JPH1176965A - Removal of heaped sludge in oil storing tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for deciding the continuation or the end of a sludge removing work by conveniently and rapidly measuring the discharging state of a heaped sludge and efficiently removing the heaped sludge in an oil storage tank in a washing method in a gas in which the heaped sludge in the oil storage tank is dispersed and discharged by a fluid jetting in an inert atmosphere. SOLUTION: After adding a solvent having a compatibility with a discharging liq., having an affinity with a sludge and hardly generating emulsion, for example, a paraffin such as heptane, an arom. hydrocarbon such as toluene, a ketone such as methylethyl ketone and an oil such as kerosine, to the discharging liq., an insoluble content in the discharging liq. is separated by a solid-liq. separating operation, and a sludge content is acquired by measuring the amount of the insoluble content, and the discharging state is grasped. In order to acquire the sludge content, a calibration curve previously prepared and the amount of the insoluble content acquired by the method are compared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing sludge deposited in an oil storage tank, and more particularly, to an air cleaning method for dispersing and discharging accumulated sludge in an oil storage tank by fluid ejection in an inert atmosphere. The present invention relates to a method for easily and quickly grasping the state of discharge of sediment sludge.

[0002]

2. Description of the Related Art Representative methods for cleaning sludge deposited in an oil storage tank include an air cleaning method and an oil cleaning method. The aerial cleaning method means that after collecting the residual oil in the oil storage tank,
In this method, a lipophilic oil or a similar oil is jetted from a temporary nozzle in a storage tank in an inert atmosphere to pulverize sludge, and dispersed and flowed or dissolved in the oil to discharge. In addition, the in-oil cleaning method means that after collecting the residual oil in the storage tank, the cleaning oil is injected, and circulated in the oil under pressure by a temporary nozzle in the storage tank to dissolve the sludge in the oil. This is a method of dispersing and discharging. In any of the cleaning methods, a method is adopted in which cleaning nozzles are temporarily provided at appropriate intervals in a storage tank, and the nozzles are sequentially switched to perform cleaning.

[0003] When cleaning and discharging sludge deposited by such a method, it is one of the very important points for improving the efficiency of the cleaning operation to grasp the state of discharge of the sludge and determine when to end the cleaning. is there. That is, it is important to determine the dispersion and dissolution state of sludge simply and quickly on site. As this kind of determination method,
(1) Method of measuring sediment sludge from the roof of an oil storage tank (
Japanese Patent Publication No. 59-34439), a method for confirming that the level of the recovered oil tank is no longer elevated (Mitsubishi Oil Corporation)
Technical Document No. 66, 1986), and (3) a method of analyzing a discharged liquid or circulating oil (edited by Hisashi Hinata, cleaning and inspection of oil tanks) are known.

However, these conventional methods have the following problems. (1) The method of measuring the level of sediment sludge is that the actual measurement of the entire surface of the tank is practically impossible, the time required for the actual measurement is long, and the stored oil in the washing tank is crude oil under a nitrogen seal. In this case, the actual measurement of the height of the piled sludge is not a recommended determination method due to the danger of lack of oxygen and the like. The method of (2) for confirming that the level of the collected oil tank does not rise is the simplest method for confirming the completion of washing, but the sludge treatment state cannot be continuously tracked. As the item (3) for analyzing the discharged liquid or circulating oil, a viscosity measurement method and a wax content determination method are known. Although the viscosity measurement is a simple and quick method, sludge exhibiting thixotropic behavior has a problem in accuracy in a high sludge concentration region, and there are cases where the determination is erroneous.
In addition, the wax content determination method is a method in which Soxhlet extraction is performed using a solvent, followed by recrystallization with methyl isobutyl ketone to determine the amount, which requires a long time for measurement and requires skill in operation, and is simple and quick. This is not a good judgment method.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an aerial cleaning method in which sedimentary sludge in an oil storage tank is dispersed and discharged by a fluid jet in an inert atmosphere. By grasping,
An object of the present invention is to provide a method for efficiently determining the continuation or termination of a sludge removal operation and thereby efficiently removing accumulated sludge from an oil storage tank.

[0006] The present inventors have repeatedly studied the properties of the deposited sludge in order to solve the above problems, and as a result,
Focusing on the fact that sediment sludge contains a large amount of solvent-insoluble matter, a calibration curve was created in advance when cleaning the oil storage tank, and the amount of solvent-insoluble matter in the effluent was measured to determine the amount of sludge. The inventors have found that the determination can be made easily and completed the present invention.

[0007]

That is, the present invention relates to an aerial cleaning method for dispersing and discharging sediment sludge in an oil storage tank by ejecting a fluid in an inert atmosphere and discharging the sludge, which is compatible with the discharged liquid and has an affinity for the sludge. After adding a solvent that does not form an emulsion to the effluent, the insolubles in the effluent are separated by a solid-liquid separation operation, and the amount of the insolubles is measured to determine the sludge content. This is a method for removing accumulated sludge from an oil storage tank, characterized in that the state of discharge is grasped.The oil storage tank for obtaining a sludge content by comparing a previously prepared calibration curve with an insoluble content obtained by the above method. This is a method for removing accumulated sludge.

