RU2424035C1 - Carbon sulphide-containing oil treatment plant - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to oil treatment plants and may be used in oil extracting industry. Proposed plant comprises separation units, preliminary and deep oil dehydration unit, oil desalination unit, unit of chemical neutralisation of carbon sulphide and light mercaptans with pressure pipeline to transfer proportioned reagent from reception and storage unit into oil pipeline, unit for commercial oil collection and storage, edge water collection and storage unit communicated via pipeline with preliminary oil dewatering unit. Unit of chemical neutralisation of carbon sulphide incorporates additionally flow metres and settler with pressure pipeline outlet arranged there between in oil pipeline. Flow metre is functionally connected with unit of chemical neutralisation of carbon sulphide to stabilise flow rates of reagent and oil, while additional settler is communicated via drain pipeline with preliminary oil dehydration unit. ^ EFFECT: higher efficiency of oil treatment at minimum costs. ^ 3 cl, 3 dwg

Description

The invention relates to oil treatment plants and can be used in the oil industry in the preparation of hydrogen sulfide-containing oil with a high content of hydrogen sulfide.

A known installation for the preparation of sour crude oil (RZ Sakhabutdinov and others. Features of the formation and destruction of oil-water emulsions at a late stage of oil field development. M.: VNIIOENG OJSC, 2005, p.226), including a separation unit, a preliminary oil dehydration unit as a part of heat exchangers, settling tanks and raw materials pumps, a unit for deep oil dehydration as a part of heating furnaces and settling tanks, an oil desalination unit as part of settling tanks with a fresh wash water pipeline, a collection and storage unit salable oil as a part of pumps and reservoirs, a unit for collecting drainage water and intermediate layers as a part of reservoirs with treatment facilities, an intermediate layer processing unit and a sludge processing unit.

The well-known installation allows you to ensure the quality of oil preparation by the concentration of chloride salts, mechanical impurities and water according to GOST R 51858-2002 and additionally carry out the processing of intermediate layers and the processing of oil sludge. The disadvantage of this installation is that in the preparation of hydrogen sulfide-containing oil, which has been separated at ordinary and elevated temperatures, effective removal of hydrogen sulfide from oil is not achieved and its content in the produced oil does not meet the requirements of GOST R 51858-2002, according to which the mass fraction of hydrogen sulfide in marketable oil should not exceed 20-100 million ^-1 (ppm) depending on the type of oil.

A known installation for the preparation of hydrogen sulfide-containing oil, designed to implement a method for the preparation of hydrogen sulfide-containing oil (US Pat. RF No. 2283856, C10G 19/02, 29/06, publ. 09/20/2006, Bull. No. 26), including a supply pipeline, oil separation unit in the composition separators and gas desulphurization units, an oil dehydration unit as part of a preliminary and deep oil dehydration stage, an oil desalination unit, a physical unit for the physical purification of oil from hydrogen sulfide as part of a desorption column with inlet and outlet gas pipelines and not teprovodami, a flow meter, installed in the inlet manifold to the column, block chemical neutralization of hydrogen sulfide and mercaptans as part of the container receiving and storing the reagent metering pump to the discharge conduit, the mixing device and the buffer tank, the block collection and storage tank oil.

This installation allows you to reduce the mass fraction of hydrogen sulfide and methyl and ethyl mercaptans to 20-100 million ^-1 and below 40-100 million ^-1, respectively, i.e. to standards that meet the requirements of GOST R 51858-2002, by combining the physical effects of oil by blowing off hydrogen sulfide with gas in a desorption column and chemical neutralization of hydrogen sulfide and mercaptans when a reagent-neutralizer is introduced into the oil.

