Jökull - 01.12.1961, Page 63

vacuum evaporators. The present equipment is
too small for an economical operation. Mizu-
tani (G/7) mentions the possibility o£ using geo-
thermal energy for the production of special
types of salt.
(ii) The projectecl salt-plant at Krýsuvik,
Iceland. Lindal (G/27) has, in cooperation with
Dr. M. S. Patel of Bombay, India, and Mr. W. A.
Tobey, Mantistee Engineering Associates, U.
S. A. made a comprehensive study o£ the possi-
bilities of the production of salt front sea-water
by means o£ geothermal energy in Iceland. A
geothermal salt-plant has been projected at
Krysuvik some 30 km south of Reykjavik.
The projected capacity of the plant is 60,000
metric tons/year of salt. Sea-water is to be piped
over a distance of 7 krn and concentrated in
triple-effect vacuum evaporators. The concen-
trated brine flows to a settler where bicarbonates
and calcium sulphate are precipitated. The salt
is to be crystallized in double effect equipment,
dewatered, dried, compacted and briquetted.
The evaporators are to be operated by natural-
steam at pressure of 1.4 to 1.7 atmospheres abs.
The consumption of steam is about 16 units
weight of steam per unit weight of salt. The
estimated total cost of production is 15.23
S/metric ton of salt. Lindal’s cost estimate is
based on a relatively low cost of the natural-
steam. In the view of the present writer, the
total cost is more likely to be about 17.00
|/metric ton of salt. This is above the price o£
imported salt.
Lindal (G/27) consiclers also further process-
ing of sea-water for the production of gypsum
ancl other materials dissolvecl in the sea.
(d) Drying and processing of various materials.
(i) Diatomite. Lindal (G/59) discusses brief-
ly the possibility of using geothermal energy in
tlie recovering and refining of diatomite front
an underwater deposit in Iceland. Natural-
steam at a temperature of 150° C is to be used,
and the consumption of steam appears to be
around 8 units weight of steam per unit weight
of product.
(ii) Alumina. Lindal (G/59) discusses also
the jDossible use of geothermal energy in the
conversion of bauxite to alumina. The possi-
bilities in this field appear rather remote due
to the fact that it is more economical to pro-
duce the alumina at the bauxite-mine.
(III) Grass, seaweeds and peat. The use of
geothermal energy for the drying of these mater-
ials is possible. But the very low transportability
of the raw materials presents the main difficulty.
(iv) Paper, pulp and sugar. The paper and
pulp industry as well as the sugar refining indu-
stry are heavy consumers of heat. The use of
natural-steam is no doubt of advantage in loca-
tions where the raw materials are available in
the vicinity o£ the geothermal resources. One
paper-mill in New Zealand uses natural-steam
as process steam.
(v) Refrigeration and air-conditioning. Ab-
sorption refrigeration systems can be operated
with natural steam. Kerr et al. (G/52) report
that some experimental work has been carried
out in New Zealand in order to study the possi-
ble uses of geothermal energy for this purpost
(6) RECOVERY OF MATERIALS FROM
GEOTHERMAL AREAS.
(a) Geochemist.ry of thermal areas.
Geothermal activitý is caused by an upward
permeation of hot fluids and gases where water
generally is the predominant component. This
water is in most areas of meteoric origin but
there may in some cases, mainly in high-temp-
erature areas, also be some water of juvenile
origin.
The fluids and gases ascend through variable
physical and chemical environment. Tempera-
ture and pressure are high at depth, but de-
crease gradually on the way upward. This leads
to the selective transport of chemical compon-
ents which is of great importance. Sorne com-
ponents are soluble at depth but are precipita-
ted at higher levels.
For example, both silica and calcium carbon-
ate take part in the selective transport. The
solubility of silica increases with increasing
temperature. This component is therefore
dissolved at depth and precipitated near to, or
on, the surface where the temperature of the
fluid drops. The solubility of calcium carbon-
ate depends mainly on the amount of carbon
dioxyde present. This component is also dissol-
ved at depth and is precipitated near to the
surface or in geothermal boreholes.
The behaviour of these two components has
an important effect on the hydrological condi-
tion in thermal areas. The precipitation of silica
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