RU2413751C1 - Procedure for complex processing oil containing hydrogen sulphide - Google Patents

Abstract

FIELD: gas-and-oil producing industry.

SUBSTANCE: invention refers to procedures for oil processing and transportation. In particular, the invention refers to the procedure for complex processing oil containing hydrogen sulphide. The procedure consists in dehydration and salt removal of oil containing hydrogen sulphide in a corresponding unit, and in stripping degasification with utilisation of gas dissolved in oil by means of its circulation along a circuit including a unit of oil degasification with a two-stage stripping column and a separator of hot-stage separation, a unit for compression of low pressure gas, and a unit of low pressure gas sweetening. Further, the procedure consists in withdrawal from the circuit of circulation and in utilisation of non-target products. Also, gas sweetening in the circuit of circulation is made upon cooling and separation before compressing. Oil is degassed in the two-stage stripping column, stages of which are communicated by gas only and are equipped with jet disks having fine slit-like punched elements of 2-3 mm² cross section and summary free section 2-4%. Oil is degassed and gas is sweetened at absolute pressure of 0.15-0.25 MPa. Gas is compressed at 0.5-0.9 MPa. A non-target product, gas benzene, withdrawn from the compressing unit and subjected to utilisation, is recycled into oil by means of mixing in the hot stage of separation, thus end oil is withdrawn.

EFFECT: upgraded commodity properties and output of oil, reduced consumption of stripping gas, and simplification of process.

5 cl, 4 ex, 3 tbl, 1 dwg

Description

The invention relates to methods for preparing hydrogen sulfide-containing oil for transportation and can be used in the oil industry.

A known method of integrated oil preparation, including dehydration and desalination and stabilization with the selection of light fractions (gasoline) in the column at a bottom temperature of 274 ° C, alkaline cleaning of gasoline from sulfur-containing compounds (Tronov V.P. Field oil preparation. - M .: Nedra, 1977. - S.226-228).

The disadvantage of this method is the high energy consumption and the formation of an additional amount of hydrogen sulfide due to thermal decomposition of unstable sulfur-containing oil compounds.

A known method for the preparation of hydrogen sulfide-containing oil, including the purge of heated to 100-120 ° C oil purified from hydrogen sulfide gas in a stripper of a special design (Tronov V.P. Field oil preparation abroad. M .: Nedra, 1983. - S.172-173) .

The disadvantage of this method is a significant decrease in the yield of salable oil due to losses of low-boiling gasoline fractions (C ₄ +) with purge gas.

There is also a method of purification of oil from hydrogen sulfide and mercaptans, including dehydration and desalination, and blowing in a column equipped with a regular nozzle or contact devices with direct-flow phase interaction at a temperature of 35-70 ° C, absolute pressure of 0.15-0.50 MPa and specific gas consumption of 4-10 nm ³ per 1 ton of oil. In this case, desorption removal of 80-95% of the hydrogen sulfide contained in the oil is achieved, followed by chemical post-treatment of the oil with a reagent-neutralizer (patent RU 2349365, IPC B01D 19/00, published on March 20, 2009).

The main disadvantage of this method is the need for chemical purification of oil and the ingress of reaction products into commercial oil, which negatively affects the quality of commercial oil.

There is a method of desorption purification of oil from hydrogen sulfide, which consists in countercurrent passage of gas purified from hydrogen sulfide through an oil volume in a column apparatus with an ABP nozzle after the end separation stage at a temperature of 50-60 ° C, an absolute pressure of 0.12 MPa and a specific flow rate of off-gas 3- 9 nm ³ / m ³ (~ 3.5-10.5 nm ³ / t), in which the degree of purification is 92-97% (Sakhabutdinov R.Z., Shatalov A.N., Garifullin PM, Shipilov D.D. ., Mukhametgaleev PP Technology for the purification of oil from hydrogen sulfide. // Transport and oil preparation. - 2008. - No. 7. - P.82-85).

