How to clean the sediment in the cross tubes of the final cooler

Cleaning Technology for Primary Coolers (1) Abstract: This article describes the use of chemical methods for cleaning primary coolers; as a result, the temperature of the gas after cleaning meets the requirements set by the process specifications, and good results have been achieved. Introduction: Our company’s coking plant’s condensing and ventilation section uses two horizontal-tube primary coolers. These coolers were put into operation in May, and they have performed well, keeping the gas temperature within the specified range. In June 2000, however, the gas temperature rose significantly, and the equipment resistance increased to around 8000 Pa. The cooling effect was particularly poor in the fresh water section – the gas temperature only decreased slightly, and increasing the amount of fresh water did not improve the cooling effect. This led to high gas temperatures, smoke emission from the coke ovens, and high fan loads, which affected the normal operation of subsequent processing stages. Inspections through manholes revealed that the heat exchangers were covered with oil deposits, with some areas between the tubes blocked by these deposits. Oil has poor thermal conductivity, resulting in high thermal resistance, which severely impaired heat exchange between fresh water and gas, thereby reducing the cooling efficiency of the primary coolers. To reduce equipment resistance, remove these oil deposits, lower thermal resistance, and improve heat exchange efficiency, we employed chemical methods for cleaning the primary coolers, achieving good results. The details are summarized below for reference by colleagues. In the condensing and ventilation section, it is necessary to remove impurities from the gas. The liquid containing tar that condenses in the first-stage primary cooler (referred to as light tar) contains some heavy tar as well, with a tar content of about 24%-26%. During the spraying process in the second stage, the tar content in the light tar increases further. As the gas cools, the temperature of the condensate drops, causing the viscosity of the light tar to increase and its fluidity to decrease. Abnormal operations such as failure to replace the light tar in time or using too low a spraying density can lead to heavy tar crystallizing and adhering to the tubes of the heat exchanger, thereby causing blockages in the primary coolers. 1.2.1 Process Issues: In the design, light tar containing tar, obtained from the condensation in the first-stage primary cooler, is used for removing impurities. However, the amount of condensate produced by this cooler is small, and its tar content is high. When the gas temperature in the first-stage primary cooler is high, more heavy tar ends up in the light tar. Using this tar for cleaning can easily cause blockages in the primary cooler, preventing the gas temperature from dropping. Additionally, the ability of the light tar to dissolve and absorb impurities decreases, leading to an increase in tar content after cooling, thus creating a vicious cycle of high gas temperatures and high tar content, which hinders purification in subsequent stages. 1.2.2 Areas for Improvement: The design of the primary coolers includes only steam cleaning as a means of removal. When there is a large amount of tar and other substances adhering to the heat exchangers, steam cleaning makes the oil deposits harder and stickier. When air is introduced, these oil deposits may oxidize and polymerize, making it difficult to completely remove them. Observations showed that these oil deposits are grayish-black, sticky, and semi-rigid substances. It was determined that they were likely composed of tar and its polymers. Accordingly, appropriate cleaning agents were selected, as shown in Table 1. Crude benzene was mixed with ammonia to create a 50% solution, which was then used to circulate and clean the primary coolers. Samples were taken every hour for inspection, and the cleaning process lasted 16 hours. As the viscosity of the benzene solution increased, it was drained into a mechanical clarification tank. If the cleaning results were not satisfactory, more crude benzene was added for further cleaning until the entire metal surface of the heat exchange tubes became visible

Using a high-pressure jet cleaner is a common method for cleaning the tubes of heat exchangers.

:victory: :victory:

There are specialized cleaning companies; you can sign an agreement to outsource the task, without having to worry about anything, and it doesn’t cost much either.