RU2470001C1 - Apparatus for drying and cleaning hydrocarbon fraction from methanol - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: apparatus has a line for feeding the starting mixture, a phase separator, a line for feeding water, a separation column having a stream inlet and outlet, a condensed vapour cooler and an output for the ready product. The apparatus is also characterised by that it is fitted with a mixer connected to the line for feeding water and the phase separator, having an outlet for the water-methanol mixture and an outlet for the separated hydrocarbon liquid phase. The line for feeding the starting mixture is connected to the mixer or the outlet for the separated hydrocarbon liquid phase from the phase separator which is connected to the separation column whose bottom part is fitted with an evaporator, wherein the column or the evaporator has an outlet for the ready hydrocarbon fraction, and the vapour outlet of the separation column is connected to an additional compressor whose outlet is connected in series to the evaporator, the cooler and the mixer.

EFFECT: use of the present apparatus enables to reduce specific power consumption of the drying and purification processes.

6 cl, 3 dwg

Description

The invention relates to techniques for purifying a hydrocarbon fraction, in particular a propane fraction, from methanol by azeotropic distillation and can be used in the oil, gas processing and petrochemical industries.

A known installation described in the method of purification of liquid hydrocarbons from an aqueous solution of methanol (see application No. 2007146631/04, 12.19.2007), which includes: a phase separator, in the form of a primary separator, which has an input line for the initial mixture of liquid hydrocarbons and an aqueous solution of methanol a methanol aqueous solution withdrawal line and a pre-purified liquid hydrocarbon withdrawal line connected to an extractor having a water input line, a methanol aqueous solution withdrawal line and a purified liquid hydrocarbon withdrawal line with a separator having a drain line of an aqueous methanol solution, a drain line of purified liquid hydrocarbons. The installation is equipped with a collector, to which there are connected lines for the output of an aqueous solution of methanol from the primary separator, extractor and separator.

Common features of the known and proposed installations are:

- input line of the initial mixture of liquid hydrocarbons,

- phase separator,

- water inlet line,

- drainage line of purified liquid hydrocarbons,

- the line of output of an aqueous solution of methanol.

The disadvantages of the known installation are:

- high energy consumption for the process of regeneration of the water-methanol mixture due to the large amount of water required to flush liquid hydrocarbons to the required residual methanol content in them, and also because of the need to conduct deep regeneration to a low residual methanol content in water;

- liquid hydrocarbons after the extractor and separator contain an equilibrium amount of water dissolved at positive temperatures, which requires additional drying before shipment to consumers (to prevent freezing of water at negative ambient temperatures). Drying measures significantly complicate the installation and significantly increase both capital costs and energy consumption.

The closest in technical essence and the achieved result is a well-known installation described in the method of separation of a wide fraction of low boiling hydrocarbons C ₁ -C ₆ (see RF patent No. 22254316, IPC ⁸ C07C 7/04), including a feed line fraction C ₁ -C ₆ , a sump of the C ₁ -C ₆ fraction with a methanol solution withdrawal line and a C ₁ -C ₆ fraction supply line; a column for isolating the C ₁ -C ₃ fraction; a propane fraction separation column with a condenser, a reflux condenser, a tank, a pump and purge lines, an ethane-propane fraction, an uncondensed product, reflux, a propane fraction; a washing column from methyl alcohol with a phase separator in the form of a settling tank, a filter separator, a water supply line, a water outlet, a washed propane fraction, a propane fraction washed and separated from water, separated water.

Common features of the known and proposed installations are:

- feed line of the initial mixture,

- phase separator,

- water supply line,

- separation column having input and output streams,

- condensed vapor refrigerator,

- yield of the finished hydrocarbon fraction.

