Arsenic leaching potential from fly ash of coal power plant in vietnam

Main Technologies used in a typical Coal Power Plant and pathway of flue gas………..22 Figure II.1.1.. Distribution map of Arsenic in Pha Lai Thermal Power Plant area for rain season ……….

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

Hanoi, 2019

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

Prof Dr TRAN HONG CON Prof Dr TAKASHI HIGUCHI

Hanoi, 2019

Table of content

1 Research Motivation and Literature Review……….……… 9

1 1 Introduction of Coal Power Development in Vietnam………9

1 2 Fly Ash Management Practice in Vietnam……… 10

1 3 Characteristic of Arsenic in Fly Ash………14

1 3 1 Physical and Chemical Properties of Class C Fly Ash………14

1 3 2 Physical and Chemical Properties of Class F Fly Ash………15

1 3 3 Overview of Arsenic……….16

1 3 4 Toxicity of inorganic Arsenic to human health and regulation in Vietnam………16

1 3 5 Behavior of Arsenic in Fly Ash and its release potential………18

1 4 Research Approach……… 23

2 Methodology and Apparatus………26

2 1 Sampling and Collection……… 26

2 1 1 Introduction of Pha Lai Thermal Power Plant……….26

2 1 2 Sampling Method……… 28

2 2 Storage and Preservation……… 32

2 3 Physical Characteristic of Fly Ash……… 33

2 4 Solid-Liquid Ratio (SLR) Examination……… 33

2 5 Leaching Test under strong acid condition (pH = 1)……… 34

2 6 Leaching Test under strong alkali condition (pH = 10)……… 36

2 7 Leaching test under acid rain condition……… 37

2 8 Leaching test under seawater condition……… 38

2 9 Sample Digestion……… 39

2 10 Quantitative Analysis……… 40

2 11 Method Validation……… 44

3 Result……… 45

3 1 Physical Properties of Fly Ash……… 45

3 2 Calibration curve……… 46

3 3 Method Validation and Quality Control……… 47

3 3 1 AAS Comparison……… 49

3 3 2 Pack Test comparison………51

3 3 3 Precision Test………54

3 4 Arsenic Distribution in surveyed area……….55

3 4 1 Distribution of rain season………56

3 4 2 Distribution of dry season……….68

3 5 Arsenic Leaching Potential (ALP) in different condition……… 64

3 5 1 Acid Condition (pH = 1)………62

3 5 2 Alkali condition (pH = 10)……….63

3 5 3 Acid rain condition (pH = 4.20)……….64

3 5 4 Seawater condition (pH = 7.76)……….65

4 Discussion……… 66

4 1 Method Validation and Quality Control……… 66

4 2 Arsenic Distribution in surveyed area……….66

4 3 Arsenic Leaching Potential (ALP) in different condition……… 68

5 Conclusion……… 70

6 Limitation……… 71

REFERENCE……….72

Table II.1.2 Summary of sample types and season variation……….33

Table III.3.1 Specific samples used for each kind of validation/QC test……… 49

Table III.3.2 Comparison of analytical results between HgBr2 Method and AAS

Method……… 50

Table III.3.3 Chi-square Test for Goodness of Fit between HgBr2 and AAS results….51

Table III.3.4 Comparison of results between Pack Test and HgBr2 Analysis…… …53

Table III.3.5 Precision Test Result for HgBr2 method……… …55

Table III.4.1 Detail information of Arsenic content in soil sample (rain season)…… 57

Table III.4.2 Detail information of Arsenic concentration in water sample (rain

season)……… ….59

Table III.4.3 Detail information of Arsenic content in soil sample (dry season)…… 60

Table III.4.4 Detail information of Arsenic concentration in water sample (rain

season).……… 62

Table IV.2.1 Average monthly rainfall of Bai Chay monitoring station, Quang Ninh

province, 2017………67

List of Figure

Figure I.2.1 Ash impoundment of Hai Phong Thermal Power Plant I & II, Thuy Nguyen

District, Hai Phong.………12

Figure I.3.1 SAC Ternary Diagram of materials ……… 16

Figure I.3.2 Main Technologies used in a typical Coal Power Plant and pathway of flue gas……… 22

Figure II.1.1 Sampling Map for both Rain Season and Dry Season……… …31

Figure III.1.1 SEM image of Fly Ash at x500 magnification……….45

Figure III.1.2 Composition of Fly Ash……….46

Figure III.2.1 Calibration curve for Mercury (II) Bromide method (Low concentration: 10-100ppb)……….47

Figure III.2.2 Calibration curve for Mercury (II) Bromide method (High concentration: 100-1000ppb)……….48

Figure III.3.1 Histogram for frequency distribution of difference percentage between 2 data sets……… 53

Figure III.3.2 Correlation between HgBr2 and Pack Test results……… 54

Figure III.4.1 Distribution map of Arsenic in Pha Lai Thermal Power Plant area for rain season ……….57

Figure III.4.2 Distribution map of Arsenic in Pha Lai Thermal Power Plant area for dry season……….60

