Adsorption method of purifying high-pressure natural gas

Abstract

The invention relates to the purification of natural gas by adsorption and can be used in industrial gas facilities. The claimed adsorption method of purifying high-pressure natural gas involving an adsorption apparatus consisting of N adsorber devices operating in alternation, a heat exchanger-heater, a condenser-cooler, a settling vessel, pipe valves (control and isolation valves) and a throttle, which are connected by a system of pipes, makes it possible to obtain a number of technical results: to provide more efficient use of an adsorbent by increasing from 66.6% to 100% the proportion of the total charge of adsorbent supplied to the apparatus which is actually utilized in purifying the natural gas during execution of procedure (f) in a working cycle of the apparatus; to eliminate the risk of accidents caused by isolation valve failure; and to reduce the risks of poor regeneration of the adsorbent or unsatisfactory cooling thereof by making it possible to vary the use of a reserve procedure (d). The technical result is an increase in the efficiency of adsorbent use and a decrease in the risk of accidents caused by the failure of shut-off valves.

Description

[0001] METHOD OF ADSORPTION PURIFICATION OF HIGH-PRESSURE NATURAL GAS

[0002] AREA OF TECHNOLOGY

[0003] The invention relates to the adsorption purification of high-pressure natural gas and can be used in gas industry enterprises, for example, in the preparation of natural gas for transportation through main pipelines or in the production of liquefied natural gas.

[0004] Natural gas purification can be accomplished using a number of methods, but deep drying and purification of natural gas in industry is primarily accomplished using the adsorption method. Typically, adsorption purification of natural gas is performed in adsorption purification units using a system of several fixed-bed adsorption units. The units are periodically switched between the stages of adsorption gas purification, adsorbent regeneration, and subsequent cooling of the hot regenerated adsorbent to the adsorption temperature. The pressure varies significantly at different stages of the process.

[0005] PRIOR ART

[0006] A pressure equalization system for air separation purification and a control method are known, which comprises: a first air line; a pressure-generating gas pipeline, which is connected to the first air line and is used to receive the pressure-generating gas and supply it to the first air line; and a control valve located on the pressure-generating gas pipeline and having an opening degree regulated by a flow regulator, by means of which the amount of gas entering the pressure-generating gas pipeline is regulated; dry nitrogen is used to equalize the pressure in the adsorber;during the entry into the adsorption stage from the regeneration stage, the pressurizing dry nitrogen used in the pressure equalization stage is pre-mixed with moist air from the main air compressor before entering the adsorber in such a way that the gas components flowing towards the cold air separation compartment remain substantially unchanged in order to reduce disturbances in the conditions of gas entering the distillation column to participate in the distillation due to the gradual change in the gas component from dry nitrogen to dry air, which thereby stabilizes the process conditions (patent RU 2754881 C1, IPC F25J 3 / 04, filed on 05.11.2020, published on 08.09.2021). The disadvantages of the invention are:;

[0007] • use of an additional nitrogen agent in the system, which requires additional equipment;

[0008] • the need to use dry nitrogen;

[0009] • dry nitrogen used at the pressure equalization stage is pre-mixed with moist air from the main air compressor before entering the adsorber, leading to a decrease in the moisture concentration in the mixed flow, which is then dried in the adsorber, which, according to Henry's law, reduces the activity of the adsorbent for moisture and indirectly leads to an increase in the adsorbent loading in the adsorber and the size of the apparatus.

[0010] A method is known for adsorption drying and purification of natural gas from sulfur-containing components after a booster compressor station before feeding the natural gas into a main gas pipeline, which includes a cyclically repeated stage of adsorption drying and purification of natural gas, a stage of regenerating the adsorbent with hot purified natural gas and a stage of cooling the adsorbent with a portion of the cold purified natural gas, characterized in that a portion of the purified natural gas after use in the adsorbent cooling stage is subjected to recuperative heat exchange, heating in a furnace and then used as regeneration gas in the adsorbent regeneration stage, after the adsorbent regeneration stage, the regeneration gas containing desorbed impurities is cooled in the first unit of adsorption drying and purification of natural gas and sent to a second additional unit of adsorption purification of regeneration gas,in the second additional unit for adsorption purification of regeneration gas, the stage of adsorption of impurities, the stage of regeneration of the adsorbent and the stage of cooling of the adsorbent are cyclically implemented, wherein at the stage of adsorption of impurities from the regeneration gas of the first unit of adsorption drying and purification of natural gas desorbed impurities are extracted, the purified regeneration gas is returned for recycling to the purified natural gas, and the stage of regeneration of the adsorbent is carried out with hot purified natural gas in two phases: during the first phase, the regeneration gas with the peak amount of desorbed impurities is discharged to the flare, during the second phase, the regeneration gas is sent for recycling to the purified natural gas - in both cases, the regeneration gas is pre-cooled and the condensate is separated (patent RU 2717052 C1, IPC BOID 53 / 26, filed on 30.12.2019,(published 17.03.2020). A disadvantage of the invention is the lack of a well-developed system for switching adsorbers from one stage to another (the stage of adsorption of impurities, regeneration of the adsorbent and cooling of the adsorbent) using valve devices, since the type of valve devices and the position of their placement on the corresponding pipelines are not specified, which can lead to a decrease in the depth of drying of natural gas due to the mixing of different flows during the process of switching adsorbers.

