Catalytic Combustion Technology Research Articles

A new home energy-saving gas stove based on multi-jet cutting technology

As one of the indispensable living equipment in Chinese family, the energy conversion efficiency of gas stove has been widely concerned. The purpose of this paper is to apply the principle of multi-jet cutting circle and catalytic combustion technology to transform the gas stove, combine with dune-shaped profile combustion technology, improving the combustion efficiency of the gas stove, reducing the proportion of polluted gas in the exhaust gas and the exhaust gas pollution of the gas stove, so as to achieve the purpose of full premix, low emission, high efficiency combustion of the gas stove.

RETRACTED: Catalytic Combustion Characteristics of Methane-Air Mixtures in Small-Scale Systems at Elevated Temperatures

The catalytic combustion characteristics of methane-air mixtures in small-scale systems were investigated at elevated temperatures, with particular emphasis on identifying the main factors that affect formation and removal of combustion-generated pollutants. Computational fluid dynamics simulations were performed using detailed chemical kinetic mechanisms, and more insights were offered into the phenomena occurring in the temperature range where homogeneous and heterogeneous reaction pathways are both important. Reaction engineering analysis was performed to provide an in-depth understanding of how to achieve low emissions of pollutants. Spatial distributions of the major species involved were presented to gain insight into the interplay between the two competing pathways involved. The results indicated that the distribution of oxidized products depends critically on the feed composition, dimension, temperature, and pressure. Small-scale catalytic systems enable low emissions of pollutants even in a high temperature environment, along with high combustion efficiency. The interplay between the two competing pathways via radicals is strong, and the heterogeneous pathway can significantly inhibit the homogeneous pathway. The inhibiting effect also accounts for the low emissions of nitrogen oxides. Almost all of the nitrogen oxides emitted by small-scale catalytic systems are nitric oxide. Catalytic combustion technology can be used to reduce the formation of undesired products, especially pollutant nitrogen oxide gases far below what can be achieved without catalysts. Recommendations for the design of small-scale catalytic systems are provided.

Catalytic Oxidation of Chlorobenzene over MnxCe1-xO2/HZSM-5 Catalysts: A Study with Practical Implications.

Industrial-use catalysts usually encounter severe deactivation after long-term operation for catalytic oxidation of chlorinate volatile organic compounds (CVOCs), which becomes a "bottleneck" for large-scale application of catalytic combustion technology. In this work, typical acidic solid-supported catalysts of MnxCe1-xO2/HZSM-5 were investigated for the catalytic oxidation of chlorobenzene (CB). The activation energy (Ea), Brønsted and Lewis acidities, CB adsorption and activation behaviors, long-term stabilities, and surficial accumulation compounds (after aging) were studied using a range of analytical techniques, including XPS, H2-TPR, pyridine-IR, DRIFT, and O2-TP-Ms. Experimental results revealed that the Brønsted/Lewis (B/L) ratio of MnxCe1-xO2/HZSM-5 catalysts could be adjusted by ion exchange of H• (in HZSM-5) with Mnn+ (where the exchange with Ce4+ did not distinctly affect the acidity); the long-term aged catalysts could accumulate ca. 14 organic compounds at surface, including highly toxic tetrachloromethane, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, etc.; high humid operational environment could ensure a stable performance for MnxCe1-xO2/HZSM-5 catalysts; this was due to the effective removal of Cl• and coke accumulations by H2O washing, and the distinct increase of Lewis acidity by the interaction of H2O with HZSM-5. This work gives an in-depth view into the CB oxidation over acidic solid-supported catalysts and could provide practical guidelines for the rational design of reliable catalysts for industrial applications.

Development of Combustion Technology for Methane Emitted from Coal‐Mine Ventilation Air Systems

AbstractFugitive gas emissions from coal mining are widely known to be significant contributors to the emission of alkanes, mainly methane, to the environment. Utilization of coal‐mine ventilation air methane (VAM) is a crucial mission to minimize methane emission in the atmosphere. This paper reviews current technology for mitigation and utilization of methane emissions from coal mining. Challenges and opportunities for each technology are discussed together with their benefits/disadvantages. Catalytic combustion technology is recommended as the best option due to the low and variable concentration of methane in coal‐mine ventilation air, as well as its high volumetric flow. Herein, current developments in flameless combustion are discussed in detail with a few highlights on palladium‐based catalyst development. The remaining uncertainties and obstacles in the development of palladium‐based catalysts for VAM are also discussed. This paper highlights a few important practical aspects that necessitate further detailed investigation, such as catalyst deactivation phenomena, the stability of the catalyst under humid conditions, and the effect of coal dust on catalytic activity and stability. Notably, a pressure decrease, heat recovery/self‐sustaining, and long‐term deactivation are key for the successful development of VAM catalytic combustors.