Figure III.5.1 Arsenic Leaching Potential (ALP) for acid condition……….…63

Figure III.5.2 Arsenic Leaching Potential (ALP) for alkali condition……… …64

Figure III.5.3 Arsenic Leaching Potential (ALP) for acid rain condition……… 65

Figure III.5.4 Arsenic Leaching Potential (ALP) for seawater condition………….…66

Abbreviation List

ARP/ALP Arsenic Release/Leaching Potential

USEPA United States Environmental Protection Agency

Acknowledgement

First and foremost, I would like to express my greatest appreciations

to Prof Tran Hong Con, Hanoi University of Science and Prof Takashi Higuchi, Ritsumeikan University, my principal supervisors whose expertise, generosity and thorough guidance have enormously contributed to the completion of this thesis as well as my understanding of the topic that is of

my great interest There is no such honor being comparable to working with them

I would like to sincerely thank Prof Jun Nakajima, my special academic advisor at Vietnam-Japan University for spending his precious time in busy schedule to share advices and helpful support in the progress of implementing and writing this thesis

Importantly, I would like to spend my most sincere gratitude to Prof Cao The Ha - Director of MEE program, Prof Hiroyuki Katayama, Prof Ikuro Kasuga, Dr Nguyen Thi An Hang and the entire MEE Department for valuable support during the implementation of thesis as well as my stay in VJU Thank you for everything we have experienced together

I would also like to express my gratefulness to Ms Tran Dieu Linh,

my fellow student in MEE and Mr Dao Trung Duc, MNT student for their kind and dedicate assistance in my study

Without directive support and coordination from all Departments of VJU and specially Department of Academics and R&D as well as Japan International Cooperation Agency, this internship could not be completed in such successful and exhaustive manner Therefore I would like to humbly offer my thankfulness to the efforts of the University and JICA

1.Research Motivation and Literature Review

1.1 Introduction of Coal Power Development in Vietnam

After nearly four decades of effort and development, Vietnam’s economy has been achieving new thriving milestones, especially 6.5-7.0% predicted GDP growth rate over the 2016-2020 period, which successfully puts the nation into dynamic economy and attractive investment group (VCCI & PwC, 2017) In order to increase and sustain the domestic production, however, the country has required gigantic power consumption of high reliability but more importantly, of good affordability Among all types of high-capacity energy source such as nuclear, wind, solar, hydro, thermal; Thermal energy with focus on coal (from now on referred as Coal Power) seemed to outweigh the rest due to three main reasons Firstly, the conventional hydropower installed in Vietnam’s river network has almost reached its maximum potential due to exploitation since 1960s (VCBS, 2016) Besides, the more complexity in multi-stakeholder governing of Mekong River Basin and unpredictable water patterns of climate change has recently made hydropower less keen toward policy makers Secondly, Coal Power offers cheaper initial investment and maintenance if removing environmental cost and thus bring more reasonable price for the majority of people in short term Thirdly, in vision to 2030/2050, Vietnam will prioritize the development of renewable energy to gradually replace other kinds of conventional power, but in the meantime to guarantee energy security, Coal Power will still be on its watch (General Directorate of Energy, 2017)

According to the Power Development Plan VII, until 2020, the total general capacity off all power sources is expected to reach 60,000MW, in which 21,600MW belongs to Hydro Power (36%) and 26,000 MW belongs to Coal Power (43.3%) This energy trend will abruptly be adjusted in the manner which double the capacity of coal power into 47,600 MW of total 96,500 MW (49.3%) while hydropower proportion reduce to 23% in 2025 By 2030, to meet up with high

energy demand of 129,500MW, all power sources must enhance their production leading to the soar of Coal Power into 55,300MW (Approval of the Revised National Power Development Master Plan for the 2011-2020 Period with the Vision to 2030; General Directorate of Energy, 2017)

Higher power must accompany with higher responsibility in terms of economic as well as environment Yet this is when two edges of the blade appear

social-On one hand, the coal power ensure a stable input with reasonable cost for domestic production without too much investment to renewable energy at a time On the other hand, latent pressure of coal-combustion-derived pollutions with vibrant precursors is becoming a real threat for sustainability of Vietnam Among them, hazardous effects to surrounding ecosystem of heavy metals in fly ash under open, inadequate storage and management are drawing substantial attention from Vietnamese researcher Under the range of this Master’s Thesis, an insightful study toward leaching potential and distribution of Arsenic from fly ash of thermal power

plant will be provided The first half of part 1: Introduction will help shed light

on the practical situation, urgent necessity in Vietnam that led to the conduct of this study

1.2 Fly Ash Management Practice in Vietnam

For many years using Coal-fired Power Plants effectively, although not being audited carefully, the estimated amount of fly ash (coal-derived combustion by-product in solid form) accumulated has reached approximately 30 million tons, yet

in which less than 4 million have been treated The majority of fly ash from Thermal Power Plant is being stored at open areas surrounding each plant Nonetheless, under open condition, the light-weight, particulate properties of fly ash make it extremely prone to dispersing, causing air pollution to the surrounding environment To mitigate the effect, fly ash is usually transported to water bodies

of proximity named “ash pond” to store This method is referred as wet disposal

or wet impoundment (B Stapp, 2015)

