Everything You Need to Know – Activated Bleaching Clay
We understand that Activated Bleaching Clay Bentonite planning can be complex, and you may have questions along the way.
General Activated Bleaching Clay Questions
What Is Activated Clay?
Activated clay is made of clay (mainly Bentonite) as raw materials, treated by inorganic acidification or salt or other methods, and then rinsed and dried by water, the adsorbent is milky white powder, odorless, tasteless, non-toxic, strong adsorption performance, can absorb colored substances, organic substances. Widely used in mineral oil, animal and vegetable oil, wax and organic liquid decolorization refining. It can also be used as moisture desiccant, internal drug alkali antidote, vitamin A, B adsorbent, lubricating oil coincidence contact agent, gasoline vapor phase fine preparation, etc., and can also be used as medium temperature polymerization catalyst, high temperature polymerization agent and raw material for manufacturing granular clay
How to Refine Palm Oil Using Activated Bleaching Earth (Activated Clay)?
Detailed Steps for Palm Oil Decolorization Using Activated Clay:
Palm oil refining typically involves four main stages: degumming, deacidification (neutralization), decolorization (bleaching), and deodorization. Activated clay is central to the decolorization (bleaching) step. Its primary purpose is to remove color bodies (e.g., carotenoids, chlorophyll, and their degradation products), trace metals, residual soaps, phospholipids, oxidation products, and off-flavors/odors.
Specific Steps of the Activated Clay Decolorization Process:
1. Pre-treatment & Conditioning:
Feedstock Preparation: Decolorization usually follows deacidification (either alkali refining or physical refining). Oil entering the bleaching section should have completed degumming and deacidification, have low Free Fatty Acid (FFA) content (especially for physical refining), be low in moisture (dewatered and dried), and have minimal residual soaps and gums.
Preheating: Deacidified palm oil is pumped into the bleacher vessel. This is typically a closed, agitated tank equipped with heating coils/jacket and a vacuum system.
Drying & Deaeration: Under vacuum (typically 20-70 mbar absolute / 15-50 mmHg abs) and with moderate agitation, the oil is heated to 90-110°C (commonly 98-110°C) and held for a period (e.g., 15-30 minutes) to thoroughly remove trace moisture. Effective drying and maintaining vacuum are critical prerequisites for successful bleaching.
2. Addition of Activated Clay:
Dosage Calculation: The amount of activated clay is determined based on the crude oil quality (primarily color intensity, soap content, impurity levels) and the target color for the refined oil. For standard RBD palm oil, dosage typically ranges from 0.5% to 2.0% (w/w). Higher dosages (up to 3-5% or more) may be needed for red palm oil (where carotenoid retention is desired) or deeply colored crudes.
Addition Method: Under agitation and vacuum, the calculated amount of dry activated clay is evenly dispersed into the hot oil via a charging port or powder injection system. Clumping must be avoided to ensure thorough contact with the oil.
3. Bleaching Reaction:
Temperature Maintenance: The oil-clay mixture is maintained at the set bleaching temperature (98-110°C is standard).
Agitation: Moderate agitation continues (avoiding excessive shear that could damage clay structure or incorporate air) to ensure uniform dispersion of clay particles, maximizing the adsorbent surface area.
Vacuum Maintenance: High vacuum (20-70 mbar absolute) is continuously applied. This prevents oil oxidation at high temperatures and helps remove gases and volatile compounds released during adsorption.
Contact Time: The clay remains in contact with the oil under these conditions for typically 15 to 30 minutes. Excessive time risks oil hydrolysis/isomerization (forming trans fats), while insufficient time leads to incomplete adsorption.
4. Cooling & Discharge:
Agitation Stop: At the end of the contact time, agitation is stopped first to allow brief settling of clay particles (aids subsequent filtration).
Cooling (Optional): The mixture may sometimes be cooled to 70-90°C to reduce oxidation risk during filtration and lower oil viscosity, depending on the specific process design.
Discharge: The oil-clay slurry (bleached oil slurry) is discharged from the bleacher to the filtration system, typically using vacuum or a pump, maintaining vacuum during transfer.
5. Filtration & Separation:
Filtration Equipment: A leaf filter (most common) or plate and frame filter press is used.
