DE938779C - Procedure to prevent the evaporation of volatile constituents - Google Patents

Description

Process for preventing the evaporation of volatile molar fractions the The invention relates to a method for preventing evaporation losses from crude oil and the like through a floating layer of small, hollow, hole-free Particle.

The petroleum industry has had the problem of evaporation for a long time of petroleum products stored in tanks perceived as very annoying. From attempts Various proposals have been made to reduce these losses, including however, none turned out to be really satisfactory. The external shape of the storage container, especially that of their coverings, has been altered in an effort to reduce evaporation loss to reduce, but this turned out to be only a partial solution, both of the so-called "breathing" effect with temperature changes as certain difficulties opposed when filling and emptying the tanks. Floating foams from countless chemical compounds were suggested without that, probably due to the short life of such foams, a remarkable reduction the evaporation loss has been reached. They also have some of these chemical Compounds contaminated the stored petroleum products. The mentioned evaporation loss continued to prove exceptionally costly.

It is in view of these difficulties that it is a purpose of the invention; to develop a permanent, cheap and effective process that is suitable is to significantly reduce or completely prevent the evaporation loss on the surface of petroleum products, especially crude oil or fractions containing both volatile and heavier components from the Crude oil -intnt.

So it and other objects of the invention, as well as its usefulness and applicability will be apparent from the more detailed description below.

Evaporation loss has now been found to be effective in crude oil can be reduced or prevented if a layer of small, hollow, Float on the oil free of holes, which consist of film-forming substances and each of which is a separate corpuscle.

A process for the production of gas-filled, hole-free hollow bodies consists essentially in having a volatile carrier with a content of film-forming material that can form a tough, gas-impermeable skin, and sprayed a gaseous or gas-forming substance in a stream of heated air, wherein the carrier is volatilized and the film-forming substance is in the form of hollow bodies, containing the evolved gas solidified. That developed during drying Gas is trapped inside the hollow particles and prevents them from collapsing the walls of the vesicles during or after drying.

Gases which can be used as such for the process described above are among others carbon dioxide, methylene chloride, ammonia, dimethylene ether, ethylene oxide, Methylene amine, methylene bromide, dimethylene amine, etc., gas-evolving substances, in general referred to as blowing agents, can also be used for the process mentioned. Some of these known propellants that can be used are, for example inorganic and organic salts such as carbonates, nitrites, carbamates, oxalates, formates, Benzoates, Sullites, bicarbonates, for example the sodium, ammonium, Calcium and magnesium salts. Organic substances produced by the aforementioned process can be used for the production of hole-free hollow bodies are, for. B. p-oxyphenyl azide, NN-dinitrosopiperazine, polymethylene nitrosamines, such as NN-dinitrosopentamethylene tetramine and trimethylene trinitrosamine, as well as compounds with two or more groups of the formula CO; N (NO) - alkyl, such as the succin-bis- (N-nitrosomethylamide), the diazoaminobenzene, the diazoisobutyric acid dinitrile and their by using cyclohexanone or methyl ethyl ketone in place of acetone produced homologs.

Many of the propellants mentioned above react with other substances with an instantaneous release of gases. For example, carbonates react and sulfites such as sodium carbonate and sodium sulfite with acids such as hydrochloric or sulfuric acid with the formation of carbon dioxide or sulfur dioxide. Ammonium salts react with Bases, such as caustic soda, liberate ammonia. One gives therefore to a solution of film-forming material according to the invention containing a carbonate or sulfite, hydrochloric acid diluted at the moment of its introduction into the atomizer, so becomes Carbonic acid or sulfur dioxide free, which is present during spray drying and represents the gas necessary for the formation of the hole-free particles. 6 The The amount of gas-forming substance required depends on the weight of the film-forming material Solution and the type and amount of gas evolved and usually moves in the range of about 0.1 to 25 percent by weight of the solution to be sprayed.

The film-forming substances used for this are inter alia.

