Iran Potash Co. (IPC) became the first Iranian producer of the potassium bearing fertiliser mineral, potash in mid-2008, following construction of a plant which started in 1999. Established through government investment, the plant is on a 5,000 hectare site which extracts the brine resources of the Khor playa, located in the Dasht-e Kavir (Great Kavir Basin), in the Yazd province of central Iran.
IPC was set up with the aim of producing 50,000 tpa potash (KCl) locked in carnallite, 300,000 tpa sodium chloride (NaCl), and 30,000 tpa magnesium hydroxide Mg(OH)2.
An investment outlay of about 980,000m. Rials ($98m.) was allocated for the project out of which about 900,000m. Rials ($90m.) has been presently been spent. At full capacity the project will employ 400 to directly operate the plant and 1,000 persons indirectly with associated transportation, processing, and administration costs.
Ali-Akbar Mehrabian Irans minister of industries and mines said: We already require about 300,000 tpa of potassium oxide out of which 50,000 tpa will be supply by this newly operating plant, we have been fully reliant on imported potassium oxide until now.
Through the existing deposits in playa of Khor, he added, I hope we can escalate our production so much that we manage to export the surplus product in future.
IPC is expecting to produce 20,000 tpa potash for 2009 while the company hopes to meet its nominal 50,000 tpa capacity by 2011-2012.
Kahanroba Co. was contracted to carry out the engineering, procurement and construction of the plant, but the main equipment has been provided by European suppliers.
IPC has development plans for expanding its capacity to 70,000 tpa potash, but this depends on finding reliable sources of brine it is eying a similar brine deposit in the north of the Khor playa.
This raises the possibility of a second plant in that area or a feed operation for the existing plant. The company also has development plans for producing magnesia from the brine, in addition to 1.5m. tpa industrial grade salt and 300,000 tpa table salt .
The possibility of high grade dead burned magnesia production has been studied and proved. In this regard, the Basic Engineering for an Mg(OH)2 production plant with a capacity of 30,000 tonnes has been performed, by EAT and KUTEC jointly.
Extracting the brine
To hit the 50,000m. tpa potash the equivalent of 13km² solar ponds have been built of which one third are for potash ponds and two thirds for salt.
Two pipelines with a diameter of 70cm established to transfer brine to the solar ponds with a maximum hourly capacity of 4,000m³. Providing brine from different parts of the playa is achieved through a series of separate channels and several excavated wells.
Precipitation of the salt and potash in the solar ponds is achieved in separate phases and controlled by a series of ponds to concentrate the brine. The salt and potash deposited in the ponds are harvested and transferred to processing plant.
Some of the removed salt is washed at the plant which has a capacity of 300,000 tpa.
Brine collection achieved through a network of open channels and fed by brine wells.
The channel area is 16m² and with a total length of 16km. The brine wells have been excavated deeper than the channels. The lower parts of brine are richer in Mg, Ca, and K than the upper parts, thus the wells are needed for higher quality liquor.
For each well between the depths of 10-13 metres a pump will be placed. The collected brine moves to solar ponds from the pumping station via two 8.8km GFRP Pipeline with a 700mm diameter.
The main pumping station is located in the north of the Khor-Tabas road, which dissects the playa, and has a maximum capacity of 4,000m³/hour; 8 electro-pumps will work in an area of 725m².
High evaporation rates in the Kavir basin and low annual rainfalls are two reasons to use solar ponds for precipitation of salt and potash.
The ponds have been designed considering production of 5,000 tph potash.
The evaporation procedure increases the density and decreases the Na content by precipitation of NaCl in the ponds. When the density reaches 1.340-1.360 ρ the precipitation of potash begins and at the end of the evaporation process, the remaining brine has a density of 1.450 ρ and is high Ca, Mg, N, and Cl. This remaining heavy brine is injected back into the playa.
Harvesting for both salt and potash will be in dry conditions into 10 tonne trucks.
Potash process route
After the delivery of the harvested raw potash, the crystalline crop is to be intermediately stored at a stockpile.
The product is then transported via conveyor belt to milling circuit followed by sieving to under 1mm.
For effective potash production by using the cold crystallisation process, the process is necessary to separate the valuable potash crystals from the NaCl. An NaCl content of 4% is allowed in the feed.
To separate the NaCl from the potash, an inverse flotation process is employed. It means the purified carnallite can be obtained in the flotation process as underflow. Next, the under flow thickening is fed to a decanting centrifuge to separate the crystals from the solution.
Then, purified potash is to fed to the decomposition reactor. Decomposition takes place by using pure water and a leaching solution from the cold leaching process.
The wet product from the centrifuge finally goes to the drying and cooling units. The whole potash plant from intermediate storage to the packaging plant is under contract with the Iranian company, Kahanroba, in co-operation with Lorgy Co. of Germany.
Contributor: Sohrab Mehrabian is an independent journalist specialising in Iran and the Middle East.
Geological setting & brine analysis of the Khor playa
After primary studies in different areas, the Khor playa has been selected as the first choice resource for production of potash in Iran. Exploration work has been previously in the southern, middle and northern areas.
In the central part of Great Kavir, there is a drainage basin that the Khor playa of is part of. Although the basin is the lowest part, the Khor playas location is on a plateau 600-850 metres above sea level. The high altitude, low precipitation conditions with continual replenishing of mineral rich groundwater into the basin are optimum and similar to those seen in the brines of South America.
Around 37% of the Great Kavir Basin is a Mio-Pliocene sedimentary environment. The basin consists of marl and evaporite minerals which are hosted small and large playas, the other regions are covered by alluvial deposits and sand dunes.
The Great Kavir Basin can be divided to three separate parts with the southern basin spanning 2,000 km², extending to near Khor city. The Khor playa from centre to borders can be separated into three zones: the salt crust, moisture zone and clay pan.
Taking into account the porosity of the playas halite body, the brine reserve is about 450m. m.³. The brine contains sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), lithium (Li). No iodine (I) or bromine (Br) has been detected.
The brine has a density of 1.218-1.223 ρ and with maximum rate of 4000m³/h in warm seasons.