Horizontal column

Abstract

FIELD: chemical; petrochemical; gas engineering.SUBSTANCE: invention relates to equipment for heat and mass transfer processes. The horizontal column consists of at least two mass-exchange sections, each of which includes a mass-exchange element, a liquid accumulation cavity and a liquid distribution device, ejectors in a quantity one less than the quantity of mass-exchange sections, to each of which a high-pressure liquid supply pipeline, a low-pressure liquid supply pipeline and a liquid supply pipeline from the ejector are connected. Each pipeline for supplying liquid from the ejector is connected to the liquid distribution device of the mass-exchange section, starting from the second one, and each pipeline for supplying low-pressure liquid is connected to the liquid accumulation cavity of the mass-exchange section, preceding the one with which the corresponding ejector is connected. The first mass transfer section is equipped with liquid inlet and gas outlet pipes, and the last one is equipped with liquid outlet and gas inlet pipes. The mass transfer sections are connected by gas flow channels.EFFECT: mobility and reliability of the distillation column.5 cl, 3 dwg

Description

[0001] The invention relates to the field of chemical, petrochemical and gas engineering, namely to the hardware design of heat and mass transfer processes, and can be used to conduct contact between gas (steam) and liquid in the processes of rectification, absorption and desorption and is intended to conduct heat and mass transfer processes between gas (steam) and liquid.

[0002] In many industries, distillation columns—equipments designed to facilitate the rectification process, a heat and mass transfer process that results in the separate condensation of vapor components—are used to separate liquid mixtures whose components have different boiling points. The classic column design is a vertical cylinder with contact devices inside.

[0003] Currently, only vertical distillation columns are used in industry. While vertical tray columns have been in operation for over 100 years, transportation and installation of such columns are complex, and operation, maintenance, and troubleshooting are unsafe and costly. Therefore, many researchers have attempted to develop horizontal distillation columns, but the development of functional horizontal columns remains challenging.

[0004] A horizontal distillation apparatus manufactured by REOTEK LLC (see http: / / www.reotek.com / upload / docs / goriz_rekt_apparati_REOTEK.pdf) is known from the prior art. It is designed for both the separation of liquid hydrocarbon feedstock into fractions (rectification) and the absorption of substances from a gas mixture (absorption). According to the company, the diameter of the apparatus ranges from 200 to 1800 mm, and their weight is approximately 2 times less compared to vertical columns of the same capacity. The apparatus offered by REOTEK LLC has an all-welded design with external thermal insulation for safe operation. In a horizontal distillation apparatus, gas (vapor) moves along the length of the apparatus due to the pressure difference at the inlet and outlet, and the liquid (raw material) moves in the opposite direction due to the energy of the vapor. In the REOTEK LLC apparatus, the functions of the plates where contact between liquid and gas occurs are performed by contact chambers.Intensive mixing of the liquid and gas occurs in the contact zone, after which the liquid (the final petroleum product) is discharged in a direction opposite to the gas flow, while the gas moves to the next chamber. All chambers of the apparatus are fractionating, meaning petroleum product extraction can be arranged from any chamber of the apparatus without any design modifications. A disadvantage of this type of column is that the energy of the gas is used to ensure the countercurrent flow of the liquid and gas, resulting in a large pressure drop across the column. This often necessitates the construction of an additional compressor station to utilize the gas extracted from the column.

[0005] Another embodiment of a horizontal heat and mass transfer column is known (see Author's Certificate SU 319317, published November 2, 1971), which features a horizontal column for contacting gas with liquid, comprising a body internally sectioned by bubbling and profiled overflow partitions. To intensify the process, plates with ends bent in the direction of liquid flow are located between the partitions, forming nozzles with profiled partitions and cavities interconnected by a tray for liquid overflow. This invention utilizes nozzles that also experience a significant pressure drop, so when implementing this invention, a large pressure drop will also be observed across the column.

[0006] The closest technical solution to the claimed one is the design of a horizontal fractionation column (see US Patent 9855515, published January 2, 2018), which consists of small interconnected vessels arranged horizontally. Trays with the same structure and the same or similar size as an equivalent vertical tray column are located near the bottom of each vessel. The vessels have the same or reduced diameter as the equivalent vertical tray column. Each section operates sequentially, similar to an equivalent vertical column. The lower part of the body of each vessel is connected to a drain device in the upper part of the body of the next vessel in the liquid flow, repeating the liquid flow movement in the vertical column.Cross-flow of liquid and vapor phases between vessels is maintained by connecting the vapor outlet of one vessel to the bottom of the next vessel in the gas flow path and by moving a controlled amount of liquid from the bottom of one vessel to the top of the next vessel using a pump and valve arrangement. A centrifugal pump with an appropriate pressure and flow rate is placed in the liquid supply line connecting two successive vessels. A flow control valve at the pump outlet controls the flow of liquid from one vessel to the next. Excess liquid from the pump outlet is returned to the vessel from the pump inlet side through a liquid recirculation line to avoid excessive backpressure in the pump. A liquid recirculation check valve is located in the recirculation line to prevent liquid / vapor backflow.In this invention, countercurrent gas and liquid movement is achieved by using pumps between each adjacent vessel. For high-quality column operation, the number of vessels can reach ten or more, and the number of pumps will be one less than the number of vessels (nine or more). Such a large number of pumps significantly reduces the column's operational reliability.

