In industries such as oil, gas and petrochemicals, it is always trying to prevent sediment formation using various methods in equipment such as heat exchangers and steam boilers. In this context, there are a lot of expenses for chemical substances and additives. But most industrial heat exchangers are subjected to sedimentation for various reasons, such as low water quality in different areas. These sediments are mostly formed in the transducer tubes. To reduce the losses of the sediment phenomenon, the converter should be continuously monitored and cleaned.<\/p>\n
The Tube Shell Converters Association 1 recommends that the design of the exchangers always be allowed for a significant amount of material in the process of production. But in all cases, the disassembly should be performed at appropriate intervals.<\/p>\n
Suspended fine particles;
\nSediment caused by corrosion;
\nBiological deposition;
\nSediment due to the formation of solid crystals;
\nPrecipitation due to a chemical reaction;
\nSediment due to temperature changes such as freezing;<\/p>\n
Suitable cleaning times for heat exchangers
\nGiven the fact that heat exchangers are an important part of different processes, if the formation of deposits in them and to maintain the amount of heat transfer, it is necessary to increase the temperature or hot water flow. This increase in temperature or flow can lead to an increase in the cost of input energy into the process or to reduce production. In both cases, costs are imposed on the process that they call the cost of sedimentation. To make appropriate economic decisions, these costs must be calculated at different times and in proportion to the amount of heat transfer from the sediment.<\/p>\n
In general, the cleaning time should be calculated according to the amount of sedimentation effect on the process, in order to achieve the optimal amount of cleaning time. Cleaning at low intervals will increase the total time spent on the repair of the converters. Therefore, this, in addition to increasing cleaning costs, also reduces overall revenue by reducing production of integrated products. On the other hand, cleansing at long intervals due to increased sedimentation increases the need for energy to maintain fluid temperatures. Additionally, in some cases overload congestion can interfere with the production of an industrial complex. So, to increase the efficiency of the heat exchangers, they must be cleaned at certain intervals. Desalination, the internal surface of the tubes returns to its original state (which is actually the surface of the metal) and usually increases its durability. Because after every cleaning, a thin layer of oxide is formed at the pipe surface, which is an agent of corrosion prevention. The cleaning of the converter tubes is done only if the converter is not working.<\/p>\n
Sediment removal methods
\nVarious methods are used to clean heat exchangers, including mechanical and chemical washing. Generally, a variety of sediment removal methods are:
\nMechanical cleaning;
\nChemical purification;
\nEach of these methods is briefly explained below.<\/p>\n
Mechanical methods
\nTypes of mechanical deposition techniques are:<\/p>\n
Create reverse flow:
\nA method of dewatering, stopping and closing the unit and cleaning its units. But every time the unit is closed and re-launched, a lot of energy, raw materials, time, product production, etc. are wasted. Because of this, there is a simpler way that can be used and effective many times before the unit is stopped for repairs. In this way, it will be reversed temporarily and for only a few minutes to enter and exit the cooling water. This is done through the opening and closing of several milk. Much of the sediment is removed by this method, and for a while, heat transfer can be made close to the design value. Of course, each time this work is done, the heat recovery from the previous runback will be less. The same is true of restoring the pressure drop of water. Depending on the design of the cooling, one of the two factors of reducing the heat transfer or increasing the pressure drop can have a more negative effect on the work of the relevant chemical unit, but usually the reduction of the heat transfer is determined earlier. To facilitate the creation of reverse flow, in particular, in units with more cooling capacity, a quill valve is used.<\/p>\n
Water jet method:
\nAmong different washing methods, the use of high pressure water is more common. Wash with water is time consuming because the pressure (jet) of the water gently cleans the tubes. It should be noted that in this method of cleansing, lack of comfort and precision, the pipes or their retaining plate can be destroyed. Of course, most of these damages are revealed after the reboot is restarted.<\/p>\n
Disadvantages of water pressure method (water jet)<\/p>\n
Dehydration using water pressure Although in many cases it is a suitable method, there are some disadvantages and limitations that are:<\/p>\n
Hydrophysical mechanics:
\nThe mechanical hydrophobic method is used for very hard sediments. Under normal conditions it is very difficult to separate these sediments. For this reason, in this method, first the deposits in the pipes are separated by appropriate drills and special brushes, and then they are used to extract a high pressure air compressor.<\/p>\n
The advantages of this method include the high safety of its tools for work inside the complex, speed, power and efficiency, long-range, low cost, the possibility of making and supplying all its accessories inside the country, the possibility of using two nozzles At the same time, it’s possible to work with the remote operator, easy and fast maintenance, high quality and robustness.<\/p>\n
Disadvantages of this method:<\/p>\n
The tool used in this method is not flexible due to its strong tube of power transfer, collisions with hard deposits, fracture of the drill and damage to the inner wall of the pipe. Because of the small pores of water drain from the tip of the tool, with increasing number of pores, friction and thermal stress increase, thus breaking the drill and damaging the tube.<\/p>\n
Abrasive spray method:
\nIn this method, by means of a compressed air gun, cartridges are fired into the tube. The abrasives are plastic, they sweep the pipe at the speed of the inner wall. Using sponge bullets with a flat surface in the heat exchanger tubes has better results in reducing sedimentation. The diameter of the sponge bullets is slightly larger than the inner diameter of the tube, so that a bullet is fired every 5 to 10 minutes.<\/p>\n
Disadvantages of this method:<\/p>\n
This method is not suitable for half-drawn or well-drained tubes and also for hard deposits.<\/p>\n
Chemical methods
\nFor the chemical washing of equipment, it is first necessary to determine the type of sediment (including deposits from process fluids or corrosion deposits). In this method, depending on the type of sediment, a variety of chemicals are used. In the chemical-acid-based method, corrosion inhibitors are used to prevent undesirable effects of acid on the surface of the metal. The acid used in these materials, depending on the sediment and metallurgy of the system, may be mineral, organic, or a mixture of both. Table 1 lists the acids that play the most role in chemical washing. Each sediment should be removed from the surface with regard to the chemical nature and physical properties. Most sedimentation solutions are based on organic and mineral acids. Among the acidic acids, HCl and H2SO4 acids are most widely used. Organic acids are also commonly used in citric acid, acetic acid and EDTA.<\/p>\n
Hydrochloric acid is one of the most important acids used in chemical washing. The choice of corrosion inhibitor depends on the concentration, temperature, acid recovery time, metallurgy of the system and the type of acid.<\/p>\n
Disadvantages of chemical wash ,This method has some disadvantages:<\/p>\n
Descaling In industries such as oil, gas and petrochemicals, it is always trying to prevent sediment formation using various methods in equipment such as heat exchangers and steam boilers. In this context, there are a lot of expenses for chemical substances and additives. But most industrial heat exchangers are subjected to sedimentation for various reasons,…<\/p>\n","protected":false},"author":1069,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0},"categories":[5],"tags":[],"_links":{"self":[{"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/posts\/7136\/"}],"collection":[{"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/posts\/"}],"about":[{"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/types\/post\/"}],"author":[{"embeddable":true,"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/users\/1069\/"}],"replies":[{"embeddable":true,"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/comments\/?post=7136"}],"version-history":[{"count":0,"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/posts\/7136\/revisions\/"}],"wp:attachment":[{"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/media\/?parent=7136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/categories\/?post=7136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mitreh.com\/en\/wp-json\/wp\/v2\/tags\/?post=7136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}