生料辊磨烘干能力的探讨

本文阐明了生料辊磨烘干过程的特征,从传热和供热两个方面探求了生料辊磨烘干能力的计算方法,并从烘干能力和粉磨能力平衡出发分析了可适应的原料水分,以及高水分时对磨机产量的影响。     

降低二氧化钛粗粒子数目的研究

用常规干燥、真空干燥及超临界干燥等方法研究了二氧化钛粗粒子的形成机理。结果表明 ,二氧化钛表面羟基间的脱水反应是形成二氧化钛粗粒子的原因 ,只有通过表面处理把羟基屏蔽起来或用超临界的方法防止干燥时的毛细孔塌陷才能有效地避免二氧化钛粗粒子的生成。对于已生成的二氧化钛粗粒子 ,用不同的加工设备研究了消除二氧化钛粗粒子的方法 ,结果表明砂磨的方法最佳。     

Drying of Activated Sludge Under Partial Vacuum Conditions—An Experimental Study

A typical wastewater treatment system in a pulp and paper mill in Finland treats wastewater both mechanically and biologically. Sludges resulting from these processes have to be disposed of. One possible way of doing this is to incinerate them with solid fuel in the power plant of the mill. To minimize the amount of sludge and to make the use of the sludge energy efficient, it has to be dried before incineration. Mechanical drying of the sludge from biological wastewater treatment is difficult to carry out. Using secondary energies may provide a competitive way of arranging drying: a method of doing this by using partial vacuum evaporation to utilize the low temperature secondary heat in sludge drying is under development. A laboratory study to examine the behavior of activated sludge under partial vacuum evaporation conditions was carried out using a laboratory rotating evaporator to analyze the drying of activated sludge from three mills at 40-80°C boiling temperatures. This article presents the results from the tests. These are promising; it was possible to reach high dry solids content. Also, no boiling point temperature rise was detected, fouling of the evaporator seemed low and easily avoidable, condensate from the evaporator weas relatively clean and returnable to the processes of the mill.     

CFD modeling of MPS coal mill with moisture evaporation

Coal pulverizers play an important role in the functioning and performance of a PC-fired boiler. The main functions of a pulverizer are crushing, drying and separating the fine coal particles toward combustion in the furnace. It is a common experience that mill outlet pipes have unequal coal flow in each pipe and contain some coarse particles. Unequal coal flow translates into unequal air-to-fuel ratio in the burner, deviating from the design value and thus increasing unburned carbon in fly ash, NO_x and CO. Coarser particles at the mill outlet originate from poor separation and decrease the unit efficiency. In addition, coarser particles reduce burner stability at low load. Air flow distribution at the mill throat, as well as inside the mill, significantly influences the mill performance in terms of separation, drying, coal/air flow uniformity at the mill outlet, wear patterns and mill safety. In the present work, a three-dimensional computational fluid dynamics (CFD) model of the MPS Roll Wheel pulverizer at Alliant Energy's Edgewater Unit 5 has been developed. The Eulerian-Lagrangian simulation approach in conjunction with the coal drying model in Fluent, a commercial CFD software package, has been used to conduct the simulation. Coal drying not only changes the primary air temperature but it also increases the primary air flow rate due to mass transfer from coal. Results of the simulation showed that a non-uniform airflow distribution near the throat contributes significantly to non-uniform air-coal flow at the outlet. It was shown that uniform velocity at the throat improves the air and coal flow distribution at the outlet pipes. A newly developed coal mill model provides a valuable tool that can be used to improve the pulverizer design and optimize unit operation. For example, reject coal rate, which is controlled by the air flow near the mill throat, can be reduced. The model can also be used to further aid in identifying and reducing high temperature or coal-rich areas where mill fires are most likely to start.     