Development of a novel cooking stove based on catalytic hydrogen combustion

A hydrogen based cooking stove was developed and tested in respect to efficiency, functionality and hydrogen safety. Therefore the developed novel combustion unit technology is based on the catalytic oxidation of hydrogen on a platinum coated highly porous reticulated silicon carbide foam ceramics. Compared to other works [1], premixing of hydrogen and air is avoided, thus providing the basis for safe and reliable operation. With this catalytic combustion technology, no initial hydrogen ignition is required, implying a high application security. Separate air and hydrogen supplies make regulation of temperature and power efficient, simple and save.Catalytic hydrogen oxidation is performed already at room temperature; whereby at high hydrogen load, a small hydrogen slip is detected under cold start conditions, nevertheless in operation this becomes negligible. In order to overcome this issue, a hydrogen flow regulation, based on the hydrogen combustion temperature, was introduced.A heat exchanger is integrated into the exhaust line, in order to recover heat for the incoming air, required for the catalytic combustion. This leads to a stove efficiency of up to 80%, measured according to the DIN EN 30-2-1: 2005–08 test standard and greatly exceeds the postulated standard minimum efficiency of 35%. For comfortable and save use, the combustion unit is mounted under a glass ceramic coverage, as common for conventional electrical stoves.

100° Temperature Reduction of Wet Methane Combustion: Highly Active Pd–Ni/Al2O3 Catalyst versus Pd/NiAl2O4

The crucial role of Ni mode addition to Pd catalysts for low-temperature wet methane combustion is addressed, resulting in excellent performance of ultralow-Ni-containing catalysts versus inactive nickel–alumina spinel. Traditional impregnation–calcination and colloidal techniques of bimetallic catalyst preparation yield monometallic Pd particles on a binary NiAl2O4 support and Pd and Ni nanoparticles on the parent Al2O3 support, respectively. The catalyst is potentially valuable for natural gas catalytic combustion technologies because it decreases the required temperature for complete methane combustion in 5% water presence in the feed by 100 degrees versus monometallic Pd.

Calorimetric thermoelectric gas sensor for the detection of hydrogen, methane and mixed gases.

A novel miniaturized calorimeter-type sensor device with a dual-catalyst structure was fabricated by integrating different catalysts on the hot (Pd/θ-Al2O3) and cold (Pt/α-Al2O3) ends of the device. The device comprises a calorimeter with a thermoelectric gas sensor (calorimetric-TGS), combining catalytic combustion and thermoelectric technologies. Its response for a model fuel gas of hydrogen and methane was investigated with various combustor catalyst compositions. The calorimetric-TGS devices detected H2, CH4, and a mixture of the two with concentrations ranging between 200 and 2000 ppm at temperatures of 100–400 °C, in terms of the calorie content of the gases. It was necessary to reduce the much higher response voltage of the TGS to H2 compared to CH4. We enhanced the H2 combustion on the cold side so that the temperature differences and response voltages to H2 were reduced. The device response to H2 combustion was reduced by 50% by controlling the Pt concentration in the Pt/α-Al2O3 catalyst on the cold side to 3 wt%.

Hybrid Catalytic Combustion of Methane/Hydrogen Mixtures

Hybrid catalytic combustion technology, which is a staged process comprising a preliminary catalytic partial oxidation (CPO) step followed by a homogeneous flame combustion with interstage heat removal, was tested for the first time with mixtures of methane and hydrogen. Short contact time CPO experiments were run to elucidate the effect of the progressive substitution of methane with H2 in the fuel feed to the structured catalytic reactor, which was operated under self-sustained conditions at high temperature. Furthermore, a prototype radiant hybrid burner was realized and safely operated at atmospheric pressure with up to 80% vol. of H2 in the fuel and a primary equivalence ratio in the range 2.4–4.0. Outstanding NOx emission levels were attained with pure methane feed, which were also confirmed with H2-rich fuels, due to the effective reduction of both thermal and prompt NOx formation.

The Structures and Preparation Methods of Perovskite-Type Oxide Catalysts for Natural Gas Catalytic Combustion

Catalytic combustion technology can effectively reduce the temperature of the combustion reaction and significantly inhibit the formation of NOx. Perovskites catalyst materials have high stability, varied chemical composition, and low cost etc. A combination of catalytic combustion technology and perovskite catalyst materials has great significance for energy industry and environment protection. However, improving lower temperature catalytic activity and high temperature thermostability performance of perovskite catalyst is still major problem. Some researchers have improved the activity and stability of perovskite catalysts for methane combustion by different preparation methods. The structure and preparation methods of perovskite-type oxide catalysts are presented.

