CN210751324U

CN210751324U - Falling film evaporation system

Info

Publication number: CN210751324U
Application number: CN201921056778.9U
Authority: CN
Inventors: 张化福; 杨俊玲; 董艳华; 张骥; 张钰; 张振涛
Original assignee: Technical Institute of Physics and Chemistry of CAS
Current assignee: Technical Institute of Physics and Chemistry of CAS
Priority date: 2019-07-08
Filing date: 2019-07-08
Publication date: 2020-06-16
Anticipated expiration: 2029-07-08

Abstract

The utility model relates to the technical field of evaporation equipment, and discloses a falling film evaporation system, which comprises an evaporator; the evaporator comprises a cylinder and a heat exchange tube, an upper tube plate is transversely arranged above the interior of the cylinder, a lower tube plate is transversely arranged below the interior of the cylinder, and the heat exchange tube is fixedly arranged between the upper tube plate and the lower tube plate; the upper tube plate and/or the lower tube plate are/is provided with first through holes, the diameter of each first through hole is larger than the outer diameter of each heat exchange tube, and the top end and/or the bottom end of each heat exchange tube penetrate out of the first through hole; the clearance of the outside of the heat exchange tube at the first through hole is sealed by a steam seal. The utility model provides a falling film evaporation system, through setting up and adopting clearance fit to connect between end and the tube sheet of the heat exchange tube, make the heat exchange tube freely stretch out and draw back from top to bottom along the axial direction, has avoided the temperature stress to strike, improve the life of the evaporation system; and the connecting structure of the heat exchange tube does not need to be additionally provided with other components, has a simple structure and is convenient to install.

Description

Falling film evaporation system

Technical Field

The utility model relates to an evaporation equipment technical field especially relates to a falling liquid film evaporation system.

Background

The traditional evaporation heat exchange equipment has the problem of temperature stress damage. Because the heat exchange tube of the evaporator and the barrel are simultaneously influenced by temperature change, and the stretching expansion amount of the heat exchange tube and the barrel is different, a corrugated pipe compensator is often required to be arranged on the barrel to offset the difference caused by the asynchronous expansion process and reduce the stress damage to the evaporator.

The evaporation process is used as a high-energy-consumption operation unit in the industrial production process, the evaporation energy consumption accounts for a larger proportion in the salt production industry, and the evaporation energy consumption cost accounts for more than 70% of the total cost. The evaporation phase change process is in equal positions in the heat exchange tube, scaling ions are quickly supersaturated due to the evaporation of a large amount of solvent to precipitate scaling, the damage to an evaporator is huge, the scaling on the evaporation surface can cause the heat exchange efficiency to be sharply reduced, and the energy consumption loss to be sharply increased. Statistically, every 1mm of scale is added, which results in 10-20% reduction of heat exchange efficiency and 1.5-2% increase of coal consumption, or even more. The heat exchanger scaling causes huge losses every year, and the water scale can reduce the flow cross section area of the pipeline, reduce the flow and efficiency of the circulating medium, and cause the pipeline to perforate due to corrosion, causing destructive accidents.

The traditional evaporation heat exchange equipment often needs to be provided with a corrugated pipe compensator on a cylinder body for avoiding the problem of temperature stress damage, so that the structure is complex, and the problem of inconvenient connection and installation is solved.

SUMMERY OF THE UTILITY MODEL

Technical problem to be solved

The utility model aims at providing a falling liquid film evaporation system for solve or partly solve traditional evaporation indirect heating equipment and for avoiding temperature stress destruction problem often need set up bellows compensator on the barrel, lead to the structure complicated, be not convenient for connect the problem of installation.

(II) technical scheme

In order to solve the technical problem, the utility model provides a falling film evaporation system, which comprises an evaporator; the evaporator comprises a cylinder and a heat exchange tube, an upper tube plate is transversely arranged above the inside of the cylinder, a lower tube plate is transversely arranged below the inside of the cylinder, and the heat exchange tube is fixedly arranged between the upper tube plate and the lower tube plate; the upper tube plate and/or the lower tube plate are/is provided with first through holes, the diameter of each first through hole is larger than the outer diameter of the heat exchange tube, and the top end and/or the bottom end of the heat exchange tube penetrate out of the first through holes; and the clearance of the outside of the heat exchange tube at the first through hole is sealed by a steam seal.

