RU2442816C1 - Device for removing hydrogen sulphide and low-molecular mercaptans from oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: The invention relates to raw hydrocarbons processing plants and can be used in oil industry when hydrogen sulphide and low-molecular mercaptans are removed from sulphurous oil. The invention relates to purifier which removes hydrogen sulphide and low-molecular mercaptans from oil. The purifier comprises a sulphurous oil feeding pipe, a oil separator connected in series with the gas pipeline by pipes, an oil pump, a mixing unit, an oxidation reactor, a high pressure separator with gas pipe and purified oil storage tanks, a tank for preparation and storage of the catalyst alkaline solution fitted with dosage pumps where their outlet is connected with the inlet of the oil pump, an air compressor with its outlet connected to the inlet of the mixing unit, and a flare line. The device is also fitted with a water pipe feeding fresh washwater. The water pipe is connected to the pipeline between the high-pressure and the low-pressure separators, furthermore, the gas feeding pipes of oil separator and low pressure separator are connected by a drain gas pipe; the gas pipe of the high pressure separator is connected with the flare line. It is also connected with the purified oil storage tanks through the shunt pipe with a pressure regulator.

EFFECT: increase of stock oil quality in order to conform with the GOST R 51858-2002 standard.

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Description

The invention relates to hydrocarbon processing plants and can be used in the oil industry for field purification of hydrogen sulfide-containing oil from hydrogen sulfide and low molecular weight mercaptans, mainly at remote sites not equipped with a gas collection system.

A known installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans (A.M. Mazgarov, A.F. Vildanov, V.N.Salin. Purification of oil and oil products from mercaptans and hydrogen sulfide. Chemical and oil and gas engineering. 2003. No. 12, p. 28 -29), which includes a section for the preparation and storage of a catalyst complex (aqueous-alkaline solution with a catalyst) as a part of tanks with a pump for mixing chemical reagents, a section for feeding a solution with a catalyst into oil as a part of metering pumps and a static mixer, an air supply section ha consisting of an air compressor and receiver recovery section of the solution container in the composition of the residual liquid, pumps, heat exchangers, exhaust air filter, RVS storage tanks of refined oil.

The disadvantage of the installation is that it requires dosing of chemical reagents into the oil stream, the reaction products of hydrogen sulfide with which re-pollute the partially refined (dehydrated and desalted) oil, which is manifested in an increase in the content of the aqueous phase and a negative effect on the results of analyzes to determine the concentration of chloride salts according to GOST 21534-76. The installation includes a wide variety of equipment and requires several technological operations related to the preparation of a mixture of solutions, dosing the mixture into a high-pressure oil stream while mixing it with air, carrying out oxidative oil purification during pipeline transportation, settling of raw materials in tanks and the regeneration of the solution, including its heating, which determines significant material and operating costs, including energy. In addition, during the operation of the unit, oil losses in the form of light fractions are large together with the exhaust air from unsealed RVS tanks, and when cleaning hydrogen sulfide-containing oils of high viscosity, the efficiency of the oil sludge process is low even with a significant residence time in the tanks, which leads to the need for constant replenishment of the process fresh portions of reagents and the inappropriateness of their regeneration.

A known installation for the purification of oil and gas condensate from hydrogen sulfide and low molecular weight mercaptans (RU 2120464 C1, C10G 27/06, C10G 27/10, publ. 01/20/1998, Bull. No. 29), including the supply pipe of sulfur dioxide, raw material tank, raw material pump, a device for mixing air with raw materials, a heater, a reactor, a settling tank and a separator tank in front of storage tanks for refined oil, alkali solution and catalyst solution tanks, metering pumps, an air inlet device.

The installation allows to reduce the concentration of hydrogen sulfide and low boiling mercaptans in oil, to reduce material costs for oil refining due to the possibility of dosing the reagents in the oil stream at the intake of a raw pump and eliminating the section for alkaline solution regeneration and loss of hydrocarbons with exhaust air through the use of special separation equipment condition of their supply to the gas collection system.

The disadvantage of the installation is the possibility of oil contamination by reaction products, primarily elemental sulfur during the catalytic oxidation of hydrogen sulfide, as a result of which the "imaginary" amount of chloride salts and reaction water increase in oil, which, if the content of hydrogen sulfide and mercaptans is significant in oil, can lead to exceeding these indicators above the values required by GOST R 51858-2002. The use of two separate sections for the preparation and dosing of reagents increases the metal consumption of the installation and leads to the need for monitoring the exact dosage of alkaline solution and catalyst.

