CN112473243A - Purification system and regeneration method of degraded molten nitrate salt - Google Patents
Purification system and regeneration method of degraded molten nitrate salt Download PDFInfo
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- CN112473243A CN112473243A CN202011501639.XA CN202011501639A CN112473243A CN 112473243 A CN112473243 A CN 112473243A CN 202011501639 A CN202011501639 A CN 202011501639A CN 112473243 A CN112473243 A CN 112473243A
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Abstract
A purification system and a regeneration method of degraded molten nitrate salt are disclosed, wherein the purification system comprises a molten salt submerged pump I, a stirring barrel, a closed plate filter and a compressed air heater; a molten salt submerged pump I is installed in a salt tank; a heat-preservation jacket I is arranged outside the stirring barrel, a stirrer and a fused salt submerged pump II are arranged in the stirring barrel, a filtered slurry discharge port is arranged at the bottom of the stirring barrel, and a fused salt outlet of the heat-preservation jacket I and a fused salt inlet of the heat-preservation jacket I are arranged on the heat-preservation jacket I; the upper part of the sealed plate type filter cylinder body is provided with a filtrate outlet, a positive air inlet and a negative air inlet, the outside of the sealed plate type filter cylinder body is provided with a heat-preservation jacket II and a filter residue vibrating device, and the bottom of the sealed plate type filter cylinder body is provided with a residue discharge port and a filtrate inlet. The invention also comprises a method for regenerating the deteriorated molten nitrate salt. By utilizing the purification system and the regeneration method, the technical problem of purification of the deteriorated molten nitrate salt which is high in temperature, low in temperature and easy to solidify can be effectively solved, the regeneration of the molten salt can be accurately realized, the service life of the molten nitrate salt is prolonged, and the purposes of saving cost and reducing solid wastes are achieved.
Description
Technical Field
The invention relates to the technical field of using molten nitrate salt as a heat transfer and storage medium, in particular to a purification system and a regeneration method of degraded molten nitrate salt.
Background
Molten nitrate salt (which is specially referred to as nitrate-based or nitrite-based alkali metal or alkaline earth metal mixed salt) is used as a heat transfer and heat storage medium for concentrating solar power generation, chemical heat carriers (such as sulfuric acid, potassium hydroxide, sodium hydroxide and melamine production) and heat treatment heating and cooling media, and particularly, the use amount of the molten nitrate salt as the heat transfer and heat storage medium is increased sharply with the introduction of advanced heat treatment technology along with the construction of photo-thermal power generation in recent years, but the molten nitrate salt is degraded to different degrees along with the increase of the use time, so that the use performance of the molten nitrate salt is degraded, and hidden troubles are brought to the safe operation of equipment. In order to recover the service performance of the deteriorated molten nitrate salt and eliminate the hidden trouble brought to the safe operation of equipment after the deterioration, the molten nitrate salt must be purified firstly, and finally, a certain amount of new salt (regenerated salt) is added for regeneration.
In the traditional treatment technology, a simple net filter is additionally arranged in a natural sedimentation system or an operation system to remove slag, and then part of molten salt is replaced. Firstly, the impurities cannot be removed completely, even some impurities cannot be removed; secondly, the amount of the replaced molten salt is relatively large, the molten salt belongs to dangerous solid waste, and the treatment is difficult and the treatment cost is high; the common chemical filtering equipment is not improved, and can not be used for the purification treatment of high-temperature and cooling molten salt which is difficult to solidify.
The prior patent technology only provides respective methods for molten salt purification, also has the problems of incomplete impurity removal, difficult replacement of an adsorbent and the like, and does not provide a method for further regeneration treatment of the purified molten salt.