On the basis of the scheme, the inner wall of the heat exchange tube is provided with the carbon nano tube coating, and the carbon nano tube coating sequentially comprises a metal oxide layer and a liquid metal layer combined carbon nano tube layer from the surface of the inner wall of the heat exchange tube to the central part.

On the basis of the scheme, a distributor is arranged in the barrel and above the upper tube plate and comprises a plurality of distribution plates arranged in parallel, and the distribution plates are transversely arranged in the barrel and uniformly provided with a plurality of second through holes.

On the basis of the scheme, the evaporator further comprises at least one baffle plate; the baffle plate is arranged between the upper tube plate and the lower tube plate, a plurality of third through holes are formed in the baffle plate, and the heat exchange tube penetrates through the third through holes and is fixedly connected with the baffle plate.

On the basis of the scheme, the method further comprises the following steps: a compressor, a separator, a circulating pump and a condensing tank; a liquid outlet at the bottom of the separator is connected with an inlet of the circulating pump, and an outlet of the circulating pump is connected with a first inlet at the top of the cylinder; a gas outlet at the top of the separator is connected with an inlet of the compressor, and an outlet of the compressor is connected with a second inlet, positioned between the upper tube plate and the lower tube plate, on the side wall of the cylinder body; a first outlet is arranged below the lower tube plate on the side wall of the cylinder body and communicated with the separator; and a second outlet is also arranged below the space between the upper tube plate and the lower tube plate on the side wall of the cylinder body, and the second outlet is communicated with the condensing tank.

On the basis of the scheme, a third inlet is also formed in the side wall of the cylinder body between the upper tube plate and the lower tube plate and is used for introducing external steam; a third outlet is formed in the bottom end face of the cylinder and communicated with the separator; and a feed inlet is arranged on the separator or on a pipeline between the separator and the circulating pump.

On the basis of the scheme, corrugated pipe compensators are respectively arranged on an inlet pipeline and an outlet pipeline of the compressor, an inlet pipeline and an outlet pipeline of the circulating pump and a pipeline between the cylinder and the separator.

On the basis of the scheme, the steam pressure between the outside of the heat exchange tube and the barrel is greater than the pressure in the heat exchange tube, and the pressure difference is 30-80 kPA; the difference between the diameter of the first through hole and the outer diameter of the heat exchange tube is 0.1-0.4 mm; the diameter of the second through hole is 6-12 mm; the outer diameter of the heat exchange tube is 25-57 mm; the diameter-height ratio of the heat exchange tube is 1/50-1/150; the flow velocity of the materials in the heat exchange tube is 10-30 m/s.

(III) advantageous effects

The utility model provides a falling film evaporation system, through setting up and adopting clearance fit to connect between end and the tube sheet of the heat exchange tube, make the heat exchange tube freely stretch out and draw back from top to bottom along the axial direction, has avoided the temperature stress to strike, improve the life of the evaporation system; and the connecting structure of the heat exchange tube does not need to be additionally provided with other components, has a simple structure and is convenient to install.

Drawings

FIG. 1 is a schematic structural diagram of an evaporator according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a carbon nanotube coating in an embodiment of the present invention;

fig. 3 is a schematic diagram of a falling film evaporation system in an embodiment of the present invention.

Description of reference numerals:

1-an evaporator; 2-a compressor; 3-a separator;

4-condensation tank; 5-a circulating pump; 6-steam valve;

101 — a first inlet; 102-upper pipe box; 103-a distributor;

104-an upper tube plate; 105-a bulk evaporation section; 106 — a second inlet;

107 — third inlet; 108-baffle plate; 109-heat exchange tube;

110-a metal oxide layer; 111 — liquid metal layer; 112-carbon nanotube layer;

113 — a second outlet; 114-a lower tube sheet; 115 — a first outlet;

116-lower header; 117 — third outlet.

Detailed Description

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The embodiment of the utility model provides a falling film evaporation system, refer to fig. 1, including evaporator 1; the evaporator 1 comprises a cylinder and a heat exchange tube 109, wherein an upper tube plate 104 is transversely arranged above the inside of the cylinder, a lower tube plate 114 is transversely arranged below the inside of the cylinder, and the heat exchange tube 109 is fixed through the upper tube plate 104 and the lower tube plate 114. The barrel interior space is divided into three sections by an upper tube plate 104 and a lower tube plate 114. And the upper tube plate 104 and the lower tube plate 114 are hermetically connected with the inner side wall of the cylinder body so that three sections of spaces in the cylinder body are isolated from each other. The heat exchange tube 109 is disposed in the middle section of the interior of the cylinder and is respectively communicated with the upper section and the lower section of the interior of the cylinder.