超剪切在沉淀白炭黑分散细化中的研究

二氧化硅是高比表面积的粉体物料,在水中形成极易团聚的沉淀白炭黑。为全面提高其分散性,使其平均粒径达到2—5μm,利用最新的超剪切技术,对沉淀白炭黑进行分散细化处理,研究了基于超剪切过程的原理和方法,并通过响应面实验对沉淀白炭黑进行了分散细化实验研究,结果表明超剪切技术对易团聚、难分散的液固态物料的分散细化具有极佳的效果。     

Drying of Activated Sludge Under Partial Vacuum Conditions—An Experimental Study

Abstract

A typical wastewater treatment system in a pulp and paper mill in Finland treats wastewater both mechanically and biologically. Sludges resulting from these processes have to be disposed of. One possible way of doing this is to incinerate them with solid fuel in the power plant of the mill. To minimize the amount of sludge and to make the use of the sludge energy efficient, it has to be dried before incineration. Mechanical drying of the sludge from biological wastewater treatment is difficult to carry out. Using secondary energies may provide a competitive way of arranging drying: a method of doing this by using partial vacuum evaporation to utilize the low temperature secondary heat in sludge drying is under development. A laboratory study to examine the behavior of activated sludge under partial vacuum evaporation conditions was carried out using a laboratory rotating evaporator to analyze the drying of activated sludge from three mills at 40–80°C boiling temperatures. This article presents the results from the tests. These are promising; it was possible to reach high dry solids content. Also, no boiling point temperature rise was detected, fouling of the evaporator seemed low and easily avoidable, condensate from the evaporator weas relatively clean and returnable to the processes of the mill.     

Gesamtkonzept zur Glucosinolatbestimmung — Möglichkeiten zur Erstellung von Bilanzen in Rapssamen und -schroten

A New Concept for the Determination of Total Glucosinolate Content — Possibilities to Draw up Balances in Rapeseed and Rapeseed Meal The indirect analysis of the original total glucosinolate content of rapeseed and rapeseed meal via the determination of released sulfate anion is an interesting alternative to the other methods. While the total sulfate content always represents the total glucosinolate content at the time of harvest, the amount of decomposed glucosinolates in the seeds or meals is represented by the amount of free sulfate. In this way a balance can be made between rapeseed harvest or rapeseed entering the oil mill and rapeseed meal leaving the oil mill. Oil milling processes always lead to a partial degradation of glucosinolates and the resulting meal will contain a variable portion of the original intact glucosinolates. Glucosinolates are hydrolysed during drying, analysing or processing either enzymatically by the action of myrosinase or thermally by the action of heat. In both cases one molecule sulfate is produced from one molecule glucosinolate. With the aid of the sulfate method it is therefore possible to draw up balances especially in rapeseed meal.     

Combined grinding and drying of refractory clays in a shaft mill

Conclusions The shaft mill is suitable for combined grinding and drying of refractory clays with different moisture contents, including frozen clays.The product of combined grinding and drying in a shaft mill, in regard to grain-size composition and moisture content, corresponds to the technological norms. The grain-size composition and moisture content of the power are easily regulated.Operating costs with combined grinding and drying of refractory clays in a shaft mill are about 25% less than when drying in a drying drum and grinding in a disintegrator.The dimensions and capital costs of the installation with a shaft mill are less than for a unit with a drying drum and disintegrator.     

Drying of a Porous Material in a Pulsed Fluid Bed Dryer: The Influences of Temperature,Frequency of Pulsation,and Air Flow Rate

In this work, a four-section pulsed fluid bed apparatus with a 0.18 m² cross-section area was used to investigate the influence of pulsed-fluidization variables on the drying process of molecular sieves, a test material that was chosen because it presents an initial constant drying rate period. A two-level factorial design was developed to evaluate the influences of the inlet gas temperature—40 and 70°C—the frequency of pulsation—250 and 900 rpm—and the air flow rate—500 and 600 m³(STP)/h—on the drying rate. In addition, a comparison was made between the drying rates achieved with conventional and pulsed fluidization. Results showed that all the investigated variables affect the drying rate. Moreover, drying rates with conventional fluidization are considerably higher, which shows that one must expect a lower drying rate when pulsation is used in a drying process controlled by the external evaporation. Concerning fluid dynamics, this work also analyzed the influence of the frequency of pulsation on the pressure drop across the bed. The higher the frequency, the higher the pressure drop. That result can be explained by the reduction of channeling.     

Drying,storage, and preparation of copra for extraction of oil

Various methods are used in drying copra. Because of costs, fuel oil and electricity are avoided by copra producers. Sun-drying remains as a cheap practical way of drying. Direct drying kilns rely on direct contact of combustion gases with coconut meat and produce a generally inferior grade of copra. Indirect drying kilns produce excellent copra. Various preparatory equipment may be used satisfactorily. A new copra oil mill will be most economically designed for handling copra as the main raw material. If, however, an existing oil mill is to diversify to include copra as new raw material, only minor equipment changes are needed. By 1980, copra will almost disappear as an export item, because the coconut producing countries will press and extract coconut oil domestically. The coconut-producing countries hope to obtain better quality of products, improve profit, and contribute to local economy by using local resources.     

