SUMMERY OF THE UTILITY MODEL
The utility model discloses the technical problem that needs to solve provides a embrane method flue gas moisture recovery system based on siphon, can not only solve the difficult problem that the membrane module moved under the negative pressure, can also solve the online problem of washing of membrane module, further reduces the energy consumption, practices thrift the running cost.
In order to solve the technical problem, the utility model adopts the following technical proposal.
A membrane-method flue gas moisture recovery system based on siphoning comprises a water tank, a variable-frequency circulating water pump, a membrane assembly inlet header, a membrane assembly for flue gas moisture recovery and a membrane assembly outlet header, wherein the water tank, the variable-frequency circulating water pump, the membrane assembly inlet header, the membrane assembly outlet header and the membrane assembly outlet header are sequentially communicated through a pipeline, the membrane assembly inlet header is positioned below a flue and used for caching circulating water, the membrane assembly outlet header plays a role in air separation and prevents circulating water at a membrane assembly outlet from splashing, and the top of the membrane; the membrane module, the membrane module inlet header, the membrane module outlet header and the water tank are arranged from a high position to a low position;
the side wall of the middle upper part of the membrane component inlet header is provided with a low level liquid level switch connected through a pipeline, the middle lower part and the middle upper part of the vertical pipe of the inlet header are respectively communicated with a middle overflow control valve and a high overflow control valve through pipelines, and the middle overflow control valve and the high overflow control valve are communicated to a water tank through overflow pipes; the height of the high-position overflow control valve is higher than that of the highest membrane tube in the membrane module, and the height of the middle-position overflow control valve is lower than that of the lowest membrane tube;
an inlet electric control valve is arranged on a pipeline for connecting the membrane module inlet header with the membrane module, the membrane module outlet header is connected with the membrane module through a first-stage descending pipe, and an outlet electric control valve is arranged at one end of the first-stage descending pipe close to the membrane module outlet header; the installation height of the outlet electric adjusting door is lower than the height of a low-level liquid level switch on the membrane component inlet header;
the membrane component outlet header is communicated with the water tank through a second-stage downcomer.
Above-mentioned embrane method flue gas moisture recovery system based on siphon effect, be provided with the circulating water cooling heat exchanger that is used for the cooling circulation water on the pipeline between water tank and the frequency conversion circulating water pump.
Above-mentioned embrane method flue gas moisture recovery system based on siphon effect, the water tank is for having the open to air water tank of overflow mouth, blowdown mouth and delivery port of emptying.
According to the membrane-method flue gas moisture recovery system based on the siphon effect, the highest membrane tube or the highest point of the outlet of the membrane assembly is provided with the pressure gauge for monitoring whether the membrane tube is full of water or not.
Above-mentioned embrane method flue gas moisture recovery system based on siphon, be provided with the level gauge that is used for continuous monitoring water level in the import header riser, the top of import header riser is provided with the air-vent valve.
Due to the adoption of the technical scheme, the utility model has the following technical progress.
The utility model discloses in using embrane method flue gas moisture recovery system with the siphon principle, positive negative pressure state through reasonable control system realizes the switching that the membrane module washed at negative pressure running state and online malleation, on the water basis is received to the embrane method that realizes the flue gas, further realizes the online of membrane module and washes, guarantees the cleanness of system, has not only reduced the complexity and the investment cost of system, has also reduced the energy consumption of flue gas moisture recovery moreover, has practiced thrift the running cost.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
A membrane-method flue gas moisture recovery system based on siphoning effect is structurally shown in figure 1 and comprises a water tank 1, a circulating water cooling heat exchanger 11, a variable-frequency circulating water pump 2, a membrane module inlet header 4, a membrane module 14 and a membrane module outlet header 18 which are sequentially communicated through a pipeline, wherein the top of the membrane module inlet header 4 is communicated with an inlet header vertical pipe 5 which is vertically upward; the water tank 1, the circulating water cooling heat exchanger 11 and the variable-frequency circulating water pump 2 are arranged at a low position, an outlet of the variable-frequency circulating water pump 2 is communicated with an inlet header 4 of the membrane module through an ascending pipe 3, an outlet header 18 of the membrane module is connected with the membrane module 14 through a first-stage descending pipe 16, and an outlet header 18 of the membrane module is communicated with the water tank 1 through a second-stage descending pipe 19. The membrane module 14, the membrane module inlet header 4, the membrane module outlet header 18 and the water tank 1 are arranged from a high position to a low position.
The utility model discloses in, water tank 1 is open to the air water tank, and its main effect is the vapor in the flue gas of storage circulating water and membrane module collection. The open type empty water tank is provided with an overflow port, an emptying drain outlet and a water outlet, wherein the outlet water can be led to a main desulfurization water replenishing pipe or an external circulating water replenishing pipe or a process water tank or boiler water replenishing pipe and the like according to the condition of water quality.