[0011] A known method for drying and purifying gas is based on pressure-cycle adsorption without heating, including adsorption of the components to be purified, regeneration of the adsorbent carried out by reducing the gas pressure in the adsorber, purging the adsorbent with purified and dried gas under low pressure and increasing the gas pressure in the adsorber to the operating value after regeneration, characterized in that the purge gas, when the pressure is reduced, is divided into hot and cold streams in a vortex tube, the adsorbent is purged with a hot stream, the pressure in the adsorber is reduced below the purge and the purification products are pumped out, the pressure is increased to the purge value, which is carried out with a cold stream at a temperature below the temperature of the gas to be purified (patent RU 2157722 C2, IPC BOID 53 / 26, F04B 39 / 16, declared on 30.10.1997, published on 20.10.2000). The disadvantages of the invention are:

[0012] • low actual productivity of the installations, ranging from several l / h to hundreds of l / h, which prevents the use of the short-cycle adsorption method on an industrial scale (100 or more tons / h) due to the high inertia of the operation of large-sized adsorbers when switching them from one stage of the process to another with a fixed response time of the shut-off valves;

[0013] • low efficiency of the adsorbent, since the optimal duration of the adsorption stage from the adsorption standpoint should theoretically be several seconds, and such a short period of operation of the apparatus cannot really be ensured by industrial technical means.

[0014] A process gas preparation unit is known, which includes an adsorption unit made up of several adsorbers, the top of which is connected to a feed gas supply line, a cooling gas supply line and a saturated regeneration gas outlet line, and the bottom is connected to a prepared gas outlet line, a cooling gas outlet line and a regeneration gas supply line, wherein the feed gas supply line passes through a control valve and is connected to an inlet separator, the gas outlet from the inlet separator is connected to a first recuperative heat exchanger, the gas outlet from which is connected to the top of the adsorbers, the prepared gas outlet line is connected to a first filtering device, wherein the cooling gas supply line is connected to the feed gas supply line upstream of the control valve and is connected to a filter separator, the gas outlet from which is connected to the top of the adsorbers, and the cooling gas outlet line is sequentially connected to a second filtering device,the second recuperative heat exchanger and the first furnace, the regeneration gas supply line is connected to the bottom of the adsorbers, and the saturated regeneration gas outlet line is connected in series with the third filter device, the second recuperative heat exchanger, the first recuperative heat exchanger, the propane refrigerator and the high-pressure separator (patent RU 2814922 C1, IPC BOID 53 / 00, B01D 53 / 14, filed 12.10.2023, published 06.03.2024).,

[0015] The disadvantages of the invention are:

[0016] • control valves change the flow rate of the dried gas, regeneration gas and cooling gas flows quite quickly in a small range of change in the flow rates of these flows, however, if it is necessary to switch the adsorbers from one stage of the process to another, associated with the cessation of the supply of one of the flows and the beginning of the supply of another flow into the apparatus, a significant time range is required, for example, for control valves with electric drives of the CV 206 / 216 / 306 / 316 GG type, the time for the complete movement of the rod, corresponding to the positions from “close” to “open”, lies within 75-150 s, depending on the stroke of the rod.This will result in a portion of the high-pressure flow being diverted into a low-pressure flow. For example, when switching from the adsorbent cooling stage with dry cooling gas in the adsorber to the adsorption drying stage of the initial wet natural gas, a significant amount of the initial wet natural gas will inevitably be diverted into the dry cooling gas stream, which has a lower pressure than the initial wet natural gas. While the control valve in the natural gas line should theoretically be open and the control valve in the cooling gas line closed, in reality, both control valves will be open for a time.

[0017] • it is possible that the original wet natural gas may be compressed into cooling gas and / or regeneration gas due to the possibility of leakage of a completely closed control valve with a large difference in products on both sides of the valve.

[0018] The adsorber switching system of the units is the weakest link in the deep purification and drying of process streams. The shutoff valves that ensure the cyclic operation of the adsorbers—control and shutoff valves with electric and pneumatic actuators—always have a certain response time due to the geometry of the valve designs, and this response time increases as the throughput increases due to the valve metrics. This situation is the primary reason why the throughput of efficient and economical pressure swing adsorption units ranges from just a few liters to 300 m3 / h, limiting their application to medical equipment, instrument making, transportation, and small-scale manufacturing.

[0019] For cyclic switching of adsorbers, shutoff valves, which operate in only two positions—open and closed—are the most suitable. However, even these valves have drawbacks, leading to significant risks of process control violations, reduced flow purification, and emergency shutdowns, all of which are determined by the valve design itself.

[0020] These disadvantages include:

[0021] • significant time for switching the valve from one position to another, which leads to mixing of different flows, for example, dry gas from cooling the adsorbent with low pressure is mixed with the gas flow being purified, which leads to a gradual increase in the concentration of pollutants in the cooling gas circuit, their sorption by the adsorbent at the cooling stage and, as a consequence, to a decrease in the depth of purification of the target flow at the adsorption stage; • with a large pressure drop of several MPa on the shut-off valve in the "closed" position, a constant small flow of high-pressure gas into the low-pressure zone is possible with a change in the composition of the low-pressure gas;

[0022] 5 • an insufficient level of precision in the execution of the “shutter-seat” pair of a specific valve used increases the risk of poor-quality switching of flows according to the cyclogram, for example, in shut-off valves according to TU 3472-1-057419211-2014 the pressure drop on the valve spool is limited, and during cyclic switching in a situation where in the system

[0023] 10 switching of flows, closed low-pressure sections are created with the installation of shut-off valves on their lines, regulating the switching of devices with different operating pressures; in the closed space, the pressure begins to gradually increase due to the squeezing of the high-pressure product through the shut-off valve, which can lead to the failure of the shut-off valve on the low-pressure line, creating an emergency situation in the adsorption unit as a whole due to the violation of the cyclogram.

