LW Horizontal Decanter Centrifuge for Chemical Sludge Dewatering & Zero Liquid Discharge (ZLD) System
LW Horizontal Decanter Centrifuge for Chemical Sludge Dewatering & Zero Liquid Discharge (ZLD) System
1. Basic Definition & Core Working Principle of LW Series Horizontal Spiral Decanter Centrifuge
Working Flow
- Raw chemical sludge (solid content: 1%~10%) enters the horizontal bowl through the central feeding pipe;
- High-speed rotation of the bowl generates centrifugal force of 2,000~4,000 G. Denser solid sludge rapidly settles and adheres to the inner wall of the bowl;
- A tiny differential speed is maintained between the built-in screw conveyor and the bowl, continuously pushing solid sludge toward the conical section for dry cake discharge;
- Clarified filtrate flows out through overflow ports at the large end of the bowl and is delivered to downstream membrane concentration / evaporative crystallization ZLD units;
- Fully continuous operation: continuous feeding, continuous sludge discharge and continuous clear water output without intermittent shutdown.
2. Specialized Configuration of LW Models for Chemical Industry (Adapted to ZLD Working Conditions)
(1) Material Upgrades
- Bowl & screw conveyor: 304 / 316L stainless steel; 2205 duplex stainless steel for high-salinity and high-chloride working conditions;
- Screw blades: tungsten carbide surfacing wear-resistant coating; hard alloy liners equipped at feeding and cake discharge ports;
- Fully closed CIP online cleaning ports integrated, compatible with online cleaning by corrosive chemicals, preventing odor leakage.
(2) Structural Optimization (Core for Water Reduction in ZLD)
- Large length-diameter ratio of 4.0~5.0 plus long dry zone with large cone angle to extend sludge dewatering residence time;
- Adjustable overflow weir baffle to precisely control filtrate clarity, separation efficiency ≥92%;
- Hydraulic differential speed drive: automatically adapts to variable sludge loads. Stable cake moisture content ranges from 70% to 78% (can drop below 65% after flocculant conditioning), sludge volume reduced by over 60%, greatly cutting energy consumption of downstream evaporation equipment.
(3) Automatic Supporting System
- Dual-motor variable frequency linkage; real-time monitoring of current, vibration, torque and differential speed;
- Interlock protection against overload, excessive vibration and abnormal torque, supporting 24-hour continuous operation;
- PLC interlocked with upstream sludge conditioning tank and downstream ZLD membrane system for fully closed-loop automatic operation.
Reference Selection Parameters for Mainstream Chemical Models
| Model | Bowl Diameter | Max. Throughput (m³/h) | Applicable Chemical Sludge Conditions | Main Motor Power (kW) |
|---|---|---|---|---|
| LW350 | 350 mm | 15~20 | Fine chemical, dyestuff sludge (small-scale) | 18.5 |
| LW450 | 450 mm | 30~45 | Pharmaceutical intermediate, electroplating sludge | 30 |
| LW530 | 530 mm | 60~75 | Petrochemical, coal chemical, high-salinity sludge | 45~55 |
| LW650 | 650 mm | 90~120 | Centralized sludge for large chemical parks | 75 |
3. Core Position of LW Decanter Centrifuge in Chemical ZLD Process
Complete Process Flow (Key Node of LW Centrifuge)
- Pretreatment & Conditioning Unit Chemical biochemical / physicochemical sludge → PAC & PAM flocculant dosing for conditioning → Homogenization in sludge thickening tank
- LW Decanter Centrifuge Dewatering (Core Section) Conditioned sludge is pumped into LW centrifuge:
- Solid phase: Low-moisture sludge cake → Hazardous waste incineration / landfill / resource utilization
- Liquid phase: Clarified filtrate (SS＜100 mg/L) delivered to ZLD advanced treatment
- ZLD Concentration & Salt Separation Unit Centrifuge filtrate → Multimedia filter → Ultrafiltration (UF) → Primary / Secondary Reverse Osmosis (RO)
- RO permeate (purified clean water): Fully recycled for production circulation and equipment washing
- RO concentrate (high-salinity mother liquor): Sent to MVR (Mechanical Vapor Recompression) evaporator
- Crystallization & Solidification to Achieve True Zero Liquid Discharge MVR evaporation & concentration → Cooling crystallization → Salt crystals transported outside as solid waste for disposal Evaporation condensate flows back to the front of RO system for reuse, with zero liquid wastewater discharge throughout the whole process.
Three Major Load-Reduction Values of LW Centrifuge for ZLD System
- Sharp reduction of influent volume to membrane units Raw sludge moisture content reaches 98%; after dewatering by LW centrifuge to 75%, liquid volume is directly cut by 75%. The specification selection of RO membranes and MVR evaporators can be downsized, lowering one-time investment by over 30%.
- Protection of downstream membrane and evaporation equipment Over 90% suspended sludge particles are removed in advance by centrifugation, avoiding RO membrane fouling and scaling on evaporator heat exchange tubes, extending membrane service life, reducing cleaning frequency and cutting operating energy consumption by 25%.
- Lower hazardous waste disposal cost Lower moisture content of sludge cake reduces the total volume of hazardous waste transported externally, significantly cutting per-ton sludge disposal expenses.