Wherein, a shell pass of the falling film evaporator 1 is formed between the outer wall surface of the heat exchange tube 109 and the upper tube plate 104, the lower tube plate 114 and the middle section cylinder; the tube pass of the falling film evaporator 1 is formed between the inner wall of the heat exchange tube 109 and the upper and lower section cylinders. The tube side and the shell side are independent of each other. Heating medium such as steam is introduced into the shell pass to heat and evaporate the materials in the tube pass.

The upper tube plate 104 and/or the lower tube plate 114 are/is provided with first through holes, the diameter of each first through hole is larger than the outer diameter of the heat exchange tube 109, the top end and/or the bottom end of the heat exchange tube 109 penetrate out of the first through hole, and correspondingly, the bottom end of the heat exchange tube 109 is fixedly connected with the lower tube plate 114 or the top end of the heat exchange tube 109 is fixedly connected with the upper tube plate 104. The heat exchange tubes 109 may be fixed at one end by a tube sheet and be in clearance fit connection with the tube sheet at the other end. Namely, one end of the heat exchange tube 109 is fixedly connected with the tube plate to fix the heat exchange tube 109; the other end is in clearance fit connection with the tube plate. Taking the top end of the heat exchange tube 109 fixedly connected to the upper tube plate 104 and the bottom end thereof in clearance fit with the lower tube plate 114 as an example:

the top end of the heat exchange tube 109 can pass through the upper tube plate 104, and the outer side wall of the heat exchange tube 109 is fixedly and hermetically connected with the upper tube plate 104. And a first through hole is arranged on the lower tube plate 114, the bottom end of the heat exchange tube 109 passes through the lower tube plate 114 from the first through hole, and a certain gap is reserved between the outer side wall of the heat exchange tube 109 and the inner wall of the first through hole on the lower tube plate 114. Further, the bottom end of the heat exchange tube 109 may protrude out of the lower tube plate 114 through the first through hole, and the protruding length may be 10-30 mm.

The heat exchange tubes 109 may also be clearance fit connected to the tube sheet at both ends. In this case, the heat exchange tube 109 may be fixed by other components, for example, a connector may be disposed at any position of the heat exchange tube 109 to achieve a fixed connection with the cylinder.

The gap at the first through hole outside the heat exchange tube 109 is sealed by a vapor seal. The sealing effect at the gap can be realized by adopting the heat source steam of the shell side through the pressure difference with the tube side, and the material of the tube side is isolated from the heat source steam of the shell side.

According to the falling film evaporation system provided by the embodiment, the end part of the heat exchange tube 109 is in clearance fit connection with the tube plate, so that the heat exchange tube 109 can freely stretch up and down along the axial direction, the temperature stress impact is avoided, and the service life of the evaporation system is prolonged; and the connecting structure of the heat exchange tube 109 does not need to be additionally provided with other components, has a simple structure and is convenient to install.

On the basis of the above embodiment, further referring to fig. 2, a carbon nanotube coating is disposed on the inner wall of the heat exchange tube 109, and the carbon nanotube coating sequentially includes a metal oxide layer 110 and a liquid metal layer 111 combined with a carbon nanotube layer 112 from the inner wall surface of the heat exchange tube 109 to the central portion.

The carbon nanotube coating starts from the inner wall surface of the heat exchange tube 109, the first layer is provided with a metal oxide layer 110, and the thickness of the metal oxide layer 110 can be 100-200 nm; the metal oxide layer 110 can improve the flatness of the inner wall surface of the heat exchange tube 109 to reduce friction with materials and reduce scaling. Then a liquid metal layer 111 is bonded to the carbon nanotube layer 112. The liquid metal layer 111 and the carbon nanotube layer 112 refer to a coating formed by bonding between the liquid metal layer 111 and the carbon nanotube layer 112. The second layer is provided with a liquid metal layer 111 which is used as a metal catalyst for growing the carbon nanotube array, controlling the density of the carbon nanotubes and realizing the directional growth. The liquid metal can be Fe, Co, Ni, Cu, Mn, Mo; the thickness of the liquid metal layer 111 may be 1-50 nm. The third layer is a carbon nanotube layer 112, wherein the diameter of the carbon nanotube is preferably 10-20nm, and the thickness of the carbon nanotube layer 112 may be 0.1-1 mm. The carbon nanotube layer 112 is in a brush shape, and can have a brush function to prevent scale.

