High Temperature Air Combustion Technology Research Articles

Development of a waste incinerator based on high-temperature air combustion technology

Development of a waste incinerator based on high-temperature air combustion technology

Study of high-temperature oxygen combustion (HiTOx) and its heating performance using a laboratory-scale test furnace

Abstract High-temperature air combustion technology (HiCOT), which uses air preheated by heat recirculation, has had a great impact on reduction of CO2 and NOx emissions from combustion furnaces. In this study, a lab-scale test furnace was developed to examine the novel combustion method termed as high-temperature oxygen combustion, HiTOx. HiTOx uses combustion with a preheated mixture of oxygen and burned gas. Testing was conducted with liquefied petroleum gas. HiTOx has the following three characteristics because nitrogen is excluded from the working gas: (1) in principle, no thermal NOx is generated; (2) combustion gas is almost entirely water vapor and carbon dioxide, providing better heating performance because of its strong gas-phase radiation; and (3) the method has good compatibility with carbon dioxide capture, utilization and storage (CCUS) technologies because carbon dioxide can be separated easily from the combustion gas of HiTOx furnace by condensation of water vapor. Heating performance tests in a lab-scale test furnace were conducted using stainless steel rectangular rods as heating objects. Gas temperature, object temperature, and heat fluxes on the objects were measured. Compared to HiCOT, HiTOx enables stable operation with a lower flow rate of flue gas, better gas temperature uniformity in the furnace, faster heating, and higher heat flux. The heat flux of HiTOx was slightly higher than that of HiCOT (7%) when the furnace temperature was low (973 K) and the temperature difference between the gas and object was large (280 K). On the other hand, the heat flux of HiTOx was much higher than that of HiCOT (22%) when the furnace temperature was high (1323 K) and the temperature difference was small (60 K). Radiative heat transfer at high temperature was greater in HiTOx than in HiCOT at small temperature difference between the gas and object. A furnace body can be greatly downsized by the good radiation performance of combustion gas in HiTOx, resulting in a remarkable improvement in energy-saving performance.

High temperature air combustion (HiTAC): How it all started for applications in industrial furnaces and future prospects

Over the last three decades, High Temperature Air Combustion (HiTAC) has contributed much to become the leading technology for fossil fuel conversion in industrial furnaces. Since then several other researchers have termed it MILD, Flameless or Distributed combustion and they all show much similarities with the HiTAC. This review underlines that the technology was developed through a cooperation between the Japanese government (NEDO, METI) and Nippon Furnace Kogyo (Japan) as well as the key role played by the University of Maryland (USA) and the International Flame Research Foundation (IFRF – the Netherlands). Tokyo Gas (Japan) also provided an important role, although indirect, in the development. The HiTAC technology development was revolutionary with simultaneous demonstration on significant energy savings (some 25%), reduced equipment size, much reduced pollution (50%, including CO2), and noise in industrial furnaces. The technology is now widely used in many modern industrial furnaces worldwide. Per METI some 39,000 HiTAC burners in 7867 industrial furnaces were installed worldwide that showed fuel savings of 1721 billion liters of crude oil/year. It is estimated that 68 Billion liters/year of fuel oil savings and 180 Billion tons/year of CO2 reduction will be realized by 2030 through the use of HiTAC technology in industrial furnaces. This revolutionary technology continues to be adapted by many countries worldwide. The authors provide a brief review on the HiTAC technology development and give their views on its potential applications on the horizon that will also contribute to cleaner and efficient combustion in many other applications, besides industrial furnaces. These include high intensity gas turbine combustion, portable power, and engines. We do not discuss MILD and Flameless combustion as they have been reviewed previously with proliferation of numerous scientific publications available in the literature on the subject.

Prospect analysis of high temperature air combustion technology for low calorific value coalbed methane in Liupanshui area of Guizhou province

China’s coalbed methane resource is abundant, which ranks third in the world. The total amount of coalbed methane resources in Guizhou Province accounts for about 10% of China, which ranks second in the country. However, the utilization rate of coalbed methane in Guizhou Province is not only low, but also relatively single, especially the low calorific value coalbed methane extracted from underground mines which has a methane concentration of only 10-30%. And the main method to deal with low calorific value coalbed methane is discharging directly, which caused a huge waste of energy. High temperature air combustion technology (HTAC), which expands the utilization range of low calorific value fuels, has attracted wide attention due to its characteristics of extreme recovery of waste heat and ultra-low NOx emission. In this paper, the characteristics of high temperature air combustion of low calorific value coalbed methane are analyzed by theoretical and numerical calculation based on combustion theory and CFD method.