There is another mode of desorption purification and stabilization of oil using an apparatus such as ABP (Installation for deep degassing of oil // NT NEFT AND GAS / Technology and equipment for the preparation and processing of oil and gas / http: /www.ntng.ru/index 1_5.html , 2007, NT Oil and Gas LLC). In accordance with this regime, oil is degassed at a temperature of 45 ° C, an absolute pressure of 0.25 MPa, a flow rate of a desorbing associated gas of ~ 10 nm ³ / t (~ 11.5 nm ³ / t). In this case, the residual content of hydrogen sulfide in oil decreases from 1000 mg / L to the level of 50 mg / L (~ 57 ppm) and lower, and the saturated vapor pressure (DNP) - to 470 mmHg (62.6 kPa). Note that in accordance with GOST R 51858-2002, the residual content of hydrogen sulfide in oil of type 1 should not exceed 20 ppm, and the DNP for oil of group 1 - 66.7 kPa (500 mm Hg), the water content - 0.5 wt.%.

The disadvantage of this method is to reduce the yield of salable oil due to the loss of a significant amount of propane-butane and gasoline fractions while increasing the flow rate of stripping gas to increase the degree of oil refining.

Closest to the proposed invention is a method for the preparation of oil and gas, including dehydration and desalination of oil in the corresponding unit, desorption degassing using gas dissolved in oil by circulating it along a circuit including an oil degassing unit with a desorption column and a hot separation stage separator, a compression unit low-pressure gas, low-pressure gas desulphurization unit, withdrawal from the circulation circuit and disposal of non-target products (Andreev E.I., Lesukhin SP the process of extraction of hydrogen sulfide and stabilization of oil from the Tengiz field by blowing with oil gas // The problem of developing oil fields with anomalous properties. - Giprovostokneft, Kuibyshev: 1983. - S.99-111 - prototype). In this method, desorption degassing of oil is carried out using an ABP packed column with a separation capacity of 5 theoretical contact stages. The method allows to combine the processes of stabilization of oil and its purification from hydrogen sulfide.

The disadvantage of this method is the low degree of purification and low oil yield due to the loss of light gasoline components (C ₄ +) due to the high consumption of stripping (stripping) gas, as well as the inevitability of the allocation and disposal of non-target liquid-phase (purified and unrefined) products. The high gas flow rate is explained by the use of columns with insufficiently high separation ability.

The objective of the invention is to increase the marketability and yield of oil, reducing the consumption of stripping gas, as well as simplifying the technology.

The problem is solved by the described method for the comprehensive preparation of hydrogen sulfide-containing oil, including dehydration and desalination of hydrogen sulfide-containing oil in the corresponding unit, desorption degassing using gas dissolved in oil by circulating it through a circuit including an oil degassing unit with a two-stage desorption column and a separator with a hot separation stage, a compressor block low-pressure gas, low-pressure gas desulfurization unit, withdrawal from the circulation circuit and disposal th non-target products in which the characterizing features are as follows:

- the implementation of gas desulfurization in the circulation loop after cooling and separation prior to compression;

- oil degassing in a two-stage desorption column, the cascades of which are connected only by gas and equipped with inkjet plates with small slit-like perforated elements with a section of 2-3 mm ² and a total free section of 2-4%;

- oil degassing and gas desulfurization at absolute pressure of 0.15-0.25 MPa, gas compression at 0.5-0.9 MPa;

- recycling derived from the compression unit and to be disposed of inappropriate product (gas gasoline) into oil by mixing in a hot separation stage with the release of marketable oil.

In addition, the hallmarks of the proposed method are:

- the implementation of gas desulfurization with an aqueous solution of amines using in the absorption and desorption columns of inkjet plates with small slit-like perforated elements with a cross section of 2-3 mm ² and a total free section of 8-12%;

- recirculation of non-target products, condensates of hydrocarbons and water removed from the oil degassing and gas desulphurization units, to the dehydration and desalination unit;

- introducing into the circulation circuit of the gas dissolved in the oil a calculated amount of additional hydrocarbon gas, the introduction of the purified gas in front of the degassing column, and the crude gas in front of the gas desulfurization unit;

- Utilization of the balance excess of purified gas by using the unit in autonomous power supply systems.

