DE1545347A1 - Flotation process for the separation of wax and paraffin hydrocarbons from oils - Google Patents

Description

Societe Industrielle Beige des Petroles S.A., Antwerp (Belgium).

Flotation process for the separation of wax and paraffin hydrocarbons from oils

The invention relates to the separation of wax and paraffin hydrocarbons from oils by flotation.

It is known that water-like hydrocarbons are produced by cooling in the presence of solvents and filtering off the solid Separate wax from oils. It has also been proposed to use waxy hydrocarbons by flotation to separate. In this process, gas bubbles are passed through the cooled oil from bottom to top, so that the wax is deposited as a foam on the oil. This method has the advantage that there is no filtration or centrifugation is required and that it is basically a simple procedure. However, as far as is known, the procedure is never in the has been transferred to an industrial scale. One reason for this may be the crucial physical conditions which are necessary for good results * as well as in the fact that with different input materials the ease with which they can be dewaxed by flotation varies widely.

This aspect is dealt with in Belgian patent application No. 43900. Another and equally important reason lies in the practical difficulties of cooling the

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Oil on an industrial scale. In a flotation process the gas bubbles must have unhindered passage through the oil so that cooling coils are not used in the flotation bath can be. Likewise, a cooling of the oil is before the Entry into the bath undesirable, as otherwise wax will be deposited and scrapers will have to be used.

According to a previous suggestion that these difficulties avoids, the gas used should be pre-cooled and also for Serve to cool the oil, but a consideration of the specific heat of suitable gases and the oils to be treated shows that with acceptable gas / oil ratios a very strong one Cooling is required.

The invention relates to a very simple alternative method for cooling the oil in a wax flotation process. The method according to the invention for the separation of wax and paraffin hydrocarbons from oils by flotation, a gas being passed from bottom to top through the oil, which has been cooled to a temperature below its cloud point is characterized in that the fresh oil of the flotation zone is at a temperature above its cloud point is supplied and that the fresh oil by withdrawing a partial flow of the oil from the zone, cooling this flow and return to the zone is cooled, the ratio of cycle oil to fresh oil being at least 5! 1 * preferably 10: 1.

The use of cycle cooling at a high ratio of cycle oil to fresh oil means that the extent of the Cooling required for the circulating oil is low, namely in practice about J5.3 ° C or less, and that the flow rate through the cooler can be high. These two factors cause the deposition of wax largely avoided in the coolers and eliminated the need for coolers provided with scrapers. But when If protection for starting up or against malfunctions is deemed necessary, coolers can be connected in parallel and

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be provided with devices that make it possible to feed the oil to all or any cooler. In this way it is possible to switch off one or more coolers for cleaning without shutting down the entire system. The cleaning can be done in a simple manner and easily by heating the cooler, for example with warm oil.

Any type of cooler can be used to cool the circulating oil. Tubular heat exchangers, for example, are suitable. The type of coolant is also not decisive. Liquefied petroleum gases are advantageous, e.g. liquid propane or butane.

The stream of cycle oil is preferably from the flotation zone at a point away from the fresh oil inlet, and preferably withdrawn from the bottom of the zone. That Circulation oil can be via a separate line, which is preferably enters the bath at a point close to the fresh oil inlet. However, it turned out that a single recycle and fresh oil line can be used, provided that this line is not too long is. In this case, the circulation oil and the fresh oil are expediently in or near the fresh oil and circulation pumps mixed.

The dewaxed oil must of course be withdrawn in such an amount that the amount of liquid in the flotation zone remains constant. This can be achieved in a simple manner, by withdrawing the required amount from the circulating stream. The wax that collects on the top of the zone is also taken continuously or at intervals. In a particularly expedient manner, the wax foam removed with the help of an arm that extends across or lengthways extends over the bath and brushes over the top of the bath * This can be achieved, for example, by that the arm is attached to an endless belt. The arm pushes the wax over a weir into a collection chamber, which is expediently thermally insulated from the flotation zone

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and contains a heating coil * The heated guard can then be easily removed as a liquid.

