rasiel reseach

INVESTIGATION AND MODERATION OF UNDERGROUND DUST EMISSION

AT TANZANITE ONE MINING COMPANY IN MANYARA REGION

Rasiel Robert

Reg no. 810 MID 12

Advance Diploma in Environmental Engineering and Management in Mines

Mineral Resources Institute

May, 2015

INVESTIGATION AND MODERATION OF UNDERGROUND DUST EMISSION

AT TANZANITE ONE MINING COMPANY IN MANYARA REGION

By

Rasiel Robert

Advance Diploma in Environmental Engineering and Management in Mines

A Project work Submitted in Partial Fulfillment of the

Requirements for the Advance Diploma in Mining Engineering of the Mineral

Resources Institute

Mineral Resources Institute

May, 2015

i

CERTIFICATION

The undersigned certify that they have read and hereby recommend for acceptance by the

Mineral Resources Institute a project work titled: Investigation and Moderation of

Underground Dust Emission at Tanzanite One Mining Company at Manyara Region in

fulfillment of the requirements for the Advance Diploma in Environmental Engineering and

Management in Mines of the Mineral Resources Institute.

FRANK PAUL

Prof/Dr/Mr./ Ms /Eng.

(Supervisor)

Date: …………………………………

MKANGO

Prof/Dr/Mr./Ms/Eng.

(Head of Department)

Date: ……………………………...

J. MAKENA

Prof/Dr/Mr./Ms.

(Project Coordinator)

Date…………………………….

ii

DECLARATION AND COPYRIGHT

I, Rasiel Robert, declare that this thesis is my own original work and that it has not been

presented and will not be presented to any other Institute/Learning Institution for a similar or

any other Advance diploma award.

Registration Number

……………………...

Signature

……………………

Date

………………………

Signature------------------------------------------

This project work is copyright material protected under the Berne Convention, the Copyright

Act 1999 and other international and national enactments, in that behalf, on intellectual

property. It may not be reproduced by any means, in full or in part, except for short extracts

in fair dealings, for research or private study, critical scholarly review or discourse with an

acknowledgement, without the written permission of the Unit of Research, Consultancy and

Short courses, on behalf of both the author and the Mineral Resources Institute

iii

ACKNOWLEDGEMENT

I would like to give the glory and honor to my almighty God for giving me hope in times of

adversity, piece in times of chaos, serenity in time of trials and endless source of grace,

courage and strength to step into the unknown every time the going got through. Without

God my Labor would be in vein. I thank him for being the source of my success.

I would like to thanks my family for their financial supporting provided to me during

industry practical training, God bless them for their support to me, I really appreciate the

support.

I would like to thank the whole management and staff of Tanzanite mining company for their

support gave me during the period of conduct my project, they cooperate with me in

perpendicular way, much thanks for them.

Finally I would like to thanks the management of Mineral Resource Institute for their effort

applied toward my project, I really appreciate their effort, also much thanks for their

academic support for us student.

iv

DEDICATION

I would like to dedicate this project work to my family members, staffs of mineral resource,

ministry of energy and minerals institute, and my school mate at mineral resource institute

v

ABSTRACT

Underground Tanzanite mining operations in Mirelani continue to increase productivity as

mining equipment and practices are improved. Unfortunately, increased production also

results in the potential for increased respirable dust generation and worker exposure. In

response, Company operations are applying basic controls at elevated levels and looking to

emerging technologies in an effort to better control respirable dust levels.

Ventilating air and water sprays remain the basis of dust control strategies for both working

and continuous mining operations, and the level of application for these controls continues to

increase. In addition, new technologies are emerging that have the potential to further reduce

dust levels. From the study has been conducted to find out the factor which affect tanzanite

production and came out with the problems of dust emission during underground mining

activities, and therefore to introduce a method of moderating the problems of dust emission.

This thesis consists of introduction, problem statement, objective and methodology, data

collection and data interpretation, conclusion and recommendation, which will be a simple

summary of this thesis.

vi

TABLE OF CONTENTS

CERTIFICATION ................................................................................................................... i

DECLARATION AND COPYRIGHT .................................................................................. ii

ACKNOWLEDGEMENT ..................................................................................................... iii

DEDICATION ........................................................................................................................ iv

ABSTRACT ............................................................................................................................. v

TABLE OF CONTENTS ....................................................................................................... vi

LIST OF TABLES .................................................................................................................. ix

LIST OF FIGURES ................................................................................................................. x

LIST OF ABBREVIATIONS ................................................................................................ xi

CHAPTER ONE ...................................................................................................................... 1

1.0. INTRODUCTION ............................................................................................................ 1

1.1. General Introduction ....................................................................................................... 1

1.1.1 Location and Background ............................................................................................. 1

1.1.2 Location and Access ..................................................................................................... 2

1.1.3 General Geology of Tanzanite ...................................................................................... 3

1.1.4 Dust ............................................................................................................................... 4

1.2 Problem Statement ........................................................................................................... 4

