Aspen Plus-based simulation of a cement calciner and optimization analysis of air pollutants emission

The cement industry is a typical high energy consumption and heavy pollution industry, in which amounts of CO₂, NO, NO₂, and SO₂ discharge from the pre-calciner kiln system and cause severe greenhouse and acid rain effects. Meanwhile, reasonable division of the combustion environment in the calciner is the main method to control the formation of pollutant gases. In this article, a calciner process model in Aspen Plus is proposed based on the combustion mechanism analysis of the Dual Combustion and Denitration calciner (DD-calciner) and verified by industrial data. Then, for a concrete DD-calciner, the article studies the effects of the flow rate of coal and tertiary air on flue gas compositions and effects of the staging combustion technology on the NO _x , SO₂, and CO concentrations in the flue gas. Through comparing the model results with the relevant environmental standards, the optimization analysis for staging combustion parameters of the calciner is done, and the result shows that when the proportion of tertiary air entering the pyrolysis and combustion zone is controlled within the range of 57–65.52% (0.89 < α < 1.004), all the gas pollutants emit within accepted standards simultaneously. The calciner process model outlined in this article describes the key processes of the physical and chemical reactions in the calciner. It can be used to study the key operation and design parameters which influence the flue gas constituents, so as to provide data support for determining the pollutant emission reduction plan of the cement industries with a view to reduce air pollutant emission.     

Computational modelling of turbulent flow,combustion and heat transfer in glass furnaces

For the combustion of natural gas in high temperature glass furnaces a computational model “Furnace” has been developed. It includes 3-D turbulent flow, flame chemistry, radiative heat transfer and the formation of soot and of the pollutant NO. Turbulent fluctuations have been taken into account, and are shown to have a large effect on thermal radiation and NO-formation. Spectral behaviour of gas radiation results in changes of heat transfer efficiency up to 5%, depending on refractory emissivity. The model has been employed to predict NO formation for different burner geometries. In general, a decrease in mixing of gas and air results in a reduction of 1600 to 400 ppm in flue gas NO concentration. Except for some of the low mixing flames, however, they lead to a lower burnout and a very high CO level in the flue gas. A comparison with semi-technical furnace tests shows that the model can predict NO formation reasonably well. With this computational model the designer of furnaces and burners can study further possibilities for increased furnace performance and low NO emissions.     

Formulation Optimization of Diltiazem Hydrochloride Matrix Tablets Containing Modified Ispaghula Husk Using Factorial Design

The purpose of this study was to develop modified-release tablets of diltiazem hydrochloride using physically modified ispaghula husk as a hydrophilic matrixing agent. Ispaghula husk and water were exposed to heat in a hot air oven or microwave oven. The treated samples were evaluated for swelling and rigid gel formation. Microwave oven treated samples showed rigid gel formation and hence they were systematically studied using 3² factorial design using heating time and amount of water as independent variables. Diltiazem tablets were prepared using treated samples and analyzed for in vitro drug release. A polynomial equation was generated using statistically significant terms such as heating time, X₁, amount of water, X₂, and X₁X₂ and X₁² for predicting time required for 80% drug dissolution. Heating time was found to have a predominant effect in sustaining the drug release. A contour plot is presented for interpretation of the results. The tablets exhibited more axial swelling than radial swelling. The results of F-statistics revealed that the drug release pattern fit well in the Higuchi model.     

严寒地区大型燃气锅炉排烟加热空气方式的优化与应用

由于严寒地区冬季室外空气的温度低,助燃的空气进入锅炉会产生爆燃和震动、燃烧效率降低。同时大型供热系统回水温度高,燃气锅炉排烟温度较高,排烟余热深度利用中,烟温降低程度受到回水温度条件限制。本文提出了新的烟气加热空气方式,与常规烟气加热空气方式相比,减少了设备耗材、体积及阻力,应用于大型燃气供热锅炉烟气余热深度梯级利用的节能改造。工程实测表明:烟气余热回收和助燃空气加热系统,可将烟气温度降到锅炉回水温度及以下,锅炉燃气利用热效率提高了13.2%,烟气余热回收率为66.7%,实现了排烟余热深度利用,并解决了助燃空气进入锅炉产生爆燃和震动的问题,为严寒地区燃气锅炉烟气余热深度利用与助燃空气加热提供了参考。     

