Mild Combustion in a Novel CCGT Cycle With Partial Flue Gas Recirculation

2003 ◽  
Author(s):  
S. M. Camporeale ◽  
F. Casalini ◽  
A. Saponaro
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Soot Formation ◽  
Combustion Process ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Heavy Fuel Oil ◽  
Mild Combustion ◽  
Turbine Exhaust

A novel Combined Cycle Gas Turbine layout is proposed for using heavy fuel oil in a combustion mode called “Mild Combustion”, characterized by a very low adiabatic flame temperature and flat temperature field in the combustion chamber and low pollutant emissions. “Mild Combustion” is obtained by means of the dilution of reactants with inert gas like combustion product resulting in a very low oxygen concentration of the mixture at the ignition. To stabilize the combustion process in such a condition the reactants temperature has to be raised above the self ignition value. In industrial application this particular preconditioning of the reactants can be reached partially before the combustion chamber and finally in process by means of a performed aerodynamic that further dilute and heat-up the mixture. An experimental analysis of the oil combustion behaviour inside the gas turbine exhaust flow has been arranged at Centro Combustione of Ansaldo Caldaie in Gioia del Colle (Italy). The turbine exhaust gases are simulated by mixing those produced in a gas burner with external air preheated at different temperatures in order to have different final oxygen concentrations and temperature levels. The influence of the main combustion parameters regarding the process feasibility and environmental impact are presented and analysed. Good results in terms of NOx emissions and soot formation have been obtained for heavy oil combustion in a 10% oxygen oxidizer concentration requiring a combustion chamber inlet temperature of about 900K. In order to meet these conditions, a novel CCGT cycle in which about 64% of combustion products are re-circulated before entering the combustion chamber, is proposed. The thermodynamic analysis shows that the efficiency that could be achieved by the proposed cycle is a few percent lower than the efficiency of a combined cycle power plant fuelling natural gas, with the same turbine inlet temperature and similar turbine blade cooling technology.

A Study on Low NOx Combustion in LBG-Fueled 1500°C-Class Gas Turbine

1994 ◽  
Author(s):  
Toshihiko Nakata ◽  
Mikio Sato ◽  
Toru Ninomiya ◽  
Takeharu Hasegawa
Keyword(s):  
Power Generation ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Coal Gasification ◽  
Combustion Process ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Secondary Air

Developing integrated coal gasification combined cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in an Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of air-blown entrained-flow type has calorific value as low as 1/10 of natural gas. Furthermore the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emission that is produced from the ammonia in the fuel. The main fuel and the combustion air is supplied into fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen. By testing it under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.

A Study on Low NOx Combustion in LBG-Fueled 1500°C-Class Gas Turbine

1996 ◽  
Vol 118 (3) ◽  
pp. 534-540 ◽  
Author(s):  
T. Nakata ◽  
M. Sato ◽  
T. Ninomiya ◽  
T. Hasegawa
Keyword(s):  
Power Generation ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Coal Gasification ◽  
Combustion Process ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Gas Temperature

Developing integrated coal gasification combined-cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of an air-blown entrained-flow type has a calorific value as low as 1/10 of natural gas. Furthermore, the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emissions from the ammonia in the fuel. The main fuel and the combustion air are supplied into a fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen. By testing under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.

Combustion Performance in a Semiclosed Cycle Gas Turbine for IGCC Fired With CO-Rich Syngas and Oxy-Recirculated Exhaust Streams