On the basis of the above embodiment, further, a distributor 103 is arranged inside the cylinder and above the upper tube plate 104, the distributor 103 includes a plurality of distribution plates arranged in parallel, the distribution plates are transversely arranged in the cylinder, and a plurality of second through holes are uniformly arranged on the distribution plates.

Specifically, the distributor 103 may be composed of 2-3 layers of porous distribution plates. The aperture of the second through hole on the distribution plate can be 6-12 mm; the material that can be better distributes. The multilayer distribution plates are arranged in parallel, and the second through holes in the multilayer distribution plates can be arranged in a one-to-one up-down correspondence mode, and also can not be arranged in a cross mode, and limitation is not required. The material enters from a material inlet at the top end of the cylinder of the falling film evaporator 1, after being homogenized by the distributor 103, the material enters the heat exchange tube 109 along the round hole of the distributor 103 and soaks the inner wall, and the material flows from top to bottom.

On the basis of the above embodiment, further, the evaporator 1 further comprises at least one baffle 108; the baffle plate 108 is arranged between the upper tube plate 104 and the lower tube plate 114, and a plurality of third through holes are formed in the baffle plate 108. The heat exchange pipe 109 passes through the third through hole and is fixedly connected with the baffle plate 108. The baffle 108 and the heat exchange tube 109 may be connected by welding.

The baffle plate 108 plays a role in preventing the shell-side heat source steam from rapidly descending and changing the flow direction of the heat source steam, and is beneficial to sufficient heat exchange between the heat source steam and the materials. The thickness of the baffle plate 108 is designed to be 5-15 mm. A plurality of baffles 108 may be arranged in the axial direction of the heat exchange tube 109, and the distance between any two adjacent baffles 108 is controlled to be 1 to 1.5 m. The baffle plate 108 is provided with a plurality of third through holes for being connected with the heat exchange tube 109, so that the position of the baffle plate 108 in the cylinder body can be conveniently adjusted by adjusting the third through holes connected with the heat exchange tube 109, and a baffling effect is better played.

On the basis of the above embodiment, further, with reference to fig. 3, a falling film evaporation system further includes: compressor 2, separator 3, circulation pump 5 and condensate tank 4. The liquid outlet at the bottom of the separator 3 is connected with the inlet of the circulating pump 5, and the outlet of the circulating pump 5 is connected with the first inlet 101 at the top of the cylinder. The material in the separator 3 is transported by the circulation pump 5 through the first inlet 101 to the tube side space for evaporation.

The gas outlet at the top of the separator 3 is connected to the inlet of the compressor 2, and the outlet of the compressor 2 is connected to the second inlet 106 in the side wall of the cylinder between the upper tube plate 104 and the lower tube plate 114. The compressor 2 extracts the vapor at the top of the separator 3 and delivers it to the shell side space as heat source vapor.

A first outlet 115 is arranged below the upper tube plate and the lower tube plate 114 on the side wall of the cylinder body, and the first outlet 115 is communicated with the separator 3; a second outlet 113 is also arranged on the side wall of the cylinder below the space between the upper tube plate 104 and the lower tube plate 114, and the second outlet 113 is communicated with the condensing tank 4. The material after each evaporation enters the separator 3 through the first outlet 115 for vapor-liquid separation. The heat source steam after heat exchange enters the condensing tank 4 through the second outlet 113 for condensation and recovery. The material in the separator 3 is circulated for several times for evaporation.

On the basis of the above embodiment, further, a third inlet 107 is further arranged on the side wall of the cylinder between the upper tube plate 104 and the lower tube plate 114, and the third inlet 107 is used for introducing external steam; the third inlet 107 is used for introducing external steam into the shell side space as heat source steam. A third outlet 117 is arranged on the bottom end surface of the cylinder body, and the third outlet 117 is communicated with the separator 3; the third outlet 117 is disposed on the bottom end surface of the cylinder, which facilitates smooth discharge of all materials in the tube pass space. A feed inlet is arranged on the separator 3 or on a pipeline between the separator 3 and the circulating pump 5. The feed may be initially through the feed inlet.

