Particle Size Estimation from Pressure Drops of a Pneumatic Conveying Pipe Line

Size measurement of solid particles has been generally performed for a test sample. In such a conventional measurement, however, it is time-consumable and not easy to get test samples from a process line. A method of particle size estimation from pressure drops of a pneumatic conveying pipe line is herein discussed for the flow of Newton's region. According to the previous report'), pressure drops of a pneumatic conveying pipe line have been able to be calculated theoretically using empirical values of λs and vt, i.e. friction factor of solid flow through a pipe and mean settling velocity of solid particles respectively. In this paper, λs and vt are obtained from the relations between solid-gas mixture ratio and pressure drops of an accelerating and a constant velocity sections, where the accelerating section has to start at the position of ν=0 such as the feed point of solid particles. Then the mean particle size equivalent to a sphere is calculated from νt, and shows good agreement with experimental results

Dynamic Characteristics of a Pneumatic Conveying Pipe Line

Measurement and control of the solid-gas mixture ratio in two phase flow were reported in the previous papers using a solid-gas two phase flowmeter1-25. However, dynamic characteristics of a pneumatic conveying pipe line could not be discussed because of large time-lags of primary means, manipulating device, etc. In this paper, therefore, pressure measuring elements having small time-lags are used and pressure changes are taken as photographs by use of a synchro-scope. Then, dynamic responses of pressure in a pneumatic conveying pipe line are discussed for a step change of flow rates of air and solids respectively. It is concluded that time-lags of the pressure responses can be neglected for change of air flow rate alone. There is a relation between pressure P and volumetric flow rate of air V as follows; where Z" and z* are impedances of a pipe line for air and solid flow respectively. The experiment shows that Z" is a constant irrespective of air flow rate, and that Zs is proportional to the hold-up of solids in a pipe line

EU, NAFTA, and Asian Responses: A Perspective from the Calculus of Participation

This paper assesses the economic conditions for Asian countries to cope with the formation of EU and NAFTA. Is it desirable for them to form their own trading area? And, if desirable, is it better to have a closed one like the EAEC or a more open one like the APEC? Relying on public economics and the calculus of participation combined with the Dixit-Stiglitz-Krugman framework, we find the following: (i) the development of the EAEC by the leadership of Malaysia would be a natural response of Asian countries against two big blocs in the world, EU and NAFTA; (ii) it is natural for the United States to discourage this move because the formation of an economic bloc in Asia will have a negative economic impact on the non- Asian countries; (iii) it is natural for the U.S. to propose an opposing coalition like the APEC to nullify the possible economic impact of the EAEC; but (iv) perhaps the APEC will be a good roundabout way towards international free trade.

Chemical Vapor-Deposited Amorphous Silicon Nitride

Chemical vapor-deposited amorphous Si_3N_4 (CVD-amorphous Si_3N_4) up to 4.2mm in thickness has been prepared from a gaseous mixture of NH_3 and H_2-carried SiCl_4 under various deposition conditions. The formation of the CVD-amorphous Si_3N_4 depended strongly on the deposition temperature, total gas pressure and gas flow rate. The CVD-amorphous Si_3N_4 prepared at 1100-1300℃ does not crystallize by heating at each deposition temperature. Their density and deposition rate are markedly dependent on deposition conditions and have maximum values of 3.00g/cm^3 (94% of the theoretical density of α-Si_3N_4) and 0.36mm/hr, respectively. The Vickers microhardness of the CVD-amorphous Si_3N_4 at room temperature varies between 2200 and 3200kg/mm^2 according to its deposition conditions. The hardness at 1300℃ is 1200～1300 kg/mm^2. The thermal conductivity was 0.010cal/cm/sec/℃ at 20℃ and 0.012cal/cm/sec/℃ at 1300℃. The thermal expansion coefficient at 20～1200℃ is 2.99±0.05/℃. The formation mechanism and the effect of gas flow patterns on the deposition rate of the CVD-amorphous Si_3N_4 are also discussed