Evaluation of Continuous Performance Monitoring Techniques for Hazardous Waste Incinerators

This paper discusses monitoring the waste destruction efficiency of hazardous waste incinerators. The particular problem is to ensure that incinerators do not release, without detection, significant quantities of waste as a result of operating fluctuations or equipment degradation. To detect these conditions, continuous, automated, and real-time source monitoring is required. Detection of degraded performance by monitoring and measuring waste compounds directly is not presently possible on a continuous basis. An alternative is to use commercially available continuous monitors to measure combustion intermediates (e.g., CO or hydrocarbons) and thereby infer waste destruction efficiency. Required, however, is a correlation between the emission of intermediates and the emission of waste. In this paper, the response of a number of these continuous monitors is compared with waste destruction efficiency measurements from a laboratory scale, liquid-spray incinerator operated on fuel oil doped with model waste compounds: benzene, chlorobenzene, acrylonitrile, and chloroform. Total hydrocarbon and CH₄ measurements are found to vary with waste emission in a nearly linear manner; however, a substantial increase in CO emission occurs before a significant amount of waste is released. These results suggest that CO may serve as an indicator of the approach of waste release, while total hydrocarbons may provide an indicator of immediate waste release.     

Continuous Infrared Analysis of N2O in Combustion Products

Nitrous oxide (N₂O) levels in the atmosphere are increasing, potentially contributing to the greenhouse effect and depletion of stratospheric ozone. From a limited data base, combustion sources have been identified as a major anthropogenic source of N₂O. However, the existing data base (obtained by traditional grab sampling techniques followed by gas chromatographic analysis) is in question due to the discovery of a sampling artifact. A continuous on-line N₂O analyzer would enable and facilitate the accurate characterization of combustion sources over a range of operating conditions, and also aid in the development of an appropriate sampling technique. This paper addresses the development of a continuous measurement technique, and the evaluation and initial use of a field prototype continuous N₂O analyzer developed at the UCI Combustion Laboratory in cooperation with a major instrument manufacturer. The analyzer is capable of measuring N₂O levels down to a few ppm. The analyzer has been evaluated and used to study the N₂O emissions from a pulverized coal-fired boiler. The N₂O levels found with the analyzer are substantially lower than levels previously attributed to such sources. Initial N₂O measurements made with the analyzer suggest that N₂O levels are not a substantial fraction of the NO_X levels, as previously suggested.     

Chemical Transformations of Nitrogen Oxides While Sampling Combustion Products

The present study reviews the sampling environments and chemical transformations of nitrogen oxides that may occur within probes and sample lines while sampling combustion products. Experimental data are presented for NO_x transformations in silica and 316 stainless steel tubing when sampling simulated combustion products in the presence of oxygen, carbon monoxide, and hydrogen. A temperature range of 25° to 400°C is explored. In the absence of CO and H₂, 316 stainless steel is observed to promote the reduction of nitrogen dioxide to nitric oxide at temperatures in excess of 300°C, and silica is found to be passive to chemical transformation. In the presence of CO, reduction of N0₂ to NO is observed in 316 stainless steel at temperatures in excess of 100°C, and reduction of NO₂ to NO in silica is observed at 400°C. In the presence of H₂, NO₂ is reduced to NO in 316 stainless steel at 200°C and NO_x is removed at temperatures exceeding 200°C. In silica, the presence of H₂ promotes the reduction of NO₂ to NO at 300°C and the removal of NO_x above 300°C.     

基于Verhulst模型的新建隧道顶板下沉预测研究

隧道顶板下沉量预测对隧道安全施工十分重要.通过分析隧道下沉过程,指出其具有"S"型曲线特征,探讨了采用Verhulst模型进行隧道顶板下沉预测的适用性和可行性,并运用MATLAB软件开发相关程序,模拟遵赤高速公路中枢隧道YK39+134.6断面沉降过程,获得相应的预测方程.通过对比其预测结果、回归分析预测结果和实测值,发现该模型的顶板沉降预测值与实测值最接近,证实运用灰色Verhulst模型预测隧道顶板沉降量是合理、可行的.