It is now a well-established fact that air pollution has worsened over the years and the major credit goes to industrial growth. The boilers and stoves are one of the major sources of air pollution from the industries. Therefore, controlling their emissions to a significant extent can lead to the reduction of air pollution. The greenhouse gases of family NOx are important pollutants to be considered in this regard. As per the study by CPCB (2011), in Delhi, industry power plants contribute to approximately 65% of total NOx emissions. Therefore, control of this pollutant may not only lead to the air quality improvement in terms of NOx pollution but will also be beneficial to the environment as NOx cause many ecotoxic effects such as acid rain, eutrophication, ozone formation etc.
There are various emission control technologies available for NOx emissions, which can be categorized into two parts-Combustion Control and Post-combustion technologies in the particular context of boilers. Post-combustion methods are mostly expensive as compared to the combustion control methods and are usually not deployed for boilers having input less than 100 MM Btu/hr. So, the focus should be more on combustion control rather than post-combustion treatment. One such powerful method of combustion control is named Flue Gas Recirculation (FGR) which causes a significant reduction in NOx emissions by recirculating flue gases from the boiler exhaust duct into the main combustion chamber. The essay discusses details of the different aspects of this technology.
Table of Contents
1. INTRODUCTION
2. FLUE GAS RECIRCULATION: DETAILED CONCEPT AND MECHANISM
3. FACTORS TO BE CONSIDERED FOR FGR SYSTEMS
3.1 FGR Rates
3.2 FGR Location
3.3 Air Preheating Temperature
3.4 Oxygen Concentration
4. ADVANTAGES AND DISADVANTAGES
5. CONCLUSION
Research Objectives and Key Topics
The work examines the effectiveness of Flue Gas Recirculation (FGR) as a combustion control technique to reduce nitrogen oxide (NOx) emissions in industrial boilers while analyzing the associated operational trade-offs.
- Mechanisms of thermal NOx reduction via flue gas recirculation.
- Impact of operational parameters like FGR rates and air preheating on emissions.
- Optimization of boiler efficiency versus emission control.
- Analysis of potential drawbacks such as flame instability and vibration issues.
Excerpt from the Book
ADVANTAGES AND DISADVANTAGES
Thermodynamically we know that temperature reduction of the burner directly to reduce emissions would decrease the efficiency but using the formed exhaust in the burner again eventually reduces the temperature without much decrease in the efficiency (Wilson, 2019). The FGR systems also help in saving fuels for feeding the stoker and cooling the fuel beds (The benefits of…., 2018). In this way, there is an improvement in overall boiler efficiency as reported by Yue, Ma and Shi (2020).
However, some studies have also reported that there is a slight reduction in the boiler efficiency when operating the FGR system, especially under the low-load conditions (Zhang et al., 2019; Zajacs, 2020). Also, there are chances of reduction in burner capacity as the air may be replaced by low-oxygen flue gases requiring the burner to be downrated to compensate further resulting in the capacity loss due to a relative rise of temperature in the inlet chamber. This issue can often be encountered by replacing the burner fan. Another problem that persists with the FGR systems is the loss of flame stability. Since the technique is particularly for reducing the emissions which it does quite effectively (more than 50%) but on the other hand, the loss of flame stability may result in higher emissions of carbon monoxide and unburned hydrocarbons (Module 106, 2016; Pett, 2017). Further, in the case of internal flue gas recirculation, the flame may be so unstable that it may cause vibrations in the boilers and the shape of the flame may become difficult to adjust (Praest & Béjar, 2019).
Summary of Chapters
1. INTRODUCTION: Provides an overview of industrial air pollution and identifies Flue Gas Recirculation as a crucial combustion control method for reducing NOx emissions.
2. FLUE GAS RECIRCULATION: DETAILED CONCEPT AND MECHANISM: Explains the working principle of FGR, specifically how recirculating flue gases lowers flame temperature to prevent thermal NOx formation.
3. FACTORS TO BE CONSIDERED FOR FGR SYSTEMS: Details critical variables such as recirculation rates, gas location, air preheating, and oxygen concentration that influence the performance of FGR systems.
4. ADVANTAGES AND DISADVANTAGES: Discusses the trade-offs of using FGR, contrasting improved emission control and fuel savings with potential risks like reduced boiler efficiency and flame instability.
5. CONCLUSION: Synthesizes the study's findings on the effectiveness of FGR and emphasizes the need for future technological improvements to address operational challenges.
Keywords
Flue Gas Recirculation, NOx emissions, industrial boilers, combustion control, thermal NOx, emission reduction, boiler efficiency, flame stability, air preheating, recirculation ratio, oxygen concentration, environmental impact, fuel saving, industrial pollution, combustion mechanisms.
Frequently Asked Questions
What is the core subject of this research paper?
The paper focuses on Flue Gas Recirculation (FGR) as an effective emission control technique to minimize nitrogen oxide (NOx) emissions in industrial boilers.
What are the primary thematic areas covered?
The study covers the mechanisms of burner temperature regulation, the influence of operational factors on emissions, and a comparative analysis of the benefits and drawbacks of FGR systems.
What is the main objective of this study?
The objective is to analyze how FGR can prevent thermal NOx formation and to identify the necessary adjustments for efficient boiler operation when utilizing this technique.
Which scientific method is utilized in this paper?
The paper uses a descriptive analytical review method, synthesizing thermodynamic principles and existing literature to evaluate FGR performance and its impact on boiler operation.
What issues are addressed in the main part of the work?
The main part addresses the design mechanisms of FGR, the impact of specific variables like FGR rates and air preheating temperature, and the practical disadvantages such as flame instability.
Which main keywords characterize this work?
Key terms include Flue Gas Recirculation, NOx emissions, combustion control, boiler efficiency, and flame stability.
How does FGR fundamentally affect boiler combustion?
FGR works by replacing excess oxygen with cooler, inert gases like carbon dioxide and nitrogen, which lowers the combustion flame temperature and thereby inhibits thermal NOx production.
Why is FGR often preferred over post-combustion treatments?
FGR is categorized as a combustion control method, which is generally more cost-effective and accessible for most industrial boilers compared to expensive post-combustion technologies.
What is a common operational problem encountered with FGR?
A significant issue with FGR is the loss of flame stability, which can lead to vibrations in the boiler and the potential production of carbon monoxide due to incomplete combustion.
- Arbeit zitieren
- Lovish Raheja (Autor:in), 2022, Flue Gas Recirculation. An Emission Control Technique for Industrial Boilers, München, GRIN Verlag, https://www.grin.com/document/1263320
