Second Generation Advanced Reburning for High Efficiency NOx Control

This project is designed to develop a family of novel NO{sub x} control technologies, called Second Generation Advanced Reburning (SGAR) which has the potential to achieve 90+ NO{sub x} control in coal fired boilers at a significantly lower cost than Selective Catalytic Reduction. The ninth reporting period in Phase II (October 1-December 31, 1999) included preparation of the 10 x 10{sup 6} Btu/hr Tower Furnace for tests and setting the SGAR model to predict process performance under Tower Furnace conditions. Based on results of previous work, a paper has been prepared and submitted for the presentation at the 28 Symposium (International) on Combustion to be held at the University of Edinburgh, Scotland

Preliminary Field Evaluation of Mercury Control Using Combustion Modifications

In this project EER conducted a preliminary field evaluation of the integrated approach for mercury (Hg) and NO{sub x} control. The approach enhanced the 'naturally occurring' Hg capture by fly ash through combustion optimization, increasing carbon in ash content, and lowering ESP temperature. The evaluation took place in Green Station Units 1 and 2 located near Henderson, Kentucky and operated by Western Kentucky Energy. Units 1 and 2 are equipped with cold-side ESPs and wet scrubbers. Green Station Units 1 and 2 typically fire two types of fuel: a bituminous coal and a blend of bituminous coals based on availability. Testing of Hg emissions in Unit 2 without reburning system in operation and at minimum OFA demonstrated that efficiencies of Hg reduction downstream of the ESP were 30-40%. Testing also demonstrated that OFA system operation at 22% air resulted in 10% incremental increase in Hg removal efficiency at the ESP outlet. About 80% of Hg in flue gas at ESP outlet was present in the oxidized form. Testing of Hg emissions under reburning conditions showed that Hg emissions decreased with LOI increase and ESP temperature decrease. Testing demonstrated that maximum Hg reduction downstream of ESP was 40-45% at ESP temperatures higher than 300 F and 60-80% at ESP temperatures lower than 300 F. The program objective to demonstrate 80% Hg removal at the ESP outlet has been met

Second Generation Advanced Reburning for High Eficiency NO(x) Control

This project is designed to develop a family of novel NO{sub x} control technologies, called Second Generation Advanced Reburning which has the potential to achieve 90+% NO{sub x} control in coal fired boilers at a significantly lower cost than SCR. The sixth reporting period (January I - March 31, 1997) included both experimental and modeling activities. New kinetic experimental data for high-temperature decomposition of sodium carbonate were obtained in a flow reactor at the University of Texas in Austin. Pilot scale combustion tests in a 1.0 MMBtu/hr Boiler Simulator Facility were continued with firing coal and using natural gas as reburn fuel. The results demonstrate that over 90% NO control is achievable by injecting one or two N-agents with sodium promoters into the reburning zone and with the overfire air. Advanced reburning technologies does not cause significant byproduct emissions. The AR kinetic model was updated to include chemical reactions of sodium carbonate decomposition. Modeling was conducted on evaluation of the effect of sodium on process kinetics in the rebuming zone. This study revealed that increasing or decreasing radical concentrations in the presence of sodium can significantly affect the reactions responsible for NO reduction under fuel-rich conditions. The effect of mixing time on performance with sodium was also evaluated. Initial activities on engineering design methodology for second generation AR improvements are described

