JP3477251B2 - Evaporator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporator for evaporating a liquid to be treated. 2. Description of the Related Art An evaporator is for evaporating a liquid to be treated. For example, there is an evaporator that utilizes heat of combustion exhaust gas from a combustion device or the like. In an evaporator using this flue gas, the heat of the flue gas is recovered as steam or the like by an exhaust heat recovery device, the temperature of the liquid to be treated is raised by the vapor, and the heated liquid to be treated is flash drummed. To evaporate under reduced pressure,
An exhaust heat recovery device that recovers the heat of the combustion exhaust gas as steam, a heat exchanger that raises the temperature of the liquid to be treated by the steam of the exhaust heat recovery device, and the liquid that is heated by the heat exchanger is evaporated. And a flash drum for gas-liquid separation. [0004] Incidentally, the above-mentioned evaporator is mainly composed of three devices, that is, an exhaust heat recovery device, a heat exchanger and a flash drum, and heat of combustion exhaust gas, for example, exhaust heat recovery. In order to eliminate the problem caused by the adhesion of the heat transfer surface (heat transfer tube) of the scale which occurs when the temperature of the liquid to be treated is raised and evaporated by the vapor from the apparatus, the temperature of the liquid to be treated is raised by the vapor and then the flash drum is used. Evaporated. For this reason, piping and a management system for connecting these three devices are required, which complicates the entire system and incurs an increase in equipment costs. Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an evaporator which can evaporate a liquid to be treated with a simple system. [0006] In order to achieve the above object, the present invention provides an evaporator for evaporating a liquid to be treated,
A downcomer pipe that evaporates by a heating medium while spraying and lowering the liquid to be processed from above, and a gas separation unit provided below the downcomer pipe and separating only the evaporated gas component,
Buoyancy by heating part of the gas separated by the gas separation unit
After raising giving, a riser and back <br/> in the downcomer to circulate in the evaporator as the heating medium, the gas separation unit, the mist from the gas therein And a gas inflow body disposed below the mist separator and guiding only gas to the riser. The liquid to be treated is sprayed into the downcomer and is directly evaporated by the heating medium while descending. When the scale adheres, the scale is the inner wall of the downcomer. There is no hindrance. Also, by heating a part of the vaporized gas to raise the inside of the riser, the gas has a sufficient amount of heat to evaporate the liquid to be treated sprayed due to an overheated state, and this is returned to the downcomer, It contributes to the evaporation of the liquid to be treated. As described above, a part of the self-evaporated gas is overheated and used for its own evaporation, so that no other medium is required and the system can be simplified. Therefore, the gas to be treated can be evaporated with a simple system. In addition,
The mist separator removes mist from the gas
Gas and gas below the mist separator.
Gas riser that guides the
Clean gas flows into the pipe, and the heat transfer surface becomes dirty.
It is extremely low and cleans the heat transfer surface even after a long operation.
Is no longer necessary. An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a vertical cylindrical high-temperature
A downcomer capable of withstanding high pressure is shown, and a supply pipe 2 for a liquid to be treated is connected to the top of the downcomer 1. The supply pipe 2 for the liquid to be treated extends inside the downcomer pipe 1 along its axis, and a spray nozzle 3 for spraying the liquid to be treated is attached to the tip. The lower part of the downcomer pipe 1 is enlarged in diameter to form a gas separation section 4.
An umbrella-shaped mist separator 5 for removing mist in the gas and lowering the removed mist along the inner wall is provided above the enlarged diameter portion (gas separation portion) 4. I have. Mist separator 5 in enlarged diameter part 4
In the lower central portion, a vertical cylindrical gas inflow body 6 is provided coaxially and the upper side is opened, and only gas flows into the gas inflow body 6. I have.
A drain pipe 7 for discharging drain is connected to the bottom of the gas inflow body 6. A lower portion of the enlarged diameter portion 4 is gradually reduced in diameter and formed in a hopper shape, and a discharge pipe 10 having a rotary valve 9 driven by a motor 8 is connected thereto. It is being discharged. A first gas discharge pipe 11 for discharging a part of the gas is connected to a side surface (peripheral surface) of the gas inflow body 6.
A pressure gauge 1 for detecting the pressure in the pipe 11 is provided on the gas discharge pipe 11.
2 and a pressure control valve 13 are provided, and the opening of the pressure control valve 13 is adjusted in accordance with the detection value of the pressure gauge 12. A second gas discharge pipe 14 for discharging a part of gas is connected to the upper part of the downcomer pipe 1. The second gas discharge pipe 14 has a pressure gauge 15 for detecting the pressure in the pipe 14 and a pressure control valve. A pressure control valve 16 is provided with a pressure gauge 15.
