global environmental effects of sulphur hexafluoride (sf6) emissions on climate

Description

ABSTRACT

This work provides information concerning possible global environmental implications a n d personnel safety aspects that should be considered during the commercial uses of sulfur hexafluoride (SF6). Sulfur hexafluoride (SF6)   is an anthropogenically produced compound, mainly used as a gaseous dielectric in gas insulated switchgear power installations. It is a potent greenhouse gas wit h a high global warming potential, and its concentration in the earth atmosphere is rapidly increasing. During its working cycle, SF 6    decomposes under electrical stress, forming toxic byproducts that are a health threat for working personnel in the event of exposure. Several precautions are recommended to avoid personnel exposure  to toxic byproducts: oxyfluoride levels or other byproduct  concentrations in t he operating gas matrix should be traced to predetermine t he overall gas toxicity; contaminants should be systematically considered during maintenance, chamber evacuation and system opening process; small SF6   quantities leaking in to air or stagnated pollutant concentrations in t he operating field should be analyzed and compared to the threshold limit values an d permissible exposure levels. New system design rules (i.e., hermetically sealed gas compartments, gas recycling or disposal in the field area) an d different handling policies—both during maintenance and final disposal—now should be considered globally to pro- vide for environmental and personnel safety.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM AND OBJECTIVE OF THE PROJECT
• SCOPE AND LIMITATIONS OF THE STUDY
• RESEARCH QUESTIONS
• SIGNIFICANCE OF THE STUDY
• RESEARCH METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.0     LITERATURE REVIEW
2.1      OVERVIEW OF SULFUR HEXAFLUORIDE (SF₆)

2.2     THE HISTORY OF SULPHUR HEXAFLUORIDE

CHAPTER THREE

3.1     SF6: APPLICATIONS AND RISKS

3.2     GLOBAL WARMING POTENTIAL FOR SF 6

3.3     TOXIC BYPRODUCTS OF SF₆ IN THE WORKING ENVIRONMENT

CHAPTER FOUR

4.1      REMEDIATION – REQUIREMENTS FOR AN ALTERNATIVE TO REPLACE SF₆

4.3     ALTERNATIVES TO SF₆ IN RENEWABLE ENERGY TECHNOLOGY

4.3     REMANUFACTURING AND REMEDIATION OF SF₆ EMISSIONS

4.3     SUCCESSFUL REMEDIATION

CHAPTER FIVE

• CONCLUSIONS
• RECOMMENDATION

CHAPTER ONE

1.0                                             INTRODUCTION

1.1                              BACKGROUND OF THE STUDY

Sulfur hexafluoride (SF₆) is an anthropogenically produced compound, mainly used as a gaseous dielectric in gas insulated switchgear power installations. It is a potent greenhouse gas with a high global warming potential, and its concentration in the earth atmosphere is rapidly increasing. During its working cycle, SF6 decomposes under electrical stress, forming toxic byproducts that are a health threat for working personnel in the event of exposure. Several precautions are recommended to avoid personnel exposure to toxic byproducts: oxyfluoride levels or other byproduct concentrations in the operating gas matrix should be traced to predetermine the overall gas toxicity; contaminants should be systematically considered during maintenance, chamber evacuation and system opening process; small SF6 quantities leaking into air or stagnated pollutant concentrations in the operating field should be analyzed and compared to the threshold limit values and permissible exposure levels. New system design rules (i.e., hermetically sealed gas compartments, gas recycling or disposal in the field area) and different handling policies–both during maintenance and final disposal–now should be considered globally to provide for environmental and personnel safety.

As scientists and citizens become more concerned with global warming and the impact of greenhouse gases such as carbon dioxide (which recently breached 400 ppm), the companies involved in the distribution of energy will be required to respond. This work focuses on the most powerful greenhouse gas in the world – sulphur hexafluoride (SF₆) and the climatic impacts it imposes. It has been used in electrical equipment such as gas-circuit breakers since 2006, which are used to quench electrical arcs. Its usage increased due to the favourable properties that the gas possesses; these include high dielectric strength and thermal stability for example. This has created problems due to its global warming potential in relation to the leak rate of the electrical equipment. The UKs wind farm industry heavily invested in the use of SF₆ in turbine generators, leading to notable leaked emissions of the gas over the last decade. This has prompted remediation efforts across the UK and in Europe to reduce its usage and to develop alternatives for the near future.