[0024] DISCLOSURE OF THE INVENTION

[0025] The objective of the claimed invention is to develop a method

[0026] 20 adsorption purification of high-pressure natural gas, increasing the efficiency of adsorbent use and reducing the risk of emergency situations due to failure of shut-off valves.

[0027] The solution to the stated problem is ensured by the fact that the method of periodic adsorption purification of high-pressure natural gas from impurities of organosulfur substances and / or methanol and / or moisture, including three stages of the process: the stage of adsorption purification of high-pressure natural gas with a fixed bed of adsorbent, the stage of regeneration of the adsorbent with hot regeneration gas and the stage of cooling the adsorbent with cold cooling gas, implemented according to a cyclogram in a battery of N adsorbent devices filled with an adsorbent, consisting of N equal in time phases of the working cycle, wherein each of the phases characterizes the operation of the corresponding adsorber device, connected by inputs and outputs to the corresponding systems for moving and processing gas flows at three stages of the process with control and shut-off valves on each flow, whilethat the first two phases provide the function of implementing the stage of adsorption purification of high-pressure natural gas by a stationary bed of adsorbent in N-1 adsorber apparatuses, and the third phase ensures the restoration of the adsorption properties of the adsorbent by sequentially performing the following procedures in one adsorber apparatus with the estimated time of implementation of each procedure:,

[0028] (a) - a procedure for draining high-pressure natural gas from the free space of the adsorber apparatus with a reduction in pressure corresponding to the adsorption purification stage to a pressure corresponding to the adsorbent regeneration stage,

[0029] (b) - the procedure for purging the adsorber apparatus with a hot stream of low-pressure process gas, corresponding to the stage of adsorbent regeneration,

[0030] (c) - the procedure for purging the adsorber apparatus with a cold flow of low-pressure process gas, corresponding to the stage of cooling the adsorbent with cold cooling gas,

[0031] (g) - a procedure for reserving the regenerated adsorbent, which allows, depending on the state of the adsorbent, to switch the adsorber apparatus to procedure (b), (c) or (d),

[0032] (d) - the procedure of filling the free space of the adsorber apparatus with high-pressure natural gas until the pressure corresponding to the adsorption purification stage is reached,

[0033] (e) - a procedure for purging the adsorber apparatus with high-pressure natural gas corresponding to the adsorption purification stage, wherein the switching of the adsorber apparatus during the third phase from one procedure to another is ensured by control and shut-off valves installed on the lines of the inlet to the adsorber apparatus and the outlet from the adsorber apparatus of the high-pressure natural gas flow, the inlet of the hot or cold low-pressure process gas flow and the outlet of the spent low-pressure process gas flow; the flow of the purified initial high-pressure natural gas with impurities of moisture and organosulfur substances is divided into N - 1 parts during the first two phases of the cyclogram and fed in parallel from above into N - 1 adsorber apparatus or is divided into N parts during the execution of procedure (e) of the third phase and fed in parallel from above into N adsorber apparatuses, ensuring passage in each adsorber apparatus through a layer of adsorbent absorbing moisture,methanol and organosulfur substances, converted at the outlet of the adsorber apparatus into a stream of deeply purified natural gas, combined at the outlet of N-1 or N adsorber apparatuses into a common stream, which is then divided into two parts, forming a stream of deeply purified natural gas and a stream of process gas, which is then throttled to a pressure ensuring the implementation of procedures (b) and (c), while in order to implement the stage of regeneration of the adsorbent according to procedure (b), the stream of low-pressure process gas is heated in a heat exchanger apparatus by a stream of coolant, fed to the bottom of the adsorber apparatus, ensuring passage through the adsorbent layer, heating the stream of process gas and carrying away the desorbed substances, and fed through the top of the adsorber apparatus into the line of low-pressure exhaust process gas and, after cooling in a condenser-refrigerator, is subjected to separation in a separator into a humidified process gas,which is then sent through a booster compressor for mixing with the original high-pressure natural gas, or fed into the enterprise's fuel gas system and condensate consisting of desorbed substances, which, in the absence of methanol, is sent to treatment facilities, and in the presence of methanol, is sent for thermal or catalytic neutralization, and to carry out the adsorbent cooling stage according to procedure (c), the low-pressure process gas flow is fed to the bottom of the adsorber apparatus, ensuring passage through the adsorbent layer, cooling it, fed through the top of the adsorber apparatus into the low-pressure waste process gas line and then sent through a booster compressor for mixing with the original high-pressure natural gas or sent to the enterprise's fuel gas system, an excess pressure increase in a completely shut-off low-pressure process gas supply system when performing procedures (a), (d),(d) and (e) are compensated by bleeding gas through a bypass line from the completely shut-off low-pressure process gas supply system into the low-pressure process gas exhaust system.

[0034] An important feature of the proposed method for purifying high-pressure natural gas is that the primary process is performed in multiple (N-1) or N adsorber units, while all auxiliary operations are performed in a single adsorber unit. This significantly increases the efficiency of adsorbent utilization. For example, when purifying natural gas in a typical three-adsorber adsorption unit with a traditional three-phase cycle, one adsorber unit operates in the adsorption stage during one phase of the cycle, a second unit operates in the adsorbent regeneration stage, and a third unit operates in the adsorbent cooling stage. In other words, the adsorption stage accounts for 1 / 3 of the total adsorbent load in the adsorption unit.In the proposed purification method with a three-adsorber system, two units will always operate simultaneously during the adsorption stage during the cycle. When the third adsorber unit (e) is used, all three units operate simultaneously. Thus, two-thirds of the total adsorbent load in the adsorption unit operates during the adsorption stage, while the entire adsorbent load operates during procedure (e). Furthermore, when the purified natural gas stream passes through a system of sequentially operating adsorbers, the depth of natural gas purification increases dramatically, as the contact time of the purified gas with the adsorbent at least doubles.When the purified natural gas flow passes through a system of parallel operating adsorber devices, the sorption activity of the adsorbent increases significantly, since when natural gas is supplied in parallel to two adsorber devices, with a twofold decrease in the linear velocity of the natural gas in the adsorbent layer, the length of the mass transfer zone decreases by 1.414 times, which indirectly leads to an increase in the dynamic activity of the adsorbent, which makes it possible to increase the productivity of the adsorption unit for natural gas by 5-8% without changing the depth of purification of the natural gas.

