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ENGINEERING DIVISION

MINERAL PROCESSMENT ENGINEERING COURSE

ACADEMIC YEAR 3

ENGLISH V

Class A

Topic: Toxic Gases On the Mines in Mozambique Moatize Student  Filipe Sitole Professor:  dr. Colasso Tete, 06-

1.Introduction Toxic gases are produced when the drill-and-blast method is used to excavate underground infrastructures. The noxious gases released immediately after blasting are mainly carbon monoxide (CO) and nitrogen oxides (NOx) [1]. These gases must be diluted and removed to provide a safe working environment for the workers. Therefore, a suitable ventilation system is required to reduce the concentration of the gases below the threshold limit value (TLV) according to health and safety regulations [2]. The safe re-entry time mainly depends on the ventilation system employed, the ventilation airflow and the distance from the working face to the tunnel outlet [3]. Forced ventilation is normally used in tunneling construction [4]. However, there are other ventilation systems that can also be used to reduce the re-entry times. Researchers have previously analyzed the migration of toxic gases generated to determine the safe re- entry time after blasting. Computational fluid dynamics (CFD) modeling is typically used by researchers to predict the concentration–time curves of the noxious gases after blasting in underground excavations. Huang et al. [3] analyzed the evolution of the CO concentration after blasting in a copper mine. They considered a forced ventilation system in a 15 m2 mining tunnel under different working conditions and concluded that the distance between the mouth of the ventilation duct and the working face, as well as the ventilation airflow, influences the dispersion coefficient of the toxic gases in the tunnel. Bahrami et al. [5] developed an advection–dispersion transport model to evaluate the safe re-entry time after blasting using a gas-monitoring system in the return of the ventilation system in a limestone mine. They concluded that the installation of a monitoring gas system can be used to reliably determine the safe re-entry time of the workers after blasting. Torno et al. [6] developed conventional and CFD numerical models to explore the migration of the blasting fumes in a coal mining heading. They validated the numerical results with field measurements to study the safe re-entry time of the miners to the heading face. Feng et al. [7] numerically analyzed the dynamic diffusion of CO after blasting in a high-altitude tunnel using forced ventilation. They concluded that the time required to reduce the CO mass fraction increases when the underground infrastructure is located in high-altitude environments.

To improve the mining cycle, mathematical and empirical models have also been used by researchers to investigate the propagation of blasting fumes and the re-entry times after blasting operations [11,12]. Agson Gani et al. [13] developed a study to determine the re-entry time after blasting in an underground gold mine. They analysed the dispersion of the CO, the diffusion coefficient and the mine ventilation system at different locations. Sirait et al. [14] studied the effective advection–diffusion coefficient to evaluate the time required to remove the toxic gases after blasting using gas detectors in an underground mine. Gillies et al. 1.2.Background of the study Moatize district located in Tete province in the center of Mozambique has one of the largest unexploited coal deposits of the world with a capacity of 2.5 billions of tones. Recently many multinational coal mine companies started exploitation of coal in Moatize. Coal exploitation has economical, social and environmental impacts. The main environmental impact is generation of acid mine drainage (AMD) which can pollute surface and groundwater. The aim of this work was to describe and assess the main impact of mining activities on water resource in Moatize and to describe treatment methods for polluted water. The methodology used was literature review and visits realized in different institutions of Mozambique. Different active and passive methods for AMD were described throughout the report. can be conclude that the impact of AMD in Moatize will not significantly affect the Zambezi river due to its big flow but it can be severe in small tributaries because some of them pass through the mining section. Water pollution can affect the population of Moatize negatively because they depend in agriculture and fishing to survive. There were not enough data to decide which treatment method can be applied for Moatize, but based on data from an old mine from Moatize it was possible to conclude that aerobic wetland and lime-limestone neutralization could be used. It is recommended to collect extensive data from mining companies in Moatize to make more detailed investigation about different treatment method.