Disclosure of Invention
The invention aims to solve the technical problem of providing a specialized purification system and a regeneration method of deteriorated molten nitrate salt aiming at the problems in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a purification system for degraded molten nitrate salt comprises a molten salt submerged pump I, a stirring barrel, a closed plate filter and a compressed air heater;
the molten salt submerged pump I is installed in a salt tank and is respectively connected with a molten salt control valve I, a molten salt control valve II and a molten salt control valve IX through pipelines, and the molten salt control valve II is connected with a molten salt control valve III and a molten salt control valve VII through pipelines;
the stirring device is characterized in that a heat-insulating jacket I is arranged outside the stirring barrel, a stirrer and a molten salt submerged pump II are arranged in the stirring barrel, a filter pulp discharge port is arranged at the bottom of the stirring barrel, a heat-insulating jacket I molten salt outlet and a heat-insulating jacket I molten salt inlet are arranged on the heat-insulating jacket I, the heat-insulating jacket I molten salt outlet is respectively connected with a molten salt control valve X and a molten salt control valve XI through pipelines, the molten salt control valve X is connected with a filter aid adding port at the upper part of the stirring barrel through a pipeline, the molten salt control valve XI is connected with a salt tank through a pipeline, the heat-insulating jacket I molten salt inlet is connected with a molten salt control valve IX, and the molten salt submerged pump II is connected with the molten salt;
the closed plate filter comprises a cylinder body, wherein a filtrate outlet, a positive air inlet and a negative air inlet are arranged at the upper part of the cylinder body, a heat-insulating jacket II and a filter residue vibrating device are arranged outside the cylinder body, a slag discharge port and a molten salt inlet are arranged at the bottom of the cylinder body, the molten salt inlet is connected with a molten salt control valve III, the filtrate outlet is connected with a molten salt control valve IV, the molten salt control valve IV is connected with a molten salt control valve V and a molten salt control valve VI through pipelines, and the molten salt control valve VI is connected with a stirring barrel through a pipeline;
the outlet of the compressed air heater is respectively connected with a high-temperature compressed air control valve II, a high-temperature compressed air control valve IV and a high-temperature compressed air control valve V through a pipeline provided with a high-temperature compressed air control valve I, the high-temperature compressed air control valve II is connected with the inlet of a filter heat-insulating jacket II, the outlet of the filter heat-insulating jacket II is connected with a high-temperature compressed air control valve III, the high-temperature compressed air control valve III is connected with a water pool through a pipeline, the high-temperature compressed air control valve IV is connected with a filter positive air inlet, and the high-temperature compressed air control valve V is connected with a filter reverse air inlet.
Furthermore, a slurry filtering discharge port of the stirring barrel is arranged at the lowest point of a barrel body of the stirring barrel, a fused salt inlet of the heat-insulating jacket I is arranged at the lowest point of the heat-insulating jacket I (and is also used as a fused salt discharge port in the heat-insulating jacket during parking), and the fused salt to be treated is used for circulating heat insulation.
Further, the design pressures of the cylinder body of the closed plate type filter and the heat-insulating jacket II are respectively 0.9MPa and 0.4MPa, and are respectively subjected to hydrostatic tests of 1.0MPa and 0.5 MPa; the filter cloth is made of high silica fireproof cloth which has more stable chemical property and can be used for a long time at 900 ℃. The closed plate type filter is preheated and insulated by heated compressed air; on the basis of vibrating slag discharge, high-temperature compressed air positive and negative air inlets for filter pressing residual liquid, discharging residual liquid, assisting in discharging residues and drying filter cakes are added; the inlet and outlet of the filtrate are changed into lower inlet and upper outlet.
Furthermore, the filter aid of the closed plate filter is a filter aid with a mass ratio of perlite to activated clay of 4:1, and the use method of the filter aid adopts a method combining pre-coating and simultaneous addition.
Furthermore, the temperature of the outlet gas of the compressed air heater can be controlled between 0 and 300 ℃, and the operating pressure can be controlled between 0.05 and 0.6MPa (G). The compressed air heater can heat a common factory air source (compressed air from an air compression station) and provides an optimal air source suitable for molten salt filtration, and the control system functions of the compressed air heater comprise heater start-stop control, electric heating power control and pressure and temperature display and control; the control method is PID + controllable silicon. The compressed air heater can be selected from the existing commercial devices.
Furthermore, the horizontal installation section of the pipeline, especially the inlet and outlet mixing drum and the sealed plate filter, is tiled in the purification system, the installation slope ratio is ensured to be 5% +/-2%, the mounting height of the mixing drum is 0.5 meter +/-0.1 meter lower than the mounting height of the filtrate outlet of the sealed plate filter, and after the molten salt submerged pump stops working, all valves of the pipeline are opened, so that the molten salt can all automatically flow back to the salt tank.
Furthermore, all equipment, valves, pipelines and flanges in the purification system are made of high-temperature-resistant and corrosion-resistant 304 stainless steel, a sealing gasket is made of 304 stainless steel graphite pads, a sealing ring or a sealing strip is made of flexible graphite products, and high-temperature-resistant and corrosion-resistant safety shields are additionally arranged at the positions of the valves and the flanges.
A method for regenerating deteriorated molten nitrate salt implemented by using the purification system comprises the following steps:
step one, cooling the molten salt to a temperature range of 30-60 ℃ higher than the crystallization point temperature of the molten salt;
step two, filtering and purifying;
and step three, analyzing the components of the molten salt, and adding new salt according to the analysis.
And step three, analyzing main components of the molten salt, and accurately adding new salt once or for multiple times according to an analysis result to achieve the aim of regeneration.