On the basis of the above embodiment, further, the inlet pipeline and the outlet pipeline of the compressor 2, the inlet pipeline and the outlet pipeline of the circulating pump 5, and the pipeline between the cylinder and the separator 3 are respectively provided with a bellows compensator. The conduits between the cartridge and the separator 3 may specifically be a conduit between the first outlet 115 and the separator 3 and a conduit between the third outlet 117 and the separator 3.

On the basis of the above embodiment, further, the vapor pressure between the heat exchange tube 109 and the cylinder is greater than the pressure inside the heat exchange tube 109, and the pressure difference is 30-80 kPA; the pressure difference value can realize steam seal, and meanwhile, the safety is good and the realization is easy. The difference between the diameter of the first through hole and the outer diameter of the heat exchange tube 109 is 0.1-0.4 mm; the size of the gap can satisfy the temperature stress deformation of the heat exchange tube 109 and the cylinder body, so that the two do not influence each other, the stability of the structure is improved, and the size of the gap is easy to realize steam sealing.

The diameter of the second through hole is 6-12 mm. The outer diameter of the heat exchange tube 109 is 25-57 mm; the diameter-height ratio of the heat exchange tube 109 is 1/50-1/150. The size of the heat exchange tube 109 can enable materials to form a film shape better, and is beneficial to improving the heat exchange evaporation efficiency. The flow velocity of the materials in the heat exchange tube 109 is 10-30m/s, which is beneficial to improving the evaporation efficiency.

Further, the difference in the heat transfer temperature of the evaporator 1 is preferably 4 to 7 ℃. The saturated temperature rise of the steam of the compressor 2 depends on the property of the material to be treated, and when the material is a sodium sulfate solution, the saturated temperature rise of the compressor 2 is preferably 10-12 ℃; when the material is sodium chloride solution, the saturated temperature rise of the compressor 2 is preferably 15-17 ℃; when the solution is a sodium nitrate solution, the saturated temperature rise of the compressor 2 is preferably 20 to 22 ℃.

On the basis of the foregoing embodiment, further, a falling film evaporation method using the falling film evaporation system described in any of the foregoing embodiments includes: a pressure difference is formed between a shell-side space between the outside of the heat exchange tube 109 and the cylinder and a tube-side space inside the heat exchange tube 109; adding materials into the separator 3, and starting the circulating pump 5 to inject the materials into the tube side space according to a preset flow rate when the liquid level of the materials reaches a first preset value; and continuously adding the materials into the separator 3, and stopping feeding when the liquid level of the materials reaches a second preset value.

On the basis of the above embodiment, further, a pressure difference is formed between a shell-side space between the outside of the heat exchange tube 109 and the cylinder and a tube-side space inside the heat exchange tube 109, which specifically includes: when the compressor 2 is in a screw or Roots type, starting the compressor 2, and forming a pressure difference between a shell-side space and a tube-side space by the operation of the compressor 2; when the compressor 2 is of a centrifugal type, the compressor 2 is started, and simultaneously, external steam is input into the shell side space to form a pressure difference.

The specific charging operation process of the falling film evaporation system provided in the above embodiment is as follows: when the compressor 2 is of the screw or roots type, a first operating step is carried out; the second operating step is carried out when the compressor 2 is of the centrifugal type. The first operation step is as follows: the compressor 2 is turned on and a steady pressure differential is established between the tube side and the shell side of the evaporator 1 by virtue of the suction and pressurization of the compressor 2. The second operation step is as follows: and (3) opening a third inlet 107 on the cylinder, namely opening a steam valve 6 connected with an external steam source, conveying fresh steam to the shell side of the evaporator 1, and forming pressure difference between the tube side and the shell side by means of the pressure of the steam to realize a sealing condition.

Feeding to the falling film evaporator 1, starting the circulating pump 5 when the liquid level reaches a first liquid level set value of the separator 3, and continuing feeding; the feed location may be located at the inlet of the circulation pump 5 or at the vapor space barrel section of the separator 3. And when the liquid level of the material reaches the second liquid level set value of the separator 3, stopping feeding, and finishing the feeding process.