Which techniques can be held in order to settle this hazardous environmental protection against gases? 1.3.2. Objectives 1.3.4.General objective  To analyse the main impacts caused by ventilation and toxic gases in mining activities sectors. 1.3.5. Specific objectives  To define ventilation and toxic gases  To identify the major of this phenomenon  To describe the impacts such as positive and negative one gases and ventilation. Purpose of the study As we have seen in our country and this community we have seen many people doing what's wrong in our community, I personally have the privilege to conduct this work and my main purpose boa to find out what are the Main problems related to the study. Limitations of the study I had some great limitations m such as books and articles that refer about the ventilation specifically in moatize district. 2.Delimitations of the study The study was delimited only in moatize mining company and around the area 2.1.Limitations of the study I had some great limitations m such as books and articles that refer about the ventilation specifically in moatize district.

2.1.2.Methodology According to LAKATOS 2005, methodology is the way an investigator or researchers do in order to find out some information. Procedures This project conducted mainly two principal: Observations Direct: the researcher goes to the the field and sees by himself the field. Indirect: the researcher doesn't go to the field but only takes what was taken into consideration previously. Experiments Bibliographic: this method is more concerned about researching the books and some articles that's says about it. Definition of the terms What is ventilation? Definitions covering ventilation and the flow of air into and out of a space include: Purpose provided (intentional) ventilation: Ventilation is the process by which ‘clean’ air (normally outdoor air) is intentionally provided to a space and stale air is removed. This may be accomplished by either natural or mechanical means. Air infiltration and exfiltration: In addition to intentional ventilation, air inevitably enters a building by the process of ‘air infiltration’. This is the uncontrolled flow of air into a space through adventitious or unintentional gaps and cracks in the building envelope. The corresponding loss of air from an enclosed space is termed ‘exfiltration’. The rate of air infiltration is dependent on the porosity of the building shell and the magnitude of the natural driving forces of wind and temperature. Vents and other openings incorporated into a building as part of ventilation design can also become routes for unintentional air flow when the pressures acting across such openings are dominated by weather conditions rather than intentionally (e.g. mechanically) induced

If you work in an office or shop, natural ventilation will normally be enough to control dusts and vapours from cleaning materials etc Sometimes planned, powered general ventilation is an integral part of a set of control measures, eg the welding of large fabrications in a workshop Local exhaust ventilation Local exhaust ventilation (LEV), or extraction, is an engineering control solution to reduce exposures to dust, mist, fume, vapour or gas in a workplace Use a properly designed LEV system that will draw dust, fume, gases or vapour through a hood or booth away from the worker An extraction system should be easy for workers to use and enclose the process as much as possible It should effectively capture and contain the harmful substance before it is released into the working environment Air should be filtered and discharged to a safe place The system should be robust enough to withstand the process and work environment. It is important to maintain it and undertake tests to ensure it is working effectively Things to avoid when applying LEV Common errors in applying extraction are:  the effectiveness of small hoods is usually overestimated – be realistic  the hood is usually too far away from the process  the hood doesn't surround the process enough  inadequate airflow  failure to check that the extraction continues to work  workers are not consulted, so they don't understand the importance of extraction and do not use it properly

3.CHAPTER III

3.1.LITERATURE REVIEW

Toxic gases are gases with hazardous physiological effects when inhaled. The National Fire Protection Association, classified gases into four classes based on the LC50. The most hazardous highly-toxic gases are rated Class 4, hazardous toxic gases are rated Class 3 and moderately-toxic gases are rated as Class 2 hazardous gases while in GHS the escalation is inverted as shown below. regulators, valves and lines must be chemically compatible with the gases being used

• Pressurized gas regulator and line system must be leak tested before use
• All regulators must be compatible with the size and type of gas cylinder 3 Reaction Vessel 4 Ventilation Line
• Reaction vessel or chamber must be located inside an exhausted enclosure like a fume hood
• Depending on the process and gas type, additional engineering controls may be required such as RFOs, gas detection systems, automatic shut-offs
• Purge vents must be connected to an exhaust system that discharges to a safe location
• Significant emissions of toxic gas needs additional treatment system such as scrubber and absorben.

