Ageing of HDPE geomembrane exposed to air,water and leachate at different temperatures

The latest findings regarding the long-term performance and service life of HDPE geomembrane (GM) samples exposed to air, water and leachate are presented based on data from samples that have been ageing for 8–10 years. Some of the GM samples are in Stage II, some in Stage III and some have completed all three stages of the service life. The paper provides: (1) improved data on antioxidant depletion rates for GMs immersed in air, water and leachate; (2) estimates of antioxidant depletion time (Stage I) at typical liner temperatures in air, water and leachate and, based on this data, an estimate for a composite liner at typical liner temperatures; (3) data regarding the changes in the physical and mechanical properties of the GM samples with time; (4) a surface analysis of virgin and aged GMs; (5) an initial estimate of the induction time (Stage II) and polymer degradation time (Stage III) and service lives of GM in laboratory immersion tests; and (6) predictions of the service life of leachate immersed GM at typical landfill temperatures. Based on these predictions, it appears likely that the service life of the specific GM tested immersed in leachate is likely to exceed 700 years and will probably be of the order of 1000 years (or longer) at 20 °C, more than 150 years and likely 225–375 years at 35 °C and more than 40 years and likely 50–90 years at 50 °C. The service life in a liner configuration may be expected to be longer than predicted here for immersion in leachate.     

Depletion of Antioxidants from a HDPE Geomembrane in a Composite Liner

The results of two series of accelerated aging tests are reported. Both series of tests were conducted at temperatures of 85, 70, 55, and 26°C over a period of about 3?years. In the simulated liner series, the top of the geomembrane was covered with a geotextile (protection) layer that was exposed to simulated municipal solid waste (MSW) landfill leachate while the bottom of the geomembrane was in contact with a hydrated geosynthetic clay liner. In the immersion series, the geomembrane was immersed in the simulated MSW leachate, and hence, both sides were exposed to leachate. The results from oxidative induction time tests indicate that the antioxidant depletion is about 2.2–4.8 times faster for the leachate immersed geomembrane than for geomembrane in a composite liner. The higher rates are attributed to the higher extraction of antioxidants from two sides of the geomembrane immersed in leachate. The measured antioxidant depletion rates are extrapolated to a range of temperatures (0–60°C) using Arrhenius modeling. At a liner temperature of 35°C, the calculated time for the depletion of antioxidants is about 40?years for a geomembrane in a composite liner compared to 10?years if it is simply immersed in leachate. These tests suggest that to obtain realistic estimates of geomembrane service life one needs data from tests that simulate the expected field conditions and that prediction based on immersion tests may underestimate the service life.     

Aging of HDPE Geomembrane in Three Composite Landfill Liner Configurations

Laboratory-accelerated aging experiments conducted to examine the depletion of antioxidant from a geomembrane (GM) underlain by a geosynthetic clay liner (GCL) are described. Three different “protection” layers between the GM and overlying gravel and leachate are examined: (1) A traditional nonwoven geotextile (GT); (2) a GT-GCL; and (3) a GT-sand-GT layer. The GT-GCL protection layer gives an antioxidant depletion rate 0.59 to 0.66 times slower than the GT layer alone. The GT-sand-GT layer gives depletion rates 0.72–0.75 times that of the conventional GT alone. Based on Arrhenius modeling, the time required for depletion of antioxidants at 35°C is estimated to be 65 years for a GM with a GT-GCL protection layer, 50 years for a GT-sand-GT layer, and 40 years for a conventional GT protection layer. These times are all significantly greater than the depletion time for GM immersed in leachate (10 years) for the geomembrane tested.     

Soil Isolation for Seismic Protection Using a Smooth Synthetic Liner

A synthetic liner consisting of a nonwoven geotextile over an ultrahigh molecular weight polyethylene, geotextile/UHMWPE, placed within a soil profile can dissipate seismic energy transmitted to the overlying soil layer and structure. This concept of soil isolation can be an effective and inexpensive way of reducing seismic ground motions through slip displacements. Shaking table tests on soil layers isolated using cylindrical and tub-shaped liners were conducted using harmonic and earthquake base excitations. The results show that an isolation liner can significantly reduce the accelerations at the surface of the isolated soil mass. Accompanying such a reduction in accelerations are slip displacements that manifest around the perimeter of the isolated soil. Because of the curved nature of the liner, permanent slips are minimized by the restoring effect of the gravitational forces of the isolated soil mass. Analytical results under field scale conditions indicate that a soil isolation liner can dramatically reduce the peak and spectral accelerations of a vertically propagating shear wave. Such a reduction can provide seismic protection to a structure founded on soil-isolated ground.     

