Chlorine Control by In-Line Fluxing Operations

The history of the metallurgy of aluminum and its alloys has been closely associated with chlorine and fluorine. Fluorine is important in smelting operations. This paper deals with melting operations and discusses the use of chlorine to remove aluminum and magnesium oxides, dissolved hydrogen, and minor elements such as sodium and magnesium to obtain aluminum alloys of a quality satisfactory for modern use in transportation, aircraft, building, and other industries. A development period of ten years has resulted in a series of graded processes that accomplish this chlorine use effectively enough that atmospheric contamination is no longer a problem. The use of these processes which operate between the melting and casting units is discussed in some detail. The use of a new process to remove magnesium from recycled scrap aluminum is also considered.     

Control of Organic Emissions from Surface Coating Operations

ABSTRACT

Step tracer tests were carried out on lab-scale biofilters to determine the residence time distributions (RTDs) of gases passing through two types of biofilters: a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow. Results were used to define the flow patterns in the reactors. “Non-ideal flow” indicates that the flow reactors did not behave like either type of ideal reactor: the perfectly stirred reactor [often called a "continuously stirred tank reactor" (CSTR)] or the plug-flow reactor.

The horizontal biofilter with back-mixing was able to accommodate a shorter residence time without the usual requirement of greater biofilter surface area for increased biofiltration efficiency. Experimental results indicated that the first bed of the modified biofilter behaved like two CSTRs in series, while the second bed may be represented by two or three CSTRs in series. Because of the flow baffles used in the horizontal biofilter system, its performance was more similar to completely mixed systems, and hence, it could not be modeled as a plug-flow reactor. For the standard biofilter, the number of CSTRs was found to be between 2 and 9 depending on the airflow rate. In terms of NH₃ removal efficiency and elimination capacity, the standard biofilter was not as good as the modified system; moreover, the second bed of the modified biofilter exhibited greater removal efficiency than the first bed. The elimination rate increased as biofilter load increased. An opposite trend was exhibited with respect to removal efficiency.     

中外饮食业油烟控制标准比较

饮食油烟的污染日益受到人们的重视，许多国家已制订了油烟排放的标准。作者从不同角度比较了4个国家或地区的饮食业油烟控制标准的异同，为我国今后饮食业油烟污染控制的技术开发、标准修订、产品推广等提供参考。     

Some Chemical Aspects Of Kraft Odor Control

The principal sources of odor in the kraft pulping process are the digester, the direct evaporator, and the recovery furnace. Control of odor from the digester requires the confinement of the noncondensable gases and their destruction by chlorination, burning, or by some other means. Control of odor from the direc’ evaporator depends on efficient black liquor oxidation. The recovery furnace, which potentially can be the worst source of air pollution, must be operated properly within its rated capacity. The chemistry of various control measures is discussed.     

Recovery and characterization of the humate-like salified polymeric organic fraction (lignimerin) from Kraft cellulose mill wastewater

A dark and complex salified organic polymeric mixture, named lignimerin, was for the first time recovered from Kraft cellulose mill wastewater (KCMW) and characterized by chemical, spectroscopic and relative molecular weight (RMW) analysis. Lignimerin proved to be composed of polyphenols (57.00%), carbohydrates (22.26%) and proteins (7.42%). It also contained metals (6.93%), mainly Ca and, to much lower extent, Mg, Na, Al, Fe, K, Mn, Zn and Cu, bound to the carboxylate and phenate groups. The distribution of lignimerin RMW was assessed to be approximately between 1000 and 8600Da, as well as to consist of lignin and tannin, protein and polysaccharide moieties, strongly aggregated each other. H-lignimerin, its acid derivative, revealed a chemical composition and a RMW distribution very close to that of lignimerin, but a marked metal cations decreasing (1.60%) with respect to lignimerin (6.93%). The humic acid-like nature of both the polymers was assessed. Their potential use as bio-adsorbents of heavy metals is briefly discussed.     

Control of Fine Particulate (PM2.5) Emissions from Restaurant Operations

ABSTRACT

This paper describes efforts to reduce particulate matter (PM) emissions from restaurant operations, including application of an existing control method to a new equipment type. Commercial charbroiling in the South Coast Air Basin results in emissions of approximately 10 tons/day of fine particulate matter ₍PM_2.5) and 1.3 tons/day of volatile organic compounds (VOCs). Over a seven-year period, the South Coast Air Quality Management District worked with industry to develop test methods for measuring emissions from various cooking operations, evaluate control technologies, and develop a rule to reduce these emissions.

Of the two basic types of charbroilers—chain-driven and underfired—underfired produce four times the emissions when equivalent amounts of product are cooked. Cost-effective control technology is currently available only for chain-driven charbroilers. The application of flameless catalytic oxidizers to chain-driven charbroilers was found to effectively reduce emissions by at least 83% and is cost-effective. The catalysts have been used worldwide at restaurants for several years. Research efforts are underway to identify control options for underfired charbroilers.

