Palladium/perovskite/zirconia catalytic premixed fiber burners for efficient and clean natural gas combustion

The present work was aimed at developing and testing – under realistic operating conditions on a specifically assembled pilot plant – a novel generation of catalytic premixed fiber burners for low-environmental-impact natural gas combustion. The adoption of a palladium-LaMnO₃-zirconia catalyst developed on purpose, where zirconia acts as a structural promoter and the noble metal/perovskite synergism is effectively exploited, led to enhanced performances with respect to non-catalyzed burners. In particular, lower CO and NO_x emissions were recorded over a wide field of operating conditions (basically excess of air with respect to the stoichiometric condition and nominal heat power).

Also, the effect of ageing and poisoning induced by sulfur compounds added as odorants in the natural gas network was studied, with promising indications as regards the burners durability: the overall performance, in terms of pollutant emissions, appeared to have slightly improved after prolonged exposure to SO₂ and high temperatures.     

天然气催化燃烧在燃气轮机和锅炉中的应用

综述了天然气催化燃烧技术在燃气轮机和热水锅炉中的应用和研究现状及其发展方向,介绍了几种不同形式的催化燃烧器和一些典型的设计实例,指出催化燃烧技术仍存在的问题。     

Development of a catalytic combustor for a heavy-duty utility gas turbine

Catalytic combustion is an attractive technology for gas turbine applications where ultra-low emission levels are required. Recent tests of a catalytic reactor in a full scale combustor have demonstrated emissions of 3.3 ppm NO_x, 2.0 ppm CO, and 0.0 ppm UHC. The catalyst system is designed to only convert about half of the natural gas fuel within the catalyst itself, thus limiting the catalyst temperature to a level that is viable for long-term use. The remainder of the combustion occurs downstream from the catalyst to generate the required inlet temperature to the turbine.

Catalyst development is typically done using subscale prototypes in a reactor system designed to simulate the conditions of the full scale application. The validity of such an approach is best determined experimentally by comparing catalyst performance at the two size scales under equivalent reaction conditions. Such a comparison has recently been achieved for catalysts differing in volume by two orders of magnitude. The performance of the full scale catalyst was similar to that of the subscale unit in both emission levels and internal temperatures. This comparison lends credibility to the use of subscale reactors in developing catalytic combustors for gas turbines.     

Mn、Fe取代六铝酸盐的结构和甲烷催化燃烧性能

采用化学可控共沉淀法制备了系列取代六铝酸盐LaMe_xAl_12-xO_19-δ（Me＝Fe、Mn）催化剂,研究了焙烧温度和Fe、Mn的离子取代量对催化剂比表面、结构及甲烷催化燃烧活性的影响.结果表明,催化剂前驱物经1000℃焙烧,催化剂中开始有六铝酸盐晶相生成; 当焙烧温度提高到1200℃时,样品主要以六铝酸盐晶相存在.增加Fe、Mn离子取代量可以提高六铝酸盐晶相的结晶度,但同时导致晶粒增大,引起比表面下降.由XPS和TPR分析表明,Mn在六铝酸盐结构中以+2价和+3价混合价态存在,而Fe以+3价形式存在.用Fe和Mn离子取代晶格中的Al³⁺大大提高了六铝酸盐对甲烷催化燃烧活性,当Mn离子的取代数为1,Fe离子的取代数为2时催化剂的活性最高.     

天然气催化燃烧在红外加热技术方面的应用

介绍了天然气催化燃烧红外辐射加热技术在工业上的应用和研究现状。该技术克服了一般天然气红外辐射加热燃烧温度高、容易回火、NOx、CO和UHC排放量高等缺点,通过粮食处理、喷漆干燥和杀灭害虫等实例说明该技术在工业中的广泛应用。该技术常用催化剂为纤维催化剂,催化剂活性组分为Pd或Pt,载体纤维包括陶瓷纤维、玻璃纤维和金属纤维等。纤维催化剂气体阻力小,比表面积大,容易成形和安装,其研究和开发较快,并得到广泛应用。     