[0007] The objective of the claimed technical solution is to develop a column in a horizontal or inclined state, designed with the ability to eliminate pressure drop.

[0008] The technical result of the claimed invention is to reduce capital costs for providing the foundation, as well as to ensure the mobility and reliability of the distillation column.

[0009] The technical result is achieved in that the horizontal distillation column consists of at least two mass-exchange sections, each of which includes a mass-exchange element, a liquid accumulation cavity and a liquid distribution device, ejectors in a number one less than the number of mass-exchange sections, to each of which a pipeline for feeding high-pressure liquid to the ejector, a pipeline for feeding low-pressure liquid to the ejector and a pipeline for feeding liquid from the ejector are connected. Each pipeline for feeding liquid from the ejector is connected to the liquid distribution device of the mass-exchange section, starting from the second one, and each pipeline for feeding low-pressure liquid to the ejector is connected to the liquid accumulation cavity of the mass-exchange section preceding the mass-exchange section to which the corresponding ejector is connected via a pipeline for feeding liquid from the ejector.The first mass-transfer section is equipped with liquid inlet and gas outlet ports, while the last mass-transfer section is equipped with liquid outlet and gas inlet ports. The mass-transfer sections are connected in series by gas flow channels.

[0010] The gas flow channels between the mass transfer sections can be installed so that one end is connected to the bottom of the previous mass transfer section and the other end is connected to the top of the next mass transfer section.

[0011] Plate or packed mass transfer elements can be used as mass transfer elements.

[0012] The liquid outlet pipe and gas inlet pipe can be connected to the heating unit.

[0013] The outlet of the heating unit can be designed with the possibility of connection to pipelines for supplying high-pressure liquid to the ejectors and supplying condensate formed at the outlet of the heating unit through them.

[0014] The claimed invention is explained by illustrations: Fig. 1 shows a schematic diagram of a horizontal column, Fig. 2 shows a schematic diagram of an ejector, Fig. 3 shows a schematic diagram of an evaporator.

[0015] The numbers indicate the following:

[0016] 1 - mass transfer section,

[0017] 2 - mass transfer element,

[0018] 3 - fluid accumulation cavity,

[0019] 4 - liquid distribution device,

[0020] 5 - ejector,

[0021] 6 - liquid supply pipeline from the ejector,

[0022] 7 - high-pressure liquid supply pipeline to the ejector,

[0023] 8 - low-pressure liquid supply pipeline to the ejector,

[0024] 9 - inlet liquid flow into the column,

[0025] 10 - liquid outlet flow from the column,

[0026] 11 - inlet gas flow into the column,

[0027] 12 - high-pressure liquid flow,

[0028] 13 - outlet gas flow from the column,

[0029] 14 - ejector receiving chamber,

[0030] 15 - ejector nozzle,

[0031] 16 - mixing chamber,

[0032] 17 - tapering part of the channel,

[0033] 18 - diffuser,

[0034] 19 - stable liquid,

[0035] 20 - evaporator,

[0036] 21 - coolant flow into the evaporator,

[0037] 22 - coolant flow from the evaporator.

[0038] The design of the claimed horizontal distillation column includes at least two mass-exchange sections 1, each of which includes a mass-exchange element 2, a liquid accumulation cavity 3 and a liquid distribution device 4. The column also includes ejectors 5, the number of which is one less than the number of mass-exchange sections 1. Connected to each ejector 5 are pipelines for feeding liquid from the ejectors 6 to the liquid distribution devices 4, pipelines for feeding high-pressure liquid 7 and pipelines for feeding low-pressure liquid 8 from the liquid accumulation cavities 3. The first mass-exchange section is the mass-exchange section into which the input liquid flow is fed into the column 9, from which gas is also withdrawn in the form of an output gas flow 13, released in the first mass-exchange section.Thus, the connection of the ejectors 5 to the liquid distribution devices 4 begins with the second (subsequent) mass-exchange section 1 by means of liquid supply pipelines from the ejectors 6, and the liquid accumulation cavities 3 are connected by low-pressure liquid supply pipelines 8 with the ejectors 5 corresponding to these liquid accumulation cavities 3, that is, up to the penultimate mass-exchange section 1. The last mass-exchange section 1 is connected to the nozzles for the liquid outlet flow from the column 10 and the gas inlet flow into the column 11. Between the mass-exchange sections 1, gas flow channels are installed so that one end is connected to the lower part of the previous mass-exchange section, and the other end is connected to the upper part of the subsequent mass-exchange section. Figure 1 illustrates an example of a horizontal column consisting of four mass-exchange sections 1 and three ejectors 5.