Cellulose derivatives, such as cellulose acetate and cellulose acetate butyrate and the cellulose acetate propionate, further thermoplastic synthetic resins such as the polyvinyl resins; d. H. polyvinyl alcohol, polyvinyl chloride; the copolymers made of vinyl chloride and vinyl acetate, polyvinyl butyraldehyde, polystyrene, polyvinylidene chloride, the acrylic acid resins, e.g. B. the polymethyl methacrylate, the polyallyl, the polyethylene and the polyamide resins, furthermore the thermosetting resins in their initial state partial polymerization in which they are in aqueous or organic solvents are soluble, these resins then after or during the formation of the vesicles converted into a more or less fully polymerized, insoluble state as is the case with the alkyd, polysiloxane, phenol-formaldehyde, urea-formaldehyde and melamine-formaldehyde resins-is the case. All of these resins are film-forming and therefore capable of evaporation of droplets from their solutions in aqueous or organic solvents to form vesicles with tough epidermis. Also film-forming Natural substances, so among others soybean and corn protein (zein), alginates and as Cellulose xanthate or copper ammonia cellulose in solution, can be used in the context of the above-mentioned patent, as can inorganic ones film-forming substances, such as sodium silicate, are to be considered included are.

The solvent used is of course determined by the solubility of the film-forming substance used. When it evaporates, it should die Promote solidification of the substance so that on the surface of the droplet quickly a tough skin is formed. Water, alcohols, ethers, esters, organic acids, Hydrocarbons and chlorinated hydrocarbons are the most notable among the appropriate solvents.

The solution concentration of the film-forming substance is not decisive since their lower limit is given by the particle size, the smallest being Particle can be formed from the most dilute solutions, and their upper limit by the Viscosity of the solution and determined by the maximum desirable particle size will. Particularly favorable results have been obtained with solutions containing from 1 to 15% of film-forming substance, although concentrations up to 300 /, also proven to be satisfactory. Solutions from one dilution to 0.1% also showed satisfactory results. Aqueous solutions with a content of 1 to 100 / o polyvinyl alcohol (viscosity of a 40 / above aqueous solution at 200 = 4-28 cp. in the Hoeppler falling ball viscometer) or from 1 to 30%, preferably 5 to 200/0, phenol-formaldehyde resins gave very satisfactory results.

The solution is prepared in the usual way, divided into droplets and dried. The use of a spray drying device proved to be particularly advantageous, in which the droplets in a stream of hot gas, usually in hot air, to be dried. The drying temperature will be in accordance with the stability and the softening point of the film-forming material, the size of the droplets produced and the volatility of the solvent used. As the skilled person will recognize however, in view of the cooling effect of the evaporation process, dry air can be used very high temperature can be used without the risk of injury in the case of low melting points or easily decomposable substances occurs.

A high drying temperature is very desirable; usually air temperatures in the range of 25 to 375 ° are suitable. Suitable drying conditions for individual cases can be seen from the examples.

The in the usual spray drying devices when using Solutions of the concentrations given above produced dry bodies (vesicles) are very small. Usually their diameter is about ten times the thickness the plastic skin that encloses its hollow interior, however, these dimensions depend on the droplet size generated in the particular device and the solution concentration of the film-forming substance.

Except for the hollow bodies produced by the method described above hollow spherical particles made in other ways can be used, and in which the vesicle walls are made of other materials. For example the hollow bodies can be formed from a ceramic material which is produced by heating from clay particles to a very high temperature or by creating hollow, hole-free ones Glass bubbles may have been produced. These particles float on liquids and can be used alone or in conjunction with those described in detail above Hollow bodies are used.

The term "hollow body" as used here therefore includes all such very small, hollow, hole-free particles of more or less spherical shape floating on a liquid regardless of that Material from which they are formed, as long as they are insoluble and inert with respect to the are substances in contact with them, and regardless of the process, after which they are made.

Example I A solution of water-soluble, partially polymerized A propellant was added to phenol-formaldehyde resin in water. The mixture contained In01, resin, IO /, di-N-nitrosopentamethylene tetramine (on an active basis) and 890 /, water. This preparation was in a slightly modified commercially available Spray dryer sprayed and dried, the one at an inlet temperature of 277 ° and a final temperature of 28 "working dryer per minute 454 g of solution were fed.

The approach was carried out using the same solution and under the same Repeated conditions, but the feed rate was 1.36 kg per minute. There the hollow bodies obtained at the two feed rates are not significant turned out different, the yield from the two approaches was combined and the properties of the particles obtained are listed under I in Table I.