Filter Aid: A pre-coat of filter aid (e.g., diatomaceous earth or perlite) is usually applied to the filter medium (cloth/paper/plates). A small amount of “body feed” filter aid is often added to the slurry just before discharge to improve flow rate and reduce filter cake compressibility.
Filtration: The bleached oil slurry is forced under pressure through the filter medium. Clear, decolorized oil passes through as the filtrate.
Blow-Down & Oil Recovery: After filtration, the filter cake is blown with steam (or inert gas like N₂) to recover trapped oil.
Cake Discharge: The filter is opened, and the spent clay cake (containing adsorbed impurities, color bodies, and residual oil) is removed. Spent clay typically contains 20-40% retained oil.
Safe Cake Handling: Spent clay is hot and oil-laden, making it extremely prone to spontaneous combustion! It must be cooled under inert atmosphere or handled with extreme care for immediate safe disposal (e.g., controlled incineration, treated landfill).
6. Post-Filtration Treatment:
Polish Filtration: Before proceeding to deodorization, the decolorized oil usually passes through a polish filter (e.g., bag filter or cartridge filter) to remove any trace fines that penetrated the main filter.
Storage (Buffering): The filtered, bleached oil is stored in a buffer tank, ready for the deodorization stage.
Key Influencing Factors:
Clay Quality: Activity, particle size distribution, free acidity, moisture content, filtration characteristics.
Oil Quality: Crude oil color, residual soap, phospholipid content, moisture, FFA level, oxidation state.
Process Conditions: Temperature, vacuum level, contact time, agitation intensity, clay dosage.
Filtration Efficiency: Filter type, filter aid usage, operating pressure, effectiveness of cake blow-down.
Summary:
Activated clay plays a vital role in palm oil refining for decolorization and impurity removal. The core process occurs under high temperature, vacuum, and agitation, ensuring the clay effectively adsorbs undesirable components. Efficient and reliable filtration then completely separates the spent clay cake from the decolorized oil, yielding clarified palm oil with significantly reduced color. This provides qualified feedstock for deodorization. Crucial aspects ensuring effectiveness and safety (preventing oxidation and fire hazards) are rigorous vacuum application, thorough drying, precise temperature control, optimal contact time, and highly efficient filtration.
How to Refine Soybean Oil Using Activated Bleaching Earth (Activated Clay)?
the process for refining soybean oil using activated bleaching earth (activated clay):
How to Refine Soybean Oil Using Activated Bleaching Earth?
The use of activated bleaching earth is a critical decolorization step in edible oil refining. It primarily removes pigments (such as chlorophyll, carotenoids), residual trace soaps, phospholipids, metal ions, oxidation products, and other colloidal impurities and off-flavors from the oil.
Below is the standard operating procedure and key considerations for using activated bleaching earth to refine soybean oil:
I. Refining Process (Decolorization Step)
1. Pre-treatment of Crude Oil:
Filtration: Crude soybean oil must first undergo preliminary filtration (e.g., plate-and-frame filter, bag filter) to remove large mechanical impurities (like soybean meal fragments).
Dehydration: If the crude oil has high moisture content (typically required to be below 0.2%), dehydration (e.g., vacuum drying) is necessary, as moisture significantly impairs the adsorption efficiency of the clay.
Degumming & Neutralization: Prior to decolorization, the crude oil usually undergoes degumming (removing phospholipids and other colloids) and neutralization (alkali refining, removing free fatty acids – FFA). These steps remove significant impurities, reducing the load on decolorization and improving clay efficiency. Decolorization typically occurs after neutralization and before deodorization.
2. Preheating the Oil:
Pump the pre-treated soybean oil into a decolorization vessel (typically a vacuum vessel with agitation and heating/cooling jackets).
Under vacuum (typically 50-100 mbar absolute pressure), heat the oil to the required decolorization temperature. The typical temperature range is 90°C – 110°C (194°F – 230°F). Vacuum helps remove air and trace moisture from the oil.
3. Adding Activated Bleaching Earth:
Close off the vacuum source but maintain agitation.