[0039] In the design of the mass-exchange sections 1, liquid distribution devices 4 are used, which are known from the prior art, for example, jet-type devices that supply liquid in separate streams (distribution plates, troughs, “spiders”, perforated pipes, sprinklers and Segner wheel-type sprinklers), or spraying devices, in which the liquid supplied to the nozzle is broken up into drops (plate-type, multi-cone and rotating centrifugal sprinklers).

[0040] The mass-transfer elements 2 of the mass-transfer sections 1 utilize well-known solutions. For example, tray mass-transfer elements or packed mass-transfer elements. Common valve or cap trays, for example, can be used as trays (internal devices of tray distillation columns) of the tray mass-transfer elements. If sieve trays are used within the mass-transfer elements 2, these trays will be installed horizontally and contain numerous small holes evenly distributed over the entire tray surface. Overflow tubes are used to drain the liquid and regulate its level on the tray. The lower ends of the tubes are immersed in cups on the underlying trays, forming hydraulic seals. The cap trays each contain a single round cap and a gas passage pipe. The edges of each cap are immersed in the liquid.This creates a hydraulic seal on the tray, forcing the gas exiting the cap to pass through a layer of liquid on the tray. The caps have holes or serrated slots to break up the gas into small bubbles, thereby increasing the surface area of ​​contact between the gas and the liquid. Valve trays are flat, perforated plates, each perforation of which is equipped with a movable disc ("valve"). The valves move up or down depending on the gas flow rate. At normal flow rates, the valve is approximately in the mid-position. At low evaporation rates, the valve closes the plate. The valves must be heavy enough to prevent excessive opening at low gas flow rates. Packed mass transfer elements can be either structured or loose. The choice of mass transfer element type 2 depends on the flow rate of the processed medium; at higher flow rates, disc mass transfer elements are preferable.For low flow rates of the processed medium, packed mass-transfer elements are more convenient. Furthermore, the type of mass-transfer element determines the ability to handle substances that tend to form deposits on the contact surface.

[0041] Liquid accumulation cavities 3 are separate reservoirs.

[0042] The ejectors 5 used in the horizontal distillation column are jet pumps known from the prior art, the operation of which is based on the Bernoulli principle, when the pressure energy of a moving fluid is converted into kinetic energy (velocity) when it flows through a relatively small converging-diverging nozzle. The ejectors 5 used in the design of the inventive column consist of a receiving chamber 14, a nozzle 15, a mixing chamber 16, a converging section of the channel 17 and a diffuser 18. The basic diagram of the ejectors 5 used is shown in Fig. 2. The ejectors are not as efficient as most types of pumps and compressor equipment, but have the advantage of a simple design and the absence of moving parts, which ensures the reliability of their operation, as well as minimal maintenance costs.Other advantages of using ejectors in a column design compared to, for example, pumps and compressors include the absence of moving parts, no need for electrical power supply for operation, low capital and operating costs, environmental safety (no emissions), light weight and compact dimensions, reliable and safe operation, simple control, and low noise levels.

[0043] The outlet liquid flow branch pipe from column 10 and the inlet gas flow branch pipe into column 11 are connected to a heating unit, which is represented by evaporator 20. The schematic diagram of evaporator 20 is shown in Fig. 3. Evaporator 20 is a horizontal heat exchanger with two operating zones: the tube side and the annular space, each of which has its own design pressure, design temperature, and material design. In the case of a horizontal column, evaporator 20 is used to maintain the gas condensate stabilization process in the column by transferring heat from the coolant to the unstable gas condensate. The main part of evaporator 20 is a tube bundle with U-shaped tubes. The tube bundle of this apparatus is constantly immersed in the liquid entering from the column in the form of stream 10. A hot coolant in the form of stream 21 is pumped inside the tube bundle.A discharge pipe 19 for the remaining stable liquid after evaporation is connected to the bottom of evaporator 20, the other end of which is connected to a pump. An air cooler for cooling the stable condensate of stable liquid 19 may be installed after the pump, as well as a discharge pipe for the stable liquid condensate 19 into high-pressure liquid pipeline 12.