Example 2 Example I was repeated, but the solution was a Contained smaller amount of resin and blowing agent, so that their composition was 2,5010 Resin, 0.50 /, blowing agent and 970 /, water. It became a laboratory spray dryer - at a speed of 100 cm3 / min. fed and at a feed temperature of 4000 and an ejection temperature of 2600 are sprayed and dried.

The properties of the hollow bodies obtained are shown in the following table: Table I Approach no. (Example no.) I *) 2 Characteristics: Density in g / cm3 apparent specific Weight ...... o, og8 0.0207 Fluid flow urge (act- neuter density) 0.320 0. in34 Size in, u: Average .... I6, o 21.4 Area in Microscope .... 2-30 5-50 (Continuation of the table overleaf) *) Approach I is a mixture of the products of the two experiments from Example I, which gave very similar products. The properties are listed here in average values from both approaches.

Table 1 (continued) Approach No. 2 (Example no.) I *) 2 Swim in pro cent (estimated): in DD naphtha in 24 hours decreased (0 / o) .. 4 1 Appearance I hollow spheres, hollow spheres *) Approach I is a mixture of the products of the two experiments from Example I, which gave very similar products. The properties are listed here in average values from both approaches.

Example.3 A solution of a phenol-formaldehyde resin with a content of 1 ° / o ammonium carbonate as blowing agent and 89% water was at a feed rate of III cm3 / min. with the help of a spray dryer that worked with an inlet temperature of 375 "and an outlet temperature of 2000, sprayed and dried. In the swimming test (flotation test) were after 24 hours only 30/0 of the hollow bodies have sunk. The particles had a liquid displacement density (= true specific gravity) of 0.449, an apparent specific gravity in total mass of o, I63 and were over a size range (determined microscopically) distributed from 2 to 30 cm.

Example 4 Example 3 was repeated, but using the propellant Ammonium nitrite was used. The hollow bodies had a liquid displacement density of 0.353, an apparent specific gravity in the total mass of 0.09 and a size of 2 to 40 tal. In the flotation test, only 10 / o had sunk after 24 hours.

Example 5 An aqueous solution of 50% polyvinyl alcohol in 94.50 / 0 Water was mixed with 0.5% ammonium carbonate as a blowing agent. This mixture was at a feed rate of 80 cm3 / min. and a feed temperature of 3150 or an output temperature of 320 to spray drying.

The hollow bodies had a liquid displacement density of o, Ig2 and an apparent specific gravity in the total mass of 0.07 on and ranged in size from 5 to 50,:. In the flotation test, only 20/0 fell away.

Analogously to the above general description and according to the examples were made from urea-formaldehyde resin, polystyrene, methyl cellulose and sodium silicates existing hole-free hollow bodies produced, the apparent specific gravity in total mass between 0.05 and 0.23 and an average particle size of 2, c2 to 36.5 leu.

The apparent specific gravity for the total masses is preferably in the range from 0. OI to 0.3 and this corresponds to a liquid displacement density in the range from preferably 0.05 to 0.6 (g / cm3), in particular between 0.2 to 0.5. The (apparent) density of the total mass is of interest when transporting or storing the dry hollow bodies. The liquid displacement density (= true density) is of interest when the space between the individual hollow bodies should be filled with a liquid, such as. B. in a foam.

The particles have an average diameter of 1 to about 500 to preferably from 25 to 250 y. Particles the size below I u are quite useful, but more difficult to use.

If the hollow bodies contain a volatile hydrocarbon fraction, like gasoline, they float on it, but prevent it, even if they are present in a layer several centimeters thick, not noticeably the evaporation. The reason for this can be assumed that the gasoline has the capillary spaces between the individual hollow bodies and from those on the surface Gaps can evaporate. The layer of hollow bodies then pulls according to Art a wick from below for more gasoline.

This process suggested that the hollow bodies with a sealing liquid to mix, which is non-volatile and floats together with the particles to thereby to prevent the gasoline from penetrating into the capillary spaces mentioned.

This requires the use of a separate sealing liquid, which increases the cost. It is also necessary to seal the hollow bodies with the sealing liquid to mix, which requires a separate operation.