The invention has the beneficial effects that:
by utilizing the system, the technical problem of purification of the deteriorated molten nitrate salt which is high in temperature, low in temperature and easy to solidify can be effectively solved, the regeneration of the molten salt can be accurately realized, the service life of the molten nitrate salt is prolonged, and the purposes of saving cost and reducing solid waste are achieved; and a set of special equipment can be manufactured and professional technical service personnel can be equipped to serve the molten nitrate salt using units so as to solve the later maintenance worries of a plurality of molten nitrate salt using units.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of a purification system for deteriorated molten nitrate salt according to the present invention;
FIG. 2 is a plot of the solubility of sodium carbonate in nitrate;
FIG. 3 is a plot of the solubility of sodium chloride in nitrate;
description of reference numerals:
1. a molten salt submerged pump I;
2. a stirring barrel, 2a, a fused salt outlet of a heat-preservation jacket I, 2b, heat-preservation jackets I and 2c, a filter aid adding port, 2d, a stirrer, 2e, fused salt submerged pumps II and 2f, a filtrate discharging port, 2g and a fused salt inlet of the heat-preservation jacket I (also used as a fused salt discharging port in the heat-preservation jacket I when the vehicle is stopped);
3. the device comprises a closed plate type filter, a 3a reverse air inlet, a 3b filtrate outlet, a 3c diaphragm pressure gauge, a 3d cover opening handle, a 3e exhaust valve, a 3f positive air inlet, a 3g heat preservation jacket II, a 3h filter residue vibrating device, a 3i slag discharge port, a 3j molten salt inlet (residual liquid outlet), a 3k filter frame, a filter screen and a filter screen, wherein the filter screen is arranged on the closed plate type filter;
4. a compressed air heater 4a, a heated gas outlet 4b, a heater shell 4c, a heating element 4d, a compressed air inlet 4e and a control cabinet;
v1, a molten salt gate valve I, V2, a molten salt gate valve II, V3, a molten salt gate valve III, V4, a molten salt gate valve IV, V5, a molten salt gate valve V, V6, a molten salt gate valve VI, V7, a molten salt gate valve VII, V8, a molten salt gate valve VIII, V9, a molten salt gate valve IX, V10, a molten salt gate valve X, V11 and a molten salt gate valve XI;
v12, high-temperature compressed air ball valves I, V13, high-temperature compressed air ball valves II, V14, high-temperature compressed air ball valves III, V15, high-temperature compressed air ball valves IV, V16 and high-temperature compressed air ball valves V.
Detailed Description
For a better understanding of the present invention, reference is made to the following examples and accompanying drawings.
Referring to fig. 1, the purification system for the degraded molten nitrate salt comprises a molten salt submerged pump I1, a stirring barrel 2, a closed plate filter 3 and a compressed air heater 4;
the molten salt submerged pump I1 is installed in an original salt tank (a cold molten salt storage tank or a molten salt tank or a quenching tank) of a molten nitrate salt using unit and is respectively connected with a molten salt gate valve I V1, a molten salt gate valve II V2 and a molten salt gate valve IX V9 through pipelines, and the molten salt gate valve II V2 is connected with a molten salt gate valve III V3 and a molten salt gate valve VII V7 through pipelines;
the stirring device is characterized in that a heat-insulating jacket I2 b is arranged outside the stirring barrel 2, a filtering and filter aid adding port 2c is arranged at the upper part of the stirring barrel 2, a stirrer 2d and a molten salt submerged pump II 2e are arranged in the stirring barrel 2, a filtered slurry discharge port 2f is arranged at the bottom of the stirring barrel 2, a heat-insulating jacket I molten salt outlet 2a and a heat-insulating jacket I molten salt inlet 2g are arranged on the heat-insulating jacket I2 b, the heat-insulating jacket I molten salt outlet 2a is respectively connected with a molten salt gate valve XV 10 and a molten salt gate valve XI V11 through pipelines, the molten salt gate valve XV 10 is connected with the filtering and filter aid adding port 2c through a pipeline, the molten salt gate valve XI V11 is connected with a salt bath through a pipeline, the heat-insulating jacket I inlet 2g is connected with a molten salt IX V9, and the molten salt submerged pump II 2e is connected; the slurry filtering discharge port 2f is arranged at the lowest point of the barrel body, the fused salt inlet 2g of the heat-insulating jacket I (which is also used as a fused salt discharge port in the heat-insulating jacket I when the barrel body is parked) is arranged at the lowest point of the heat-insulating jacket I, and the circulating heat insulation is carried out by using the fused salt to be treated;