Slowly and evenly sprinkle the calculated amount of dry activated bleaching earth into the oil through a feed port. Key Points:
Dosage: Clay addition is typically 0.5% – 5% of the oil weight. The exact amount depends on:
The initial color depth (Lovibond/RBD color value) of the crude oil.
The desired color of the finished oil.
The adsorption capacity (activity) of the clay itself.
The impurity content of the oil.
Optimal economical dosage is usually determined through lab-scale trials.
Uniformity: Ensure the clay is evenly dispersed throughout the oil to prevent clumping. Effective agitation is crucial. Some processes premix the clay with a small amount of hot oil to form a slurry before adding it to the main vessel.
4. Decolorization Reaction (Contact):
Maintain vigorous agitation at the set temperature (90-110°C / 194-230°F).
Maintain the reaction (contact) time. Typical contact time is 15 – 30 minutes. Insufficient time leads to incomplete adsorption; excessive time can cause oil darkening (color reversion) or increased oil loss.
Towards the end of the contact period, reapply vacuum (or maintain it throughout) to further remove moisture and air.
5. Cooling:
After the designated contact time, circulate cooling water through the jacket to rapidly cool the oil to approximately 70°C – 80°C (158°F – 176°F). Cooling helps:
Stop the adsorption reaction, preventing over-bleaching or side effects.
Reduce oil viscosity for easier subsequent filtration.
Minimize the risk of oil oxidation at high temperatures.
6. Filtration & Separation:
Pump the mixture of oil and spent clay into filtration equipment (commonly plate-and-frame filter presses or leaf filters).
Filter under appropriate pressure to separate the decolorized oil from the spent clay cake containing the adsorbed impurities.
Key Points:
Filtration temperature should not be too low (generally maintained around 70°C / 158°F) to avoid increased viscosity and difficult filtration.
Filter pressure must be controlled carefully, starting low and gradually increasing, to prevent leaks or filter cloth damage.
The initially cloudy oil (first runnings) is usually recycled back for re-filtration.
After filtration, blow the filter cake with a small amount of steam or compressed air to recover trapped oil (cake blowing), minimizing oil loss (foots loss).
7. Post-Treatment:
The filtered decolorized oil may contain traces of clay fines (< 20 ppm) and usually requires polish filtration (e.g., bag filtration, cartridge filtration) for further removal.
Decolorized oil should proceed promptly to the next processing step (typically deodorization) to prevent oxidation or color reversion due to exposure to air and light.
II. Key Control Points & Considerations
1. Clay Selection:
Choose an activated bleaching earth grade specifically suitable for vegetable oil decolorization, particularly soybean oil. Effectiveness varies significantly between manufacturers and clay activities.
Consider clay moisture content (should be low, may require drying before use), particle size distribution (affects filtration rate and residual fines), and pH value (affects oil stability).
Lab-scale testing of new clay batches is recommended.
2. Moisture Control:
Both oil moisture and clay moisture must be strictly controlled. Excessive moisture is a primary cause of poor decolorization efficiency, increased oil loss, and difficult filtration. The system requires good sealing.
3. Temperature Control:
Temperatures that are too low result in slow adsorption and poor results; temperatures that are too high (>120°C / 248°F) risk oil oxidation, polymerization, reduced clay activity, and off-flavor formation. Precise temperature control is vital.
4. Vacuum Level:
Performing decolorization under vacuum helps remove air (oxygen) and trace moisture, preventing oil oxidation and improving decolorization efficiency and oil stability.
5. Agitation:
Ensure thorough and uniform agitation to maximize clay-oil contact and prevent clay sedimentation/clumping. However, avoid excessive agitation that introduces too much air.
6. Contact Time:
Contact time must be optimal. Excessive time increases oil loss and color reversion risk. Determine the best time through experimentation.
7. Filtration Efficiency:
Filtration is critical for production efficiency and oil loss minimization. Select appropriate filter cloths/paper, control filtration temperature and pressure, and clean filter cakes promptly. Incomplete filtration leads to hazy oil (clay residue), affecting downstream deodorization and final product quality.
8. Safety:
Activated bleaching earth is a fine powder. Observe dust control precautions (respirators, ventilation, prevention of dust explosions) during handling to avoid inhalation.