(1) Most ash pond are relatively large with the purpose of long-time holding fly ash inside, making most of them impossible to have protective bottom layer and ,therefore, pond water containing high content of Heavy Metals tend to leak to nearby regions, causing damage to both people’s health and reduce economic values (Vietnamnet, 2016)

(2) The input water sometimes has inconsistent quality and source, eg Sea water, normal rain, acid rain, fresh water, etc., causing it more difficult to control the behavior of heavy metals during aging process

(3) The different types of coal ash product also have different behaviors during wet impoundment, which will be discussed in the next chapter

Figure I.2.1 Ash impoundment of Hai Phong Thermal Power Plant I & II, Thuy

Nguyen District, Hai Phong (Source: Google Earth)

Many countries who used to use coal power in the past has been struggling with this issues for decades and eventually come up with new solutions to avoid wet disposal The most leading country to refer in this realm is Japan According to Sato and Fujikawa in 2015 and reports from the Japan Coal Energy Center (JCOAL), there are various solution derived to suppress the controversial impacts

of coal ash or waste incineration ash The most important initiative is to reuse them

as materials for other building purposes Secondly, the country is approaching toward coal gasification, which produce syngas (Carbon monoxide + Hydrogen + Carbon Dioxide + Methane) to apply for higher efficiency combustion process Furthermore, more improvements for flue gas treatment were carried out with more strict regulations to ensure the quality of living environment as Japan has recently been in a serious power reform after the earthquake at Fukushima nuclear power in

2011

In another so-called developed country of the region such as India, a lot of emphasis has been put into materializing of fly ash Based on types of coal and content of lime (CaO), fly ash can be classified into two main types: C (>20% CaO), and F (< 10% CaO) Class C fly ash with self-cementing property is used more widely with construction purposes: Fly Ash-Based Cement, Brick, Embankment, Concrete or Ceramics (Dwivedi and Kumar Jain, 2014; Senapati, 2011) With lower lime content, Class F fly ash need activator additives like Portland Cement or quicklime

to start cementing or can be mixed with Sodium Silicate to form geopolymer (Dwivedi and Kumar Jain, 2014) Additionally, some studies shows that fly ash can

be used for agriculture to improve permeability, fertility, texture of soil, stabilize some HMs and optimize pH value (Kumpiene, Lagerkvist and Maurice, 2007; Alam and Akhtar, 2011)

The above pathways all lead to a bright end for thermal power that inflict little harms to ambient air and minimize the volume of fly ash disposed in developed countries But for now, the lack of technology and economic potential is holding Vietnam back though all limitation has been realized Hopefully, with more scientific paper plus practice in environmental pollution, Vietnam’s policy maker will have a different look into the situation

Beside of technological factor, the second main reason is due to coal type variation leading to inconsistence of fly ash quality With mentioned demand for energy production in the next few decades, Vietnam is predicted to face serious needs for

coal to supply the entire system Table I.2.1 will depict the coal demand in several periods

Table I.2.1: Estimation of coal demand/supply for Vietnam over different periods

of time (Source: Vietnam’s Power Development Plan, Ministry of Industry and

Trade, 2017)

Estimated Demand (Million Tons)

2017 2018 2019 2020 2025 2030 Demand 55.2 63.5 76.2 86.4 121.5 156.6

Domestic Supply 45.6 44.6 46.9 48.2 53.2 56.6

Import Coal (5,500 Kcal.kg) 11.7 21.0 31.5 40.3 70.3 102.1

Import for Coal-fired Power Plant 4.3 9.8 18.0 25.1 57.6 86.6

From the table, it can be easily seen that by 2030 the annual consumption of coal will triple at 156.6 million tons, comparing to 2017’s data However, as Vietnam’s natural reserve for coal has been drained out and most of coal sources will be provided from other countries In 2030, the domestic capacity is expected to meet around 30% of total needs, and Coal-operated thermal power will utilize more than 80% of imported amount Hence, it will be even more challenging in the future to identify exact type of fly ash to apply appropriate treatment technology

To finalize, it can be concluded from the situation that:

(1) The higher the coal consumption will be, the more fly ash will be created; leading to much more serious environmental burden, especially if simple wet disposal method continues

(2) The inconsistent of coal quality and originality will make it more challenging for treatment of fly ash Hence, in the meantime of developing new technology,

wet disposal will still be regarded as a temporary solution This process might take years to eliminate all fly ash accumulated

(3) Therefore, to obtain good understanding on the influences of fly ash aging in wet impoundment, research for availability/release potential of hazards from fly ash is urgent

(4) The most toxic component of fly ash in storage are Heavy Metals, including Arsenic This Master’s Thesis put emphasis on the Arsenic Leaching Potential (ALP) in various conditions and arsenic distribution in surrounding areas as a baseline study for assessing hazard level imposed by fly ash

