Determining the air excess in the heating of coke furnaces. 3. Calculation of the air excess

The chemical mechanism by which coke-oven gas burns in the heating ducts of coke ovens is considered. A formula is obtained for the air excess. In contrast to the existing formula, the proposed version takes account of not only the content of oxygen, carbon monoxide, and carbon dioxide in the combustion products but also the content of sulfur dioxide, hydrogen, methane, nitrogen oxides. Analysis of the combustion products in the heating ducts of a coke battery with 30.9-m³ ovens shows that the content of incombustible components in the coke-oven gas may reach 3%. Calculation of the air excess by means of the proposed formula permits improvement in the uniformity of the temperature distribution in the heating system, the prevention of specific lining defects, and decrease in atmospheric emissions when the coke battery is heated by means of coke-oven gas. The proposed method of determining the air excess may be used not only in equipment for coke production but also in other metallurgical systems where coke-oven gas is burned.     

Gas combustion in the heating channel of a coke oven

The concentration, temperature, and velocity fields of the gas fluxes during gas combustion in the heating channel are calculated on the basis of the mathematical model for a coke oven with a dust-free cokedischarge system. The influence of the air excess and the gas dynamics in the furnace wall on the concentration of combustion products is studied.     

Analysis of the volatile combustion products of vinyl plastics

The extensive use of plastics for insulation and building materials has created interest in the possible toxicity of their combustion products. Three poly(vinyl chloride) homopolymers, a vinyl chloride-vinyl acetate copolymer, and formulations of two of the homopolymers and the copolymer have been examined to determine the composition and toxicity of their combustion products. Differential thermal analysis and thermal gravimetric analysis were used to study the breakdown process which occurred in several steps, the largest and first being the release of hydrogen chloride from the polymer at about 300°C. Approximately 50 products of combustion were then determined qualitatively by using either infrared spectroscopy or a combination of gas chromatography and mass spectroscopy. Quantitative analyses were carried out on 22 of the combustion products, and quantitative changes with varying air supply, temperature, and heating rate were determined. A comparison of the products of the polymers and their formulations is given.     

Regimes of the Combustion of Organic Coal–Water Fuels

The results of an analysis of the combustion behavior of the drops of organic coal–water fuels (OCWFs) prepared based on the flotation products (cakes) of the enrichment the coal of five grades (longflame, gas, coking, low-caking, and lean coals) and two petroleum products (petroleum residue and spent turbine oil) are presented. The experiments were performed under the conditions of the stationary fastening of an OCWF drop on the junction of a quick-response thermocouple in a flow of heated (from 500 to 1000°C) air. The following three combustion regimes were revealed for all of the test OCWF compositions: stepwise regime with slow heating (smoldering), intense gas generation regime with the boiling of liquid fuel components (boiling), and regime with a distinct tear-off zone of gas flow (torch). It was shown that the occurrence of the above combustion behaviors substantially depends on the characteristics of the OCWF components: the ash content and the yield of volatile substances of coal cakes and the boiling points and the ignition and combustion temperatures of the petroleum products used. Based on the results of the experiments, the ranges of air temperature changes characteristic of each of the three combustion regimes of fuel suspensions were established.     

Reducing the flammability of ultra-high-molecular-weight polyethylene by triphenyl phosphate additives

The thermal degradation and combustion of ultra-high-molecular-weight polyethylene (UHMWPE) doped with triphenyl phosphate (TPP) at atmospheric pressure was studied by molecular beam mass spectrometry, dynamic mass spectrometric thermal analysis, microthermocouples, thermogravimetry, gas chromatography/mass spectrometry. The kinetics of thermal degradation of pure UHMWPE and that mixed with TPP at high (≈150 K/s) and low (0.17 K/s) heating rates was investigated. The effective values of the rate constant and activation energy of the thermal degradation reaction were determined. Burning velocity and temperature profiles in UHMWPE and UHMWPE + TPP flames were measured. The composition of the combustion products in a flame zone adjacent to the burning surface of the sample was determined. TPP vapor in the flame was detected. The addition of TPP to UHMWPE was found to reduce the flammability of the polymer. It is shown that TPP acts as a fire retardant in both the condensed and gas phases.     

Determining the air excess in the heating of coke furnaces. 1. Adequacy of the chemical analysis

The traditional chemical framework for determining the air excess in the heating of coke furnaces is discussed. In determining the air excess, no account is taken of numerous chemical reactions associated with the combustion of the fuel gas in the heating channels. In fact, it is necessary to determine combustion products other than oxygen, carbon monoxide, and carbon dioxide: specifically, hydrogen, methane, nitrogen oxides, and sulfide. The formula for the air excess must therefore be corrected to include the content of those components.     

