Acid-Resistant Candle Filter for TiO2 Production - PTFE/Rubber Lined

Challenge:

Corrosive TiOSO4 solutions with fine particles pose a major filtration challenge in TiO2 production, often leading to equipment failure and process instability.

Our Solution:

Our specialized Automatic Precoat Candle Filter is engineered specifically for this harsh chemical environment. It combines a corrosion-proof construction (PTFE or Rubber lined) with intelligent, fully automated operation. This ensures continuous, high-precision solid-liquid separation, directly translating into higher product yield, superior clarity, and more stable production for your plant.

Key Advantages

1. Unmatched Corrosion Resistance for Acidic Service

• Corrosion-Proof Vessel: Choose between cost-effective Rubber Lining or superior PTFE Lining on carbon steel for optimal protection against strong acids.
• Resistant Internals: Filter candles and horizontal suspension tubes are crafted from FRPP or PVDF, ensuring long-term integrity in aggressive chemical environments.
• Stable Filter Media: High-performance PP filter cloths guarantee consistent filtration performance and durability under acidic conditions.

2. High-Efficiency & Low-Cost Filtration

• Depth Filtration with Precoat: Utilizes diatomaceous earth or cellulose to form a stable precoat layer, trapping sub-micron particles effectively.
• Extended Cycle Times: High dirt-holding capacity reduces regeneration frequency, lowering operational costs.
• Complete Cake Discharge: Efficient gas back-blowing ensures clean regeneration, restoring full flow capacity.

3. Smart & Automated Operation

• Hands-Free Control: Fully integrated PLC/DCS system automates the entire cycle (filtration, cake discharge, washing).
• Remote Monitoring & Support: Enables remote diagnostics and troubleshooting for minimized downtime and swift support.

Technical Specifications

Structure Overview of the Candle Filters

Working Principle

The filtration system typically comprises filters, a precoat tank, a precoat pump, a dosing tank, a metering pump, instruments, valves, piping, and a control system.

Before starting filtration, a precoat solution with diatomaceous earth or Perlite filter aid is prepared in the pre-coat tank and then pumped into the filter for a circulation cycle to establish a uniform and dense pre-coat layer on the filter elements.

Subsequently, the unfiltered liquid enters the vessel. Impurities are efficiently retained by the pre-coat, and the clarified filtrate exits. Meanwhile, the metering pump is activated to inject filter aid from the dosing tank into the feed stream at a controlled, metered rate.

When the differential pressure across the filter reaches the set limit, or the predefined filtration time is met, the filter elements require regeneration. First, the inlet is closed, and compressed gas is introduced to pressurize the vessel, displacing the residual liquid. Next, high-pressure gas is injected in reverse through the filtrate outlet, creating a pressure shock from the inside of the element outwards, instantly dislodging the accumulated filter cake. This cake is then discharged via the bottom discharge port.

After the cake is fully purged, the filter elements can be thoroughly washed with cleaning agents, such as hot water, to complete the regeneration process.

System Control：

The filtration system is fully automated and can be equipped with a local PLC control panel or integrated directly into the customer’s DCS system for centralized control.

Three control modes are available:

• Differential pressure control
  
• Time-based control
  
• Manual control

Core Components

HC Intermediate Shell Section (Modular Design)

FRPP horizontal suspended tubes

Candle filter elements

P&ID Diagrams：

Typical Applications in the Titanium Dioxide Industry

Our fully automatic candle filters deliver outstanding performance in two critical stages of TiO₂ production:

Ⅰ. Hot Filtration of Acid Digestion Slurry

After ilmenite is digested with sulfuric acid and the resulting black titanium liquid is settled, the filter handles the hot, acidic slurry directly. Equipped with acid-resistant and high-temperature-resistant filter media, and operating with a precoat filter aid layer, it effectively removes undecomposed ore particles, silicates, and insoluble residues. This not only prevents abrasive wear on downstream centrifuges and filter cloths but also eliminates impurities that could compromise TiO₂ crystal structure and whiteness during hydrolysis. The automatic back-pulse cake discharge ensures continuous, trouble-free operation.

Ⅱ. Precision Control Filtration after Ferrous Sulfate Crystallization

Following vacuum cooling and primary separation of ferrous sulfate crystals, the titanium liquid still contains fine crystals and suspended solids. Our candle filter, with precoated filter aid, performs high-precision polishing filtration to reduce solids to an extremely low level. This step guarantees that only high-purity titanium liquid enters the hydrolysis stage, significantly improving TiO₂ purity and overall yield.

With robust construction, automated regeneration, and superior filtration efficiency, our candle filter system is the trusted solution for critical solidliquid separation throughout the titanium dioxide production chain.

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