Take precautions against burns during high-temperature operations.
9. Spent Clay Disposal:
Spent clay cake contains approximately 20%-40% entrained oil (a source of oil loss) and adsorbed impurities. It is typically handled as waste, requiring consideration of environmental regulations (e.g., disposal by licensed contractors, or exploration of recycling/recovery methods).
III. Role of Activated Bleaching Earth in Decolorization
Primary Role: Adsorb pigments (decolorization), improving oil color and appearance.
Secondary Roles:
Adsorb trace soaps and metal ions (e.g., iron, copper).
Adsorb phospholipid breakdown products and residual phospholipids.
Adsorb oxidation products (peroxides, aldehydes, ketones).
Adsorb some off-flavor compounds.
Create better conditions for the subsequent deodorization step.
Summary:
Refining soybean oil using activated bleaching earth is a precise physical adsorption process centered on decolorization. Its effectiveness and efficiency depend on numerous factors: clay quality, degree of oil pre-treatment, operating conditions (temperature, time, vacuum, agitation), and filtration performance. Strict process control and parameter optimization are essential for producing decolorized soybean oil with a light color and stable quality. Following decolorization, the oil typically undergoes deodorization to remove volatile odor compounds before becoming a finished refined oil. 😊
How to Refine Rice Bran Oil Using Activated Bleaching Earth (Activated Clay)?
Rice Bran Oil Refining Process
I. Critical Pre-treatment Breakthroughs
1. Immediate Crude Oil Stabilization
Perform degumming within 2 hours of extraction: Add 0.05% oxalic acid (lipase deactivation) + 0.1% citric acid (metal chelation).
Target: Acid Value (AV) increase ≤0.5 mg KOH/g·24h.
2. Integrated Dewaxing-Degumming Technology
Stepwise Cooling: Crude oil → 45°C (113°F) (hot degumming) → Add 0.2% sodium silicate → Cool to 25°C (77°F) (colloid precipitation) → Secondary cooling to 10°C (50°F) (winterization, 48h).
Centrifugal Separation: Tricanter centrifuge (light phase: oil / heavy phase: gums / solid phase: waxes).
Wax residue: ≤100 ppm (meets Grade 1 oil standards).
3. Hybrid Physical-Chemical Deacidification
High-AV oil (AV>30): Enzymatic esterification first (lipase + glycerol, 60°C/140°F, 4h, 50% FFA reduction).
Followed by physical refining: Vacuum ≤1.5 mbar, 240°C (464°F) → FFA ≤0.1%.
II. Activated Bleaching Earth Innovations
1. Scientific Clay Blending System
Component Function Dosage Key Specifications
Acid-activated bentonite Adsorbs polar pigments (chlorophyll derivatives) 1.5~2.0% Acidity ≥0.8 mol H₂SO₄/L
Neutral attapulgite Preserves gamma-oryzanol 0.8~1.2% Pore size >5 nm, pH 6.8~7.2
Activated carbon Removes 3-MCPD esters 0.1~0.3% Iodine value ≥1000 mg/g
2. Low-Temperature Short-Duration Adsorption
Temperature: 85±1°C (185±2°F) (critical: >90°C/194°F accelerates oxidation in high-UFA oil).
Time: 15 min (gamma-oryzanol loss increases ~2%/min beyond this).
Vacuum: ≤50 mbar (O₂ <0.05%).
Dynamic Mixing: Variable-frequency agitation (300–500 rpm) prevents localized overheating.
3. High-Efficiency Filtration & Recovery
Filtration Media: Sintered stainless steel mesh (10 μm) + cellulose pre-coat.
Oil Recovery: Supercritical CO₂ extraction (25 MPa, 40°C/104°F) → Residual oil ≤5%.
Clay Residue: ≤10 ppm (UV-Vis detection).
III. Core Challenge Solutions for Rice Bran Oil
1. Gamma-Oryzanol Preservation
Clay Pre-treatment: N₂ activation at 150°C (302°F)/2h → Blocks acidic sites.
Post-bleaching Addition: Immediately add 0.01% rosemary extract (synergistic antioxidant).
Target: Final oil oryzanol ≥8000 ppm (≥80% retention vs. crude oil).
