WSP00132

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1980
• Title: Use of Saline Water in Energy Development
• Water Supply Pro - Doc Type: Report/Study

where

Q

rate of heat rejection from the
1,000 MWe power plant, operating
at 40 percent thermal ef-
ficiency. Thia ia

(1-0.4n) = 1500 MWe=5.12x109Btu/hr.
0.40
(2)

Co.)
~
Co.)
-..J

Q = 1000 MWe

Ml

mass flow rate of water entering
the tower.

M2

mass flow rate of water leaving
the tower.

hfl

apecific enth.alpy of circulating
water entering the tower.

hf2 apecific enthalpy of circulating
water leaving the tower.

Temperatures of water entering and leaving
the cooling tower are assumed to be Tl .
l100F (43,30C) and T2 = 800F (26.70C).

The evaporation flow rate was estimated
from the literature (Caplan 1975; Kunz et al.
1977) aa 1 percent of the circulating water
flow rate for each ten degree reduction in
temperature (OF), giving:

Mevap = 0,01 MI (TI - T2)/10 = 0,001 MI (TI- T2)
. , , ' ' (3)

Drift 1088 is taken as 0.1 percent of circu-
lation (Caplan 1975)

Mdrift = 0.001 HI

(4)

A tnass balance for the water may thus be
wr {tten as,

+ I Blowdown I

I Makeup I =
M =M +M +M.
mu drift evap . bd

+

(5)

A mass balance for the salt is similarly
expressed as

Makeup
Salt

Drif t
Salt

Blowdown
Salt

+

MmuCmu = MdriftCcir + ~dCbd

(6)

wh~re

Cmu salt concentration of makeup
water.

Cclr IIIl salt concentration of circu-
lating water.
Cbd ... salt concentration of blowdown
water.

Also, another mass balance for the water
through the cooling tower is written 8S

Water
Leaving
the
Tower

Water
Entering
the
Tower

Drift
Loss

Evaporation
Loss

M2 = M1 - M - M
drift evap

(7)

The above equations and assumptions
provide sufficient information to calculate
makeup and blowdown water requirements as a
function of their salt concentrations for the
cooling option (called option 1 and depicted
in Figure 35) in which no water treatment
other than biocide is specified. Results are
ahown~in Table 7,

~s may be expected the required quan-
tities- of makeup and blowdown waters increase
a igniflcantly as the salinity of the makeup
water \ 'increases. For example, with the
maximum allowable TDS of the circulating
",ater set at 8,000 mg/l, increasing the TDS
of the makeup water from 1,000 mg/l to 2,000
mg!l increases the makeup water by 17 percent
and the blowdown water to be disposed
of by 174 percent. An increase in the TDS of
the makeup water from 6,000 mg/l to 7,000
mg!! increases the makeup water requirement
by 100 percent and the blowdown by 135
percent. The results plotted in Figures 17
and 18 emphasize the nonlinearity of the im-
pact of makeup water salinity on the annual
volumes of makeup water which must be ob-
tained, and blowdown water which must be
diacharged. The maximum allowable salinity
of the circulating water also has an impor-
tant impact and is largely determined by the
design and selection of material in the
cooling loop syatem.

The Brine Evaporation Pond

Even though possibilities exist to
concentrate the brine before it leaves the
plant and to utilize the briny blowdown
waters for such purposes as ash quenching "and
stack gas scrubbing, very substantial quan-
tities of blowdown waters must be disposed
of, and the amount increases with the sa-
linity of the makeup water as shown in Figure
18. One option for blowdown disposal is the
evaporation pond, wherein sunshine evaporates
the water leaving the minerals behind in a
hopefully impervious basin, This section of
the study predicts the required evaporation
pond area as a function of the salinity of

18