脱硝系统改造后炉膛负压波动原因分析及对策

选择性催化还原法(SCR)是目前燃煤电厂普遍采用的烟气脱硝技术,锅炉加装SCR脱硝装置后易出现空预器堵塞、炉膛负压异常波动等问题。以某燃煤机组为例,对空气预热器进出口压差、炉膛负压、入炉煤质、机组运行工况等进行综合分析,发现炉膛负压异常是由于锅炉进行SCR烟气脱硝时空气预热器发生局部堵塞,其根本原因为SCR装置过量喷氨或局部过量喷氨造成大量氨逃逸所致。并在分析原因的基础上提出治理对策。     

某300MW燃煤锅炉选择性催化还原脱硝导流系统的分析

为探究某300 MW燃煤锅炉选择性催化还原(Selective Catalytic Reduction,SCR)脱硝系统内烟道导流方案的可行性,利用FLUENT 6.3软件,对该导流方案下SCR系统的流场和氨浓度分布进行数值模拟研究.结果表明:烟道截面变化以及弯头偏转导致系统流场严重不均,且现有导流系统导流效果较差,AIG下游截面最大速度偏差达31.25 m/s,反应器入口速度也存在偏差,且尾部烟道内流场不均,会对下游设备产生影响;系统流场不均导致氨浓度不均,AIG下游截面氨的浓度偏差达60.0%,反应器入口截面氨的浓度偏差达38.4%,大的浓度偏差严重影响系统的脱硝效率,且反应器出口氨逃逸量达5.266 ppm,这会对大气造成二次污染.这些研究结果可为燃煤锅炉选择性催化还原脱硝导流系统的改进提供参考.     

660 MW 机组 SCR 脱硝板式催化剂磨损分析

针对马鞍山当涂电厂660MW机组脱硝SCR(选择性催化还原)板式催化剂发生局部严重磨损的现象,文章依据多次实际测量的数据进行对比分析,发现磨损呈现规律性分布,并且与脱硝反应器内部结构相关联。通过冷态流场计算及灰场数值计算分析研究表明:催化剂局部严重磨损的主要原因是由于反应器的顶部梁结构布局不合理,造成烟气流量、流速分布不均,引起催化剂局部出现严重磨损。针对这一原因,文章提出通过移除脱硝反应器上方的积灰三角以及改变喷氨烟道上方导流板的直径和角度等措施来改善脱硝反应器中烟气的流速分布。数值模拟的计算结果表明,在相同的运行工况下,改善后的脱硝反应器中烟气流速的均匀性得到了显著的提高,有效抑制了催化剂局部出现严重磨损等不良现象的发生。     

水泥窑用SCR脱硝反应器的模拟优化

随着氮氧化物的减排标准逐年严格,加快对选择性催化还原方法(SCR)的研究,提高烟气脱硝效率是水泥行业的当务之急。选用一款CFD软件对某日产5 000t级水泥熟料生产线初步设计的SCR脱硝反应器进行数值模拟研究,选用湍流模型、多孔介质模型对SCR反应器的流场进行模拟计算;运用组分输运模型和离散相(DPM)模型模拟NH_3与烟气的混合过程,研究喷氨面位置、喷氨口个数对混合过程的影响。结果表明:在烟道弯管处设置导流板,能有效地改善反应器内烟气流场,较优方案的烟气流速偏差仅为6.95%;喷氨面与催化剂层的距离及喷氨口个数都能影响NH_3与NO_x的混合。     

基于LSTM模型的SCR系统喷氨量串级预测控制

常规PID对时变、时滞的选择性催化还原脱硝技术(SCR)脱硝系统控制效果不佳,难以满足环保排放要求,因此提出了一种基于长短期记忆(LSTM)神经网络滚动预测的串级预测控制策略。将LSTM网络预测输出作为下一时刻输入数据,建立能自动微调的SCR系统模型;将LSTM网络与预测控制方法相结合应用于SCR喷氨优化控制中,并在此优化控制方案基础上加入PID控制,建立喷氨量串级预测控制系统。仿真结果表明:该控制策略对于SCR系统具有调节速度快、动态控制性能好等优点,且能克服模型失配的影响。     

SCR烟气脱硝技术

选择性催化还原（SCR）烟气脱硝技术是中国航天空气动力技术研究院所属航天神舟环境工程有限责任公司充分发挥流体力学专业优势．通过技术引进、消化、吸收与再创新开发的新型脱硝技术。该技术的脱硝率适当．催化剂比例合理：SCR反应器与锅炉炯道配合较好：氨站的安全性能较高：     

台湾中钢SCR触媒在烧结场脱硝与脱二噁英中的应用

台湾中钢SCR触媒是一种选择性催化还原(SCR,Selective Catalytic Reduction)双效触媒.其主要成分为V2O5/WO3/TiO2,最适反应温度介于250℃与320℃间,在此范围内,脱硝与分解二噁英的效率皆可达80%以上.它是一种板式触媒,抗飞灰腐蚀性高、堵塞机率与压降皆低.烧结场SCR触媒反应器主要由气气热交换器、再热燃烧器、导流板、筛板、喷氨格栅、触媒层与吹灰器构成,脱硝与分解二噁英之效率除受触媒活性质影响外,内部流场分布对于NH3与NOx混拌有显著影响,亦极为重要.CFD模拟可以帮助决定导板、筛板、喷氨格栅、触媒层的型式、数量与相对位置等以优化设计,相关CFD模型已在台湾中钢建立完成,计算结果可印证正式运转中的台湾中钢集团中龙钢铁烧结场SCR触媒反应器设计.     

