Comprehensive Modeling Study on Fuel Gas Reburn in an Opposed Wall Fired Boiler

2007 ◽  
Author(s):  
Q. H. Nguyen ◽  
W. Zhou ◽  
G. Xu ◽  
L. W. Swanson ◽  
D. K. Moyeda
Keyword(s):  
Gas Flow ◽  
Nox Reduction ◽  
Injection System ◽  
Cfd Modeling ◽  
Performance Impact ◽  
Fuel Gas ◽  
Gasification Process ◽  
Underground Gasification ◽  
Coal Deposits ◽  
Economical Feasibility

GE conducted engineering and modeling studies to evaluate the feasibility of applying gas reburn technology on Eskom’s Majuba Unit 5 (710 MWe). The key objective of the study was to evaluate the technical and economical feasibility of utilizing a low-calorific fuel gas as a reburn fuel. The fuel gas is produced from an underground gasification process of the Majuba coal deposits, which are difficult to mine. The studies include: (1) develop a conceptual gas reburn injection system that will serve as a basis for the boiler performance impact and economic studies, (2) evaluate mixing performance of the gas reburn system and evaluate impacts of gas reburn on the furnace thermal and species profiles using computational fluid dynamics (CFD) modeling, (3) evaluate impacts of gas reburn on the boiler thermal performance using heat transfer modeling, (4) evaluate NOx reduction potential of the gas reburn systems, and (5) evaluate the economical feasibility of applying gas reburn technology to the Majuba boiler. The study indicates that the proposed reburn fuel and OFA injection systems will provide adequate mixing and reasonable residence time for the reburn application. The potential impacts on boiler performance with injection of the low-calorific fuel gas include the flue gas flow rate, attemperation rate and ID fan capacity. The detailed modeling approach and results are presented in this paper.

Use of CFD Modeling for Design of NOx Reduction Systems in Utility Boilers

2002 ◽  
Author(s):  
Bradley Adams ◽  
Marc Cremer ◽  
James Valentine ◽  
Venkata Bhamidipati ◽  
David O’Connor ◽  
...  
Keyword(s):  
Nox Reduction ◽  
Field Testing ◽  
Nox Emission ◽  
Injection System ◽  
Cfd Modeling ◽  
Unburned Carbon ◽  
Port Placement ◽  
Utility Boilers ◽  
Ammonia Slip ◽  
Combustion Optimization

CFD modeling has found increasing use in the design and evaluation of utility boiler retrofits, combustion optimization and NOx reduction technologies. This paper reviews two recent examples of CFD modeling used in the design and evaluation of NOx reduction technologies. The first example involves the staging of furnace combustion through use of overfire air (OFA) to reduce NOx emission in a B&W opposed-wall fired pc furnace. Furnace simulations identified locations of highest flue gas mass flows and highest CO concentrations and were used to identify OFA port placement for maximum NOx reduction with lowest increases in unburned carbon in fly ash and CO emission. Simulations predicted a 34% reduction in NOx emission with OFA. The second example summarizes the design and application of RRI with OFA and SNCR in a 138 MW cyclone-fired boiler. Simulations were used to design an aminebased injection system for the staged lower furnace and to evaluate NOx reduction and ammonia slip of the RRI system. Field-testing confirmed modeling predictions and demonstrated that the RRI system alone could achieve 25–30% NOx reduction beyond OFA levels with less than 1 ppm ammonia slip and that RRI in combination with SNCR could achieve 50–55% NOx reduction with less than 5 ppm slip.

NOx Emissions in a Steel Reheat Furnace Firing By-Product Fuels

2001 ◽  
Author(s):  
Bradley R. Adams ◽  
Dave H. Wang
Keyword(s):  
Low Cost ◽  
Nox Reduction ◽  
Coke Oven ◽  
Cfd Modeling ◽  
Stoichiometric Ratio ◽  
Nox Emissions ◽  
Confined Space ◽  
Nox Formation ◽  
Reheat Furnace ◽  
Bottom Zone