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Takeharu Hasegawa
Keyword(s):  
Gas Turbine ◽  
Coal Gasification ◽  
Combustion Process ◽  
Equilibrium Concentration ◽  
Combined Cycle ◽  
Reaction Heat ◽  
Highly Efficient ◽  
Coal Fuel ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Our study found that burning a CO-rich gasified coal fuel, derived from an oxygen–CO2 blown gasifier, with oxygen under stoichiometric conditions in a closed cycle gas turbine produced a highly-efficient, oxy-fuel integrated coal gasification combined cycle (IGCC) power generation system with CO2 capture. We diluted stoichiometric combustion with recycled gas turbine exhaust and adjusted for given temperatures. Some of the exhaust was used to feed coal into the gasifier. In doing so, we found it necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, we examined the emission characteristics of gasified-fueled stoichiometric combustion with oxygen through numerical analysis based on reaction kinetics. Furthermore, we investigated the reaction characteristics of reactant gases of CO, H2, and O2 remaining in the recirculating gas turbine exhaust using present numerical procedures. As a result, we were able to clarify that since fuel oxidation reaction is inhibited due to reasons of exhaust recirculation and lower oxygen partial pressure, CO oxidization is very sluggish and combustion reaction does not reach equilibrium at the combustor exit. In the case of a combustor exhaust temperature of 1573 K (1300 °C), we estimated that high CO exhaust emissions of about a few percent, in tens of milliseconds, corresponded to the combustion gas residence time in the gas turbine combustor. Combustion efficiency was estimated to reach only about 76%, which was a lower value compared to H2/O2-fired combustion while residual O2 in exhaust was 2.5 vol%, or five times as much as the equilibrium concentration. On the other hand, unburned constituents in an expansion turbine exhaust were slowed to oxidize in a heat recovery steam generator (HRSG) flue processing, and exhaust gases reached equilibrium conditions. In this regard, however, reaction heat in HRSG could not devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly efficient, oxy-fuel IGCC.

CCPP Operational Flexibility Extension Below 30% Load Using Reheat Burner Switch-Off Concept

2015 ◽  
Author(s):  
Dirk Therkorn ◽  
Martin Gassner ◽  
Vincent Lonneux ◽  
Mengbin Zhang ◽  
Stefano Bernero
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Fast Response ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Operational Flexibility ◽  
Part Load ◽  
Combustion Technology ◽  
The Impact

Highly competitive and volatile energy markets are currently observed, as resulting from the increased use of intermittent renewable sources. Gas turbine combined cycle power plants (CCPP) owners therefore require reliable, flexible capacity with fast response time to the grid, while being compliant with environmental limitations. In response to these requirements, a new operation concept was developed to extend the operational flexibility by reducing the achievable Minimum Environmental Load (MEL), usually limited by increasing pollutant emissions. The developed concept exploits the unique feature of the GT24/26 sequential combustion architecture, where low part load operation is only limited by CO emissions produced by the reheat (SEV) burners. A significant reduction of CO below the legal limits in the Low Part Load (LPL) range is thereby achieved by individually switching the SEV burners with a new operation concept that allows to reduce load without needing to significantly reduce both local hot gas temperatures and CCPP efficiency. Comprehensive assessments of the impact on operation, emissions and lifetime were performed and accompanied by extensive testing with additional validation instrumentation. This has confirmed moderate temperature spreads in the downstream components, which is a benefit of sequential combustion technology due to the high inlet temperature into the SEV combustor. The following commercial implementation in the field has proven a reduction of MEL down to 26% plant load, corresponding to 18% gas turbine load. The extended operation range is emission compliant and provides frequency response capability at high plant efficiency. The experience accumulated over more than one year of successful commercial operation confirms the potential and reliability of the concept, which the customers are exploiting by regularly operating in the LPL range.

Chemical Looping Combustion Using the Direct Combustion of Liquid Metal in a Gas Turbine Based Cycle

2010 ◽  
Author(s):  
Niall R. McGlashan ◽  
Peter R. N. Childs ◽  
Andrew L. Heyes
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Combined Cycle ◽  
Air Separation ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Sensible Heat ◽  
Separation Unit

