shells of water drops so that the wash water can mix with the formation water [brine] originally associated with the oil. T h e degree of desalting from emulsions with specific interfacial surfaces from 1.4"104 to 4.37'104 cm = is the same for the two demulsifiers. The relationships thatwe have obtained are valid for the extremal mixing conditions that we have studied. Hence we can conclude that in carrying out a desalting operation, the degree of mixing of the oil with the wash water must be adjusted according to the type of demuisifier that is being used. LITERATURE CITED i.

2. 3.

D.N. Water 82. V.P. 29. N.M.

Levchenko, N. V. Bergshtein, A. V. Khudyakova, et al., Emulsions of Crude Oil with and Methods of Breaking These Emulsions[in Russian], Khimiya, Moscow (1967), p. Tronov, Emulsion Breaking in Oil Production: [in Russian], Nedra, Moscow (1974), p. Nikolaeva, L. N, Orlov, M. N. Kuznetsova, et al., Neftepererab. Neftekhim., No. 4,

8-10 (1978).

EFFICIENCY OF DEMULSIFIERS OF DIPROKSAMIN TYPE IN RELATION TO HLB F. M. Khutoryanskil, Do N. Levchenko, N. M. Nikolaeva, and E. N. Makal'skaya

UDC 661.185.42:66.066.6: 543.544:678.644-13

The demulsifying efficiency of block copolymers of ethylene and propylene oxides is very much dependent on the composition and structure of the surfactant molecule and on the ratio between its hydrophobic and hydrophilic parts. I t i s known that surfactant molecules are diphilic; and, depending on the ratio between the hydrophobic (lipophilic) and hydrophilic parts, the malecules will display certain affinities for the external medium, i.e., the aqueous and organic phases. The demulsifiersused to bmeak emulsions of water in crude oil are one particular class of surfactants, and hence it is of interest to evaluate this ratio between the hydrophobic and hydrophilie parts of the molecule and thus evaluate the surface activity. In particular, the development of principles for the selection of demulsifiers on the basis of surface activity is extremely important in the synthesis of compounds having specific properties that are needed for this application. As a measure of the surface activity of one particular class of surfactants, i.e., emulsifiers, Griffin [i] proposed a classification based on the hydrophilic--lipophilic balance (HLB). In this classification, each substance that acts as an emulsifier is characterized by a certain value of the HLB; and for a given emulsion, some particular value for the emulsifier HLBcorresponds to maximum stability of the emulsion. No information has been reported in the literature on the relationship between the demulsifying efficiency in breaking emulsions of water in crude oil and the HLB of certain surfactants used as demulsifiers, specifically block copolymers of ethylene and propylene oxides. We have demonstrated the feasibility of using reverse-phase chromatography to determine the HLB for such surfactants [2].

3o

Fig. i. Quality of water separated from Romashkino crude oilemulsion, as a function of HLB of demulsifier.

b.p-2

8

Ig

7'5 17

H~ All-Union Scientific-Research Institute for Petroleum Processing(VNII NP). from Khimiya i Tekhnologiya Topliv i Masel, No. 6, pp. 50-51, June, 1981. 354

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9 1982 Plenum Publishing Corporation

Translated

TABLE Demulsifying power: quantity of water (vol.%) separated from emulsion of water in indicated crude o i l

!