the sealed plate filter 3 comprises a cylinder body, wherein a reverse air inlet 3a, a filtrate outlet 3b, a diaphragm pressure gauge 3c, a cover opening handle 3d, an exhaust valve 3e and a positive air inlet 3f are arranged at the upper part of the cylinder body, a heat-insulating jacket II 3g and a filter residue vibration device 3h are arranged outside the cylinder body, a filter frame 3k is arranged inside the cylinder body, a slag discharge port 3i and a molten salt inlet 3j are arranged at the bottom of the cylinder body, the molten salt inlet 3j is connected with a molten salt gate valve III V3, the filtrate outlet 3b is connected with a molten salt gate valve IV V4, the molten salt gate valve IV V4 is connected with a molten salt gate valve V5 and a molten salt gate valve VI V6 through pipelines, the molten salt gate valve VI V6 is connected with the stirring barrel 2 through pipelines, and the molten salt gate valve V5 is;
the outlet of the compressed air heater 4 is connected with a high-temperature compressed air ball valve IV 12, the high-temperature compressed air ball valve IV 12 is respectively connected with a high-temperature compressed air ball valve II V13, a high-temperature compressed air ball valve IV V15 and a high-temperature compressed air ball valve V16 through pipelines, the high-temperature compressed air ball valve II V13 is connected with an inlet of a filter heat-insulating jacket II 3g, an outlet of the filter heat-insulating jacket II 3g is connected with a high-temperature compressed air ball valve III V14, the high-temperature compressed air ball valve III V14 is connected with a water pool through a pipeline, the high-temperature compressed air ball valve IV V15 is connected with a filter positive air inlet 3f, and the high-temperature compressed air ball valve V16 is connected with a.
In the embodiment, the molten salt submerged pump I1 is used as a molten salt conveying and filtering power pump, the working pressure of a filter is required to be 0.3MPa-0.4MPa after the pressure pipe is damaged, the pump head is determined to be 55 m +/-5 m, and the flow is determined to be 20m3About/h; meanwhile, a backflow bypass is installed at an outlet, and the flow is adjusted through a fused salt gate valve IV 1。
In this embodiment, the stirring barrel 2 is used for manufacturing a simultaneous feeding filter slurry (which is used for continuously forming a new cake layer on the filter aid and impurities during the filtering process), precoating the filter slurry, and realizing precoating circulation. The molten salt submerged pump II 2e is used as a precoating filter pulp conveying pump and a precoating power pump of a filter, the working pressure of the filter needs to be 0.3MPa-0.4MPa and the precoating speed is met after the pressure pipe is damaged, the pump lift is determined to be 55 meters +/-5 meters, and the flow is determined to be 10m3The ratio of the reaction time to the reaction time is less than h. The concentration of the precoating filter pulp is 5-8%, the precoating filter pulp amount is calculated according to the filter area of each square meter and needs to use 0.7 plus or minus 0.2Kg of filter aid to prepare, the molten salt submerged pump II 2e is sent into the closed plate filter 3 to carry on the precoating circulation, until the outlet liquid of the closed plate filter is clear; the concentration of the simultaneously added filter pulp is 8-10% in the stirring barrel, the amount of the simultaneously added filter pulp is calculated according to the amount of the filter aid which is 0.05-0.1% of the weight of the molten salt in the salt tank, and after the filter pulp is prepared in the stirring barrel 2 in times, a molten salt gate valve VIII V8 at the bottom of the stirring barrel 2 is opened and placed in the salt tank.
In particular, before the deteriorated molten nitrate salt to be treated enters the purification system of the deteriorated molten nitrate salt according to the invention for treatment, the temperature of the molten salt in a salt tank must be uniformly reduced to be within a range of 30-60 degrees above the crystallization point of the molten salt. Firstly, sodium carbonate, sodium chloride and other impurities with reduced solubility along with temperature reduction in the molten salt are separated out along with temperature reduction and removed in subsequent filtration, and secondly, the purification safety is considered.