A combined cycle gas turbine generating power and hydrogen is proposed and evaluated. The cycle embodies chemical looping combustion (CLC) and uses a Na based oxygen carrier. In operation, a stoichiometric excess of liquid Na is injected directly into the combustion chamber of a gas turbine cycle, where it is burnt in compressed O2 produced in an external air separation unit (ASU). The resulting combustion chamber exit stream consists of hot Na vapour, and this is expanded in a turbine. Liquid Na2O oxide is also generated in the combustion process, but this can be separated, readily, from the Na vapour and collects in a pool at the bottom of the reactor. To regenerate liquid Na from Na2O, and hence complete the chemical loop, a reduction reactor (the reducer) is fed with three streams: the hot Na2O from the oxidiser; the Na vapour (plus some entrained wetness) exiting a Na-turbine; and a stream of solid fuel, which is assumed to be pure carbon for simplicity. The sensible heat content of the liquid Na2O and latent and sensible heat of the Na vapour provide the heat necessary to drive the endothermic reduction reaction and ensure the reducer is externally adiabatic. The exit gas from the reducer consists of almost pure CO which can be used to generate by-product H2 using the water-gas shift reaction. A mass and energy balance of the system is conducted assuming reactions reach equilibrium. The analysis allows for losses associated with turbomachinery; heat exchangers are assumed to operate with a finite approach temperature; however, pressure losses in equipment and pipework are assumed negligible — a reasonable assumption for this type of analysis that will still yield meaningful data. The analysis confirms that the combustion chamber exit temperature is limited by both first and second law considerations to a value suitable for a practical gas turbine. The analysis also shows that the overall efficiency of the cycle, under optimum conditions and taking into account the work necessary to drive the ASU, can exceed 75%.

Performance Simulation of a Combined Cycle Power Generation System With Steam Injection in the Gas Turbine Combustion Chamber

2007 ◽  
Author(s):  
B. Law ◽  
B. V. Reddy
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Pressure Ratio ◽  
Steam Injection ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Work Output ◽  
Gas Turbine Combustion

In the present work the effect of steam injection in the gas turbine combustion chamber is investigated on gas turbine and steam turbine work output and on thermal efficiency of the combined cycle power plant. The operating conditions investigated include gas turbine pressure ratio and gas turbine inlet temperature. The steam injection decreases the steam cycle output and boosts the gas cycle output and the net combined cycle work output and thermal efficiency significantly.

scholarly journals Experimental Evaluation of a Two-Stage Slagging Combustor Design for a Coal-Fueled Industrial Gas Turbine

1992 ◽  
Author(s):  
L. H. Cowell ◽  
R. T. LeCren
Keyword(s):  
Gas Turbine ◽  
Combustion Zone ◽  
Combustion Process ◽  
Coal Ash ◽  
Pollutant Emissions ◽  
Test Facility ◽  
Inlet Temperature ◽  
Water Mixture ◽  
Test Results ◽  
Industrial Gas Turbine

A full-size combustor for a coal-fueled industrial gas turbine engine has been tested to evaluate combustion performance prior to integration with an industrial gas turbine. The design is based on extensive work completed through one-tenth scale combustion tests. Testing of the combustion hardware is completed with a high pressure air supply in a combustion test facility at the Caterpillar Technical Center. The combustor is a two-staged, rich-lean design. Fuel and air are introduced in the primary combustion zone where the combustion process is initiated. The primary zone operates in a slagging mode inertially removing coal ash from the gas stream. Four injectors designed for coal-water mixture (CWM) atomization are used to introduce the fuel and primary air. In the secondary combustion zone additional air is injected to complete the combustion process at fuel-lean conditions. The secondary zone also serves to reduce the gas temperatures exiting the combustor. The combustor has operated at test pressures of 7 bars with 600K inlet temperature. Tests have been completed to set the air flow split and to map the performance of the combustor as characterized by pollutant emissions, coal ash separation, and temperature profile. Test results with a comparison to subscale test results are discussed. The test results have indicated that the combustor operates at combustion efficiencies above 98% and with pollutant emissions below design goals.

A Program for the Evaluation of Pollutant Emissions in Combined Cycle Power Plants With Supplementary Firing

2002 ◽  
Author(s):  
R. Bettocchi ◽  
M. Pinelli ◽  
P. R. Spina
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Power Plants ◽  
Combustion Process ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Emission Model ◽  
Combined Cycle Power Plant ◽  
Gas Turbine Combustors ◽  
Numerical Predictions

