Process Application Expertise

Potassium Chemicals Sector

K-Tech has developed a number of technologies related to the production of potassium chemicals using more economical feedstocks than those typically employed in the “conventional” processing industries. Examples include the following:

Production of Potassium Carbonate Directly from Potassium Chloride:

K-Tech has developed technology for the production of potassium carbonate using a continuous ion exchange process. Potassium chloride (including agricultural grade “red” potash), lime and carbon dioxide are used as the primary feedstocks, thus the high cost associated with the current methods for the production of the carbonate, based on the use of potassium hydroxide that is produced by an electrolytic process, is greatly reduced.

In the conventional process for the production of potassium carbonate, potassium hydroxide (KOH) that is generally produced via an expensive electrolytic process is reacted with carbon dioxide (CO2) to form potassium carbonate via the following reaction:

2 KOH + CO2 → K2CO3 + H2O

The process is straightforward; however this simplicity is off-set by the need for an expensive raw material, namely KOH.

In the K-Tech process, which was originally described in U.S. Patent 5,449,506 Process for Producing Potassium Carbonate, a continuous ion exchange approach is described where the potassium chloride was treated in the ion exchange process with ammonium carbonate to exchange potassium with an ammonium ion to produce a solution of potassium carbonate and co-product ammonium chloride. The overall reaction is as follows:

2 KCl + (NH4)2CO3 → K2CO3 + 2 NH4Cl

The potassium carbonate product is concentrated to a 45% saturated solution, which can be used as a high analysis, completely water soluble non-chloride form of potash (0-0-62). This solution can also be dried in a fluidized bed to form a granular solid form of potassium carbonate for various industrial uses.

In some regions, the ammonium chloride may have agricultural or other industrial value. If this is not the case for a specific location, then the ammonium chloride is treated with slaked lime to release the ammonia for recovery and recycle, and to produce a co-product calcium chloride material. The calcium chloride can be processed to produce liquid; flake; and anhydrous chloride products that have a range of industrial uses. The recovery of the ammonia is as follows:

2 NH4Cl + Ca(OH)2 → 2 NH4OH + CaCl2

The ammonium carbonate is produced on site by the reaction of ammonia with carbon dioxide and water. Slaked lime is produced by reacting burnt lime with water.

Continued K-Tech development has led to further improvements in the technology and improved economics. When compared to the conventional methodology for the production of potassium carbonate, the costs associated with the K-Tech approach are considerably less, especially when considering the use of potassium hydroxide as the K-source for the conventional technology.

Potassium Thiosulfate via Ion Exchange Using Sulfur Compounds and Intermediate Potassium Solutions derived from
Potassium Chloride:

There are numerous geographical areas where sulfur deficiencies have become critical and also various crops where sulfur (an important secondary

crop nutrient), as well as potassium, are vital to optimum growth. Potassium thiosulfate is an ideal material to provide a high level of sulfur for each unit of potassium. Potassium thiosulfate provides about 0.68 units of soluble sulfur per unit of K2O, which is approximately double the amount that is provided by potassium sulfate. In addition, potassium thiosulfate has a relatively low salt index, thus making it appealing for crops that have some level of salt intolerance.

Potassium thiosulfate is usually made via the reaction of a potassium material, such as potassium hydroxide (KOH), with sulfur-containing materials in a thiosulfate production system. In the conventional approach, KOH can be reacted in a thiosulfate reaction system in much the same manner as ammonia is reacted with sulfur compounds to produce ammonium thiosulfate. The K-Tech ammonium thiosulfate technology is also applicable to the production of potassium thiosulfate using KOH, however regardless of the production technique, the use of KOH as a feedstock is expensive.

To this end, K-Tech has developed technology for the production of potassium thiosulfate by initially producing a potassium intermediate chemical directly from agricultural grade potassium chloride (KCl) via a proprietary ion exchange methodology, then reacting the potassium intermediate with sulfur and sulfur dioxide to produce potassium thiosulfate.

A key advantage to the K-Tech process approach is that the potassium thiosulfate is made from lower cost feedstocks thus providing more attractive economics to the fertilizer producer.

Potassium Sulfate Production via Ion Exchange:

Potassium sulfate (K2SO4) has a variety of agricultural and industrial uses. In agriculture, it is the principal form of non-chloride potassium for crops, and also provides the secondary nutrient sulfur in soluble form. About 95% of potassium sulfate worldwide is used in agriculture, while the balance is used in higher purity industrial markets. Its principal industrial use is in the manufacture of gypsum wallboard.

One of the current processes used to produce potassium sulfate includes the application of a high temperature reaction system known generally as the Mannheim process, although similar techniques have been applied. In this process, potassium chloride is reacted with sulfuric acid in a higher temperature reaction system to produce potassium sulfate and a co-product hydrochloric acid (HCl). This technology has been used, in various forms, to produce the sulfate material, and while workable, it does have a number of critical issues associated with it in order to produce high quality material. The overall reaction associated with this approach is as follows:

2 KCl + H2SO4 → K2SO4 + 2 HCl

K-Tech personnel have worked closely with companies producing K2SO4 using this approach, as well as developing methods to purify the resulting HCl. Operation and control of these high temperature reaction systems can be cost-intensive and, as expected, there are considerable capital and maintenance issues associated with the methodology.

An advanced method has been developed by K-Tech that eliminates many of the complications associated with the high temperature systems. K-Tech has improved ion exchange technology for the production of potassium sulfate using low cost feedstocks. In one version of the approach, agricultural grade KCl and a sulfate source(from brines or by-products) can be used to produce an industrial-quality potassium sulfate product via the following ion exchange assisted reaction:

2 KCl + X-SO4 → K2SO4 + 2 X-Cl
Ion Exchange Assist (where X is the brine cation)


The resulting solution from the ion exchange assisted reaction is further treated to recover an industrial-grade potassium sulfate product in solid form. The co-product X-Cl can be recovered or disposed of depending on the location of the facility and the periphery process systems.

Potassium Phosphate Compounds

There are a number of potassium phosphate compounds that find agricultural and industrial uses. Among these are mono-potassium phosphate (MKP), di-potassium phosphate (DKP) and potassium tetra-pyrophosphate (KTPP). Typically these compounds are made using high quality phosphoric acid, i.e. technical-grade or food grade materials, and potassium hydroxide (KOH).

While the basic techniques for producing the products are somewhat straightforward, the cost of the raw materials results in a high cost product.

K-Tech has developed a process which can use agricultural-grade phosphoric acid and an intermediate potassium carbonate that is produced using the K-Tech K2CO3 process technology.

The process relies on a proprietary acid pretreatment and sequential neutralization approach where the contaminants normally contained in the phos-acid are precipitated and rejected from the solution as a fertilizer blend material. The resulting potassium phosphate solution is further concentrated to produce purified potassium phosphate materials. KTPP can also be produced using the intermediate purified product via further thermal treatment.

The net result is that with the K-Tech approach, the purified potassium phosphate products are made using agricultural-grade potash (KCl) and ag-grade phos-acid which produces substantial cost savings when compared to the traditional methodology.

Potassium Polyphosphate and
Polyphosphate Production

(Coming Soon)

Potassium Hydroxide Production
by Modified Ion Exchange

(Coming Soon)