The circulating water cooling heat exchanger 11 is used to cool the circulating water used by the system. The frequency conversion circulating water pump 2 adopts a centrifugal water pump and is used for conveying circulating water in the system, and the flow of the circulating water can be adjusted according to the operating state requirement of the system.
The membrane component inlet header 4 is used for caching circulating water; the membrane component is positioned below the flue and is not higher than the bottommost part of the flue, otherwise, the membrane component at the bottom of the flue cannot establish negative pressure; but should not be too low and the height needs to be less than the height corresponding to the maximum vacuum at which the membrane tube establishes a siphon. The side wall of the middle upper part of the membrane component inlet header 4 is provided with a low level liquid level switch 7 connected with a pipeline.
The middle lower part and the middle upper part of the inlet header vertical pipe 5 are respectively communicated with a middle position overflow control valve 8 and a high position overflow control valve 9 through pipelines, and the middle position overflow control valve 8 and the high position overflow control valve 9 are communicated to the water tank 1 through an overflow pipe 10. Wherein, the height of the high position overflow control valve 9 is higher than that of the highest membrane tube in the membrane component 14, and the height of the middle position overflow control valve 8 is lower than that of the lowest membrane tube. A liquid level meter 6 for continuously monitoring the water level is arranged in the inlet header vertical pipe 5, the height of the inlet header vertical pipe 5 is higher than the highest point of the flue, and an air exhaust valve 12 is arranged at the top of the inlet header vertical pipe.
The membrane module inlet header 4 and the inlet header vertical pipe 5 provide water source for the membrane module inlet and can also adjust the liquid level. When the air exhaust valve 12 is in an open state and the liquid level drops below the middle overflow control valve 8, the membrane module 14 is in a negative pressure operation state under the siphon action, that is, the flue gas is subjected to water vapor separation.
The membrane module 14 is used for recovering moisture in flue gas. The highest membrane tube or the highest point of the outlet of the membrane module 14 is provided with a pressure gauge 15 for monitoring whether the membrane tube is full of water.
The membrane module outlet header 18 plays a role in the air and prevents circulating water at the membrane module outlet from splashing, and is also positioned below the flue and lower than the liquid level in the membrane module inlet header 4. An inlet electric adjusting valve 13 is arranged on a pipeline connecting the membrane module inlet header 4 and the membrane module 14, and an outlet electric adjusting valve 17 is arranged at one end of the primary downcomer 16 close to the membrane module outlet header 18; the outlet electric valve 17 is arranged at a height lower than the height of the low level liquid level switch 7 on the membrane component inlet header 4.
The utility model discloses in can adopt siphon principle to realize that the embrane method flue gas receives the prerequisite of water be, be full of the circulating water in the difference in height of membrane module import header and membrane module export header and the system.
The utility model discloses a water and the online malleation back flush step of membrane module are received to the water injection before the flue gas moisture retrieves and system operation in-process membrane module negative pressure mainly including the system operation, and the negative pressure operation of membrane module and the liquid level height of online malleation back flush operating condition through adjustment import header riser realize.
The specific method of the water injection process of the system comprises the following steps: closing the middle overflow control valve 8, the high overflow control valve 9, the air exhaust valve 12 and the outlet electric regulating valve 17, and opening the inlet electric regulating valve 13; and then starting the variable-frequency circulating water pump 2, monitoring the pressure of a pressure gauge 15 at the highest point of the membrane module to be 0.15-0.2 MPa, closing an inlet electric regulating valve 13 and an outlet electric regulating valve 17, opening a high-level overflow control valve 9, monitoring a liquid level meter 6, adjusting the variable-frequency circulating water pump 2 to reduce the flow of circulating water until the high-level overflow control valve 9 is in a micro-overflow state, and finishing the positive-pressure water injection of the system at the moment.
The specific method for collecting water by the membrane module under negative pressure comprises the following steps: after the water injection process is finished, opening an air exhaust valve 12, an inlet electric regulating valve 13, an outlet electric regulating valve 17 and a middle position overflow control valve 8 until the water level of the inlet header vertical pipe 5 is reduced to the height of the middle position overflow control valve 8, establishing a system siphon state, and enabling the membrane component to be in a negative pressure operation state; when the membrane module is in a negative pressure operation process, the water level height in the system is maintained between the height of the low-level liquid level switch 7 and the height of the middle-level overflow control valve 8 by controlling the circulating water flow of the variable-frequency circulating water pump 2. If the water level is reduced too fast, the circulating water flow of the variable-frequency circulating water pump 2 is increased, so that the water level is maintained above the installation height of the low-level liquid level switch 7, and the siphon water cut-off is avoided.
The specific method of the membrane module online positive pressure back flushing is that in the running state, the middle position overflow control valve 8 is closed, the variable frequency circulating water pump 2 is adjusted to increase the circulating water flow, the water level is gradually increased until the height of the high position overflow control valve 9, at the moment, the highest point pressure gauge 15 of the membrane module displays that the pressure is changed from negative to positive, and the system carries out the positive pressure flushing process.