In this paper, a one-dimensional program for evaluating pollutant emissions in combined cycle power plant with supplementary firing is presented. The program uses Chemical Reactors analysis based on a Perfectly Stirred Reactor approach in conjunction with an emission model that simulates a detailed chemical kinetic scheme for combustion process modelling. The program allows the evaluation of the main pollutant emissions deriving from natural gas and oil combustion. In order to simulate combustion systems that can be found in a fired combined cycle power plant, the developed program presents some extended features with respect to programs developed for gas turbine combustors only. In order to reproduce a wide typology of combustors, the combustor geometry is represented using two characteristic dimensions (hydraulic diameter and length) and the considered domain is divided into reactors in series (along the axial direction) and in parallel (along the radial direction). The temperature in each reactor is determined taking into account both the convective and the radiative heat transfer between hot gases and walls. The program has been applied to two cases. In the first the numerical predictions have been compared with available experimental data relative to two gas turbine combustors. In the second case the program has been instead applied to a cylindrical test burner designed in accordance with EN 267 European Standard. The obtained results are acceptable from an engineering point of view and have been considered sufficiently accurate for this preliminary set-up phase of the model.

Numerical Simulation of Pollutant Emissions in a Can-Type Low NOx Gas Turbine Combustor

2010 ◽  
Author(s):  
Di Wang ◽  
Wenjun Kong ◽  
Yuhua Ai ◽  
Baorui Wang
Keyword(s):  
Gas Turbine ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Gas Turbine Combustor ◽  
In Series

A research program is in development in China in order to realize a demonstrator of combined cooling heating and power system (CCHP) with net electrical output around 100kW by using of a can-type micro gas turbine. In this paper, numerical simulations were completed to investigate the pollutant emissions in a can-type low NOx gas turbine combustor. Based on the analysis of the computational fluid dynamics (CFD) results, a Chemical Reactor Network (CRN) model was set up to simulate the pollutant emissions in the combustor with detailed gas-phase chemical kinetic mechanism of GRI-Mech 3.0. The CRN consists of a number of ideal reactors of the perfectly stirred reactors (PSR) and plug flow reactors (PFR) in series and parallel structures. Two types of CRN models were designed. One is relatively simple, another is more complex. The results show that the complex CRN model corresponds with the actual combustion process better. The trends of nitrogen oxides (NOx) and carbon monoxide (CO) varying with the equivalence ratio were conducted. Effects of the inlet temperature and pressure on NOx and CO emissions were also presented in this paper. At last, the numerical results are compared with the experimental results.

Semi-Closed CCGT Cycle With High Temperature Reactants Combustion

Volume 1 ◽  
2004 ◽  
Author(s):  
S. M. Camporeale ◽  
F. Casalini ◽  
A. Saponaro
Keyword(s):  
High Temperature ◽  
Large Range ◽  
Soot Formation ◽  
Fuel Oil ◽  
Stable Operation ◽  
Inlet Temperature ◽  
Stable Form ◽  
Nox Emissions ◽  
Heavy Fuel Oil ◽  
Mild Combustion

In the last years many research studies have been focused on the features of MILD combustion that is a stable form of combustion, obtained with high temperature reactants and high exhaust gas recirculation and characterized by low flame temperature and, consequently, low Nox emissions. This form of combustion is also characterized by low light emissions (for this reason it is also called “flameless” combustion) and a large range of stable operation. MILD combustion has been already applied in industrial furnaces where ceramic regenerators provide to raise the temperature of the entering diluted air, the main advantages being high efficiency and low emissions. The introduction of MILD combustion in power plants would allow for increasing the temperature of the entering reactants beyond the self-ignition temperature without increasing the NOx emission. The main goals of this technique are low combustion exergy losses, large range of stable combustion, and low NOx emissions. Some experiments have shown that the flameless conditions can be obtained using diluted reactants, even using heavy fuel oil. Good results in terms of NOx emissions and soot formation have been obtained for heavy oil combustion in a 10% oxygen concentration of reactants and combustion chamber inlet temperature of about 900K. In order to meet these conditions, a semiclosed CCGT cycle with high recirculation ratio, suitable for the use of heavy fuel oil, is proposed here, assuming state-of-the-art technologies for gas turbine and steam plant and steam cooling of the turbine blades. The thermodynamic analysis shows that the overall plant efficiency of the new scheme is close to 60% that is about the efficiency that can be obtained in modern CCGT power plant fuelling natural gas.

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