Carbothermic Reduction of Zinc Oxide Concentrate by Microwave

1.IntroductionExtractive metallurgy of zinc by conventional py-rometallurgical processes involves serious problems suchas low efficiency and environmental pollution.New en-ergy sources(like microwave)with higher efficiency andlower pollution have recently been paid much attention.Microwaves correspond to electromagnetic waves ofwavelength from1mm to1m.Microwave as a sourceof energy has found many industrial applications.Usingmicrowave energy has several advantages such as volu-metric,local an…     

新疆某电厂#1机组排烟余热回收系统的设计与运行

论述了新疆某厂一期锅炉增设烟气余热回收系统（LLHS）降低排烟温度的技术路线及节能效果,提出热系统参数的优化原则及纯凝-供热联合系统切换运行模式。增设LLHS后排烟温度降低不小于25℃。机组年均供电煤耗降低2.56g/kWh（含供热期）,每台锅炉年节省标煤2270t,年节水量4.37万t,减少烟囱内净烟气含水率24%,为脱硫系统正常运行提供了保证。     

Effects of sodium modification, different reductants and SO(2) on NO reduction by Rh/Al(2)O(3) catalysts at excess O(2) conditions

Although many catalysts of NO reduction have been developed, the presence of excess O(2) and SO(2) significantly inhibits their performance when they are used to treat the incineration flue gas. To solve such problem, this study prepared new Rh/Al(2)O(3) catalysts and investigated the effects of Na modification, SO(2) and different reductants. Experimental results indicated that the average removal efficiency of NO at such high O(2) concentrations exceeded 80% when the Rh/Al(2)O(3) catalysts were used. CO was a better reductant than C(3)H(6) and the best concentration ratio of reductant/NO was equal to 1. Adding Na to modify Rh/Al(2)O(3) catalysts significantly enhanced the removal efficiency of NO from 80 to 99% at 250-300 degrees C, especially at relative high SO(2) concentrations. Unfortunately, Rh-Na/Al(2)O(3) catalysts do not have long-time activities for NO reduction, possibly because of the formation of NaNO(3). Both Rh/Al(2)O(3) and Rh-Na/Al(2)O(3) catalysts have good performance for NO reduction, they can feasibly be used to reduce NO in the flue gas from waste incineration.     

A dual-use of DBD plasma for simultaneous NO(x) and SO(2) removal from coal-combustion flue gas

Dielectric barrier discharge (DBD) was investigated for the simultaneous removal of NO(x) and SO(2) from flue gas in a coal-combustion power plant. The DBD equipment was used in either a mode where flue gas was directed through the discharge zone (direct oxidation), or a mode where produced ozonized air was injected in the flue gas stream (indirect oxidation). Removal efficiencies of SO(2) and NO for both methods were measured and compared. Oxidation of NO is more efficient in the indirect oxidation, while oxidation of SO(2) is more efficient in the direct oxidation. Addition of NH(3), has lead to efficient removal of SO(2), due to thermal reaction, and has also enhanced NO removal due to heterogeneous reactions on the surface of ammonium salt aerosols. In the direct oxidation, concentration of CO increased significantly, while it maintained its level in the indirect oxidation.     

基于康达效应的热缩烘箱流场分析及结构优化

目的对壁纸包装机烘箱进行建模与分析,优化烘箱结构。方法基于流体力学,建立热收缩烘箱的能量方程和运动学方程。通过数值计算得到烘箱流场分布及仿真云图,进而研究烘箱喷口、底面、回风口的流场分布及对热缩性能的影响。基于计算结果,进行回风口尺寸和结构的改进与优化,对多种拟定的改进结构进行分析计算,提取计算数据并对比确定相对最优模型。结果将确定的最优改进模型加入烘箱中进行整体模拟计算,提取优化后的计算数据,完成结构优化设计。结论优化后的壁纸包装机烘箱结构在一定程度上改进了原结构中存在的不足,能够较好地满足壁纸包装工程中的工艺需要。     