The circulation of gas dissolved in oil along the circuit "oil degassing unit - gas desulphurization unit - gas compression unit - oil degassing unit" allows to simplify the oil production process flow diagram by eliminating the need to clean a liquid-phase non-target product (gas gasoline). The fact is that the bulk of the liquid-phase non-target product is formed in the compression unit after cooling and separation. In the proposed method, the gas is desulfurized before compression, therefore, separate cleaning of this product is not required. A similar solution is known from the literature (Persiyantsev MN Improving the processes of oil and gas separation in industrial conditions. - M .: Nedra - Business Center LLC. 1999. - P.225-233). In this method, gas from the column is sent directly to the desulfurization, as a result, high-boiling hydrocarbons get there, which is undesirable for the desulfurization process (enhances foaming). In the proposed method, this disadvantage is eliminated by cooling and gas separation after the degassing column before desulfurization.

Oil degassing in a two-stage column, the cascades of which are connected only by gas (i.e., the gas flow passes through the plates of both stages of the column, and the oil introduced by two equal flows to the upper plates of the cascades separately, passes separately across all plates of each cascade, without mixing of these oil flows) and equipped with inkjet plates with small slit-like perforated elements with a section of 2-3 mm ² and a total free section of 2-4% increases the efficiency of the oil stabilization process (reduction of the residual sulfur content hydrogen in oil and the pressure of its saturated vapors, as well as the flow rate of the stripping gas) by halving the liquid: gas ratio, the formation of a thin-layer finely dispersed oil stream, and the practically absence of a liquid dip even with a very low gas flow rate. As an element of such plates, for example, a well-known canvas can be used (patent RU 2236900, IPC 7 В01J 19/32, published September 27, 2004).

Carrying out oil degassing and gas desulfurization at an absolute pressure of 0.15-0.25 MPa, gas compression at 0.5-0.9 MPa contribute to the production of oil with the optimal combination of yield and commercial properties (saturated vapor pressure, DNP, and residual hydrogen sulfide content ) This is explained as follows:

- if the pressure in the oil degassing column is below the specified range, it will not be enough to carry out gas desulfurization;

- if the pressure is higher, it does not provide the required quality of oil;

- when compressing gas below the specified limit, the yield of salable oil is reduced due to less condensation of gas gasoline;

- when compressing gas above the specified limit of the DNP of commercial oil may exceed the permissible value, while the consumption of stripping gas also increases.

The authors are not aware of the method of integrated oil treatment, carried out precisely with such a combination of pressures in the blocks of oil degassing, gas desulfurization and gas compression.

Recycling of the non-target product in the liquid phase, gas gasoline removed from the compression unit and to be disposed of, into oil by mixing in the hot separation stage allows to increase the yield of marketable oil due to the return of gas gasoline.

The implementation of gas desulfurization with an aqueous solution of amines using in the absorption and desorption columns of jet plates with small slit-like perforated elements with a cross section of 2-3 mm ² and a total free section of 8-12% helps to increase the efficiency of the known gas purification process (Kuznetsov A.A., Sudakov E.N. Calculations of the main processes and apparatuses for the processing of hydrocarbon gases: Reference manual. - M .: Chemistry, 1983. - P.5-55). Efficiency is increased due to fine dispersion of the absorbent and the formation of a developed interface.

Recycling of non-target products in the liquid phase (gas gasoline and water) to be disposed of from the oil degassing and gas desulphurization units to the oil dehydration and desalination unit helps simplify the technology by eliminating the need for their purification. A method involving the recirculation of gasoline in the dehydration and desalination unit of an oil preparation unit is known from the literature (Zaripov A.G., Pozdnyshev G.N. et al. Oil preparation with recirculation of a part of unstable gasoline to the stage of dehydration and desalination // Collection, preparation and oil and water transport - All-Union Research Institute for the Collection, Preparation and Transport of Oil and Oil Products (VNIISPTneft), Ufa: 1976. - P.63-69). In the proposed method, the amount of this gasoline is small (not more than 0.1 wt.%) Due to a clearer separation of gas and liquid in the oil desorption column, which reduces the additional cost of recirculation.