Catalytic combustion of methane on BaZr(1−x)MexO3 perovskites synthesised by a modified citrate method

The catalytic combustion technology still lacks of catalytic systems stable at high temperatures, such as those of the gas turbine inlet in the last turbine generation. In this paper we tried to solve this problem by fitting transition metals inside a crystal structure which is known to be very stable.Several oxides have been synthesised by a modified citrate method and investigated in the catalytic combustion of methane. Synthesised catalysts consist of a solid solutions with a perovskite structure of formula BaZr(1−x)MexO3, where Me=Rh, Pd, Mn, Ni, Ru, Pt, Co.The goal of the work has been to provide the physicochemical, structural and morphological characterisation and the activity of these catalysts containing different amounts of transition metals, by means of BET, XRD profile fitting and TPC reactivity tests, respectively.The synthesised powders showed a very limited hysteresis between the increasing and decreasing temperature curves and therefore should display no oscillations in working conditions.These systems could be a high temperature alternative to the hexa-aluminates and could avoid the homogeneous post combustion volumes typical of the hybrid and XONON combustors.

ChemInform Abstract: Challenges in Applied Oxidation Catalysis

AbstractReview: 23 refs.

Thermoelectric hydrogen gas sensor

A thermoelectric hydrogen gas sensor developed for leak detection in hydrogen stations has shown good hydrogen selectivity and wide hydrogen detection concentration ranging from 0.5 ppm to 5 %. We have demonstrated high sensitivity and reliability of the sensor exceeding conventional technology through a field test of one year. We could optimize the following three constituent technology elements to meet the social needs, i.e. new principle integrating catalytic combustion and thermoelectric conversion technology, micro-fabrication technology to realize the principle and high performance ceramic catalyst for gas combustion. In addition, the sensor performance evaluation technology established during the development has been proposed for ISO standardization.

Development of a Hybrid Catalytic Gas Burner

A prototype hybrid catalytic radiant gas burner suitable for EU condensing boilers (4–25 kW) was developed based on the novel concept of a rich catalytic/homogeneous combustion with interstage heat removal. An extensive experimental campaign was carried out to validate the hybrid catalytic combustion technology through the detailed characterization of the operating features of the prototype burner with special focus on the catalytic partial oxidation reactor, which simultaneously acts as a radiant element. Methane combustion tests were conducted also in direct comparison with two low-NOx forced air commercial systems: a fully premixed gas burner stabilized with a knitted metal wire cover and a blue–flame turbulent diffusive burner with multiple swirled fuel nozzles and high-speed air injection. The novel burner shows the potential for improved performance with regard to heat transfer efficiency, pollutants emissions, stability, rangeability, and safety of operation.

Challenges in applied oxidation catalysis

Haldor Topsøe A/S works on several aspects related to oxidation catalysis. In three examples, the challenges related to the development of catalysts and processes in oxidation catalysis are discussed. While certain challenges like the lowest possible pressure drop over the catalyst and price considerations are common for almost all areas of oxidation catalysis, other challenges may be specific for a particular area. In the first example, it is shown that the catalytic combustion technologies for off-gas purification have to tolerate a large variety of trace species involving traditional catalyst poisons including halogens and sulphur. The second example deals with oxidation catalysis for automotive applications. The main challenges within this area are often related to catalyst efficiency at the cold-start of a motor and catalyst lifetime, which depends upon the lifetime of the vehicle. Finally, the third example presents challenges within catalytic partial oxidation (CPO) of natural gas for hydrogen and synthesis gas production. Here, a high catalyst activity and selectivity are of utter importance due to ultra-short residence times of the feed gas in the channels of a monolithic CPO reactor. The examples show that industrial catalyst and process developments are often tailor-made solutions for a specific application.

A novel advanced oxidation process to degrade organic pollutants in wastewater: Microwave-activated persulfate oxidation

This article, for the first time, provides a novel advanced oxidation process based on sulfate radical (SO4*-) to degrade organic pollutants in wastewater: microwave (MW)-activated persulfate oxidation (APO) with or without active carbon (AC). Azo dye acid Orange 7 (AO7) is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 (up to 1000 mg/L) is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion (up to 0.50 mol/L), the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 (500 mg/L) is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 (484 nm), during MW-APO, two bands in the ultraviolet region (228 nm and 310 nm) are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO4*- is identified with quenching studies using specific alcohols. Both SO4*- and *OH could degrade AO7, but SO4*- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.