1.3 Objectives ........................................................................................................................ 5

1.3.1 Main Objective ............................................................................................................. 5

1.3.2 Specific Objective ......................................................................................................... 5

vii

CHAPTER TWO ..................................................................................................................... 6

2.0. LITERATURE REVIEW ................................................................................................ 6

2.1.0 Dust ............................................................................................................................... 6

2.1.1 Emission of dusts .......................................................................................................... 7

2.1.2 Type of dust .................................................................................................................. 7

2.2.3 Grade of Dust ................................................................................................................ 8

2.1.4 Aim of Dust Control ..................................................................................................... 9

2.1.5 Importance to Control Dust in Underground Mines ................................................... 10

2.2.6 Effects of dust ............................................................................................................. 10

2.2.7 Effect of dust in water ................................................................................................. 10

2.2.8 Dust Moderation Methods .......................................................................................... 11

2.2.9 Airborne Dust Capture Systems method .................................................................... 11

2.3.0 Methods of Atomization ............................................................................................. 13

2.3.1 Chemical Additives to Control Droplets .................................................................... 14

2.3.2 Wet Dust Suppression ................................................................................................. 15

CHAPTER THREE .............................................................................................................. 18

3.0 METHODOLOGY .......................................................................................................... 18

3.2. Dust data collection. ..................................................................................................... 18

3.3 Dust sampling ................................................................................................................ 18

CHAPTER FOUR ................................................................................................................. 20

4.0 DATA COLLECTION, ANALYSIS AND INTERPRETATION .............................. 20

4.1 Data Collection and Analysis ........................................................................................ 20

viii

4.2. Data Interpretation ........................................................................................................ 24

CHAPTER FIVE ................................................................................................................... 28

5.0 RESULTS AND DISCUSSION ...................................................................................... 28

CHAPTER SIX ...................................................................................................................... 29

6.0 CONCLUSION AND RECOMMENDATION ............................................................. 29

6.1. Conclusion .................................................................................................................... 29

6.2 Recommendation ........................................................................................................... 29

REFERENCES ...................................................................................................................... 30

APPENDICES ....................................................................................................................... 31

ix

LIST OF TABLES

TABLE page

Table 1: Table show data of test # 1 ........................................................................................ 20




x

LIST OF FIGURES

FIGURE page

Figure 1: Location of Tanzanite one mining company ......................................................... 1

Figure 2: Location of Tanzanite one mining the four blocks ................................................ 2

Figure 3: Sketch map showing gemstone mineralization in the Mozambique belt

of Tanzania ............................................................................................................ 3

Figure 4: Dust emission ......................................................................................................... 7

Figure 5: It show the size of the particle that grouped according to the human

threats ..................................................................................................................... 9

Figure 6: Collision between dust particle and water droplets ............................................. 12

Figure 7: Effect of droplet size on dust particle impingement ............................................ 13

Figure 8: Contact angle resulting from a liquid meeting a solid surface............................. 14

Figure 9: The use of water to suppress dust ........................................................................ 16

Figure 10: Sleap stream effect ............................................................................................... 17

Figure 11: Components of dust collection system ................................................................ 19

xi

LIST OF ABBREVIATIONS

Abbreviations Meaning

MEM Ministry of Energy and Minerals

MRI Mineral Resources Institute

Ca2Al2O.AlOH[Si2O7][SiO4] Zoisite

ACGIH American Conference of Governmental Industrial

Hygienists

BOHS British Occupational Hygiene Society

IPT Industrial Practical Training

STAMICO State Mining Corporation

KIA Kilimanjaro international airport

TGI Tanzania Gemstone Industries Ltd

NEMC National Environmental Management Council

NE North East

PPM Particle per million

H2O Water

CH4 Methane

H2S Hydrogen sulphate

N2 Nitrogen gas

θ Angle

1

CHAPTER ONE

1.0. INTRODUCTION

1.1. General Introduction

1.1.1 Location and Background

Tanzanite one Mine company is an underground mine located in Manyara Region northeast of

Tanzania, 16kilometers from Kilimanjaro international airport (KIA). It was discovered in the

Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and

Mount Kilimanjaro. Tanzanite One Mining Ltd is owned by Richland Resources, but a 2010 law

in Tanzania required them to cede 50% ownership of their mining license to the Tanzanian State

Mining Company (STAMICO).Tanzanite is a trade name that was first used by Tiffany and

Company for gem-quality specimens of the mineral zoisite (Ca2Al2O.AlOH[Si2O7][SiO4]) with

a blue color. Tiffany could have sold the material under the mineralogical name of blue zoisite

but they thought the name Tanzanite would stimulate customer interest and be easier to market.

Figure 1: Location of Tanzanite one mining company

2

Various individuals have been credited with the discovery of Tanzanite including Manuel

D’Souza and Ali Juuyawatu who came across the then unknown blue mineral in 1967 He shared

his find with Manuel D’Souza, a tailor by profession and prospector by passion, who was

looking for rubies in the region. From 1968 to 1971, Ali Juuyawatu, a farmer, started mining in

the area now known as Block C and the government nationalized all mining activities were

putted under the control of Tanzania Gemstone Industries Ltd (TGI), in 1972 the State Mining

Corporation (STAMICO) was formed and took over control of TGI until 1983.