The opening degree is adjusted in accordance with the detected value of. The first and second discharge pipes 11 and 14 discharge gas using one or both of them according to the purpose. For example, when the discharged gas is used after being cooled, the gas is discharged using only the first gas discharge pipe 11. As an example, there is a case where the evaporator of the present invention is applied to a seawater desalination plant. When the energy of the gas is used, the gas is discharged through the second gas discharge pipe 14. As an example, there is a case where the present invention is applied to a waste liquid treatment apparatus. As shown in FIGS. 1 and 2, a plurality (five in the illustrated example) of inflow headers 17 into which a part of the gas flows are attached to the side surface of the gas inflow body 6. These inflow headers 17 have parallel portions 17a formed substantially in parallel on a horizontal plane at predetermined intervals.
In addition, above the spray nozzle 3 of the downcomer pipe 1, an outflow header 18 that is paired (opposed) with the inflow header 17.
Are mounted, and a number of risers 19 are vertically extended between the parallel portions of the headers 17 and 18. Combustion exhaust gas from a combustion device or the like passes through the riser pipe 19 at right angles (both at right angles to the parallel portion of the header). The riser pipe 19 acts as a heat transfer tube to heat the gas inside the pipe 19 with the combustion exhaust gas. A heat input section (exhaust heat recovery section) 20 is formed to constitute an evaporator 21 according to the present invention. Thus, the gas in the riser pipe 19 is heated by the combustion exhaust gas to obtain buoyancy, rises in the pipe 19, and returns to the downcomer pipe 1 via the outflow header 18. That is, by guiding only the gas to the riser pipe 19 and heating the riser pipe 19 by the external heat, the gas has a lower density than that of the descending fluid descending in the downcomer pipe 1 and rises with buoyancy. In other words, the gas becomes overheated, so it has enough heat to evaporate the liquid to be treated.
Circulate. The circulating force (F) of this gas is expressed by the following equation (1). F = H (r _D −r _R ) (1) where F: circulation force (kg / m ² ), H: height (m), r
_D : density in the downcomer (kg / m ³ ), r _R : density in the ascender (kg / m ³ ). The relationship between the amount of circulation (Wc) and the amount of liquid to be treated (W) is expressed by the following equation (2). ## EQU2 ## Here, W: supply amount of the liquid to be treated (kg / h),
Wc: circulation amount (kg / h), i _F : enthalpy of the liquid to be treated (kJ / kg), i _S : enthalpy in the downcomer (kJ / kg),
i _h : enthalpy (kJ / kg) at the outlet of the riser, η: efficiency. [0018] From the equation (2), the circulation rate is a factor of the processing liquid supply amount _{(i S -i F) / (} i h -i S), depending on how to set the enthalpy, i.e. riser 19 The circulation amount can be set arbitrarily depending on how many times the gas temperature after passing (temperature of the gas in an overheated state) is set, and the circulation amount is set according to the liquid to be treated. Specifically, when the liquid to be treated is a waste liquid, the supply amount of the
Preferably, it is about twice. In addition, if the temperature difference between the downcomer pipe and the riser pipe is made large, the circulation amount may be small. The liquid to be treated is evaporated in the downcomer pipe 1,
A circulating system for returning a part of the gas into the downcomer pipe 1 via the ascending pipe 19 due to the density difference is formed. Then, the liquid to be treated is sprayed from the spray nozzle 3 into the downcomer 1 under high temperature and high pressure. Then, the liquid to be treated evaporates due to the amount of heat held by the circulating gas, and this gas forms a downward flow in a state where a part of solid or liquid is mixed at a relatively high density. In this downward flow, solids or liquids are separated by a gas separation unit 4 mainly by a mist separator 5, and the solids or liquids are discharged from a discharge pipe 10 via a rotary valve 9. A part of the separated gas is discharged from the first and / or second discharge pipes 11 and 14 and guided to another system for processing. The remainder is led from the gas inlet 6 to the riser 19 via the inlet header 17.
The riser pipe 19 is heated by combustion exhaust gas from a combustion device or the like, that is, external heat. As a result, the fluid (gas) in the riser pipe 19 has a lower density than the descending fluid and has buoyancy, rises in the pipe 19, and after ascending, is returned into the descender pipe 1 via the outflow header 18. Circulate. Since the returned gas is heated and rises in the riser pipe 19 to be in an overheated state, the returned gas has a sufficient amount of heat to evaporate the sprayed liquid to be processed. To contribute. As described above, since the liquid to be treated evaporates directly by a part of the gas which has self-evaporated and overheated while descending in the downcomer pipe 1, even if scale is generated at the time of evaporation, the liquid to be treated is not evaporated. Since the scale adheres to the inner wall of the downcomer pipe 1, the scale does not hinder the evaporation of the liquid to be treated. Also,
Since a part of the self-evaporated gas is overheated by the external heat such as combustion exhaust gas and used for its own evaporation, no other medium is required and the system can be simplified. Therefore,
The gas to be treated can be evaporated with a simple system. Further, since the liquid is evaporated at a high pressure, the size of the apparatus can be reduced. Further, the gas separation unit 4
Mist separator 5 for removing the mist and the mist separator
Is arranged below the radiator 5 and guides only gas to the riser 19.