This falling film evaporation system gets into the concentrated stage of feed liquid after reinforced completion, specifically does: the material from the separator 3 firstly enters a circulating pump 5, is pressurized by the circulating pump 5 and then is input into a top material inlet, namely a first inlet 101, of the falling film evaporator 1; after being processed by the distributor 103, the heat exchange tube 109 is fed into the heat exchange tube 109, and a liquid film is formed on the inner wall of the heat exchange tube 109 to exchange heat with steam outside the tube; the materials are heated and gasified, and the generated vapor-liquid mixture falls to the bottom of the falling film evaporator 1 and enters the separator 3 through a pipeline communicated with the separator 3 to realize vapor-liquid separation; the separated liquid sinks to the bottom and enters the circulating pump 5 again to complete the next circulation, and when the feed liquid reaches the specified concentration, the feed liquid is discharged out of the system.

And then a condensed water extraction stage: the secondary steam separated by the separator 3 rises, is discharged from a steam outlet, namely a gas outlet, at the top of the separator 3, and enters the steam compressor 2; after being heated and pressurized, the condensed water enters the shell pass of the falling film evaporator 1, exchanges heat with materials on the tube pass, is condensed to form condensed water, is discharged from a second outlet 113 which is a condensed water outlet at the bottom of the falling film evaporator 1, flows to the condensing tank 4 through a connecting pipeline, and is finally discharged from the condensing tank 4.

On the basis of the above embodiment, further, the embodiment provides a falling film evaporator 1 and a use method thereof, and the connection mode of the heat exchange tube 109 and the tube plate is modified aiming at the problem that the working process of the evaporator 1 is damaged by temperature stress under the special conditions and working conditions of the use of the falling film evaporator 1. The falling film evaporator 1 includes an upper tube plate 104, a heat exchange tube 109, a baffle 108, a lower tube plate 114, an upper tube body, a middle tube body, and a lower tube body. In the cylinder, an upper section cylinder is arranged above the upper tube plate 104, a middle section cylinder is arranged between the upper tube plate 104 and the lower tube plate 114, and a lower section cylinder is arranged below the lower tube plate 114.

An upper pipe box 102 is formed between the upper section of the cylinder body and the upper pipe plate 104 and between the upper section of the cylinder body and the material inlet, namely the first inlet 101; the middle section cylinder, an upper tube plate 104, a heat exchange tube 109, a baffle plate 108, a lower tube plate 114, a steam inlet, namely a second inlet 106, a third inlet 107 and a condensed water outlet, namely a second outlet 113 form a main evaporation section 105; a lower pipe box 116 is formed between the lower section cylinder body and a material outlet, namely a third outlet 117, and a bypass outlet, namely a first outlet 115; the upper tube box 102 is detachably connected to the main evaporation section 105, and the main evaporation section 105 is detachably connected to the lower tube box 116, and may be connected by flanges.

The heat exchange tube 109 is connected with the lower tube plate 114 in a clearance fit manner, a certain clearance is reserved between the outer wall of the heat exchange tube 109 and the inner wall of the first through hole of the lower tube plate 114, the size of the clearance is 0.05-0.2mm, the heat source steam of the shell pass of the evaporator 1 is adopted to realize a sealing effect, and the material of the tube pass of the evaporator 1 is isolated from the heat source steam of the shell pass. The length of the lowest end of the heat exchange tube 109 extending out of the lower tube plate 114 is 10-30 mm. The traditional expansion and welding mode is replaced, the problem of stress damage caused by asynchronous expansion change between the heat exchange tube 109 and the barrel of the evaporator 1 due to temperature change can be solved, the heat exchange tube 109 can freely stretch and retract along the vertical axial direction and flexibly move, the temperature stress damage is avoided, and the service life is prolonged.

The surface of the inner wall of the heat exchange tube 109 is plated with a carbon nano tube coating, the carbon nano tube coating comprises an oxide layer and a liquid metal layer 111 combined with a carbon nano tube layer 112, and the thickness of the carbon nano tube layer 112 is 0.1-1 mm. The coating can solve the problems of serious equipment scaling, performance attenuation, heat efficiency reduction and energy consumption increase in the working process of the evaporator 1. The inner wall surface of the heat exchange tube 109 is used as a substrate, a carbon nano tube directional growth technology is adopted, and a carbon nano tube coating is added on the inner wall surface, so that the effects of scale inhibition and descaling and heat exchange enhancement can be achieved.