The disadvantage of the installation is its limited scope. For its effective use, it is necessary to have sources of stripping gas not containing hydrogen sulfide, and a gas collection system with sufficient throughput. Sulfur-containing oil treatment facilities often do not have gas collection systems and blowing in a desorption column leads to significant losses of hydrocarbon feed when gas is supplied after the column to the flare. In these conditions, in addition to cleaning the volume of gas supplied to the column, it is required to invest certain costs for the disposal of a significant amount of gas after the column contaminated with hydrogen sulfide. Another major drawback of the installation is a decrease in the yield of salable oil due to the conversion of propane-butane and gasoline fractions of oil to the composition of the stripping gas after the column, which in the total gas volume is also flared. To reduce hydrocarbon losses, the column at best can only perform the function of a conventional vertical separator, in which the efficiency of oil purification from hydrogen sulfide is extremely low and amounts to no more than 30-35%. Therefore, the main process of purification of oil from hydrogen sulfide and light mercaptans is carried out through the use of a chemical neutralization block of hydrogen sulfide, which is mainly used for the well-known unit for cleaning commercial (dehydrated and desalted) oil from hydrogen sulfide (RU 45292 U1, B01D 19/00, publ. 10.05. 2005, Bull. No. 13), including the supply pipeline of commercial oil, a buffer tank, a mixing device installed in the pipeline of commercial oil in front of the buffer tank, a block of neutralization of hydrogen sulfide containing Food storage node and reagent metering pump, whose pressure line is provided with a pressure pulsation damper and connected to a nozzle installed in the tank oil line before the mixing device.

The disadvantage of the installation, taking into account the limitations of its effective use, is that it requires dosing of increased volumes of hydrogen sulfide neutralizing reagent into the oil stream, which leads to the contamination of already refined (dehydrated and desalted) crude oil with products of the reaction of hydrogen sulfide with reagent components, which is expressed in an increase the content of the aqueous phase and the negative impact on the results of analyzes to determine the concentration of chloride salts in accordance with GOST 51858-2002, which manifests itself in the form of an increase in their content I'm in oil.

Closest to the proposed installation is the preparation of hydrogen sulfide-containing oil (RZ Sakhabutdinov and others. The study of the effectiveness of neutralizing hydrogen sulfide in oil by chemical reagents. Oil industry. 2009. No. 7, p. 66-69), including the supply pipeline, separation units, preliminary and deep dehydration, desalting of oil, a block of chemical neutralization of hydrogen sulfide and mercaptans with a pressure pipe of a dosed reagent, mainly consisting of a unit for receiving and storing reagent with a metering pump ohm and pressure pipeline, units for the collection and storage of commercial oil and produced water.

The well-known installation allows you to ensure the quality of oil preparation by the concentration of chloride salts, solids, mass fraction of water, hydrogen sulfide and mercaptans according to GOST R 51858-2002 due to the sequence of technological operations to neutralize hydrogen sulfide, flushing, desalting and sludge oil when the reagent is supplied to the product or watered oil.

Fitting disadvantage when applying the reagent-catalyst in commercial oil with a mass fraction of hydrogen sulphide 150-200 mn ^-1 is the need for its additional training - the implementation of additional operations for oil dehydration and desalting with prolonged settling to remove hydrogen sulfide therefrom products of the reaction with the reagent and imparted with him water, since the reagents used to neutralize hydrogen sulfide are aqueous solutions that increase the total content of the aqueous phase in the oil volume, and e reaction products adversely affect the results of analysis of the concentration of chloride salts. Therefore, to ensure the necessary quality of oil, the use of additional settling equipment and additional volumes of fresh rinsing water is required, which leads to excessive energy costs. In addition, under these conditions, the necessary time is not provided for neutralizing hydrogen sulfide after feeding the reagent, which for the most effective reagents based on aminoformaldehyde mixtures with their optimal dosage rates in oil is 3-4 hours, and in this installation this time is limited by the points of supply of the reagent and fresh wash water in one pipeline during an additional oil desalination operation, which creates conditions for the rapid washing out of a part of the reaction that has not yet reacted with hydrogen sulfide coagulant and leads to a need to increase the dosage above its optimum value.

The supply of the neutralizing agent to partially dehydrated oil with a water cut of 3-5% (emulsion) after the preliminary dehydration stage requires a significant consumption, since in this case the neutralizing agent is also consumed to neutralize hydrogen sulfide in produced water. Considering that neutralizing agents are aqueous solutions, dosing them in waterlogged oil leads to a decrease in their reactivity due to their partial dilution with formation water. As a result, a reagent with an increased flow rate is fed into the emulsion, providing a certain margin that allows it to maintain its reactivity, which leads to even greater pollution of the oil with reaction products and requires increased fresh water consumption to wash oil from them. Under these conditions, the total liquid load on the installation elements (oil heaters, sedimentation tanks, etc.) increases significantly, which can lead to a violation of the technological regimes of its operation and a deterioration in the quality of marketable oil in all its indicators, especially in conditions of fluctuation of emulsion and oil consumption and , if necessary, bringing its indicators for the mass fraction of hydrogen sulfide to a level below 20 million ^-1 (ppm). At the same time, the stability of the obtained indicators of oil quality is not ensured at the initial optimal parameters of the oil refining process, determined by the consumption of oil (emulsion) and neutralizing agent. This is because the flow rate of oil produced at the plants is not constant and varies widely due to the frequency of oil pumping from booster pump stations (BPS) and the uneven flow of fluid from them. In this regard, to obtain a stable quality of oil by the value of the mass fraction of hydrogen sulfide and mercaptans, some excess amount of expensive reagent is fed into the oil (emulsion) based on the maximum volume (or close to it) of the incoming liquid. As a result, the concentrations of hydrogen sulfide and mercaptans required even in accordance with GOST R 51858-2002 can be obtained, but the amount of the aqueous phase or chloride salts is unacceptably increased by a specific volume of salable oil, and this requires additional costs for the preparation of the oil.

