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PROJECT OVERVIEW
The Potash Company of Saskatchewan switched to solution mining in the late
1980's as a result of being unable to contain or dewater their flooded mining
operation. In the early stages of solution mining, they were able to
maintain a reasonable potash extraction rate until they started to exhaust the
heat sink in the earth materials located in the mine. In essence, the heated barren
solution had to be pumped down through the mine and returned pregnant to the
surface. The pregnant potash solution would precipitate in the surface lakes
when exposed to subzero temperatures during the winter months, hence the mine
only operated during the winter months.
In order to save the mine, a novel form of brine solution heating had to be
considered, and Subcom solution heating was piloted and proven as the most suitable
application.
THE CHALLENGE
The challenge was to investigate the possibility of adapting Subcom solution
heating to heat the corrosive brine solution.
Inproheat initially performed a series of metallurgical test in order to
determine the most suitable alloy choice for the construction of the combustion components.
The criteria required an alloy choice that would stand up to stress corrosion
cracking resulting from exposure at high temperatures in the presence of
chlorides.
Time at temperature tests concluded that Duplex 2204 & 2205 as most suitable
alloys to withstand the harsh environment.
THE SOLUTION
With suitable alloy choices confirmed, construction began on ten (10) 13 MM
Btu/hr Subcom Solution heating system, providing a total heat input of 130 MM
Btu/hr. The system comprised of mounting the ten Subcom burners onto a floating
tank structure. A specific channel was formed to direct the 15,000 USGPM brine
flow rate directly under the Subcom Burners. The burners elevated the brine
solution some 15 to 20º C, providing a thermal heating efficiency of 98%.
This novel application has been in operation since 1990, and as a result of such
outstanding performance, PCS was issued the 1991 award from CGA for "innovative
use of natural gas".
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