Experimental research on the application of HTAC in small-size heating furnace

High temperature air combustion (HTAC) technology, which is also known as regenerative combustion technology, has realized energy saving, CO2 and NOx emissions reduction and low-noise combustion. It has been widely applied in various types of heating furnace and has achieved good energy-saving effect. However, there is little application of this technology in small-size furnace. In this paper, a small-size regenerative heating furnace was built in the laboratory and experiments were carried out on it. The result shows that, if the transport frequency was set to a group per min, the center temperature of processed workpiece at the rated conditions (i.e. burner power is 300 kW and switching time is 60s) reached 1133°C. And the efficiency of the heating furnace was 36.8%. Then the derived comprehensive heat transfer coefficient was 168 W/(m2˙°C).

Numerical investigation towards HiTAC conditions in laboratory-scale ethanol spray combustion

In the past 25years high temperature air combustion (HiTAC) technology has been proved and utilized in industry as a promising way to increase thermal efficiency, create a relatively uniform temperature distribution, and reduce emissions of harmful pollutants such as NOX and CO. However, due to the complexity of fuel-oil combustion, to date HiTAC is mainly applied to gaseous fuel or coal, and little is known about spray combustion under HiTAC condition. In the present study, we numerically investigate the Delft Spray-in-Hot-Coflow (DSHC) using ethanol in high temperature diluted combustion air, and extend it to more co-flow conditions. We employ different temperatures and oxygen concentrations of the co-flow in order to dilute the oxidizer/fuel before it reacts with the fuel/ oxidizer. The pressure-swirl atomizer model with an Eulerian-Lagrangian approach was implemented for the spray modeling. Collision, coalescence, secondary breakup and evaporation of the drops were taken into account. The steady laminar flamelet model for the combustion of ethanol, the Discrete Ordinate model for radiation and the k-ε model for the turbulence with enhanced wall treatment were validated by the simulation of the NIST flame under conventional conditions and then used in the current study.The results indicate that the decreased peak temperature in many HiTAC applications with high temperature combustion air is mainly due to the reduced oxygen concentration by entraining flue gas.In the present study, a low oxygen concentration slows the evaporation process of droplets. It results in an enlarged combustion zone, a lowered peak temperature and minor NOX emission. However, decreasing the oxygen concentration may lead to problems of cracking, soot formation and flame extinction, especially for heavy oils. The optimization needs to be carried out based on the analysis of a specific fuel in order to create a HiTAC-like condition.Based on the results of the current study, the 1500K and 6%vol oxygen concentration case is considered as a HiTAC condition.

7-1-3 対向流型吹き込み方式を適用したストーカ式廃棄物焼却炉のNOx低減メカニズムに関する考察

7-1-3 対向流型吹き込み方式を適用したストーカ式廃棄物焼却炉のNOx低減メカニズムに関する考察

7-2-2 高温空気燃焼技術を適用したストーカ式焼却炉の性能向上(Session 7-2 環境対策)

7-2-2 高温空気燃焼技術を適用したストーカ式焼却炉の性能向上(Session 7-2 環境対策)

対向流燃焼を適用したストーカ式焼却炉の低NOx化に関する性能評価

JFE Engineering has developed the advanced stoker-type incineration system “JFE Hyper 21 Stoker System”, which adopts high temperature air combustion technology. With this technology, the incinerator realizes stable combustion in the condition of low excess air ratio, which results in reduction of NOx formation. In this paper, we describe a newly developed stoker-type incinerator which utilizes counter flow combustion in addition to high temperature air combustion technology. Verification experiment was conducted and further reduction of NOx formation was achieved. Experiment and numerical simulation were carried out to consider the reduction mechanism of NOx. Flat combustion region which contributes to stable combustion was observed in both experiment and simulation. Oxygen concentration distribution in the furnace implies that effective two-staged combustion is formed. From the view of fluid analysis, strong turbulence region is formed in the downstream of the furnace. These factors are considered to interact with each other and contribute to suppress the NOx formation.