5.References Santos, M. (1996). A natureza do espaço. Técnica e tempo. Razão e emoção. São Paulo, Hucitec. 4 Appadurai, A. (2004). The Capacity to Aspire: Culture and the Terms of Recognition. In V. Rao, & M. Walton (eds.), Culture and Public Action: A Cross-Disciplinary Dialogue on Development Policy. Palo Alto, Calif.: Stanford University Press. 5 Rao, V., & Walton, M. (2004). Culture and Public Action: An Introduction. In V. Rao, & M. Walton (eds.), Culture and Public Action: A Cross-Disciplinary Dialogue on Development Policy. Palo Alto, Calif.: Stanford University Press. Census (2007). Indicadores Sociodemográficos Província de Tete 2007. Instituto Nacional de Estatística, Gabinete Central do Recenseamento, Maputo, Mozambique. Retrieved on September 25th, 2021 from http://www.ine.gov.mz/operacoesestatisticas/censos/censo-2007/rgph-2007/indicadores- socio-demograficos-provincia-de-tete-2007.pdf/view De Meulder, B., & Wambecq, W. (orgs.). (2018). Resilient Zambezi Landscape urbanism studio: designing resilience in an era of drastic transformation. Studio Investigation Series. Leuven: KU Leuven, Department of Architecture. De Meulder, B., & Shannon, K. (2018). Designing Ecologies for Resilient Urbanisms. Landscape Architecture Frontiers, 6(5), 12-33. https://doi.org/10.15302/J-LAF- De Meulder, B., Shannon, K., & Wambecq, W. (2019). Settling with and within an Open Canopy Forest: a Landscape Urbanism Proposition for the Semi-arid Savannah of the Lower Zambezi River Basin around Tete (Mozambique). Folio Radical Development. Radical Noir, 47-69. Gibbens, M., & Schoeman, C. (2020). Planning for sustainable livelihood development in the context of rural South Africa: A micro-level approach. Town and Regional Planning, 76, 14-28.

[1] Inquiry into nursing home deaths, BBC 2005, Viewed 30/5/ http:/news.bbc.co.uk/1/hi/Scotland/3448091.stm. [2] Andrews, G.E., Ledger, J., and Phylaktou, H.N., “Enclosed Pool Fire Flame Temperatures and Global Heat Loss Using Gas Analysis,” Sixth International Symposium on Fire Safety Science, 1999. [3] BS 5588-4:1998 “Fire Precautions in the Design, Construction, and Use ofBuildings.” [4] Andrews, G.E., Ledger, J., and Phylaktou, H.N., “Pool Fires in a LowVentilation Enclosure,” I.Chem.E. Symposium on Hazards XV, I.Chem.E. Symposium Series, No. 147, 2000, p.147-183. [5] Andrews, G.E., Ledger, J., and Phylaktou, H.N., ‘The Gravimetric Determination of Soot Yields in Enclosed Pool Fires,” Proc. 3rd International Colloquia on Explosions in Reactive Systems, Windermere, 2000. [6] Sugawa, O., Kawagoe, K., and Oka, Y., “Burning Behavior in a Poor-ventilation Compartment Fire – Ghosting Fire,” Nuclear Engineering and Design, 125, p. 347-352,

[7] Peatross, M.J., and Beyler, C.I., “Thermal Environment Prediction in Steel Bounded Preflashover Compartment Fires,” Proc. Fifth Int. Symp. On Fire Safety Science, 1997, p. 415-426. [8] Audounin, I., Such, J.M., Malet, J.C., and Casselmann, C., “A Real Scenario for a Ghosting Flame,” Proc. Fifth Int. Symp. on Fire Safety Science, 1997, pp. 1261-1272.