Abstract A DOE-funded program was used to understand the mechanisms that control the formation of NOx during the combustion of steelmaking by-product fuels and to investigate possible low-cost control options to minimize the NOx emissions. This paper discusses the CFD modeling results of NOx emissions in a reheat furnace. The reheat furnace has a total of 20 burners distributed over three firing zones. The furnace is fired at a rate of 250 × 106 Btu/hr and an overall stoichiometric ratio of 1.06 (fuel lean). Fuels with heating values of approximate 500 Btu/SCF were examined, including coke oven gas (COG), blast furnace gas (BFG) and a blend of COG, BFG, natural gas (NG) and nitrogen. A good range of process variables was modeled to examine effects of fuel type, air preheat, stoichiometric ratio, firing rate and burner stoichiometry distribution on NOx emissions. Modeling results indicated that NOx formation in the reheat furnace is dominated by thermal NO, with some variation depending on the fuel fired. Temperature profiles showed an effective separation of the furnace interior into top and bottom zones as a result of the steel slab barrier. Higher temperatures characterized the bottom zone and elevated NOx levels as a result of the confined space and enhanced fuel air mixing provided by the slab supports. Results also showed that reburning of NOx plays a significant role in final NOx emissions with 30–40% of NOx formed being reduced by reburning in most cases. Modeling identified that operating the side burners in each burner zone slightly substoichiometric (while maintaining the overall furnace stoichiometry at 1.06) provided significant NOx reduction via reburning. NOx reductions of 23% and 30% were predicted when firing with COG and COG-NG-Air fuels, respectively. Overall furnace exit temperatures and heat flux profiles were not significantly affected by the biased firing.

Chemistry of the Gasification of Carbonaceous Raw Material

2021 ◽  
Vol 1045 ◽  
pp. 67-78
Author(s):  
Pavlo Saik ◽  
Roman Dychkovskyi ◽  
Vasyl Lozynskyi ◽  
Volodymyr Falshtynskyi ◽  
Edgar Caseres Cabana ◽  
...  
Keyword(s):  
Gas Flow ◽  
Experimental Studies ◽  
Reaction Channel ◽  
Raw Material ◽  
Gas Generator ◽  
Equal Concentration ◽  
Gasification Process ◽  
Gasification Rate ◽  
Gasification Products ◽  
Gas Flow Velocity

The paper represents the studies of the process of carbonaceous raw material gasification. The initial material is represented by bituminous coal of grade H with the carbon (C) content of 79.2-85.3 %. Experimental studies have been used to substantiate the parameters of combustible generator gases (СО, Н2, СН4) output depending on the temperature of a reduction zone of the reaction channel and gas flow velocity along its length. It has been identified that the volume of the raw material input to be used for gasification process changes in direct proportion depending on the amount of burnt-out carbon and blow velocity. The gasification is intensified in terms of equal concentration of oxygen and carbon in the reaction channel of an underground gas generator. The gasification rate is stipulated by the intensity of chemical reactions, which depend immediately on the modes of blow mixture supply. Moreover, they depend directly on the intensity of oxygen supply to the coal mass and removal of the gasification products.

scholarly journals Nitrogen Oxide Reduction by Staged Combustion of Biomass Gas in Gas Turbines — A Modeling Study of the Effect of Mixing

1999 ◽  
Author(s):  
Edgardo G. Coda Zabetta ◽  
Pia T. Kilpinen ◽  
Mikko M. Hupa ◽  
Jukka K. Leppälahti ◽  
C. Krister O. Ståhl ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Nox Reduction ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Process Variables ◽  
Staged Combustion ◽  
Fuel Gas ◽  
Effective Option ◽  
Fuel Mixing ◽  
Lower Temperature

Detailed chemical kinetic modeling has been used to study the reduction of nitrogen oxides at gas turbine (GT) combustor conditions. A gas from gasification of wood with air has been used as the fuel. An air-staged combustion technique has been adapted. In our previous study a simple plug flow model was used to study the effects of pressure and temperature among others process variables. The air-fuel mixing was assumed perfect and instantaneous. Results showed the NOx reduction mainly affected by both pressure and temperature. The aim of the present work is to establish the effect of air-fuel mixing delay on NOx predictions and to extrapolate indications options for GT. To model the mixing delay, a varying number of air sub-streams are mixed with the fuel gas during different time periods. Alternatively, a combination of a perfectly mixed zone followed by a plug flow zone is illustrated. Results by any air-fuel mixing model show similar affect of process variables on NOx reduction. When a mixing delay is assumed instead of the instantaneous mixing the NOx reduction is enhanced, and only with delayed mixing NOx are affected by CH4. Lower temperature and higher pressure in the GT-combustor can enhance the NOx reduction. Also air staging is an effective option: a 3 stages combustor designed for low mixing speed appear competitive compared to more complicate combustors. The fewer hydrocarbons in the gasification gas the high NOx reduction.

