砂型铸造固体废弃物综合利用概述

为了实现绿色铸造,在砂型铸造过程中需对铸造固体废弃物包括铸造废旧砂和除尘灰进行综合利用。本文概述采用热法和机械法对铸造废旧砂进行再生循环利用,采用免烧结造粒技术将铸造除尘灰制成免烧结陶粒,可替代建筑骨料,实现铸造除尘灰的综合利用,对废砂和废灰的综合利用,可实现铸造固体废弃物的“零排放”,从而实现绿色铸造。     

废旧资源再生利用大有可为

在我国经济社会发展面临着严峻资源环境约束的背景下,发展废旧资源再生利用产业具有极为重要的战略意义。通过发展废旧资源的再生利用产业,打造"资源-产品-废旧资源-废旧资源再利用"的循环发展模式,实现资源的循环利用,可以直接减少对原生资源的依赖,提升资源综合利用效率,是缓解经济发展资源约束的必然选择。废旧资源再生利用产业将会进入快速发展时期,有利于培育新的经济增长点。     

废旧纸回收利用日本占世界第一

美国的一个智囊团——世界动向研究所最近发表了关于世界再生利用现状的总结报告。根据这个报告,在废旧纸张的回收利用方面,日本占世界第一位,旧纸回收率达45%,荷兰居第二位,回收率为43%,也就是说:这两个国家现在所使用的纸,约有将近一半是回收再生纸。日本对废旧纸张的大力回收使垃圾抛弃量减少了40%。可见,废旧纸张的回收再生一方面大大减少了垃圾的清运、处理费用,另一方面又可节省大量的造纸原料,从而减少     

浙江省废旧金属再生利用的经验、问题及对策

文章分析了浙江省在废旧有色金属资源再生利用方面的几个典型模式的经验、存在问题及发展对策。     

生产者主导的废旧电器产业链主体责任运行机理

以循环经济为主导推动废旧电器再生利用产业链的健康运行是可持续发展战略的需要,废旧电器属性和特性决定了其产业链运行调控的复杂性。从产业链循环机理和促进物质循环视角,基于生产者责任延伸制阐述产业运行过程的生态设计与资源减量化、绿色营销与资源节约、递阶使用与环境保护等主体责任及运行机理,以促进其生态设计、清洁生产、友好销售、绿色消费、合理利用、多元回收、充分再用、高效再生的健康和有序发展。     

德国回收利用系统与塑料销售包装的再生

回收和分类自１９９１年６月起德国对包装物的生产者和销售者施行了产品责任制的原则。立法者通过包装法使企业承担废旧包装物的回收及其再生利用的义务。如果生产者和商家参加一个除地方政府垃圾处理系统之外的私营经济组织系统，他们即可从对家庭和小企业的销售包装物所...     

常温法废旧轮胎精细胶粉生产线建成

日前,一家以专业研究、开发、生产环保设备——废旧橡胶(轮胎)常温法精细胶粉成套生产线为主的浙江绿环橡胶粉体工程有限公司在浙江嵊州市成立。该公司是集绿色环保、新材料、资源再生利用为一体的高科技企业,累计投资1.5亿元建成国内最大规模的废旧轮胎常温精细粉碎设备生产基地及年产2万吨的精细橡胶粉加工示范生产线,并以此为中心,形成废旧轮胎回收处理、深加工及再生利用产业链的国家工业园区。废旧轮胎生产精细胶粉技术是一项符合国家政策扶持的有着广阔前景的朝阳产业。“废橡胶制取超细胶粉”、“建立废橡胶、废轮胎回收处理产业化基…     

再生铜行业环境管理问题的若干思考和建议

随着我国铜冶炼(原生铜和再生铜)行业对含铜二次资源需求量的增加,集废旧资源回收、拆解和分选、二次资源出售、铜再生利用于一体的产业链逐渐发展壮大起来。然而高能耗、高污染、低质量、低产出的特点在再生铜行业依然存在,环境监管政策和标准也不健全不完善。随着人们对美丽生态环境诉求的增加,必须加强有色金属行业的环境管理。本文对再生铜行业发展和环境管理做了一些思考,特别是对再生铜行业环境管理存在的问题进行了分析,并针对问题提出了几点政策性建议,以期为我国再生铜产业的环境友好发展和环境监管提供借鉴。     

