Page 165 - Petroleum and Gas Field Processing

Because of the above drawbacks, it is generally recommended to
avoid using heating as a treatment process if at all possible. Otherwise,
some of the benefits of heating may be realized with the minimum amount
of heating.

5.4.2 Methods of Heating Oil Emulsions
The fuel used to supply heat in oil-treating operations is practically natural
gas. Under some special conditions, crude oil may be used.
Heaters are generally of two basic types:
1. Direct heaters, in which oil is passed through a coil exposed to
the hot flue gases of the burned fuel or to introduce the emulsion
into a vessel heated using a fire tube heater.
2. Indirect heaters, in which heat is transferred from the hot flue
gases to the emulsion via water as a transfer medium. The
emulsion passes through tubes immersed in a hot water bath.
In general, the amount of free water in the oil emulsion will be a
factor in determining which method is to be used. If free water is found to
be 1–2%, then use an indirect heater. If the free-water content is more
enough to hold a level around the fire tube, then use a direct heater. Both
types are shown in Figure 10.

5.4.3 Heat Requirement
The amount of heat transferred to, or gained by, a fluid is generally
given by

q ¼ mc T Btu=h ð4Þ
where q is the rate of heat transferred/gained (Btu/h), m is the mass flow

rate of fluid (lb/h), c is the specific heat of fluid (Btu/lb- F), and T is the

increase in temperature due to heat transferred ( F).
The mass flow rate, m, could be calculated from the volumetric flow
rate, Q, that is normally given in BPD (bbl/day) as follows:
!
3 3
bbl 1 day ft ft lb
m ¼ Q 5:61 62:4
day 24 h bbl lb h
Therefore,
m ¼ 14:59
Q ffi 15
Q lb=h ð5Þ

where
is the specific gravity of the liquid.

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.