According to the invention it has now been shown that, in contrast to the one to be expected on the basis of the above experiences, hollow bodies to prevent it evaporation in crude oil. There are apparently constituents in crude oil present, which have the function of a final resp.

Take over sealing liquid, d. H. the volatile components of the Prevent crude oil from penetrating the layer of hollow bodies, and at the same time are these components such that a crust-like surface is cooked does not, or at least not to such an extent, forms that thereby at If the floating layer breaks, the reconnection is diminished. It must be called a fortunate circumstance that the components that make up the hollow bodies put in a position to prevent the evaporation of the crude oil, at the same time constituents of the crude oil itself.

The above considerations are only possible explanations of the events observed, and the scope of the invention is not determined by any theoretical explanations of the observed results are limited.

The floating layer of hollow bodies is formed when one the latter to crude oil or other oil, such as light neutral oil, which is to crude oil is added, to protect the latter from evaporation losses. The combination of hollow bodies and crude oil results in a foam in shape a viscous sludge in which the hollow bodies are about 20 to 700/0, preferably Consume 40 to 55 per cent by volume. This essentially consists of hollow bodies and Crude oil or a component of the latter composed of floating protective layer becomes gas-tight that the crude oil or its portion coming into effect through the capillary forces acting between the capillary spaces of the spherical particles is being held.

The foam layer deposited on the crude oil surface must be thick enough be an effective reduction or the complete prevention of evaporation losses to ensure. In accordance with this, have suitable evaporation tests on single barrels show that a layer of about 2.5 cm of a foam made of crude oil and hollow bodies reduce the evaporation loss to about 20 to 30 percent of the loss uncovered crude oil (see Table II). Part of the loss that still occurs may be due to initial losses during the training of a Equilibrium. After the layer reaches a uniform composition the losses are lower. The thickness of the layer is variable. An essential one Reduction in evaporation is already achieved with a layer of about 0.3 cm thickness. Using layers thicker than about three inches is convenient pointless.

Another embodiment of the invention is where appropriate to be selected addition of a non-oil-miscible, non-volatile lubricant, for example of dipropylene glycol, to the hollow body, which serves to increase the mobility of the To enlarge the foam layer, which otherwise tends to build up after a certain period of time to transform into a relatively rigid top layer. The optimal amount of the lubricant to be added is 0.5 to 4%, preferably about 20 / o des Erchen the weight of the hollow bodies contained in the foam. This amount is less than the necessary to fill all capillary spaces. The importance of a Admixture of dipropylene glycol in only small proportions is clearly shown in the table II, approaches G, H and I, where 10, 20 and 30 0 / o dipropylene glycol is extremely rigid Foams gave what prevented the final effect of the foam.

The difficulties encountered when using a sealing liquid have already been described.

It is important for maintaining the mobility of the gas impermeable Protective layer to enable them to close again, in case it breaks at some point. In the normal storage or return of Crude oil can break the foam cover through disruptive parts in the tank or in some other way then a part of the crude oil surface is exposed to the air, so that an evaporation loss occurs. As a result, the inclination poses the protective Foam layer to close again quickly, an essential property of a suitable protective foam layer. Even if the outer surface of the mixture of hollow bodies and crude oil tends to turn into a relatively rigid surface layer to convert, the lower parts of the foam layer according to the invention are sufficient flexible to enable the foam to penetrate the cracks and thus the layer to seal again automatically from below.

To determine the effect of the foam according to the invention were two zoo-l-barrels, open at the top, each containing about 38 l of West Texas C crude oil of the specific Weight o.856 contained, which floated on about In.41 water, set. In one A certain amount of very light hollow bodies was placed in the barrels mixed with a proportion of crude oil that would cause a foam thickness like them from batch B in Table II it was sufficient. The two barrels, one of them now one covered with a floating foam, the other completely uncovered were left in a small shed away from direct sunlight for 18 days. Measurements of the liquid level or its change were then carried out, which, when converted, showed that it was with a layer of foam covered barrel had lost only a relatively small percentage of which evaporates from the uncovered reference barrel of volatile hydrocarbons was. The results can be seen from batch A and B of Table II. With another Experimental series, designated batch C-I in Table II, were the experimental barrels mounted on a metal platform and placed each 7.5 cm above the floor entering manifold connected to the water supply and drainage. The barrels were provided with a clamp cover, and a fume cupboard made of 5 cm pipe and elbows was in it provided upper part of each of the barrels. The water manifold contained one Flow meter that determines the rise and fall of the water surface allowed in the respective barrel.