印刷机进风系统的结构分析与优化

目的研究凹印机烘箱进风管道的结构,以减少管道内的涡流,提高热风流动均匀性。方法建立烘箱结构的三维模型和进风管道的流体域,确定进风系统管道结构数值模拟的可行性研究方案。设计制作烘箱管道结构的实验模型。验证理论研究和数值模拟结果的正确性。结果实验结果表明,流场的速度及压力特性与数值模拟的特征结果具有较好的一致性。结论通过三维结构建模、仿真分析和实验验证,提高了管道的热风效率,节约能耗效果显著。     

Calculation of a Three-Dimensional Temperature Field with Allowance for the Radiation Heat Exchange in Chambers of Tubular Ovens with Acoustic Burners

A three-dimensional calculation of the heat transfer in the chamber of a technological tubular oven with the combustion of methane in air with acoustical burners of a floor flame has been carried out. The calculation method is based on the joint numerical solution of the difference analogs of the three-dimensional equations of radiation, energy transfer, and turbulent motion of flue gases and the model of methane combustion in air. The entire spectral region is divided into six bands to account for radiation selectivity. The organization scheme of three-dimensional modeling of the burner operation is shown. Some results of numerical studies of heat and mass transfer in a combustion chamber are given.     

焦炉煤气制氢方法的比较及成本分析

使用焦炉煤气为原料分离的化工产品主要是氢气和天然气。小规模焦炉煤气制氢一般采用变压吸附法。大规模焦炉煤气可先分离出LNG,再提取氢气。分别对两种制氢方法做了介绍和成本分析。     

Modelling and simulation of stamp-charged coke making by 2-D discrete element method

Coking of coal blends using high-volatile coals with poor caking properties can be achieved by densifying the coal prior to carbonisation. In stamp-charged coke making, the coal charge is compacted to one large cake before entering the coke oven. A coal cake density of approximately 80% of the coal solid density is needed to produce a high-quality coke. Also, sufficient mechanical strength is required when transferring the cake from the stamping machine to the oven. To gain insight into the densification process and cake structure a 2-dimensional computational model based on the discrete element method (DEM) was set up. The model was validated against force and displacement patterns from laboratory stamping tests. Stamper movement in response to cake properties could be reproduced. The approach also enables tracking of cake porosity, particle rearrangement, stress and strain rates, etc. This offers additional possibilities for studying the densification process and understanding mechanical strength development.     

Industrial oven improvement for energy reduction and enhanced process performance

Industrial ovens consume a considerable amount of energy and have a significant impact on product quality; therefore, improving ovens should be an important objective for manufacturers. This paper presents a novel and practical approach to oven improvement that emphasises both energy reduction and enhanced process performance. The three-phased approach incorporates product understanding, process improvement and process parameter optimisation. Cure understanding is developed using Dynamic Mechanical Analysis (DMA) and CIE-Lch colour tests, which together highlight the impact of temperature variation on cure conversion and resulting product quality. Process improvement encompasses thermodynamic modelling of the oven air to evaluate the impact of insulation on temperature uniformity and system responsiveness. Finally, process parameters, such as temperature, pressure negativity and air flow, are optimised to reduce energy consumption. The methodology has been effectively demonstrated for a 1 MW festoon oven, resulting in an 87.5 % reduction in cooling time, saving 202 h of annual downtime and a reduction in gas consumption by 20–30 %.     

Kinetics of Oxidative Dearsenication of Niccolite Ore with Microwave Radiation

The rate processes of oxidative dearsenicationof niccolite ore in microwave oven and inconventional furnace were measured withthermogravimetric technique.The results show thatthe dearsenication rate of niccolite ore withmicrowave heating becomes faster than that withconventional heating.Under the conditions of an approximate linearheating and a definite air flow,the oxidativedearsenication process of niccolite ore is mainlycontrolled by interfacial chemical reaction.The ex-perimental data are in agreement with     