The technical objectives of the invention are to increase the efficiency of oil preparation at minimal material cost by combining operations to clean it from sulfur compounds (hydrogen sulfide and light mercaptans) and desalination in a single technological cycle, stabilizing oil quality by optimizing the process and the dosing point of the reagent, eliminating the possibility the negative effect of the reaction products of reactants with hydrogen sulfide and light mercaptans in determining the concentration of chloride salts in oil.

The stated technical problem is solved by the described plant for the preparation of hydrogen sulfide-containing oil, including separation units, preliminary and deep dewatering, oil desalination, chemical neutralization of hydrogen sulfide and light mercaptans with a pressure piping of a dosed reagent from the receiving and storage unit to the oil pipeline, and the collection and storage of marketable oil, unit collection and storage of produced water, connected by a water conduit to the oil preliminary dehydration unit.

New is that to increase the efficiency of oil preparation by combining operations to clean it from hydrogen sulfide and light mercaptans and desalting in a single technological cycle, to ensure the stability of the results obtained by the mass fraction of hydrogen sulfide, light mercaptans, water and the concentration of chloride salts, the unit for chemical neutralization of hydrogen sulfide and light mercaptans is additionally equipped with a flow meter and additional installed in series on the pipeline between the blocks of dehydration and desalination of oil itelnym sump, between which is placed in the pipeline outlet flow conduit, the flowmeter is operatively associated with the block of chemical neutralization to ensure a constant ratio of reagent costs, and oil, and an additional settling tank is connected with the drain conduit preliminary oil dehydration unit.

Also new is that in order to increase the efficiency of oil purification from hydrogen sulfide due to improved dispersion and uniform distribution of the reagent in the oil volume, the pressure pipe at the junction with the oil pipe is equipped with a nozzle installed in the oil pipe perpendicular to the direction of flow and made in the form of a tube with holes located along the central axis of the flow towards the direction of its movement and providing a pressure drop across the nozzle of at least 0.1 MPa.

Also new is that to improve the functionality of the installation and expand the range of its effective use, the oil pipeline after the flow meter is equipped with a flow swirl and a bypass line with a pump installed on it, and the outlet of the pressure pipe is connected to the pump inlet.

Figure 1 presents a schematic diagram of the proposed installation for the preparation of hydrogen sulfide-containing oil.

Figure 2 and figure 3 presents the options for connecting the pressure pipe dosing of the reagent to the pipeline, providing effective dispersion and distribution of the reagent in the volume of oil.

The installation (Fig. 1) comprises an oil supply pipe 1, a separation unit I, consisting, for example, of a separator 2 with a gas pipeline 3, a block II of preliminary oil dehydration, containing, for example, sump tanks 4 and raw materials pumps 5, a block of deep oil dehydration III containing, for example, crude oil heaters 6 and 7, sedimentation tanks 8 and ballast water pipe 9, a block for neutralizing hydrogen sulfide and light mercaptans IV, comprising a flow meter 10 mounted on the oil pipe 11, a reagent receiving and storage unit 12 with a metering pump 13, is provided frequency regulator 14, functionally connected to the flow meter 10, and the pressure pipe 15, which through the nozzle 16 (figure 2) is connected to the oil pipe 11 (figure 1) or to the reception of the pump 17 (figure 3) installed on the bypass line 18 covering swirl 19 located on the oil pipe 11 (Fig. 1), mixer 20, additional settlers 21 with a drain pipe 22 connected to the intake of raw materials pumps 5 or settling tanks 4 of the oil pre-dehydration unit II, oil desalination unit V, including e.g. sedimentation tanks electrodehydrators 23 and a fresh wash water pipeline 24, a commercial oil collection and storage unit VI, comprising, for example, a commercial oil pipeline 25, a buffer tank 26 with a gas pipeline 27, and commercial oil tanks 28, a production and collection water storage unit VII, including, for example water tanks 29 with a water conduit 30.