Application and research on Regenerative High Temperature Air Combustion technology on low-rank coal pyrolysis

Abstract Regenerative High Temperature Air Combustion (RHTAC) technology is composed of circular-ceramic regenerator, burners, small four-way reversing valve and control system. RHTAC technology works by using the regenerator in burners to complete heat exchange between the high-temperature fume exhausted and the combustion air. Based on RHTAC technology, Regenerative Radiant Tube Combustor (RRTC) has been developed, and was adopted by Shenwu Pyrolysis Process (SPP), which is a new pyrolysis technology with the heat-carrier-free rotating bed. SPP was researched and developed to upgrade low-rank coal into the upgraded coal, tar and pyrolyzing gas. Presently, various coals from China and other countries have been conducted, including Lignite and Long flame coal. To understand the function of the RRTCs in SPP, a pilot plant has been constructed and used to investigate the effects of the RRTCs on the fume and pyrolyzer temperature distributions and pyrolyzing products. The results show that low calorific value gas fuel (>700 kcal/Nm3) can be used, the heat loss in fume exhausted is low (temp. about 150 °C), so thermal efficiency of the RRTC is greatly improved; the RRTCs can realize accurate temperature control and the separation of volatile materials and fume in the pyrolyzer, so as to increase tar yield and improve gas quality. The tar yield is more than 90% of the Gray-King tar yield; the pyrolyzing gas contains high contents of CH4, H2 and CO. Moreover, SPP could solve some technical problems, such as high dust content in coal tar, likely blockage of pipeline and greatly increasing the subsequent tar processing cost.

Application of Regenerative High Temperature Air Combustion Technology on Low-rank Coal Pyrolysis

Abstract Based on Regenerative High Temperature Air Combustion technology (RHTAC), a Regenerative Radiant Tube Combustor (RRTC) has been developed and adopted into Shenwu Pyrolysis Process (SPP). SPP is a new regenerative pyrolysis technology with heat-carrier-free rotating bed, which has been researched and developed to upgrade low-rank coal. To understand the RRTC function, a pilot plant has been constructed and used to investigate the effect of RRTC on the fume, reactor temperature distribution and pyrolysis products. The results show that low calorific value gas can be used as fuel, the heat loss in fume exhausted is low while thermal efficiency of the RRTC is greatly improved; the RRTC could realize accurate temperature control and the separation of volatile materials and fume in the reactor, so as to increase tar yield and improve gas quality. The tar yield is more improved; the gas contains high content of CH4 and H2. Moreover, heat-carrier-free rotating bed could solve some technical problems.

Efficient Energy Conversion of Wastes and Fuels in Power Systems

Efficient fossil energy use with low pollution in all kinds of power plants is of growing interest in all industrial sectors. The use of energy is growing steadily by many countries worldwide due to the greater desire for enhancing better standards of living and to increase productivity. Efficient energy use is favorable for better productivity product quality, costs, and quality of human life but the energy use adversely impacts our environment. During the past decade energy demands from China and India have grown significantly and is projected to grow even more in the coming decades as they enhance their living standards and productivity. This clearly requires close examination of the available methods of fossil fuel energy conversion as well as advanced methods that will provide increased efficiency and pollution reduction. This section, after brief review on historical perspectives on energy conversion, provides a short review on the various methods used for energy conversion in industrial power plants as well as new innovative methods that are now beginning to become available with significant fuel saving, compact size of the equipment and low pollution. As an example, high temperature air combustion technology has seen wider acceptance of the technology in many kinds of industrial furnaces, in particular, for use in steel industry and fuel reforming furnaces with demonstrated energy savings of about 30% (on the average), about 25% reduction in the size of the equipment (compact size), about 50% reduction in low pollution and better quality of the product produced. Such significant energy savings were only dream of engineers in the past. This technology has been adapted by many countries worldwide. In addition advanced technologies are developed or being developed for use with coals (and solid fuels) since its cost based on energy content is low as compared to gaseous fuels, such as natural gas. Several commonly used methods in power generation are presented along with integrated and hybrid systems for increased efficiency. Clear representation is provided of the output energy available from known input energy. Some energy conversion techniques provide in-situ capture of pollutants while others must use air pollution control devices for pollution capture and/or pollution reduction prior to waste gases discharge to the atmosphere. The information provides quick guide on the commonly used methods of energy conversion in the USA and Europe, in particular when using solid fuels, such as coal. It is expected that future systems will be more energy efficient and emit even lower pollution via the use of combined cycle systems and integrated energy conversion systems. Advanced high temperature steam gasification results in hydrogen-rich syngas of higher heating value, reduced volume of the waste, and the remaining residue is clean and non-leachable.