The introduction of the calculated amount of additional hydrocarbon gas into the circulation circuit of the gas dissolved in oil, the purified gas in front of the degassing column and the crude gas in front of the gas desulfurization unit, allows the oil preparation process to be carried out with insufficient dissolved gas in it.

Disposal of the balance excess of purified gas (if there is an excess of its own gas dissolved in oil) by using the unit in autonomous energy saving systems (see, for example, OPRA Technologies. Energy for you and your business. - P.1-17. Www.mttby.com/ img / opra / pdf), together with the previous distinguishing feature, ensures its operation without involving external heat and electric energy, and also reduces transportation costs.

The non-target product (hydrogen sulfide concentrate) removed from the gas desulfurization unit can be disposed of in the elementary sulfur production unit, for example, by the Klaus method, which allows the entire process of complex oil preparation to be carried out without environmental pollution.

Thus, the set of distinctive features of the proposed method allows to achieve the claimed technical result: improving the marketability and yield of oil, simplifying the technology of its preparation, reducing the consumption of stripping gas. In addition, it becomes possible to self-supply the installation with heat and electric energy and reduce transportation costs.

An analysis of the known methods and installations for the preparation of oil shows that in the given field of science and technology there is no object similar to the claimed combination of features with the achievement of the same technical effect.

The invention is illustrated by the flowchart shown in the drawing.

Oil from the end stage of separation goes to the unit (UKPN) via line 1. After mixing with non-target products recycled through line 2 in the liquid phase from the oil degassing and gas desulphurization units, it is fed through line 3 to the dehydration and desalination unit 4. line 5 also serves fresh water, line 6 discharges produced water, and line 7 displays desalted and dehydrated oil and sends it to block 8 for desorption oil degassing. This oil stream is divided into two equal streams and fed through lines 9 and 10 to a two-stage degassing column 11, respectively, to the upper plates 12 and 13 of the cascades. All columns of the column are of the jet type and are equipped with small slit-like perforated elements 14. At the bottom of the column 11, circulating stripping (stripping) gas is supplied via line 15. Oil from the column 11 is sent via line 16 to a buffer tank - separator (hot separation stage) 17, where the final degassing of the oil is carried out together with the non-target product in the liquid phase (gas gasoline) from the compression unit via line 18 in the liquid phase (gasoline). The separated mixture of oil and gas gasoline is discharged through line 19 and pump 20 is sent via line 21 to a heat exchanger 22, in which this mixture is cooled by heat transfer of the original oil and removed from the unit as commercial oil via line 23. The separation gas is removed from the buffer tank - a separator 17 and together with a gas stream 25 taken from the top of the column 11, as well as an additional crude gas stream 26, are fed through line 27 to the refrigerator 28 and then through line 29 to the separator 30. The gas phase from the separator 30 is withdrawn via line 31 and direction t for amine treatment unit 32 provided with a hydrogen sulphide absorption column with an aqueous solution of diethanolamine and stripping column to a reboiler to regenerate the absorbent. The liquid non-target hydrocarbon phase is withdrawn from this unit via line 33 and, together with the non-target liquid phase (mixture of hydrocarbons and water) from the separator 30 output via line 34, is recycled to the feed oil via line 2. Acid gas, hydrogen sulfide concentrate, is sent from the desulfurization unit 32 via line 35 to the elemental sulfur production unit The purified gas from block 32 is fed through line 36 to compression unit 37. After cooling and separation, the compressed gases are removed via line 38 and, together with an additional stream of purified gas supplied through line 39, are recycled to the bottom of the desorption column through line 15 as a stripping gas ( total gas).

The balance excess of purified and compressed gas is discharged via line 40 and sent as fuel for generating heat and electric energy to the mini-TPP 41, for example, to a gas turbine (or gas piston) unit with a cogenerator for heat recovery. A portion of the heat flux is removed via line 42 and used in the reboiler of the amine gas purification unit 32. Another portion of the heat flux is withdrawn via line 43 and used in the dehydration and desalination unit 4 for heating oil. These parts of the heat flow used for technological purposes are necessary and sufficient for the implementation of the method. The low-temperature part of the heat flux is removed via line 44 and used in the UKPN heating system. The resulting electrical energy is removed via line 45 and used to meet the internal needs of the installation and for other purposes.