[0044] The horizontal distillation column operates as follows. The inlet liquid stream into column 9 to be separated passes through liquid distribution device 4 and enters in a known manner into mass-transfer element 2 of the first mass-transfer section 1. The inlet liquid inside mass-transfer element 2 is bubbled in a known manner by gas flows, which have entered in the form of inlet gas stream 11 through the last mass-transfer section 1 and gas overflow channels. In this manner, the main part of the mass-transfer process occurs, after which the liquid flows from mass-transfer element 2 in a known manner into liquid accumulation cavity 3, from where it is fed via low-pressure liquid supply pipeline 8 into first ejector 5. The gas, having reached the upper part of mass-transfer section 1, flows through gas overflow channel to the lower part of the next mass-transfer section 1, where the mass-transfer process is repeated.High-pressure liquid from flow 12 enters receiving chamber 14 of the same ejector 5 via high-pressure liquid supply pipeline 7. The increased velocity of the moving liquid through nozzle 15 (high-pressure liquid) causes a corresponding decrease in pressure, creating suction in mixing chamber 16, into which liquid is drawn (passive flow). High-pressure liquid (process fluid) mixes with the entrained flow of low-pressure liquid (driving fluid) in mixing chamber 16. Then the mixed flow passes through converging section of channel 17 and converging-expanding diffuser 18, where the velocity is converted back into pressure energy. The resulting pressure at the outlet exceeds the suction pressure of ejector 5. The resulting mixture enters via liquid supply pipeline 6 from the outlet of ejector 5 into liquid distribution device 4 of the second mass-transfer section 1, then the process occurs similarly to the first mass-transfer section 1.From the liquid accumulation cavity 3 of the last mass-exchange section 1, the output liquid flow from the column 10 is collected. From the upper part of the first mass-exchange section 1, the output gas 13, separated from the input liquid flow, is collected.

[0045] The interaction of liquid and gas entering the column is carried out in mass-exchange elements 2 by bubbling gas through a layer of liquid on the plates (in the case of using plate-type mass-exchange elements) or by surface contact of gas and liquid on the packing (in the case of using packed-type mass-exchange elements) or on the surface of the liquid flowing down as a thin film.

[0046] The liquid outlet stream from column 10, having passed through all mass-transfer sections 1, enters evaporator 20 from the horizontal column, where primarily the light fractions are evaporated and returned to the column as inlet gas stream 11, while the stable liquid 19 remaining after evaporation is withdrawn from the bottom of evaporator 20 and directed to the pump inlet. After the pumps, the stable liquid stream 19 is divided into stable condensate, which is diverted to an air cooler, where it is cooled and then sent for storage, and condensate, which is used as high-pressure liquid stream 12 in ejectors 5, and is divided between them accordingly. The hot coolant provides heating for evaporator 20.

[0047] The claimed invention makes it possible to operate a distillation column in a horizontal or inclined state and achieve the following advantages:

[0048] - reduce capital costs for providing the foundation on which the column is installed, since with a horizontal arrangement the column can be installed on a slab,

[0049] - ensure the mobility of the column, since the specified design is easily disassembled and, accordingly, has the ability to quickly transport the column from one site to another;

[0050] - ensure the exclusion of excessive pressure drop inside the column, which affects the reliability of the entire equipment.

Claims

1. A horizontal distillation column characterized in that it consists of at least two mass-exchange sections, each of which includes a mass-exchange element, a liquid accumulation cavity and a liquid distribution device, ejectors in a quantity one less than the number of mass-exchange sections, to each of which a pipeline for feeding high-pressure liquid to the ejector, a pipeline for feeding low-pressure liquid to the ejector and a pipeline for feeding liquid from the ejector are connected, wherein each pipeline for feeding liquid from the ejector is connected to the liquid distribution device of the mass-exchange section, starting from the second one, and each pipeline for feeding low-pressure liquid to the ejector is connected to the liquid accumulation cavity of the mass-exchange section, preceding the mass-exchange section to which the corresponding ejector is connected by means of a pipeline for feeding liquid from the ejector, the first mass-exchange section is equipped with pipes for inlet of liquid and outlet of gas,and the last mass-exchange section is equipped with liquid outlet and gas inlet pipes, while the mass-exchange sections are sequentially connected by channels for gas flow.

2. A horizontal distillation column according to claim 1, characterized in that the channels for gas flow between the mass-exchange sections are installed so that one end is connected to the lower part of the previous mass-exchange section, and the other end to the upper part of the subsequent mass-exchange section.

3. A horizontal distillation column according to paragraph 1, characterized in that plate or packed mass transfer elements are used as mass transfer elements.

4. A horizontal distillation column according to paragraph 1, characterized in that the liquid outlet pipe and the gas supply pipe are connected to the heating unit.

5. A horizontal distillation column according to paragraph 4, characterized in that the outlet of the heating unit is designed with the possibility of connection to pipelines for supplying high-pressure liquid to the ejectors and supplying condensate formed at the outlet of the heating unit through them.

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