对球磨机衬板选材的一点看法

球磨机是选矿工业中的主要设备。为了保护球磨机筒体内表面不受磨损和控制钢球在简体内的运动轧迹，筒体内铺有高锰钢衬板。主要介绍球磨机衬板装在不同部位，应选不同材质的衬板。     

Increasing the Utility of the Copper Cylinder Expansion Test

We report the development of a new methodology for analyzing CYLEX tests streak images. In these tests, the displacement of the wall of an explosive filled cylinder is obtained by backlighting the cylinder. The profile is imaged through a slit and streaked across a film record as the cylinder is detonated. A critical step in processing this data is the spatial calibration of the film and extraction of the profile of the cylinder from the image. Historically this has been a tedious task as it was performed by eye with the assistance of an optical comparator. Recently we developed an algorithm which automates the data calibration and extraction process of digitized streak records utilizing the Shen‐Castan edge detection algorithm and the image processing capabilities found in the IGOR PRO software. The new processing methodology greatly increases the resolution of the data, removes human subjectivity, and reduces analysis time from hours to seconds. The higher resolution of the new method has enabled much greater accuracy in measuring early‐time (<15 µs) expansion. With the aid of CTH hydrocode calculations, new fitting functions were developed to model both the early and late‐time expansion data. These functions contain physically meaningful fitting parameters and include terms which mimic the intensity and time scales of the shock and gas induced expansion of the cylinder independently. We demonstrate the methodology and hydrocode calculations on a recent CYLEX test series aimed at examining the effects of a plastic liner on high‐purity oxygen‐free copper cylinders filled with a high explosive.     

稀土白口铸铁衬板类零件的生产工艺

共晶碳化物呈连续网状分布是白口铁脆性的根源。运用稀土变质处理和热处理相结合的方法可以使共晶体碳化物断网、团聚化的原因在于变质处理后形成的有利的铸态组织更能籍助热力学与动力学规律,实现“小粒溶解,大粒团聚”。再加上充分奥氏体化后的二次碳化物弥散析出分布,白口铁性能得到了根本的改善。用它来制造衬板类零件,材料特性符合工况使用条件,其耐磨性约达高锰钢的２倍以上。     

Antioxidant Depletion from a High Density Polyethylene Geomembrane under Simulated Landfill Conditions

Accelerated aging tests to evaluate the depletion of antioxidants from a high density polyethylene geomembrane are described. The effects of temperature, high pressure, and continuous leachate circulation on the aging of geomembranes in composite liner systems are examined. The antioxidant depletion rates (0.05, 0.19, and 0.41?month?1 at 55, 70, and 85°C, respectively) obtained for the simulated landfill liner at 250 kPa vertical pressure are consistently lower than that obtained from traditional leachate immersion tests on the same geomembrane (0.12, 0.39, and 1.1?month?1 at 55, 70, and 85°C). This difference leads to a substantial increase in antioxidant depletion times at a typical landfill liner temperature (35°C) with 40 years predicted based on the data from the landfill liner simulators tests, compared to 15 years predicted for the same geomembrane based on leachate immersion tests. In these tests, the crystallinity and tensile yield strain of the geomembrane increased in the early stages of aging and then remained relatively constant over the testing period. There was no significant change in other geomembrane properties within the testing period.     

阿苏卫卫生填埋场边坡最终覆盖设计

现代卫生填埋工程(城市固体废弃物填埋场)是世界各地处理城市垃圾的主要方法。本文介绍了阿苏卫垃圾卫生填埋场边坡最终覆盖设计。对比了国内外最终覆盖的技术规范要求,参照国外技术规范,结合工程实际,分别对边坡最终覆盖总体方案设计中导渗层、基础层、阻隔层、排水层、营养层、植被层的结构选择进行了探讨,并对今后的生活垃圾卫生填埋场最终覆盖设计提出了建议。     

烟气脱硫装置的腐蚀与防护

湿法烟气脱硫装置因其处理烟气量大、脱硫率高、运行周期长、运营成本适中，已成为国内外火电厂烟气脱硫的主导装置。但该装置腐蚀环境苛刻、防腐蚀工程量大、装置腐蚀维修困难。本文针对湿法烟气脱硫装置的各区域不同的腐蚀环境特点，提出了防腐蚀复合衬里结构体系，为我国大型火电厂烟气脱硫装置的防腐蚀技术国产化提供了可靠的技术信息。