1.3 Characteristic of Arsenic in Fly Ash

Fly Ash is the fine-particle particle byproduct of combustion process, mostly by Coal-Power Plant or Biomass Power Plant aiming to generate power and Waste Incineration Plant This study only concentrates to Coal Fly Ash, which is of greatest concerning for Vietnam at the moment Based on physical properties and originality, Fly Ash can be divided into two main groups: Class C and Class F The following parts will describe more of their characteristic and explain why they are important information

1.3.1 Physical and Chemical Properties of Class C Fly Ash

Basically, there are 4 major types of coal often utilized in combustion process: Anthracite, Bituminous, Sub-bituminous and Lignite Anthracite is regarded as the highest rank of coal which contains approximately 95% of carbon, making it hard and shining black color and lower volatile content Bituminous is soft coal, containing higher moisture content (up to 20%) and volatile content (up to 40%) Sub-bituminous is also soft black coal, less superior than the other above, but can

be found more common in thermal power Lignite, as being ranked lowest in value, contain highest moisture proportion and lowest heat value Class F Coal is group

name for Anthracite and Bituminous coal while Class C composes of bituminous and Lignite coal

Sub-Therefore, in terms of originality, Class C Fly Ash is the combustion byproduct of Class C Coal

In terms of major composition, class C and Class F difference can be defined using SiO2-Al2O3-CaO Diagram (SAC-Ternary Diagram) as in Figure I.3.1

Figure I.3.1 SAC Ternary

Diagram of materials (Source:

(Tennakoon et al., 2015)

Class C Fly Ash, according to the diagram, has SiO2 content ranging from 80%), AlsO3 content around 30% and CaO content from 12-28% Due to its natural abundancy in lime, class C Fly Ash tend to self-solidify or concreating more quickly Besides, the rich lime content in it help produce alkaline fluid during aging process in wet impoundment (Catalano et al., 2012), which is very important for choosing appropriate leaching method of this study Other than major components, other metals and Heavy Metals such as Fe, Ni, Mg, Cr, Pb, As, Se, Cd, Cu, Zn also present in fly ash as a result of co-mineralization in coal deposit (Catalano et al., 2012; Deonarine et al., 2016) However, the occurrence of these HMs does not depend on type of fly ash but rather their deposit location and other variables

60%-1.3.2 Physical and Chemical Properties of Class F Fly Ash

The most significant difference between class C and class F Fly Ash lying in their CaO proportion (Guo and Shi, 2013; Bankowski, Zou and Hodges, 2004) By combusting class F coal: Anthracite and Bituminous, class F Fly Ash is obtained Specifically, there are around 80% SiO2, 18-40% Al2O3, and 2-18% CaO in class

F This difference makes it harder for class F ash to self-solidify under normal condition and need supplementary additive like pozzolan cement to make concrete Additionally and more importantly, in reverse with class C fly ash, class F produce more acidic condition during aging process based on its low lime content (Catalano

et al., 2012; Deonarine et al., 2016) This will greatly affect the release potential as well as behavior of many substances inside the matrix, in which most significantly

to this study, Arsenic

1.3.3 Overview of Arsenic

Arsenic (As) is the 33th element of periodic table with atomic weight of 74.92 Arsenic is a metalloid, usually occur in nature under mineral forms (in which mostly of sulfur and other metals) Arsenic is abundant in Earth’s crust (ranked

53th), making it ubiquitously available in many country, especially South East Asia and can be found in both soil and water environment Beside natural occurrence, Arsenic is used directly in agricultural products (pesticide, herbicide, insecticide), wood preservatives, batteries, pigment production, ammunition and present indirectly in coal ash from Thermal Power Plants

There are two main form of Arsenic: organic and inorganic Organic arsenic happens through bioaccumulation when organism consume food with higher content of Arsenic Organic Arsenic is regarded as less toxic than its counterpart, inorganic Arsenic

1.3.4 Toxicity of inorganic Arsenic to human health and regulation in Vietnam

According to World Health Organization (WHO), inorganic Arsenic is considered

as highly toxic Major diseases relating to arsenic poisoning (Arsenicosis) includes acute immediate symptoms, skin, bladder and lung cancer

In short term, the direct exposure to high concentration of Arsenic might cause nausea, vomiting, abdominal contraction and diarrhea if non-lethal dose is absorbed When lethal enough, Arsenic poisoning can make victim feel extreme tingling, numbness and finally death (WHO, 2018) In many countries, Arsenic has been used as one of the quickest poison for centuries and the small amount as half

of a pea size can instantly cause mortality to a person

In long term, it has been reported that the contact with Arsenic-contaminated water

of more than 50 mg/L (50 ppm) for a long duration will increase 1% of cancer in population (National Research Council (US) Subcommittee on Arsenic in Drinking Water, 1999) The most common cancer type is skin cancer, nonetheless lung cancer and bladder cancer are also found related to the situation In fact, the death

by Arsenic poisoning is not unexpected Patients will suffer from skin lesion,

“Black Foot Disease”, hyperkeratosis, heart attacks and kidney failure for a long period of time before the death penalty (WHO, 2018) These precursors are not only painful but also affect greatly to the victims’ livelihood