Alternative gases that are currently being developed are CF₃I and different fluoronitriles, these contain similar properties to SF₆, offering a promising and cleaner future. Remediation and remanufacturing are also a solution to help reduce the consequences of SF₆, providing environmental and economic benefits.

This study focuses on the global use of sulphur hexafluoride (SF₆) and it impact it posses in our environment.

1.2                                           PROBLEM STATEMENT

Sulphur hexafluoride (SF₆) has been one of the most popular material used in the world today because of its versatile application in electrical industries. The popularity and applications do not hinder its effect on the climate thereby affecting human beings on earth which most people are not aware of. This study was carried out to bring to the knowledge of all reader to the global environmental effect of sulphur hexafluoride (SF₆).

1.3                                 AIM AND OBJECTIVES OF THE STUDY

The main aim of this study is do discuss the global environmental effects of sulphur hexafluoride (SF₆). The objectives are:

1. To understand the environmental impact of sulphur hexafluoride (SF₆)
2. To study the remedy to the negative impact of sulphur hexafluoride (SF₆) on our environment.

• To study the benefit of using sulphur hexafluoride (SF₆).

1.4                                           SCOPE OF THE STUDY

This work provides information concerning possible global environmental implications and personnel safety aspects that should be considered during the commercial uses of sulfur hexafluoride (SF6).

1.5                                     RESEARCH QUESTIONS

At the end of this work, answer to the following questions shall be made known:

1. How does sulfur hexafluoride affect climate?
2. How does SF6 contribute to global warming?

• Is SF6 a greenhouse gas?

1.6                               SIGNIFICANCE OF THE STUDY

This study will become useful to all electrical students and readers of this work in that it will expose their knowledge to the uses of sulphur hexafluoride (SF₆) and also help them to understand the negative impact of sulphur hexafluoride (SF₆) in our environment. To electrical engineers, this study will help them to understand how sulphur hexafluoride (SF₆) can be generated from electrical equipment and how they hand handle it in other to be safe.

1.7                                             RESEARCH METHODOLOGY

In the course of carrying this study on the global environmental effect of sulphur hexafluoride (SF₆), numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.

1.8                                     PROJECT ORGANIZATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.

CHAPTER FIVE

RECOMMENDATIONS   AND   CONCLUSIONS

It is true that equipment incorporating SF6 has a demonstrated value for society. However, the environmental risks (either in the global atmosphere or in the working environment) strongly dictate that improved handling procedures and innovative designs of GIS constructions will have to be adopted to minimize leaks to the atmosphere. CIGRE recommends t hat at the end of life of SF6   equipment, t he electrically stressed gas will either have to be

6

recycled, ⁵¹ or reduced to environmentally compatible end- productscan be destroyed by thermal decomposition in industrial waste treatment furnaces at  elevated temperatures (>1,100 °C) (Maut et al, 2016). In t his process the constituents of SF6 (i.e., sulfur a n d fluorine) are converted into

2                                                                                                         3

the naturally occurring materials CaSO ₄ (gypsu m) and  CaF (fluorspar) by reacting with CaCO   (calcite). The excess of CaCO ₃ is required to ensure the reaction with any HF or H₂S that may be produced in the furnace by the thermal decomposition of SF₆. Gypsum and fluorspar can be land filled or possibly used as raw materials in other processes (Maut et al, 2016)

The problems related to SF 6 and the power industries are not without solutions an d may eventually lead to new opportunities (e.g., in situ recycling or disposal, development of alternative gaseous insulators, or alternative high voltage technologies). Besides current efforts ⁵³ and recommendations to control the release of electrically stressed SF6 , the introduction of addition al environmental standards concerning recycling procedures or on-site gas purity control have yet to become available. A comprehensive systematic online monitoring and in situ analysis of the gas concentrations would be beneficial towards (Maut et al, 2016).

• Personnel safety—toxicity control of t he SF 6 gas matrix could be based upon disulfur decafluoride or oxyfluoride detection levels;
• Locating leaks—help to curtail undesirable release to t he atmosphere; an d
• Component reliability and assurance—systematic examination of certain byproduct concentrations can be used as a maintenance prognosis tool (e.g., t he presence of high CO₂ levels in t he SF₆ matrix of a GIS plan t singularly identifies filter sorption saturation, while t he presence of metal fluorides possibly originating from the erosion of field smoothing devices should be immediately removed as it may induce surface fatigue (or dam- age) on the solid insulants of the installation) (Maut et al, 2016).  Thus, the on-line monitoring an d analysis techniques, although substantially increasing t he regular running cost of t he equip men t, could be proved to be beneficial for t he power