In 1990 the government divided the area into four main blocks Block C was awarded to

Graphtan Ltd, predominantly focused on mining graphite, at the end of 1998, AFGEM Ltd was

issued a prospecting license for the Block C and later in 2001 acquired a mining license.

Figure 2: Location of Tanzanite one mining the four blocks

Tanzanite one mining company consists of a process plant, waste rock dumps, tailing

containment, water management ponds, and associated facilities.

1.1.2 Location and Access

Tanzanite is mined in vicinity of Mirelani a mining village situated on the west flank of the

Lelatema mountain range in Tanzania East Africa as show in ( Figure 1) situated 16km south

east of Kilimajaro international airport. The deposit is situated between latitude 30,33

’’ and 3

0

3

33’’5

’S and longitude 36

0 57

’’ and 37

0 4

’’E the nearest Arusha and Moshi accessible from mine

via a 16km dirt road to Kilimanjaro international airport followed by 45km stretch of tar road.

1.1.3 General Geology of Tanzanite

The Proterozoic (1900-700 Ma) lithostratigraphic units within the Mozambique Belt of Tanzania

stretch in a N-S direction east of the Tanzanian Craton and are known to host most of the

coloured gemstones. This paper concentrates on the Merelani Tanzanite mining area lying near

the contact between the volcanic and the high-grade metamorphic rocks of the Mozambique Belt.

Figure 3: Sketch map showing gemstone mineralization in the Mozambique belt of Tanzania

1) Longido, 2) Manyara, 3) Babati, 4) Merelani, 5) Lelatema, 6) Tiriri, 7) Landanai, 8) Umba, 9)

Mvuha, 10) Magogoni, 11) Namaputa, 12) Nabunju, 13) Sumbawanga,14) Mpwapwa, 15) Kilosa

and 16) Loliondo (After Malisa and Muhongo 1990).

4

The supracrustal rocks in the Merelani area very similar to the rocks found elsewhere in the

Mozambique Belt, consisting of psammitic, pelitic and psammo-pelitic gneisses, crystalline

limestones, and to a lesser extent granite pegmatites and quartz veins. After the main phase of the

Pan African tectonothemal event, these rocks have in some areas suffered alteration as reflected

in their chemical and mineralogical composition as a result of the hydrothermal processes.

The mineralization lies within the hydrothermally altered zone along the Lelatema fault zone

with a northerly plunging regional scale fold structure. High quality blue zoisite (tanzanite)

occurs in boudinaged quartz veins within the graphiterich hydrothermally altered gneisses.

However, honey- yellow coloured with other colours may also be found outside the boudinaged

structures. Inhalation of graphitic dust and silica particulates is the main problem miners face

during extraction of the gems from the host rocks. Detailed studies on the geology of Merelani

area is discussed by Malisa (1987) while the paragenesis of tanzanite, its crystallographic

structure, mode of occurrence, the tectonic setting are described by Malisa and Koljonen (1986),

Sundberg et al. (1988), Malisa and Muhongo (1990), respectively.

1.1.4 Dust

Are the solid particles that are suspended in air, or have settled out onto a surface after having

been suspended in air. The terms dust and particulate matter (PM) are often used fairly

interchangeably, although in some contexts one term tends to be used in preference to the other.

1.2 Problem Statement

Tanzanite one mining has been facing a problem of underground dust emission during the

mining activities. This is due to failure of dust moderation, poor control systems and inadequate

method of dust suppression. The aim of this project is to investigate the amount of dust emission

during underground mining activities and techniques required to improving dust emission as to

meet international and national standards.

5

1.3 Objectives

1.3.1 Main Objective

The aim of this project is to examine the dust emission based on the principle of environmental

conservation consequently to moderate the amount of dust emitted and leave the working area

safe.

1.3.2 Specific Objective

i. To establish airborne dust capture systems method basing on the particle size emitted

ii. To use of wet dust suppression method with standard calibrated horse pipes

iii. To conduct Dust Collection techniques

6

CHAPTER TWO

2.0. LITERATURE REVIEW

2.1.0 Dust

Dust is the general name for minute solid particles of a diameter of less than 500 micrometers. In

construction, destruction, and renovation situations, dust of differing sources poses a serious and

recognized health risk to workers causing acute and chronic diseases such as silicosis and

asbestosis. In addition to the health risk, dust emission also poses a threat with its ability in some

sectors to be flammable.