Arsenic exists in two oxidation states, Arsenic trivalent: As(III) and pentavalent As(V) It is also widely known that As(III) is 60 times more toxic than As(V) (Ratnaike, 2003)

In our body, Arsenic can deactivate several hundreds of vital enzymes, disrupting particularly to which coordinate DNA replication, DNA repair and cellular energy pathway ATP, the most vital energy holding compound, will be destroyed by substituting Phosphorous by Arsenic (Ratnaike, 2003) DNA damage, lipid peroxidation and reactive oxygen production that harm organs’ function are by-products of Arsenic reduction-oxidation process and metabolic activation process (Cobo and Castiñeira, 1997)

Acknowledging the deleterious consequences of Arsenic contamination and the essential of prevention, WHO, U.S EPA and many countries has established safety limits for Arsenic uptake as well as Arsenic concentration in soil and water environments Table I.3.1 shows some typical standard values for Arsenic with comparisons to Vietnam

Table I.3.1 Comparison of typical Standard Values for Arsenic in some

environments (Soil, Hazardous Waste, Surface water, Ground water, Drinking water)

WHO Standard

U.S Standard Vietnam Standard Arsenic in Soil - - 15-20 mg/kg

1.3.5 Behavior of Arsenic in Fly Ash and its release potential

Because of Arsenic’s extreme toxicity, it is necessary for any country to evaluate the presence of this substance in any industrial activities that prone to increase the total amount of Arsenic in the region Vietnam in its own direction to expand Coal Power scale is not an exception Though total Arsenic (T-As) is an important target

of examination, it will be inconsiderate if its mobility or release potential (also called leaching potential) is taken lightly (Azam et al., 2008)

To have a good insight toward FA’s Arsenic characteristic and behavior, it is significant to know the chemical transformation during combustion process of coal Under high temperature in boiler, most substances existing in coal undergo thermal denaturing: volatilization of VOC, molecular breakdown (disintegration), re-fusion

to form new compounds (Pandey et al, 2011) Coal pulverized to maximize heat conversion breakdowns into much finer, spherical FA particles and act as a cooler surface for condensing volatile inorganic compounds (Pandey et al, 2011) Many metal elements obey gradation theory and be divided into several groups Some experience little concentration increase with decreased particle size (“Litho” Group); some, including “Pb, As, Se, Cd, Sb”, increase their concentration with decreased particle size (“Chalco” Group) while some shows milder manners between two groups (Davison et al., 1974; Klein et al., 1975) The enrichment of these new compounds takes place in spherical outer layer and speedily extractable from 5%-40% in water (Linton et al., 1976) Hence, since 1980, USEPA in their publication “Ambient water quality criteria for arsenic” has observed considerable concentration of soluble salts, toxic compounds and Arsenic in Fly Ash

As mentioned, Arsenic is mostly abundant in co-existence of Iron and Sulfur, which possess mineral form of Pyrite (FeS2) Jacob et al in 1970 conceived an improved rate of arsenic adsorption in presence of iron or aluminum oxide, especially Arsenate (As-V) Furthermore, the capture ability of iron can even be enhance with support of Calcium, forming [Ca2.Fe3(AsO4)3.(OH)4.10H2O] complex (Pandey et al, 2011) Fortunately, this can be perceived as an advantage as lime (CaO/Ca(OH)2) is frequently added during operation of power plant to act as principal desulfurizer Goodarzi, 2006 and Zielinski et al, 2007 have proved the Ca-capturing theory when highest amount of trace elements were found in bag filter,

in which more forms were found

There are two dominant fates in which Thermal Power Plant’s proximities become exposed with Heavy Metals in Fly Ash in general and Arsenic in specific:

(1)Particulate Matter transport through dispersion and sedimentation; and (2)leaching in soluble form from fly ash impoundment (Pandey et al., 2011; Catalano et al., 2012; Deonarine et al., 2016; Azam et al., 2008)

(1) Particulate Matter transport through dispersion and sedimentation: to

understand the principle of this pathway, the emission and pollution control mechanism of Coal Power Plant should be explained first Figure I.3.2 demonstrates the operating process of a typical power plant

Starting from input material, coal will be delivered by conveyor to combustion chamber Theoretically, the heat conversion from burning coal is calculable precisely, however in practice the actual efficiency is even lower and be dependent on the version of combustion technology as well as maintenance status The incomplete burning of coal will result in fly ash with more carbon content and might have different behavior with ideal fly ash However since researching every aspect will be resource-consuming, this master thesis will assume fly ash as completely burnt

After going through combustion chamber and heat conversion process, the flue gas containing emission gases and fly ash is directed to filter system when single or multiple technologies applied For particulate phase, the most popular systems can be listed as Gravitational settle/Cyclone which take advantage of kinetic loss in collision with chamber’s wall to settle coarse particle; Bag Filter/Membrane Filter for finer particle that escaped cyclone; Liquid treatment using water to adsorb/absorb dust; and Electrostatic Precipitator (ESP) in which particulate matters will be electrostatically charged and collected For gas phase, the most harmful gas/greenhouse gas is SO2, therefore the Flue Gas Desulfurization chamber, using lime (CaO/Ca(OH)2) to capture SO2 effectively