The disadvantages of the known installation are:

- increased capital costs for organizing the separation process due to the need to install an additional column apparatus for washing the propane fraction with water;

- the propane fraction at the outlet of the installation contains an equilibrium amount of water dissolved at positive temperatures, which requires additional drying before shipment to consumers (to prevent freezing of water at negative ambient temperatures);

- increased water consumption due to the need to have a low concentration of methanol in water (4.5-7% wt.) at the outlet of the wash column and, as a result, increased energy costs for its regeneration;

- the need to use for washing propane water with a very low methanol content, which requires the use of deep regeneration of a water-methanol mixture, which also leads to increased energy costs.

The technical result is the organization of simultaneous drying and deep purification of the hydrocarbon fraction from methanol while reducing specific energy costs for the drying and purification processes.

This result is achieved by the fact that in the installation for drying and purifying the hydrocarbon fraction from methanol, including a feed line for the initial mixture, a phase separator, a water supply line, a separation column having inlet and outlet flows, a refrigerator, and an output of finished products, the installation is new equipped with a mixer connected to the water supply line and with a phase separator having an outlet of a water-methanol mixture and an output of a separated hydrocarbon liquid phase, while the feed line of the initial mixture is connected to the mixer or output m of the separated hydrocarbon liquid phase from the phase separator, which is connected to the separation column, the lower part of which is equipped with an evaporator, while the separation column or evaporator has an outlet for the finished hydrocarbon fraction, and the vapor output of the separation column is connected to an additional compressor, the output of the latter is connected in series with the evaporator , refrigerator and with mixer.

In addition, on the line connecting the refrigerator with the mixer, an additional filter - coalescer is installed.

In addition, a phase separator is connected to the separation column through a pump.

In addition, a degasser is additionally installed on the line connecting the evaporator to the refrigerator.

In addition, on the line connecting the evaporator to the degasser, an additional choke can be installed.

In addition, the phase separator is equipped with a vapor recovery line.

Providing the installation with a mixer for introducing water allows to organize the extraction of methanol from the flow of the hydrocarbon fraction sent to the separation column, and the removal of methanol from the phase separator due to its dissolution in water. When water is added, the equilibrium of the propane-methanol-water mixture changes, which leads to its separation and the transfer of part of the methanol from the rich hydrocarbon, for example propane, liquid phase to the liquid-rich phase.

The connection of the feed line of the initial mixture, for example, the propane fraction with methanol, with the mixer allows, in the case of a high concentration of methanol in the initial mixture, to reduce it before being fed to the separation column to the desired value due to the transition of part of methanol from the propane-rich liquid phase to the liquid-rich water phase.

The connection of the feed line of the initial mixture with the output of the separated hydrocarbon liquid phase from the phase separator allows, provided that the methanol concentration in the initial mixture corresponds to the acceptable values for the separation column, to direct the initial mixture directly to the separation column for cleaning, which makes it possible to reduce the overall dimensions of the phase separator and mixer.

The connection of the vapor output of the separation column with a compressor, the output of which is connected in series with the evaporator, allows you to increase the temperature of the vapors leaving the separation column, and thereby makes it possible to use the heat of condensation of these vapors to evaporate the mixture in the evaporator of the separation column. Using the heat of condensation of vapor from the top of the separation column to evaporate the propane fraction in the evaporator of the separation column can significantly reduce the energy consumption for evaporation of the product in the evaporator and its condensation in the vapor condenser of the separation column. Thus, the compressor operates in the heat pump mode. Since the temperature difference between the bottom and top of the separation column does not exceed several degrees, and the vapor flow through the column is a hydrocarbon fraction with a small amount of impurities, the energy transfer coefficient of the heat pump can reach very high values, i.e. energy consumption for separation can be reduced several times.

The installation of a coalescer filter on the line connecting the refrigerator to the mixer allows to enlarge the droplets of the liquid phase enriched in water in the stream after the refrigerator and thereby prepare the stream for separation in the phase separator. The liquid-rich liquid phase formed as a result of condensation and supercooling is a droplet of microscopic size, which can be separated in the phase separator only after their preliminary enlargement. Upon subsequent mixing of the streams in the mixer, droplet crushing to a microscopic size does not occur.