Study on High Temperature Air Combustion of Hot Blast Stove

NOx is the major technical barrier to increase hot blast temperature and prolong campaign life of hot blast stove (HBS) at present. In order to restrain the amount of NOx formation during combustion process in the HBS, the paper studies and analyses the generation mechanism of NOx production, and calculates NOx generation rate and amount in HBS by means of thermodynamic generation model. A new dome combustion stove is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of CFD numerical simulation model. Temperature and concentration field distribution, flame shape and NOx concentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature field distribution. Under the same dome temperature, NOx generation is 80ppm only, reduced by approximate 76% in comparison with conventional stove. HTAC HBS can obtain higher temperature, energy-saving, emission-reducing, and decrease NOx emission efficiently, as well as realize long campaign life of HBS.

206 高温空気燃焼技術を適用したストーカ式焼却炉の性能向上(焼却・溶融技術)

To improve the performance of "JFE Hyper 21 Stoker System", an advanced stoker-type incinerator, we have modified High-temperature Air Combustion Technology (HiCOT). In this paper, the effect and characteristics of modified HiCOT are examined. In verification tests, stable combustion with lower NOx emission is demonstrated at air excess rate 1.3. In a numerical simulation, calculated internal temperature distribution of the incinerator is agreed with measured that in verification tests qualitatively. In case of applying modified HiCOT to actual waste incinerator, increase of power generation is expected by increase of steam flow for turbine which is due to eliminating a catalytic denitrification equipment.

Study and Design on High Temperature Air Combustion of Hot Blast Stove

During Hot Blast Stove (HBS) combustion, NOxforms rapidly when the flame temperature above 1420°C. In order to restrain the amount of NOxformation during combustion of HBS, the formation mechanism of NOxis investigated, and the NOxformation rate and amount in HBS are calculated by means of thermodynamic model. A new type of dome combustion HBS is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of Computational Fluid Dynamics (CFD) simulation model. Temperature and concentration distribution, flame shape and NOxconcentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature distribution. Under the same dome temperature, NOxamount is 80ppm only, reduced by approximate 76% in comparison with conventional stove.

I133 高温酸素燃焼条件における同軸噴流火炎の火炎構造に関する研究

OH-PLIF measurements and numerical simulations were conducted for co-axial laminar jet flame of CH_4/N_2 in high-temperature air (relevant to High-Temperature Air Combustion Technology: HiCOT) flow and that of CH_4/CO_2 in high-temperature O_2/CO_2 (High-Temperature Oxygen Combustion: HiTOx) flow. In both HiCOT and HiTOx conditions, two types of lifted flames were observed: one (Lifted Flame A) showed strong OH signal near the flame base at high CH_4 mole fraction of the fuel stream (X_<CH4>) and another (Lifted flame B) showed strong OH signal near the flame tip at low X_<CH4>. The present computations successfully reproduced these two types of lifted flames. In the computations, Lifted Flame A was formed near stoichiometric line while Lifted Flame B was formed in the far downstream region of stoichiometric line. Based on the classification using the flame temperature, Lifted Flame A was classified to a tnbranchial lifted flame and Lifted Flame B was classified to mild combustion.

Current State of Gas Resource Utilization and Countermeasures of Energy Saving for Integrated Iron and Steel Works in China

Gas is an important secondary energy in integrated iron and steel works. In this paper we proposed the reasons for low gas utilization by analyzing the characteristics and recycling situation of gas resource. One is the relatively backward idea, the other is that the ways and means of optimizing gas utilization are also backward, then we come up with the countermeasures to improve gas resource utilization. First of all we should promote energy conservation of enterprise system, optimize comprehensive utilization of gas and improve the energy structure. Second is putting more investment in new technology development and take active use of new technology and new process, such as high temperature air combustion technology, combined cycle power plant technology, enriched technology of blast furnace gas and so on. Last is developing gas deep processing to promote co-products of steel and chemical industry. The high added-value chemical products can be obtained by technologies such as production of hydrogen and methyl alcohol with coke oven gas, synthesis of methanol and dimethyl ether with converter gas and so on.