From the British Occupational Hygiene Society (BOHS) Technical Committee studied the "dust

yield" defined as "the mass of aerosol produced per mass of powder dropped" (BOHS, 1995). It

was shown that initially increasing the mass increases the dust yield, but a point is reached when

the dust produced per unit mass levels off and then decreases. Other studies Hazard Prevention

and Control in the Work Environment confirmed this (Breum, 1999), and one concluded that

"dust generation can be minimized by having powders fall as large, discrete slugs instead of a

stream of small clumps; slugs should be as large as possible to minimize the exposure of the

powder to the airflow" (Heitbrink et al., 1992). The explanation is that with higher material

flow, there is more material at the centre of the falling mass, and this central part is less exposed

to surrounding air, and hence less likely to disperse.

7

Figure 4: Dust emission

2.1.1 Emission of dusts

Most of dust at Tanzanite one emitted during drilling and blasting. Dust exposure is dependent

on the amount of dust emitted, which depends on the physical and chemical characteristics of the

material and the methods of handling of the material. Other causes of underground Dust

exposure at tanzanite one generally occurs during the following activities, Through the breaking

of ores by grinding for a simple transport to skip point, During drilling and blasting process

Drilling and during Loading and Mucking, Drilling & Bolting, Ore passes, Crushers, Backfill

Process.

2.1.2 Type of dust

Dust is produced in a very wide range of sizes. Larger, heavier particles tend to settle out of the

air and onto a surface and smaller, lighter particles have a tendency to hang indefinitely in the

air. There are two main types of dust that exist on a worksite like Fibrogenic dust, inert dust.

8

Fibrogenic dust: is so named because it is a kind of dust that has fiber like tendencies.

Fibrogenic dust is biologically toxic and if retained in the lungs can impair the lungs’ ability to

function properly.

Inert dust: is defined as any dust containing less than 1% of quartz content. Typically, and

health effects caused by inert dust are potentially reversible, as opposed to the Fibrogenic dust’s

more permanent effects. However, inert dust has the potential to incomprehensible visibility,

cause unpleasant deposits in exposed bodily orifices, and potentially injure mucous membranes

or the skin with some sort of chemical action.

2.2.3 Grade of Dust

Dusts are grouped according to its particle size. For occupational health purposes, dust is

classified by its size into the three categories of respirable dust, inhalable dust, and total dust.

Respirable dust; is the kind of dust that is small enough to penetrate deep into the lungs and

bypassing the nose, throat, and upper respiratory tract. It has size of less than 5µm or equals to

5µm, which is about 1/12th

the width of the average human hair.

Inhalable dust; is dust of a median size of 10 µm that is trapped in the nose, throat, and upper

respiratory tract. Total dust; it includes all airborne particles, without regard to size or

composition.

9

Figure 5: It show the size of the particle that grouped according to the human threats

2.1.4 Aim of Dust Control

Control systems are used to reduce dust emissions. Although installing a dust control system

does not assure total prevention of dust emissions, a well-designed dust control system can

protect workers and often provide other benefits, such as:-

Preventing and reducing risk of dust explosion or fire

Increasing visibility and reducing probability of accidents

Preventing unpleasant odors from blasting and other mining activities

Reducing cleanup and maintenance costs since of good ventilation from duct moderation

Reducing equipment wear, especially for components such as bearings and pulleys on

which fine dust can cause a "grinding" effect and increase wear or abrasion rates

Increasing worker morale and productivity because of the dust control in extent

Assuring continuous compliance with existing health regulations (NEMC or WHO)

Proper planning, design, installation, operation, and maintenance are essential for an

efficient, cost-effective, and reliable dust control system.

10

2.1.5 Importance to Control Dust in Underground Mines

Dust control is necessary due to health hazards, industrial problems and environmental problems.

Excessive dust emissions can cause such health issues as occupational respiratory diseases; eye,

nose, and throat pain or irritation; and skin irritation. In addition, dust is an industrial problem.

With its potential risk of dust explosions and fires, it can potentially damage worksite equipment,

it impairs visibility, it can cause unpleasant odors, and it is a potential problem in community

relations.

As far as health hazards to workers, this occurs when workers are exposed to excessive amounts

of harmful dusts. The harmfulness is dependent on the composition of the dust (i.e. chemical or

mineralogical), the concentration of the dust (either by weight or quantity of dust particles), the

size and shape of the particle (i.e. fibrous or spherical), and lastly, the exposure time.

2.2.6 Effects of dust

The investigation done at tanzanite one mining proves that most of the people admitted to the

company dispensary are suffered from dust exposure diseases. Both found with the lung problem

caused by the dusts. Dust from mining can make it difficult to breathe. Large amounts of dust

can make the lungs fill with fluid and swell up. Signs of lung damage from dust include: sore

throat, shortness of breath, fever, chest pain and loss of appetite

2.2.7 Effect of dust in water

The dust will possibly deposit in underground water bodies, such as river and underground

springs. It increase the sediment in the water body, the particle contain different types of metal it

can change the pH of the water bodies. The alteration of the pH will harm the underground living

organisms which are the biodiversity to our environment and which help in mineralogy process.