In this embodiment, the closed plate filter 3 is used for filtering molten salt, and deeply removes impurities in the molten salt. Firstly, through early pre-coating circulation, a porous filter cake layer with the thickness of 2-4mm, which is formed by a filter aid (the filter aid is a filter aid with the mass ratio of perlite to activated clay being 4:1, and the use method of the filter aid adopts a method combining pre-coating and simultaneous addition), is formed on the filter cloth, and then molten salt is formally filtered. Stopping filtering when the pressure of a diaphragm pressure gauge 3c of the filter is close to 0.4MPa and the flow of a clear liquid outlet is obviously reduced (firstly stopping the molten salt submerged pump I1 and then quickly closing the molten salt gate valve III V3); starting filter pressing and discharging residual liquid. Starting a compressed air heater 4, introducing high-temperature compressed air with the pressure of 0.4MPa and the temperature controlled below the melting point of molten salt to be filtered by more than 30 ℃ and less than 50 ℃ through a positive air inlet 3f, ensuring that the pressure of a diaphragm pressure gauge 3c of a closed plate type filter 3 is not more than 0.4MPa, filter-pressing the molten salt in the filter, drying a filter cake, stopping filter-pressing when no molten salt flows out from a filtrate outlet 3b of the filter, and stopping filter-pressing (firstly closing the compressed air heater 4, and then quickly closing a molten salt outlet valve, namely a molten salt gate valve IV V4; closing the molten salt gate valve II V2, opening the molten salt gate valve III V3 and the molten salt gate valve VII V7, and returning the residual liquid to the stirring barrel 2 (if allowed, the residual liquid can also be returned to the salt tank from the main pipeline molten salt gate valve III V3-molten salt gate valve II V2 to the molten salt gate valve I V1); and finally, carrying out slag discharging treatment. Firstly, vibrating to remove slag. Opening an exhaust valve 3e until the pressure of a filter diaphragm pressure gauge 3c is zero, opening a slag discharge port 3i, starting a filter residue vibrating device for 3h to discharge slag, and stopping until the slag does not drop obviously; and then hot compressed air is used for back flushing the filter cloth and assisting in deslagging. Closing the molten salt gate valve III V3, the high-temperature compressed air ball valve II V13 and the high-temperature compressed air ball valve IV V15, opening the high-temperature compressed air ball valve V16, introducing high-temperature compressed air with the pressure of 0.3-0.4MPa and the temperature controlled to be more than 30 ℃ and less than 50 ℃ of the melting point of molten salt to be filtered from the reverse inlet 3a, and opening and closing the high-temperature compressed air ball valve IV 12 for many times in a moment to blow slag. And (5) stopping the compressed air heater 4 after the slag discharge is finished, and closing the high-temperature compressed air ball valve V16 and the slag discharge port 3 i. Repeating the steps to perform the next round of purification.
The design pressures of the cylinder body of the closed plate type filter 3 and the heat-insulating jacket II are respectively 0.9MPa and 0.4MPa, and are respectively subjected to hydrostatic tests of 1.0MPa and 0.5 MPa; the filter cloth is made of high silica fireproof cloth which has more stable chemical property and can be used for a long time at 900 ℃; preheating and insulating by using heated compressed air; on the basis of vibrating slag discharge, high-temperature compressed air positive and negative air inlets for filter pressing residual liquid, discharging residual liquid, assisting in discharging residues and drying filter cakes are added; the inlet and outlet of the filtrate are changed into lower inlet and upper outlet.
In this embodiment, the compressed air heater 4 includes a heated air outlet 4a, a heater housing 4b, a heating element 4c, a compressed air inlet 4d, and a control cabinet 4e, wherein the heating element 4c is located in the heater housing 4b, and the heating element 4c is connected to the control cabinet 4 e. The compressed air heater 4 mainly provides high-temperature compressed air with the temperature controllable between 0 and 300 ℃ and the operating pressure controllable between 0.05 and 0.6MPa (G). The device is used for extruding residual liquid in the closed plate type filter, drying filter cakes and blowing residual filter residues inside and outside the filter cloth; and the second is used for preheating and heat preservation of the closed plate type filter. Before the sealed plate type filter 3 is filled with molten salt, the compressed air heater 4 is adjusted, the outlet pressure is controlled to be 0.1-0.2MPa (G), a high-temperature compressed air ball valve II V13 (air inlet) and a high-temperature compressed air ball valve III V14 (air outlet) of a heat-insulating jacket II 3g of the sealed plate type filter 3 are opened and adjusted, after a cylinder body of the sealed plate type filter 3 is preheated to 120 +/-10 ℃, the high-temperature compressed air ball valve II V13 and the high-temperature compressed air ball valve III V14 are closed, and the heat-insulating jacket II 3g is filled with high-temperature compressed air for heat insulation. The compressed air heater 4 can heat a common factory air source (compressed air from an air compression station) and provides an optimal air source suitable for molten salt filtration, and the control system functions of the compressed air heater comprise heater start-stop control, electric heating power control and pressure and temperature display and control; the control method is PID + controllable silicon. The compressed air heater can be selected from the existing commercial devices.
In the embodiment, the volume ratio of the stirring barrel 2 to the closed plate type filter 3 is 1:1.5, four support lugs are uniformly arranged on the peripheries of the heat-preservation jacket I2 b and the heat-preservation jacket II 3g and are arranged on a support.