Figure I.3.2 Main Technologies used in a typical Coal Power Plant and pathway

of flue gas (Source: Liberty Hygiene, www.libertyhygiene.com)

Although these technologies plays an important role in mitigating the effect of serious pollution and is competent to achieve dust removal yield from 95% to 99.5% (Meikap, 2004), the amount of fly ash escaped through stack and entering atmosphere are still relatively large, especially with local communities surrounding Thermal Power Plants According to data, it is estimated that a 500MW plant can produce up to 500 tons of fly ash per day Thus a common 1200MW Power complex in Vietnam, in both scenarios, can produce:

If 95% removal yield achieved

1200𝑀𝑊 500𝑀𝑊 x 500 𝑡𝑜𝑛𝑠

𝑑𝑎𝑦 x 365 𝑑𝑎𝑦𝑠

𝑦𝑒𝑎𝑟 x 0.5% = 2,190 𝑡𝑜𝑛𝑠 𝑓𝑙𝑦 𝑎𝑠ℎ

𝑦𝑒𝑎𝑟Some part of P.M can travel very far distance but many, depending on wind, particle size and moisture, stay closely to the power plant The amount of free fly ash can varies with technological improvement but in either situation, the

pressure to environment and public health is of great question Acid rain and other weathering condition might be a factor to increase the release of soluble Arsenic Rain washout, surface runoff and infiltration can transport these potential contamination to water bodies that used by communities for domestic use (Pandey et al, 2011)

(2) Arsenic leaching from wet impoundment: for decades, researcher has tried

to evaluate the mobility and toxicity of Arsenic in various leaching condition, both in-lab and in-situ since they are key factors of Arsenic behavior and As-containing water are most likely to be consumed by human and related living organisms Yet, the leaching manner has so far not clearly explained (Pandey

et al, 2011) Several theories of interaction were introduced, in which pH, reduction-oxidation state, ionic strength of solution meet high consensus for their importance (Kirby and Rimstidt, 1994; Azam et al., 2008; Catalano et al., 2012; Deonarine et al., 2016)

Arsenic Release Potential (ARP) or Arsenic leaching potential (ALP), however, receives most attention from pH approach as it can interpret some, but not to all extent, mechanisms Based on classification of coal, fly ash is also divided into class C and class F There is a strong belief among scientists that class C fly ash during aging process produce alkaline environment due to higher Ca content, though gradually get neutralized by CO2 intake from the atmosphere (Catalano

et al, 2012; Deonarine et al., 2016) On the other hand, class F with much lower level of Ca, have tendency to produce acidic environment in contact with water (Catalano et al, 2012; Deonarine et al., 2016) Wide range of studies also suggested that the pH range for minimum release is pH 3-7 and pH ranges for increasing ARP are pH < 3 and pH 7-11 (Wang et al., 2009; Pandey et al., 2011; Izquierdo and Querol, 2012; Bednar et al., 2010) In his study, Wang et al, 2009 also indicated that Bituminous coal (Class F) leached relatively more than Sub-bituminous coal (Class C)

The difference in ARP by pH can be explained by two major mechanisms: adsorption/desorption to iron oxide and Calcium precipitation The sharp rising

of arsenic concentration in low pH leaching test is possibly attributed by adsorbable As from neutral region and FA particle dissolution itself in strong acidic condition (Wang et al., 2008; Wang et al., 2009) In contrast, the hypothesis for the increasement of ARP in alkaline condition might be protonated surface annihilation in high pH, leading to loss binding site for As-anions thus making them more available (Wang et al., 2008; Wang et al., 2009) Nonetheless, when pH reach 9 or more, formation of AsO43- commence Since this form of Arsenic is most preferred by free Ca for co-precipitation, the ARP now exhibits decrease comparing to acidic condition The higher the pH becomes, the more insoluble calcium arsenate gains and the less Arsenic is released to leachate (Wang et al., 2009) Yet if pH can breakthrough extreme alkaline value ( pH ≥ 11), Ca will prioritize hydroxide ion to precipitate in form

non-of Ca(OH)2, weakening Ca-As bond and enabling more Arsenic to be released (Wang et al., 2009)

1.4 Research Approach

Most of the mentioned studies are able to distinguish the originality of coal (lignite, sub-bituminous, bituminous, anthracite) and types of FA they are focusing (class

F, class C), but so far most of research in Vietnam have encounter a serious problem

of mixing coal from various sources in each Thermal Power Plant, caused by the shortage in domestic supply and leading to uncertainty in fly ash type The accurate mixing ration between class C and class F coals remain unknown in reality, therefore it is even more challenging for researcher to predict the behavior of Arsenic during wet aging The As toxicity to local communities and release potential from then are different to previous studies and need a new approach to evaluate these parameter again

Therefore, this study aims to re-assess the release potential of Arsenic in Fly Ash following practice in Vietnam; also evaluate the toxicity of this substance from

power plant, ash storage site to local community by determining total-arsenic, leaching potential as well as its distribution in both soil and water samples