1913t／h超临界四角切圆锅炉冷态空气动力场的试验研究

为了解某电厂1913t／h超临界四角切圆锅炉大修后炉内空气动力场的分布特性,进行了锅炉冷态空气动力场试验。对6台磨煤机的一次风挡板特性及两侧二次风道挡板特性进行了测量,并对一、二次风风速进行了调平,对贴壁风速及水平烟道风速进行了测量。试验结果表明,一、二次风挡板特性较好,经调整各粉管及燃烧器喷口风速均匀,贴壁风速及水平烟道风速合理。     

混合导体透氧膜反应器中焦炉煤气重整制合成气的实验研究

研究了以焦炉煤气为原料在BaCo0.7Fe0.2Nb0.1O3-δ(BCFNO)透氧膜反应器中制合成气。实验结果表明,BCFNO膜反应器的自催化性能差。加入催化剂后,膜反应器的重整性能得到明显提高,在875℃,焦炉煤气中甲烷转化率为87.0%,产物中氢气和一氧化碳选择性分别为78.3%、105.6%,透氧量达到15.8ml/(cm2.min)。焦炉煤气中的甲烷在膜反应器中反应路径为首先焦炉煤气中的氢气与膜片透过去的氧反应生成水,然后甲烷再与水重整生成氢气和一氧化碳。实验过程中,透氧膜没有出现破裂,BCFNO透氧膜反应器在富氢的焦炉煤气下显示出很好的稳定性。     

On-line analysis of nitrogen stable isotopes in NO from ambient air samples

A method was developed for the on-line analysis of nitrogen stable isotopes at the natural abundance level in NO in order to study the NO contribution to the nitrogen cycle in ecosystems and in the atmosphere. The method enables a quick and accurate determination of 15N/14N ratios for NO and consists of the following steps: (a) accumulation of NO from air samples on a molecular sieve of 5 A, (b) desorption of NO from the molecular sieve during 15 min of heating at 350 degrees C (an offset of Deltadelta 4.6% must be corrected for), (c) trapping and cryofocusation of the desorbed NO on a PoraPlot Q matrix at -196 degrees C during heating, (d) release of the trapped NO from the PoraPlot Q matrix followed by chromatographic separation, reduction to N2, and isotopic composition analysis. A minimum sample size of 125 nmol of NO is recommended. A correction function for the calculation of the delta15N-NO values was introduced for sample sizes from 125 to 220 nmol of NO. Measurements of NO in automobile exhaust have proven the applicability of the developed method.     

非常规天然气液化研究进展

煤层气、合成天然气、焦炉煤气、化工尾气等非常规天然气液化是回收利用的有效途径.由于含有大量氧、氮或氢,通常需要进行低温精馏提纯,非常规天然气液化技术与常规天然气有较大差别.本文回顾了近年与非常规天然气液化相关的研究进展.对于煤层气,国外大型煤层气项目因制冷剂供应原因均采用级联式流程,国内则注重小型或撬装式装置的开发以及...     

Volatile organic compound constituents from an integrated iron and steel facility

This study measured the volatile organic compound (VOC) constituents of four processes in an integrated iron and steel industry; cokemaking, sintering, hot forming, and cold forming. Toluene, 1,2,4-trimethylbenzene, isopentane, m,p-xylene, 1-butene, ethylbenzene, and benzene were the predominant VOC species in these processes. However, some of the chlorinated compounds were high (hundreds ppbv), i.e., trichloroethylene in all four processes, carbon tetrachloride in the hot forming process, chlorobenzene in the cold forming process, and bromomethane in the sintering process. In the sintering process, the emission factors of toluene, benzene, xylene, isopentane, 1,2,4-trimethylbenzene, and ethylbenzene were over 9 g/tonne-product. In the vicinity of the manufacturing plant, toluene, isopentane, 1,2,4-trimethylbenzene, xylene and ethylbenzene were high. Toluene, 1,2,4-trimethylbenzene, xylene, 1-butene and isopentane were the major ozone formation species. Aromatic compounds were the predominant VOC groups, constituting 45-70% of the VOC concentration and contributing >70% to the high ozone formation potential in the stack exhaust and workplace air. The sequence of VOC concentration and ozone formation potential was as follows: cold forming>sintering>hot forming>cokemaking. For the workplace air, cokemaking was the highest producer, which was attributed to the fugitive emissions of the coke oven and working process release.