Specialized Tube-in-tube Heat Exchanger for Tobacco Factories

Concentric Tubing

- Inner Tube: Carries liquid media (cold water/hot water/ethylene glycol circulating water)

- Outer Tube: Carries high-temperature, humid tobacco flue gas/process hot air (flue gas flows through the annular channel)

Cigarette factory drying machines, tobacco curing machines, stem drying machines, and boiler exhaust gas face three major harsh operating conditions:

1. High Humidity + Acid Corrosion: The flue gas contains a large amount of water vapor and organic acids from tobacco, which easily condense and corrode ordinary copper tube fins below the acid dew point;

2. Contains Tobacco Dust and Tar Particles: Easily clogs fin gaps;

3. Wide Temperature Range: Drying exhaust gas 110~180℃, boiler flue gas 150~250℃, large temperature difference, significant thermal stress deformation.

Defects of Ordinary Single-Pipe Finned Heat Exchangers: Flue gas directly erodes the thin-walled fins, leading to dew point corrosion perforation, difficult-to-clean ash accumulation, and leakage due to thermal expansion and contraction.

Advantages of Double-Pipe Finned Heat Exchangers: Flue gas flows only within the double-layer annular gap, the medium water is completely isolated in the inner tube, the outer sleeve is thickened for corrosion protection, and the fins only serve as external auxiliary heat exchange enhancements, significantly reducing the risk of corrosion.

Scenario 1: Waste Heat Recovery from Tobacco Drying/Sheet Baking Machines (Most Mainstream)

1. Process: High-temperature, humid flue gas from tobacco drying (120~160℃) → Circulation through the annular gap of the sleeve; Cold water absorbs heat in a counter-current flow within the inner tube;

2. Functions:

- Cold water is heated to 50~70℃ for workshop heating, process water preheating, and hot water for tobacco leaf rehydration;

- Flue gas is cooled to below 60℃, condensing water vapor to remove white smoke, reducing white smoke emissions;

3. Benefits: Waste heat recovery per tobacco drying machine is 25~32kW, reducing steam energy consumption by 18%~30%.

Scenario 2: Preheating of Fresh Air for Processing (Winter Workshop/Tobacco Storage Room)

Recovering waste heat from boiler flue gas, heating circulating hot water through sleeve fins, and then preheating low-temperature outdoor fresh air with air fin coils, stabilizing the temperature and humidity of tobacco leaf storage and preventing tobacco leaves from drying and crumbling.

Scenario 3: Flue Gas Conditioning and Cooling (Pre-desulfurization Cooling)

Boiler exhaust gas at 140℃ enters the jacketed tube fins. Cold water is circulated inside to reduce the flue gas temperature to 85~95℃, optimizing dust removal and desulfurization efficiency. The double-layered structure of the jacket prevents cold water leakage and contamination of the flue gas system.

Scenario 4: Low-Temperature Condensation and Dehumidification (Deep Recovery of Latent Heat from Exhaust Gas)

The flue gas is cooled below the dew point, and water vapor condenses, releasing latent heat. The jacketed tube structure can withstand a large amount of condensate erosion. A water collection tank at the bottom collects the condensate for reuse in cleaning equipment.