我国废旧手机回收利用现状与对策分析

随着手机用户的增加，每年会产生大量的废旧手机。废旧手机一方面对环境构成潜在危害，一方面又具有回收利用的价值。本文针对我国目前废旧手机回收利用的现状，提出手机回收利用的措施，以有效应对电子垃圾污染，并实现资源的循环利用。     

我国废旧电器回收利用现状及存在的问题

人类社会发展到今天，创造了前所未有的文明，同时也带来了一系列环境问题。诸如废电脑、废家电、废通讯工具等废弃“电子垃圾”以及制造这砦电器过程中产生的各类废弃物占用着大量资源，对这蝼废旧电子器件和电子材料的不合理处置和回收会给环境造成极大污染。因此，广泛开展有关废旧电器和各类废旧电子材料回收利用方面的研究，使这些宝贵的二次资源得到科学合理的资源化和无害化处置，对保证人类所需生产和生活资源的永续利用，促进人类的可持续发展具有十分重要的意义。文章结合废旧电器回收利用进行了探讨。     

Green sand reclamation using a fluidized bed with an attrition nozzle

The objective of this study was to determine the technical feasibility of green sand reclamation using attrition in a gas–solid fluidized bed. Reclamation of foundry sand is becoming important as it may help solve concerns related to transportation and dumping of the used sand, and reduce production costs by recycling sand. The crucial step in green sand reclamation is the removal of small clay particles that are bound to the sand particles.For this study two different types of green sand were used and supplied by two different foundries. Tests were performed in a fluidized bed equipped with an attrition nozzle operating at pressures of either 350 or 550 kPa (50 or 80 psig). Attrition experiments for one green sand were performed on either unburned or burned (calcined) green sand, to determine the effect of prior calcination of the green sand on its reclamation potential by attrition. Calcination temperatures of over 700 °C were employed, and the results suggest that calcination facilitates the removal of clay from the green sand.Green sand was analyzed for clay and organic content, acid request, and particle size before and after attrition. Attriting calcined green sand produces the best results. Also experiments conducted at the highest attrition pressure of 550 kPa gave good results. According to the mass balance, the mass lost during the attrition process may be limited to less than 14%, and this could be considered acceptable. The volume of air required for the attrition nozzle is rather high and this may adversely affect the economics of the process.     

Regeneration of Nothofagus pumilio [Poepp. et Endl.] Krasser forests after five years of seed tree cutting

Nothofagus pumilio [Poepp. et Endl.] Krasser is a deciduous tree species that grows in Chile and adjacent Argentina between 36 and 56 degrees S, often forming the Andean tree line. Silvicultural systems proposed for this species integrate both regeneration and intermediate level operations in an orderly process for managing forest stands. The seed-tree method of regeneration has been used to manage even-aged stands of this species. This paper investigates the effect of seed tree cuttings on the regeneration of Nothofagus pumilio [Poepp. et Endl.] Krasser forest located in the Magallanes region (Chile). The studied forest was managed on an even-aged basis using a seed tree silvicultural system for regeneration with an intensity of cutting of 65-70% of the basal area and a minimum of 15 dominant lenga trees per hectare retained. A regeneration inventory sampling was used to quantify regeneration attributes in the study area. Regeneration was found to be significantly affected by the seed tree cuttings. In fact, the number of established individuals rose from 0.39 to 26.7 plants m(-2) pre-harvest to 9.2-21.5 plants m(-2) post-harvest, depending on the particular development stage. Total regeneration ranged from 9.5 to 48.2 plants m(-2). The number of plants established over the period 1992-1997 was related to the residual basal area, coverage and number of trees. However, mean tree height was not significantly related to any regeneration variable. Significant variables were used to establish a regeneration prediction model using single and multiple linear equations (R2<0.418). Consequently, the seed tree method of regeneration can be considered feasible for commercially valuable lenga forests, although this method, in its strictest application, will create many large, irregularly shaped, even-aged groups.     