In this embodiment, if the unit of use only has one salt tank, the treated clear liquid can be returned to the salt tank again, and the treatment can be repeated until the molten salt is clear.
In this embodiment, the devices, valves, pipelines, and flanges are made of high temperature resistant and corrosion resistant 304 stainless steel, the sealing gasket is made of 304 stainless steel graphite pad, and the sealing ring or sealing strip is made of flexible graphite. High-temperature resistant and corrosion resistant safety shields are additionally arranged at the positions of the valves and the flanges.
In this embodiment, the horizontal installation section of tiling pipeline among the clean system, especially business turn over agitator and airtight plate filter, the installation slope ratio is guaranteed 5% +/-2%, and the agitator is 0.5 meters + -0.1 meters lower than airtight plate filter fused salt export mounting height, and after the fused salt submerged pump stopped working, as long as open all valves of pipeline, the fused salt homoenergetic all flowed back to the salt groove by oneself.
The working process of the purification system is as follows:
1. preparation of simultaneous addition filter slurry and precoating filter slurry
Firstly, checking all valves of the system to enable all valves to be in a completely closed state; fully opening a molten salt gate valve I V1, and starting a molten salt submerged pump I1; fully opening a molten salt gate valve XI V11, and slowly opening a molten salt gate valve IX V9; then adjusting a molten salt gate valve I V1 and a molten salt gate valve IX V9, and preheating a stirring barrel 2;
manufacturing simultaneous addition filter pulp, slowly opening a molten salt gate valve XV 10, adjusting a molten salt gate valve XI V11, performing simultaneous addition filter pulp molten salt by using a stirring barrel 2, adjusting a molten salt gate valve XI V11, and closing a molten salt gate valve XV 10; starting the stirrer 2d, adding the filter aid by times from the filter aid adding port 2c, uniformly stirring, starting the molten salt gate valve VIII V8, adding the filter slurry into the salt tank, and closing the molten salt valve VIII V8;
preparing precoated filter pulp, adding the filter pulp in the same way as the preparation, and keeping the precoated filter pulp in the stirring barrel 2;
2. precoating
When the precoating filter pulp is manufactured, a compressed air heater 4 is started, and a closed plate type filter 3 is preheated; opening a molten salt gate valve IV V4, a molten salt gate valve VI V6, a molten salt gate valve II V2 and a molten salt gate valve III V3, and adjusting the molten salt gate valve I V1 and the molten salt gate valve IX V9 until molten salt flows out from an outlet of the molten salt gate valve VI V6; adjusting a molten salt gate valve I V1 and a molten salt gate valve IX V9, closing a molten salt gate valve II V2, opening a molten salt gate valve VII V7, and opening a molten salt submerged pump II 2e for pre-coating circulation until molten salt at an outlet of the molten salt gate valve VI V6 is clear; closing the molten salt submerged pump II 2e, and immediately opening the molten salt gate valve V5 and closing the molten salt gate valve VI V6 and the molten salt gate valve VII V7;
3. filtration
Immediately opening a molten salt gate valve II V2, quickly starting a molten salt submerged pump I1, adjusting a molten salt gate valve I V1 and a molten salt gate valve IX V9, and filtering molten salt;
4. and (6) removing slag.
A regeneration method of deteriorated molten nitrate salt comprises the following specific processes:
step one, cooling the molten salt to a temperature range of 30-60 ℃ higher than the crystallization point temperature of the molten salt;
the main impurities such as sodium carbonate, sodium chloride and the like are precipitated due to the fact that the solubility of the main impurities in the nitrate is reduced along with the temperature reduction (see figures 2 and 3 in detail), and are removed in the subsequent filtration and purification; the step is particularly important for concentrated solar power generation with high use temperature, chemical heat carriers and molten nitrate salt for aluminum alloy solution heat treatment;
step two, filtering and purifying;
the filtering and purifying are key steps influencing the regeneration effect of the molten salt, no matter what filtering and purifying equipment is selected, the characteristics of the molten salt must be considered, and the molten salt is purified thoroughly to the maximum extent;
analyzing the components of the molten salt, and adding new salt according to the analysis;
quantitatively detecting main components of the deteriorated molten salt by using a chemical analysis method; calculating the amount of new salt to be supplemented; adding the mixture at one time or in several times.
Application example 1(53% potassium nitrate +40% sodium nitrite +7% sodium nitrate) calculation and addition of HTS molten salt
If the (degraded) molten salt detection result is: 52.7% potassium nitrate +38% sodium nitrite +9.3% sodium nitrate (only the three major components were tested relative proportions, other impurities not considered), the molten salt weighed 20 tonnes.
