Chapter 2 Selective Catalytic Reduction

Chapter 2 Selective Catalytic Reduction

John L. Sorrels Air Economics Group Health and Environmental Impacts Division Office of Air Quality Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, NC 27711

David D. Randall, Karen S. Schaffner, Carrie Richardson Fry RTI International Research Triangle Park, NC 27709

May 2016

Chapter 2 ? Selective Catalytic Reduction

CONTENTS

2. Selective Catalytic Reduction ..................................................................................................... 2 2.1 Introduction...................................................................................................................... 2 2.2 Process Description........................................................................................................ 10 2.2.1 Reduction Chemistry, Reagents, and Catalyst ................................................... 11 2.2.2 SCR Performance Parameters ............................................................................ 16 2.2.3 SCR System Configurations .............................................................................. 29 2.2.4 SCR System Primary Equipment....................................................................... 35 2.2.5 SCR System Auxiliary Equipment .................................................................... 42 2.2.6 Other Considerations ......................................................................................... 45 2.3 Design Parameters ......................................................................................................... 50 2.3.1 Boiler Heat Input................................................................................................ 51 2.3.2 Heat Rate Factor ................................................................................................ 52 2.3.3 System Capacity Factor ..................................................................................... 52 2.3.4 Inlet NOx and Stack NOx ................................................................................... 54 2.3.5 NOx Removal Efficiency.................................................................................... 54 2.3.6 NOx Removal Rates ........................................................................................... 54 2.3.7 Actual and Normalized Stoichiometric Ratios .................................................. 55 2.3.8 Flue Gas Flow Rate............................................................................................ 55 2.3.9 Space Velocity and Area Velocity ..................................................................... 56 2.3.10 Theoretical NOx Removal Efficiency ................................................................ 57 2.3.11 Catalyst Volume................................................................................................. 58 2.3.12 SCR Reactor Dimensions .................................................................................. 59 2.3.13 Estimating Reagent Consumption and Tank Size.............................................. 61 2.4 Cost Analysis ................................................................................................................. 62 2.4.1 Total Capital Investment.................................................................................... 64 2.4.2 Total Annual Costs ............................................................................................ 72 2.5 Example Problem #1 ? Utility Boiler ............................................................................ 79 2.5.1 Design Parameter Example #1........................................................................... 80 2.5.2 Cost Estimation Example................................................................................... 84 2.6 Example Problem #2 ? Industrial Boiler ....................................................................... 87 2.6.1 Design Parameter Example #2........................................................................... 88 2.6.2 Cost Estimation Example #2.............................................................................. 91 References............................................................................................................................... 96

Chapter 2 ? Selective Catalytic Reduction

2. SELECTIVE CATALYTIC REDUCTION

2.1 Introduction

Selective catalytic reduction (SCR) has been applied to stationary source fossil fuel?fired combustion units for emission control since the early 1970s and is currently being used in Japan, Europe, the United States, and other countries. In the U.S. alone, more than 1,000 SCR systems have been installed on a wide variety of sources in many different industries, including utility and industrial boilers, process heaters, gas turbines, internal combustion engines, chemical plants, and steel mills [1]. Other sources include fluid catalytic cracking units (FCCUs), ethylene cracker furnaces, nitric acid plants, catalyst manufacturing processes, nitrogen fixation processes, and solid/liquid or gas waste incinerators [2, 3]. In the U.S., SCR has been installed on more than 300 coal-fired power plants ranging in size from ................
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