POLLUTANTS ASSOCIATED WITH SAND AND SALT APPLIED TO ROADS IN MINNESOTA1

ABSTRACT: The component of snowmelt pollutant washoff due to sand and salt application to roadways in Minnesota is simulated. Laboratory methods are used to extract various pollutants from sand-salt mixtures commonly used in the Minneapolis-St. Paul Metropolitan Area of Minnesota for keeping winter road conditions safe. Values derived in the laboratory are compared with actual snowmelt runoff values to estimate the contribution of materials application. High concentrations of solids, phosphorus, lead and zinc in snowmelt from road surfaces axe due in part to sand and salt spread to improve winter driving conditions. The source of the sand and salt appears to be influential in determining the pollutant levels. Judicious use and careful application of materials can reduce the increment of pollution due to anti-skid sand and salt applied to road surfaces.     

Survival potential of Escherichia coli and Enterococci in subtropical beach sand: implications for water quality managers

Fecal bacteria have traditionally been used as indicator organisms to monitor the quality of recreational waters. Recent work has questioned the robustness of traditional indicators, particularly at seawater bathing beaches. For example, a study of Florida beaches found unexpectedly high abundances of Escherichia coli, fecal coliforms, and enterococci in beach sand. The aim of the present study was to explain these abundances by assessing the survival of E. coli and enterococci in beach sand relative to seawater. We used a combination of quantitative laboratory mesocosm experiments and field observations. Results suggested that E. coli and enterococci exhibited increased survivability and growth in sand relative to seawater. Because fecal bacteria are capable of replicating in sand, at least under controlled laboratory conditions, the results suggest that sand may be an important reservoir of metabolically active fecal organisms. Experiments with "natural" mesocosms (i.e., unsterilized sand or water rich in micropredators and native bacteria) failed to show the same increases in fecal indicators as was found in sterile sand. It is postulated that this was due to predation and competition with indigenous bacteria in these "natural" systems. Nonetheless, high populations of indicators were maintained and recovered from sand over the duration of the experiment as opposed to the die-off noted in water. Indicator bacteria may wash out of sand into shoreline waters during weather and tidal events, thereby decreasing the effectiveness of these indicators as predictors of health risk and complicating the interpretations for water quality managers.     

Research on distribution performance of desert sand for heat storage in downcomer

In this research, desert sand is used as the sensible heat storage medium, which exchanges heat with air in the downcomer to realize heat storage and heat release. The desert sand distribution uniformity has a significant impact on the heat exchange performance and efficiency between desert sand and air for the process of convection in the downcomer. Given the superiority of sensible heat storage in convective heat transfer between desert sand and air, distributors with cylinder or conical bore solid particles and homogeneity performance testing device are designed and manufactured on the basis of convection system equipped with solid particle–air downcomer. Then, the convection experiment between solid sand and air is researched. The greater the desert sand flow rate and higher the volume density, the larger the variance of regional mass flow rate and the worse the homogeneity performance. For the cylinder bore distributor, the smaller the sand particle size is, the greater affected the sand groups can be. The sand homogeneity performance is preferable with the two particle size ranges: 0.18-0.25 mm and 0.15-0.18 mm. The total sand flow rate decreases, but the uniformity improves with the increase of the air flow velocity, and the best distribution performance is achieved at an air velocity of 0.6 m/s. However, the distribution performance declines with the air flow velocity persistently increasing because the sand groups are pushed to one pipe side close to the wall. The sand groups deflect seriously with the air flow velocity increasing.     

胜利油田的油泥沙现状及处理工艺探讨

采油生产中的油泥（沙）是胜利油田的重要污染源,对含油泥（沙）处理国际上主要采用加碱、注热水、离心分离的方法将油、沙分离。含油泥（沙）的处理在国内尚无成熟工艺。目前,主要应采用以下方法：原油浓度低的油泥（沙）和油污土壤,主要采用微生物降解的方法进行处理;对原油浓度高的油泥（沙）和油污土壤主要采用物理化学的方法进行处理。可以预测,开展油泥（沙）处理及回收利用可获得巨大的经济效益和环境效益。     

Permeability predictions for sand-clogged Portland cement pervious concrete pavement systems