11

2.2.8 Dust Moderation Methods

There are so many dust control methods and it varies, based on budget, desired level of

effectiveness, and structural constraints these are:

To establish airborne dust capture systems method basing on the particle size emitted

To use of wet dust suppression method with standard calibrated horse pipes

To conduct Dust Collection techniques

2.2.9 Airborne Dust Capture Systems method

Airborne dust Capture systems work on the principle of spraying very small water droplets into

airborne dust. When the small droplets collide with the airborne dust particles, they stick to each

other and fall out of the air to the ground.

This collision between the particles occurs due the factors which involve both the water and the

dust particles. As a dust particle and water particle approach each other, the airflow could move

the particle around the droplet; have a direct hit on the droplet, or barely graze/abrasion the

droplet.

This factor leads to the second factor, in which droplets and particles of the same sizes have the

best chance of a collision (slipstream effect). If a droplet is smaller than the dust particle or vice

versa, then they may never collide and instead just be swept around each other.

The last factor is the dependence of an electrostatic force on a droplet and how the path is

affected by this force. Like with magnets, similar charged particles repel each others. Thus it is

advantageous to have the particles either both neutrally charged (so that they neither repel nor

attract one another) or oppositely charged (so that they attract one another) in order to increase

the likelihood of a water and particle collision.

In this approach, very fine water droplets are sprayed into the dust after it is airborne. When the

water droplets and dust particles collide, agglomerates are formed. When these agglomerates

become too heavy to remain airborne, they settle.

12

Figure 6: Collision between dust particle and water droplets

The collision between dust particles and water droplets occurs due to the following two factors:-

Impaction/interception and Droplet size/particle size

i. Impaction/Interception

When a dust particle approaches a water droplet, the airflow may sweep the particle around the

droplet depending on its size, trajectory, and velocity; the dust particle may strike the droplet

directly, or barely graze the droplet, forming an aggregate.

ii. Droplet size/particle size

Droplets and particles that are similar in size have the best chance of colliding. Droplets of water

which are smaller than dust particles or vice versa may never collide but just be swept around

one another particles.

13

Figure 7: Effect of droplet size on dust particle impingement

For optimal agglomeration, the particle and water droplet sizes should be roughly equivalent.

The probability of impaction also increases as the size of the water spray droplets decreases,

because as the size of the droplets decreases, the number of droplets increases by (Rocha 2005).

When wetting the bulk ore to achieve airborne dust prevention, droplet sizes above 100

micrometers (µm) (preferably 200 to 500 µm) should be used. In contrast, for airborne dusts

uppression, where the goal is to knock down existing dust in the air, the water droplets should be

in similar size ranges to the dust particles. The intent is to have the droplets collide and attach

themselves (agglomerate) to the dust particles, causing them to fall from the air. To achieve this

goal, droplets in the range of 10 to 150 µm have been shown to be most effective.

2.3.0 Methods of Atomization

Atomization is the process of generating droplets by forcing liquid through a nozzle, which is

accomplished by one of two methods. Hydraulic or airless atomization controls droplet size by

forcing the liquid through a known orifice diameter at a specific pressure. This method utilizes

high liquid pressures and produces relatively small- to medium-sized droplets in uniformly

distributed fan, full cone, or hollow cone spray patterns.

14

Hydraulic fine spray nozzles are preferred in most areas because operating costs are lower since

compressed air is not required. Air atomizing controls droplet size by forcing the liquid through

an orifice at lower pressures than the hydraulic atomizing method, by using compressed air to

break the liquid into small droplets. This method produces very small droplets and uniform

distribution in a variety of spray patterns.

However, it is more complex and expensive because it requires compressed air. In most cases,

air atomizing nozzles are effective in locations where dust particles are extremely small and the

nozzles can be located in close proximity to the dust source, although some applications will

require large capacity air atomizing nozzles to throw their sprays long distances to reach the dust.

2.3.1 Chemical Additives to Control Droplets

Surfactants are sometimes used in wet spray applications because they lower the surface tension

of the water solution, which has the following effects: reduced droplet diameter; an increase in

the number of droplets for a given volume of water; and a decrease in the contact angle (Blazek

2003), defined as the angle at which a liquid meets a solid surface θ as shown bellow:-

Figure 8: Contact angle resulting from a liquid meeting a solid surface

15

The use of surfactants increases the rate at which the droplets are able to wet or coat dust

particles; thus less moisture is used to produce the same effects as a typical water application.

Small amounts of surfactants can be injected into the spray water to improve the wetting and

subsequent control of dust particles (Swinderman et al. 2002).

Despite the effectiveness of chemical additives, it must be noted that they are not often used in

the metal/nonmetal mining industry based upon several limitations. Surfactants are significantly

more expensive than a typical water application. They can alter the properties of the mineral or

material being processed. They can damage some equipment such as conveyor belts.

The nozzle's droplet size distribution is the most important variable for proper dust control. The

droplet size decreases as the operating pressure increases. Information about the droplet size data

at various operating pressures can be obtained from the nozzle manufacturer. For wet dust

suppression systems, coarse droplets (200-500 µm) are recommended. For airborne dust capture

systems, very fine droplets (10-150 µm) may be required.

