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确定细粉料密相气力输送能力通常要比确定其稀相输送的更难,有望在一开始就能正确评估粉料是采用密相还是稀相输送,只需利用某种形式的预测准则而不必对该粉料进行气力输送试验。早就认识到有两类宽范畴的密相流能有效用于气力输送系统,其一主要是显示高度透气性颗粒料的密相输送(栓流),其二是主要基于细粉流态化本质的流动(流态化密相流)。颗粒料密相流本质上是被空气间隙分隔的满管径物料输送,细粉料密相流则是物料通常被分成两层流动,即在管底流动的密相层和在上层流动的稀相层。不同的气力输送分类图采用了各种各样的粒子和散料参数,力图精确预测散料密相输送的潜力,这些图中采用的参数包括了从粒径大小、粒子密度、堆积密度等基本粒子性能到基于流态化和去气行为等较复杂的空气—粒子性能。不同的研究者用于确定按流动模式预测的不同粒子和堆积参数间关系的方法很不相同,对照已知的散料“流动模式”能力,描述了每位研究者的方法,并对他们的流动模式预测特性做出评价。当需要流体(或气体)的性能(密度、黏度、温度)时,与空气有关的数值采用在标准大气压条件下的。
Determining the dense-phase pneumatic conveying capability of fines is generally more difficult than determining the transport of the lean phase and is expected from the outset to correctly estimate whether the fines are transported in either dense or dilute phase using only some form of prediction criterion It is not necessary to carry out the pneumatic conveying test on the powder. It has long been recognized that there are two broad categories of dense phase streams that can be effectively used in pneumatic conveying systems, one mainly for the dense phase transport (bolting) of highly breathable pellets and the second based mainly on the fine powder fluidization Essential flow (fluidized dense phase flow). Particulate dense phase flow is essentially the full diameter of the material separated by the air gap material delivery, fine powder dense phase flow is the material is usually divided into two layers flow, that is, in the bottom of the flow of dense phase and the flow of thin Phase. The different pneumatic conveying classifications use a wide range of particle and bulk parameters in an effort to accurately predict the potential for dense phase bulk flow. Parameters used in these plots include basic particle size, particle density, bulk density, etc. Particle performance is based on the more complex air-particle properties such as fluidization and de-aeration behavior. The methods used by different researchers to determine the relationship between the different particle-by-particle parameters predicted by the flow pattern are very different, describing each researcher’s method against the known bulk “flow pattern” Their flow pattern predictive characteristics are evaluated. When fluid (or gas) properties (density, viscosity, temperature) are required, air-related values are used at standard atmospheric pressure.