Closest to the proposed one is an installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans, designed to implement a method for the preparation of hydrogen sulfide-containing oil (RU 2269566 C1, C10G 27/06 C10G 19/02, publ. 02/10/2006, Bull. No. 4), including a supply pipeline sulphurous oil, oil-gas separator connected in series with pipelines, oil pump, mixing device, oxidation reactor, high-pressure separator-settler with gas pipeline, low-pressure separator with gas pipeline and outlet pipes wire in refined oil storage tanks, cooking and storage capacity of the catalyst with alkali solution dosing pump, the output of which communicates with the inlet of the oil pump, air compressor, the output of which is connected to the input of the mixing device, a discharge pipeline connected to a flare line or a gas gathering system.

The installation allows to obtain the required indicators of oil quality by the concentration of hydrogen sulfide and light mercaptans and reduce the negative impact of the reaction products of hydrogen sulfide with reagents on the quality of the oil by the content of the aqueous phase and the concentration of chloride salts due to the partial blowing of hydrogen sulfide from oil in the heated oil separator when the exhaust gas is fed into it with nitrogen from a high pressure separator and reducing the volume of reagents supplied to the oil (alkaline solution with a catalyst).

A disadvantage of the known installation is the limited area of its cost-effective use - only at facilities equipped with a gas collection system. In most cases, plants that implement oxidative methods for oil refining using reagents are used at remote sites where there is no gas collection system. Under these conditions, the supply of exhaust air, consisting of 60-65% of nitrogen, to the intake of the oil separator contributes to the fact that, together with hydrogen sulfide, a significant amount of light hydrocarbons, mainly propane and butane-pentane fractions, pass from the oil to the gas phase, which determines a decrease the output of marketable oil, an increase in losses, along with losses from reservoirs for storing refined oil, when a nitrogen-hydrocarbon mixture is supplied to a torch for burning (or a scattering candle), and an increase in the negative load on the environment. In addition, the technical and technological interconnection of the elements of the installation determines the cyclic mode of its operation, which consists in constant adjustment and control of air and reagent consumption in connection with continuously changing indicators for the initial concentration of hydrogen sulfide in oil at its outlet from the heated oil separator and the need for periodic reduction or increase the cost of reagents and air involved in the process of oxidative purification of oil from hydrogen sulfide and light mercaptans, which negatively affects the floor enii stable quality parameters of oil. In this regard, the installation does not guarantee oil quality in all respects according to GOST R 51858-2002, especially with a high initial content of hydrogen sulfide in oil over 400-500 ppm, since the efficiency of removing hydrogen sulfide from oil in the separator is constantly changing and does not exceed in most cases 40-45%, which determines the use of a sufficiently large volume of chemical reagents, since the consumption of alkaline reagent with a change in the initial concentration of hydrogen sulfide changes to a lesser extent than air consumption. Therefore, with a high value of the concentration of hydrogen sulfide in oil, especially highly viscous, there is a high probability of exceeding the quality indicators of oil in the content of the aqueous phase and the concentration of “imaginary” chloride salts with an excess of supplied alkaline reagent based on the minimum amount of exhaust air from the high-pressure separator-settler, and with insufficient supply of reagent, calculated on the maximum amount of exhaust air directed into the oil pipeline in front of the oil separator, - and for owl proportion of low molecular weight of hydrogen sulfide and mercaptans. The technological method of sludge after the reactor and recirculation of the reaction mixture (almost completely spent reagent) for the intake of the feed pump proposed in the installation implies an increase in the load on it and the installation as a whole, not only with the reagent, but, to a greater extent, with the already refined oil, since qualitative sedimentation of a reagent having a density close to the density of oil during the preparation of viscous oils is unlikely under conditions of simultaneous separation of exhaust air from oil, which ultimately also negates but the impact on the quality of oil refining and requires higher energy costs.

The technical objectives of the invention are to improve the quality of oil purification from hydrogen sulfide and low molecular weight mercaptans by reducing the proportion of the aqueous phase in crude oil, to eliminate the negative influence of the reaction products of reactants with hydrogen sulfide and low molecular weight mercaptans when determining the concentration of chloride salts in oil, to stabilize the operating parameters of oil refining by maintaining constant costs of reagents and air supplied to the oil at the stage of oxidation of hydrogen sulfide and mercaptans, and SN voltage losses light hydrocarbons from oil separators and the purified oil reservoir by optimizing the distribution of the gas streams from the separators of high and low pressures.

The stated technical problem is solved by the described installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans, including a sulfuric oil supply pipeline, an oil separator with a gas pipeline connected in series, an oil pump, a mixing device, an oxidation reactor, a high pressure separator with a gas pipeline, a low pressure separator with a gas pipeline and tanks storage of refined oil, the capacity for the preparation and storage of the catalyst alkaline solution with metering pumps, outlet d which communicates with the inlet of the oil pump, air compressor, the output of which is connected to the input of the mixing device, and flare line.