i--7--

0

r

,-1

D-l

D-2 D-3 D-4 D-5 D'6 D-7 D'8

I

5 600[ 21 0001 1 5001 10 5001 5 100 1 320 60O 4 6001

i

5 10 20 20 30 40 50 5O

6,1 5,5 10,0 6,8 8,2 11,7 16,4 8,8

72

49 60 82 85 50 5 86

86 65 78 90 88 60 25 89

77

68 58 81 84 48 42 85

Here we are reporting the use of this chromatographic method in determining the HLB on certain samples of demulsifiers that have been synthesized (block copolymers of the Diproksamin type) over a broad range of contents of oxyethylene and oxypropylene groups (5-50% for the oxyethylene and correspondingly 50-95% for the oxypropylene) and a range of average molecular weights from 600 to 21,000; also, we have obtained data on the demulsifying efficiency of these demulsifiers and its relationship to the HLB. We have established (Table l) that as the content of oxyethylene groups is increased, the HLB of the demulsifiers increases if the comparison is made between compounds of similar molecular weight. As the molecular weight of the demulsifier is increased, while ~maintaining the same content of oxyethylene groups, the HLB decreases. In investigating the relationship between the demulsifier efficiency and its HLG, we determined the demulsifying power of these compounds.* The ~est procedure was as fol!ows~ A specified amount of the demulsifier (in the form of a 2% solution in toluene) was added to the oil. Then water was added, and a stable emulsion of oil and water was prepared by means of a homogenizer. This emulsion was placed in a settler equipped with a central electrode; the assembly was heated in a thermostat to 60~ and a high-strength electric field (E = 3 kV/cm) was imposed. After 60 min, the quantity of water separated from the emulsion was determined, this quantity characterizing the demulsifying power of the compound being tested. Particular attention was given to the selection of the particular emulsion used in this work. The experiments were performed on 10% emulsions of water i n c o m m e r c i a l l y important crude oils (Romashkino, Arlan, and Samotlor) that differ in physicochemical properties and in emulsifying characteristics. Also, conditions were selected for the emulsion preparation (homogenizer speed and mixing time) so that the emulsions would not drop out any emulsified water during the course of an experiment in the electric field in which no demulsifier was present, but would drop out 85-90% of the water when the most effective demulsifier was present in the optimal amount. The demulsifying power of each demulsifier was determined at a dosage equal to the optimal dosage for the most effective demulsifier; in the case of the Romashkino and Arlan crudes, this optimal dosage was 40 ppm by weight, and for the Samotlor crude, which has less tendency to emulsify, it was i0 ppm by weight. The results from these determinations are listed in Table I. For the Romashkino crude oil emulsions, the results are shown in Fig. i as a plot of the quantity of water separated from the emulsion as a function of the HLB. This relationship is extremal. As the HLB is increased from 5.5 to 8~8, the demulsifying power increases (quantity of separated water increases from 49 to 86%); then, as the HLB is further increased from 8.8 to 16.4, the quantity of separated water drops off to 5%. Similar relationships were obtained in the breaking of Arian and Samotlor crude oil emulsions. The most pronounced maxima ~re observed for the Romashkino and Samotlor emulsions, for which a demulsifying power greater than 80% is shown by demulsifiers with HLB from 6.5 to 9.2. In the case of the Arlan emulsions, this high level of demulsifying power is obtained when using demulsifiers with HLB from 6 to 9~ *L. N, Zakharov took part in the experimental work.

355

Thus, we have established a relationship between the efficiency of DSproksamin type demulsifiers in breaking crude oil emulsions and the hydrophilic--lipophilic balance of the demulsifier, a quantity that characterizes the surface activity of surfactants. The most effective demulsifiers are those with HLB from 6 to 9.9. LITERATURE CITED i. 2.

N. Schoenfeldt, Surface Active Ethylene Oxide Adducts, Pergamon, New York (1970). F. M. Khutoryanskii, D. N. Levchenko, E. N. Makal'skaya, et al., Neftepererab. Neftekhim., No. l, 37-38 (1981).

IMPROVEMENT IN DESIGN OF HORIZONTAL ELECTRODEHYDRATORS Ya. I. Pinkovskii

UDC 665.622.43.066.5

The pretreatment of crude oil before refining is a complex problem, which can be solved in a logical manner only through organization of the appropriate process in the oil fields and in the refineries. Specific requirements are placed on the equipment in crude oil pretreating units, particularly electrodehydrators, since the operating efficiency of these units is a major factor determining the degree of corrosion damage to process equipment and also in determining the quality of the end products. In the light of the document approved by the 26th Congress of the Communist Party of the Soviet Union, "Basic Directions of Economic and Social Growth of the USSR in 1981-1985 and in the Period up to 1990," and with further consideration that process units with large individual capacities are being built, the efficiency of crude oil pretreating units and the basic vessels in these units (electrodehydrators) must be increased. This will make it possible for refineries to extend the operating runs of process units, increase the effective capacity of these units, lower the costs of equipment maintenance, and improve the quality of a number of petroleum p r o d u c t s . In many crude oil pretreatment units, there are still hidden reserves that can be utilized to reduce the specific consumption of electrical energy, heat, demulsifiers, and wash water; with the current v o l u m e s o f oil production and refining, such reductions will give very significant economic gains on a nationwide scale. Studies performed at VNIIneftemash on the improvement of horizontal electrodehydrators have been directed toward further reduction of the residual salt content in the crude oil being processed, and also toward discovering reserves for economy in energy resources in crude oil pretreatment. Since it is extremely difficult to model horizontal electrodehydrators with vertical movement of liquid in terms of volume capacity and quality of desalting, all of the experimental horizontal electrodehydrators used in these studies were manufactured in commercial sizes and were investigated in currently operating units, with the participation of engineering institutes such as VNII NP [All-Union Scientific-Research Institute Petroleum Processing], VNIISPTneft' [All-Union Scientific-Research Institute for Special Design Technology for the Petroleum Industry] and Giprovostokneft' [State Research and Design Institute of the Oil Production Industry of the Eastern Regions of the USSR]. The method of investigation that was adopted was found to be extremely effective. The studies were performed under actual commercial conditions in those refineries where the required crude oil is available. Since the experimental vessel is no different from the commercial vessels in diameter, the results obtained in these studies can be used directly to issue recormnendations for regular production of a new vessel, thus bypassing the stage of manufacturing and testing an experimental-commercial model, which usually Qonsumes at least 3 or 4 years. In crude oil pretreatment practice throughout the world, two basically different systems of introducing the oil into the electrodehydrator have gained the most acceptance: oil feed into the bottom section of the vessel in the zone below the electrodes and direct oil feed into the space between the electrodes. For comparative tests on these systems under refinery and oil-field conditions, test stands were built at the Novo-Ufa refinery and the Otradnyi crude oil stabilization plant. All-Union Scientific-Research and Design Institute of Petroleum Machinery Construction (VNIIneftemash). Translated from Khimiya i Tekhnolgiya Topliv i Masel, No. 6, pp. 52-55, June, 1981. 356

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9 1982 Plenum Publishing Corporation