STUDIES OF THERMAL SHOCK RESISTANCE OF AN ANTI-OXIDATION COATING FOR A MULTI-LAYERED CERAMIC COMPOSITE

2021 ◽  
pp. 51-58
Author(s):  
B.E. Goncharov ◽  
◽  
A.M. Sipatov ◽  
N.N. Cherkashneva ◽  
A.Yu. Pleskan ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Gas Flow ◽  
Ceramic Composite ◽  
Fuel Gas ◽  
Refractory Compounds ◽  
Turbojet Engine ◽  
Shock Resistance ◽  
Layered Ceramic ◽  
High Thermal Shock Resistance

The article covers the performance of thermal shock resistance experiments of a ceramic composite with two types of anti-oxidation coatings. A thermal shock burner rig was used to carry out the experiments similar to those expected in a combustor of a turbojet engine. SEM and х-ray diffraction analyses were used to examine the antioxidation coatings. It was deter-mined that the coating based on the refractory compounds possesses high thermal shock resistance when exposed to the fuel gas flow from a burner rig.

Simulation of Sugarcane Residues Co-Gasification (Vinasse-Straw-Bagasse) for Different Equivalence Ratios and Gasifying Agents

2021 ◽  
Vol 15 (1) ◽  
pp. 50-60
Author(s):  
Cláudia C. Santos ◽  
Janaine dos A. Oliveira ◽  
Igor de A. Barbieri ◽  
Filipe A. E Monhol
Keyword(s):  
Return On Investment ◽  
Energy Content ◽  
Operating Temperature ◽  
Energy Potential ◽  
Fuel Gas ◽  
Gasification Process ◽  
Thermoelectric Plant ◽  
Thermodynamic Equilibrium Model ◽  
Sugarcane Industry

This study evaluates the co-gasification of the main residues of the sugarcane industry (vinasse, bagasse and straw), in order to recover their energy and give an appropriate destination, making them suitable for use as fuel gas (syngas). To verify the feasibility of energy conversion through gasification, thermodynamic equilibrium model for gasification process was carried out and verified by literature available data. The gasification parameters for different gasification agents and equivalence ratio values were then obtained, such as: syngas composition and energy content, operating temperature, production rate and conversion efficiency. For equivalence ratios (ER) between 0.35 and 0.4 and temperatures around 750 °C, the quality of the syngas obtained is better, but a higher energy content is obtained in ER values of 0.2. There is a high H2/CO ratio for the gasifying agent formed by air and steam, and when using oxygen-enriched air, there is a change in the ER value that generates better syngas quality (to 0.3–0.35) and an increase in its energy content. There is also a possible better return on investment in a thermoelectric plant for the lowest ER values, which can increase gains by up to 21.4% and decrease the installation’s payback. The results indicate that the co-gasification of the waste is feasible, allowing a better use of its energy potential.

scholarly journals Analysis of the Effect of Anode Porosity on Temperature Distribution on Planar Radial Type SOFC

2018 ◽  
Vol 73 ◽  
pp. 01010
Author(s):  
Alif Widiyanto ◽  
Sulistyo ◽  
MSK Tony Suryo Utomo
Keyword(s):  
Temperature Distribution ◽  
Gas Flow ◽  
Hydrogen Gas ◽  
Cfd Modeling ◽  
Dynamics Modeling ◽  
Waste Products ◽  
Geometry Model ◽  
Electrolyte Surface ◽  
Fluent Software ◽  
Object Of Study

Solid Oxide Fuel Cell (SOFC) is an electrochemical equipment that converts gas into electricity directly. The waste products resulting from SOFC are water vapor and heat when using hydrogen gas. The electrode of the SOFC is the anode, electrolyte and cathode. The performance of SOFC is influenced porosity of the electrode. This study explained the relationship between porosity of the anode and temperature distribution using computational fluid dynamics modeling approach (CFD). In this study, CFD modeling was done by using Fluent software. The geometry model of computational modeling is a planar radial-type SOFC. The assumptions of some boundary conditions used from the study of literature and the object of study. The standard deviation and the different of temperature of the anode-electrolyte surface used to analyse the result. Non-homogenous temperature distribution rise if the anode porosity and gas flow rate is increasing. This indicates the gradient of temperature is bigger in the higher porosity, which may cause thermal stress and degrades the materials of electrode.