The fine droplets usually are generated by fogging nozzles, which may use either compressed air

or high-pressure water to atomize water in the desired droplet range. Droplet Velocity normally,

higher droplet velocities are desirable for both types of dust control through water sprays.

Information on the droplet velocity can be obtained from the nozzle manufacturer manual.

2.3.2 Wet Dust Suppression

There are two different types of wet dust suppressions: one wets the dust before it is airborne

(surface wetting) and the other wets the dust after it becomes airborne. At tanzanite one use dry

grinding which produce dusts to the environment especially around occupation area.

The Practical Resource for Cleaner, Safer, More Productive Dust & Material Control

(Swinderman et al. 2009), also devotes a chapter to the control of air movement, including a

section on effective measurement of air quantities. Finally, a recommended journal article is

"Dust Control System Design: Knowing your Exhaust Airflow Limitations and Keeping Dust out

of the System" (Johnson 2005).

Therefore in order to control the dust formed it is important to be aware of the fact that it should

not be automatically assumed that by wet, it means only water is being used in this process.

16

From the British Occupational Hygiene Society (BOHS) Technical Committee studied the "dust

yield" defined as "the mass of aerosol produced per mass of powder dropped" (BOHS, 1998). It

shows that initially increasing the mass increases the dust yield, but a point is reached when the

dust produced per unit mass levels off and then decreases. From the book written by (Trivedi, S

M and Ajay, 2011) Dust suppression of mine can be applied during drilling and milling

processes may reduce dust emission.

Airborne Dust have confirmed this (Breum, 1999), and one concluded that "dust generation can

be minimized by having powders fall as large, discrete slugs instead of a stream of small clumps;

slugs should be as large as possible to minimize the exposure of the powder to the airflow. The

explanation is that with higher material flow, there is more material at the centre of the falling

mass, and this central part is less exposed to surrounding air, and hence less likely to disperse.

Figure 9: The use of water to suppress dust

17

In many cases surfactants or chemical foams like Dustron PC are often added to the water into

these systems in order to improve performance. A water spray with surfactant lower the surface

tension of the water droplets and allow these droplets to spread further over the material and also

to allow deeper penetration into the material. Chemical foam is generally water and some sort of

special unify of surfactant.

Foam allows the surface area per unit volume of wetted material and efficiency of the

wetting to be increased. By applying this method during drilling and blasting processes may

reduce dust emission in surrounding working area. Wet drying is important and efficient method

to environment by eliminating dust emission during mining operation. Also the diagram bellow

gives details about the efficient of drop when surfactant is used:-

Figure 10: Sleap stream effect

18

CHAPTER THREE

3.0 METHODOLOGY

3.1 Surveying and consultation on site (drilling and blasting)

Surveying on site conducted to look on the drilling, blasting techniques and to consult project

supervisor so as to obtain technical solutions of problems. It was done through the help of project

supervisor, environmentalists, mining engineers and various experts concerned with the issue, as

well as different environmental journals, internet and other related sources.

3.2. Dust data collection.

Dust collection systems are the most widely used engineering control technique employed by

mineral processing plants and underground mining activities to control dust and lower workers'

respirable dust exposure. A well integrated dust collection system has multiple benefits, resulting

in a dust-free environment that increases productivity and reclaims valuable product. Data

collected for the analysis of achieving the desired target, the data collected are compared with

standards where performed through of dust sampling apparatus. Test performed by making

comparison between the standards placed by national environmental management council

(NEMC-not to exceed 250mg/Nm3) and world health organization (WHO-not exceed

500mg/Nm3) (the dust that do not injure the heath of workers).

3.3 Dust sampling

Dust sampling is the method that used to determine dust emission at Tanzanite one. Dust

sampling is the method that used to determine dust emission at Tanzanite one. According to

American Conference of Governmental Industrial Hygienists [ACGIH 2010]. The ACGIH

handbook considered as a primary resource for anyone interested in protecting workers from dust

exposure in the mineral industry using dust collector systems, and especially for engineers who

are involved in designing such systems. Dust collector at the occupational area collects the dust

released daily. After every 5 days dust in the collector brought to the laboratory for analysis. By

knowing the type of dust emitted at the site will help in management of dust. The dust collection

system (local exhaust ventilation system) is one of the most effective ways to reduce dust

emissions. A typical dust collection system consists of four major components:

19

Figure 11: Components of dust collection system

An exhaust hood used to capture dust emissions at the source, and Ductwork to transport the

captured dust to a dust collector, a dust collector remove the dust from the air, and fan and motor

provide the necessary exhaust volume and energy. Each of these components plays a vital role in

proper operation of a dust collection system, and poor performance of one component can reduce

the effectiveness of the other components. Therefore, careful design and selection of each

component is dangerous.