Hereinafter, the present invention will be described in detail. The sludge referred to in the present invention is a bottom deposit of an oil storage tank when mineral oil such as crude oil or heavy oil is stored, and is composed of mud, iron, moisture, paraffin, wax, asphaltene, resin, etc. Is an organic substance such as paraffin, wax, asphaltene, and resin. Examples of the type of sedimentary sludge include water in oil, wet sludge caused by asphaltene, dry sludge mainly caused by asphaltene, and wax-based sludge caused by paraffin in oil. The composition and properties vary depending on the type and storage condition of the oil.

The fluid for dispersing the sludge includes:
Normally, stored oil in a tank to be cleaned (referred to as friend oil) is used, and is hereinafter referred to as friend oil in the present invention. Most of the organic matter in the sludge is discharged in a dissolved state during washing in oil, while the organic matter in the sludge is mainly dispersed in friend oil in air washing. Exhausted from tank. The discharged liquid (referred to as circulating oil when used in a circulating manner, but the circulating oil in the present invention also includes circulating oil) is highly viscous because it contains sludge at a high pour point. For this reason, it is difficult to directly separate the oil component and the sludge component by a solid-liquid separation operation such as centrifugation. However, by adding a low-viscosity solvent that is compatible with the oil component in the effluent, has an affinity for sludge, and does not produce an emulsion, the viscosity of the effluent is reduced and the sludge component is easily reduced. Can be separated.

Examples of such a solvent include paraffins such as pentane, hexane, heptane, octane, nonane, and decane; aromatic hydrocarbons such as benzene, toluene, and xylene; acetone, methyl ethyl ketone (ME
Ketones such as K) and petroleum oils such as kerosene and light oil, etc., may be used alone or in combination of two or more. When measuring sludge derived from crude oil such as crude oil tank sludge from the viewpoints of compatibility with friend oil, correlation with sludge concentration and handling, M
EK and heptane are particularly preferred, and when measuring sludge derived from heavy oil such as heavy oil tank sludge, heptane, toluene, MEK and kerosene are particularly preferred as solvents.
The amount of the solvent added is 1 to 10 times, preferably 2 to 5 times the amount of the sampled effluent. Further, the generation of the emulsion may be determined by mixing and stirring the discharged liquid and the solvent and visually determining the mixture.

In order to measure the deposition sludge according to the present invention, a calibration curve is prepared in advance according to the following procedure. First, sludge and friend oil are sampled, respectively, mixed at various ratios to prepare a sludge-friend oil mixed oil having various sludge concentrations, and a predetermined amount of a solvent is added thereto. The insoluble matter is separated by a liquid separation operation, and the weight of the insoluble matter is weighed. A calibration curve can be created by expressing the relationship between the sludge content and the insoluble content obtained in this manner on a graph. Although the volume of the insoluble component may be measured instead of the weight of the insoluble component, the weight is preferable because the accuracy is higher.

Next, the discharged liquid is sampled from the oil storage tank in which the accumulated sludge is removed, a predetermined amount of a solvent is added thereto, and insoluble components are separated by a solid-liquid separation operation such as centrifugation. The amount of this insoluble content is determined. From the amount of insoluble matter thus determined, sludge content can be simply and quickly measured using the above-mentioned calibration curve.

In the method for removing deposited sludge according to the present invention, as a nozzle used for discharging the deposited sludge, various types of jet nozzles are manufactured by each manufacturer, but any nozzle having a predetermined cleaning ability can be used. Any nozzle may be used. Further, the fluid ejected from the nozzle may be any of crude oil, heavy oil-friendly oil and similar oils. The sludge may be discharged in a state dissolved in friend oil or in a slurry state dispersed and fluidized in friend oil. Further, when the sludge concentration is high, it is difficult to measure the sludge concentration by the viscosity method or the specific gravity method, but according to the present invention, it can be easily measured. The actual measurement of the sludge pile height, etc., is performed over a long period of time by interrupting the operation, but according to the present invention, the sludge concentration can be measured easily and quickly without interrupting the operation, and the sludge treatment status can be measured. It is easy to grasp or determine the end of cleaning.