脱硝系统运行调整试验分析

锅炉脱硝系统改造后,存在NOx排放达不到环保要求,受热面的磨损加剧,空气预热器结垢严重等问题.通过对脱硝系统进行运行优化调整试验,对SNCR喷枪及SCR喷氨格栅的开度和喷氨量进行了调整,使机组的NOx排放指标达到环保要求,提高了脱硝效率并减少了氨逃逸,有效地缓解了SCR下游设备的NH4HSO4沉降及堵灰状况,为同类型机...     

SCR脱硝系统喷氨隔栅优化调整试验研究

燃煤电厂超低排放改造后,存在SCR出口氨逃逸高于设计值且分布不均匀、空预器烟气侧阻力持续上升等问题,文章针对以上问题对SCR脱硝系统喷氨格栅优化调整进行试验.试验表明,通过有针对性地调节喷氨格栅开度,使得SCR装置的总尿素溶液用量下降,平均氨逃逸保持在6ppm左右,有效地降低了空预器堵塞的风险.     

超超临界锅炉喷氨优化与调整

某厂超超临界燃煤火电机组已完成超低排放改造,实现烟尘、SO₂和NO_x排放浓度远低于10 mg/Nm³、35 mg/Nm³和50 mg/Nm³。但锅炉中脱硝系统氨逃逸过大,导致脱硝系统后面的烟道内空预器及低温省煤器堵塞严重,严重影响了机组运行安全。通过测量该锅炉SCR反应器出口NOx浓度及氨逃逸量等参数,基于实测数据分析对锅炉喷氨量进行优化调整,降低SCR反应器出口氨逃逸量,从而有效缓解空预器及低温省煤器的堵塞状况,保证机组的高效安全运行。     

水泥炉窑SNCR-SCR联合脱硝中试实验研究

以水泥炉窑氮氧化物（NO_x）脱除为研究对象,分析烟气温度、入口NO_x质量浓度、氨氮摩尔比（NSR）、催化剂装载量和积灰时间等对选择性催化还原脱硝技术(SCR)性能的影响,研究水泥炉窑SNCR-SCR联合脱硝工艺. 依托浙江省某水泥熟料生产线,通过在已配套的SNCR脱硝装置后端引入SCR反应器深化烟气脱硝过程,建立体积流量为10 000 m³/h的SNCR-SCR联合脱硝系统. 结果表明,在烟气体积流量为10 000 m³/h,入口温度为340 °C,入口NO_x质量浓度为200~320 mg/m³的条件下,选择NSR为0.85~1.00、催化剂用量为8.1 m³时,SCR处理系统出口NO_x排放质量浓度为23.4 mg/m³,氨排放质量浓度为0.98 mg/m³,SCR系统脱硝率可达90.4 %. 中试实验NO_x的排放质量浓度、氨排放质量浓度均远优于《水泥工业大气污染物排放标准》（GB4915—2013）的规定,证明可实现水泥炉窑烟气氮氧化物的超低排放.     

Simulation calculation of solubility of insoluble compound MmAa in complex system

A simulation calculation model for the solubility of insoluble compound M _m A _a in complex system was established. According to coordination equilibrium principle, relevant dissociation reaction, complexation reaction, self-complexation reaction and protonation reaction during insoluble compound dissolving were considered and then the mass balance equations about solubility calculation were obtained. In the case analysis, the solubility of silver chloride in ammonia system was obtained by simulation calculation, and curved surface charts of thermodynamic equilibrium about the total concentration of silver ions, pH and concentration of ammonia ions were drawn correspondingly. The results show that under the conditions of room temperature and 6 mol/L ammonia concentration, the calculated solubility value of silver chloride (34 g/L) is close to the actual value (31 g/L), demonstrating that this model is suitable for solubility calculation of insoluble compound M _m A _a in the complex system.     