The gas separation unit 4 is provided with the gas inflow body 6, and the gas separation performance in the gas separation unit 4 can be improved. Therefore, the rising pipe 19
Since clean gas flows into the inside, dirt of the heat transfer surface is extremely less, even a long time driving the cleaning of the heat transfer surfaces becomes unnecessary. Furthermore, since the liquid to be treated is sprayed and evaporated, the liquid to be treated can be applied from a low concentration to a high concentration regardless of the concentration. Since the inside of the downcomer pipe and the inside of the riser pipe are at high temperature and high pressure, another gas may be injected to perform a desired reaction. For example, when the liquid to be treated is a waste liquid, air may be injected into the riser to burn some or all of the combustible substances in the waste liquid, thereby reducing or eliminating the need for an external superheated fluid. FIG. 3 is a configuration diagram showing an example in which the evaporator of the present invention is applied to a waste liquid treatment apparatus. In FIG. 3, reference numeral 21 denotes the evaporator, and a waste liquid pipe 30 as a supply pipe for the liquid to be treated is connected to the top of the downcomer pipe 1 of the evaporator 21. The waste liquid pipe 30 is connected to a waste liquid tank 31, and most of the waste liquid stored in the waste liquid tank 31 is a mixture of a plurality of waste liquids, and the pH is adjusted to 7 to 8. The waste liquid pipe 30 includes a waste liquid pump 32 and a flow control valve 33.
And a flow meter 34, and the flow controller 35 adjusts the opening of the flow control valve 33 based on the detection value of the flow meter 34. The pressure gauge 15 is provided above the downcomer 1.
And a gas pipe 14 serving as a second gas discharge pipe having a pressure control valve 16. The gas pipe 14 is connected to a gas burner 37 of an incinerator 36. The incinerator 36 has a vertical cylindrical shape and is lined with a refractory material, and a fuel burner 38 is provided at the top. An air pipe 41 having an air preheater 39 and an air blower 40 is connected to the fuel burner 38.
1 is an air bypass pipe 4 for bypassing the air preheater 39.
2 is connected, and an air preheater 39 is provided by an open / close valve 43 interposed between the air pipe 41 and the bypass pipe 42.
The amount of inflow to the system is adjusted. The fuel burner 38 has a heavy oil line 4 having a heavy oil pump 44.
5 is connected, and the fuel oil in the fuel oil tank 46 is supplied to the fuel burner 38.
The gas (waste liquid) from the gas pipe 14 is thermally decomposed (oxidized) by being blown into the incinerator 36 and burning.
It is supposed to be. An exhaust gas duct 48 for guiding combustion exhaust gas to a chimney 47 is connected to the lower side of the incinerator 36. The exhaust gas duct 48 is connected to the exhaust heat recovery section 20, the cyclone 49, and the air preheater 39 of the evaporator 21. , An exhaust fan 50, a slaked lime mixing section 51, and a bag filter 52 are sequentially provided. By performing the exhaust gas treatment in a dry manner in this way, prevention of white smoke,
It can save water and so on. Now, the waste liquid is evaporated in the downcomer pipe 1 and a part of this gas is heated by the riser pipe 19 and then returned to the downcomer pipe 1 to form a circulation system. Spray the waste liquid. The sprayed waste liquid is heated by the gas passing through the rising pipe 19 and evaporates while descending in the pipe 1.
Part of the evaporated gas flows into the riser pipe 19, is heated by the external heat (combustion exhaust gas), rises inside the riser pipe 19, and then returns to the downcomer pipe 1. Since this gas is heated and rises inside the riser pipe 19 to be in an overheated state, it has a sufficient amount of heat to evaporate the sprayed liquid to be processed, and thus contributes to the evaporation of the liquid to be processed. I do. The remainder of the evaporated gas is injected into the incinerator 36 through the gas pipe 14, where it is subjected to a thermal decomposition treatment (oxidation treatment). The combustion exhaust gas from the incinerator 36 is supplied to the evaporator 2
For example, the exhaust heat recovery unit 20 cools the temperature from 850 ° C to 300 ° C,
After being collected by the cyclone 49, it is further cooled to 250 ° C. by the air preheater 39. After the slaked lime is mixed and neutralized through the exhaust fan 50, the dust is collected again by the bag filter 52, and then discharged to the atmosphere from the chimney. That is,
After the flue gas is recovered by heat in the boiler, it is cooled to near the heat-resistant temperature (about 200 ° C) of the bag filter and then released to the atmosphere. The ash containing heavy metals captured by the cyclone 49 and the bag filter 52 is separately sent to a processing system for regeneration or disposal. As described above, the waste liquid is directly evaporated by a part of the gas which has been self-evaporated and overheated while descending in the downcomer 1, and this is heat-treated in the incinerator 36. The system is simplified because it is used to heat the self-evaporated gas from the flue gas. That is, when evaporating the waste liquid and performing heat treatment in an incinerator, it has been proposed to use three devices, ie, an exhaust heat recovery device, a heat exchanger, and a flash drum. Can evaporate the waste liquid, thereby reducing the number of devices and simplifying the system. FIG. 4 is a block diagram showing an example in which the evaporator of the present invention is applied to a seawater desalination apparatus. In FIG.