The research approach can be separated into 3 main phases:

❖ Pre-phase (From May - July, 2018): Proceeded meeting with supervisors:

Prof Tran Hong Con, Hanoi University of Science (HUS); Prof Takashi Higuchi, Ritsumeikan University Collected information of the topic and related documents from professors

❖ Phase 1: Preliminary Examination (From July - September, 2018):

o Establish detail research procedure, including time and budget management

o Research scope, site selection and methodology selection

o Sample Collection for Rain Season (August) and Dry Season (December)

❖ Phase 2: Sample Analysis (September 2018 – March 2019):

o Total As content in samples to provide baseline for evaluation

o Quality Control + Method Validation

o Acid condition (pH =1) Leaching Test (rain + dry season)

o Alkaline condition (pH = 10.08) Leaching Test (rain + dry season)

o Acid rain condition (pH = 4.20) Leaching Test (rain + dry season)

o Seawater condition (pH = 7.76) Leaching Test (rain + dry season)

o Distribution of toxicity

❖ Phase 3: Data Treatment + Interpretation (April 2019)

❖ End-Phase: Writing (April – May 2019) + Defense (June 2019)

2 Methodology and Apparatus

2.1 Sampling and Collection

2.1.1 Introduction of Pha Lai Thermal Power Plant

Pha Lai Thermal Power Plant (PLTPP) is one of the oldest coal power facility in Vietnam It was originally designed with USSR’s combustion technology and went into operation in 1980 as one of the symbols for friendship between two nations The initial capacity was only 440 MW, powered by 4 turbines (110 MW each) During 1980s-1990s, such capacity contributed in greatest amount to the electricity grid of Northern Vietnam and only became second when Hoa Binh Hydropower Plant (1,920 MW) was installed in 1994 In late 1990s, the position of Pha Lai Thermal Power Plant was recovered with new expansion of two more modern turbines, 300 MW each, raising total electric capacity to 1040 MW in 2001 However, as new standards for coal Power are frequently promulgated, both in terms of technical improvement and environmental well-beings, Pha Lai Power Plant has been regarded as one of the most backward station in the North of Vietnam Yet this facility is also one of the most representative examples for many similar Power Plants that has been serving for long period of time and beyond The accumulated fly ash produced by these stations also holds a very large proportion

in total national fly ash reserve Therefore, PLTPP has all virtue to be chosen as target of this study

Table II.1.1 gives information on detail technical design of Pha Lai Thermal

Power Plant

TECHNICAL DESIGN PHA LAI 1 PHA LAI 2

Total Electricity Generation 2.86 bils kWh/yr 3.68 bils kWh/yr

Steel pipe:

ɸ = 4.5m

With regard to geographical characteristic, Pha Lai Thermal Power Plant (both 1&2) is located in Pha Lai Ward, Chi Linh City, Hai Duong Province (65km from Hanoi) The area is lying at the crossroad of 3 rivers: Cau River (flowing in from North West), Luc Nam River (flowing in from North-East) and Duong River (going nearby, from West to South) The population of Pha Lai ward is 21.309 people (updates in 2010) spreading in the area of 13.825 km2 There are two main wind directions: North East and North West The open terrain plus wind coming from both directions help disperse flue gas from Plant’s stack to surrounding area robustly Pha Lai Thermal Power Plant possesses several ash ponds scattering around community areas The biggest impoundment is located up in a mountain 3.2 km from the Plant, while some smaller storage site are placed in the North, near Luc Nam tributary where fly ash and coal slag can be transferred conveniently in pipeline As the area is surrounded by rivers, it can be suggested that groundwater table remains relatively adequate and therefore, the leaching activities are more likely to impose effects to the adjacent community

2.1.2 Sampling Method

Based on weather patterns, our group conducted 2 sampling periods in Rain Season (16-17th August 2018) and Dry Season (13-14th January 2019) For each point, we collected the same amount of sample in both sampling trip The accurate coordinates are logged with GPSMAP® 78, Garmin (visit Annex for more detail) Equipment for sampling trip includes: PET Bottles (sufficient for water sampling), connection cord (x1), bucket (x1), parafilm (sufficient), clinging film (sufficient), shovel (x1), plastic zip bag (sufficient), filter paper with pore size = 8 µm (ɸ =

125mm, Whatman), plastic funnel (x3) All equipment were provided by MEE laboratory, Environmental Chemistry Laboratory, HUS and personal funding

VJU-Figure II.1.1 Sampling Map for both Rain Season and Dry Season (Source: All copyright of original capture

belongs to Google Map; edited and labeled by To Hoang Nguyen)

The overall strategy could be divided into 4 separate tasks:

• Task 1: River Sampling

➢ Survey area, select sampling points following water streams (approx 200m in distance)

➢ There are 2 complementary samples that were not collected in Rain Season trip: Cau River and Luc Nam River These samples were taken only in Dry Season trip

• Task 2: South West Soil Sampling

➢ Survey area, select sampling points based on the predicted path of wind dispersion: North East → South West (approx 200m – 250m

in distance)