Selective catalytic reduction of NO with NH3 over sol-gel-derived CuO-CeO2-MnOx/γ-Al2O3 catalysts

Granular CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH₃ and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts is 300–400 °C. The catalysts maintain nearly 100% NO conversion at 350 °C. The °C NH₃ oxidation experiments show that both NO and N₂O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH₃, which improves the denitrification activity at low temperature. The over-oxidation of NH₃ at high temperature is the main cause leading to a decrease in the NO conversion. The NH₃ and NO desorption experiments show that NH₃ and NO can be adsorbed on CuO-CeO₂-MnO _x /γ-Al₂O₃ granular catalysts. The transient response of NH₃ and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process. Foundation item: Projects (50776037, 50721005) supported by the National Natural Science Foundation of China     

Effect of water washing pre-treatment on the properties of glass-ceramics from incinerator fly ash using electronic arc furnace

Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite (Ca2Al2SiO7) and akermanite (Ca2MgSi2O7). Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.     

Fabrication and characterization of nano silver powder prepared by spray pyrolysis

Silver powder was fabricated by spray pyrolysis, using 2%–20% AgNO₃ solution, 336–500 mL/h flux of AgNO₃ solution, 0.28–0.32 MPa flux of carrier gas and in the 620–820 °C temperature range. The effects of furnace set temperature, concentration of AgNO₃ aqueous solution, flux of AgNO₃ aqueous solution as well as carrier gas on the morphology and particle size distribution of silver powder, were investigated. The experimental results showed that with the high concentration of AgNO₃ aqueous solution, the average grain size of silver decreased with the increasing of furnace set temperature. But the gain size distribution was not homogenous, the discontinuous grain growth occurred. With the low concentration of AgNO₃ aqueous solution, the higher furnace set temperature made the nano sliver grains sintered together to grow. Nano silver powder about 100 nm was fabricated by spray pyrolysis, using 2wt% AgNO₃ solutions, 336 mL/h flux of AgNO₃ aqueous solution, 0.32 MPa flux of carrier gas at 720 °C furnace set temperature.     

Parameter Optimization on Experimental Study to Reduce Ammonia Escape in CO2 Absorption by Ammonia Scrubbing

In order to research ammonia escape in CO₂ absorption by ammonia scrubbing, ammonia escape was studied in CO₂ absorption process using the bubbling reactor in different conditions as gas flow rate, CO₂ ratio, absorbent temperature and ammonia concentration and quantity of escaped ammonia was measured by chemical titration. The results indicated that, the amount of ammonia escape can be around 20% of original amount in 90 min and the escaped amount will increase with the rise of gas flow rate, absorbent temperature, concentration of ammonia while decrease as CO₂ ratio goes up. Through the analysis of the law of ammonia escape, at the same time, combined with ammonia escape and the influence of the relationship between the CO₂ absorption efficiency, reducing ammonia escape working condition parameter optimization is given.     

Physical properties of crushed air-cooled blast furnace slag and numerical representation of its morphology characteristics

Physical properties and geometrical morphologies of crushed air-cooled blast furnace slag (SCR) and crushed limestone (LCR) were comparatively investigated. The shape, angularity, surface texture and internal pore structure of aggregate particles for different size and gradation were numerically represented by sphericity (ψ) and shape index (SI), angularity number (AN), index of aggregate particle shape and texture (IAPST), porosity and pore size, respectively. The results show that SCR is a porous and rough aggregate. Apparent density, void, water absorption and smashing index of SCR are obviously higher than those of LCR with the same gradation, respectively. However, bulk density of SCR is lower than that of LCR with the same gradation. SI, AN, IAPST and porosity of SCR are obviously higher than those of LCR with the same gradation, respectively. The smaller particle size of SCR, the larger of its AN, IAPST and porosity.     

墙式切圆锅炉燃烧过程的数值模拟

为研究墙式切圆锅炉炉内的燃烧问题,采用Fluent模拟软件,分析了炉内的速度场、温度场和NOx的分布规律.结果表明,炉膛燃烧器区横截面的切圆直径随着炉膛高度的增加逐渐增加;在炉膛中心纵截面上,炉内中心温度低于两侧温度,而且随着炉膛高度的增加,温度先增后降,炉壁附近出现局部高温;NO浓度沿高度方向先升后降.     

Dissolution kinetics of malachite in ammonia/ammonium sulphate solution

The dissolution kinetics of malachite was investigated in ammonia/ammonium sulphate solution. The effects of ammonia and ammonium sulphate concentration, pH, leaching time, reaction temperature, and particle size were determined. The results show that the optimum leaching conditions for malachite ore with a copper extraction more than 96.8% are ammonia/ammonium concentration 3.0 mol/L NH₄OH + 1.5 mol/L (NH₄)₂SO₄, liquid-to-solid ratio 25:1 mL/g, leaching time 120 min, stirring speed 500 r/min, reaction temperature 25 °C and particle size finer than 0.045 mm. The dissolution process of malachite with an activation energy of 26.75 kJ/mol is controlled by the interface transfer and diffusion across the product layer. A semi-empirical rate equation is obtained to describe the leaching process and the reaction orders with respect to concentration of ammonia and ammonium sulphate are 2.983 0 and 0.941 1, respectively.     

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69μm, holding at 80℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2：1, and the ratio （g/mL） of solid to liquid being 1：10.