Measurements were made to determine the height of the hydrocarbon layer carried out in which a small, floating measuring container by means of a electrical probe the water level was determined.

The hydrocarbon level was then measured using a millimeter ruler measured outside the probe.

The measurements were taken once for each barrel every few days, at the same time with qualitative studies on the sealability of the foam. Each time the hydrocarbon level was measured, the liquid level became in the test barrels by pumping in or withdrawing water upwards or downwards changes. During these up and down movements, the foam layer came along every time a ridge running around the barrel that broke the seal.

Furthermore, the layer came into contact with the part of the barrel wall that was originally in contact with water, which acted in a similar way to that condensation water normally present on the tank walls. As can be seen from Table II, the mixture of hollow bodies and crude oil was a small amount in some cases The above dipropylene glycol was added.

The results were as follows: Table II loss Foam composition mm / day loss% loss in observations To thick (average (average liters / dayj / about mobility sets cm of foam from Iooo m2 daily test and sealing effect Penode) A no crude oil (comparison test) - 0.72 6.17 100 - spec. Weight o.856 B 2.0 A plus hollow bodies o, 22 I, 9 3I Wide slot with a (Example II) 10 cm border, waterproofing + 2 percent by weight according to the test period Dipropylene glycol (go 0 / e) satisfactory C no crude oil (comparison experiment) I, 3 II, 2 I00 - spec. Weight 0.846 D 2.5 C plus hollow bodies 0.3 2.6 23 Rigid surface, ab- (Example II) seal, however, digend E 2.5 C plus hollow body c, 3 2.6 23 About the same as (Example I) at D F 5.0 C plus hollow bodies 0.5 4.2 37 More rigid than with D and -E, (Example I) Sealing satisfactory gend, however slower than with E G 2.5 - C plus hollow bodies o.6 5.3 47 surface more mobile (Example I) than with E, sealing + 10 percent by volume satisfactory, but a lot Dipropylene glycol slower than with E H 2.5 C plus hollow bodies 0.7 6, o 53 Mobility a little (Example I) greater than E, sealing + 20 percent by volume roughly the same. Dipropylene glycol I 2.5 C plus hollow bodies- I, I *) 9.5 84 So rigid that sealing (Example I) right from the start + 30 percent by volume doubtful Dipropylene glycol *) Average value over 6 days, then canceled due to obvious lack of sealing B. 20/0 of propylene glycol also gives satisfactory results (approach B).

Amounts of 10% and above, however, result in a rigid one to achieve Foam incapable of rapid sealing, which consequently results in greater evaporation losses shows. (Approaches G, H and I.) An increase in specific gravity (i.e. the water displacement) of the hollow bodies from 0.1 to 0.3 influenced the protective effect of the foam formed therefrom in no way, as is clear from batches D and E. emerges. The thickness of the floating layer was increased from 2.5 to 5 cm turned out to be practically useless, and it even turned out that the thicker layer made one showed greater evaporation loss than the 2.5 cm layer (approach F).

The above tests were supplemented by factory tests. There were for this purpose two large working tanks in good shape, which are open to the open air and filled with crude oil. One of the tanks was covered with hollow bodies, the other uncovered. The top layer of the former had been made by Mixing the hollow particles with the crude oil in a ratio of 120 g hollow bodies per liter of crude oil. The mixture was then placed in the tank in such an amount that it finally covers the entire surface of the crude oil to a thickness of about 2 cm covered as a stable foam layer made of microballoons and crude oil.