The calculation method comprises the following steps: the amount of newly added salt is calculated according to the initial proportion (53 percent potassium nitrate, 40 percent nitrous acid and 7 percent sodium nitrate) of the completely recovered molten salt:
(20×52.7%+X):(20×9.3%)=53:7
x =3.54 (ton is the amount of potassium nitrate which needs to be supplemented for the X to be completely recovered to the initial proportion of the molten salt);
(20×38%+Y):(20×9.3%)=40:7
y =3.028 (ton is the amount of supplemental sodium nitrite needed to fully recover the initial proportion of molten salt).
The adding method comprises the following steps: weighing the calculated amounts of potassium nitrate and sodium nitrite which need to be supplemented as described above, uniformly mixing the potassium nitrate and the sodium nitrite as new salt to be supplemented, and verifying by experiments: can be added into the molten salt tank once, and then the complete regeneration is achieved; or can be added into the molten salt tank for multiple times, and the molten salt tank is partially regenerated firstly and then is gradually adjusted to be completely regenerated. Whether the once supplement or the multiple supplement is carried out is determined according to the volume of a molten salt operation system and the technical requirements of the process on the use of the molten salt.
Application example 2 calculation and addition of molten salt (50% Potassium nitrate +50% sodium nitrite)
If the (degraded) molten salt detection result is: 55% potassium nitrate +45% sodium nitrite, the molten salt weight is 20 tons.
The calculation method comprises the following steps: the amount of newly added salt is calculated according to the initial ratio (50% potassium nitrate +50% nitrous acid) of the completely recovered molten salt:
(20×55%):(20×45%+X)=50:50
x =2.0 (ton of sodium nitrite is added for X to completely recover the initial proportion of molten salt).
The adding method comprises the following steps: the amount of sodium nitrite to be supplemented calculated according to the above is weighed as the new salt to be supplemented, and the experiment proves that: can be added into the molten salt tank once, and then the complete regeneration is achieved; or can be added into the molten salt tank for multiple times, and the molten salt tank is partially regenerated firstly and then is gradually adjusted to be completely regenerated. Whether the once supplement or the multiple supplement is carried out is determined according to the volume of a molten salt operation system and the technical requirements of the process on the use of the molten salt.
Particularly, the added new salt raw materials (potassium nitrate, sodium nitrite, sodium nitrate and the like) should meet the technical requirements of products of international high-class products or related industries.
TABLE 1 detection results of main technical indexes before and after regeneration treatment of HTS molten salt as chemical heat carrier of a company
As can be seen from Table 1, the molten salt treated by the purification system and the regeneration method has good impurity removal effect and ideal regeneration effect.
The purification system is simultaneously suitable for the purification treatment of quenching oil.
Claims (9)
1. A purification system of deteriorated molten nitrate salt is characterized in that: the device comprises a molten salt submerged pump I, a stirring barrel, a closed plate type filter and a compressed air heater;
the molten salt submerged pump I is installed in a salt tank and is respectively connected with a molten salt control valve I, a molten salt control valve II and a molten salt control valve IX through pipelines, and the molten salt control valve II is connected with a molten salt control valve III and a molten salt control valve VII through pipelines;
the stirring device is characterized in that a heat-insulating jacket I is arranged outside the stirring barrel, a stirrer and a molten salt submerged pump II are arranged in the stirring barrel, a filter pulp discharge port is arranged at the bottom of the stirring barrel, a heat-insulating jacket I molten salt outlet and a heat-insulating jacket I molten salt inlet are arranged on the heat-insulating jacket I, the heat-insulating jacket I molten salt outlet is respectively connected with a molten salt control valve X and a molten salt control valve XI through pipelines, the molten salt control valve X is connected with a filter aid adding port at the upper part of the stirring barrel through a pipeline, the molten salt control valve XI is connected with a salt tank through a pipeline, the heat-insulating jacket I molten salt inlet is connected with a molten salt control valve IX, and the molten salt submerged pump II is connected with the molten salt;
the closed plate filter comprises a cylinder body, wherein a filtrate outlet, a positive air inlet and a negative air inlet are arranged at the upper part of the cylinder body, a heat-insulating jacket II and a filter residue vibrating device are arranged outside the cylinder body, a slag discharge port and a molten salt inlet are arranged at the bottom of the cylinder body, the molten salt inlet is connected with a molten salt control valve III, the filtrate outlet is connected with a molten salt control valve IV, the molten salt control valve IV is connected with a molten salt control valve V and a molten salt control valve VI through pipelines, and the molten salt control valve VI is connected with a stirring barrel through a pipeline;
the outlet of the compressed air heater is respectively connected with a high-temperature compressed air control valve II, a high-temperature compressed air control valve IV and a high-temperature compressed air control valve V through a pipeline provided with a high-temperature compressed air control valve I, the high-temperature compressed air control valve II is connected with the inlet of a filter heat-insulating jacket II, the outlet of the filter heat-insulating jacket II is connected with a high-temperature compressed air control valve III, the high-temperature compressed air control valve III is connected with a water pool through a pipeline, the high-temperature compressed air control valve IV is connected with a filter positive air inlet, and the high-temperature compressed air control valve V is connected with a filter reverse air inlet.
