This document discusses the production and harvesting of salt. It begins by defining salts and describing common salt (sodium chloride). It then describes three main methods for obtaining salt: evaporation from seawater, mining salt from the earth, and creating salt brines. The document focuses on harvesting salt produced through solar evaporation of seawater or brines. It describes the processes of pumping brine, soil stabilization, raking salt layers, and harvesting and washing salt. It discusses mechanizing these operations to reduce costs and increase production.

1. Trivedi Pankti M.
Sem – 3
Roll no – 7
Paper no - 9
Department Of Marine Science
M.K. Bhavnagar University
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2.  The word "salt" is a general chemical term that refers to
ionic compounds formed when an acid reacts with a base.
They may be simple salts such as:-
NaCl, KCl, and Na 2 SO 4 ; acid salts like NaHCO 3 and
NaH 2 PO 4 ; or double salts like KAl(SO 4 ) 2
 Table salt is sodium chloride, a chemical compound with
the formula NaCl. Sodium chloride has been used to flavor
and preserve food for thousands of years.
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3. Crystal structure of sodium chloride
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4.  Salts are formed by a chemical reaction between:
 A base and an acid, e.g., NH3 + HCl → NH4Cl
 A metal and an acid, e.g., Mg + H2SO4 → MgSO4 + H2
 A metal and a non-metal, e.g., Ca + Cl2 → CaCl2
 A base and an acid anhydride, e.g., 2 NaOH + Cl2O →
2 NaClO + H2O
 An acid and a base anhydride, e.g., 2 HNO3 + Na2O →
2 NaNO3 + H2O
Conti..
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5. There are three main methods for obtaining salt:
 Evaporation from sea water
 Mining salt from the earth
 Creating salt brines
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6.  When producing sea salt on an industrial scale, seawater is
placed in large "concentrating ponds" to allow efficient
evaporation from the sun and the wind.
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7.  Rock salt is extracted through dynamite, similar in fashion to
the mining of any other mineral.
 Once it is brought to the Earth's surface, it is crushed and
used for industrial and other non-food purposes.
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8.  While the ocean is a natural salt brine, hydraulic mining (or
solution mining) of salt involves pumping water below the
earth's surface to dissolve salt deposits and create a salt
brine.
 This brine is then pumped to the surface and evaporated to
create salt.
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9.  For effective winning of salt from sea or other inland sources,
the various mechanical and other processes like :
1. Pumping of brine
2. Soil stabilisation
3. Raking of salt layers
4. Harvesting of salt
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Pumping of brine
Stabilisation
of soil in
crystalliser Pan
Raking of Salt layer Harvesting & Washing
of Salt
ConveyingGrindingPacking
Mechanisation in Salt Industry

11.  Normally centrifugal mixed flow or axial
flow pumps are used for pumping of
brine
 The material of construction for pumps
used for pumping sea brine of specific
gravity 1.03 may be usual cast iron
impeller, and 2 % nickel cast iron casing
and suction flare.
 For those used for pumping brine of
higher concentrations the impeller of
bronze and stainless shaft is
recommended.
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12.  In India salt is obtained by solar evaporation of
sea water or sub-soil or lake brine.
 Evaporation of brine is carried out over large
areas and the brine stands on the soil beds for
a long period of time thus there is possibility
of loss of brine by percolation.
 The other danger is the dilution of brine by
upward or lateral infiltration of water or weak
brine which nullifies the effect of evaparation
 Thus impermeability of the soil is only the
protection that is possible.
 This can be achieved by soil stabilisation.
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13.  In inland salt works at Kharaghoda
and kuda, salt is raked regularly
throughout the season after some
ten to fifteen days of its first
deposition in crystallisers.
 Occasionally salt beds are disturb to
increase the crystallization and this
process is recently done by newly
introduce “ Japanese power Tiller”.
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14.  Harvesting of salt is done one a year and
the thickness of the deposit that
determines the stoppage of crystallisation
which is usually 10 to 12 cm.
 The harvesting method used depends
upon several factors like climatic
conditions, nature of soil and its bearing
strength.
 According to Bertrand De Saboulin Bollena
there are three type of salt works
throughout the world which require
different methods for harvesting.
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15.  Here salt is allowed to crystallise in
thin layers and harvested
occassionally.
 Essentially, the crystallisers in this
method are of smaller dimensions
to permit collection of salt by
wooden ‘pawdis’ from the ridges
of the same.
 The method is practiced in salt
works in the states of Maharashtra,
Mysore, Orissa and Andhra.
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16.  Here the harvesting is
carried out at the end of
dry season just before
rains.
 Harvesting is done
mechanically or manually
depending upon bearing
strength of soil bed, size
of crystalliser and
thickness of salt layer.
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17.  Harvesting is done once at the end of dry season or several
times during the season.
 Some times big salt works abandon the salt crop of the first
season and this salt layer works as a salt floor for the next
year crop.
 Though the manual operation works satisfactorily it
deteriorates the quality of salt to some extent.
 In old times salt works in India used to harvest salt manually
but the situation is now changing in India due to rapid
agricultural and industrial development as manual harvesting
is a time consuming process.
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18.  It is therefore , necessary to mechanise these operations, at
least partly, so that the number of laboures required can be
reduced.
 This will help in two ways:
1. By reduction of the cost of production
2. Utilising the extra period available for production of extra
salt.
Conti..
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19.  It consist of two parts :
1. Harvester proper
2. Tractor
 harvester scraps the broken bed of salt.
 The scrapped salt is collected at the collector and conveyed
with the help of mini bucket elevator and discharged
through the hopper which is collected continuously in
trolleys.
 These can be transported from one place to other without
any difficulty.
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20.  This is also done with aid of hydraulic system of the tractor.
 The harvester requires stabilised bed of soil and a salt of at
least 10 to 12 cm.
 The capacity of the harvester is about 20 tonnes per hour.
Conti..
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21.  It is a compact equipment for cutting, lifting and washing of
salt from crystalliser pans.
 It consists of two conveyors, the lower one of which is carried
in a frame.
 At the lower end of the frame there is adjustable salt cutting
blade and salt is cut and lifted by means of upper conveyor
and continuously discharged into trailors.
 The harvester is powered by suitable engine which drives the
harvester, conveyor and trailor.
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22.  The harvester can work in stabilised soil with a salt layer of
10 to 12 cm thick and its capacity is about 10 tonnes/hour.
 This accomplishes about 33% saving in the cost of labour
engaged for harvesting of salt.
Conti..
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23.  For improving the quality of the salt
produced by solar evaporation, washing
is the easiest and cheapest method.
 The soluble impurities (magnesium salts)
can be easily removed along with the
superficially situated insoluble matter
like clay, silica, sand etc and gypsum
impurity.
 Washing can be carried out in many ways
and therefore, the equipments required
will depend upon the quality of raw
common salt used, quality of washed
salt desired and increased price of
washing, the salt can bear.
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24.  Portable conveyor belts moving with
the help of diesel engine or electric
motors for stacking and loading the
barges or trucks are commonly used
in nearly all large salt works.
 Sometime stacking platforms are far
and transportation is done by trollies
hauled by diesel locomotives.
 For well laid out salt works there is a
scope of this transportation being
made by a series of belt conveyors.
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25.  The grinders consists of two
cylindrical rollers rotating in
opposite direction to each
other are used.
 Screening of salt is not
much practicised while
packaging is done by hand
operations.
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Grinding
Packing

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