The varieties of potassium fertilizer produced in China include potassium chloride, potassium sulphate and potassium nitrate, potassium dihydrogen phosphate. Now, the production of potassium fertilizer series products in China has stepped in a period of gradual technology maturity, potash fertilizer production technology can basically meet the needs of potassium fertilizer production by using different types of raw materials, and potash fertilizer industry is starting to soar. According to long-term planning, China potash fertilizer supply will be the formation of domestic product, import, foreign equity accounted for 1/3 of the pattern. Of which the number of potassium sulphate production enterprises are more than 40, potassium nitrate production enterprises are more than 30,and potassium dihydrogen phosphate production enterprises are more than 60 in China. At present in China, the output of potassium sulphate is 3,500kt/a , the output of potassium chloride is 5,300kt/a, the production capacity of potassium dihydrogen phosphate is about 900kt/a, while the production capacity of potassium nitrate for agriculture use is about 400kt/a.
Potassium chloride is a main variety of potassium fertilizer, other potassium fertilizers such as potassium sulfate, potassium nitrate, potassium carbonate are all prepared by using potassium chloride as raw material. According to the raw materials containing different potassium resources, there are four main potassium chloride production processes:(1) floatation process (2) carnallite process (3) dissolving crystallization process (4) heavy-medium process. Of which the reverse flotation cold crystallization process and hot melt crystallization process of carnallite process is the most advanced production technology. China’s potassium sulphate production has got a considerable capacity with varieties of technologies. Production process mainly has sulfate process, double decomposition process, potassium sulfate extracted by seawater or brine, solid potassium ore extraction process. It will be the main direction in the future that making full use of China rich saline lake and sea (brine) water resources and vigorously developing the innovation production technology of potassium sulfate.
The market of potassium nitrate for agriculture in China will be huge in the future. Potassium nitrate is a high-quality, chlorine-free potassium fertilizer. In addition to containing 45% of K2O, it contains 14% of nitro nitrogen. As a compound fertilizer of high quality and high efficiency, it is widely used in manuring the plants to which chlorine must be avoided, such as tobacco, coffee, tomato, grape, orange, gardening, flowers, potato, avocado, tea, vegetable and mango. It is also widely used as water soluble fertilizer. At present, the main potassium nitrate production methods in China include double decomposition method and ion exchange method. The process of vacuum-crystallization, double-decomposition developed by ECEC
is a production method with the most competitive power in China.
ECEC is one of the earliest engineering companies engaged in potassium fertilizer technology development and project construction in China. Since the mid-1980s, it has been working on the research and development of potassium fertilizer, especially in the field of potassium nitrate fertilizer. In 1997, ECEC developed the first plant in China for the production of ten thousand tons of potassium nitrate using the new technology of vacuum-crystallization and double-decomposition process, and the production plant using the said process had reached its quality and capacity standards in October 2000. Mengo 1200kt/a Potash Fertilizer Project in Congo (Brazaville) undertaken by ECEC in the mode of EPC general contract in 2013 is still under construction now. In addition, ECEC has maintained good business relations with a number of companies engaged in the production and research of potassium sulphate.
Sample projects (I)
——10kt/a Potassium Nitrate Plant of Yunnan Wotewei Chemical Co., Ltd.
Plant capacity: 10kt/a potassium nitrate
Source of technology: ECEC
Process flow: The raw material, which is potassium chloride, is put into the
No.1 reaction tank with an agitator, where it takes part in a double
decomposition reaction with the NH4NO3 in the secondary mother liquor from which
KNO3 and NH4Cl has been separated. The reaction liquid, after completely reacted
in No.1 and No.2 reactors, flows into an intermediate tank. The reaction liquid
from the intermediate tank is cooled through a plate-type heat exchanger
together with the primary mother liquor from which KNO3 crystals have been
separated, and then it is sent to a vacuum cooling crystallizer, where the
reaction liquor is cooled and most of KNO3 are crystallized out. The
crystallization liquid is thickened through a thickener and then goes through a
centrifuge to separate out the product KNO3. The primary mother liquor so
obtained is further processed in a double-effect evaporation and concentration
after heat exchanging with the reaction liquid, and is then sent into a NH4Cl
cold-precipitating crystallizer to make most of the NH4Cl precipitate,
crystallize and grow up. The crystallization liquid is thickened by a thickener
and then goes through a centrifuge to separate out the by-product of NH4Cl. The
secondary mother liquor so obtained flows back into the reaction tank. The
secondary steam condensate from evaporation and concentration is also added into
the reaction tank for reuse as make-up water.
ECEC’s scope of work: proving process technology, engineering design, technical service, supervision on construction, installation, commissioning and start-up.
Construction period: 1998-2000
Operation: The plant was built up and put into operation in August 2000, and reached the design capacity and quality standard in October 2000.
Currently, the daily production of the plant has reached 42t, which is over 120%
of the designed capacity. The quality of the product meets the design
requirements, the analysis of which are as follows (average during production
Potassium nitrate: K2O 44.96% Cl- 0.8%
N 14.3% H2O 3%
Ammonium chloride N 22.2% K2O 5.4% H2O 3.5%
Sample project (II)
——1200kt/a Mengo Potash Project in the Republic of Congo (in construction)
Plant capacity: 1200kt/a potassium chloride
Source of technology: Novopro, Changsha Design & Research Institute of Ministry of Chemical Industry
Process flow: mine rock is decomposed by raw brine, decomposed mother solution passes through three effect vacuum evaporation and three stage vacuum cooling crystallization to obtain carnallite. Carnallite is decomposed by raw brine and part of potassium chloride crystallization mother liquor to obtain sylvite slurry, the sylvite after filtration is heated to dissolve, clarify and filter to remove sodium chloride impurity with crystallization mother liquor and water, the obtained high temperature high potassium mother liquor goes on for vacuum cooling crystallization and precipitation of potassium chloride, potassium chloride slurry so obtained is thickened and dehydrated for drying.
Main units include:
Brine extraction unit: thermal injection agent is sent to various brine wells,
the brine returned from the underground wells passes through oil-water
separation and sent to processing unit; at the same time, the old brine and tail
salt is backfilled into the well groups that have been exploited over.
Evaporation unit: raw brine and decomposed mother liquor go over to
concentration by evaporation ,vacuum cooling crystallization to obtain
Filtration unit: carnallite slurry is filtered to obtain filter cake, the filter
cake is decomposed with raw brine and part potassium chloride mother liquor to
get sylvite slurry which is sent to hot melt after filtration.
Hot melt unit: sylvite is heated to dissolve, clarify and filter for removal of
sodium chloride impurity and get high temperature high potassium mother liquor
which is sent to crystallization unit.
Crystallization unit: high temperature high potassium mother liquor goes over to
vacuum cooling crystallization for precipitation of potassium chloride, and then
sent to dehydration for drying.
Granulation unit: potassium chloride crystal materials pass through dehydration
for drying, dyeing, compaction, slice, granulation, screening to obtain
qualified granule potassium chloride in grain size grade.
Post-treatment unit: potassium chloride particle surface goes on for hardening,
glazing, drying cooling, screening and coating to obtain product potassium
ECEC 's scope of work: EPC
Construction period: 2014-
Chemical content index of the product:
Granule potassium chloride: K2O KCL NaCL Mg2+ Ca2+ H2O
Weight percentage % ≥60 ≥95 ≤2.5 ≤0.3 ≤0.3 ≤0.2 2