Steam Coil in Palm Oil Mill Heating Sections

Steam Coil in Palm Oil Mill Heating Sections

In palm oil mills, steam coils are critical heat-transfer components in multiple heating sections, directly supporting core processes like fruit bunch pretreatment, oil extraction, and crude palm oil (CPO) refining. Their design and application are tailored to the mill’s harsh conditions—high temperature, humidity, and exposure to acidic/viscous palm oil derivatives.

The core mechanism relies on steam condensation heat transfer, which is far more efficient than sensible heat transfer (e.g., hot air). 

Here’s the step-by-step process:

Steam Inlet: High-pressure saturated steam (6–10 bar, 150–180°C) from the mill’s boiler enters the coil’s header, then distributes evenly into individual tubes.

Heat Release: Inside the tubes, steam condenses into water as it releases latent heat (≈2200 kJ/kg—this is the primary heat source for palm mill processes).

Heat Transfer: The released heat passes through the tube wall (and fins, if present) to the target medium (e.g., palm fruit bunches, crude oil, or process air).

Condensate Drainage: Condensed water (now near-saturated) flows to the coil’s lower header and is drained via steam traps—critical to prevent “water logging” (which reduces heat transfer efficiency by up to 40%).

Steam coils are integrated into 5 core mill sections, each with specialized requirements:

① Fresh Fruit Bunch (FFB) Preheating & Thawing

Purpose: Soften FFBs (especially frozen bunches in cold climates) to ease fruit detachment from stalks (stripping) and prepare for Steaming.

Coil Design: Bare tubes (to avoid fiber buildup) or low-fin-density coils; installed in enclosed preheating chambers.

Operating Conditions: Steam pressure ≈4–6 bar (140–160°C); heats FFBs from ambient temperature to 60–80°C.

② FFB Cooking (Palm Fruit Sterilization)

Purpose: The most critical heating step—cooks FFBs at high temperature to:

Destroy lipase enzymes (prevents free fatty acid (FFA) formation, which degrades oil quality).

Soften fruit mesocarp (facilitates oil extraction).

Kill microorganisms (prevents spoilage).

Coil Design: U-shaped or serpentine bare tubes (easy to clean); installed at the bottom/ sides of large cylindrical cookers (capacity: 5–20 tons/ batch).

Operating Conditions: Steam pressure ≈8–10 bar (170–180°C); cooking time 60–90 minutes; ensures FFB core temperature reaches ≥100°C.

③ Crude Palm Oil (CPO) Heating for Pumping & Clarification

Purpose: CPO is highly viscous at low temperatures (viscosity ≈100 cP at 30°C vs. 10 cP at 80°C). Heating reduces viscosity to enable:

Efficient pumping to clarification tanks.

Separation of oil from water and solids (decantation).

Coil Design: Double-pipe or shell-and-tube coils (direct contact with CPO); smooth inner tubes to avoid oil fouling.

Operating Conditions: Steam pressure ≈3–5 bar (130–150°C); heats CPO to 70–90°C.

④ Palm Kernel (PK) Drying

Purpose: After oil extraction, palm kernels (moisture content ≈20–25%) are dried to ≤10% moisture for storage or further processing (kernel oil extraction).

Coil Design: Finned tubes (maximize heat transfer to air); installed in hot air dryers (airflow is forced over coils to heat air, then blown over kernels).

Operating Conditions: Steam pressure ≈4–6 bar (140–160°C); heats drying air to 80–100°C.

⑤ Crude Palm Oil Refining (Deacidification/Deodorization)

Purpose: In the refining section, CPO is heated to high temperatures to remove impurities:

Deacidification: Heat CPO to 100–120°C to evaporate water and activate acid-neutralizing agents (e.g., caustic soda).

Deodorization: Heat refined oil to 220–240°C (under vacuum) to strip volatile odors (e.g., free fatty acids, aldehydes).

Coil Design: Stainless steel 316 coils (resists high-temperature corrosion); shell-and-tube type (for uniform heating under vacuum).

Operating Conditions: Steam pressure up to 12 bar (190°C) for deacidification; high-pressure steam (or thermal oil) may supplement for deodorization (since 240°C exceeds saturated steam temperature at standard pressure).