[0035] It is also possible to simultaneously moderately increase the plant's productivity for natural gas and the depth of purification within the calculated limits of the variability of the process mode.

[0036] The introduction of procedure (d) into the third phase of the process for reserving the regenerated adsorbent, which allows, depending on the state of the adsorbent, to switch the adsorbent apparatus to procedure (b), (c) or (e), also increases the flexibility of the process, since if the quality of the adsorbent regeneration in procedure (b) worsens, the continuation of its time period of the phase by switching to procedure (d) allows to increase the duration of the regeneration stage and improve its quality; if the adsorbent is not sufficiently cooled in procedure (c), the continuation of its time period of the phase by switching to procedure (d) allows to increase the duration of the adsorbent cooling stage, and if the quality of regeneration and the level of adsorbent cooling are within the standard, the transition of the time of procedure (d) to procedure (e) increases the depth of purification of natural gas in this adsorber apparatus.Thus, the claimed method ensures flexibility in the operation of the adsorption unit, allowing for varying the unit's capacity for purified natural gas and the depth of its purification.

[0037] An additional advantage of the method is the implementation of the stages of adsorbent regeneration and adsorbent cooling with a single flow of multi-temperature process gas, which reduces the number of pipelines and simplifies the piping of adsorber devices.

[0038] Bleeding gas through a bypass line from a completely isolated low-pressure process gas supply system to a low-pressure process gas exhaust system significantly reduces the risk of pressure increase in a completely isolated process gas supply system when performing procedures (a), (d), (e).

[0039] It is advisable to use silica gels as an adsorbent as a cheap adsorbent for relatively shallow drying of natural gas when preparing it for transportation in main pipelines.

[0040] It is advisable to use synthetic zeolites as an adsorbent for deep drying of natural gas when preparing natural gas for processing into liquefied natural gas.

[0041] It is advisable to use KA zeolites as an adsorbent as the most active and selective adsorbent for deep drying of natural gas.

[0042] It is useful to use two adsorbent layers with different adsorption characteristics in an adsorber apparatus when natural gas purification requires the removal of impurities of different natures and with different affinities for the adsorbent. Specifically, when drying natural gas and purifying it from methanol, it is beneficial to use KA zeolites in the upper adsorbent layer, which provide deep drying of the natural gas, and NaA zeolites in the lower adsorbent layer, which absorb both moisture and methanol. During adsorbent regeneration in procedure (b), it is useful to gradually increase the adsorbent layer temperature to the adsorbent regeneration temperature and then bring it to a plateau. This prevents local overheating early in the process, which can lead to cracking and crushing of the adsorbent granules, leading to dust formation, which adversely affects the operation of downstream equipment and shutoff valves.Maintaining a plateau of constant regulated regeneration temperature ensures high-quality regeneration of the adsorbent.

[0043] When regenerating an adsorbent that removes various impurities during purification, it is recommended to gradually increase the adsorbent bed temperature during procedure (b) to an intermediate temperature that ensures a bed temperature at which weakly adsorbed substances are desorbed from the lower adsorbent layer. Maintain this intermediate temperature for the duration of their desorption. Then, gradually increase the adsorbent bed temperature to the temperature of the adsorbent regeneration stage for strongly adsorbed substances, and then bring it to a plateau. Two-stage regeneration allows for the initial removal of weakly adsorbed methane and heavier hydrocarbons from the regenerated adsorbent bed at a low temperature, which inevitably also adsorbs relatively small quantities from the purified gas stream. This helps reduce adsorbent coking, which causes its deactivation and reduces adsorbent activity. This is followed by desorption of water and other impurities at a high temperature.

[0044] It is useful to regulate the adsorbent bed temperature by regulating the flow rate of hot, low-pressure process gas. In this case, a hot oil stream or organic fuel combustion products can be used as a heat transfer fluid to heat the process gas to the specified temperature. The adsorption unit becomes an independent process unit if a portion of the high-pressure natural gas feed stream or a portion of the low-pressure waste process gas stream is used as the organic fuel.

[0045] It is useful to bleed gas through the bypass line from the completely

[0046] 5 The shut-off system for supplying low-pressure process gas to the exhaust low-pressure process gas removal system shall be provided with control valves installed on the bypass line, which allows for minimizing losses of process gas during routine operation of the shut-off valves.

[0047] 10 It is possible to significantly expand the scope of application of the claimed method of adsorption purification, since it is acceptable to use high-pressure methane-containing gas as a stream of purified high-pressure natural gas; it is also possible, for example, to dry synthesis gas and other similar high-pressure streams.

[0048] The method for periodic adsorption purification of high-pressure natural gas from impurities of organosulfur substances and / or methanol and / or moisture is illustrated by the basic diagram of the adsorption unit shown in Figure 1, the operation cyclogram of the unit shown in Figure 2, and the adsorbent processing diagram

[0049] 20 different phases of adsorption purification of natural gas.

