred reporting items for systematic reviews and meta-analysis(PRISMA)method was conducted to investigate the health effects of RCMD exposure and identify the factors that may contribute to the recent resurgence of CWP cases.The systematic review yielded a total of 401 papers,which were added to the database.The total number of 148 and 208 papers were excluded from the database in the process of screening and eligibility,respectively.Then,18 papers were considered for data selection and full-text assessment.The review revealed that factors including geographic location,mine size,mining operation type,coal-seam thickness,coal rank,changes in mining practices,technology advancement,and engi-neering dust control practices are contributing to the recent resurgence of CWP among coal workers.However,the evidence for root causes is limited owing to the methodological constraints of the studies;therefore,further detailed studies are needed.

Preliminary Characterization of Respirable Rock Dust Generated from Cutting Potash in Laboratory Full-Scale Tests with Radial Picks at Different Stages of Wear

Airborne rock dust poses serious long-term health effects to workers in mining and tunneling underground rock environments.When inhaled,respirable crystalline silica particles commonly found in quartz and other minerals will scar sensitive lung tissue and cause irreversible lung diseases.Characteristics such as concentration,type of mineral,particle size,and particle shape can harm workers to various extents.Therefore,this study characterizes airborne rock dust particles that are released from mechanically cutting rock.Laboratory full scale linear cutting tests on samples of potash rock were performed with radial picks to generate dust and were collected with various instruments,including Dorr-Oliver cyclones.Three stages of pick wear were tested:new,moderately worn,and severely worn.Comparisons between different stages of pick wear to dust concentration,size distribution,and particle shape characteristics are drawn from this preliminary study using analytical methods,field-emission scanning electron microscope image capture techniques,and laser diffraction.Although further testing needs to be conducted to make viable and concrete conclusions,a review of the test results reveals a strong tendency in generated airborne and deposited dust to be linked to the bit tip wear,which was influenced by tip surface area geometry,such as a sharp tip,blunt tip,or undulating sharp tips.The moderately worn pick,or the pick with the bluntest tip,in these experiments released the highest concentration of dust.The moderately worn(bluntest)pick also generated particle shapes with the highest aspect ratio compared to the other two picks.Additionally,in terms of the particle size distributions,all the picks generated airborne particle size mean values between 0.7 and 1.2µm in aerodynamic diameter.As for deposited particle size distributions,all the picks generated particles with the mode of particle aerodynamic diameter sizes at 13µm.In the end,the results of this preliminary study paired with future testing can confirm and eventually provide the basis for optimum bit management and maintenance systems to control airborne dust exposures.

Laboratory results of foam application testing for longwall shield dust control in a simulated environment

There were 37 longwall faces operating in mines in the United States in 2019.The average panel width for these longwalls was approximately 368.5 m(1209 ft).This translates to a range of approximately 170-240 shields per longwall,depending upon the width of shield.The movement of longwall shields is a significant contributor to respirable dust overexposures to longwall operators.Foam is expected to have the potential to reduce this shield dust generation.The foam is applied to the area on the roof between the coal face and the shield tip after the shearer passes.In this study,the longwall shield dust simulator was used to test three foam agents for their ability to control dust from longwall shield movements.Results showed that at low-velocity ventilation(≈3.0 m/s(600 fpm))all foam agents were able to produce dust reduction levels of at least 45%.At high-velocity ventilation(≈5.1 m/s(1000 fpm)),the reductions were lower and more variable,ranging from being undeterminable for one foam agent to having 46%-63%reductions for the other two foam agents,with one instance of an increase in dust concentration.Overall,the use of foam agents can provide longwall shield dust control.Important factors are roof coverage and the ability of foam to remain on the roof for extended time periods.