Very careful measurements of the crude oil in each of the tanks were carried out at intervals of 1 to 2 weeks over the entire duration of the experiment of about 67 days. The results in the form of the average evaporation loss are shown in the following table: Table III Tank loss liter / Bbl / day I000 m2 / day Comparison test 0> 090 o, ogo 3> 64 Covered with micro balloon foam 0, ob26 0.5I Investigations into the properties of the crude oil before and after 56 days of storage in the two tanks also showed that the contents of the comparison tank had changed significantly more than that of the other test tank. This was shown in a change in the specific gravity (or the API grades) and the 10% point in the Engler distillation. These results are shown in Table as follows: Table IV After 56 days Initial Ver values equal search values values "API 1 37> 7 36> 0 37> 6 Specific gravity o, 8362 o, 8447 0> 8366 I0 ° / O-Punlçt, "C. I20 127> 8 I2I, 7 Suitable means of any kind can be used to protect the surface of crude oil tanks with a floating foam of the type described above. In the case of very small tanks, the foam can be generated by simply pouring the hollow bodies onto the surface of the crude oil and by stirring the entire upper layer for the purpose of good distribution of the hollow bodies in the crude oil of the upper layer. In practice, however, much larger tanks are used, which makes such a mode of operation less suitable. In the case of small tanks, it is possible to get the surface of the crude oil sufficiently in motion by stirring it from a measuring hatch with a larger stirrer or, if necessary, with a horizontally mounted disc that can be moved up and down using a suitable handle to disperse or mix in the hollow bodies poured through the hatch onto the crude oil surface in a sufficient manner. However, the large tanks commonly found in the art may require other methods of installation. One of these methods consists in premixing the hollow bodies with oil, the latter not necessarily having to be crude oil (a light neutral oil or a residual oil can be used for safety reasons). This results in a viscous sludge which can then be pumped onto the surface of the tank through any feed opening. Another method of applying the sludge to the surface of the crude oil consists in placing the hollow bodies in a vent arrangement for "breathing" into which the crude oil, which is either taken from an emptying oil line or is branched off from the tank itself, is pumped at the same time . This creates a foam made of hollow bodies and crude oil, which is fed to an inlet opening through an oil-resistant hose. These methods only explain some special devices for applying a floating foam of the type described here to the crude oil surface and can be varied as desired.

Claims (12)

PATENT CLAIMS:. I. Process to prevent the evaporation of volatile molar fractions, characterized in that the oil surface is covered with a floating layer of small, hole-free hollow bodies and a non-volatile uncovered, whereby the individual hollow bodies have an average diameter of 1 to 500 Su and have a specific gravity of 0.05 to 0.6 (cm3) and in their entirety Take 20 to 70 percent by volume of the floating layer. 2. The method according to claim I, characterized in that the to Protective oil and the non-volatile oil are crude oil, and that the individual hollow bodies an average diameter of 25 to 250 ju and a specific gravity from 0.2 to 0.5 (g / cm3) and in their totality 40 to 55 percent by volume the floating layer. 3. The method according to claim 2, characterized in that the floating layer made of hollow bodies and crude oil is about 2.5 cm thick. 4. The method according to claim 2, characterized in that the Oil-protective floating layer consists essentially of the hollow bodies and not volatile fractions of crude oil represents foam, the crude oil fractions held by capillary forces in the spaces between the hollow bodies will. 5. The method according to claim I, characterized in that the floating layer from hollow bodies and oil a low content of an oil-insoluble, non-volatile Has lubricant. 6. The method according to claim 4, characterized in that the floating layer has a low proportion of an oil-soluble, non-volatile lubricant. 7. A method for producing the according to the method according to claim 2 protective layer used, characterized in that for the purpose of forming a Sludge crude oil mixed with the hollow bodies, whereupon the sludge is poured onto the Applies stored crude oil. 8. A method for producing the in the method according to claim 4 used protective layer, characterized in that there are non-volatile components of the crude oil mixed with the hollow bodies to form a sludge, whereupon man applies the sludge to the stored crude oil. 9. A process for the preparation of those used in the process according to claim 5 Protective layer, characterized in that for the purpose of forming a sludge not volatile fractions of the crude oil with the hollow bodies and a small amount of one Oil-insoluble, non-volatile lubricant mixed together, whereupon you put the mud on the stored crude oil applies. Io. Containing hollow bodies and non-volatile crude oil components Foam for use in the method of claim 2. II. Hollow bodies, a non-volatile, oil-soluble lubricant and foam containing non-volatile crude oil for use in the process Claim 5 12. Combination of one related to the free air Storage tank, the crude oil in this tank and the foam according to claim 10.