Aquatech Delivers a Zero Liquid Discharge System for Flue Gas Desulfurization Wastewater at One of the World's Largest Coal-Fired Power Plants
| Challenge: | Taean Thermal Power Station needed to treat FGD wastewater, which couldn't be discharged due to high levels of contaminants. |
| Solution: | Aquatech's system removed minerals and recovered water using lime-soda softening, Seeded Brine Concentrators, and crystallizers for zero liquid discharge. |
| Customer Benefit: | The system ensured regulatory compliance, reduced costs, and achieved nearly 100% water recovery, improving wastewater management efficiency. |
This project at the Taean Thermal Power Station in South Korea implemented Aquatech’s advanced wastewater treatment system to address stringent Effluent Limitation Guidelines by converting challenging FGD wastewater into high-purity water and mixed salts, ultimately achieving zero liquid discharge and optimizing operational and capital expenditures.
Taean Thermal Power Station, located in Taean, South Korea, about 100 kilometers southwest of Seoul.
Aquatech's crystallization process technology on it's way to the Taean Thermal Power Station.
Challenge
In many geographic locations, wastewater from Flue Gas Desulphurization (FGD) scrubbers can no longer be discharged directly due to stringent Effluent Limitation Guidelines (ELG). Flue gas, generated from the coal burning process, is treated by these scrubbers, creating a challenging wastewater stream due to its high concentrations of suspended solids, heavy metals, and chlorides. The purged water from the scrubber process contains high concentrations of contaminants, making it unsuitable for discharge into the environment without further processing.
The high dissolved solids content in FGD wastewater makes recycling within the power plant difficult. Therefore, additional treatment is required to remove these minerals and recover water for reuse. The options for final disposal of this wastewater are limited to discharge under specified limitations or processing through crystallization in a zero liquid discharge (ZLD) system.
Solution
The FGD wastewater, with a flow rate of 60 m3/h, contains high concentrations of heavy metals, chlorides, and ammonia. To address this, a lime-soda softening process is utilized in a softening clarifier to remove most divalent minerals. The partially softened wastewater is then processed in Aquatech’s dual Seeded Brine Concentrator (SBC) trains, each processing 50% of the total capacity. The SBCs recover most of the wastewater as high-purity water by evaporation from the FGD wastewater stream.
Forced Circulation Crystallizers then process the wastewater concentrated by the SBCs to convert the dissolved minerals to a mixed salt suspension in the forced-circulation crystallizer and separated from the mother liquor using a belt filter press to achieve ZLD. The crystallizer completes the recovery of water such that the overall recovery is close to 100%, with minor system losses.
The FGD wastewater contains dissolved ammonia, which becomes volatile in the evaporation process and partially dissolves in the distillate water. The recovered high-purity water is then further treated for ammonia removal in a membrane-based post-treatment process before the distillate is recycled back to the power plant.
Customer Benefit
FGD wastewater presents significant challenges for conventional wastewater treatment due to its high mineral scaling potential. Aquatech’s extensive experience handling this complex water chemistry ensures that the system will perform and meet all process objectives while simultaneously optimizing the operating expenditure (OPEX) and capital expenditure (CAPEX) necessary to achieve ZLD.
Aquatech achieves this by uniquely controlling hardness in the softening clarifier, where the remaining hardness in the partially softened is used as seeds in the SBC. This partial softening approach with Aquatech SBC technology reduces OPEX by more than 20%. Additionally, the system employs MVCs in a power-driven evaporation system, significantly reducing steam and cooling water consumption compared to the conventional muti-effect evaporation systems commonly used in South Korea.
Most of the equipment supplied by Aquatech is prefabricated in our manufacturing facility, and modules are shipped to reduce installation costs at the site.