Denotes the evaporator, and the exhaust heat recovery section 20 of the evaporator 21
The combustion exhaust gas from the combustion device 60 is supplied as an external heating medium. The combustion device 60 injects fuel such as heavy oil and air from an air blower 61 or air preheated through an air preheater 62 from a plurality of burners 63 to burn the fuel. It flows into the heat recovery unit 20. The combustion exhaust gas passing through the exhaust heat recovery unit 20 is released to the atmosphere from the chimney 64 via the air preheater 62. A seawater supply pipe 65 as a supply pipe for the liquid to be treated is connected to the top of the downcomer pipe 1 of the evaporator 21. The seawater supply pipe 65 is provided with a seawater pump 66, a flow control valve 67, and a flow meter 68 so that the flow controller 69 adjusts the opening of the flow control valve 67 based on the detection value of the flow meter 68. The seawater whose flow rate is partially adjusted from the seawater pump 66 is supplied to the downcomer 1. The remainder of the seawater is supplied to the condenser 70 as a cooling medium. The pressure gauge 12 is provided below the downcomer 1.
A gas pipe 11 as a first gas discharge pipe having a pressure control valve 13 is connected, and the vapor evaporated in the downcomer pipe 1 flows into the gas pipe 11 and is guided to the condenser 70. The condenser 70 is for condensing steam with a cooling medium (seawater). A drain pipe 72 having a control valve 71 is connected to the bottom of the condenser 70 and the level of the condensed liquid in the condenser 70 is reduced. The control valve 7 is detected based on the detected value.
A level controller 73 for adjusting the opening degree is provided, and the level of the vapor condensed by the level controller 73 is maintained in a predetermined range. Now, a fuel system is burned by the combustion device 60, seawater is evaporated in the downcomer pipe 1, and a part of the steam is heated by the ascending pipe 19 and then returned to the downcomer pipe 1 to form a circulation system. . When seawater is sprayed into the downcomer pipe 1, the seawater is evaporated by being heated by the steam passing through the ascending pipe 19 while descending in the pipe 1. Part of the evaporated steam is
9 and is heated by external heat (combustion exhaust gas)
It is overheated and returned into the riser 1 and contributes to the evaporation of the liquid to be treated. The remainder of the steam is passed through a gas line to the condenser 70
To be condensed there. As described above, the seawater self-evaporates while descending in the downcomer pipe 1 and is directly evaporated by a part of the superheated steam, which is condensed to obtain water, and the seawater is desalinated. As a result, the system is simplified. Therefore, the evaporator 21 of the present invention can be applied to a waste liquid treatment device or a seawater desalination device, and the system can be simplified, and can be applied to other devices such as a milk powder production device. In summary, according to the present invention, there is an excellent effect that the liquid to be treated can be evaporated with a simple system. In addition, the heat transfer surface inside the riser has very little dirt,
The cleaning becomes unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing one embodiment of the present invention. FIG. 2 is a view taken along the line AA in FIG. FIG. 3 is a configuration diagram showing an example in which the evaporator of the present invention is applied to a waste liquid treatment device. FIG. 4 is a configuration diagram showing an example in which the evaporator of the present invention is applied to a seawater desalination apparatus. [Description of Signs] 1 Downcomer 4 Gas separation unit 19 Ascending tube

Claims (1)

(57) [Claim 1] In an evaporator for evaporating a liquid to be treated,
A downcomer pipe that evaporates by a heating medium while spraying and lowering the liquid to be processed from above, and a gas separation unit provided below the downcomer pipe and separating only the evaporated gas component,
Buoyancy by heating part of the gas separated by the gas separation unit
After raising giving, a riser and back <br/> in the downcomer to circulate in the evaporator as the heating medium, the gas separation unit, the mist from the gas therein An evaporator comprising: a mist separator for removing gas; and a gas inflow body disposed below the mist separator and guiding only gas to the riser.