The described method is illustrated by three calculation examples. A fourth example relates to a known method. Table 1 shows the main material flows of the installation. The flow rates in wt.% Are calculated for convenience regarding dehydrated and desalted oil, gas flow rates are given without taking into account hydrogen sulfide. Table 2 presents the operational parameters of the columns of the blocks desorption degassing of oil and amine gas purification.

The data in tables 1 and 2, the data refer to the proposed method. Table 3 summarizes the main indicators of the proposed and known methods.

It should be noted that heating the oil in the furnace in the proposed method to 70 ° C is associated with the dehydration and desalination of highly viscous oil - the raw materials of the designed installation.

Example 1 illustrates the possibility of implementing the process of oil preparation without involving additional stripping gas in the circulation circuit. However, in this case, the balance excess of gas used as fuel is insufficient for the self-supply of the installation with the thermal energy required by the technology.

In Example 2, the necessary and sufficient amount of thermal energy required by the technology is provided by introducing an additional hydrocarbon gas purified from hydrogen sulfide.

Example 3 illustrates the possibility of fully providing the installation with thermal energy, including its heating system, as well as electric energy.

Example 4 relates to a known method. Table 3 compares the main indicators of the proposed and known methods.

As can be seen from the above data, the main process indicators in the proposed method compared to the prototype are improved:

- in marketable oil, the hydrogen sulfide content is reduced by 6.4 ppm and saturated vapor pressure by 129 mm Hg;

- the oil yield rises by an average of 0.8 wt.%;

- the consumption of stripping gas is reduced by 2.4 times;

- selection and purification of gas gasoline from hydrogen sulfide is not required.

The above examples prove that the proposed method allows to solve the problem of improving the marketability and oil yield while simplifying the technology and significantly reducing the consumption of stripping gas.

Table 1 Name, flow rate and flow number Flow rate Example 1 Example 2 Example 3 Oil for installation (1): wt.% 104.69 104.69 104.71 kg / h 238,126.6 238,126.6 238,126.6 including: gases 2,407.9 2,407.9 2,407.9 H ₂ s 119.1 119.1 119.1 H ₂ O 11896.8 11896.8 11896.8 Dehydrated and desalted oil (7): wt.% 100.00 100.00 100.00 kg / h 227474.7 227,456.7 227,450.9 including: gases 2577.5 2,409.7 2,409.9 H ₂ s 109.1 109.1 109.1 H ₂ O 1136.8 1136.8 1136.8 Circulating stripping gas (38): wt.% 0.8439 0.5690 0.3757 kg / h 1908.8 1542.4 854.2 including: gases 1623.6 1294.3 671.8 H ₂ s 0,0515 0.0426 0.0191 H ₂ O 7.5 6.4 3,7 Additional stripping gas (39): wt.% - 0,0324 0,1224 kg / h - 73.7 278.3 including: gases - 71.2 268.7 H ₂ s - 0.0147 0,0557 H ₂ O - 0,0007 0.0028 Commodity oil (23): wt.% 99.74 99.67 99.43 kg / h 226890.3 226680.3 226162.0 including: gases 2265.7 2083.2 1676.1 H ₂ s 1.17 1.17 1.12 H ₂ O 940.3 962,2 973.2 Fuel Gas (40): wt.% 0,0600 0.1982 0.5213 kg / h 136.4 450.9 1185.9 including: gases 116.0 378.4 932.5 H ₂ s 0.004 0.012 0,020 H ₂ O 0.539 1,871 4.0 Sour gas (35): wt.% 0,0604 0.0591 0,0572 kg / h 137.4 134.5 130.1 including: gases 23.9 20.8 16.8 H ₂ s 107.9 108.3 108.1 H ₂ O 5.5 5,4 5.2

