Design and Performance Evaluation of a Solar-Assisted Biomass Drying System with Thermal Storage

A solar biomass hybrid air heating system that does not require a conventional auxiliary heater but can still provide a daily load fraction exceeding 90% and supply hot air at a steady temperature and flow rate continuously for 24 h a day has been developed. The system, which combines an unglazed transpired solar collector, rock bed, and a biomass gasifier stove with heat exchanger, was evaluated by drying chilli using air at 60°C and 90 m³/h. The chilli was dried from 76.7% moisture (w.b.) to 8.4% over 32.5 h of continuous drying. The dryer reduced the drying time by 66% compared to open sun drying and provided 91.6% load fraction during the 24-h operation. The temperature of hot air supplied was stable at 60±3°C for about 21 h during the entire drying duration.     

Membrane extraction in rectangular modules with external recycle

The analysis of solvent extraction in the membrane modules of cocurrent, countercurrent and cross-flows with external recycle, has been carried out by mass-transfer theory, analogous to heat transfer in recycled heat exchangers. Considerable improvement is achievable by recycle operation if the increase in mass-transfer coefficient by applying the recycle effect can compensate for the decrease in the driving force of mass transfer due to the dilution of inlet feed solution. Under comparable conditions most solute is extracted in countercurrent-flow arrangement, the least in cocurrent-flow. However, the separation efficiencies of the three flow-type devices approach in unity for lower feed concentration and/or larger flow rate and/or larger reflux ratio.     

Applicability of flashing desalination technique for small scale needs using a novel integrated system coupled with nanofluid-based solar collector

The present study introduces an attempt for the application of flash desalination technique for small scale needs. An integrated system uses a flashing desalination technique coupled with nano-fluid-based solar collector as a heat source has been made to investigate both the effect of different operating modes and that of the variation of functioning parameters and weather conditions on the fresh water production. The flashing unit is performed by similar construction design technique of commercial multi-stage flashing (MSF) plant. The thermal properties of working fluid in the solar collector have been improved by using different concentrated nano-particles. Cu nano-particle is used in the modeling to determine the proper nano-fluid volume fraction that gives higher fresh water productivity. An economic analysis was conducted, since it affects the final cost of produced water, to determine the cost of fresh water production. Although a system may be technically very efficient, it may not be economical. The effect of different feed water and inlet cooling water temperatures on the system performance was studied. The mathematical model is developed to calculate the productivity of the system under different operating conditions. The proposed system gives a reasonable production of fresh water up to 7.7 l/m²/day under the operation conditions. Based on the cost of energy in Egypt, the estimated cost of the generated potable water was 11.68 US$/m³. The efficiency of the system is measured by the gained output ratio (GOR) with day time. The gained output ratio (GOR) of the system reaches 1.058. The current study showed that the solar water heater collecting area is considered a significant factor for reducing the water production cost. Also, the produced water costs decrease with increasing the collecting area of the solar water heater. The volume fractions of nano-particle in solar collector working fluid have a significant impact on increasing the fresh water production and decreasing cost.     

Mathematical modeling of an inclined solar water distillation system

An inclined solar water distillation (ISWD) system, which generates distilled water (i.e., condensate) and hot water at the same time, was modeled and simulated. In the parametric studies, the effects of feed water mass flow rate and solar intensity on the system parameters were investigated. Finally, the system was simulated using actual deviations of solar intensity and environment temperature during a typical summer day in North Cyprus. The system can generate 3.5–5.4 kg (per m² absorber plate area) distilled water during a day (i.e., 7 am till 7 pm). The temperature of the produced hot water reached as high as 60°C, and the average water temperature was about 40°C, which is good enough for domestic use, depending on the type of feed water. The simulation results are in good agreement with the experimental results.     

焦化厂冷鼓工段循环水余热的利用

介绍了利用焦化厂冷鼓工段循环水余热采暖的运行情况,实践表明,不仅可以节省大量蒸汽和循环水,缓解焦化厂蒸汽紧张的局面,而且相应降低了初冷前煤气温度,有利于稳定生产。     

Scientific Principles of Drying Technique (in Russian)B.S. Sazhin and V.B. Sazhin Nauka,Moscow, 1997, 448 pages

ABSTRACT

A novel low cost tray dryer equipped with a solar air collector, a heat storage cabinet and a solar chimney is designed and tested. The design is based on energy balances and on an hourly-averaged radiation data reduction procedure for tilted surfaces. Measurements of total solar radiation on an horizontal plane, ambient temperature and humidity, air speed, temperature and relative humidity inside the dryer as well as solids moisture loss-in-weight data are employed as a means to study the performance of the dryer. First, detailed diagnostic experiments are carried out with no drying material on the trays. Next, a number of experiments is conducted using a controlled reference material whose reproducible dehydration pattern allows comparisons among runs. Drying is also tested during night operation and under adverse weather conditions. For all the employed conditions, the material gets completely dehydrated at a satisfactory rate and with an encouraging system's efficiency.     

DESIGN AND TESTING OF A NEW SOLAR TRAY DRYER

A novel low cost tray dryer equipped with a solar air collector, a heat storage cabinet and a solar chimney is designed and tested. The design is based on energy balances and on an hourly-averaged radiation data reduction procedure for tilted surfaces. Measurements of total solar radiation on an horizontal plane, ambient temperature and humidity, air speed, temperature and relative humidity inside the dryer as well as solids moisture loss-in-weight data are employed as a means to study the performance of the dryer. First, detailed diagnostic experiments are carried out with no drying material on the trays. Next, a number of experiments is conducted using a controlled reference material whose reproducible dehydration pattern allows comparisons among runs. Drying is also tested during night operation and under adverse weather conditions. For all the employed conditions, the material gets completely dehydrated at a satisfactory rate and with an encouraging system's efficiency.     

