How To Choose The Finned Tube Heat Exchanger for Palm Oil Production?

How to Choose the Right Finned Tube Heat Exchanger for Palm Oil Production?

Palm oil production involves heating, cooling, condensation and other links, the heat transfer objectives of different links vary significantly, need to be clear about the specific purpose:

Heating (such as palm fruit cooking, oil preheating): low-temperature media (palm fruits, cold palm oil) need to be heated to a specific temperature (usually 60-120 ° C), most of the heat source is steam or high temperature heat transfer oil. At this time, the heating rate and temperature uniformity of the heat exchanger need to be prioritized to avoid local overheating leading to the deterioration of fats and oils.

Cooling (e.g. after refining oil cooling): high temperature palm oil (e.g. after deodorization 180-240℃) needs to be cooled down to the storage temperature (30-50℃), and the cooling medium is mostly cold water or cold air. The cooling medium is mostly cold water or cold air. Attention should be paid to the cooling efficiency to avoid oxidization of oils and fats staying under high temperature for a long time.

Condensation (e.g. solvent recovery, steam condensation): the steam generated in the process (e.g. solvent steam, water vapor) is condensed into liquid, and it is necessary to ensure the thoroughness of condensation and reduce the loss of media (e.g. solvent leakage will increase the cost and pollute the environment).

Palm oil production media involved (palm oil, steam, solvents, cleaning fluids, etc.) characteristics directly affect the heat exchanger material and structural design:

Palm oil characteristics:

easy to solidify at room temperature (melting point of 24-39 ° C), high temperature viscosity is reduced, but may contain pulp residues, gums, and other impurities, easy to be scaled in the pipe wall.

Refining process may come into contact with acid, alkali (such as caustic soda for deacidification), there is a certain corrosiveness.

Countermeasures: The base tube should be made of corrosion-resistant material (e.g. 304 stainless steel, to avoid iron ion contamination of oil and grease); the fins should be tightly fitted with the base tube (e.g. high-frequency welding process), to minimize scaling at the interstices; if there are many impurities, a large fin pitch (e.g. 8-12mm) is required to reduce the risk of clogging.

Characteristics of heat/cold source:

Steam: high temperature (150-200℃), medium pressure (0.5-1.0MPa), pressure resistance of base tube (e.g. seamless steel tube);

Cold air: clean but low heat transfer coefficient, need to increase the area of fin (e.g. high fins, fin height of 15-25mm);

Cold water: may contain minerals (easy to scale), need to consider the design of shell process easy to clean (e.g. removable shell).

The finned tube is the core of the heat exchanger, and its parameters (material, type, structure) directly determine the performance:

Base tube material: Priority is given to 304/316 stainless steel (food-grade, resistant to oil and grease and weak corrosion); for cost-sensitive, high-temperature heating processes, carbon steel can be used (but requires regular anticorrosion treatment).

Fin Material: Aluminum fins (high thermal conductivity, low cost, suitable for low and medium temperature cooling); Copper fins (better thermal conductivity but high cost, suitable for high-precision temperature control); Stainless steel fins (corrosion-resistant, suitable for acid and alkali condensation link).

Fin type: spiral fins (large heat transfer area, good turbulence effect, suitable for high viscosity media such as palm oil heating); ring fins (strong structure, easy to clean, suitable for cooling links containing impurities).

Fin pitch: small pitch (3-6mm): large heat transfer area, suitable for clean media (e.g. steam condensation); large pitch (8-15mm): anti-clogging, suitable for cooling of palm oil containing impurities or prone to scaling.

Fin height: high height (15-30mm): increase the heat transfer area, suitable for low heat transfer coefficient media (such as cold air cooling); low height (5-10mm): compact structure, suitable for space-constrained heating link.

Heat transfer area is the core parameter of heat exchanger selection, which needs to be calculated according to the heat load formula:

Heat load Q = mass flow rate × specific heat capacity × temperature difference (when heating/cooling); or Q = condensate volume × latent heat of vaporization (when condensing).

On this basis, combined with the heat transfer coefficient (need to take into account the effect of scaling, usually take the empirical value: air cooling 10-30 W / (m ² / ℃); water cooling 500-1000 W / (m ² / ℃)), the calculation of the required area of heat transfer, and reserve 10% - 20% of the margin (to cope with fluctuations in the process or scaling caused by the decline in efficiency).

Initial cost: stainless steel > carbon steel + corrosion protection; copper fins > aluminum fins, to be selected according to process life (usually 10-15 years) and corrosion risk.

Operating costs: high efficiency heat exchanger (such as high fins, dense pitch) initial investment is high, but low energy consumption (such as cooling can reduce the fan / water pump power); need to calculate the whole life cycle cost (investment + energy consumption + maintenance), rather than just look at the unit price.

In actual selection, need to be adjusted with specific capacity (e.g. 1000 tons of palm fruit per day vs. 100 tons), local climate (e.g. air-cooling is more economical in the tropics) and other details.