Co-current combustion of oil shale - Part 1: Characterization of the solid and gaseous products

Co-current combustion front propagation in a bed of crushed oil shale (OS) leads to the production of liquid oil, of a flue gas and of a solid residue. The objective of this paper was to provide a detailed chemical characterization of Timahdit oil shale and of its smoldering combustion products. The amount of fixed carbon (FC) formed during devolatilization is measured at 4.7% of the initial mass of oil shale whatever the heating rate in the range 50-900 K min⁻¹. The combustion of oil shale was operated using a mix of 75/25 wt. of OS/sand with an air supply of 1460 l min⁻¹ m⁻². In these conditions, not all the FC is oxidized at the passage of the front, but 88% only, with a partitioning of 56.5% into CO and the rest into CO₂. A calorific gas with a lower calorific value of 54 kJ mol⁻¹ is produced. Approximately 52% of the organic matter from OS is recovered as liquid oil. The front decarbonates 83% of carbonates.     

甲醇弛放气掺入量的变化对焦炉加热的影响

结合开滦京唐港煤化工园区生产实际,根据甲醇弛放气波动造成煤气热值变化,来计算所需空气和产生废气量以及炉温的变化。结果表明,弛放气掺入量在0%～40%时,若未调节入炉空气量,弛放气每降低10%,理论燃烧温度会升高85℃左右,并提出弛放气波动情况下的调节意见,为焦炉加热调温提供参考。     

双燃料燃烧炉在固碱生产中的应用

针对天然气与电石炉气成分及热值的差异,对固碱生产装置中燃烧炉炉头、工艺配管、控制系统、风机及安全装置等进行了技术改造,实现了天然气一电石炉气双燃料燃烧炉的正常运行。     

典型宁东煤热解阶段硫迁移路径的分子动力学模拟

以典型宁东煤为研究对象,采用工业分析、元素分析、X射线光电子能谱(XPS)分析和¹³C固体核磁共振(¹³C-NMR)等手段研究了煤样的元素组成、原子比、官能团类型及含量等分子结构特征,构建了含硫原子的宁东煤有机化学结构。通过反应力场分子动力学(ReaxFF MD)模拟,考察了热解温度和升温速率对典型宁东煤热解产物的影响,结果表明:热解温度低于1500 K时,热解产物中气体组分较少,重质焦油较多;随着热解温度升高(1500 K~2500 K),大分子化合物和活性自由基均会发生二次反应产生小分子碎片,气体产物快速增加;增大升温速率会减少C1~C4有机气体的生成,促进重质焦油的产生;16 K/ps和2500 K分别是合适的模拟升温速率和热解温度。污染性元素S的迁移路径分析结果表明:宁东煤热解过程中S原子容易迁移到相对分子质量小的有机碎片中,最终将以硫氢根的形式与H自由基结合生成H₂S参与后续燃烧反应。     

Toxicity of pyrolysis and combustion products of poly-(vinyl chloride)

The pyrolysis and combustion products of poly-(vinyl chloride) and those of some of its polymer, especially of vinyl chloride with vinylidene chloride, were analysed using gas chromatography and gas chromatography mass spectrometry. The toxic effect of the individual products on the human organism was evaluated and presumed total toxicity of the poly-(vinyl chloride) combustion products (0.3g PVC products per m³) was determined.     

煤气燃烧对火焰高度影响的研究

焦炉立火道中煤气的燃烧过程属于扩散燃烧,扩散燃烧有利于焦饼高向加热的均匀性和降低能耗。文中计算了扩散燃烧的火焰高度,对焦炉使用高炉煤气与焦炉煤气加热及废气循环对火焰高度的影响进行了比较。同时还分析了影响火焰高度的因素和解决焦炉高向加热的措施。     

Monitoring of emissions from coke-battery heaters

The operation of electrochemical gas analyzers in coke-battery monitoring is considered. The sealing of the battery’s heating system may affect the readings of the gas analyzer. The presence of free hydrogen in the combustion products distorts the readings of the CO cell in the absence of hydrogen compensation. For reasons of reliability, calculation of the SO₂ concentration is recommended.     

Dynamic combustion regimes of the Ti-(Ti+0.5C) layered system in a concurrent nitrogen flow

The filtration combustion of a layered porous fill consisting of alternating layers of a mixture of Ti + 0.5C a titanium powder with forced concurrent filtration of nitrogen was studied for the first time. The gas flow through the sample was provided by a vacuum pump attached to the lower end of the fill. The presence of the concurrent gas flow radically changes the character of propagation of the combustion front and the structure and composition of the products obtained. The layers consisting of carbonitride and titanium nitride make a single unit. The experiments provided scientific bases for the production of new laminated and composite ceramic materials by dynamic filtration combustion. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 44–51, November–December, 2008.     