Principle of air flow

Airflows from a high- to a low-pressure zone due to the pressure difference; the quantity and the

velocity of airflow are related according to the following equation:

Q = AV

Where:

Q = volume of airflow, ft3/min

(Note 1m = 3.28ft)

V = velocity of air, ft/min

A = cross-sectional area through which the air flows, ft2

20

CHAPTER FOUR

4.0 DATA COLLECTION, ANALYSIS AND INTERPRETATION

4.1 Data Collection and Analysis

Table 1: Table show data of test # 1

Week 1, July 2014

Initial dust 210ppm and during the work 1095ppm

week 1 ORE PASS

Initial dust (ppm) 210

During the work (ppm) 1095

PH value in

pm Days Dust weight (ppm)

Cumm

.

(ppm)

Cum

m. %

%

emission

2.5

1ST

3hours

2ND

3hours Total

Monday 527 485 1012

1012 21.14 78.86

Tuesday 457 381 838 1850 38.66 61.34

Wednesday 450 405 860 2710 56.63 43.37

Thursday 581 509 1090 3800 79.41 20.59

Friday 520 465 985 4785

100.0

0 00.00

Total weight of dust emission 2540 2245 4785

21


Week 2, July 2014


week 2 LEVEL 73

Initial dust ppm 250

During the work ppm 1339

PH value in


Cumm.

(ppm)

Cumm.

%

%

emission

1ST

3hours

2ND

3hours Total

Monday 567 450 1017

1017 17.90 82.10

Tuesday 757 581 1338 2355 41.47 58.53

Wednesday 450 415 865 3220 56.70 43.30

2.5 Thursday 781 501 1282 4502 79.27 20.73

Friday 921 256

1177 5679

100.00 00.00


22


Week 3, July 2014


week 3 LEVEL 76



PH value in


Cumm.

(ppm)

Cumm.

%

%

emission

1ST

3hours

2ND

3hours Total

Monday 811 550 1361

1361 25.90 74.10

2.5 Tuesday 634 421 1055 2416 45.99 54.01

Wednesday 564 615 1179 3595 68.44 31.56

Thursday 381 301 682 4277 81.42 18.58

Friday 620 356 976

5253 100.00 00.00


23


Week 4, July 2014


week 4 LEVEL 77/PILOT



PH value in


Cumm.

(ppm)

Cumm.

%

%

emission

1ST

3hours

2ND

3hours Total

Monday 1012 450 1462

1462 19.26 80.74

2.5 Tuesday 931 628 1559 3021 39.79 60.21

Wednesday 888.1 600.5 1480.6 4501.6 59.29 40.71

Thursday 867 670.2 1537.2 6038.8 79.53 20.47

Friday 1001 553 1554

7592.8 100.00 00.00

Total weight of dust emission 4691.1 2901.7

7592.8

24

4.2. Data Interpretation

THE GRAPH SHOWS RELATIONSHIP BETWEEN WEIGHT OF DUST EMISSION

AGAINST DAYS OF WEEK

ORE PASS

0

200

400

600

800

1000

1200

Monday Tuesday Wednesday Thursday Friday

D

U

S

T

C

O

N

C

.(

P

P

M)DAYS

1ST 3hours

2ND 3hours

Total

25

THE GRAPH SHOW RELATIONSHIP BETWEEN DUST EMISSION PER WEEK

LEVEL 73

0

200

400

600

800

1000

1200

1400

1600


D

U

S

T

C

O

N

C

.(

P

P

M)Days

1ST 3hours

2ND 3hours

Total

26


LEVEL 76

0

200

400

600

800

1000

1200

1400

1600


D

U

S

T

C

O

N

C

.(

P

P

M)Days

1ST 3hours

2ND 3hours

Total

27


LEVEL 77/PILOT

0

200

400

600

800

1000

1200

1400

1600

1800


D

U

S

T

C

O

N

C

.(

P

P

M)

Days

1ST 3hours

2ND 3hours

Total

28

CHAPTER FIVE

5.0 RESULTS AND DISCUSSION

From the data extracted from Tanzanite one mining company each table shows the initial and

final dust emission for both five days of the work, the model of the data collection is for every

three hours in order to avoid error and to make improvement of dust truck working efficient

during the data collection. The data summed together to find the total amount of dust emission

per day/week during the mining activities.

Lastly calculation of cumulative frequency and the percentage in order to know the exactly the

percentage of dust that will be reduced per day/week

Also from the data on the table and graphs shows variability of dust emission depending to

condition of ventilation and dust control technology, example from the ore pass dust emission is

very low compared to level 77/pilot since ore pass area is very near to the surface were

ventilation is actually fine compare to pilot were is very deeper about 1.5km from the surface.

(Total dust at ore pass 1095ppm while level 77/pilot 1600ppm) Furthermore, it seems that as the

ventilation decrease it results the high dust concentrate and therefore more technology required

for moderation.

29

CHAPTER SIX

6.0 CONCLUSION AND RECOMMENDATION

6.1. Conclusion

Moderation of dust was done through the water suppression gives a least satisfactory of dust

emission due lack of enough technical methods like doing the magnification of spray equipments

and doing a sampling for analysis which will help to have a good follow up of dust on dealing

with performance of the sprayer.