The connection of the phase separator with the column through the pump allows the installation to maintain operability at a pressure of the initial mixture lower than in the separation column. The pump increases the pressure of the hydrocarbon liquid phase to the pressure necessary for its supply to the separation column.

The installation on the line connecting the evaporator to the refrigerator, a choke and a degasser allows the removal of light impurities in the form of vapors from the hydrocarbon fraction. If light impurities are present in the initial mixture, they accumulate in the system and lead to disruption of the process, therefore, they are removed from the system in the degasser under reduced pressure, which is created by the throttle installed in front of the degasser.

The installation of a degasser on the line connecting the evaporator to the refrigerator allows the removal of light impurities in the form of vapors from the hydrocarbon fraction. If light impurities are present in the initial mixture, they accumulate in the system and lead to disruption of the technological process; therefore, they are removed from the system in the degasser. The removal of light impurities, to increase the driving force of the process, can be carried out under reduced pressure, which is created by a throttle installed in front of the degasser.

Providing a phase separator with a vapor removal line allows the removal of light impurities from the system in case of their low content in the initial mixture.

In figures 1, 2, 3 presents a diagram of the installation of drying and purification of the hydrocarbon fraction from methanol with its various implementation in accordance with the claims.

The installation for drying and purification of the hydrocarbon fraction from methanol contains a mixer 1, which can be connected to the supply line of the initial mixture 2 — the hydrocarbon fraction, for example, the propane fraction, mixed with methanol for drying and purification from methanol, the water supply line 3. The mixer 1 is connected to phase separator 4. Phase separator 4 has an outlet of a water-methanol mixture 5 and feeds it to a unit for regenerating a water-methanol solution (not shown), the output of light components 6, and also the output of the separated hydrocarbon liquid phase 7, which it is called a pipeline line with a separation column 8 (see figure 1). On the pipeline line connecting the outlet of the separated hydrocarbon liquid phase 7 and the separation column 8, a pump 9 can be installed for supplying liquefied gas to the separation column 8 (see figure 2). The vapor output from the separation column 8 is connected by a pipe to the inlet of the compressor 10, the output of which is connected by a pipe to the inlet of the heating medium of the evaporator 11, which is connected to the lower part of the separation column 8. The output of the heating medium from the evaporator 11 is connected to the inlet of the condensed vapor refrigerator 12 (see Fig. .one). In addition, on the line connecting the evaporator 11 with the refrigerator 12, an additional degasser 13 can be installed, having an outlet connected to the output line of the volatile components 14 (see Fig. 2, 3). In addition, on the line connecting the evaporator 11 to the degasser 13, an additional choke 15 can be additionally installed (see FIGS. 2, 3).

The output of the condensed vapor cooler 12 can be connected directly to the mixer 1 (see FIG. 1) or can be connected to the mixer 1 through an additionally installed filter coalescer 16 (see FIG. 2).

The separation column 8 (see Fig. 1) or the evaporator 11 (see Fig. 2) has an outlet for the finished hydrocarbon fraction 17 connected to the line of the dried and purified propane fraction.

The feed line of the initial mixture 2, namely the hydrocarbon fraction for purification, can be connected to the mixer 1 (see figure 1), or with the output of the separated hydrocarbon liquid phase 7 from the phase separator 4 (see figure 3).

The unit is equipped with auxiliary pumps, pipelines and the necessary shut-off and control valves.

Installation works as follows:

The initial mixture is a hydrocarbon fraction, for example a propane fraction, mixed with methanol for drying and purification from methanol enters through the supply line of the initial mixture 2 to the mixer 1 (see figure 1), into which water is supplied from the regeneration unit through the water supply line 3 water-methanol mixture, or from another source, as well as the return stream of the methanol-enriched condensed vapors of the top of the separation column 8. When mixed, part of the dissolved methanol passes from the hydrocarbon-rich liquid phase to the liquid-rich liquid. From the mixer 1, the water-methanol mixture is sent to the phase separator 4 for phase separation. The water-methanol mixture is withdrawn from the installation for subsequent regeneration through the outlet of the water-methanol mixture 5. The hydrocarbon phase, through the outlet of the separated hydrocarbon liquid phase 7, is sent directly to the separation column 8 (see Fig. 1). The hydrocarbon phase can be supplied to the separation column 8 using a pump 9 at a pressure of the initial mixture lower than in the separation column 8 (see FIG. 2). Pump 9 increases the pressure of the hydrocarbon liquid phase to the pressure necessary for its supply to the separation column 8. Vapors of light components are removed from the phase separator 4 through the output of light components 6. The hydrocarbon fraction for drying and purification of methanol through the feed line of the initial mixture 2 can be fed to a pipeline line connecting the outlet of the separated hydrocarbon liquid phase 7 and the separation column 8 (see figure 3). Separation column 8 implements a separation mode using non-ideal properties of the hydrocarbon-methanol-water system (the presence of azeotropy), as a result of which almost all methanol and water are concentrated in the hydrocarbon fraction leaving the vapor in the upper part of separation column 8, and the bottoms product discharged from separation column 8, contains only a small residual amount of methanol and water. The vapors leaving the top of the separation column 8 are compressed by the compressor 10 and are sent to condensation in the evaporator 11 of the separation column 8 with increased temperature and pressure. Due to the heat condensation of the vapors of the top of the separation column 8, part of the bottoms product is evaporated in it and the necessary product is created for it work vapor stream. After the evaporator 11, the condensed vapors of the top of the separation column 8 are sent to the refrigerator 12, where, as a result of lowering their temperature, the liquid phase enriched in water is condensed, which coarsens after passing through the filter flow - coalescer 16, and is sent for separation to the phase separator 4, from where it is output for regeneration through the yield of water-methanol mixture 5.

The separation of the light components can be carried out using a degasser 13 (see figure 2). In this case, the vapors are partially condensed in the evaporator 11, and not the condensed part, which contains predominantly volatile components, is separated in the degasser 13 and removed through the output line of the volatile components 14. To increase the driving force of the process, light components can be separated in the degasser 13 under reduced pressure, in in this case, the pressure in the degasser is reduced by means of a throttle 15. The liquid hydrocarbon phase from the degasser 13 is sent to the refrigerator 12.

From the bottom of the separation column 8 (see FIG. 1) or from the evaporator 11 (see FIG. 2), the finished product — the dried and purified methanol propane fraction — is output to the consumer through the outlet of the finished hydrocarbon fraction 17.

Claims (6)

1. Installation of drying and purification of the hydrocarbon fraction from methanol, including a feed line for the initial mixture, a phase separator, a water supply line, a separation column having inlet and outlet flows, a condensed vapor cooler, an output of finished products, characterized in that the installation is equipped with a mixer connected with a water supply line and with a phase separator having an outlet of a water-methanol mixture and an outlet of a separated hydrocarbon liquid phase, the feed line of the initial mixture being connected to a mixer or an outlet of a separated hydrocarbon liquid phase from the phase separator, which is connected to the separation column, the lower part of which is equipped with an evaporator, while the column or evaporator has an outlet of the finished hydrocarbon fraction, and the vapor output from the separation column is connected to an additional compressor, the outlet of the latter is connected in series with the evaporator, fridge and with mixer. 2. The installation of drying and purification of the hydrocarbon fraction from methanol according to claim 1, characterized in that an additional filter-coalescer is installed on the line connecting the refrigerator to the mixer. 3. Installation of drying and purification of the hydrocarbon fraction from methanol according to claim 1, characterized in that the phase separator is connected to the column through a pump. 4. Installation of drying and purification of the hydrocarbon fraction from methanol according to claim 1, characterized in that on the line connecting the evaporator to the refrigerator, an additional degasser is installed. 5. Installation of drying and purification of the hydrocarbon fraction from methanol according to claim 4, characterized in that a choke is installed in front of the degasser. 6. Installation of drying and purification of the hydrocarbon fraction from methanol according to claim 1, characterized in that the phase separator is equipped with an output of light components.

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