New is that to improve the quality of oil purification from hydrogen sulfide and low molecular weight mercaptans by reducing the proportion of the aqueous phase in marketable oil and to eliminate the negative effect of the reaction products of reactants with hydrogen sulfide and low molecular weight mercaptans on determining the concentration of chloride salts in oil, stabilizing the operating parameters of oil refining, to reduce the loss of light oil hydrocarbons from separators and refined oil tanks, it is additionally equipped with a fresh wash water conduit connected to m to conduit separators between high and low pressure, wherein the oil separator pipelines and low pressure separator connected retractable pipeline and a high-pressure separator communicates with a pipeline and a flare line through a jumper tube valve "behind" - with storage tanks of refined oil.

Also new is that in order to achieve oil quality indicators in accordance with the requirements of GOST R 51858-2002 when cleaning high-viscosity oils with a high initial concentration of hydrogen sulfide due to an increase in the cleaning depth for all quality indicators, an electric dehydrator is placed on the pipeline between the connection to the water main and the low pressure separator .

The drawing shows a schematic diagram of the proposed installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans.

The installation comprises a supplying oil pipeline 1 of sulfur dioxide, an oil separator 2 with a gas pipeline 3, an oil pump 4, a container 5 for preparing and storing a catalyst alkaline solution, metering pumps 6, the discharge of which is connected by a pipe 7 to a pump 4, an air compressor 8 with a pipe 9, a mixer 10, an oxidation reactor 11, a high pressure separator 12 with a gas pipe 13, a pipe 14 with a fresh wash water conduit 15 connected to it, an electric dehydrator 16 with a water discharge pipe 17 connected to the input of the preparation oil production, and a discharge oil pipe 18, a low pressure separator 19 with a gas pipe 20 connected by a gas pipe 21 to a gas pipe 3 of an oil separator 2, refined oil storage tanks 22 connected through the gas phase via a pipe jumper 23 on which the 24 "valve is installed after itself ", To the gas pipeline 13 connected to the flare line 25.

Installation of oil purification from hydrogen sulfide and low molecular weight mercaptans works as follows. Hydrogen sulfide-containing oil (undergoing stabilization, deep dehydration and desalination, or only deep dehydration) from the oil preparation unit (UPN) is fed through oil supply line 1 to oil separators 2, from where gas is supplied through gas pipeline 3, for example, to the UPN furnace for heating crude oil. The degassed oil after the separator 2 is sent to the intake of pump 4, where from the tank 5 by metering pumps 6, a catalyst complex (CPC), which is an alkaline solution, preferably a 25% solution of ammonia NH ₃ , with a catalyst, is fed through pipeline 7. Intensive mixing of the solution with oil takes place in the working cavity of the pump. After pump 4, a stoichiometric amount of air is introduced into the oil stream by air compressor 8 through line 9, which is mixed with oil and an alkaline solution at a pressure of 1.0-1.5 MPa in mixer 10. Next, the mixture of oil, air and reagent is sent to the oxidation reactor 11 where the main oil refining process is carried out due to the oxidation of hydrogen sulfide to elemental sulfur, and low molecular weight mercaptans to disulfides. The reaction products that form the reaction of reagents and oxygen in the air with hydrogen sulfide, mercaptans, and naphthenic acids in oil and water that is also released during the reaction worsen the oil quality indicators: the mass fraction of water increases, the reaction products negatively affect the analysis of the determination of chloride salts in oil according to the method of GOST 21534-76 (method A - titration of an aqueous extract), which manifests itself in the form of an increase in the concentration of chloride salts in oil. After the reactor 11, oil is fed to a high pressure separator 12, from which the exhaust air (nitrogen above 60% with light hydrocarbons) separated from the oil at a pressure of about 0.2-0.3 MPa enters the gas pipeline 13, and the purified oil is sent to the pipeline 14 To remove the reaction products from the oil volume in order to bring its quality in accordance with the requirements of GOST R 51858-2002 and to exclude their influence on the results of determining the concentration of chloride salts in the oil stream transported through pipeline 14, fresh flushing water is fed through conduit 15 do, the amount of which is selected empirically, based on the volume of oil and the initial concentration in it of hydrogen sulfide and low molecular weight mercaptans. Laboratory and field studies show that the amount of fresh water for flushing oil from polluting reaction products is from 2 to 10% of the volume of oil. When refining light oils with a viscosity of up to 20-30 MPa · s with a hydrogen sulfide content of 150–200 ppm and mercaptans up to 50–100 ppm, the oil treated with fresh water is transported through all subsequent structures to its storage tanks, where they are trimmed and dumped during sludge the entire aqueous phase with the reaction products. When refining heavy oils with a viscosity of over 60 MPa · s with a high concentration of hydrogen sulfide in excess of 250-300 ppm, the oil after fresh water is introduced is additionally sent to an electric dehydrator 16, where at a pressure close to the pressure in the high-pressure separator 12, it is exposed to an electric field, as a result which is the process of effective sludge of the aqueous phase (a mixture of produced water, water, originally present in an alkaline solution and fresh wash water) with reaction products and residual chloride salts. The settled water through pipeline 17 is fed to the UPN, and oil is sent via pipeline 18 to a low pressure separator 19, where at a pressure of about 0.05-0.1 MPa, the gas phase containing up to 90% hydrocarbons is separated from the refined oil. Gas from the separator 19 is sent to the gas pipeline 20 and through the off-gas pipeline 21 it is fed into the gas pipeline 3 of the separator 2 and then a mixture of gases with a reduced content of hydrogen sulfide is used in UPN oil heating furnaces or for other oilfield needs. This technique allows you to completely eliminate the loss of hydrocarbons from the separator 19 low pressure and reduce the corrosiveness of the gas supplied to the furnace UPN. Oil from the separator 19 is sent to storage tanks 22, which are operated in the "filling-pumping" mode. When oil enters reservoirs 22, residual gas is released as a result of pressure reduction, which when filled together with the products of evaporation from the mirror, the surface of the oil is discharged through the breathing valves into the atmosphere. To reduce oil losses in the form of light fractions during the subsequent emptying of the reservoirs 22, which is accompanied by a decrease in pressure in their vapor spaces, in them through the jumper 23 through the valve 24 "after themselves" by a signal from a pulse tube, fixing the moment of pressure reduction to a certain value, from gas line 13 of the high-pressure separator 12, gas with a high nitrogen content begins to flow, as a result of which a nitrogen cushion is formed in the tanks, which reduces the volatility of oil and the loss of its light fractions and subsequent filling of the reservoirs 22, since with increasing pressure in the reservoirs and opening the breathing valves, nitrogen will be emitted into the atmosphere. An additional effect, in addition to reducing the negative load on the environment and the loss of hydrocarbons from the high pressure separator 12 and tanks 22, from the connection of the gas pipeline 13 and tanks 22 through the pipe jumper 23, is to reduce the fire hazard and reduce the corrosiveness of the medium in the tanks 22 by eliminating the ingress of in them air. When filling the reservoirs 22, the nitrogen-hydrocarbon mixture from the high-pressure separator 12 is sent through the gas line 13 to the flare line for combustion (or dispersion). When accumulating in the tanks 22 a certain amount of the aqueous phase, it is periodically dumped into the tanks of treatment facilities.