天然气催化燃烧器独石通道内气体温度分布

研究了天然气催化燃烧器蜂窝状独石通道内气体温度分布。由于催化反应区在独石通道内10 mm左右基本结束,将催化剂独石长度减至20 mm进行实验,由于在高热强度下燃烧不易稳定,为降低独石入口前端腔内混合气温度,将一块20 mm长的无催化剂独石连接在镀钯催化剂独石的入口前组成组合催化剂独石,发现组合催化剂独石燃烧稳定。     

High temperature stable magnesium oxide catalyst for catalytic combustion of methane: A comparison with manganesesubstituted barium hexaaluminate

The activity of magnesium oxide for catalytic combustion of methane was examined and the results were compared with experimental results for manganese-substituted barium hexaaluminate. The catalysts were calcined at temperatures up to 1 500°C and the effects of temperature, space velocity and calcination temperature were examined. The catalysts were also characterized with BET and XRD. For magnesium oxide calcined at 1 100°C the ignition temperature T_10% was decreased by 270°C compared to the non-catalyzed reaction. For the same catalyst T_50% was measured to be 795°C. The corresponding temperature for the hexaaluminate was 640°C. The difference between the two catalysts decreased after calcination at 1 500°C. For the magnesium oxide the influence of catalytically initiated homogeneous gas phase reactions was studied by varying the post catalytic volume of the reactor (and hence the residence time in the heated zone after the catalyst). It was shown that these catalytically initiated homogeneous gas phase reactions are significant for the methane conversion.     

载体孔道密度对天然气催化燃烧的影响

制备了不同载体孔道密度的Pd/γ-Al_2O_3和六铝酸盐蜂窝催化剂,在自行设计的催化燃烧实验装置上进行了天然气催化燃烧实验。考察了载体孔道密度、空燃比和燃气流量对催化燃烧效果的影响。结果表明,载体孔道密度影响孔道内壁面反应和气相反应变化以及燃烧流体孔道内的流动及燃烧过程的传热传质,当载体孔道密度为200目时,流速减小,加强了气流与壁面上的浓度边界层中反应物质的交换,温度峰值增大,HC排放少;载体孔道密度为400目,气相反应减少,不会产生局部高温区,NO_x排放小。空燃比影响催化反应炉内各床层轴心温度以及炉内温度峰值的出现位置。随着燃气流量的增加,温度随之上升,1200℃以上时会产生较多的NO_x。     

SrxCa1-xNiAl11O19催化剂的制备及其催化甲烷燃烧活性研究

用异丙醇盐水解法制备SrxCa1-xNiAl11O19(x=1.0,0.75,0.5,0.25,0)催化剂,通过X射线衍射、比表面积分析等实验技术及甲烷燃烧,对催化剂的结构和性质进行了考察。研究了掺杂不同量的钙离子对催化剂的结构以及对甲烷催化燃烧活性的影响。结果表明,催化剂在1 200℃焙烧后可以形成完整的六铝酸盐晶型,同时具有较高的催化性能和高温稳定性,不同量的Ca离子掺杂对于催化剂的比表面积有较大的影响。Sr0.25Ca0.75NiAl11O19催化剂具有较好活性,其起燃温度(T10%/℃)为590℃,完全转化温度(T90%/℃)为730℃。     

二甲醚燃烧用掺杂钡、镍六铝酸盐催化剂的研究

二甲醚是易液化，便于运输，清洁化的新能源。当作为燃料使用时，采用催化燃烧的方法能使得燃烧的起燃温度降低和提高燃烧转化率，克服了普通燃烧的缺点，实现了清洁燃烧。对二甲醚催化燃烧用的催化剂BaNiAl11O19-δ进行了制备与研究。采用溶胶-凝胶法制备六铝酸盐催化剂BaNiAl11O19-δ,考察其对新能源二甲醚催化燃烧反应的活性，并用TG—DTA对催化剂的性质进行考察。结果表明，加入经800℃焙烧4h后又在1200℃焙烧了2h的催化剂，比未加催化剂的燃烧体系T10降低了50℃。用溶胶一凝胶法制备的六铝酸盐催化剂BaNiAl11O19-δ对二甲醚催化燃烧反应具有较高的催化活性。     