2. Trans-Fatty Acid (TFA) Control
Strict temperature monitoring: Deacidification ≤240°C (464°F)/90 min, bleaching ≤85°C (185°F).
Pre-deodorization addition of 0.005% tea polyphenols → Suppresses TFA formation.
Target: TFA ≤1% (GB limit).
3. Wax Re-precipitation Prevention
Rapid cooling to 25°C (77°F) → 12h tempering → Secondary filtration (captures re-dissolved waxes).
Turbidity target: ≤20 NTU (5h at 0°C/32°F).
IV. Circular Economy & Safety Enhancements
1. Spent Clay Valorization
Oryzanol Extraction: Ethanol Soxhlet extraction → 40% purity crude concentrate.
Fuel Conversion: Pelletized with rice husk → Calorific value ≥3500 kcal/kg (coal substitute).
2. Explosion Safety Design
Dust concentration monitoring: ≤20 g/m³ (CO₂ auto-extinguishing system).
Equipment grounding: Resistance ≤4 Ω (prevents electrostatic sparks).
Key Optimized Process Parameters
Stage Temperature Time Vacuum Key Additives
Stabilization 50°C (122°F) 0.5 h – Oxalic + Citric acid
Dewaxing-Degumming 10°C (50°F) 48 h – Sodium silicate
Enzymatic Deacidification 60°C (140°F) 4 h – Lipase + Glycerol
Bleaching 85°C (185°F) 15 min ≤50 mbar Acid-bentonite + Neutral attapulgite
Filtration 45°C (113°F) ≤1 h – Supercritical CO₂
Testing Standards:
Gamma-Oryzanol: HPLC-ELSD (GB 5009.xxx)
Wax Content: GB/T 5534-2019 Cold Test
3-MCPD Esters: ISO 18363-1:2015
This process achieves efficient decolorization (Lovibond Y≤20/R≤2.0) while maximizing gamma-oryzanol retention, increasing refined oil yield to ≥82% (vs. ≤75% conventional), and reducing trans-fatty acid formation by 40%.
*Technical notes:
Gamma-oryzanol preservation mechanisms are explicitly defined.
Safety protocols align with ATEX/IEC standards.
Dual units (°C/°F, mbar/MPa) included for global applicability.
Industry-standard terminology used (e.g., “tricanter centrifuge,” “winterization”).*
Learn More About Activated Clay
How To Definition Activated Clay Good Quality?
1. Higher decolorization ability. The activated clay has a stronger decolorization ability, the decolorization ability of the activated clay is mainly dependent on the adsorption capacity of the pore size for decolorization, the reaction to the index parameters can be seen as higher than the surface area, the activated clay can be up to 280 ㎡/g specific surface area, with a strong adsorption capacity;
2. Fewer impurities. The activated clay is made from deep natural bentonite, which has the characteristics of high purity, very low heavy metal content and very low sand content, which is more friendly for the production of food grade products;
3. Fast filtering speed. The filter speed of activated clay is lower than that of a similar activated clay, and the filter speed is faster under the same particle size. After comparison, the filter time of 100ml oil under pressure filtration is 30 seconds to more than one minute faster than that of similar competing products.
4. Lower residual oil rate after use. Because of the outstanding decolorization ability activated clay, it can reduce the amount of use, and the natural adsorption of less oil can be taken away when the amount of use is reduced.
How to Refine Coconut Oil Using Activated Bleaching Earth (Activated Clay)?
the activated bleaching earth refining process for coconut oil, addressing its low melting point, oxidation sensitivity, and phenolic compound preservation:
I. Key Challenges in Coconut Oil Refining
Property Refining Difficulty Risk
High Lauric Acid Hydrolysis at high temperatures FFA surge, flavor degradation
Natural Antioxidants Polyphenol loss from bleaching Reduced oxidative stability
Low MP (24°C/75°F) Filtration clogging Lower refining yield
II. Optimized Bleaching Process
- Critical Pre-treatment
Degumming & Dehydration
Add 0.1% citric acid solution (dissolved at 50°C/122°F), centrifuge to remove gums (phospholipids ≤10 ppm).
