Baihuipu Completes FGD Wastewater ZLD Retrofit
Baihuipu has completed a FGD wastewater ZLD retrofit at a coal-fired power plant where the flue gas desulfurization purge had been discharged after conventional treatment. The scrubber purge carries chlorides above 20,000 mg/L, gypsum fines and heavy metals, and the plant wanted it off the discharge outfall entirely. The retrofit, finished this month, treats the purge through lime softening and sulfide precipitation, evaporates it in a mechanical vapour recompression unit built in chloride-resistant materials, and crystallises the remaining brine. Distillate returns to the scrubber as make-up, and the plant discharge for this stream is now zero.
Key Features and Benefits
Pretreatment That Protects the Evaporator
Lime softening drops the calcium before it reaches the heat transfer surfaces, and sulfide precipitation pulls mercury and other heavy metals into a filterable solid. Gypsum fines carried over from the dewatering area are removed in the clarification stage, because they seed scaling and wear pump internals. If your site also runs this kind of duty, What Is Actually in the Stream covers the cost side of the decision in more depth.
We set out the wider process route in boiler chemical cleaning wastewater.
The sludge from this stage is the only solid route out of the front end, and it is pressed and sent to the plant existing solid waste handling. Skipping or under-sizing pretreatment is the most common reason ZLD evaporators on this duty spend their lives in chemical cleaning. For the reuse angle specifically, Baihuipu Releases UF Pretreatment Package for SWRO goes further than we can here.
Materials Chosen for Chlorides, Not for Price
At 20,000 mg/L chloride and boiling temperature, standard stainless does not survive. The evaporator heat exchanger and the wetted internals are in higher-alloy material selected against the measured chloride, with the condenser side in ordinary grades where the water is clean. We have written about the downstream implications separately in Baihuipu Updates Potable Water Testing Protocol.
Mechanical vapour recompression keeps the energy demand close to the electrical input of the compressor rather than to live steam consumption, which matters at a plant where steam is the product being sold.
A Salt Stream With a Defined Route
The crystalliser produces a mixed salt dominated by sodium chloride and sodium sulphate. The plant sends it to controlled disposal rather than claiming a saleable product, which we consider the honest baseline: a saleable salt needs purity the scrubber liquor rarely supports.
Distillate quality is checked by conductivity at the condenser and returns to the scrubber as make-up. During the performance run the distillate stayed below 50 µS/cm, and the scrubber accepted it without any change to its chemistry control.
Technical Specifications
FGD purge treatment performance during the 72-hour acceptance run:
| Parameter | Raw FGD Purge | After Retrofit |
|---|---|---|
| Chloride | above 20,000 mg/L | zero liquid discharge; distillate below 50 µS/cm |
| Mercury | as measured in purge | removed in sulfide precipitation sludge |
| Discharge volume | about 8 m3/h to outfall | zero |
| Distillate reuse | not applicable | returned as scrubber make-up |
| Energy source | not applicable | MVR compressor, electrical input |
Why Choose Baihuipu as Your Manufacturer
Two decades in this industry teaches you that most treatment problems are procurement problems in disguise. Someone bought the cheapest skid, nobody checked the equalisation volume, and eighteen months on the plant cannot hold its consent limit. We build differently.
In-House Fabrication
Our Guangdong works produces everything from standard modular units to fully bespoke lines. Building in-house keeps cost, schedule and quality under our own control rather than a subcontractor's goodwill.
Certification and Export Practice
CE marking is standard and we work to ISO 9001 procedures. Where a project calls for specific material grades, pressure vessel certification or ATEX-rated equipment, we build to that standard and ship the full documentation pack.
Two Decades of Field Data
Food and beverage, chemicals, electroplating, textile dyeing, mining, municipal work — we have commissioned across all of them. The useful part is not the project count, it is having seen how plants fail in year seven and designing those failures out.
Complete Units and Turnkey Plants
Whether you need a single package unit or a turnkey installation with civil works, we deliver the entire treatment scheme. Our engineering team covers process, mechanical, electrical and automation so one party owns the outcome.
Spares, Service and Commissioning
Membranes, dosing pumps, diffusers, instrumentation and blowers are stocked for the systems we sell. Our control systems support remote diagnostics, and we can put an engineer on site for commissioning, training or an unplanned shutdown.
Let's Look at Your Numbers
Share your water analysis and site constraints and we will give you a straight assessment of the process route and the realistic operating cost before you commit to anything. Contact our engineers at WhatsApp: +86 13631765076, or find us at hkbhp.com.
WhatsApp: +86 13631765076
Customer FAQs
Why is FGD wastewater so difficult to treat to ZLD?
It combines very high chloride, high hardness from gypsum contact, heavy metals and variable solids carryover. Each of these drives a different design decision, and the chloride level in particular dictates the materials of construction.
Can the crystalliser salt be sold?
Usually not without additional purification, because scrubber liquor carries metals and organics that end up in the salt. Controlled disposal is the honest default, and a saleable stream should be demonstrated by analysis before anyone promises it.
What does pretreatment typically remove before evaporation?
Hardness by lime softening, heavy metals by sulfide precipitation, and suspended gypsum fines by clarification. Removing them ahead of the evaporator is what keeps the heat transfer surfaces clean between chemical washes.
Is MVR the right evaporator for every FGD ZLD project?
It suits sites with cheap electricity and expensive steam, which describes most power plants. Where the site has surplus low-pressure steam and constrained power, a multiple-effect design can win. We size against the site tariff, not against habit. The operating detail behind this sits in chemical dosing system power plant.
Readers planning similar projects often also read Baihuipu Commissions Second Train at Coastal Desalination Plant and Baihuipu Publishes Desalination Energy Cost Benchmark for the process detail behind these systems.