2. The purification system of deteriorated molten nitrate salt according to claim 1, characterized in that: the mixing drum is connected with a slurry filtering discharge port, a heat-preservation jacket I is connected with a molten salt inlet, a mixing drum body is connected with a mixing drum body, a mixing drum slurry filtering discharge port is arranged at the lowest point of the mixing drum body, a heat-preservation jacket I is arranged at the lowest point of the heat-preservation jacket I, and the molten salt to be treated is used.
3. The purification system of deteriorated molten nitrate salt according to claim 1 or 2, characterized in that: the design pressures of the cylinder body of the closed plate type filter and the heat-insulating jacket II are respectively 0.9MPa and 0.4MPa, and the design pressures are respectively tested by water pressure tests of 1.0MPa and 0.5 MPa; the filter cloth is made of high silica fireproof cloth which has more stable chemical property and can be used for a long time at 900 ℃; the closed plate type filter is preheated and insulated by heated compressed air; on the basis of vibrating slag discharge, high-temperature compressed air positive and negative air inlets for filter pressing residual liquid, discharging residual liquid, assisting in discharging residues and drying filter cakes are added; the inlet and outlet of the filtrate are changed into lower inlet and upper outlet.
4. The purification system of deteriorated molten nitrate salt according to claim 1 or 2, characterized in that: the filter aid of the closed plate type filter is a filter aid with a mass ratio of perlite to activated clay of 4:1, and the use method of the filter aid adopts a method combining pre-coating and simultaneous addition.
5. The purification system of deteriorated molten nitrate salt according to claim 1 or 2, characterized in that: the temperature of the outlet gas of the compressed air heater can be controlled between 0 and 300 ℃, and the operating pressure can be controlled between 0.05 and 0.6 MPa; the compressed air heater can heat a common factory air source and provide an optimal air source suitable for molten salt filtration, and the control system functions of the compressed air heater comprise heater start-stop control, electric heating power control and pressure and temperature display and control; the control method is PID + controllable silicon.
6. The purification system of deteriorated molten nitrate salt according to claim 1 or 2, characterized in that: the pipeline is laid in the purification system, the installation slope ratio is ensured to be 5% +/-2%, the installation height of the mixing drum is 0.5m +/-0.1 m lower than that of the filtrate outlet of the sealed plate filter, and after the molten salt submerged pump stops working, all valves of the pipeline are opened, so that the molten salt can flow back to the salt tank automatically.
7. The purification system of deteriorated molten nitrate salt according to claim 1 or 2, characterized in that: the purification system is characterized in that the equipment, the valves, the pipelines and the flanges are made of high-temperature-resistant and corrosion-resistant 304 stainless steel, the sealing gasket is made of 304 stainless steel graphite pads, the sealing rings or the sealing strips are made of flexible graphite products, and the valves and the flanges are additionally provided with high-temperature-resistant and corrosion-resistant safety shields.
8. A method for regenerating deteriorated molten nitrate salt, which is carried out by using the purification system according to claims 1 to 7, characterized by comprising the steps of:
step one, cooling the molten salt to a temperature range of 30-60 ℃ higher than the crystallization point temperature of the molten salt;
step two, filtering and purifying;
and step three, analyzing the components of the molten salt, and adding new salt according to the analysis.
9. The method for regenerating deteriorated molten nitrate salt according to claim 8, characterized in that: and step three, analyzing main components of the molten salt, and accurately adding new salt once or for multiple times according to the analysis result to achieve the regeneration purpose.
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Address after: No. 118, Ziwei East Road, jingjingpu Development Zone, Ningxiang City, Changsha City, Hunan Province 410600 Applicant after: Hunan Zhonghe hot salt Technology Co.,Ltd. Address before: No. 118, Ziwei East Road, jingjingpu Development Zone, Ningxiang City, Changsha City, Hunan Province 410600 Applicant before: Ningxiang nuclear industry heat treatment materials Co.,Ltd. |
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