Study On The Characteristic Of Lignite Upgrading Through Hot Gas And Microwave Dryness

Coal is the most widely used fossil energy in the world, but as a non-renewable energy,extensive use has led to increasingly scarce of high-quality coal. People gradually turn theirattention to the low-quality coal of lignite, As the reserve of lignite account for40%ofglobal coal, the reserve of lignite is also considerable in China. However, the high-moisture,spontaneous combustion and low calorific value as the disadvantages of lignite affect itsavailable using. After upgraded, the moisture content of the lignite can be reduced that theefficiency of boiler would be improved while a substantial increase of the calorific value ofthe lignite would strengthen the combustion characteristics of coal in the boiler. In thispaper, Several typical domestic lignite were used as objects to study the characteristic ofupgrading under the method of the hot air and microwave.Firstly, according to national standards for industrial analysis of method, five kinds oflignite were measured manually with related equipment, then the results were comparedwith the results through the industry standard analyzer, It was indicating that the measuringerror of the moisture and ash were respectively less than1.165percent and1.369percentwhich was acceptable, measuring error of the volatile which had been regulated within1.1percent. Then calorific values of five kinds of lignite were calculated using the differentempirical formulas and the results were compared to the standard results in the thermalanalyzer to find the best empirical formula.Secondly, a series of studies on the influence factors and mechanism were carried outin the fixed-bed of upgrading with hot air. The study indicated that. the calorific values andrate of moisture removal increased with extension of time and exaltation of the temperatureof hot air, the largest rate of addition between4and8minutes, the maximum rate ofaddition at150℃the Besides, it also increased with the growing of the flow of hot air, inwhich1000ml/min made the most obvious effect, and reduction of the particle size of coal.It showed that the moisture removal led to increasing the calorific value in the processwhile the release of volatile did less effect. Trough the upgrading process, the release of gas which was not steam were CO₂, CO and CH₄and the volume of CH₄was the largest. Thenthe analyzing of physical properties of the samples of upgrading quality lignite showed thatthere is a significant change of coal pore structure and surface morphology.At last, a series of exploratory studies were carried out in the microwave equipment ofupgrading It imported that the upgrading process was general the process of moistureremovals, while volatile was constant. At the same time, conclusion was got that the rate ofmoisture removal increased with exaltation of the power in particular between2and4minutes, grew with reduction of the weight but rate of diversification reduced as the weightbelow9g. The flow of air and granularity of the coal hardly took effect. The same testmethods was took on the coal simples which had been treated under specific conditions.The elevation of calorific value was conspicuous. The process of upgrading took minoreffect on surface morphology of the simples and took less minor on pore structure thanupgrading of hot air.