Application of catalytic combustion to a 1.5 MW industrial gas turbine

A catalytic combustor is described for a 1.5 MW gas turbine engine. The catalyst temperature is limited and the high combustor outlet temperatures required by the turbine are generated downstream of the catalyst. The combustor design places a low NO_x preburner upstream of the catalyst and uses this preburner to achieve optimum catalyst operation by providing the desired catalyst inlet temperature. The combustor system employs the catalyst during engine acceleration and loading. The catalyst design has been tested on a sub-scale rig under full pressure and flow conditions simulating turbine operation over the entire operating range including acceleration and loading. The design should achieve emissions at full load operation of <3 ppm NO_x and <10 ppm CO and UHC. Low emissions operation is expected over the 75–100% load range. In addition, long-term sub-scale rig test results are reported at simulated full load operating conditions including cyclic operation and full load trips.     

Characteristics of a stepwise fuel-rich/lean catalytic combustion of natural gas bearing ammonia

A two-step fuel-rich/fuel-lean catalytic combustion seems to be one of the most effective methods to control simultaneously the NO generation and the hydrocarbon (HC) conversion from fuel-bound nitrogen. By controlling equivalent air ratio, space velocity, inlet temperature, and catalyst component, the HC and ammonia conversion efficiency higher than 95% could be achieved, with ammonia conversion to NO remaining below 5%. The experimental results would be applied to the combustion of land fill gas and to gasified refuse-derived fuels as a method of minimizing NO generation.     

不同方法制备K2MnAl11O19六铝酸盐催化剂及其甲烷的燃烧活性

介绍了共沉淀法和异丙醇盐水解法制备了六铝酸盐催化剂K2MnAl11O19,用XRD、BET、SEM和TG-DTA技术及甲烷燃烧活性对催化剂进行了表征和活性验证。结果表明,两种方法所制备的催化剂经1200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中异丙醇盐水解法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性。     

Development of a catalytic burner with Pd/NiO catalysts

A catalytic burner was studied which can be used as a heater operated at medium temperature. The catalytic combustion was initiated by an igniter which was placed on the exit surface of the catalyst layer. Noble metal catalysts (Pd/NiO) which were supported on alumina washcoated honeycomb were used, whose maximum heat-resisting temperature is about 900°C. The optimal operating conditions for stable catalytic combustion were obtained by means of analyzing the catalytic combustion region, the temperature distribution, and the combustion efficiency.     

Combustion synthesis of perovskite-type catalysts for natural gas combustion

Combustion synthesis has been applied to LaMnO₃ production with a view to boosting its activity towards natural gas combustion by enhancing its specific surface area. With a highly exothermic and self-sustaining reaction, this oxide can be quickly prepared from an aqueous solution of metal nitrates (oxidisers) and urea (fuel).

The favourable conditions for LaMnO₃ formation were sought: only fuel-rich mixtures are effective, but carbonaceous deposits are formed when too much urea is used. In the field of operating conditions in which the combustion synthesis reaction takes place, the specific surface areas were not dramatically higher than those obtained with traditional methods; moreover, even short thermal treatments have been found to rapidly deactivate the catalysts by rapid sintering. With a view to tackling these problems, NH₄NO₃ was chosen as an additive for its low costs, highly exothermic decomposition and because it generates gaseous products only, without altering the proportion of the other elements in the catalysts. With ammonium nitrate, specific area was enhanced from 4 m²/g up to about 20 m²/g. A short thermal treatment at 900 °C partially deactivates also the NH₄NO₃-derived catalysts. It was found that NH₄NO₃-boosted mixtures produce materials whose activity, after a similar thermal treatment, behave practically as the perovskites obtained by the “citrates” method.

Combustion synthesis is though rather cheap—in terms of reactants employed—and quick, given that the process requires few minutes at low temperature without successive calcination. However, the main drawback of this method is that hazardous or polluting compounds are emitted during the synthesis (mainly NH₃ or NO_x).