Further, the present embodiment provides an MVR falling film evaporation system comprising the falling film evaporator 1 described in any of the above embodiments. The MVR falling film evaporation system consists of a falling film evaporator 1, a compressor 2, a separator 3, a circulating pump 5 and a condensed water tank.

The steam inlet, namely the second inlet 106, of the falling film evaporator 1 is connected with the outlet of the compressor 2 through a pipeline; a condensed water outlet (i.e. a second outlet 113) of the falling film evaporator 1 is connected with a water inlet of a condensed water tank through a pipeline; a material inlet, namely a first inlet 101, of the falling film evaporator 1 is connected with an outlet of the circulating pump 5 through a pipeline; the material outlet of the falling-film evaporator 1, i.e. the first outlet 115, is connected via a line to the material inlet of the separator 3.

Specifically, the outlet of the compressor 2 is connected with the steam inlet, i.e. the second inlet 106, of the falling film evaporator 1, the inlet of the compressor 2 is connected with the steam outlet, i.e. the gas outlet, of the separator 3, and the inlet and outlet pipelines of the compressor 2 are provided with the corrugated pipe compensators.

Specifically, the outlet of the circulating pump 5 is connected with the material inlet, i.e. the first inlet 101, of the falling film evaporator 1, the inlet of the circulating pump 5 is connected with the material outlet, i.e. the liquid outlet, of the separator 3, and the inlet and outlet pipelines of the circulating pump 5 are provided with the corrugated pipe compensators.

Compared with the prior art, the falling film evaporator 1 and the falling film evaporation system provided by the embodiment have the following advantages: the heat exchange tube 109 of the evaporator 1 is treated by adopting a carbon nano tube coating, which has the function similar to a brush, realizes scale inhibition and scale removal and high-efficiency heat exchange. The heat exchange tube 109 and the tube plate are connected in a clearance fit mode, the heat exchange tube 109 can freely stretch along the vertical axial direction, temperature stress impact is avoided, and the service life of the evaporator 1 is prolonged. The heating steam medium of the shell side of the evaporator 1 has multiple functions and effects, the waste heat of secondary steam of an evaporation system is recycled, the heating steam medium is used as a heat source medium to heat a tube side material, and meanwhile, the heating steam medium is also used as a sealing medium to prevent the tube side material from leaking to the shell side.

The pressure difference between the shell side and the tube side of the evaporator 1 is realized by utilizing the self-pressurization effect of the compressor 2, the additional pressurization power cost is not required, and the additional operation cost is not required in the operation process. The carbon nanotube coating structure and the processing method provided by the embodiment can be applied to other types of evaporators 1 or heaters, such as forced circulation heaters, climbing-film evaporators 1 and the like.

In the clearance fit manner between the heat exchange tube 109 and the tube plate provided by this embodiment, the heat exchange tube 109 can be separately clearance fitted with the lower tube plate 114; or the heat exchange tube 109 is separately clearance-fitted with the upper tube plate 104; or the heat exchange tube 109 is in clearance fit with the upper and lower tube plates 114 at the same time, the baffle plate 108 can be arranged to be connected with the inner wall of the cylinder, and the heat exchange tube 109 can be fixed through the baffle plate 108 or other components.

Further, this example provides an MVR falling film evaporation system with an evaporation capacity of 5 tons/hour, wherein the material component is a sodium chloride solution, the feeding mass concentration is 4%, the discharging mass concentration is 20%, and each parameter of the MVR falling film evaporation system is as follows:

preferably, the evaporation temperature is 95 ℃, the pressure of the evaporator 1 is 84.6kPA, and an MVR falling film circulating type evaporation process is adopted. Preferably, the falling-film evaporator 1 has the main parameters: heat exchange area 400m²The heat exchange tube 109 is phi 38mm multiplied by 1.2mm in specification, the length of the heat exchange tube 109 is 8m, the heat exchange tube 109 is made of industrial pure titanium TA2, other materials are 2205 stainless steel, the cylinder is phi 1200mm multiplied by 6mm in specification, and the thickness of the external heat-insulating layer is 50 mm.

