Cleaning and liquid contact with solids – Processes – Hollow work – internal surface treatment
Reexamination Certificate
1999-06-14
2001-08-14
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Hollow work, internal surface treatment
C134S022120, C134S022160, C134S022170, C134S022190, C134S026000, C134S028000, C134S029000, C134S030000, C134S034000, C134S036000, C134S041000, C134S042000, C502S029000, C502S031000
Reexamination Certificate
active
06273102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to petroleum refining plants. More specifically, the present invention relates to method of cleaning and maintaining a petroleum refining plant, in which process equipment such as a furnace, reactor, heat exchanger and stripper are chemically cleaned, and rinsed after a softening catalyst agglomerated in the reactor and a surface of the catalyst softened by the chemical cleaning is coated and passivated, these processes being combined and conducted simultaneously.
2. Description of Related of Related Art
Crude oil is refined and various products and feed materials for chemical petroleum plant are manufactured in a petroleum refining plant, in which various catalysts are used. Catalayst activity deteriorates during continuous plants operation due to coking, poisoning or the like. Accordingly, periods repair to exchange the catalyst is necessary. The catalyst is exchanged by initially unloading the spent catalyst and subsequent loading of new catalyst.
The catalyst is mainly exposed to a reducing atmosphere during operation of the aforesaid petroleum refining plant. Therefore, when thus reduced catalyst is exposed to the air for replacement, the catalyst is oxidized to generate heat, thus causing possible ignition of carbide, sulfur and the like adhered to the catalyst during operation.
Therefore, after the catalyst beds are cooled from a high temperature (350 to 450° C.) to a lower temperature capable of conducting the unloading work (40 to 50° C.), the catalyst is dumped out in a nitrogen atmosphere by introducing the nitrogen gas into the reactor. Alternatively, a predetermined chemical is added while cooling the catalyst to coat the surface of the catalyst and passivate before unloading the catalyst.
In the aforesaid petroleum refining plant, since the catalyst reacts in a high temperature, the catalyst is agglomerated during the reaction by metal compound, sulfide, coke and other impurities. Thermal conductivity of the agglomerated catalyst is greatly deteriorated and the catalyst is not sufficiently cooled during cooling process. Accordingly, work efficiency for unloading the agglomerated catalyst is lowered, resulting in longer shutdown maintenance term.
In order to facilitate ways dumps out of the agglomerated catalyst, the catalyst is immersed in a surface active agent to soften the agglomerated catalyst.
However, since the waste water after softening the agglomerated catalyst contains compounds contaminating the environment, waste water treatment is necessary. Further, since the catalyst inevitably contacts the air, the dumping process is likely to be dangerous.
Contamination is generated in the process equipment, piping and on a surface of heat-transfer equipment (such as furnace, heat exchanger and stripper) during normal operation in the aforesaid petroleum refining plant.
When the contaminant is generated in piping, for example, the quality of the products deteriorates and production efficiency is lowered since the fluid flow is restricted. In an extreme case, the line may be choked and the devices may be damaged. When the contaminant is generated on the heat-transfer surface, excessive duty is required to the equipment to accelerate deterioration and abrasion of metal and to increase fuel cost.
Therefore, a work for removing the contaminant adhered to the piping and the heat-transfer surface of the process equipment so-called equipment cleaning, is required.
Various chemical cleanings by cleaning fluid are developed as the equipment cleaning.
The chemical cleaning is mainly composed of cleaning process for removing the contaminants from the surface of the equipment and rinsing process for forming clean fluid coat on the surface. In the chemical cleaning, the cleaning fluid is introduced into the equipment and is heated to a predetermined temperature. The heated cleaning fluid is circulated to remove the contaminant from the equipment. Subsequently, water rinsing fluid is used to rinse the equipment.
The aforesaid various methods, i.e., coating the surface of the catalyst to safely unload the catalyst in the air, softening the agglomerated catalyst to easily dump out, and chemical cleaning of the equipment to maintain the operation efficiency of the plant, are developed independently and are conducted as separate processes.
Accordingly, plant shutdown term gets longer, thereby deteriorating the production efficiency.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a cleaning and maintenance method for efficiently a conducting cleaning process of process equipment and pipings, unloading process of agglomerated catalyst, rinsing work of the process equipment and the piping in a petroleum refining plant, thereby reducing plant shutdown term, preventing stress-corrosion cracking by polythionic acid, improving production efficiency, ensuring work safety, and reducing production cost.
Specifically, it is noticed in the present invention that the catalyst is necessary to be cooled from a high temperature to a temperature capable of conducting the unloading work in order to dump out the catalyst. Accordingly, the entirety of the coating process of the catalyst, softening process of the catalyst, chemical cleaning of the equipment etc. are designed to be efficiently and effectively during the cooling time in the present invention, thereby reducing maintenance term of the plant.
More specifically, a repairing method of a petroleum refining plant according to the present invention is for a petroleum refining plant having various process equipment including equipment using various catalysts and pipings connecting the process equipment. The repairing method of the petroleum refining plant includes following steps of: first step of cleaning the various process equipment and the pipings and simultaneously softening agglomerated catalysts inside the process equipment; second step of rinsing the various process equipment and the pipings and simultaneously coating a surface of the softened catalyst by a coating agent; and third step of unloading the softened and coated catalyst from the process equipment containing the catalyst and simultaneously re-rinsing the various process equipment and the pipings.
In the above, the repairing method refers to conduct unloading of the catalyst, accompanying cooling, softening, coating of the catalyst, and rinsing of the equipment etc. The repairing method may be conducted regularly and/or irregularly. A predetermined chemical is preferably used for cleaning the process equipment and softening the agglomerated catalyst. However, the usage is optional. Another predetermined chemical is preferably used for rinsing the equipment and coating. The catalyst may be unloaded from the process equipment from an outlet provided to a lower portion of the equipment by virtue of gravity or, alternatively, from an upper manhole of the facility by vacuum.
In the present invention, since the process for chemically cleaning the equipment, softening the agglomerated catalyst, and coating the surface of the catalyst can be conducted in harmony in a single system, the advantages of respective process can be well performed so that the cleaning process of the process equipment and pipings, unloading process of the agglomerated catalyst, rinsing process of the process equipment and pipings can be efficiently conducted. Accordingly, the plant shutdown term can be reduced, thereby improving production efficiency.
In the above arrangement, the process equipment and the pipings are preferably cleaned by cleaning fluid having cleaning and softening effect introduced into light oil circulating in plant system, the process equipment and the pipings are preferably rinsed by a first rinsing fluid including light oil, and re-rinsed by a second rinsing fluid including water.
In the above arrangement, since the cleaning fluid having cleaning and softening effect introduced into light oil circulating in the system is introduced to the catalyst agglomerated in the reactor,
Kawakami Katsuhiko
Takano Jun-ichi
Xu Guiqing
Carrillo Sharidan
Lowe Hauptman & Gilman & Berner LLP
Softard Industries Co., Ltd.
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