Pervious concrete is an alternative paving surface that can be used to reduce the nonpoint source pollution effects of stormwater runoff from paved surfaces such as roadways and parking lots by allowing some of the rainfall to permeate into the ground below. This infiltration rate may be adversely affected by clogging of the system, particularly clogging or covering by sand in coastal areas. A theoretical relation was developed between the effective permeability of a sand-clogged pervious concrete block, the permeability of sand, and the porosity of the unclogged block. Permeabilities were then measured for Portland cement pervious concrete systems fully covered with extra fine sand in a flume using simulated rainfalls. The experimental results correlated well with the theoretical calculated permeability of the pervious concrete system for pervious concrete systems fully covered on the surface with sand. Two different slopes (2% and 10%) were used. Rainfall rates were simulated for the combination of direct rainfall (passive runoff) and for additional stormwater runoff from adjacent areas (active runoff). A typical pervious concrete block will allow water to pass through at flow rates greater than 0.2 cm/s and a typical extra fine sand will have a permeability of approximately 0.02 cm/s. The limit of the system with complete sand coverage resulted in an effective system permeability of approximately 0.004 cm/s which is similar to the rainfall intensity of a 30 min duration, 100-year frequency event in the southeastern United States. The results obtained are important in designing and evaluating pervious concrete as a paving surface within watershed management systems for controlling the quantity of runoff.     

Bacterial removal and protozoan grazing in biological sand filters

The objective of the study was to investigate the importance of protozoan predation as a biological removal mechanism in sand filters used for purification of bacteria from wastewater. Eleven sand filter columns were seeded with a high dose of wastewater (70 mm d(-1)) and a high concentration (10(8) colony forming units [CFU] mL(-1)) of Aeromonas hydrophila (American Type Culture Collection [ATCC] 14715) for a period of 30 d. Water samples from three filter outlets were analyzed for the concentration of A. hydrophila. In addition, one filter column was sacrificed each sampling day for the quantification of A. hydrophila, culturable bacteria (heterotrophic plate counts, HPC), total bacterial counts, and protozoa in the sand. The mean removal efficiency of A. hydrophila in the sand filter columns was 4.7 log units. The concentration of A. hydrophila in the sand filter effluent, however, had a clearly time-dependent pattern from high (log 6) and unstable concentrations to low and more stable levels (log 2). The removal efficiency of A. hydrophila correlated significantly (P = 0.0005, r2 = 0.6) with numbers of protozoa in the sand filters. Significantly higher (P < 0.05) concentrations of A. hydrophila were observed in sand filter effluents from columns treated with the protozoan inhibitor cycloheximide, compared with nontreated columns. Results from the present study show that protozoan grazing plays an important role as a bacterial removal mechanism in sand infiltration systems.     

砂尘环境试验中颗粒沉降的数值模拟

对砂尘试验中试验段前后砂尘颗粒气固两相流场进行了数值模拟，计算中,将气相作为连续介质，采用两相耦合的Navier-Stokes湍流模型，，并用SIMPLE算法对流场进行数值模拟；将固相作为离散体系，采用颗粒轨迹法计算其运动轨迹。计算结果表明，试验段前后由于气流旋涡的诱导，使得砂粒会聚集在模型的前端和后端附近，说明此处较容易聚集砂粒。计算结果对自行设计与研制砂尘环境模拟试验设备具有重要的指导意义和实用参考价值。     

Recirculating sand filters for treatment of synthetic dairy parlor washings

Land-spreading and spray irrigation are the most widely used practices for the disposal of dairy wastewaters in Ireland but in some cases there can be problems due to contamination of surface and ground water. The use of intermittent sand filtration has been suggested as an alternative treatment process. However, a single pass through a sand filter limits denitrification because of the absence of reducing conditions following nitrification and the lack of an available carbon source. This leads to poor total nitrogen (TN) reduction and an effluent that is high in nitrate nitrogen (NO3-N). This paper follows a previous paper in which two instrumented stratified sand filter columns (0.9 and 0.425 m deep, and both 0.3 m in diameter) were intermittently loaded with synthetic dairy parlor washings at a number of hydraulic loading rates, leading to a TN reduction of 27 to 41%. In the present study, under a chemical oxygen demand (COD) of 23.4 g m(-2) d(-1), the TN was reduced by 83.2% when three-quarters of the sand filter effluent was recirculated through an anoxic zone. This produced an effluent NO3-N concentration of 60 mg L(-1). With recirculation, the improvement in the removal of organic matter and ammonia N (NH4-N) is minimal. Recirculating sand filters appear to offer a mechanically simple and effective method for the removal of nitrogen from dairy parlor effluents and are a significant improvement over a single-pass sand filter.