Cathlean: catalytic, hybrid, lean-premixed burner for gas turbines

Cathlean (an EU FP5 project) addresses the research and development of an advanced, ultra-low NO x , hybrid burner for gas turbines (present and future), that combines catalytic and lean-premix combustion components. Such a hybrid design enables this new technology to be introduced in a lower-risk manner. The catalytic elements serve to pretreat the fuel in order to enhance performance in terms of emissions (<3 ppmv NO x and <10 ppmv CO @ 15% O 2 at 50–100% load, for natural gas fuel), part-load stability (reducing the lean blow-out temperature by over 100 °C) and thermoacoustic phenomena (pulsations ≪ 0.3% of pressure). The principle scientific objective is to quantify the advantages of the hybrid burner in terms of the above-mentioned criteria, relative to traditional, lean-premixed combustors. The present paper describes the technical and organisational aspects of the project, including an outline of state-of-the-art catalytic combustion technology, technical specification of the advanced burner and a description of the methods used to attain project goals.

Achieving ultra low emissions in a commercial 1.4 MW gas turbine utilizing catalytic combustion

The drive to achieve low emissions from gas turbines has been an ongoing challenge for over 30 years with the reduction of NO x levels representing the most difficult issue. Catalytic combustion represents the technological approach that can achieve the lowest level of NO x , in the range of 3 ppm and lower depending on the combustion system design. The program to develop a catalytic combustion technology that can achieve ultra low levels of NO x , CO and unburned hydrocarbons (UHCs), applicable to a wide range of gas turbine systems and with long term durability is described. The technological approach is to combust only a portion of the fuel within the catalyst with the remaining fuel combusted downstream of the catalyst allowing the catalyst to operate at a low temperature and thus obtaining good long term catalyst durability. This catalytic combustion approach is then applied to a 1.4 MW gas turbine to demonstrate feasibility and to obtain real field experience and to identify issues and areas needing further work. The success of this demonstration lead to a commercial combustor design. This combustor and the final commercial package is described and the performance specifications discussed.

Development of catalytic combustion technology for single-digit emissions from industrial gas turbines

Catalytic combustion has demonstrated potential for attaining the firing temperatures of current and next generation gas turbines with nitrogen oxides (NO x ) production less than 3 parts-per-million by volume (ppmv), using natural gas fuel. The technology necessary to achieve this extremely low emissions performance with typical heavy-duty industrial and utility gas turbine operating cycle conditions, has been under development as a joint effort by the General Electric Company (GE) and Catalytica Combustion Systems Incorporated (CCSI) for several years with the support of Tokyo Electric Power Company Inc. (TEPCO). The most recent phase of this program, which began in late 1997, is focused on the durability of catalytic reactors in the gas turbine combustor operating environment. This paper presents the results of subscale catalytic reactor endurance testing at simulated steady-state and cyclic operating conditions typical of utility gas turbine service. The results of full-scale, full-pressure, laboratory testing of a catalytic combustion system having the most advanced catalytic reactor mechanical design features developed by CCSI are also presented.

Materials for catalytic gas combustion

Catalytic combustion, which permits to burn lean fuel/air mixtures is the key to environmentally preferable utilization of natural gas as an energy source and to removal of organic combustible gases from industrial effluents. The range of potential applications of catalytic combustion is large and can vary in temperatures of operation. Successful wide implementation of existing and of new catalytic combustion technologies will largely depend on the availability of suitable low cost catalytic materials. Since no single material can meet all demands, development of new catalysts needs to be orchestrated with the specific requirements of a given technology. The challenge is to combine existing knowledge and expertise in the area of combustion catalysts with innovations in their synthesis, improved formulations and applications in new specific composite forms. This paper outlines the current state of art and then focuses on perovskites for applications below 1,000 K. Examples of highly active formulations and of further enhancement of their activity through controlled synthesis and suitable support combinations are given. Criteria for the design of highly performing materials for high temperature catalytic combustion are also presented.

A catalytic combustion technology of concentrated VOCs in textile coating process

We developed a new process employing catalytic combustion for textile coating aimed at decreasing emissions of volatile organic compounds (VOCs) and saving energy at the same time. For this purpose, the VOCs are concentrated in a temperature swing adsorption (TSA) device. A fraction of the concentrated VOCs is completely oxidized on an electrically heated (EHC) system, and its combustion gas of EHC is supplied as the heating source via heat exchangers. The remaining concentrated VOC is recycled as a renewable energy source for the drying process to dual-type catalytic burners designed specially to operate with LPG and concentrated VOC at the same time. This system minimizes the problem of VOC emission and maximizes energy conservation by reusing the VOC, toluene, from textile coating.