[0050] LIST OF DRAWINGS

[0051] Figure 1 shows a schematic diagram of one of the possible implementation options for the method of periodic adsorption purification of high-pressure natural gas from impurities of organosulfur substances and / or methanol and / or moisture using the following designations:

[0052] 100, 101, 102 - adsorbers;

[0053] 103 - sump;

[0054] 200, 201, 203, 204, 206, 207, 209, 212, 215, 218 - control valves; 202, 205, 208, 210, 211, 213, 214, 216, 217 - shut-off valves; 219 - throttle;

[0055] 300 - heat exchanger-heater;

[0056] 301 - condenser-refrigerator;

[0057] 1-29 - pipelines.

[0058] Figure 2 shows a cyclogram of the operation of a plant for one of the possible implementation options for the method of adsorption purification of high-pressure natural gas.

[0059] BRIEF DESCRIPTION OF DRAWINGS

[0060] The adsorption unit consists of three adsorber apparatuses 100, 101 and 102, operating alternately in accordance with a cyclogram (Fig. 2) consisting of three equal in time t phases of the working cycle, a heat exchanger-heater 300, a condenser-cooler 301, a settling tank 103, pipeline fittings consisting of control fittings 200, 201, 203, 204, 206, 207, 209, 212, 215, 218 and shut-off fittings 202, 205, 208, 210, 211, 213, 214, 216, 217, and a throttle 219, connected by a system of pipelines 1-29. The complete operating cycle of the unit in time is 3t.

[0061] According to the cyclogram, adsorber 100, simultaneously with adsorber 101, performs adsorption purification of high-pressure natural gas, while adsorber 102 performs procedures (a), (b), (c), (d), (e), and (e) associated with adsorbent regeneration. Following adsorbent regeneration, each adsorber purifies gas during two phases of the operating cycle over a period of 2τ. However, the operation of adsorbers 100 and 101 differs significantly in terms of the physicochemical specifics of sorption at different phases of gas purification.

[0062] Figure 3 shows a diagram of the adsorbent processing at different phases of the adsorption purification of natural gas. The processing of the adsorbent layer in the adsorber over time at the beginning (F1a), middle (F1b) and end (F1 s) of the first phase, as well as at the beginning (F2a), middle (F2b) and end (F2 s) of the second phase of the adsorption stage. Thus, in adsorber 100, operating in the second phase of the process, sorption occurs in the lower part of the adsorbent layer with complete processing of the upper part of the layer, and in adsorber 101, operating in the first phase of the process, sorption occurs in the upper part of the adsorbent layer with complete processing of the upper part of the layer, and in the second - in the lower part.

[0063] The operating features of an adsorption unit can be examined using the example of the operation of one of the adsorbers, for example, adsorber 100, shown in Figure 1.

[0064] At the beginning of the adsorption unit operating cycle, the adsorber 100 continues to purify natural gas during the second phase, continuing to operate continuously after the completion of the first phase. In this case, the purified high-pressure natural gas supplied to the adsorption unit via pipeline line 1 is fed to the top of adsorber 100 via pipeline line 2 through control valve 200 (via pipeline lines 3 and 4 through control valves 203 and 206 to the top of adsorbers 101 and 102, respectively), passes from top to bottom through the adsorbent layer that extracts impurities from the gas with the lower part of the layer, is purified and discharged from the bottom of adsorber 100 via pipeline line 5 (7 and 9, respectively, from the bottom of adsorbers 101 and 102) through open shut-off valve 210 (213 and 216 during operation of adsorbers 101 and 102, respectively) into the high-pressure purified natural gas pipeline line 11, common to all adsorbers of the unit.When the adsorber 100 is operating at the adsorption stage (the first and second phases), the shut-off valve 211 is closed in the lower part of the adsorber, preventing the loss of purified natural gas into the adsorbent regeneration system, the control valve 209 (212 and 215 during the operation of adsorbers 101 and 102, respectively), and in the upper part of the adsorber, the shut-off valve 202 (205 and 208 during the operation of adsorbers 101 and 102, respectively) and the control valve 201 (204 and 207 during the operation of adsorber 102 and 102, respectively) are closed, preventing the loss of purified high-pressure natural gas into the adsorbent regeneration system. A portion of the purified high-pressure natural gas, considered as process gas, is removed from pipeline line I via pipeline line 12, throttled in throttle 219 to a low pressure required for carrying out the regeneration stages, and enters pipeline line 13, which is the process gas line after throttling.

[0065] Upon completion of the second phase of the adsorption stage, the adsorber 100 is switched to procedure (a) of the adsorbent regeneration phase - drainage of high-pressure natural gas from the free space of the adsorber apparatus with a decrease in the pressure corresponding to the adsorption purification stage to a pressure corresponding to the adsorbent regeneration stage. For this purpose, all pipeline valves are closed in the lower part of the adsorber 100 - shut-off valves 210 (213 and 216 when switching adsorbers 101 and 102, respectively) are closed, and shut-off valves 211 and control valves 209 (212 and 215 when switching adsorbers 101 and 102, respectively) remain closed, and control valves 200 are closed in the upper part of the adsorber, control valves 201 are opened, and the natural gas drained from the adsorber body is discharged through pipeline line 19 into the common line for all adsorbers for the exhaust process gas through pipeline 25.When the permissible pressure differential across shut-off valve 202 is reached, it opens, and control valve 201 closes. To equalize the pressure upstream and downstream of shut-off valves 210, 213, and 216, bypass lines are used through pipelines 6, 8, and 10, respectively.