Second Generation Advanced Reburning for High Efficiency NOx Control

This project develops a family of novel Second Generation Advanced Reburning (SGAR) NO{sub x} control technologies, which can achieve 95% NO{sub x} control in coal fired boilers at a significantly lower cost than Selective Catalytic Reduction (SCR). The conventional Advanced Reburning (AR) process integrates basic reburning and N-agent injection. The SGAR systems include six AR variants: (1) AR-Lean--injection of the N-agent and promoter along with overfire air; (2) AR-Rich--injection of N-agent and promoter into the reburning zone; (3) Multiple Injection Advanced Reburning (MIAR)--injection of N-agents and promoters both into the reburning zone and with overfire air; (4) AR-Lean + Promoted SNCR--injection of N-agents and promoters with overfire air and into the temperature zone at which Selective Non-Catalytic Reduction (SNCR) is effective; (5) AR-Rich + Promoted SNCR--injection of N-agents and promoters into the reburning zone and into the SNCR zone; and (6) Promoted Reburning + Promoted SNCR--basic or promoted reburning followed by basic or promoted SNCR process. The project was conducted in two phases over a five-year period. The work included a combination of analytical and experimental studies to confirm the process mechanisms, identify optimum process configurations, and develop a design methodology for full-scale applications. Phase I was conducted from October, 1995 to September, 1997 and included both analytical studies and tests in bench and pilot-scale test rigs. Phase I moved AR technology to Maturity Level III-Major Subsystems. Phase II is conducted over a 45 month period (October, 1997-June, 2001). Phase II included evaluation of alternative promoters, development of alternative reburning fuel and N-Agent jet mixing systems, and scale up. The goal of Phase II was to move the technology to Maturity Level I-Subscale Integrated System. Tests in combustion facility ranging in firing rate from 0.1 x 10{sup 6} to 10 x 10{sup 6} Btu/hr demonstrated the viability of the AR technology. The performance goals of the project to reduce NO{sub x} by up to 95% with net emissions less than 0.06 lb/10{sup 6} Btu and to minimize other pollutants (N{sub 2}O and NH{sub 3}) to levels lower than reburning and SNCR have been met. Experimental data demonstrated that AR-Lean + SNCR and Reburning + SNCR are the most effective AR configurations, followed by AR-Lean and AR-Rich. Promoters can increase AR NO{sub x} reduction efficiency. Promoters are the most effective at small amounts of the reburning fuel (6-10% of the total fuel heat input). Promoters provide the means to improve NO{sub x} reduction and simultaneously decrease the amount of reburning fuel. Tests also showed that alkali-containing compounds are effective promoters of the AR process. When co-injected with N-agent, they provide up to 25 % improvement in NO{sub x} reduction. A detailed reaction mechanism and simplified representation of mixing were used in modeling of AR processes. Modeling results demonstrated that the model correctly described a wide range of experimental data. Mixing and thermal parameters in the model can be adjusted depending on characteristics of the combustion facility. Application of the model to the optimization of AR-Lean has been demonstrated. Economic analysis demonstrated a considerable economic advantage of AR technologies in comparison with existing commercial NO{sub x} control techniques, such as basic reburning, SNCR, and SCR. Particularly for deep NO{sub x} control, coal-based AR technologies are 50% less expansive than SCR for the same level of NO{sub x} control. The market for AR technologies is estimated to be above $110 million

Second Generation Advanced Reburning for High Efficiency NOx Control

This project is designed to develop a family of novel NO{sub x} control technologies, called Second Generation Advanced Reburning (SGAR) which has the potential to achieve 90+% NO{sub x} control in coal-fired boilers at a significantly lower cost than SCR. The twelfth reporting period in Phase II (July 3-October 15, 2000) included design validation AR-Lean tests (Task No.2.6) in the 10 x 10{sup 6} Btu/hr Tower Furnace. The objective of tests was to determine the efficiency of AR-Lean at higher than optimum OFA/N-Agent injection temperatures in large pilot-scale combustion facility. Tests demonstrated that co-injection of urea with overfire air resulted in NO{sub x} reduction. However, observed NO{sub x} reduction was smaller than that under optimum conditions

Ethanol reforming in non-equilibrium plasma of glow discharge

The results of a detailed kinetic study of the main plasma chemical processes in non-equilibrium ethanol/argon plasma are presented. It is shown that at the beginning of the discharge the molecular hydrogen is mainly generated in the reaction of ethanol H-abstraction. Later hydrogen is formed from active H, CH2OH and CH3CHOH and formaldehyde. Comparison with experimental data has shown that the used kinetic mechanism predicts well the concentrations of main species at the reactor outlet.Comment: 16 pages, 8 figure

