Chemical Cleaning is the process of removing fouling deposits from process equipment with chemical solutions. The cleaning action may be entirely chemical in function (such as mineral acids used to degrade inorganic salt scales) or may be also 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. Today, specialized chemical mixtures have been developed to suppress foaming or enhance foaming, negate emulsion formation or create nearly unbreakable emulsions, remove scales without the use of acidic liquids, make fluids non-viscous or make them thick as a milk shake.

To new age companies where the chemical products are on the leading edge of technology, almost anything can be done given a definition of the requirements. This is no longer your grandmother’s “soap”. 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 investigated in a laboratory of skilled professionals who specialize in evaluating petroleum processing or chemical manufacturing foulants. Knowledge of the process can be most important in quickly understanding the nature of the debris and also 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 situ, 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 situ. In-line, but off-stream chemical cleaning is also now possible for equipment like banks of 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 also allowing 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). Typically, cleaning productsimport from 'react-helmet'; specifically designed for the petrochemical industry are mixed with circulating hot water at a temperature of between 80 and 90°C (176 – 194°F.) A chemical concentration of between 1% and 5% is usually employed depending on the nature of the hydrocarbons to be removed and/or the depth of foulant to be removed. In regards to the removal of hydrocarbon debris, a temporary, loose emulsion can be formed between the oil and water phases. The emulsion is then moved to a holding tank to allow the oil phase to quickly phase separate without the addition of supplemental chemicals to enhance the oil separation for recovery. Experience has shown that chemical cleaning can reduce the time required during shutdowns by 50% or more. The time saved and the resultant increase in plant availability can often more than offset the costs of chemical cleaning.