The blocks of separation I, preliminary dehydration of oil II, deep dehydration of oil III, desalination of oil V, collection and storage of commercial oil VI, collection and storage of produced water VII may contain other typical elements that make them in different interconnections with each other.

Installation for the preparation of hydrogen sulfide-containing oil works as follows. Crude hydrogen sulfide-containing oil is fed through a supply pipeline 1 to the separators 2 of the separation unit I, from where gas is supplied through the gas pipeline 3 to the gas collection system or to the flare. Partially degassed watered oil after separator 2 is fed into the tank 4 of the oil pre-dehydration unit II, from where it is sent with heat pumps 5 through heaters 6 and 7 of the deep dehydration unit III to a settling tank 8 with a temperature of 40-60 ° С, from which the settled ballast water is discharged through a pipeline 9 to sump tanks 4. Dehydrated oil with a mass fraction of water of not more than 1.0% is fed through a flow meter 10 of the unit for chemical neutralization of hydrogen sulfide and light mercaptans IV to the oil pipeline 11, into which from the receiving unit 12 Storage reagent metering pump 13 a predetermined metered amount of reagent depending on the flow meter 10 which detects the amount of incoming oil. The oil flow meter 10 is functionally connected with a frequency controller 14, which allows you to change the flow of the metering pump 13, due to which, with an increase or decrease in the flow rate of dehydrated oil, the volume of the reagent supplied to it changes, which allows you to maintain a predetermined ratio of oil-reagent costs and exclude the possibility overdose of the reagent, and therefore, reduce the negative impact of its use on oil quality.

The reagent in the oil pipe 11 is fed through the pressure pipe 15 through the nozzle 16 (figure 2), which is installed in the oil pipe perpendicular to the direction of flow and is made in the form of a tube with a hole located on the Central axis of the stream towards its direction of movement. Depending on the initial mass fraction of hydrogen sulfide in oil and reagent consumption, the number of holes in the nozzle can be any - from one to several. An important condition for the effective process of neutralization of hydrogen sulfide in oil is the intensive dispersion and uniform distribution of the reagent in the volume of oil. Therefore, the holes in the tube must be of such a diameter that, when the reagent is supplied, a pressure drop across the nozzle of at least 0.1 MPa is ensured. Field tests show that at a pressure drop with a lower value, the reagent is introduced into the stream without the necessary crushing of the reagent stream into droplets, which does not provide an effective distribution of the reagent in the oil volume. At the same time, the holes in the nozzle must have a diameter that prevents them from clogging with tiny particles of mechanical impurities that may be in the reagent. As field studies show, in most cases, one hole with a diameter of 0.8-1.5 mm is enough with the initial mass fraction of hydrogen sulfide in oil in the range of 250-650 ppm ^-1 , which is located in the center and directed towards the oil flow, which allows dosing of the reagent in the area of oil flow, where its speed is greatest to ensure uniform redistribution of the reagent in the volume of oil.

In case of failure to fulfill these conditions, for example, a small value of the mass fraction of hydrogen sulphide in oil at 150 million ^-1 and low oil consumption, reagent supplied to the pump intake 17 (Figure 3) low productivity, which is located in the bypass line 18, covering swirler 19, located on the oil pipeline 11 (figure 1) and providing intensive mixing of the liquid with the formation of a swirling flow. In the pump 17 (Fig. 3), due to the supply of the reagent, only part of the oil stream is intensively dispersed and uniformly distributed in the oil volume to obtain a concentrated emulsion of the reagent in oil, which is fed via bypass line 18 to mix with the swirling main oil stream immediately after swirler 19, where re-mixing of the reagent in an emulsion with crude oil is carried out. Since the pre-reagent-neutralizer was already uniformly mixed with part of the oil flow in the pump 17, the introduction of the reagent in a concentrated emulsion, the amount of which exceeds the amount of the reagent, allows the emulsion to be evenly distributed, and therefore the reagent, in the bulk of the main oil stream when they are mixed. As a swirler 19, it is possible to use a device of any design that provides a swirl or swirl flow.