Implementation of Rule 1138, Control of Emissions from Restaurant Operations, adopted November 14, 1997, will result in reductions of 0.5 tons/day of PM_2.5 and 0.2 tons/day of VOCs. Future rules will result in reductions from underfired charbroilers and possibly other restaurant equipment when cost-effective solutions are available.     

Odor and Fallout Control in a Kraft Pulp Mill

Lead dioxide cylinders are inexpensive sampling devices commonly used for an assessment of sulfur oxides in the atmosphere. This paper will report the results of basic studies intended to characterize some of the critical parameters of this method. The behavior of the system in the region of the critical loading percentages was determined as well as the effects of lead dioxide particle size, presence of reduced sulfur compounds, and use of different binders. From these studies it has been possible to show a definite relationship between allowable exposure times and atmospheric concentrations of sulfur dioxide with particle size as a major parameter     

An Example of Planning for Pollution Control in Kraft Pulping

Two factors have contributed to the preparation of this paper. The first stemmed from Morton Sterling’s remarks in his address to the Houston Meeting. Therein he suggested the value of industry making public the progress made in overcoming pollution problems. Interest in Kraft Pulping Pollution problems on a wider scale constituted the second factor. This is well illustrated by the U.S.P.H.S. annotated bibliography, “Air Pollution and the Kraft Pulping Industry.” This paper will not contribute any new technology. It will, however, indicate how an established plant, in a large urban area, has planned and taken action to solve a pollution problem. Planning in this situation is used in a broad sense. It includes education and training of personnel, changes in process, capital expenditure and new installations, constant attention to maintenance and control, utilization of research and development from all sources, and relations with the public and regulatory agencies.     

Toxic by-products from the combustion of Kraft lignin

Lignin samples, sub-product in the Kraft process of cellulose from eucalyptus wood, were burnt in a laboratory scale furnace at different residence temperatures and with distinct fuel-rich atmospheres. The yields of CO, CO(2), eight light hydrocarbons (methane, ethylene, ethane, propylene, acetylene, butane, etc.) and 60 semi-volatile+volatile compounds (benzene, toluene, ethylbenzene, styrene, indene, naphthalene, dibenzofuran, phenanthrene, chrysene, etc.) were determined, with nominal reactor temperatures between 800 and 1100 degrees C and residence times of the volatiles evolved and formed between 4 and 7 s. The collection of the gases and volatiles evolved was carried out with a Tedlar bag and by XAD-4 resin respectively, comparing the data obtained in both cases. The emission factor (mg/kg) of the CO was between 2500 and 90000, and under the poor-oxygen atmosphere, the emission factors of many by-toxic products were greater than 100 mg/kg. A pyrolysis run was also performed, obtaining emission factors between 30 and 3000 mg/kg, facilitating its identification. The behaviour of different compounds in the combustion runs was discussed considering three groups in accordance with their stability vs. oxygen, and two groups vs. temperature.     

Characterisation of non-condensable sulphur containing gases from Kraft pulp mills

This paper describes work performed on the sampling and analysis of non-condensable gases (NCG) emitted from diffuse sources of a Portuguese Kraft pulp mill, which is the background information for a NCG collection, treatment and disposal system. The variability found in the composition of the gaseous compounds showed the existence of gaseous streams other than typical total reduced sulphur (TRS) compounds as usually described. From the measured TRS concentrations and the gas flow rate from each source it was possible to calculate the emission flow rate, E, of each source. These emission flow rates were then divided into three categories which are quite useful to identify significant sources and to choose abatement techniques. The methodology presented allows for a precise quantification of sources so that similar emissions can be grouped for treatment purposes. Sources with an emission flow rate bigger than 1 kg/h have a marked effect on the overall TRS emissions of the mill, as they are major contributors. It was also found that a new analytical procedure using Restek columns is more easy to use and overcomes operational problems noticed previously, namely a run time of 20-25 min instead of 50-60 min.     

膜萃取技术回收浓缩废水中的邻甲苯胺

采用均质硅橡胶膜构建了卷绕式膜组件,以盐酸溶液为萃取液回收浓缩废水中的邻甲苯胺。通过考察进水浓度、萃取液pH、温度、离子强度、进水流速等因素对去除过程及回收率的影响,探讨了采用膜萃取技术回收浓缩邻甲苯胺的条件与机制。结果表明:膜萃取技术可以将2 g/L的邻甲苯胺废水浓缩至约10 g/L,且随着料液浓度增加,邻甲苯胺回收率先增后降,过高的邻甲苯胺浓度可能会造成膜选择性下降;萃取液pH是影响回收率的重要因素之一,1≤pH≤2时污染物回收率高于95%;无机盐离子可以促进邻甲苯胺的回收,当盐离子含量超过10%时,回收率显著提高;进水流速在2~20 mL/min之间变化时,回收率先增后降,膜阻和解吸速率依次成为主要影响因素。该实验研究表明,膜萃取技术可以高效节能地的浓缩回收生产废水中的邻甲苯胺。     

