Practical applications and optimum gas flowrate for maximum power saving
Drag reduction offers the possibility of lowering both the pressure drop and the
power requirements in slurry pipelines. Air injection can be used, in practice,
in two ways:
(i) To reduce the pressure drop, and hence the upstream pressure in a
pipeline, for a given flow rate of shear-thinning liquid.
(ii) To increase the throughput of liquid for a given value of pressure drop.
4.2.6
Air injection can also be beneficial because it may be easier to re-start pumping
after a shutdown as the pipe will not be completely full of slurry. On the other
hand, if the pipeline follows an undulating topography, difficulties can arise
from air collecting at the high points.
Air injection may sometimes be an alternative to deflocculation before
pumping. In general, less power is required to pump deflocculated slurries
but highly consolidated sediments may form on shutdown and these may be
difficult to resuspend when pumping is resumed. Furthermore, deflocculating
agents are expensive and may be undesirable contaminants of the product.
However, additional energy will be required to compress the air to a pressure
in excess of the upstream pressure. Thus, the circumstances under which
there will be a net saving of power for pumping will be strongly dependent
on the relative efficiences of the slurry pump and the gas compressor, and on
the specific plant layout. Dziubinski and Richardson [1985] have addressed
this problem and the salient features of their study are summarised here. They
introduced a power saving coefficient, , defined as
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
|