scholarly journals Numerical Analysis on Effect of Additional Gas Injection on Characteristics around Raceway in Melter Gasifier

2019 ◽  
Vol 38 (2019) ◽  
pp. 837-848
Author(s):  
Du Kaiping ◽  
Gao Xiangzhou ◽  
Sun Haibo
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Gas Injection ◽  
Coke Oven ◽  
Pure Oxygen ◽  
Small Scale ◽  
Gas Temperature ◽  
Fuel Gas ◽  
Hot Air ◽  
Flow Circulation

AbstractThe raceway plays an important role in the mass and heat transportation inside a melter gasifier. Considering that pure oxygen at room temperature instead of hot air is injected into the melter gasifier, a two-dimensional mathematical model at steady state is developed in the current work to describe the effect of the additional gas injection on the characteristics around the raceway in melter gasifier. The results show that a high-speed jet with a highest temperature above 3500 K could be found in front of tuyere. Furthermore, a small scale of gas flow circulation occurs in front of tuyere that results in a more serious thermal damage to tuyere. In order to decrease the gas temperature in the raceway to prevent the blowing-down caused by tuyere damage, the additional gas, including N2, natural gas (NG) and coke oven gas (COG) should be injected through the tuyere. Compared with N2, additional fuel gas injection gives full play to the high temperature reduction advantage of hydrogen. In addition, considering the insufficient hearth heat after injecting NG and the effective utilization of secondary resource, an appropriate amount of COG is recommended to be injected for optimizing blast system.

COAL SEAM DEGASIFICATION IN QUEENSLAND UTILISING HYDRAULIC FRACTURING WITH FOAM—A CASE HISTORY

1981 ◽  
Vol 21 (1) ◽  
pp. 137
Author(s):  
B. Wilkinson ◽  
L. Barro
Keyword(s):  
Gas Flow ◽  
Gas Production ◽  
Low Permeability ◽  
Gas Flow Rate ◽  
Coal Seams ◽  
Flow Rates ◽  
Coal Deposits ◽  
Early Production ◽  
Design Calculations ◽  
Gas Bearing

Vast reserves of gas-bearing coal deposits are located in Queensland. Owing to the extremely low permeability and porosity of the coal, very low gas flow rates are normally encountered. In an effort to enhance the gas production to economic quantities and to degasify the coal to provide a safer mining environment, four experimental wells were drilled into coal seams near Blackwater, Queensland.Based on extensive laboratory testing of coal samples, computerised fracture design calculations were performed to determine a suitable stimulation programme. The wells were hydraulically fractured with up to 15 000 US gal of foamed stimulation fluid containing 75 per cent nitrogen. To prop open the induced fracture system, 15 000 lb of sand was pumped with the foam. The maximum concentration was eight pounds of 20-40 mesh sand per gallon of fluid. Gas production from the unstimulated wells was too low to measure. Early production data soon after the fracturing suggested a gas flow rate of approximately 50 Mcf/D.

Effects of Various Reactions on the Gas Flow and Heat Transfer in an Anode Duct of ITSOFCs

2005 ◽  
Author(s):  
Jinliang Yuan ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Porous Electrode ◽  
Gas Permeation ◽  
Transport Processes ◽  
Operating Conditions ◽  
Electrochemical Reactions ◽  
Fuel Gas ◽  
Internal Reforming ◽  
Porous Anode

Recently, there has been considerable interest in the internal reforming reactions of solid oxide fuel cells (SOFCs) using methane or natural gas via. The internal reforming and electrochemical reactions appear in the porous anode layer, and may lead to inhomogeneous temperature and gas species distributions according to the reaction kinetics. A three-dimensional calculation method has been further developed to simulate and analyze the internal reforming and the electrochemical reactions, and the effects on various transport processes in a thick anode duct. In this study, the composite duct consists of a porous anode, fuel flow duct and solid current connector. Momentum, heat transport and gas species equations have been solved by coupled source terms and variable physical properties (density, viscosity, specific heat, etc.) of the fuel gas mixture. The combined thermal boundary conditions on solid walls, mass balances (generation and consumption) associated with the various reactions and gas permeation to/from the porous electrode are applied in the analysis. Simulation results show that the internal reforming and the electrochemical reactions, and operating conditions are significant for fuel gas transport and heat transfer in the anode.

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