Vacuum dehydration (80°C/176°F at 50 mbar) to moisture ≤0.05%.
Pre-deacidification (Physical Method)
Short-path distillation (180°C/356°F, 0.5 mbar) reduces FFA to ≤0.3%.
- Clay Selection & Blending
Component Function Dosage Specifications
Neutral bentonite Adsorbs polar pigments 1.0~1.5% pH 6.5~7.0, pore size >4 nm
Activated carbon Removes heavy metals/3-MCPD esters 0.2~0.5% Iodine value ≥900 mg/g
Silica gel Protects tannins & phenols 0.1% Surface area ≥700 m²/g
Note: Acid-activated clays prohibited (prevent fatty acid hydrolysis catalysis).
- Low-Temperature Adsorption
Temperature: 70±2°C (158±4°F) (critical: >75°C/167°F accelerates lauric acid hydrolysis).
Vacuum: ≤40 mbar (O₂ <0.03%). Contact time: 20 min (polyphenol loss >15% per extra 10 min).
Agitation: Paddle-type low-speed mixing (100–150 rpm).
- Anti-Solidification Filtration
Heated Filtration System:
Jacketed leaf filter (maintain 65–70°C/149–158°F).
Pre-coat with diatomaceous earth (1.0 kg/m² to prevent clay penetration).
Oil Recovery:
Countercurrent washing with hot coconut oil (75°C/167°F) → Residual oil ≤18%.
Cake residual oil: Soxhlet extraction ≤12%.
III. Core Component Preservation
1. Polyphenol Retention
Add 0.01% rosmarinic acid (synchronized with clay addition to reduce polyphenol adsorption).
Target: ≥80% total polyphenol retention (Folin-Ciocalteu assay).
2. Oxidative Stability Control
Immediate post-bleaching cooling to <30°C (86°F).
Nitrogen storage (dissolved O₂ ≤1 ppm).
3. Fatty Acid Profile Protection
Max. process temperature ≤180°C (356°F) (prevent MCFA isomerization).
Trans-fatty acids: ≤0.5% (AOCS Cd 14d-99).
IV. Process Parameters & Testing Standards
Stage Temperature Time Vacuum Key Metrics
Degumming/Dehydration 80°C (176°F) 30 min 50 mbar Phospholipids ≤10 ppm
Physical Deacidification 180°C (356°F) 40 min 0.5 mbar FFA ≤0.3%
Bleaching 70±2°C (158±4°F) 20 min ≤40 mbar Lovibond Y≤15/R≤1.5
Filtration 65–70°C (149–158°F) ≤40 min – Clay residue ≤5 ppm
Final Product Testing:
Peroxide value: ≤1.0 meq/kg (ISO 3960).
Phytosterol retention: ≥90% (GC-FID).
V. Spent Clay Valorization
1. Polyphenol Recovery
Ethanol-water (70:30) extraction → Coconut polyphenol concentrate (cosmetic ingredient).
2. Energy Utilization
Pelletized with coconut shells → Fuel rods (calorific value ≥4,000 kcal/kg).
3. Eco-treatment
Biodegradation: Candida tropicalis fermentation (COD removal ≥85%).
Process Advantages
Yield increase: Total refining yield ≥88% (vs. ≤82% conventional).
Nutrient retention: Vitamin E >95%, total phenols >150 mg GAE/kg.
Safety: Full-process N₂ blanketing (dust <10 g/m³).
Applicability: Suitable for virgin (VCO) and industrial coconut oil (crude color Lovibond Y≤50/R≤8.0).
Technical Notes:
Industry-standard terminology (e.g., “short-path distillation,” “countercurrent washing”).
Dual units (°C/°F) and international test methods included.
Critical parameters explicitly defined for reproducibility.
How to Refine Sunflower Oil Using Activated Bleaching Earth (Activated Clay)?