水泥预粉磨及其相关问题探析

设法降低粉磨电耗是水泥工业节能、减排、提效之关键,针对目前水泥终粉磨仍然是球磨机占绝对优势的现状,采用预粉磨技术则是最有效措施。简要介绍了水泥预粉磨装备的分类和目前各类预粉磨系统的技术指标(比表面积)情况;重点进行了国产和洪堡辊压机及CKP立磨这三种设备的预粉磨功率投入、预粉磨压力及预粉磨成品比面积的对比与分析。作者认为,可用预粉磨配置功率能效转换指数的大小来评价预粉磨的效益;预粉磨比表面积控制在180m2/kg左右比较科学,是最佳的选择;CKP立磨的预粉磨能效转换指数是辊压机的2倍多,应当是目前预粉磨装备的最好选择。     

Mathematical model of drying in a brown coal mill system. 1. Formulation of model

Brown coals, because of their high as-mined moisture contents, are dried as they are transported through the drying system of a power station mill, by hot gas taken from the boiler combustion chamber. In this paper, a mathematical model of the drying process that occurs in this system is developed and tested. In the first part of the paper, drying experiments on single coal particles in hot gas streams are described and a model of the drying of a single particle is developed. From the single-particle study, a rate equation is obtained which is used in the formulation of a model of the mill drying process. The basic assumptions necessary for the development of the drying-process model are discussed. Modifications to a simple model are proposed to account more realistically for gas-particle interactions.     

HP磨煤机磨制高水分印尼煤选型

根据高水分印尼煤的煤质特点,分析了HP磨煤机磨制高水分印尼煤时的技术特点,从研磨出力和干燥出力角度出发,详细论述了HP磨煤机的选型方法。通过实际工程HP磨煤机选型实践,得出HP磨煤机可以磨制收到基水分高达40%的印尼煤,研磨出力和干燥出力均能满足设计要求。     

稻草秸秆综纤维素对阿司匹林片崩解性能的影响

以稻草秸秆为原料,经过SO₃微热爆预处理、木质素降解、漂白等工序制备出了稻草秸秆综纤维素,并将其用作片剂崩解剂进行了性能评价。参照《中国药典》(2015版)中的有关规定,检测了稻草秸秆综纤维素的各项指标;以阿司匹林为模型药物,以市售微晶纤维素为对照,测定了稻草秸秆综纤维素的崩解性能。结果表明,稻草秸秆综纤维素质量符合《中国药典》(2015版)中的相关规定,且崩解性明显优于市售微晶纤维素,可用作片剂崩解剂。在稻草秸秆综纤维素用量为3％~5%时即可达到微晶纤维素用量为15%~20%的崩解效果,这一效果的呈现与稻草秸秆综纤维素的形态结构以及含有半纤维素组分有着密切联系。     

Möglichkeiten zum Nachweis einer Hitzeeinwirkung auf Rapssaat im Zusammenhang mit Glucosinolat-Bestimmungsmethoden

Ways to Detect Heat Exposure of Rapeseed in Relation to Glucosinolate Determination In wet summers rapeseed lots may have to be dried during harvesting by the action of hot air prior to storage in a silo. In the laboratory, samples for analysis must often be dried because rapeseed with a higher degree of humidity can be difficult to grind or mill. In some laboratory protocols, the ise of microwave ovens is recommended. When rapeseed is heated, components can be chemically transformed in such a way that they are no longer accessible to analysis methods designed for the original parent compound. This is also the case with glucosinolates and some of their analysis methods, particularly when microwave drying of samples is used. Discrepancies in glucosinolate results, particularly between the result of a sulfur or sulfate determination on the one hand, and GLC or HPLC of desulfoglucosinolates on the other hand, may have been caused by excessive drying if batches and by the fact that the GLC or HPLC methods in use do not determine decomposed glucosinolates. The known thermal decomposition of glucosinolates is particularly evident in 00-rapeseed because of the increased lability of 4-hydroxyglucobrassicin — a prominent 00-rapeseed glucosinolate. It was therefore of interest to find independent methods to detect heat exposure in rapeseed. A number of possibilities are discussed and investigations based on the pattern of chlorophyll degradation products are described. An analysis of the degree of formation of the pyropheophytins a and b permits to decide whether or not a sample of rapeseed had been heated excessively or dried by microwave absorption.     