High Temperature Air Combustion Energy-Saving Technologies and Environmental Characteristics Analysis

High temperature air combustion technology is a new advanced combustion technology, which is energy efficient and has the dual advantages of low pollution emissions and energy conservation. This sustainable development is in line with China’s strategic objectives of energy saving. Based on the high temperature air combustion technology and environmental characteristics, the paper analyzed its heat transfer process and determined the proper commutation cycle based on the numerical model. It is indicated that combustion technology can increase the temperature of air flowing into the furnace, reduce the temperature of the flue gas emissions, and improve thermal and temperature efficiency and thus to save the fuel. It can also suppress the formation of NOx, reducing CO2 emissions and is a good environmentally friendly energy technology in industrial furnace.

Development of high intensity CDC combustor for gas turbine engines

Colorless distributed combustion (CDC) has been demonstrated to provide ultra-low emission of NO x and CO, improved pattern factor and reduced combustion noise in high intensity gas turbine combustors. The key feature to achieve CDC is the controlled flow distribution, reduce ignition delay, and high speed injection of air and fuel jets and their controlled mixing to promote distributed reaction zone in the entire combustion volume without any flame stabilizer. Large gas recirculation and high turbulent mixing rates are desirable to achieve distributed reactions thus avoiding hot spot zones in the flame. The high temperature air combustion (HiTAC) technology has been successfully demonstrated in industrial furnaces which inherently possess low heat release intensity. However, gas turbine combustors operate at high heat release intensity and this result in many challenges for combustor design, which include lower residence time, high flow velocity and difficulty to contain the flame within a given volume. The focus here is on colorless distributed combustion for stationary gas turbine applications. In the first part of investigation effect of fuel injection diameter and air injection diameter is investigated in detail to elucidate the effect fuel/air mixing and gas recirculation on characteristics of CDC at relatively lower heat release intensity of 5 MW/m 3 atm. Based on favorable conditions at lower heat release intensity the effect of confinement size (reduction in combustor volume at same heat load) is investigated to examine heat release intensity up to 40 MW/m 3 atm. Three confinement sizes with same length and different diameters resulting in heat release intensity of 20 MW/m 3 atm, 30 MW/m 3 atm and 40 MW/m 3 atm have been investigated. Both non-premixed and premixed modes were examined for the range of heat release intensities. The heat load for the combustor was 25 kW with methane fuel. The air and fuel injection temperature was at normal 300 K. The combustor was operated at 1 atm pressure. The results were evaluated for flow field, fuel/air mixing and gas recirculation from numerical simulations and global flame images, and emissions of NO, CO from experiments. It was observed that the larger air injection diameter resulted in significantly higher levels of NO and CO whereas increase in fuel injection diameter had minimal effect on the NO and resulted in small increase of CO emissions. Increase in heat release intensity had minimal effect on NO emissions, however it resulted in significantly higher CO emissions. The premixed combustion mode resulted in ultra-low NO levels (<1 ppm) and NO emission as low as 5 ppm was obtained with the non-premixed flame mode.

Effect of buoyancy on soot formation in gas-jet diffusion flame

In order to investigate the effect of buoyancy on soot formation in gas-jet diffusion flame, we conducted one set of experiments with the High-Temperature Air Combustion Technology (HiCOT) system and another set under partial gravity conditions. Ethylene (C2H4) was used as fuel, and soot volume fractions for the flame were observed as shadow graph images with backlight. In the experiment with the HiCOT, the oxygen concentrations were O2 = 15 %, 17 %, and 23 %, with constant flame temperature and surrounding air temperatures of 1100 K, 900 K, and 300 K, respectively. We found that the soot volume fraction in the flames increased with the increase of the oxidizer temperature. In the partial gravity experiment meant to identify the buoyant effect, the results showed that the soot volume fraction depended on the gravity level. These results imply that soot formation in a gas-jet diffusion flame with the HiCOT is strongly affected by the buoyant flow due to oxidizer flow into the soot formation field.