The Belgian patent application No. 4-3900 describes the importance of the correct choice of the feedstock. According to this, materials are expediently treated which contain at least a proportion of cracked material, in particular 0.5 to 100 VpI. -% contain cracked material and have a viscosity of no more than 20 cS at the specified separation temperature. It has been shown that the amount of circulation must be as high as possible in order to reduce the likelihood of wax settling out of the circulation flow.

Wax and paraffin hydrocarbons may have trouble in oils cause, which in kerosene gas oil and wax distillate range - boiling (150 650 ⁰ C). The process is applicable to all of these feedstocks, but of course the heavier materials require more diluent to lower the viscosity. It has also been found that the presence of asphalt or other materials which are effective as pour point depressants, even in very small amounts, is disadvantageous, so that their presence must be avoided. The cloud points of the acu, treating oils can vary over a fairly wide range, so that the same also applies to the flotation temperature. However, suitable temperatures are in the range from -18 to 27 ⁰ C, in particular from -7 to 4 ° C. In effective operation, the cloud point of the dewaxed oil and the temperature used are essentially the same.

The amount of gas used is not critically important. Oute 'results have already been obtained at a volume ratio of gas (at normal temperature and normal pressure) to oil content of 0.2, although there were no indications that this ratio was a limit value. Higher ratios are not disadvantageous, but bring little additional benefit. Suitable,; ¹ ^ is therefore a range from 0.1 to 10. Any · paeeend · Oaee can be used, e.g. nitrogen, nitrogen-free. ^ - * gases, e.g. flue gas, hydrogen or under normal conditions ", *

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gaseous hydrocarbons. Air is also suitable however, their use on an industrial scale is possibly related by safety regulations limited with fire hazards.

The gas must of course be in the form of bubbles from bottom to top pour through the oil. It can optionally be at the bottom of the Plotation bath introduced by known distribution devices will. It has been found, however, that the gas can be introduced very easily and efficiently by it into the suction side of the pump that feeds the oil into the bath * is blown in. In this case, however, make sure that the outlet pressure of the pump is between 2 and 10 kg / cm lies.

The amount of oil introduced into the flotation zone and that out The amount of dewaxed oil withdrawn from the flotation zone must be adjusted so that there is a suitable residence time results. This can easily be determined experimentally. In practice, residence times of up to 7 hours have proven to be suitable.

From the method according to the invention, a dewaxed oil of reduced cloud point and pour point can be obtained as well win the wax. If the wax is in the form of foam on the surface of the flotation zone, the wax can be significant Contain amounts of oil carried over. However, a large part of this oil separates out on standing, and any remaining oil can be further reduced Separate known methods, waxes are obtained which are qualitatively equivalent to the waxes, for example separated by filtration in the presence of solvents. When the wax is not used for special purposes it can be used, for example, as a high value feedstock for catalytic cracking.

The invention is described with reference to the figure, which is a flow diagram of a suitable plant.

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In the system shown, the flotation zone consists of a rectangular tank with an oil inlet 2 and a oil leak JJ. The fresh use is related to the system at 4 with the gas fed through the line 5 in the Suction side of the pump 6 is blown. The fresh use is made with a recycle stream, which is described in more detail below is described, mixed and passes through line 7 to inlet 2.

Part of the oil is released through outlet 3 and line 8 deducted. Part of this S-stream is called through line 9 dewaxed oil withdrawn. The rest is through a series of Heat exchangers 10, 11 and 12 out. Through suitable pipes and valves, which are shown schematically in the figure are indicated, the oil can be fed to all or any exchangers. The oil cooled in the exchangers is combined with the fresh feed and the flotation gas via line 15 and enters again through inlet 2 the tank 1. There are pumps in this circuit line If required, for example at 25 and 26.

The coolant is the. Heat exchangers through the pipe fed; this coolant can also be and is fed to any and all heat exchangers withdrawn through line 15.

Lines and valves can be provided on the oil side of the exchangers to allow a cleaning liquid, e.g. warm oil, to pass through any heat exchanger that has been shut down by the system.

