The Azoty Group uses electrodialysis for the treatment of brackish water from the river Odra

Grupa Azoty Zakłady Chemiczne Police S.A.

Since 1969, when the first department of the company was put into operation, the Polish company Grupa Azoty Zakłady Chemiczne Police, has become a key player in the European fertiliser and chemical industry.

Thanks to the continuous modernization and expansion of its plants, Grupa Azoty it is increasing its production capacity and adapting its product portfolio to global standards, including reducing the environmental impact of production.

Grupa Azoty is a conglomerate of more than 50 companies based in Poland. It supplies its products to more than 100 countries worldwide.

Customer needs

With the growing volume of fertilizer production, Grupa Azoty is facing a significant increase in the consumption of process water, which will further increase after the construction of the new chemical complex Polimery Police for the production of propylene and polypropylene is completed.

The previous water treatment plant based on ion exchange technology (IEX) was already outdated and could not produce the required amount of water. Even the addition of a mobile reverse osmosis (RO) unit to the treatment plant did not solve this problem.

In addition, there has been a significant increase in the salinity of the Odra River at the abstraction point due to the works on the new sea channel, which has been reflected in the widening of the riverbed. The increase in salinity of the input water resulted in a reduced quality of the RO permeate, which caused an increase in the consumption of chemicals (H₂SO₄, NaOH) for the regeneration of the IEX columns. This further led to reduced process water availability and high waste production.

The economics of the treatment plant, burdened with these operating costs, was unbearable, and it was necessary to find a modern and at the same time cost-effective solution for the treatment of river water with a composition close to brackish water.

Challenge

Grupa Azoty compared two possible technological solutions for the desalination node. The first was the application of ultrafiltration (UF) pressure membrane processes and reverse osmosis (RO). The second option compared was electromembrane processes, namely electrodialysis (EDR).

The initial evaluation came out better for the combination of UF + RO. The well-known membrane technology achieves a high degree of desalination more easily at a relatively low investment cost. In contrast, EDR does not provide such a high degree of desalination but has a higher water yield compared to the UF + RO combination. In addition, EDR does not require costly membrane pretreatment compared to RO.

EDR technology has a 25% higher yield compared to the UF + RO combination, even with higher input water salinity, and lower operating costs (EDR is more resistant to potential scaling). The cost of electricity consumed is half the cost, and the cost of chemical consumption is even three times lower. Factoring in the normal lifetime of EDR membranes of over ten years, MEGA technology came out as the clear winner.

Solution

MEGA applied for the tender in 2019 as a subcontractor for the electrodialysis technology and was selected in early 2020. The technology was handed over to the customer and commissioned in 2021.

The installed solution is two RALEX® EWTU Twinline90 8L2S EDR-III/550-0.8 units, which have a total active ion exchange membrane area of over 14,500 m². The reverse electrodialysis technology is part of Grupa Azoty's new water treatment plant and can process up to 735.6 m³/h.

The EDR system is designed to produce 640 m³/h of demineralized water with a minimum of 87% recovery. The customer's water needs vary throughout the year and the EDR system can respond to the current demand and produce different quantities of water at ratios of 80, 160, 240, 320, 400, 480, 560, and 640 m³/h.

Outputs

The brackish water treatment system provided by MEGA is in operation 24/7, and thanks to the innovative design of the MEGA Twinline90, the entire process can be treated without interrupting the production process, with only a partial reduction in production capacity of 80 m³/h. Chemical cleaning (CIP) is carried out approximately once every two months.

Key parameters:

• The amount of RAS (TDS) in the input water is 739.4 mg/kg, of which Cl is 300 mg/kg.
• The TDS in the product is 229.4 mg/kg, of which Cl is 89.1 mg/kg.
• Minimum guaranteed recovery: 87 %.
• Continuous operation 24/7.
• Flexibility of the EDR system, which can supply demineralized water from 80 to 640 m³/h according to the actual production needs.
• Low chemical consumption, no antiscalants.
• High robustness of the equipment.

Customer service

During the test period, the bed of the Odra River was widened in close proximity to the inlet of the water treatment plant. As a result of this work, a large amount of sediment containing humic acids and other substances was released from the riverbed and partially entered the desalination node through the pretreatment. This has resulted in a very substantial reduction in the desalination capacity of the ion exchange membranes and thus a reduced capacity of the entire desalination unit.

MEGA responded immediately and, after identifying the problem, developed and tested a new unique membrane cleaning system that was able to fully restore the membranes to functionality at the site. The EDR technology proved its robustness by not having to replace the membranes, saving the customer an extremely large amount of unexpected financial costs.