Effect of Reagent Injection Amount and Hole Size on NOx Reduction by SNCR in a CO Boiler

Abstract

presented an experimental and kinetic study of the influence of additives on the SNCR process. The experimental results prove that the use of such additives allows the NO reduction process to be more efficient at lower temperatures. Ayoub et al. [3] performed an experimental study on the NOx reduction from gas stream by SNCR using urea as a reducing agent. Different types of additives were added during SNCR process to improve NOx reduction efficiency and enlarge temperature window. Anionic surfactants were found to give maximum efficiency for NOx reduction and provide maximum range for the temperature window. Nguyen et al. [4] studied the NOx controlling in a municipal solid waste incinerator by SNCR using urea-water solution by means of computational fluid dynamics (CFD) simulation, which is validated with on-site experiments. At normalized stoichiometric ratio (NSR) = 1.8, 70% NO reduction is obtained from on-site experiments, while 66% NO reduction is from the CFD simulation. Carbon monoxide (CO) boilers play an important role in the petroleum-refining process. They can retrieve the thermal energy of CO from the regenerator. A CO boiler utilizes the burning gas (CO) from the regenerator as fuel, and CO then reacts to form CO2 and release large amount of heat. The hightemperature flue gas flows through the superheating section and exchanges heat with water in the cooling tubes to produce superheated steam that can be used by other equipment.The performance of a CO boiler can have a detrimental influence on operation and production in petrochemical industries, steel & iron industries and other relevant industries.This study adopts a CO boiler from the Formosa Petrochemical Corporation (FPC) in Taiwan as the model for numerical investigation [5,6]. Configuration and dimensions of the CO boiler investigated are shown in Fig. 1. In the author„s previous studies, the combustion and fluid flow [5] and the application of reburning technology to the NOx reduction in the FPC CO boiler [6] were investigated. In this study, the discussion is focused on the application of SNCR method to the NOx reduction in the FPC CO boiler. Reducing agent for the SNCR method is ammonia (NH3). The influences of injection amount and hole size of the reducing agent on SNCR method are inspected.