Sunflower Oil Refining Process with Activated Bleaching Earth
I. Critical Pre-treatment Steps (Distinctive Features)
1. Deep Winterization (Dewaxing)
Cooling Protocol: Crude oil → 24°C (74°F) (coarse wax crystallization) → Hold 4h → Secondary cooling to 6–8°C (43–46°F) (48h)
Filter Aids: Add 0.1% diatomaceous earth + 0.05% cellulose (by oil weight) to enhance wax filtration efficiency
Target: Wax content ≤50 ppm (GB Grade 1 standard)
2. Enzymatic Degumming (Replaces Acid Refining)
Add phospholipase A1 (50–100 ppm), react at 45°C (113°F) for 2h → Hydrolyzes non-hydratable phospholipids to ≤10 ppm
Advantages: Reduces wastewater, increases oil yield by 3–5%
3. Mild Deacidification
Apply physical refining (steam distillation): Vacuum ≤3 mbar, temperature 220–240°C (428–464°F)
Condition: Crude oil FFA ≤3 mg KOH/g (alkali refining required if higher)
II. Activated Bleaching Earth Technology (Optimized for Sunflower Oil)
1. Clay Selection Strategy
Primary Adsorbent: Neutral bentonite (pH 6.5–7.5) 85% → Preserves tocopherols
Secondary Adsorbent: Acid-activated attapulgite 15% → Efficient chlorophyll removal (target ≤0.01 mg/kg)
2. Low-Temperature Dynamic Adsorption
Temperature Control: 88±2°C (190±4°F) (critical: never >95°C/203°F due to PV sensitivity)
Vacuum: ≤60 mbar (O₂ content <0.1%)
Staged Addition:
Step 1: Add primary clay (1.2%), agitate 15 min to adsorb primary oxidation products
Step 2: Add secondary clay (0.3%), agitate 20 min for chlorophyll removal
3. Filtration Innovation
Dual-Stage Filtration System:
Stage 1: Leaf filter with pre-coat (diatomaceous earth, 1.5 kg/m²)
Stage 2: Bag polish filter (5 μm rating)
Residual oil control: Cake oil ≤22% → N₂ blowback recovery technology
III. Core Challenge Solutions for Sunflower Oil
1. Chlorophyll Removal Difficulty
Measure crude oil chlorophyll (spectrophotometry):
2 mg/kg: Increase activated carbon to 0.5% blend
≤1 mg/kg: Reduce total clay to 1.0–1.5%
2. Tocopherol (Vitamin E) Retention
Clay pre-treatment: Dry at 150°C (302°F) for 2h → Reduce surface activity
Add 0.02% TBHQ (tert-butylhydroquinone) for synergistic oxidation protection
Target: ≥85% tocopherol retention in final oil
3. Peroxide Value (PV) Control
Full-process N₂ blanketing (degumming to bleaching)
Immediate post-bleaching cooling to <50°C (122°F) before storage
IV. Process Optimization & Cost Control
1. Clay Regeneration
Fluidized-bed calcination of spent clay (450°C/842°F, 1h) → 75% activity restored
Regenerated clay usage: ≤30% of fresh clay (only for pre-bleaching)
2. Inline Quality Control
Real-time NIR Monitoring:
Chlorophyll (700 nm peak)
Peroxide value (2900 cm⁻¹ band)
Automatic clay dosage adjustment (±0.3%)
Environmental & Safety Protocols
Spent Clay Valorization:
Recovered oil → Biodiesel feedstock
Calcined clay → Cement raw material (10% clay substitution)
Explosion Protection:
Bleaching vessels with N₂ inerting system (O₂ <8%)
Dust collectors equipped with spark detection + auto-extinguishing
Key Process Parameters
StageTemperatureTimeVacuumKey AdditivesWinterization6–8°C (43–46°F)48 h-Diatomite + CelluloseEnzymatic Degumming45°C (113°F)2 h-Phospholipase A1Bleaching88±2°C (190±4°F)35 min≤60 mbarNeutral Bentonite + Acid-Activated AttapulgiteFiltration45–50°C (113–122°F)≤1 h-N₂ blowback
This process achieves target color (Lovibond Y10/R1.2) while maximizing nutrient retention, controlling PV increase to ≤0.5 meq/kg. Refined oil must proceed to deodorization within 24h to prevent flavor deterioration.
Note: Industry-standard terms are used (e.g., “winterization”, “N₂ blanketing”, “fluidized-bed calcination”). Dual units (°C/°F) and precise technical descriptors (e.g., “acid-activated attapulgite”) ensure global applicability. Safety protocols align with ATEX directives.