BIOMASS REBURNING - MODELING/ENGINEERING STUDIES

This project is designed to develop engineering and modeling tools for a family of NO{sub x} control technologies utilizing biomass as a reburning fuel. The sixth reporting period (January 1--March 31, 1999) included CFD modeling and assessment of available experimental and modeling data on biomass reburning. Experimental and modeling data obtained within scope of this and Phase II SBIR USDA projects were reviewed and analyzed. This work was necessary to summarize available data and to make decision about additional efforts that are necessary for successful completion of the DOE FETC project. These efforts resulted in preparation of the paper entitled ''Kinetic Study of Biomass Reburning'' which was presented at the 1999 Joint Meeting of the United States Sections of the Combustion Institute. The paper is included in Attachment A

MINIMIZATION OF CARBON LOSS IN COAL REBURNING

This project develops Fuel-Flexible Reburning (FFR), which combines conventional reburning and Advanced Reburning (AR) technologies with an innovative method of delivering coal as the reburning fuel. The overall objective of this project is to develop engineering and scientific information and know-how needed to improve the cost of reburning via increased efficiency and minimized carbon in ash and move the FFR technology to the demonstration and commercialization stage. Specifically, the project entails: (1) optimizing FFR with injection of gasified and partially gasified fuels with respect to NO{sub x} and carbon in ash reduction; (2) characterizing flue gas emissions; (3) developing a process model to predict FFR performance; (4) completing an engineering and economic analysis of FFR as compared to conventional reburning and other commercial NO{sub x} control technologies, and (5) developing a full-scale FFR design methodology. The project started in August 2000 and will be conducted over a two-year period. The work includes a combination of analytical and experimental studies to identify optimum process configurations and develop a design methodology for full-scale applications. The first year of the program included pilot-scale tests to evaluate performances of two bituminous coals in basic reburning and modeling studies designed to identify parameters that affect the FFR performance and to evaluate efficiency of coal pyrolysis products as a reburning fuel. Tests were performed in a 300 kW Boiler Simulator Facility to characterize bituminous coals as reburning fuels. Tests showed that NO{sub x} reduction in basic coal reburning depends on process conditions, initial NO{sub x} and coal type. Up to 60% NO{sub x} reduction was achieved at optimized conditions. Modeling activities during first year concentrated on the development of coal reburning model and on the prediction of NO{sub x} reduction in reburning by coal gasification products. Modeling predicted that composition of coal gasification products depends on gasification temperature. At lower temperature yield of hydrocarbons is high which results in higher efficiency of NO{sub x} control. As temperature decreases, yield of hydrocarbons increases and CO and H{sub 2} yields decrease

SECOND GENERATION ADVANCED REBURNING FOR HIGH EFFICIENCY NOx CONTROL

This project is designed to develop a family of novel NO{sub x} control technologies, called Second Generation Advanced Reburning which has the potential to achieve 90+ NO{sub x} control in coal fired boilers at a significantly lower cost than Selective Catalytic Reduction. The sixth reporting period in Phase II (January 1-March 31, 1999) included experimental activities and combined chemistry-mixing modeling on advanced gas reburning. The goal of combustion tests was to continue the work on identifying prospective promoters for the advanced reburning process. Tests were conducted in Controlled Temperature Tower (CTT) and Boiler Simulator Facility (BSF). Tests showed that some promoters significantly affect the reburning process when co-injected with NH{sub 3} . The promoters injected into reburning zone without NH{sub 3} in the amount 30 ppm do not significantly affect the reburning process. The modeling effort was focused on the description of Na effect on CO emissions in advanced reburning. Increase in CO concentration in flue gas upon Na injection results from inhibition of CO oxidation by Na species in the burnout zone