[0066] After the pressure in the adsorber 100 has been reduced to the required level, the adsorber is switched from procedure (a) to procedure (b) of the adsorbent regeneration phase - purging the adsorber apparatus with a hot stream of low-pressure process gas, corresponding to the adsorbent regeneration stage. For this purpose, shut-off valve 211 is opened and the process gas from pipeline line 13 enters heat exchanger-heater 300, where it is heated by an external coolant, for example, hot oil, to the temperature required for adsorbent regeneration, then the hot process gas enters the hot / cold process gas supply system through pipeline 15 into adsorbers 100 (101, 102), from where it is fed through open shut-off valve 211 along pipeline line 16 to the bottom of the adsorber.Next, the hot process gas passes through the adsorbent layer from the bottom up, heating the adsorbent to the adsorbent regeneration temperature, ensuring the desorption of impurities previously adsorbed from the natural gas, and the mixture of hot process gas with desorption products is discharged through the top of adsorber 100 through open shut-off valve 202 along pipeline line 19 (21 and 23, respectively, from adsorbers 101 and 102) into the common line for all adsorbers of waste process gas through pipeline 25.Through pipeline line 25, the hot waste process gas then enters condenser-cooler 301, in which partial condensation of desorbed impurities carried away with the hot process gas occurs, the resulting two-phase mixture through pipeline line 27 enters settling tank 103, in which the condensate (water) is separated from the cooled wet process gas, which can then enter the general plant fuel gas line through pipeline line 28, and the condensate through pipeline line 29 is sent to the general plant wastewater system.

[0067] After completion of the adsorbent regeneration in the adsorber 100, the adsorber is switched from procedure (b) to procedure (c) of the adsorbent regeneration phase - purging the adsorber apparatus with a cold flow of low-pressure process gas, corresponding to the stage of cooling the adsorbent with cold cooling gas. In this case, all the shut-off valves of the adsorber 100 remain in the positions of procedure (b), and instead of the hot process gas, cold process gas is passed through the adsorbent layer, which from pipeline line 13, bypassing the heat exchanger-heater 300 along pipeline line 14, enters the hot / cold process gas supply system along pipeline 15 into the adsorbers 100 (101 and 102, respectively), from where through the open shut-off valve 211 along pipeline line 16 (17 and 18 when supplying dry regeneration gas to the adsorbers 101 and 102, respectively) it is fed to the bottom of the adsorber 100.Next, the cold process gas passes through the adsorbent layer from the bottom up, cooling the adsorbent to the required temperature, and is discharged through the top of the adsorber 100 through the open shut-off valve 202 along the pipeline line 19 into the common line for all adsorbers of the exhaust process gas along the pipeline 25, then it is cooled further in the condenser-cooler 301 and through the pipeline line 29 it can enter the general plant fuel gas line.

[0068] After the adsorbent has cooled down completely, the adsorber 100 is switched from procedure (c) to procedure (d) of the adsorbent regeneration phase - reserving the regenerated adsorbent, which allows, depending on the adsorbent's state, to switch the adsorbent apparatus to procedure (b), (c), or (e). If, due to operational requirements, for example, when reducing the flow rate of natural gas supplied for purification, the sorption activity of the adsorbent is not fully utilized, then, in order to avoid readjusting the cyclogram in procedure (d), the adsorber 100 is temporarily disconnected from process operations, while shut-off valves 202 (upper) and 211 (lower) are moved to the "closed" position.If, due to operational requirements, it is useful to increase the duration of the adsorbent regeneration (procedure (b)), the adsorbent cooling (procedure (c)) or additional adsorption of the extracted impurity (procedure (e)), then the position of the pipeline valves of procedure (d) is set in accordance with procedures (b), (c) or (e).

[0069] Following the operations in procedure (d), adsorber 100 is switched to procedure (d) of the adsorbent regeneration phase—the procedure of filling the free space of the adsorber apparatus with high-pressure natural gas until a pressure corresponding to the adsorption purification stage is reached. In this case, all pipeline valves in the lower part of adsorber 100 remain closed—shutoff valves 210, 211, control valve 209—while in the upper part, shutoff valve 202 is closed and control valve 200 is opened, ensuring the introduction of the initial high-pressure natural gas into the body of adsorber 100.

[0070] When the pressure of natural gas in adsorber 100 increases to the pressure of the adsorption stage, adsorber 100 is switched from procedure (d) to procedure (e) - the procedure of purging the adsorber apparatus with high-pressure natural gas, corresponding to the adsorption cleaning stage, while shut-off valve 210 is switched to the “open” position.

[0071] After completion of the third phase of the cyclogram, the adsorber 100 continues the adsorption purification of high-pressure natural gas in the next cycle according to the first and then the second phases of the working cycle.

