Chemical Cleaning is the process of removing fouling deposits from process equipment with chemical solutions.
advantages of chemical cleaning in refineries and petrochemical plants over mechanical methods. Describes steps necessary in analyzing deposits to be removed, chemical agents used in cleaning, effects of these agents on construction materials and cleaning of equipment in situ. Includes cleaning of columns, coolers, condensers, heat exchangers, boilers and drums. Also includes discussion of potential corrosion difficulties encountered in chemical cleaning. Describes auxiliary equipment needed.
The cleaning action may be entirely chemical in function (such as mineral acids used to degrade inorganic salt scales) or may be assisted by physical means such as steam or turbulent water flow. There have been many advancements made over the last decade in the chemistries used for conducting chemical cleaning operations.
Chemical cleaning operations can be conducted in such a way that will not lead to unacceptable pollution of the environment; air, water or soil. To determine the most suitable cleaning agent for a particular application, a representative sample of the fouling deposit should be analyzed. Knowledge of the process can be most important in quickly understanding the nature of the debris and in selecting the appropriate products for application in successful removal. If samples of the deposits cannot be obtained, then the experience of the chemical producer and/or the equipment owner should be requested. Many inorganic deposits can be removed using acidic or acid-based commercial cleaning agents, while alkaline solutions can be used for the removal of some organic deposits. Aromatic solvents with an emulsifying agent may remove some tars and polymer deposits. These basics are acceptable where equipment materials of construction will allow for strong acidic or strong alkaline contact and the handling of waste waters through sensitive waste water operations are not impacted. For equipment that cannot be moved and for systems of vessels and piping, etc., chemical cleaning can be carried out in site, using mobile facilities to circulate cleaning agents through the equipment. In towers or columns, steam is often the carrier of choice for distributing cleaning chemicals within the vessel in a process known as “steam phase” cleaning. Chemical cleaning can also be carried out by immersion of the equipment in a cleaning agent. This is suitable for small parts or for equipment containing deposits difficult to remove in site. stream chemical cleaning is also now possible for equipment like heat exchangers that once required having the heating bundles cut-out, removed to a cleaning yard and then high-pressure water blasted. On-stream chemical cleaning should be applied only after careful consideration since process temperatures may not be suitable and contamination by the cleaning agent could occur throughout the system. Specialized chemical cleaning solutions are becoming more widely used to improve the effectiveness and reduce the time needed for equipment decontamination during the process unit shutdowns. The primary objective of the decontamination phase of a shutdown is the removal of hazardous materials from vessels, piping and auxiliary equipment. In many cases, the primary purpose for equipment cleaning is to remove fouling debris that has severely impacted production capacities and is thus effecting revenue creation. However, specialized chemical cleaning solutions can also effectively clean refinery equipment by eliminating residual bulk hydrocarbons, as well as hydrocarbon films and sludge. Included, are chemical preparations that serve to safely decontaminate a vessel and allow for enhanced resource recovery of large percentages of valuable hydrocarbon streams for re-insertion into the refining process. This saves the owner the large expenses associated with hazardous materials waste disposal (very important in tank cleaning operations).

The advantages of chemical cleaning are:
• Cleaning can often be carried out without dismantling the equipment.
• Cleaning is more effective since all parts will be reached, resulting in more uniform cleaning.
• When carried out by competent personnel, the damage caused by chemical cleaning is minimal and generally less than that due to conventional mechanical cleaning. Damage induced by mechanical cleaning could enhance corrosion and/or fouling during subsequent operations.
• Cleaning is likely to reduce the time required for decontamination by 50% or more returning the equipment to productive operations more quickly than mechanical cleaning methods.
• Cleaning often generates much less waste materials than mechanical cleaning.
• The opportunity to recover large amounts of valuable hydrocarbon streams is accentuated with chemical cleaning and not as likely with conventional cleaning.