Research on Distribution Regularities of Dust Concentration and Granularity in Large Mining Height Working Face

The key for dust control of coal mine is to clarify the dust concentration distribution and sedimentation in different areas. Both similarity experiment and numerical simulation method have certain restrictions and are quite different from the actual situation on site. In order to study the dust sedimentation regularity of coal mine in large mining height, “filter membrane method” is adopted in this paper, i.e., to dry and weigh the filter membrane before and after sampling, collect the dust of respirable zone on mining face and calculate the dust concentration based on a main airway of 100 m. The result shows that: A large amount of dust will be produced during coal mining, wherein the maximum dust concentration from 6 m upstream to 100 m downstream of coal cutter is 121 mg/m3, while the minimum dust concentration is 61 mg/m3;The dust concentration in return airway is reduced with the distance increases, while the dust concentration at the entrance is 91 mg/m3;A large amount of dust may fall from roof during section advancing and improves the dust concentration of hydraulic support in walking area obviously;The dust granularity of mining face and return airway is 0 - 100 μm, but the amount of respirable dust is higher than 80%, the larger the dust particle size, the higher the dust concentration. Besides, dust in small particle size can be suspended in air flow for longer, but that in large particle size may subside under the action of gravity;To reduce dust exposure, the mining position shall be located in the windward direction of advancing or coal cutter. This research can provide guidance for taking dust prevention measures of working face in large mining height.

Diesel engine exhaust exposures in two underground mines

Exposure to diesel engine exhaust(DE) is a major concern in underground mines. It has been linked to cardiopulmonary diseases and is classified as a human carcinogen. The goal of this study is to assess DE exposures in workers at two underground gold mines, to compare exposure levels within and between the mines, and to compare different methods of measuring DE exposures, namely respirable combustible dust(RCD), elemental carbon(EC) and total carbon(TC). Ambient and personal breathing zone(PBZ) measurements were taken. Side-by-side monitoring of RCD and of the respirable fraction of EC and TC(EC_Rand TC_R) was carried out in the workers' breathing zone during full-shift work.Regarding ambient measurements, in addition to EC_R, TC_Rand RCD, a submicron aerosol fraction(less than 1 mm) of EC and TC was also sampled(EC_1and TC_1). Average ambient results of 240 mg/m^3 in RCD, 150 mg/m^3 in EC_Rand 210 mg/m^3 in TC_Rare obtained. Average PBZ results of 190 mg/m^3 in RCD,84 mg/m^3 in EC3Rand 150 mg/min TC_Rare obtained. Very good correlation is found between EC_Rand EC_1 with a Pearson correlation coefficient of 0.99(p < 0.01) calculated between the two logtransformed concentrations. No differences are reported between EC_Rand EC_1, nor between TC_Rand TC_1, since ratios are equal to 1.04, close to 1, in both cases. Highest exposures are reported for loadhaul-dump(LHD) and jumbo drill operators and conventional miners. Significant exposure differences are reported between mines for truck and LHD operators(p < 0.01). The average TC_R/EC_Rratio is 1.6 for PBZ results, and 1.3 for ambient results. The variability observed in the TC_R/EC_Rratio shows that interferences from non-diesel related organic carbon can skew the interpretation of results when relying only on TC data.

An analysis of contributing mining factors in coal workers’pneumoconiosis prevalence in the United States coal mines,1986-2018

In the United States,an unexpected and severe increase in coal miners’lung diseases in the late 1990s prompted researchers to investigate the causes of the disease resurgence.This study aims to scrutinize the effects of various mining parameters,including coal rank,mine size,mine operation type,coal seam height,and geographical location on the prevalence of coal worker’s pneumoconiosis(CWP)in surface and underground coal mines.A comprehensive dataset was created using the U.S.Mine Safety and Health Administration(MSHA)Employment and Accident/Injury databases.The information was merged based on the mine ID by utilizing SQL data management software.A total number of 123,589 mine-year observations were included in the statistical analysis.Generalized Estimating Equation(GEE)model was used to conduct a statistical analysis on a total of 29,707,and 32,643 mine-year observations for underground and surface coal mines,respectively.The results of the econometrics approach revealed that coal workers in underground coal mines are at a greater risk of CWP comparing to those of surface coal operations.Furthermore,underground coal mines in the Appalachia and Interior regions are at a higher risk of CWP prevalence than the Western region.Surface coal mines in the Appalachian coal region are more likely to CWP development than miners in the Western region.The analysis also indicated that coal workers working in smaller mines are more vulnerable to CWP than those in large mine sizes.Furthermore,coal workers in thin-seam underground mine operations are more likely to develop CWP.