[0072] The main risk associated with the operation of adsorber 100 and other adsorbers in the plant is the unpredictable failure of shut-off valves 211 (214 and 217 on adsorbers 101 and 102, respectively), which are responsible for regeneration and cooling of the adsorbent layer when switching the shut-off valve from the "closed" to the "open" position to supply hot and then cold process gas to the adsorber. This valve switching is ensured by a small permissible pressure drop on both sides of the valve (approximately 20 kPa), provided by the pressure difference between the process gas in the adsorbers and in pipeline 15 supplying hot / cold process gas to adsorbers 100, 101, and 102.Failure of the shut-off valve 211 may occur even with a slight compression of dried high-pressure natural gas into pipelines 12, 13, 14 and 15, which together form a low-pressure process gas system, which may occur due to insufficient sealing of the shut-off valve during manufacture or wear, as well as when microparticles of the adsorbent carried away with the dried natural gas get onto the pipeline valves.When even a small amount of high-pressure natural gas is forced into a low-pressure process gas system with a volume of less than 1 m3, which is a closed system with shut-off valves in the "closed" position during the entire technological cycle of the plant operation, with the exception of the operation of procedures (b) and (c), this may lead to such an increase in pressure in the process gas system that the shut-off valve will not be able to perform the operation of switching the "closed" position to the "open" position when switching to procedure (b) after completing procedure (a) for feeding the hot process stream that regenerates the adsorbent and, as a consequence, the plant will exit the standard technological mode due to a failure of the automatic cyclogram execution system.To prevent such risks, a connection is provided between the low-pressure process gas system and the bypass line of pipeline 26, equipped with control valves 218, with the common line of exhaust process gas via pipeline 25 with an even lower pressure, which makes it possible, in the event of an abnormal increase in pressure in the process gas system, to release excess pressure into pipeline line 25.

[0073] Adsorber 101 operates similarly to adsorber 100 with a shift in the cyclogram by one phase.

[0074] Adsorber 102 operates similarly to adsorber 100 with a two-phase shift in the cyclogram.

[0075] Switching of equipment operating procedures at the installation is performed automatically and can also be duplicated by the manual control mode of the installation operation.

[0076] Example. High-pressure natural gas in the amount of 120 t / h is dried in a three-adsorber adsorption unit using the method according to the claimed invention. The moisture content in the feed gas is 0.19% vol., in the dried gas - 1 ppm. Zeolite KA with a moisture capacity of 100 g / kg of adsorbent is used for gas drying. The adsorption drying stage of natural gas is carried out at a pressure of 6 MPa and a temperature of 40-30 °C, the adsorbent regeneration stage is carried out at 300 °C, the process gas pressure during regeneration and cooling of the adsorbent bed is 1.5 MPa. The permissible rate of change in the adsorbent bed temperature during heating and cooling is 50-60 °C / h. The duration of the unit operating cycle is 36 hours, the duration of each phase of the operating cycle is 12 hours. The zeolite loading capacity of one adsorber is 33 tons. The third phase ensures the restoration of the adsorption properties of the adsorbent with the following duration of procedures:

[0077] (a) - high pressure natural gas drainage procedure - 30 minutes,

[0078] (b) - the procedure for purging the adsorber apparatus with a hot stream of low-pressure process gas (adsorbent regeneration) - 4.5 hours,

[0079] (c) - the procedure for purging the adsorber apparatus with a cold stream of low-pressure process gas (cooling the adsorbent), cold cooling gas - 3.5 hours,

[0080] (g) - a procedure for reserving the regenerated adsorbent, which allows, depending on the state of the adsorbent, to switch the adsorber apparatus to procedure (b), (c) or (e) - 1 hour,

[0081] (d) - the procedure of filling the free space of the adsorber apparatus with high-pressure natural gas until the pressure corresponding to the adsorption purification stage is reached - 30 minutes,

[0082] (e) - the procedure for purging the adsorber apparatus with high-grade natural gas (adsorption drying of natural gas, with all three adsorbers operating in parallel at the adsorption stage) - 2 hours.

[0083] When procedures (a), (b), (c), (d), and (e) are performed in one of the adsorbers, the high-pressure natural gas feedstock is fed in parallel to the other two adsorbers at a rate of 60 t / h each. In this case, 66.6% of the total adsorbent load in the natural gas adsorption purification unit is utilized at the adsorption drying stage. When procedure (e) is performed in one of the adsorbers, the high-pressure natural gas feedstock is fed in parallel to all three adsorbers at a rate of 40 t / h each. In this case, 100% of the total adsorbent load in the natural gas adsorption purification unit is utilized at the adsorption drying stage.

[0084] In a typical adsorption purification scheme in three adsorbers, where one adsorber purifies the raw material, the second one regenerates the adsorbent, and the third one cools the adsorbent, only 33.3% of the total adsorbent load of the unit is utilized during the adsorption stage. Thus, the claimed method for adsorption purification of high-pressure natural gas allows for a number of technical results to be achieved: increased efficiency of adsorbent utilization by increasing the share of adsorbent providing natural gas purification during the unit operation cycle from 66.6% to 100% of the total adsorbent load of the unit when performing procedure (e); elimination of the risk of an emergency situation due to the failure of shut-off valves; and reduction of the risk of poor-quality adsorbent regeneration or cooling due to the variability of the use of the backup procedure (d).