6.2 Recommendation

Since it has been shown that there is increases in dust emission and the moderation conducted

through water suppression, I would like to recommend that the company might moderate much

by improve the suppression system by doing magnification of pipe nozzle depend to the size of

the dust particles (coarse droplets 200-500 µm and very fine droplets 10-150 µm may be

required). Also to use surfactant method of dust moderation (chemical foams like Dustron PC)

for the best result. By doing so the amount of dust emitted will be minimized in high extent and

to meet the standards 250mg/Nm3- 500mg/Nm

3 suggested by National Environmental

Management Council (NEMC) and World health organization (WHO).

30

REFERENCES

American Conference of Governmental Industrial Hygienists; “Industrial ventilation”, a

manual of recommended practice for design. 27th ed. Cincinnati, 2010.

Bartell W, Jett B, “The technology of spraying for dust suppression”, Cement Americas,

pp. 32–37, 2005.

Datson, H. Birch, W.J, “The development of a novel method for directional dust

monitoring”, Environmental Monitoring and Assessment, Vol.124 (1-3), pp.301-308,

2006.

Trivedi, S .M, Ajay, Dust suppression of mine haul road, “India Seminars on Advances

in Mine Production and Safety”, Dhanbad, pp 239-246, 2011.

Vallack, H. W. & Shillito, D. E , “Suggested guidelines for deposited ambient dust”,

Atmospheric Environment, Vol.32, pp.2737-2744, 1998.

31

APPENDICES

Location of Tanzanite one mining company

Underground Drilling that results urge dust at Tanzanite one mining company

32

Week 1, July 2014


week 1 ORE PASS



PH value in pm

Days Dust weight (ppm) Cumm. (ppm)

Cumm. %

% emission

2.5

1ST

3hours

2ND

3hours Total

Monday 527 485 1012 1012 21.14 78.86

Tuesday 457 381 838 1850 38.66 61.34

Wednesday 450 405 860 2710 56.63 43.37

Thursday 581 509 1090 3800 79.41 20.59

Friday 520 465 985 4785 100.00 00.00


33

Week 2, July 2014 : Initial dust 250ppm and during the work 1339ppm

week 2 LEVEL 73



PH value in pm

Days Dust weight (ppm) Cumm. (ppm)

Cumm. %

% emission

1ST

3hours

2ND

3hours Total

Monday 567 450 1017

1017 17.90 82.10

Tuesday 757 581 1338 2355 41.47 58.53

Wednesday 450 415 865 3220 56.70 43.30

2.5 Thursday 781 501 1282 4502 79.27 20.73

Friday 921 256

1177 5679

100.00 00.00


Week 3, July 2014: Initial dust 245ppm and during the work 1400ppm

week 3 LEVEL 76



PH value in


Cumm.

(ppm)

Cumm.

%

%

emission

1ST

3hours

2ND

3hours Total

Monday 811 550 1361

1361 25.90 74.10

2.5 Tuesday 634 421 1055 2416 45.99 54.01

Wednesday 564 615 1179 3595 68.44 31.56

Thursday 381 301 682 4277 81.42 18.58

Friday 620 356 976

5253 100.00 00.00


34

Week 4, July 2014: Initial dust 295ppm and during the work 1600ppm

week 4 LEVEL 77/PILOT



PH value in


Cumm.

(ppm)

Cumm.

%

%

emission

1ST

3hours

2ND

3hours Total

Monday 1012 450 1462

1462 19.26 80.74

2.5 Tuesday 931 628 1559 3021 39.79 60.21

Wednesday 888.1 600.5 1480.6 4501.6 59.29 40.71

Thursday 867 670.2 1537.2 6038.8 79.53 20.47

Friday 1001 553 1554

7592.8 100.00 00.00

Total weight of dust emission 4691.1 2901.7

7592.8


ORE PASS:

0

200

400

600

800

1000

1200


D

u

s

t

c

o

n

.(

p

p

m)

Day

1ST 3hours

2ND 3hours

Total

35


LEVEL 76


LEVEL 77/PILOT

0

200

400

600

800

1000

1200

1400

1600


D

U

S

T

C

O

N

C

.(

P

P

M)

Days

1ST 3hours

2ND 3hours

Total

0

200

400

600

800

1000

1200

1400

1600

1800


D

U

S

T

C

O

N

C

.(

P

P

M)

Days

1ST 3hours

2ND 3hours

Total

36

Formula

CALCULATION

Cumulative Weight of dust per week = weight1, (weight 1+weight 2), (weight 1+weight 2

+weight 3)

For example

Table no.4

1462+1559+1480.6+1537.2

% cumulative weight= (cumulative weight/total weight) *100%

For example

(1462/7592.8)*100%

=19.26%

(1559/7592.8)*100%

=20.5%

%of dust emission/day =100 - % cumulative weight retained

100-19.26%

=80.74%

Therefore the dust emission per week can be reduced/ controlled for more than 80.00%

rasiel reseach

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