Additional mixing of the droplets of the reagent with oil is carried out during the passage of the stream through the mixer 20 (figure 1). When transporting the reagent with oil through pipeline 11, hydrogen sulfide is neutralized with the formation of non-toxic sulfur reaction products, which, when analyzing the concentration of chloride salts according to GOST 51858-2002 (method A-titration of an aqueous extract), manifest themselves as imaginary chloride salts, since the reagents used for purification of oils from hydrogen sulfide, initially do not contain any salts. Given that the reagents are aqueous solutions obtained using fresh water, mixing the reagent with dehydrated oil containing saline formation water (up to 1.0%) allows simultaneous neutralization of hydrogen sulfide to carry out its washing from the true salts in the formation water at mixing it with fresh water of a reagent solution. Oil purified from hydrogen sulfide with an increased volume of the aqueous phase and a concentration of chloride salts (due to imaginary salts) enters additional settling tanks 21, where the completion of neutralization reactions of hydrogen sulfide is carried out. At the same time, oil settling occurs in these sedimentation tanks with the discharge of ballast water mixture with reaction products and part of the unreacted reagent through the drain pipe 22 to the intake of raw materials pumps 5 of the oil pre-dehydration unit II, which allows mixing this part of the reagent with the emulsion and partially reducing the mass fraction in it hydrogen sulfide in front of the unit for deep oil preparation III. With significant volumes of ballast water, to eliminate excessive load on the pumps and subsequent equipment, the water is discharged to the reception of settling tanks 4. Partially demineralized oil after settling tanks 21, in which processes of neutralization of hydrogen sulfide and preliminary desalination of oil are completed, enters the sedimentation tanks-electric dehydrators 23 unit for deep oil desalination V. For washing oil from residual salts (both true and imaginary) in front of sedimentation tanks-electric dehydrators 23 through a pipeline 24, the required amount of fresh water is injected, as a result of which chloride salts are washed out of the oil, and after sedimentation and discharge of water through pipeline 9, oil (dehydrated and desalted) passes through pipeline 25 of the commercial oil collection and storage unit VI to buffer tank 26, from where the residual gas enters the gas pipeline 27, and the oil is directed to the commodity tanks 28. The produced water from the settling tank 4 of the oil pre-dehydration unit II enters through the water conduit 30 into the water tanks 29 of the reservoir th of water VII and further - for purification.

The proposed installation allows the preparation of oil to the requirements of GOST R 51858-2002 and in comparison with the known has the following advantages:

- improves the efficiency of oil preparation by combining operations to clean it from hydrogen sulfide and light mercaptans and desalination in a single technological cycle;

- increases the efficiency of oil purification from hydrogen sulfide due to the intensification of the dispersion of the reagent and improve its distribution in the oil stream;

- improves the quality of salable oil by stabilizing the supply of reagent;

- reduced material costs for the preparation of oil by eliminating the need for its additional training.

The proposed installation for the preparation of hydrogen sulfide-containing oil is technologically advanced and simple to implement, eliminates the need for additional additional treatment of oil, is easily implemented at existing facilities for the preparation of hydrogen sulfide-containing oil, and makes it possible to obtain oil in accordance with GOST R 51858-2002.

Claims (3)

1. Installation for the preparation of hydrogen sulfide-containing oil, including oil separation units, preliminary and deep dehydration, oil desalination, chemical neutralization of hydrogen sulfide and light mercaptans with a pressure piping of a dosed reagent from the receiving and storage unit to the oil pipeline, collection and storage of marketable oil, and a collection and storage unit formation water connected by a water conduit to the oil pre-dewatering unit, characterized in that the chemical neutralization unit is additionally equipped installed sequentially on the oil pipeline between the dehydration and desalination units of the oil by the flow meter and an additional sump, between which the outlet of the pressure pipe is located in the oil pipe, the flow meter being functionally connected to the chemical neutralization unit to ensure a constant ratio of reagent and oil consumption, and the additional sump is connected by a drain pipe to the preliminary unit dehydration of oil. 2. Installation according to claim 1, characterized in that the pressure pipe at the junction with the oil pipeline is equipped with a nozzle installed in the oil pipeline perpendicular to the direction of flow and made in the form of a tube with holes located along the central axis of the flow towards its direction of movement and providing a pressure drop at the nozzle at least 0.1 MPa. 3. Installation according to claim 1, characterized in that the oil pipe after the flow meter is equipped with a flow swirl and a bypass line enclosing it with a pump installed on it, and the outlet of the pressure pipe is connected to the pump inlet.

Images