The oil level in the tank is kept constant by the supply and withdrawal of oil to a level just below the weir 16 is regulated. An endless belt 17, which from driven by disks 18 and 19 is connected to an arm 20 which extends across the bath. At the "On the other side of the bath there is a wax collecting chamber 21 with a heating coil 22 and an outlet 23. The side

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of the bath towards the collecting chamber is provided with thermal insulation.

example

The! Sank 1, which was 25 m long, 12 m wide and 1.5 m deep, was filled with oil at 21 ° C. This oil was a cycle oil from a catalytic cracking plant, which had a boiling range from 320 to 370 ^° C. and a viscosity of 50 cS at ⁰ ° C. and, with straight-run kerosene, led to an oil with a viscosity of 13 cS O ⁰ C, a cloud point of 16.7 ⁰ C, a pour point of 15.6 ⁰ C and a boiling range of 370 ° C was diluted. The oil was cooled to -1 ° C by passing it through line 8, heat exchangers 10, 11 and 12 and back to the tank through lines 13 and 7 again. During this initial cooling phase, wax can settle in the exchangers. The exchangers can be switched off from the system as required and cleaned with a separate stream of warm oil.

It is also possible to start up the system in such a way that the sedimentation vessel is filled with kerosene, this to the required level Temperature cools and only then introduces the fresh oil. Through the other side the heat exchanger is made liquid propane at -6.7 ° C via lines 14 and 15 guided.

M O

After the oil had reached a temperature of -1 C, fresh oil of 21 ° C and gas were introduced via the lines 4, 5 and the pump 6. The hairdressing oil was cooled to the tank temperature of ^{0 ° C. by the circulating oil.} The gas blown at 5 under the pressure of the suction side of the pump 6 was released when the oil reached the tank 1 and flowed upward in the form of fine bubbles. At the same time, wax separated from the fresh oil and combined with the bubbles to form a foam on top of the oil. This foam was periodically passed through the arm 20

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the weir 16 pushed into the collecting chamber 21. Here was it is liquefied by the heating coil 22 and by conduction deducted.

Of the. Primary oil use was 10 m ^ / hour, the ratio of cycle oil to fresh oil 20tl and the temperature drop of the cycle oil on the way through the heat exchange *** 1 , I ⁰ C. The gas - flue gas was used - was in a ratio to fresh oil of 0.5: 1 is used. ,.

The yield of dewaxed oil with a cloud point of -IjI ⁰ C was 80 °, the yield of Waeheschaum 20 $.

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Claims (6)

- 9 claims 1.yContinuous process for the separation of waxy Hydrocarbons from oils by flotation «being a gas is passed upward through the oil cooled to a temperature below its cloud point, characterized in that the fresh oil is fed to the flotation zone at a temperature above its cloud point, and that the fresh oil is passed through Withdrawal of a partial stream of the oil from the zone, cooling this stream and returning it to the zone, is cooled, the ratio from cycle oil to fresh oil at least 5 ι 1, preferably 10 ι 1 is. 2.) The method according to claim 1, characterized in that the oil carried out is cooled in heat exchangers without SChaber. 3.) Process according to claims 1 and 2, characterized in that several heat exchangers are arranged in parallel in the process are that one ofler several of the exchangers are excluded from the system without affecting the other exchangers can be. 4.) Process according to Claims 1 to J5, characterized in that that the cycle oil is withdrawn from the flotation zone at one point which is removed from the supply of the fresh egg and in particular lies at the bottom of the flotation zone. 5.) Process according to Claims 1 to 4, characterized in that that the dewaxed oil is withdrawn from the cycle oil in such an amount that the amount of oil in the flotation zone remains essentially constant. 6.) Process according to Claims 1 to 5, characterized in that .009809 / 1396
BAbORlGINAl - ίο .- that the wax foam is deposited by placing it over a Weir (24) pushed into a collecting chamber (21) on one side of the zone, heated in the chamber and as a liquid is deducted. 009809/1396 BAD ORIGINAL