纳米材料对太阳能集热器应用的影响

以碳纳米管为分散相材料,乙二醇水溶液为分散介质,可制备出用于直接吸收式太阳集热器的新型吸热与传热循环工质～碳纳米管悬浮吸热黑液流体。该黑液流体的分散稳定性主要受到分散介质的组成、碳纳米管粒子的含量、分散剂的属性和含量、分散方式以及分散时间等因素的影响。分散稳定性好的碳纳米管黑液流体的对太阳辐射具有全波段强吸收特性,可以提高集热效率,加入分散剂可使光热转化效率提高12％～15％。     

纳米材料对太阳能集热器应用的影响

以碳纳米管为分散相材料,乙二醇水溶液为分散介质,可制备出用于直接吸收式太阳集热器的新型吸热与传热循环工质-碳纳米管悬浮吸热黑液流体。该黑液流体的分散稳定性主要受到分散介质的组成、碳纳米管粒子的含量、分散剂的属性和含量、分散方式以及分散时间等因素的影响。分散稳定性好的碳纳米管黑液流体的对太阳辐射具有全波段强吸收特性,可以提高集热效率,加入分散剂可使光热转化效率提高12%～15%。     

三聚磷酸钠生产中尾气除尘探讨

我国三聚磷酸钠生产尾气中含尘较多,不仅造成资源浪费、成本升高,并且造成环境污染。作者对国内外几种除尘方式进行分析对比后,着重推荐文丘里除尘或袋式除尘方式取代目前多数企业采用的水膜除尘器,以取得更好的环境和经济效益。     

The drying kinetics of seeded grape in solar dryer with PCM-based solar integrated collector

This paper presents a novel type of dryer for experimentally evaluating the drying kinetics of seeded grapes. In the developed drying system, it has been particularly included an expanded-surface solar air collector, a solar air collector with phase-change material (PCM) and drying room with swirl element. An expanded-surface solar air collector has been used to achieve high heat transfer and turbulence effect whiles a solar air collector with PCM has been used to perform the drying process even after the sunset. On the other hand, the swirl elements have been located to give the swirl effect to air flow in drying room. These advantages make the proposed novel system a promising dryer in that lower moisture value and less drying time. The drying experiments have been carried out simultaneously both under natural conditions and by the dryer with swirl flow and without swirl flow at three different air velocities. The obtained moisture ratio values have been applied to six different moisture ratio models in the literature. The model having the highest correlation coefficient (R) and the lowest Chi-square (χ²) value has been determined as the most relevant one for each seeded grape drying status.     

Water disinfection by solar photocatalysis using compound parabolic collectors

TiO₂ solar photocatalysis has been proven to be a degradation process for aqueous organic contaminant leading to total mineralisation of a large number of compounds. Furthermore, the interest in using this technique for water disinfection has grown in the last decade. Recent publications have reported photokilling of bacteria and viruses by TiO₂ photocatalysis. Therefore, solar photocatalysis disinfection seems to be a very promising process, which could help to improve public health in rural areas of developing countries.

The objective of this work was to assess the feasibility of using TiO₂ solar photocatalysis to disinfect water supplies for future applications in developing countries. This article reviews the viability of solar photocatalysis for disinfection in low cost compound parabolic collectors, using sunlight and titanium dioxide semiconductor, both applied as slurry and supported. We report on the bactericidal action of TiO₂ on a pure culture of Escherichia coli with a low cost photoreactor based on compound parabolic collectors. The influence of different experimental set-ups and parameters are also analysed.

The results and potential application of the solar photocatalysis technology to water disinfection are studied within the frame of two research EU projects whose objective consist on the development of a fully autonomous solar reactor system to purify drinking water in remote locations of developing countries.     

A simple and highly productive solar still: a vertical multiple-effect diffusion-type solar still coupled with a flat-plate mirror

This paper presents a newly designed simple solar still: a vertical multiple-effect diffusion-type solar still consisting of a flat-plate mirror, a number of vertical parallel partitions in contact with saline-soaked wicks with narrow air gaps between partitions, and casters for azimuth tracking by human power. The proposed still is designed so that non-skilled persons can construct it with common materials in developing countries. We theoretically analyzed the dependence of the solar absorption on the first (or heated) partition on the angle of the flat-plate mirror and the azimuth angle of the still, and found that the solar absorption on the first partition can be significantly increased by rotating the still at southing of the sun just once a day, and the daily solar absorption would be about 85% or 99% of the daily solar radiation on a horizontal surface on the spring equinox or winter solstice, respectively. We also theoretically analyzed the heat and mass transfer in the proposed still, and found that a proposed still of 10 partitions with 10 mm diffusion gaps between partitions was predicted to produce 29.2 34.5 kg/m²d on sunny spring equinox and winter solstice days respectively at the equator.     

防爆离心机出湿料的原因分析及消除措施

分析了卧式刮刀自动卸料防爆离心机出现湿料的原因,及消除出现湿料的方法措施。     

250 t/h水泥粉磨系统调试问题及处理

葛洲坝集团水泥公司4500t/d熟料生产线水泥粉磨系统,设计台时产量为250t/h,对该系统调试、投产中出现的O-Sepa选粉机电机与减速机振动过大、水泥粉磨系统袋式收尘器供气不足及其他故障进行说明,并提出具体的解决措施,改进后系统运转良好,满足生产需求。