[0014]

【Example】

Reference Example 1 Sludge and friend oil were sampled from a crude oil tank and a heavy oil tank, respectively, to prepare a sludge-friend oil mixed oil containing 30% by weight of sludge. 10 g of this mixed oil
And 40 ml of the solvent shown in Table 1 were weighed into a centrifuge tube, dispersed and mixed by ultrasonic waves for 10 minutes, and then centrifuged at 3000 rpm.
p. Centrifugation was performed for mx 10 minutes. Thereafter, decantation was performed to remove the upper solution. Again, the same operation was performed by adding 40 ml of the solvent, and the insoluble content was weighed, and then the proportion (% by weight) of the insoluble content in the sludge-friendly oil mixed oil was determined.
In addition, the proportion of insolubles in the friend oil was determined in the same manner. The results are shown in Table 1 (upper row: insoluble content of sludge-friendly oil mixed oil, lower row: insoluble content of only friendly oil).

[0015]

[Table 1]

From Table 1, it can be seen that in crude oil tank sludge, n-
Heptane, methyl ethyl ketone, etc., in heavy oil tank sludge, n-heptane, toluene, methyl ethyl ketone, kerosene, etc., are each compatible with friend oil, have an affinity for sludge, and are suitable as insoluble matter measurement solvents. Admitted.

REFERENCE EXAMPLE 2 From the tank to be cleaned, sediment sludge and crude oil used for cleaning were sampled, and the crude oil and sediment sludge were uniformly mixed at a predetermined ratio to prepare five known samples having different sludge concentrations. 10 g of this prepared sample and 40 ml of n-heptane were weighed in a centrifuge tube, and the sludge was dispersed and dissolved in n-heptane at 80 ° C., returned to room temperature, and centrifuged to measure insoluble matter. This was plotted to create a calibration curve shown in FIG.

Example 1 Next, at the time of aerial cleaning of the tank to be cleaned, the discharged liquid and the inlet oil (oil spouted from the cleaning nozzle) are sampled at predetermined time intervals, and insoluble components are removed in the same manner as in Reference Example 2. Asked,
The tank was washed while obtaining the sludge concentration from the calibration curve of FIG. 1, and the washing was completed when the sludge concentration in the discharged liquid became the sludge concentration of the inlet oil (see FIG. 2). The result of calculating the amount of discharged sludge from the flow rate of the inlet oil and the discharged liquid and the sludge concentration almost coincided with the amount of sludge calculated from the measured value of the height of the deposited sludge before cleaning. Further, hot water washing was continued and the manhole was opened and inspected, and the amount of residual sludge was small.

Comparative Example 1 Sludge and lipophilic oil were sampled from a crude oil tank, a mixed oil containing a known amount of sludge was prepared, and the viscosity and specific gravity at 40 ° C. were measured. The pour points of the sludge and the oil were 38 ° C. and 10 ° C., respectively.
The viscosity was measured using a B-type viscometer, and the specific gravity was measured by a float scale method.

[0020]

[Table 2]

From Table 2, it was found that when the sludge content of the effluent exceeded 50% by weight, the viscosity sharply increased and exhibited a thixotropic behavior. Therefore, the viscosity method cannot accurately grasp the sludge concentration in the high concentration region. Also, even with the specific gravity method, it is difficult to accurately grasp the sludge concentration for those having only such a small specific gravity.

[0022]

According to the present invention, there is provided an air cleaning method for dispersing and discharging by injecting a fluid in an inert atmosphere,
The discharge status of the accumulated sludge can be grasped simply and promptly, whereby the continuation or end of the sludge removal operation can be determined, and therefore, the accumulated sludge in the oil storage tank can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a sludge calibration curve.

FIG. 2 is a drawing showing a change with time of an insoluble component.

Continued on the front page (72) Inventor Kazuaki Kurosaki 46 at 46 Hama, Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka 80 Shin Nikka Environmental Engineering Co., Ltd.

Claims (5)

[Claims] 1. An air cleaning method for dispersing and discharging sediment sludge in an oil storage tank by fluid ejection in an inert atmosphere, wherein the solvent is compatible with the discharged liquid, has affinity with the sludge, and does not form an emulsion. After adding to the effluent, the insolubles in the effluent are separated by solid-liquid separation operation, the amount of insolubles is measured to determine the amount of sludge, and the state of discharge of accumulated sludge is characterized. A method for removing accumulated sludge from oil storage tanks. 2. The method according to claim 1, wherein the amount of sludge is determined by comparing a previously prepared calibration curve with the amount of insoluble matter determined by the method according to claim 1. 3. The solvent is a paraffin selected from pentane, hexane, heptane, octane, nonane and decane; an aromatic hydrocarbon selected from benzene, toluene and xylene; a ketone or kerosene selected from acetone and methyl ethyl ketone; The method for removing sediment sludge from an oil storage tank according to claim 1 or 2, wherein the oil is one or more kinds of petroleum selected from light oil. 4. The method according to claim 1, wherein the deposition sludge is a crude oil tank sludge, and the solvent is methyl ethyl ketone or heptane. 5. The method according to claim 1, wherein the sediment sludge is a heavy oil tank sludge, and the solvent is heptane, toluene, methyl ethyl ketone or kerosene.