Emission Control in Coking Operations By Use of Stage Charging

At the Clairton Coke Works of the United States Steel Corporation (the world’s largest coke plant), with coal charges of about 30,000 net tons per day, a system designated as “stage charging” has been developed for charging coal into the coke oven chamber without emissions to the atmosphere. The principles of the system are based on controlled sequential flow of the coal from the charging hoppers, during which the oven chamber is maintained under a very slight negative pressure condition by use of steam aspiration in the offtakes for on-the-main charging. The techniques are basic but require knowledge of the coal characteristics, adequate and properly maintained aspirating systems, including clean offtake piping, control of coal volume in the individual hoppers, and last, and probably most important, adherence by the operating crew to specific charging and leveling practices.     

絮凝法回收印染废水中的聚乙烯醇

采用絮凝法以硼酸为絮凝剂,硫酸同氢氧化钠反应形成的硫酸钠为盐析剂,对含聚乙烯醇的印染废水进行回收处理。通过检测絮凝后溶液中聚乙烯醇含量分析了硼酸投加量、硫酸投加量、温度和pH值等因素对其回收率的影响。结果表明,当硼酸投加量为0.5 g,硫酸投加量为5 mL,pH值为9,温度为50℃时,聚乙烯醇的回收率可达98.6%,且COD去除率为93%。     

Elimination of VOC Emissions from Surface Coating Operations

Collectively, surface coating operations using paints with hydrocarbon solvents may well be the largest industrial source of volatile organic compounds (VOC) and hazardous air pollutants (HAP). Most surface coating operations involve the manual application of paint with spray equipment inside a paint spray booth. The booth exhaust system collects the solvent fumes and then exhausts them through a stack to the atmosphere. Stack emissions are characteristically high in flow rate and low in concentration. Since control equipment is sized based on exhaust flow rate rather than concentration, control of VOC and HAP requires large, expansive abatement equipment. Simple, effective designs employing recycling of air have greatly reduced the exhaust flow rate and the cost of the control equipment. However, these designs are not popular because they are burdened by various flaws, notably worker endangerment. The Mobile Zone recirculation system can be incorporated into new construction or retrofitted to existing spray booths and will reduce the exhaust volumes ranging from 65 to 95 percent without adversely affecting the production rate, production quality or worker safety.     

润滑油废白土的热解处理

以润滑油废白土为原料,利用电热解法,研究了热解终温、加热速率和CaO添加量对热解产物的影响。实验结果表明:热解终温对热解产物的影响最为显著。随着热解终温的升高,不凝气产量和产油率均迅速增加。当热解终温达到600℃时,其增加的速率逐渐缓慢增大。当控制热解终温为800℃、加热速率为16℃/min、CaO添加量为0.5%时,富氢气体产量为189.2 L/kg,气体中主要成分为H2和CH4,其含量分别为27.97%和41.64%;热解残渣含油率和重金属溶出物均低于标准规定值,热解油产率为10.98%,回收率为38.94%,其主要成分为汽油、柴油和重油3部分组成,分别含19.13%、31.35%和49.52%。     

造纸黑液酸析法回收木质素

研究了加酸沉淀回收碱法草浆黑液中木质素的工艺,探讨了酸浓度,温度,ｐＨ值及加酸速度对木质素回收量的影响,得出的最佳条件是：硫酸浓度为５０％,温度为４０℃￣５０℃,ｐＨ值为３．０左右,加酸速度以控制不使产生大量泡沫为准。在上述条件下,木质素的回收效果最佳。     

多效膜蒸馏技术浓缩回收废水中的二甲基亚砜

利用具有内部潜热回收功能的气隙式多效膜蒸馏(MEMD)组件对含二甲基亚砜(DMSO)的化纤废水进行了浓缩回收研究,考察了料液中DMSO浓度、进料流量、进料温度和膜侧进口温度对膜通量、造水比、分离因子和回收率的影响。结果表明,多效膜蒸馏可以将DMSO废水浓缩至200~300 g/L;初始浓度为6.2 g/L时,造水比和分离因子最高值分别为12.4和76.0;虽然膜通量、造水比和分离因子均随料液浓度增大而下降,但是当DMSO浓度达到200 g/L时,膜通量、造水比、分离因子仍分别高达3.74 L/(m2·h)、7.1、32.1;在整个浓缩过程中,回收率维持在99.6%以上;当DMSO废水浓缩达到150 g/L以上时,含有少量DMSO的渗透液可作为二次料液继续用MEMD过程浓缩。膜组件在连续运行的1个月内保持了良好的操作性能。该实验研究表明,多效膜蒸馏过程可以高效节能地浓缩回收化纤废水中的DMSO。