table 2 Name and dimension of the parameter in columns The numerical value of the parameter Example 1 Example 2 Example 3 Desorber unit desorption oil degassing: - top temperature, ° С 72 70 69 - temperature in the feed zone, ° С 70 70 70 - bottom temperature, ° С 71 70 70 - top pressure, MPa 0,200 0,200 0,200 - pressure in the feed zone, MPa 0,200 0,200 0,200 - bottom pressure, MPa 0.225 0.225 0.225 Absorber gas purification unit: - top temperature, ° С 42 42 42 - temperature in the feed zone, ° С 35 35 35 - bottom temperature, ° С 44 44 44 - top pressure, MPa 0.160 0.160 0.160 - pressure in the feed zone, MPa 0.180 0.180 0.180 - bottom pressure, MPa 0.180 0.180 0.180 Gas purification unit desorber: - top temperature, ° С 113 114 114 - temperature in the feed zone, ° С 108 108 108 - bottom temperature, ° С 121 121 121 - top pressure, MPa 0.170 0.170 0.170 - pressure in the feed zone, MPa 0.174 0.174 0.174 - bottom pressure, MPa 0.190 0.190 0.190

Table 3 Name and dimension of an indicator The numerical value of the indicator Proposed technology Known technology Example 1 Example 2 Example 3 Example 4 Specific consumption of additional stripping gas, nm ³ / t - 0.396 1,495 - Specific consumption of total stripping gas, nm ³ / t 4,616 4,357 3,781 14,386 The hydrogen sulfide content in the oil in front of the degassing unit, ppm 480 480 480 1198 The content of hydrogen sulfide in marketable oil, ppm 5,0 5,0 5,0 11,4 The saturated vapor pressure of the oil in front of the degassing unit, kPa (mmHg) 60.6 (455) 60.6 (455) 60.6 (455) 77.9 (584) Saturated vapor pressure of salable oil, kPa (mmHg) 48.2 (362) 45.4 (340) 38.2 (287) 62.3 (467) The yield of oil, wt.% 99.74 99.67 99.43 98.78 The number of theoretical plates in the desorption column, pcs. 12 12 12 5 Absolute pressure in the desorption column, MPa 0,200 0,200 0,200 0.250 Oil heating temperature in the furnace, ° С 70 70 70 40 The degree of self-sufficiency in energy,%: - thermal energy required by technology thirty one hundred one hundred - - thermal energy for the heating system of the installation - - one hundred - - Electric Energy - - more than 100 - The need for selection and purification of gas gasoline from hydrogen sulfide no no no Yes

Claims (5)

1. A method for the comprehensive preparation of hydrogen sulfide-containing oil, including dehydration and desalting of hydrogen sulfide-containing oil in the corresponding unit, desorption degassing using gas dissolved in oil by circulating it along a circuit including an oil degassing unit with a two-stage desorption column and a hot separation stage separator, low gas compression unit pressure unit, desulphurization of low pressure gas, withdrawal from the circuit and disposal of inappropriate products, characterized in that Desulfurization of gas in the circuit is carried out after cooling and separation to compression, degassing of oil is carried out in a two-stage stripping column, which cascades are connected only by the gas jet and provided with small plates of expanded slotted section elements 2-3 mm ² and the total free section of 2- 4%, oil degassing and gas desulfurization is carried out at an absolute pressure of 0.15-0.25 MPa, gas compression is performed at 0.5-0.9 MPa, taken out of the compression unit and the non-target product to be disposed of, gas free Nzin, recycle into oil by mixing in a hot separation stage with the release of marketable oil. 2. The method according to claim 1, characterized in that the gas desulfurization is carried out with an aqueous solution of amines using in the absorption and desorption columns of inkjet plates with small slit-like perforated elements with a section of 2-3 mm ² and a total free section of 8-12%. 3. The method according to claim 1, characterized in that non-target products, condensates of hydrocarbons and water, which are removed from the oil degassing and gas desulphurization units, are recycled to the oil to the dehydration and desalination unit. 4. The method according to claim 1, characterized in that a calculated amount of additional hydrocarbon gas is introduced into the circulation circuit of the gas dissolved in the oil, the purified gas being introduced in front of the oil degassing column, and the crude gas in front of the gas desulfurization unit. 5. The method according to claim 4, characterized in that the balance excess of purified gas is disposed of by using the installation in autonomous power supply systems.

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