40 m² Skid-Mounted Membrane Filter Press “Tests the Waters” in Power Plant Desulfurization Wastewater

Desulfurization wastewater from coal-fired power plants has long been one of the toughest sections of the water treatment chain. The wastewater generated by the limestone–gypsum wet flue gas desulfurization (FGD) process often has a pH of around 4–6, high suspended solids concentration with fine particles, persistently high salinity and chloride ion levels, and also carries heavy metal ions such as Hg and Pb. It is highly corrosive and has an obvious scaling tendency. For filter press equipment, this means withstanding the continuous attack of corrosive media on filter plates and piping on the one hand, and, under conditions of fine particles and high salinity, “pressing the cake dry and discharging it cleanly” on the other, avoiding turbid filtrate or cake sticking to the filter cloth that would slow down the cycle. For this reason, equipment selection for the sludge dewatering stage of desulfurization wastewater is far more demanding than for general industrial sludge.

Recently, a 40 m² automatic plate-pulling membrane filter press completed a trial operation at a desulfurization wastewater treatment site at a power plant. Unlike a conventional standalone unit, this equipment was delivered in an integrated skid-mounted configuration: in addition to the filter press itself, it was equipped with a belt conveyor, a crushing feed hopper, an operating platform, a squeeze pump, and an air receiver tank, forming a complete closed loop from feeding to pressing, and from cake discharge to conveying. The customer’s positioning for this purchase was very clear—to use a compact, quickly deployable unit to verify the feasibility of the filter-press process under real desulfurization wastewater conditions and to accumulate operating data for the selection of a subsequent plant-wide treatment system.

According to on-site feedback, the trial met expectations. The sludge from desulfurization wastewater after pretreatment entered the 40 m² membrane filter press, and the membrane squeezing stage further reduced the filter cake moisture content. Industry data show that membrane squeezing has a significant deep-dewatering effect on sludge: secondary mechanical pressing can reduce pump-pressed dewatered sludge with a moisture content of about 80% to 50%–58%, a decrease of 15–25 percentage points compared with feed filtration alone. For desulfurization wastewater sludge, higher cake dryness directly reduces the pressure of subsequent transfer and disposal and also lowers the secondary load caused by filtrate returning to the system. The customer’s recognition of the filtration performance was based precisely on this actual performance of “dry cake, clear filtrate, and stable operation.”

The integrated skid-mounted design played a key role in this trial. Desulfurization wastewater treatment facilities in power plants often face practical constraints such as tight site space, complex piping connections, and limited construction windows. The skid-mounted combination integrates the filter press and auxiliary equipment before delivery, so that after positioning on site it can be connected to the system, greatly shortening installation and commissioning time. For a trial project, this configuration means a lower initial investment threshold and a faster verification pace—there is no need to carry out civil works according to the standards of a large fixed station building; instead, a compact unit can first be used to validate the process route.