4. Comparison with Traditional Dewatering Equipment: Advantages of LW Decanter Centrifuge for ZLD
(1) vs. Plate & Frame Filter Press
(2) vs. Belt Filter Press
Exclusive Advantages of LW Centrifuge for Chemical ZLD
- Fully enclosed structure for centralized collection of volatile chemical waste gas without secondary pollution;
- Strong adaptability to ultra-fine chemical sludge (particles ≥3 μm);
- Modular layout with floor area only 1/3 of plate & frame filter, suitable for renovation and expansion of existing wastewater stations to build ZLD systems;
- Tolerant of fluctuating influent solid concentration and impact loads, ensuring non-stop stable operation of ZLD system.
5. Typical Application Scenarios
- Fine chemical industry: Dewatering and ZLD treatment of dyestuff, pigment, resin and pharmaceutical intermediate sludge;
- Petrochemical & coal chemical industry: Oily sludge, circulating water sludge and high-salinity biochemical sludge;
- Electroplating & surface treatment: Heavy metal sludge; centrifuge filtrate enters salt separation ZLD system to recover nickel, copper and other metal salts;
- Fluorine chemical & lithium salt chemical industry: High-corrosion and high-salinity sludge (2205 duplex stainless steel LW models recommended).
6. Key Operation Control Points (Guarantee Stable Compliance of ZLD)
- Stabilize sludge feeding concentration at 2%~6%, equipped with automatic chemical dosing system to optimize flocculation performance;
- Adjust bowl rotating speed and differential speed according to sludge salinity and viscosity to balance sludge cake dryness and filtrate clarity;
- Conduct daily online CIP pickling & alkaline washing to remove salt scaling inside the bowl and maintain stable separation efficiency;
- Online SS monitoring of filtrate; automatic interlock adjustment when exceeding standard to prevent suspended solids from entering downstream RO membranes.
7. Key Deliverables for Tender & Technical Agreement
- Material breakdown, length-diameter ratio, separation factor and differential drive form of anti-corrosion & wear-resistant LW decanter centrifuge;
- Guaranteed sludge cake moisture content and effluent SS index of filtrate;
- Matching flow rate and water quality interface parameters with ZLD membrane and MVR evaporator;
- Full-automatic interlock control logic and configuration of anti-corrosion cleaning system;
- Continuous operation load, energy consumption and maintenance consumables list.
Q1：Is the LW decanter centrifuge suitable for chemical sludge ZLD zero discharge projects?
A：Yes, it is the core pretreatment equipment for chemical ZLD systems. It continuously removes suspended solids and sludge from wastewater, reduces the water volume entering RO and MVR units, effectively prevents membrane fouling and evaporator scaling, and provides stable water quality guarantee for zero liquid discharge.
Q2：What is the final sludge cake moisture content after dewatering?
A：For conventional chemical biochemical and physicochemical sludge, the stable moisture content is 70%–78%. With reasonable PAC/PAM dosing conditioning, the moisture content can be reduced below 65%, realizing maximum sludge reduction and lowering ZLD system operation cost.
Q3：What kind of chemical sludge can this LW centrifuge handle?
A：It is widely applicable to fine chemical dyestuff and resin sludge, pharmaceutical intermediate sludge, petrochemical oily sludge, coal chemical high-salinity sludge, electroplating heavy metal sludge, fluorine and lithium chemical corrosive sludge, and all kinds of industrial sludge supporting ZLD systems.
Q4：What material options are available for corrosive and high-salinity wastewater working conditions?
A：Standard configuration adopts 304/316L stainless steel. For high chlorine, high salt and strong acid-base corrosive workingconditions, 2205 duplex stainless steel is optional. The screw blade is overlaid with tungsten carbide to ensure wear resistanceand long-term stable operation.
Q5：Why choose decanter centrifuge instead of plate&frame filter press for ZLD projects?
A：Plate&frame filter press works intermittently with low efficiency, easy filter cloth blockage and large floor area, which cannot match the 24-hour continuous operation requirement of ZLD systems. LW decanter centrifuge features fully continuous feeding and discharging, fully closed operation, clear filtrate, stable effluent water quality, and perfectly matches the continuous and stable operation logic of zero discharge systems.
Q6：What is the clarity of the filtrate after centrifugal treatment?
A：The effluent SS is stably controlled below 100mg/L with a separation efficiency of over 92%. The filtrate is clear without suspended solids, which can directly enter the subsequent UF+RO membrane concentration process, effectively protecting the membrane elements.
Q7：How does the centrifuge reduce the overall investment and operation cost of ZLD system?
A：The centrifuge reduces the sludge liquid volume by more than 60% through front-end dewatering and reduction, which greatly reduces the treatment load of downstream RO membranes and MVR evaporators, lowers equipment selection specifications, saves more than 30% of initial investment, and reduces evaporation energy consumption and hazardous waste disposal cost simultaneously.
Q8：Does the equipment support fully automatic operation and linkage with ZLD system?
A：Yes. It is equipped with full-frequency conversion automatic control system, which can realize automatic adjustment of differential speed and load. It can be seamlessly linked with the front conditioning tank and rear membrane & evaporation equipment to realize fully enclosed automatic operation of the whole ZLD system with unattended 24-hour operation.
Q9：What maintenance work is required for long-term operation?
A：The equipment is equipped with CIP online cleaning function. Daily acid and alkali online cleaning can remove internal salt scaling and sludge deposition. Regular inspection of bearing and transmission system is required. The whole machine has low wear, few vulnerable parts and low later operation and maintenance cost.
Q10：What are the common model specifications and treatment capacity?
A：Conventional models cover small, medium and large working conditions: LW350 (15–20m³/h), LW450 (30–45m³/h), LW530 (60–75m³/h), LW650 (90–120m³/h). Customized models are available for super large flow and special working conditions.
