I. Why are primary coolers prone to blockage?

• Condensation mechanism: During the cooling of coke oven gas,

  • Tar vapor condenses into droplets,

  • Naphthalene desublimates from gas to solid,

  • Dust particles also adhere.

• Accumulation effect: These substances deposit on pipe walls, forming layers that gradually thicken and finally cause blockage.

• Temperature factor: At lower temperatures, tar becomes more viscous and less fluid, which further aggravates the blockage.

II. Solution concept

• Spray an “ammonia liquor + tar mixture” into the middle and lower sections of the primary cooler to dissolve naphthalene and deposits into the spraying liquor, then send them to the separation unit for treatment.

• Key factors:

  • Composition ratio of the spraying liquor (tar content and naphthalene solubility),

  • Spray uniformity and density.

III. Core calculation conclusions

• Middle section outlet temperature: about 40 ℃

  • Tar in the self-generated condensate contains about 19% naphthalene, below the solubility limit (≈35%).

  • No extra tar supplementation is needed.

• Lower section outlet temperature: about 21 ℃

  • Tar in the self-generated condensate contains about 26% naphthalene, above the solubility limit (≈20%).

  • Continuous addition of product tar is required, otherwise naphthalene will precipitate, blocking pipelines and downstream equipment.

 According to the group standard, the tar content of the lower-section spraying liquor must be maintained at 40% ±10%.

IV. Operating essentials

• Middle section: Circulate and spray self-generated condensate only.

• Lower section: Continuously add product tar; control the tar content of the spraying liquor at 40% ±10%.

• Spraying requirements: Ensure proper spray density and uniformity; regularly inspect nozzle condition.

• Temperature control: Maintain a proper gradient to avoid premature naphthalene precipitation in the middle section.

• Cleaning management: During offline cleaning, use hot ammonia liquor; send the cleaning liquid for separate treatment, do not recycle it.

• Prohibited practice: Do not replace self-generated condensate with liquid from the separation unit, as this disrupts proportion and temperature, reducing effectiveness.

V. Benefits

• More stable primary cooler operation: Long-cycle, blockage-free.

• Cleaner coke oven gas: Less visible smoke emissions.

• Energy savings: Lower blower power consumption, stable low resistance.

• Safer downstream operation: Reduced risk of naphthalene re-deposition in desulfurization, benzol-washing, and other units.