Production of H2 and medium Btu gas via pyrolysis of lignins in a fixed-bed reactor

Lignins are generally used as a low-grade fuel in the pulp and paper industry. In this work, pyrolysis of Alcell and Kraft lignins obtained from Alcell process and Westvaco, respectively, was carried out in a fixed-bed reactor to produce hydrogen and gas with medium heating value. The effects of carrier gas (helium) flow rate (13.4–33 ml/min/g of lignin), heating rate (5–15°C/min) and temperature (350–800°C) on the lignin conversion, product composition, and gas yield have been studied. The gaseous products mainly consisted of H₂, CO, CO₂, CH₄ and C₂₊. The carrier gas flow rate did not have any significant effect on the conversion. However, at 800°C and at a constant heating rate of 15°C/min with increase in carrier gas flow rate from 13.4 to 33 ml/min/g of lignin, the volume of product gas decreased from 820 to 736 ml/g for Kraft and from 820 to 762 ml/g for Alcell lignin and the production of hydrogen increased from 43 to 66 mol% for Kraft lignin and from 31 to 46 mol% for Alcell lignin. At a lower carrier gas flow rate of 13.4 ml/min/g of lignin, the gas had a maximum heating value of 437 Btu/scf. At this flow rate and at 800°C, with increase in heating rate from 5 to 15°C/min both lignin conversion and hydrogen production increased from 56 to 65 wt.% and 24 to 31 mol%, respectively, for Alcell lignin. With decrease in temperature from 800°C to 350°C, the conversion of Alcell and Kraft lignins were decreased from 65 to 28 wt.% and from 57 to 25 wt.%, respectively. Also, with decrease in temperature, production of hydrogen was decreased. Maximum heating value of gas (491 Btu/scf) was obtained at 450°C for Alcell lignin.     

Thermogravimetric and mass-spectrometric study of the thermal decomposition of PBCT resins

The thermal decomposition of three commercial samples of carboxy-terminated polybutadiene (PBCT) resins was studied by thermogravimetric analysis (TGA) at heating rates varying from 2° to 100°C/min. Kinetic parameters of the decomposition process at different heating rates were evaluated by means of the Fuoss method.¹ The decomposition process and the activation energy values are found to be dependent on heating rate. Mass-spectrometric analysis of the decomposition products shows that the pyrolysis products of PBCT resins are mainly low molecular weight hydrocarbons: ethylene, acetylene, butadiene, propadiene, vinylcyclohexene, etc. The rates of evolution of these hydrocarbon products vary with the carboxy content of the PBCT resin. Based on this, a carbonium ion mechanism has been suggested for the thermal decomposition. The data generated from this work are of importance for a consideration of the mechanism of combustion of composite solid propellants based on PBCT binders.     

可燃固体废弃物的热解动力学

研究了垃圾中各种可燃物的热解特性 ,得出了各自的热解动力学参数 ,并对各种可燃物的热解特性进行了评价 .     

PYROLYTIC KINETICS OF COMBUSTIBLE OF MSW

研究了垃圾中各种可燃物的热解特性 ,得出了各自的热解动力学参数 ,并对各种可燃物的热解特性进行了评价 .     

非等温动力学研究煤的着火特性

以乌煤和自洗蒙古煤为原料,采用TG-DTG法,应用非等温动力学方法研究了升温速率和粒径对煤着火特性的影响,并得出两种煤燃烧过程的动力学参数.根据煤燃烧产物释放特性指数R的大小来确定煤的燃烧性能.在实验条件下得出以下结论:1)乌煤在升温速率较低时,挥发分释放特性指数R值大,燃烧特性好,对煤着火有利;而升温速率对自洗蒙古煤的燃烧性能影响不大;2)乌煤:粒径0.2 mm～0.3 mm失重量最大,粒径小于0.15 mm和0.15 mm～0.2 mm失重量基本一致.自洗蒙古煤:粒径0.2 mm～0.3 mm失重量最小,粒径小于0.15 mm失重量和0.15 mm～0.2 mm失重量基本一致;3)通过对两种煤燃烧过程的动力学分析,得出乌煤燃烧过程的活化能高于自洗蒙古煤.     

An effect of tar model compound toluene treatment with high-temperature flames

A major drawback of renewable gasification technologies is contamination of the syngas produced with “tar”, which can induce fouling in downstream equipment. The effect of continuous injection of acetylene and hydrogen high-temperature flames into the blend of gases containing a tar model compound toluene in order to decompose the latter has been studied. The experimental results indicate that treatment of the reaction mixture with the acetylene and hydrogen oxy-flames promotes reforming of toluene into H₂ and CO. The same heating values of the flames result in different ratios between H₂ and CO; this points out on a difference in mechanism of that reforming implying an interaction between toluene and combustion products which include a large specter of intermediate species (radicals). A better understanding of these mechanisms will help to obtain an optimal ratio between external oxy-flame and internal combustion regularly employed to increase the temperature of the producer gas in order to decompose volatile organics and tars in it. Utilization of oxy-flames for high-temperature clean-up of producer gas (gasification products) is very similar to the application of plasma steam tested with positive results in semi-industrial gasification units.