Horizontal tube indirect primary cooler

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As shown in Figure 16, the horizontal-tube primary cooler has a vertically rectangular-shaped shell, with the cooling water tubes arranged horizontally at an angle of 2° to the horizontal plane. The tube box on the outside of the tube sheet is connected to the cooling water pipes, forming a cooling water channel that allows for water supply in two or three stages. The Dawa Coking Plant uses a two-stage water supply system, providing low-temperature water and circulating water. The gas passes through the primary cooler from top to bottom. The cooling water enters from the lower part of each section; cold water is supplied to the lowest section in order to increase the heat transfer temperature difference and reduce the temperature of the gas at the outlet. Spraying devices are installed at the upper part of each section in the cooler’s shell side, where ammonia water containing coal tar is continuously sprayed to clean the coal tar and naphthalene deposited on the inner walls, while also helping to absorb a portion of the naphthalene from the gas. In a horizontal tube primary cooler, it is reasonable for the gas and condensate to flow simultaneously from top to bottom. Spray devices are installed at the upper parts of each section in the shell side of the cooler to continuously spray ammonia water containing coal tar, thereby cleaning the tar and naphthalene deposited on the outer walls of the tubes; this also helps to absorb a portion of the naphthalene from the gas as it passes through the absorber. The cross-tube coolers use steel tubes with dimensions of ϕ54mm×3mm; due to their small diameter and compact tube bundle, the water flow velocity can reach 0.5~0.7m/s. Due to the horizontal and dense arrangement of the cooling water pipes across the cross-section of the cooler, the gas flowing perpendicular to them experiences intense turbulence, which improves the heat transfer efficiency and enables uniform cooling; as a result, the gas can be cooled to an outlet temperature that is only 2°C higher than that of the inlet water. Since cleaning the water pipes of horizontal tube coolers is difficult, high requirements are placed on water quality; treated industrial water should be used.