➢ Soil samples were taken by removing 10cm of top soil, then taking 1-2kg of soil into zip bag, sealed

➢ South West (SW) samples are denoted from No.8 -No.17 in map

• Task 3: North West Soil Sampling

➢ Similar to Task 2 in terms of Procedure

➢ North West (NW) samples were taken in the river bank of opposite site to PLTPP, therefore there will be no connection with ground water of Pha Lai area The major factor contributing to Arsenic existence might merely be from the settling of dispersive F.A in South East – North West path

➢ North West samples are denoted from No.18 – No.22 in map

• Task 4: Ash Pond Sampling

➢ Ash Pond sediment samples were collected in the same manner with soil sample

➢ Ash Pond samples were collected in 3 different areas to ensure the representative for the whole area However some sectors, which were too far with no transport available, could not be examined

➢ Fly Ash samples are denoted from No.5 to No.7 in map

Table II.1.2 Summary of sample types and season variation

Sample Name Sample type Season

Soil/Sed Water Rain Dry

2.2 Storage and Preservation

All soil and sediment samples after being taken from ground were enclosed

through 8µ paper (atmospheric pressure) before captured in PET bottles The cap

of bottles were sealed with parafilm and body covered with clinging film to prevent sample loss Plastic bottle minimize the adsorption of Arsenic into vessel wall, one

of the reasons for analysis bias

In laboratory, water samples were preserved at 4-5°C in refrigerator, VJU-MEE laboratory waiting for analysis Small amount of acid was added to maintain soluble condition for Arsenic

Soil samples were dried naturally in room temperature until brittlely dry texture attained After that, samples were removed from debris and plant roots, milled and sieved through 2mm sieves The fine powder of each sample were respectively transferred to new zip bags, stored in room condition, waiting for analysis

2.3 Physical Characteristic of Fly Ash

An exhaustive understanding of F.A characteristic might be of great essential to explain the potential behaviors in the future With strong and indispensable support

of Professor Higuchi Takashi, Ritsumeikan University and Department of Nano Technology Department, Vietnam-Japan University, Original Fly Ash sample and Ash Pond sample was examined by Scanning Electron Microscope-SEM (JEOL-JSM-IT 100) and Energy-dispersive X-ray Spectroscopy-EDX (Shimadzu, EDX 700)

Specifically, SEM imaging was applied for Original Fly Ash sample while EDX analysis was applied for Ash Pond sample The reason was at the time of Internship

in Ritsumeikan University, Japan (EDX available), Original Fly Ash sample was not yet collected and therefore could only be examined with SEM

2.4 Solid-Liquid Ratio (SLR) Examination

Solid-Liquid Ratio is one of the determining factors for all leaching experiments Low SLR can result in over-dilution of sample that might suppress the substance

under the limit of detection (LOD) High SLR may weaken the release potential of solvents, making leaching test less reliable An appropriate SLR can optimize the experimental condition by optimize the amount of chemical used and soil samples which are limited already

Materials Mixed Fly Ash from Pha Lai 1 & 2 Thermal Power Plant

Apparatus

250ml conical flasks

Horizontal shaker Parafilm

0.45 µ filter paper

Falcon tubes Vacuum

pump pH meter Centrifuge

Solvent HCl 0.1M Diluting 8.4ml HCl 36.5% (Merck) in 1000ml

2.5 Leaching Test under strong acid condition (pH = 1)

The result of SLR test is applied for all other leaching procedure from now on More detail will be presented in Chapter 3: Result and Discussion However, in

order to enhance the understanding of next parts, the ratio is revealed as 20g solid/100g extracting solution (20g:100ml)

Acid condition leaching test has its role to imitate the acidification of F.A during wet aging (Catalano et al., 2012; Deonarine et al., 2016; Pnadey et al, 2011) The concentration of Arsenic released by this solvent will later be used for comparison with total-As content and other methods

Materials All soil and sediment samples

Equipment

and

Apparatus

250ml conical flasks

Horizontal shaker Parafilm

0.45 µ filter paper

Falcon tubes Vacuum

pump pH meter Centrifuge

Solvent HCl 0.1M Diluting 8.4ml HCl 36.5% (Merck) in 1000ml

= 26 extracts = 30 extracts

2.6 Leaching Test under strong alkali condition (pH = 10)

In reverse to acid leaching, alkali condition leaching test aims to simulate the leaching behavior of Arsenic when alkaline solvent present When Class C Fly Ash

is dominant, the abundance of CaO content is likely to cause alkalization of water (Catalano et al., 2012; Deonarine et al., 2016; Pandey et al, 2011) The concentration of Arsenic released by this solvent will later be used for comparison with total-As content and other methods

Materials Original Fly Ash (Mixed F.A) + All soil and sediment samples

Equipment

and

Apparatus

250ml conical flasks

Horizontal shaker Parafilm

0.45 µ filter paper

Falcon tubes Vacuum

pump pH meter Centrifuge

Solvent NaOH 1M Dissolving 40.0 g NaOH (GuangDong Chem)