The packing flatness of distillation column is the key installation index to determine the separation efficiency. Once the packing layer has obvious inclination or uneven height, the liquid will gather to the low side under the action of gravity, forming local flooding; While the high side packing is in the dry zone state, and the gas-liquid can not effectively contact against the current, which is equivalent to the complete failure of this part of packing.
The measured data of the industry show that when the levelness deviation of the upper end face of the packing exceeds d/1000 and more than 4mm, the mass transfer efficiency can be reduced by more than 30%. For regular packing, the HETP increases by about 5%~8% for every 1mm increase in the levelness deviation of the packing layer per meter, which means that the corresponding proportion of packing height or reflux ratio needs to be increased to achieve the same separation purity. Taking the air separation distillation column as an example, if the designed oxygen extraction rate is 99.6%, and the efficiency decreases by 20% due to uneven packing, the oxygen extraction rate may fall below 97%, which directly affects the purity and yield of the product.
Suggestions for on-site operation and maintenance disposal: first, open the manhole after shutdown, check the flatness of the filler layer one by one with a level ruler, and level and reassemble the inclined part; The second is to check the levelness of the support grid. When the deviation exceeds ± 3mm/m, it needs to be leveled with sizing blocks; Third, for bulk packing, after each 0.5-1 meter of filling, use a rubber hammer to gently tap several circles along the tower wall to promote its settlement and compaction; Fourth, the verticality of the tower body shall be regularly detected to ensure that the deviation per meter is ≤ 1mm. The packing efficiency is designed, but whether it can be brought into play depends on the installation accuracy.