How to Refine Peanut Oil Using Activated Bleaching Earth (Activated Clay)?
Process for Refining Peanut Oil with Activated Bleaching Earth
I. Critical Pre-treatment Steps
1. Raw Material Screening & Impurity Removal
Crude peanut oil must first pass through a vibrating screen to remove mechanical impurities (e.g., peanut skin fragments), followed by precision bag filtration.
Aflatoxin Risk Control: If raw peanuts carry high mold risk, implement a “pre-detoxification with clay” step before degumming (add 0.3%~0.5% activated clay to adsorb toxins).
2. Dehydration & Degumming
Heat oil to 70°C ±5°C (158°F ±9°F), add phosphoric acid (85%) at 0.1%~0.3% of oil weight for acid conditioning to destabilize non-hydratable phospholipids. Settle and remove gums (30–40 min).
Note: Peanut oil has low phospholipid content (~0.6%) but complex gums; ensure thorough hydration (add 2%~3% hot water) for complete degumming.
3. Neutralization (Deacidification)
Calculate alkali concentration (typically 12–18°Bé) based on Acid Value (AV); use 0.1%~0.3% excess alkali.
Temperature Control: Start at 60°C (140°F) → End at 80°C (176°F) to avoid excessive emulsification and neutral oil loss.
II. Core Activated Bleaching Earth Decolorization Process
1. System Preparation
Evacuate bleaching vessel to ≤100 mbar (hPa), load neutralized oil, and heat to 95–105°C (203–221°F). Avoid >110°C (230°F) due to peanut oil’s oxidation sensitivity.
2. Clay Selection & Blending
Recommended Formula:
Primary: High-activity attapulgite clay (strong adsorption, pH≈7, reduces color reversion).
Secondary: 10%–20% activated carbon (adsorbs aflatoxins, PAHs).
Total Dosage: 1.0%–3.0% (adjust based on crude oil color, e.g., 2.2% clay to reduce Red 3.0 → 0.8).
3. Dynamic Adsorption Process
Add clay in two stages:
First, add 70% clay, agitate 20 min;
Then add remaining 30% blended with activated carbon, agitate 15 min.
Vacuum Control: Maintain ≤50 mbar (h (158–167°F)** and transfer to a vertical leaf filter (pre-coat with diatom – Cake Handling: Recover trapped oil via countercurrent hot water (80°C/176°F) washing (residual oil ≤25%).
- Refining Considerations*
1. Pigment Characteristics
Peanut oil contains lutein and carotenes; select clays with 2–5 nm pores (e.g., acid-activated montmorillonite).
Post-bleaching color target: Lovibond 5.25″ cell: Y≤15, R≤1.5.
2. Flavor Preservation
Strictly control°F) to preserve characteristic flavor compounds (e.g., alkylpyrazines).
-time (LTLT) deodorization** (180°C/356°F for 2 hr) instead of high-temperature methods.
3. Enhanced Safety Protocols
Aflatoxin B1 Monitoring: Post-bleaching2716 limit (≤10 μg/kg)**; apply secondary clay treatment if needed.
**Metal Ion citric acid to chelate Fe/Cu with clay (reduce to ≤0.1 ppm).
Handling & Environmental Compliance**
1. Residual Oil Recovery
Extract oil from spent clay using n-hexane (residual oil ≤8%). ClayHazardous Waste Control**
Aflatoxin-contaminated clay must be treated with 5% NaOH solution before incineration to prevent toxin Optimization Recommendations**
**Online N real-time to minimize vitamin E loss from over-bleaching.
Clay Regeneration Trials: Calcination at 450°C (842°F) for 1 hr restores costs by 30% (validate oil residue levels).
Note: Peanut oil refining requires balancing decolorization efficiency and flavor retention. Optimize clay parameters via GC-MS flavor analysis to avoid “over-refining” and flavor degradation.
This translation maintains technical rigor while adapting terminology (e.g., “凹凸attapulgite clay*), units), and industry conventions (e.g., LTLT deodorization). Critical safety notesHs) and process specifics (two-stage clay addition, cake washing) are preserved with precision.
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