磨粉机操作技巧

小麦制粉工艺具有较强的连续性,在生产过程中,任何环节只要产生不协调现象,就会影响整个生产。只有良好的设备和合理的工艺流程,没有灵活的正确操作方法去适应现有的设备和工艺。就不可能同时达到质量好、出率高、电耗省和产量高的要求。

Study on the new materials for fiberboard refiner plate of defibrator

Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refiner plates is of significance to the wood industry. It may affect refining quality, production efficiency, and power consumption. In this paper, the abrasion resistance of the refiner plate made of different materials, the stainless steels and high chromium cast irons, were tested and compared. The results showed that abrasion resistance of refiner plate made of high chromium cast irons was better than that of the stainless steel materials. Although the two kinds of materials have the same compositions, their abrasion resistances have ap-parent difference. The main reason is that the material microstructures have very important effects on their performance. The refiner plates made of developed high chromium cast irons don抰 demand the complex heat treatment. This can simplify the producing process, save the cost of production, decrease labor strength, and increase the production efficiency.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.

Semi-autogenous mill power prediction by a hybrid neural genetic algorithm

There are few methods of semi-autogenous(SAG)mill power prediction in the full-scale without using long experiments.In this work,the effects of different operating parameters such as feed moisture,mass flowrate,mill load cell mass,SAG mill solid percentage,inlet and outlet water to the SAG mill and work index are studied.A total number of185full-scale SAG mill works are utilized to develop the artificial neural network(ANN)and the hybrid of ANN and genetic algorithm(GANN)models with relations of input and output data in the full-scale.The results show that the GANN model is more efficient than the ANN model in predicting SAG mill power.The sensitivity analysis was also performed to determine the most effective input parameters on SAG mill power.The sensitivity analysis of the GANN model shows that the work index,inlet water to the SAG mill,mill load cell weight,SAG mill solid percentage,mass flowrate and feed moisture have a direct relationship with mill power,while outlet water to the SAG mill has an inverse relationship with mill power.The results show that the GANN model could be useful to evaluate a good output to changes in input operation parameters.

Breakage and separation mechanism of ZGM coal mill based on parameters optimization model

Sampling ports were firstly drilled on a ZGM95 coal mill in the power plant in China, and the coal samples from various points in the pulverizer were collected under the different operation conditions. The prop- erty of the sampling material from the mill was analyzed, applying the float-sink test, size distribution analysis, proximate analysis and so on. It was indicated that the ＋250 I^m fraction in the pulverized fuel accounted for only 0.02%, while it was 83.2% in the new feed. The circulating ratio and coal flow in the separator and the cone zone were calculated using the mass balance of the circulating load. So, the cir- culating ratio in the separator of the pulverizer was between 8 and 13, and the circulating ratio, the feed flow of separator and cone zone all raised with the increase of the air volume. Furthermore, the parameters of the separation functions were obtained based on the fitting method. It was shown that the mean value of the shape factor B was 0.7617, and the parameter D which is the particle size at 50% cumulative yield in the separator almost kept unchanged.

LOAD DISTRIBUTION ON DRUMS OF DOUBLE DRIVE BELT CONVEYOR

The double drum drive is widely used on the mine belt conveyor, which are divided the rigid connected double drums and separately driving double drums according to connected method of two drums. Because of the change of real work condition, the load distribution is changed on the two drive drums, which may produce a slippage between a drum and belt. Slippage may intensify the wear of the drum, and sometimes causing the fire of the belt. This restricts the development toward narrow belt, high velocity and large power of belt conveyor. In this paper, the factors affecting the load distribution of two drums of double drum belt conveyor are systematically analyzed and some computing formulas derived, by these formulas, the actual lcad distribution on the two drums of rigid connected or separately driving belt conveyor can be separately calculated.These formulas also can be as the theory base for adjusting the driving force of two drums.

Effect of different milling processes on the mineral distribution in a coal powder

Coal samples obtained from Wanbei(WB),Pingxiang(PX),Liupanshui(LP),and Datong(DT) mines were pulverized,using either a vibration mill or a ball mill,to different degrees of fineness.The effect of the different grinding methods on the mineral distribution within the pulverized coal was investigated by using proximate analysis,particle size analysis,and float-sink tests.The results show that the ash content in WB,PX,and DT coal increases with increasing particle size overall,while the ash content of the LP coal remain almost the same within each size fraction.In that case the ash in each fraction is similar to that of the raw coal.The ash versus size distributions for the same coal sample milled with the same grinding method to different degrees of fineness are similar.The ash versus size distribution of the coal powder with a 15% screen residue that was prepared with the vibration mill is different from the distribution of a similar sample prepared with a ball mill.The curves also vary between different coal samples.The grinding method has a great influence on the distribution of minerals across the various particle sizes.The float-sink tests and the laser particle size analysis results on PX and DT coal samples show that fines dominate the higher density fractions although the large +2.0 g/cm3 fraction was dominated by coarse particles.The size distribution of the low density fraction and +2.0 g/cm3 density fraction is bimodal.The size distribution of the intermediate density fraction is multimodal.

Experimental analysis of the mechanism of high-order polygonal wear of wheels of a high-speed train

This paper presents a detailed investigation, via field experiment, into the mechanism of high-order polygonal wear of wheels of a new type of high-speed train. The investigation was carried out during the performance acceptance test of the train and its initial commercial operation. The investigation covered the performance acceptance test of 150 000 km and the commercial operation of about 150 000 km. In the performance acceptance test of the first stage of about 70 000 km, at 200-250 km/h with full loading and sometimes overloading by 30%, the serious polygonal wear of 23-order took place on all the wheels of the train, and was measured and analyzed in detail. All the potygonized wheels were re-profiled because the polygonal wear had caused strong vibration and damage to the train parts. After re-profiling, the vibration of the train and track and the wear status of the wheels were measured and analyzed at different test mileages according to the polygonal wear situation of the wheels. The measured vibration of the train includes the accelerations at different positions of a motor car and a trail car. The vibration modes of the key parts of the bogies of the two cars were calculated. Meanwhile, the track resonant frequencies were investigated at the site. The purpose of the above tests and analysis is try to find the frequency of work mode matching the passing frequency of the high-order wheel polygon. The present investigation shows that one of the working models causes the formation and development of the high-order wheel polygonal wear. The growth of this wear was effectively reduced through the frequent changing of the running speed of the train operating on the way back and forth every day.