The MgO introduction, which should act both as a structural promoter and as a sulphur poisoning limiting agent, has proved to be harmful: since MgO does not physically interpose between perovskite grains, it does not offer resistance to deactivation induced by high temperatures.     

Development of a novel catalytic burner for natural gas combustion for gas stove and cooking plate applications

On the request of Gaz de France Research Department, Catator AB has designed, constructed and evaluated a catalytic burner, based on Catator's patented wire mesh catalysts, for natural gas combustion in gas stoves or cooking plates. The results have shown that burner operation results in extremely low NO_x emissions (1–3 mg NO_x/kWh), acceptable CO-levels (0–15 mg CO/kWh), relatively high thermal efficiencies over a broad range of power inputs (40–50% for 1–4 kW) and a long catalyst life-time (>10 000 h). Other advantages of this burner design are its compactness and ease of cleaning. The critical concern is the high emissions of unburned hydrocarbons measured at slow cooking mode (<1 kW), which is believed to be overcome by developing and implementing an appropriate heat-exchanger with the burner.     

Advanced technology catalytic combustor for high temperature ground power gas turbine applications

We report results from a lean burn ultra-low emission catalytic combustor. In a sub-scale rig, atmospheric testing with methane demonstrated NO_x<3, CO<5, and UHC<1 ppm, with stable combustion at inlet temperatures of 400–500°C (750–1020°F) and combustor discharge temperatures of 1150–1540°C (2100–2800°F). Catalyst temperatures were held well below metal substrate material limits, while combustor discharge temperatures of up to 1540°C (2800°F) were achieved.     

Performances of a catalytic foam trap for soot abatement

A catalytic trap for soot particles was prepared by deposition of Cu–V–K–Cl catalyst on a ceramic foam. Catalytic trap performances were evaluated by treating the exhaust of a gas oil burner under different operating conditions. The results obtained showed that ceramic foam is a particularly suitable support for this application since it yields low gas pressure drop, good soot collection efficiency (“deep bed” filtration mechanism), high thermal shock resistance and good contact throughout the filter between soot particles and catalyst surface. In addition, the catalytic foam trap is able to spontaneously regenerate at operating conditions comparable to those typical of diesel engine exhaust and after more than 70 test hours it retains its activity towards soot oxidation.     

催化燃烧法处理聚酯工艺废气的实践

探索用催化燃烧方法处理聚酯生产工艺废气的可行性,并在生产装置上进行中试。介绍了废气处理装置的主要设计参数、处理工艺流程。对装置的安全运行,催化剂的寿命,运行经济性进行了讨论。结果表明:相对于目前的喷淋处理法,该法处理简单,不产生二次污染,成本较低,处理聚酯生产工艺废气是完全可行的。     

High-pressure reaction and emissions characteristics of catalytic reactors for gas turbine combustors

The reaction and emissions characteristics of catalytic reactors comprising noble metal catalysts were investigated using homogeneous mixtures of natural gas and vitiated air at pressures up to 2.9 MPa. The mixture temperatures at inlet ranged from 500 to 700°C and the fuel-air ratio was increased till the exit gas temperature reached about 1200°C. Values of combustion efficiency greater than 99.5% and nitrogen oxides emissions for all catalytic reactors tested were less than 0.2 g NO₂/kg fuel (2 ppm (15% 0₂) ) for all reactors at reactor exit gas temperatures higher than about 1100°C. Combustion efficiency decreased with increasing pressure in the heterogeneous-reaction controlled region, though a pressure increase favored homogeneous, gas phase reactions. Appreciable reactivity deterioration by aging for 1000 h at 1000°C was observed at lower mixture temperatures. A two-stage combustor comprising a conventional flame combustion stage and a catalytic stage was fabricated and its NO,_x emissions and performance were evaluated at conditions typical of stationary gas turbine combustor operations. About 80% reduction in NO,_x emissions levels compared with flame combustion was attained at 1 MPa pressure and 1180°C exit gas temperature, together with complete hydrocarbon combustion.