Claims

CLAUSES OF THE INVENTION 1. A method for periodic adsorption purification of high-pressure natural gas from impurities of organosulfur substances and / or methanol and / or moisture, comprising three process stages: a stage of adsorption purification of high-pressure natural gas with a fixed bed of adsorbent, a stage of regeneration of the adsorbent with hot regeneration gas and a stage of cooling the adsorbent with cold cooling gas, implemented according to a cyclogram in a battery of N adsorbent devices filled with an adsorbent, consisting of N equal-time phases of the working cycle, wherein each of the phases characterizes the operation of the corresponding adsorber device connected by inputs and outputs to the corresponding systems for moving and processing gas flows at three stages of the process with control and shut-off valves on each flow, characterized in that in the first two phases the function of implementing the stage of adsorption purification of high-pressure natural gas with a fixed bed of adsorbent in N-1 adsorber devices is ensured,and the third phase ensures the restoration of the adsorption properties of the adsorbent by sequentially performing the following procedures in one adsorber apparatus with the estimated time for the implementation of each procedure: (a) - a procedure for draining high-pressure natural gas from the free space of the adsorber apparatus with a reduction in pressure corresponding to the adsorption purification stage to a pressure corresponding to the adsorbent regeneration stage, (b) - the procedure for purging the adsorber apparatus with a hot stream of low-pressure process gas, corresponding to the stage of adsorbent regeneration, (c) - the procedure for purging the adsorber apparatus with a cold flow of low-pressure process gas, corresponding to the stage of cooling the adsorbent with cold cooling gas, (g) - a procedure for reserving the regenerated adsorbent, which allows, depending on the state of the adsorbent, to switch the adsorber apparatus to procedure (b), (c) or (d), (d) - the procedure of filling the free space of the adsorber apparatus with high-pressure natural gas until the pressure corresponding to the adsorption purification stage is reached, (e) - a procedure for purging the adsorber apparatus with high-pressure natural gas corresponding to the adsorption purification stage, wherein the switching of the adsorber apparatus during the third phase from one procedure to another is ensured by control and shut-off valves installed on the lines of the inlet to the adsorber apparatus and the outlet from the adsorber apparatus of the high-pressure natural gas flow, the inlet of the hot or cold low-pressure process gas flow and the outlet of the spent low-pressure process gas flow; the flow of the purified initial high-pressure natural gas with impurities of moisture and organosulfur substances is divided into N-1 parts during the first two phases of the cyclogram and fed in parallel from above into N-1 adsorber apparatus or is divided into N parts during the execution of procedure (e) of the third phase and fed in parallel from above into N adsorber apparatuses, ensuring passage in each adsorber apparatus through a layer of adsorbent absorbing moisture,methanol and organosulfur substances, converted at the outlet of the adsorber apparatus into a stream of deeply purified natural gas, combined at the outlet of N-1 or N adsorber apparatuses into a common stream, which is then divided into two parts, forming a stream of deeply purified natural gas and a stream of process gas, which is then throttled to a pressure ensuring the implementation of procedures (b) and (c), while to carry out the stage of regeneration of the adsorbent according to procedure (b), the stream of low-pressure process gas is heated in a heat exchanger apparatus with a stream of coolant, fed to the bottom of the adsorber apparatus, ensuring passage through the adsorbent layer, heating the stream of process gas and, carrying with them the desorbed substances, and fed through the top of the adsorber apparatus into the low-pressure waste process gas line and, after cooling in the condenser-cooler, is separated in a separator into a humidified process gas, which is then sent through a booster compressor for mixing with the original high-pressure natural gas, or fed into the fuel gas system of the enterprise and condensate consisting of desorbed substances, which, in the absence of methanol, is sent to treatment facilities, and in the presence of methanol, is sent for thermal or catalytic neutralization, and to carry out the stage of cooling the adsorbent according to procedure (c), the flow of low-pressure process gas is fed to the bottom of the adsorber apparatus, ensuring passage through the adsorbent layer, cooling it,fed through the top of the adsorber apparatus into the low-pressure waste process gas line and then sent through a booster compressor for mixing with the high-pressure initial natural gas or sent to the enterprise's fuel gas system, the excess pressure increase in the completely isolated low-pressure process gas supply system during the execution of procedures (a), (g), (d) and (e) is compensated for by bleeding gas through a bypass line from the completely isolated low-pressure process gas supply system into the low-pressure waste process gas removal system. The system according to claim 1, characterized in that the metal rigid linear sections of the cryogenic transfer pipelines are made with vacuum insulation of the space between the rigid linear internal product pipe and the rigid linear casing.

2. The method according to paragraph 1, characterized in that silica gels are used as the adsorbent.

3. The method according to paragraph 1, characterized in that synthetic zeolites are used as the adsorbent.

4. The method according to paragraph 1, characterized in that zeolites KA are used as the adsorbent.

5. The method according to paragraph 1, characterized in that two layers of adsorbent with different adsorption characteristics are used in the adsorber apparatus.

6. The method according to paragraphs 1 and 5, characterized in that KA zeolites are used in the upper layer of the adsorbent.

7. The method according to paragraphs 1 and 5, characterized in that NaA zeolites are used in the lower layer of the adsorbent.

8. The method according to paragraph 1, characterized in that when performing procedure (b), the temperature of the adsorbent layer is gradually increased to the temperature of the adsorbent regeneration stage and then brought to a plateau.

9. The method according to paragraphs 5-7, characterized in that when performing procedure (b), the temperature of the adsorbent layer is gradually increased to an intermediate temperature, providing a layer temperature at which weakly adsorbed substances are desorbed from the lower layer of the adsorbent, the intermediate temperature is maintained during the time of their desorption, then the temperature of the adsorbent layer is gradually increased to the temperature of the stage of regeneration of the adsorbent for strongly adsorbed substances and then brought to a plateau.

10. The method according to paragraph 9, characterized in that the change in the temperature of the adsorbent layer is regulated by the flow rate of hot low-pressure process gas.

11. The method according to paragraph 1, characterized in that a process flow of hot oil is used as the heat carrier.

12. The method according to paragraph 1, characterized in that combustion products of organic fuel are used as the heat carrier.

13. The method according to paragraph 12, characterized in that a portion of the flow of high-pressure natural gas is used as the organic fuel.

14. The method according to paragraph 12, characterized in that a portion of the flow of low-pressure waste process gas is used as organic fuel.

15. The method according to paragraph 1, characterized in that the bleeding of gas through the bypass line from the completely cut-off low-pressure process gas supply system into the low-pressure process gas exhaust removal system is ensured by control valves installed on the bypass line.

16. The method according to claim 1, characterized in that a high-pressure methane-containing gas is used as the stream of high-pressure natural gas being purified.

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