Preferably, the vapor compressor 2 has the main parameters: the saturated temperature rise of the water vapor is 10 ℃, the flow rate is 5t/h, a screw compressor 2 is adopted, and the motor power of the compressor 2 is 165 kW. Separator 3 main parameters: the cylinder size is phi 2200mm 8mm, and cylinder height H equals 3000mm, and the cylinder sets up the reinforcement circle, and reinforcement circle interval 1m, material 2205 stainless steel, heat preservation thickness 50 mm.

Preferably, the condensation tank 4 has the main parameters: the size of the cylinder body is phi 1000mm multiplied by 6mm, the length H of the cylinder body is 1500mm, a horizontal structure type is adopted, the thickness of the heat-preservation layer is 50mm, and the heat-preservation cotton is rock wool. Main parameters of the circulating pump 5: flow rate of 120m³The pump head is 25m in lift, the material is 2205 stainless steel, a centrifugal water pump is adopted, the inlet and outlet type is a flat inlet and outlet type, and the sealing type of the water pump is a double-end-face mechanical seal.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A falling film evaporation system comprising an evaporator; the evaporator comprises a cylinder and a heat exchange tube, an upper tube plate is transversely arranged above the inside of the cylinder, a lower tube plate is transversely arranged below the inside of the cylinder, and the heat exchange tube is fixedly arranged between the upper tube plate and the lower tube plate; the heat exchange tube is characterized in that the upper tube plate and/or the lower tube plate is/are provided with first through holes, the diameter of each first through hole is larger than the outer diameter of the heat exchange tube, and the top end and/or the bottom end of the heat exchange tube penetrate out of the first through hole; and the clearance of the outside of the heat exchange tube at the first through hole is sealed by a steam seal.

2. The falling film evaporation system of claim 1, wherein the heat exchange tubes are provided with a carbon nanotube coating on the inner wall thereof, the carbon nanotube coating comprising a metal oxide layer and a liquid metal layer in combination with a carbon nanotube layer in order from the inner wall surface to the central portion of the heat exchange tubes.

3. The falling film evaporation system according to claim 1, wherein a distributor is arranged inside the cylinder and above the upper tube plate, the distributor comprises a plurality of distribution plates arranged in parallel, the distribution plates are transversely arranged in the cylinder, and a plurality of second through holes are uniformly arranged on the distribution plates.

4. The falling film evaporation system of claim 1, wherein the evaporator further comprises at least one baffle plate; the baffle plate is arranged between the upper tube plate and the lower tube plate, a plurality of third through holes are formed in the baffle plate, and the heat exchange tube penetrates through the third through holes and is fixedly connected with the baffle plate.

5. The falling film evaporation system according to any one of claims 1 to 4, further comprising: a compressor, a separator, a circulating pump and a condensing tank; a liquid outlet at the bottom of the separator is connected with an inlet of the circulating pump, and an outlet of the circulating pump is connected with a first inlet at the top of the cylinder;

a gas outlet at the top of the separator is connected with an inlet of the compressor, and an outlet of the compressor is connected with a second inlet, positioned between the upper tube plate and the lower tube plate, on the side wall of the cylinder body;

a first outlet is arranged below the lower tube plate on the side wall of the cylinder body and communicated with the separator; and a second outlet is also arranged below the space between the upper tube plate and the lower tube plate on the side wall of the cylinder body, and the second outlet is communicated with the condensing tank.

6. The falling film evaporation system according to claim 5, wherein a third inlet is further provided on the side wall of the cylinder between the upper tube plate and the lower tube plate, and the third inlet is used for introducing external steam; a third outlet is formed in the bottom end face of the cylinder and communicated with the separator; and a feed inlet is arranged on the separator or on a pipeline between the separator and the circulating pump.

7. The falling film evaporation system according to claim 6, wherein bellows compensators are provided in the inlet and outlet pipes of the compressor, in the inlet and outlet pipes of the circulation pump, and in the pipes between the drum and the separator, respectively.

8. The falling film evaporation system according to claim 3 wherein the vapor pressure between the outside of the heat exchange tubes and the drum is greater than the pressure inside the heat exchange tubes and the pressure difference is 30-80 kPA; the difference between the diameter of the first through hole and the outer diameter of the heat exchange tube is 0.1-0.4 mm; the diameter of the second through hole is 6-12 mm; the outer diameter of the heat exchange tube is 25-57 mm; the diameter-height ratio of the heat exchange tube is 1/50-1/150; the flow velocity of the materials in the heat exchange tube is 10-30 m/s.