JPS6146037B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preventing the accumulation of petroleum sludge,
In particular, it relates to a method for preventing accumulation of crude oil sludge. Oil, the most commonly used energy source in Japan today, is almost entirely imported from overseas and stored in huge tanks. Looking at the size of these tanks, just under 40% of them are ultra-large tanks with a capacity of 100,000 Kl or more each, and the average capacity is approximately 60,000 KL. Meanwhile, a long-term oil stockpiling plan is underway to stabilize energy supplies, but the tanks used in this plan are likely to be even larger. A major problem when storing oil, especially crude oil, is the problem of sludge accumulating at the bottom of tanks, as well as various safety measures. capacity 10
In the case of 10,000Kl tanks, sludge may accumulate several meters from the bottom of the tank, and the amount of sludge can reach over 10,000KL. The accumulation of sludge not only reduces the actual storage capacity of the tank, but also causes clogging of oil pipes, pumps, etc. attached to the tank. This sludge has a complex composition consisting mainly of paraffins with large molecular weights, mixed with aromatic polymer compounds, asphaltene, resin, etc. Because it has a very high pour point, it takes a lot of effort to remove it. Requires expenses. This kind of thing occurs not only in crude oil tanks but also in heavy oil tanks, and has become an important problem in business establishments such as power plants that consume large amounts of oil. The only methods currently used in Japan to prevent the accumulation of sludge are mechanical methods. In other words, a stirrer attached to the side of the tank forces convection of the crude oil in the tank.
This is a method to prevent sludge from settling. However, in a huge tank, the flow only occurs in a part of the tank, and a sufficient stirring effect cannot be obtained. Furthermore, the electric power required to operate the stirrer cannot be ignored, which is economically disadvantageous, especially in tanks for long-term stockpiling projects. For these reasons, methods of adding small amounts of chemicals to prevent sludge buildup have been studied in the United States for quite some time. The purpose of this method is to prevent the precipitation of crystals such as paraffin, which is a component of the sludge. However, this method cannot simply be applied to the case of Japan. Oil imported into our country is
Imported crude oil is transported over a long period of time from remote areas such as the Middle East, where temperatures are quite high, to Japan, where it is relatively cool, so there are already plenty of precipitated and grown crystals such as paraffin in imported crude oil. It is. For the above reasons, the present inventors have developed a method for preventing the accumulation of sludge that is consistent with Japan's petroleum situation by stably dispersing the sludge, which has already been generated close to the maximum, into oil using a surfactant. As a result of repeated studies aimed at preventing sludge from settling to the bottom, it was discovered that adding polyoxyalkylene sorbitan fatty acid ester to petroleum can effectively prevent the accumulation of sludge. The polyoxyalkylene sorbitan fatty acid ester used in the present invention is derived from an ester obtained by heating and dehydrating sorbitan or sorbitol and a linear or branched, saturated or unsaturated fatty acid having 4 to 22 carbon atoms. However, in this raw ester, mono-, di-, and triesters such as sorbitol, sorbitan, and sorbide are mixed in a complicated composition ratio, so in the following explanation, the names of the main components in the raw ester will be used. These esters can be used in the present invention by adding 5 moles or more of ethylene oxide, or by adding 5 moles or more of ethylene oxide and other alkylene oxides such as propylene oxide or butylene oxide in a block or random pattern. A polyoxyalkylene sorbitan fatty acid ester is obtained. The polyoxyalkylene sorbitan fatty acid ester used in the present invention includes the type and composition of the fatty acid as a raw material, the type and amount of alkylene oxide added,
Although the effect of preventing petroleum sludge from accumulating varies depending on the composition, etc., by appropriately selecting these conditions depending on the type of petroleum, the amount of sludge accumulation can be extremely reduced. The amount of these polyoxyalkylene sorbitan fatty acid esters added is 2 to
500 ppm, preferably 5 to 150 ppm. 2ppm
If it is less than 500 ppm, the effect will be small, and if it exceeds 500 ppm, the effect will not improve much, which is economically disadvantageous. On the other hand, when branched polyethylene (U.S. Pat. No. 3,640,824) or naphthalene (U.S. Pat. No. 3,276,519), which are paraffin precipitation inhibitors, are used, the amount of deposited sludge hardly decreases, and there is no difference from the case where nothing is added. was hardly recognized. However, when storing crude oil for a long period of time,
When new crystals such as paraffin are gradually precipitated, it may be effective to use these paraffin precipitation inhibitors in combination with the polyoxyalkylene sorbitan fatty acid ester of the present invention. Next, the present invention will be explained with reference to Examples and Comparative Examples, and tests were conducted in the following manner. A 100ml centrifuge tube (JIS K-2603-
Using a 1971 centrifugal graduated test tube, 100 ml of crude oil was added to the tube, additives were added, the mixture was tightly capped, shaken, and the mixture was allowed to stand in a thermostatic chamber at a predetermined temperature. After a predetermined period of time had elapsed, the centrifuge tube was turned upside down, the crude oil was poured out, and the tube was left standing upside down in the same constant temperature room for another hour. In this state, the amount of accumulated sludge still remaining at the bottom was read on a centrifuge tube scale to judge the effect of preventing accumulation. Table 1 uses basralite crude oil at 100°C at 20°C.
The test results obtained when the samples were allowed to stand for one day showed that Examples 1 to 10 in which the polyoxyalkylene sorbitan fatty acid ester of the present invention was added had a small amount of deposited sludge. Comparative Example 1 is a case in which no additive is added, Comparative Examples 2 to 3 are cases in which the above-mentioned US patent paraffin precipitation inhibitor is added, and Comparative Examples 4 to 10 are cases in which another surfactant is used.

【table】

[Table] In Table-2, Umm-Syaif crude oil is used, and 100% at 20℃
The case where the samples were allowed to stand for one day is shown, but in all Examples 11 to 17 in which the polyoxyalkylene sorbitan fatty acid ester of the present invention was used, the amount of deposited sludge was extremely small.

【table】

[Table] Table 3 shows the case where Daqing crude oil was used and allowed to stand at 40°C for 80 days, and Examples 18 to 24 of the present invention all showed very good deposition prevention effects.

【table】

Claims (1)

[Claims] 1. A method for preventing deposition of petroleum sludge, which comprises adding polyoxyalkylene sorbitan fatty acid ester to petroleum. 2. The method for preventing deposition of petroleum sludge according to claim 1, wherein the polyoxyalkylene sorbitan fatty acid ester is an ester of a linear or branched, saturated or unsaturated fatty acid having 4 to 22 carbon atoms. 3. The method for preventing deposition of petroleum sludge according to claim 1 or 2, wherein the polyoxyalkylene sorbitan fatty acid ester is an adduct of sorbitan fatty acid ester with 5 moles or more of ethylene oxide. 4. Claims 1 or 2, wherein the polyoxyalkylene sorbitan fatty acid ester is obtained by adding ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms to a sorbitan fatty acid ester in a block or random manner of 5 moles or more in total. The described method for preventing the accumulation of petroleum sludge. 5. The method for preventing deposition of petroleum sludge according to claim 1, 2, 3, or 4, wherein the amount of polyoxyalkylene sorbitan fatty acid ester added is 2 to 500 ppm based on petroleum.