Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Reexamination Certificate
2002-10-11
2004-03-09
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
C134S022100, C134S022110, C134S022140, C134S022190, C134S029000, C134S036000, C134S040000, C134S042000
Reexamination Certificate
active
06702903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of washing petroleum equipment and a washing solution for use with the method.
2. Description of Related Art
Conventionally, it has been considered that water as well as surface-active agent are requisites for washing fluids used for washing petroleum equipment. When petroleum flows into sea, for example, surface-active agents are used to remove the petroleum because the surface-active agents can minutely disperse the petroleum in combination with seawater as a solvent.
As mentioned above, since water for the surface-active agent to be dispersed therein is a requisite for removing petroleum residue by the surface-active agent, it has been thought that the petroleum residue could not be removed by the surface-active agent in a waterless place.
However, in petroleum refining equipment, a part of petroleum is degraded to turn into macromolecule petroleum, which adheres on a wall of the equipment to be further firmly adhered (highly polymerized). The highly polymerized compound (referred to as petroleum residue hereinafter) becomes gradually thicker and thicker, which exerts bad influence on performance of the petroleum equipment. For instance, such petroleum residue significantly deteriorates heat exchange efficiency of the equipment.
Therefore, it is necessary to wash petroleum equipment for removing petroleum residue therefrom. However, when a water-containing washing solution is used, the petroleum equipment may be damaged or bad influence is caused on products on account of residual water. Accordingly, petroleum-rinsing or drying process has to be conducted after washing the petroleum equipment with the water-containing washing solution. As a result, the total equipment downtime is lengthened.
SUMMARY OF THE INVENTION
In the following description, the terms “washing solution” and “circulated washing solution” are equivalent and used interchangeably to denote a solution being circulated in petroleum equipment to wash petroleum residue or any other build-ups off the walls of the petroleum equipment.
The present invention has been reached based on the finding that surface-active agents are effective in finely dividing and dispersing the petroleum residue for removal, even in petroleum equipment having no water therein. In other words, washing solutions that contain no water can be used to effectively wash petroleum equipment.
A method of washing petroleum equipment according to an aspect of the present invention is characterized in using a compound of a surface-active agent and petroleum as a washing solution for the petroleum equipment.
A method of washing petroleum equipment according to another aspect of the present invention comprises the steps of:
a) preparing a non-aqueous washing solution consisting of a surface-active agent and petroleum, the petroleum comprising at least one selected from the group consisting of kerosene, light gas oil, vacuum gas oil and light cycle oil fraction;
b) introducing the washing solution inside the petroleum equipment; and
c) circulating the washing solution to wash the inside of the petroleum equipment.
Since the washing solution contains no water, there is no need for a rinsing or drying process as required by the conventional arrangement, thus simplifying the whole process and reducing the total downtime of the equipment.
The concentration of the surface-active agent in the washing solution is preferably from about 1 to about 20 volume percentage.
When the concentration of the surface-active agent is less than 1 volume percentage, the washing effect is significantly deteriorated. On the other hand, when the concentration of the surface-active agent exceeds 20 volume percentage, the washing effect increases only slightly, which does not justify the cost of the washing solution.
The temperature of the washing solution during the washing process is less than the boiling point of the solvent of the surface-active agent, which is preferably and normally between the normal temperature and 200° C. The non-aqueous washing solution may preferably be heated while being circulated inside the petroleum equipment thus enhancing washing efficiency.
According to the method of the present invention, at least one property of the washing solution being circulated inside the petroleum equipment may preferably be monitored, and the concentration of the surface-active agent in the non-aqueous washing solution will preferably be adjusted, e.g., increased, when the monitored property or properties do not satisfy a predetermined standard.
The properties may be monitored in any suitable manner, such as visual observation of the washing solution and/or evaluation using a measuring device. The predetermined standard may be set in any manner, considering the type of the petroleum equipment to be washed, acceptable downtimes for the petroleum equipment, the properties of the washing solution etc.
The monitored properties of the non-aqueous washing solution preferably include at least one of the hue acid value and the residual carbon content of the circulated washing solution.
According to the method of the present invention, even when the non-aqueous washing solution does not show sufficient performance for washing the petroleum equipment at the initial stage of the washing process, the concentration of the surface-active agent can be adjusted, e.g., increased, during the washing process to attain desired washing efficiency.
In accordance with an embodiment of the present invention, a non-aqueous washing solution having a predetermined concentration, i.e., percentage by volume, of the surface-active agent may be directly introduced into the equipment and circulated therein until the end of the washing process without being changed or adjusted.
However, it is more preferable and flexible if the concentration of the surface-active agent in the non-aqueous washing solution can be adjusted during the washing process. For this purpose, an initial non-aqueous washing solution containing the surface-active agent of a concentration less that the predetermined concentration is first loaded into the equipment to be circulated therein. Thereafter, another, condensed non-aqueous washing solution having the surface-active agent of a concentration greater than the predetermined concentration is introduced in the petroleum equipment. Thus, a resulting washing solution which is a mixture of the initial non-aqueous washing solution and the condensed non-aqueous washing solution is circulated in the petroleum equipment. The resulting washing solution contains the surface-active agent of a concentration higher than the concentration of the initial washing solution but lower than the concentration of the condensed washing solution. Continually introducing the condensed washing solution into the petroleum equipment at, e.g., regular intervals will gradually increasing, or adjusting, the concentration of the surface-active agent in the resulting washing solution being circulated. Simultaneously, one or more properties of the circulated washing solution is/are being monitored for washing efficiency. When a desired washing effect has been reached, the introduction of the condensed washing solution is stopped. The introduction of the condensed washing solution may also be stopped when a maximum desired concentration of the surface-active agent, e.g., 20% by volume, in the circulated washing solution has been reached. The condensed washing solution and the initial washing solution preferably contain the same components, i.e., the same petroleum and surface-active agent, only in different concentrations.
Another embodiment of the present invention can be implemented in substantially the same manner as immediately described above, except that petroleum, instead of the initial washing solution, is introduced into the petroleum equipment. In other words, this embodiment is a particular case of the embodiment immediately described above when the initial washing solution contains no surface-active agent
Hosokawa Hirozumi
Kawakami Katshuiko
Carrillo Sharidan
Lowe Hauptman & Gilman & Berner LLP
Softard Industries Co., Ltd.
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