After the flushing is finished, the middle overflow control valve 8 is opened, the variable frequency circulating water pump 2 is adjusted to reduce the circulating water flow, the water level is gradually reduced until the height of the middle overflow control valve 8, the siphon state of the system is established again, and the membrane module is in a negative pressure operation state.
The utility model discloses in, still can reduce the degree of depth that one-level downcomer 16 stretched into in the membrane module export header 18 through increasing the back and adjust the liquid level difference that the membrane module advances membrane module export header and the flow of membrane module internal circulation water.
In the embodiment, the tail flue of a 300MW unit boiler of a power plant is additionally provided with a membrane module to recover flue gas water, and the height of the positions of the membrane module inlet header 4 and the membrane module outlet header 18 in the calculation engineering is checked to verify the rationality of the application of the siphoning effect in the membrane water receiving technology.
Assuming that the height from the inlet header of the membrane module to the membrane module is 4.68m, and the height from the outlet header of the membrane module to the outlet header of the membrane module is 7.38m, the height difference H between the inlet header of the membrane module and the outlet header of the membrane module is 2.7 m. And taking values of other data: the length of the membrane module and the horizontal pipeline is 11.2m, namely the total length of the siphon pipeline is 7.38+4.68+11.2 which is 23.26 m. The roughness coefficient of the membrane module and the water pipeline is 0.011, the on-way resistance coefficient is 0.018, the local resistance coefficient is 27.73, and the membrane module and the water pipeline specifically comprise a right-angle inlet of 0.5, an outlet of 0, butterfly valves (two sets of fully-opened a/d is 0.2), vacuum stop valves (two sets of vacuum stop valves) of 10 and a membrane module (comprehensive value) of 17.19.
Checking the calculation process and the description.
(1) As long as the vacuum in the siphon is not broken, anThe liquid level of the membrane component inlet header and the liquid level of the membrane component outlet header are kept at a certain height difference H, and the siphon can continuously convey water. Considering that the flow rate of the internal circulation water for receiving water by the membrane method is large, the height difference H is not lower than 1 m. As shown in fig. 2, the siphon belongs to submerged outflow, and neglecting the flow velocity in the membrane module inlet header and the membrane module outlet header, taking H as 2.7m, and all the pipe diameters as 0.565m, and is calculated by formula 1: the circulating water flow is 0.34m3The flow velocity in the opposing membrane tube was 1.36 m/s.
Therefore, the flow rate of circulating water in the membrane tube is lower than 1.5m/s (the flow rate is taken from the design data of a membrane module manufacturer), so the height difference H of the inlet header and the outlet header of the membrane module is basically reasonable.
(2) The minimum and maximum vacuum in the siphon tube occur at section a and section B in fig. 2, respectively. The vertical distance H from the section with the maximum vacuum degree in the siphon to the liquid level of the membrane component inlet headersReferred to as the installation height of the siphon. However, when the vacuum degree in the siphon pipe is too large, the water body is vaporized, and the water delivery effect of the siphon pipe is affected. In order to ensure normal operation of siphon tube in engineering, the maximum vacuum degree in the limiting tube must not exceed the allowable value [ H ]v]The water column is 7-8 m.
The total length of the pipeline in front of the section B is 15.88 meters, the local resistance coefficient is 22.71, and the method can be obtained according to the formula 2: the mounting height Hs is 4.76m, which is greater than 4.68m from the inlet header to the membrane module.
Generally, α is 1, Hv7 m. It can be seen that the greater the installation elevation, the lower the flow rate.
Similarly, the total loss H of the pipeline after the section B can be calculatedw0.47m, a pressure at section B of 33.64kPa, and a total loss H of the pipe after section AwIs 2.57m, section AAt a pressure of 54.18 kPa. The saturated vapor pressure at the water temperature of 45 ℃ is 9.855kPa, and because the pressure at the section B of the siphon pipe is far greater than the saturated vapor pressure at the water temperature of 45 ℃, the water in the siphon pipe cannot be vaporized at the position, and simultaneously the requirement condition of the membrane pipe for negative pressure operation is also met.
From the above calculation, the installation height H of the siphon tubesThe vacuum degree of the siphon is 4.76m, is slightly larger than the length from the membrane component inlet header to the membrane component by 4.68m, is smaller than the maximum vacuum degree in the siphon and cannot exceed the allowable value of 7-8 m of water column, so the height value of the membrane component inlet header is basically reasonable.
The utility model discloses during the in-service use, can preset between membrane module and the membrane module import header, between membrane module and the export header and the membrane module import header and the membrane module export the height between the header, carry out the rationality that the value was verified to the velocity of flow of membrane intraductal circulating water and the intraductal maximum vacuum of siphon under the siphon state.