Energetic Analysis of Drying Biological Materials with High Moisture Content by Using Microwave Energy

One of the most important parameters in the drying process is the efficiency of energy transfer. Although it is well known that the absorbed component of the referred energy in the dehydration process under microwave conditions is theoretically lower—especially during the falling rate period of drying—by an order of magnitude than that of convective drying, the real efficiency of energy transfer in the microwave field depends on numerous—partly unknown—factors. In this study, the most significant relations between the energy transfer efficiency and the drying parameters were investigated. During the experiments, two power levels were used to study the effects of domain variables in apple, potato, and onion dehydration processes. The results showed that variations in microwave power level played an important role in overall drying kinetics.

Based on the recorded data, we determined the typical energy efficiency factors for microwave drying of apple, potato, and onion. The specific energy consumption was calculated to compare the energy efficiency of a single measurement series. It was evident that by applying higher power levels, the energy utilization was more efficient. Furthermore, we theoretically proved and experimentally showed the nonthermal effects of the microwave energy.     

Shell煤气化磨煤干燥系统常见问题分析及解决

阐述Shell煤气化工艺磨煤干燥系统流程,磨煤干燥系统主要设备循环风机和磨煤机进行简介,Shell煤气化磨煤干燥系统试车及运行过程中实际遇到问题的原因浅析及采取相应措施解决问题达到稳定运行目的。     

Influence of Extractives on Bonding Properties of White and Southern Red Oak

White and southern red oak veneers were subjected to four methods of drying followed by five surface treatments. The four drying methods were mill drying at 350°F, laboratory drying at 350 and 212°F, and air drying. The five surface treatments were no treatment, surface scraping, soaking and dipping in 1% NaOH aqueous solution, and water extraction. Plywood panels were prepared by using a phenol-formaldehyde resin.

Even with the best drying-surface treatment combination, wood failure was only 35% for white oak and 39% for southern red oak. Overall, mill drying was the best drying method. Soaking the veneers in 1% NaOH solution significantly increased the bond quality.

Mill drying of veneers caused water-soluble extractives to migrate from the interior portions to veneer and lathe check surfaces. SEM examinations of the glue failure surface revealed that gluelines failed to adhere to the cell walls. Difficulties in bonding white and southern red oak veneers may be caused by extractive contamination.     

BIXIN POWDER PRODUCTION IN CONICAL SPOUTED BED UNITS

Recent work has demonstrated that the red carotenoid bixin is easily extracted from Bixa orellana seeds by particle attrition and impact rather than by solvent extraction. This technique may require a previous step for drying seeds at a safe temperature to preserve pigment quality. A spouted bed (SB) with a draft tube is the most appropriate equipment to process both seed drying and bixin extraction at low operational costs. Operational parameters of the SB unit are optimized as a function of the powder production rate. The maximum air inlet temperature for drying the seeds is also specified. A high performance liquid chromatography method has been developed for the semi-quantitative determination of bixin content in the powder produced. Results show that this SB unit can be more competitive than ball mill equipment.     

Grain Drying in a Paraboloid-Based Spouted Bed with and without Draft Tube

In this study, grain drying in a spherical-based spouted bed (SBSB), a cone-based spouted bed (CBSB), and a paraboloid-based spouted bed (PBSB) with and without draft tube was investigated. Spouted-bed bases with the same volume in different shapes—spherical, cone, and paraboloid—were used for the drying experiments to investigate the effect of the spouted-bed base shape on drying. The drying experiments were carried out with perforated and solid draft tubes. The effects of the distance between the gas inlet nozzle and the bottom of the draft tube (entrainment zone height) and the draft tube diameter as geometric parameters on drying were also investigated. It was seen that the geometrical shape of the contactor base influenced the drying time. The highest drying rate was achieved for drying in a paraboloid-based spouted bed. The results also showed that using a draft tube caused a significant increase in drying time. Because the perforated draft tube allows a higher gas flow rate through the annulus, it decreases the drying time when compared with the solid draft tube. Drying time decreased slightly with the decreasing height of the entrainment zone but draft tube diameter did not have a considerable effect on drying.