The proposed installation allows the purification of oil from hydrogen sulfide and low molecular weight mercaptans to the requirements of GOST R 51858-2002 and compared with the known has the following advantages:

- has a wide scope regardless of the existing infrastructure for the collection and use of petroleum gas;

- the quality of oil refining is improved by reducing the proportion of the aqueous phase and eliminating the negative effect of the reaction products of reagents with hydrogen sulfide and low molecular weight mercaptans on determining the concentration of chloride salts in oil as a result of stabilization of operating parameters while maintaining constant flow rates of reagents and air and ensuring effective washing of oil from reaction products , which also provides simplification of control and regulation of the oil refining process;

- reduced oil losses in the form of light hydrocarbons from reservoirs and separators by optimizing the distribution of gas flows from these devices;

- the fire hazard of the facilities is reduced due to the exclusion of air from entering the atmospheric oil storage tanks and at the same time the corrosiveness of the gas medium in them is reduced.

The proposed installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans is technologically advanced and simple to implement, easy to implement at existing facilities for the preparation of hydrogen sulfide-containing oil, and allows oil to be produced in accordance with GOST R 51858-2002.

Depending on the specific conditions of the collection and preparation, the physicochemical properties of the oil and the concentration of hydrogen sulfide and low molecular weight mercaptans in it, the proposed installation can be operated both as part of the operating oil treatment unit after a deep oil dehydration unit, or as an independent device after the existing oil treatment unit in order to improve the quality of the product oil to the requirements of GOST R 51858-2002.

Claims (2)

1. Installation for the purification of oil from hydrogen sulfide and low molecular weight mercaptans, including a supplying oil pipeline of sulphurous oil, oil separator connected to a gas pipeline in series, an oil pump, a mixing device, an oxidation reactor, a high pressure separator with a gas pipeline, a low pressure separator with a gas pipeline and refined oil storage tanks , the capacity for the preparation and storage of the catalyst alkaline solution with metering pumps, the output of which is communicated with the inlet of the oil pump, is air a compressor, the output of which is connected to the inlet of the mixing device, and a flare line, characterized in that it is additionally equipped with a fresh flush water conduit connected to the pipeline between the high and low pressure separators, the gas separator and the low pressure separator gas pipelines connected, and the gas pipeline the high-pressure separator is connected with the flare line and through the pipe jumper - with the valve "after itself" - with the storage tanks of refined oil. 2. Installation according to claim 1, characterized in that an electric dehydrator is placed on the pipeline between the connection to the water conduit and the low pressure separator.

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