A salt water chiller system for producing persulfate

Abstract

The present application relates to salt water refrigeration unit technical field, specifically to a kind of salt water refrigeration unit system for producing persulfate, including dynamic control module;Dynamic control module obtains real-time brine concentration, brine inlet temperature;According to the critical temperature of salt precipitation occurrence calculated according to real-time brine concentration, according to the heat load and critical temperature of persulfate production device calculates safety threshold, according to heat load and safety threshold calculates optimal flow rate, according to safety threshold, optimal flow rate controls the operation of salt water refrigeration unit system;The present application is through accurate calculation of the critical temperature of salt precipitation of brine under current concentration, provides accurate threshold for subsequent salt precipitation early warning, again into heat load dynamic correction safety threshold, realizes linkage determination, and then according to actual load control brine preparation module output temperature;Again in combination with load deduce optimal flow rate, ensure optimal flow rate in the case of avoiding salt precipitation, reduce the waste of power.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of salt water refrigerating unit systems, in particular to a salt water refrigerating unit system for producing persulfate. BACKGROUND

[0002] The production of persulfate (such as ammonium persulfate and sodium persulfate) is mostly carried out by electrolysis or oxidation, and the system temperature needs to be strictly controlled at-5-0 DEG C in the reaction process, so as to inhibit the side reactions (such as decomposition of persulfate and hydrolysis reaction under acidic conditions) and improve the yield of target products. As a core temperature control equipment, the salt water refrigerating unit system realizes indirect heat exchange and temperature control by passing the cooled calcium chloride / magnesium chloride brine, and the heat exchange efficiency, stability and anti-salting ability of the brine directly determine the production continuity.

[0003] The existing system adopts fixed-concentration (25%-30% calcium chloride) brine, but in fact, due to the problems of precipitation and brine leakage, the actual concentration of the flowing brine is not fixed but in a floating state; when the local temperature is lower than the freezing point of the brine (about-25 DEG C) in the refrigeration process, solid salt is easy to precipitate and adhere to the inner wall of the heat exchange pipe (the thickness can reach 2-3 mm), which leads to the decrease of the heat exchange coefficient and affects the finished product quality of the persulfate; and the acid washing needs to be stopped every month, which leads to the increase of cost.

[0004] Therefore, there is a need for a salt water refrigerating unit system for producing persulfate, which can avoid the precipitation of solid salt and thus avoid the decrease of the heat transfer coefficient and prolong the acid washing period. SUMMARY

[0005] The technical problem to be solved by the application is to provide a salt water refrigerating unit system for producing persulfate, which can avoid the precipitation of solid salt and thus avoid the decrease of the heat transfer coefficient and prolong the acid washing period.

[0006] In order to solve the above technical problems, the technical scheme adopted by the application is as follows:

[0007] A salt water refrigerating unit system for producing persulfate is used for cooling a persulfate production device, and the persulfate production device comprises a cooling inlet and a cooling outlet; the salt water refrigerating unit system comprises a brine preparation module and a heat exchange module; the brine preparation module comprises a brine inlet and a brine outlet; the heat exchange module comprises a heat exchange pipe and a circulating pump; the brine outlet is communicated with the cooling inlet through the heat exchange pipe, the cooling outlet is communicated with the brine inlet to form a circulation, and the circulating pump is arranged on the heat exchange pipe.

[0008] The salt water refrigerating unit system further comprises a dynamic control module.

[0009] The brine preparation module comprises a concentration sensor, through which the real-time brine concentration C is obtained; the brine inlet is provided with a temperature sensor to obtain the brine inlet temperature ;

[0010] The dynamic control module calculates the critical temperature of salting-out according to the real-time brine concentration C , = × + ×C+ ; calculates the salting-out safety threshold , =min , and ≤ , when Q=0, = ; calculates the optimal flow rate , = , wherein , , is a coefficient; T is a basic safety margin and is a positive value, Q is the heat load of the persulfate production device, is the optimal working temperature of the persulfate production device, is the minimum heat exchange difference; is the brine density, is the specific heat capacity of brine, is the flow area of the heat exchange tube;

[0011] The dynamic control module controls the temperature output from the brine outlet of the brine preparation module according to , and dynamically controls the rotating speed of the circulating pump according to .

[0012] Preferably, a heat load curve of the persulfate production device during production is established, the x-axis of the heat load curve is time, and the y-axis is the heat load Q;

[0013] After the dynamic control module is time-aligned with the heat load curve, the heat load Q on the x-axis is delayed by a predetermined time t as the input of , .

[0014] Preferably, the calculation formula of the t is: t= ; wherein L is the length of the heat exchange tube.

[0015] Preferably, the t is a fixed value.

[0016] Preferably, the specific heat capacity of the brine and the brine density According to the C table lookup.

[0017] Preferably, when Q = 0, the optimal flow rate According to the preset value.

[0018] Preferably, before the concentration sensor first acquires the real-time brine concentration C, the circulating pump works for a predetermined time.

[0019] Preferably, if the concentration sensor acquires the real-time brine concentration C lower than the preset minimum concentration, the dynamic control module prohibits the brine preparation module from starting.

[0020] Preferably, the -3℃; the 6℃.

[0021] The beneficial effects of the present application are: by accurately calculating the salting-out critical temperature of the brine at the current concentration, overcoming the rough cognition of the prior art that fixed concentration corresponds to fixed freezing point, providing an accurate threshold for subsequent salting-out warning, and then integrating the dynamic correction safety threshold of the heat load, realizing linkage determination, and then controlling the output temperature of the brine preparation module according to the actual load, avoiding the problems of brine preparation module salting-out, freezing and blocking, and insufficient output temperature, while ensuring the operation, safety and meeting the heat load requirements of the brine preparation module; Finally, in combination with the load, the optimal flow rate is derived to ensure the optimal flow rate and reduce power waste while avoiding salting-out; The basic safety margin is positive, which ensures that the system does not salt out at all, even if the load is very low, but it is close to the critical temperature without salting-out; Through the dynamic control module, the power of the brine preparation module and the power of the circulating pump are adjusted according to the real-time brine density and heat load to ensure that there is no salting-out and meet the production requirements, so as to meet the energy-saving, avoid the decrease of the thermal conductivity coefficient and prolong the pickling cycle of the brine freezing unit system; That is, the unity of salting-out safety, load matching, energy consumption optimization and pickling cycle. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structure diagram of a brine freezing unit system for producing persulfate according to an embodiment of the present application.

[0023] Figure 2 It is a heat load curve diagram of a persulfate production device of a brine freezing unit system for producing persulfate according to an embodiment of the present application.

[0024] Label explanation: 1, persulfate production device; 11, cooling inlet; 12, cooling outlet; 2, brine chiller unit system; 21, brine preparation module; 211, brine inlet; 212, brine outlet; 213, concentration sensor; 214, temperature sensor; 22, heat exchange module; 221, heat exchange pipe; 222, circulating pump; 23, dynamic control module. DETAILED DESCRIPTION

[0025] To illustrate the technical content of the present application, the purposes and effects achieved are described below in conjunction with the embodiments and the accompanying drawings.

[0026] Please refer to Figure 1 and Figure 2 A brine chiller unit system 2 for persulfate production is used for cooling of a persulfate production device 1, the persulfate production device 1 comprising a cooling inlet 11 and a cooling outlet 12; the brine chiller unit system 2 comprises a brine preparation module 21 and a heat exchange module 22; the brine preparation module 21 comprises a brine inlet 211 and a brine outlet 212; the heat exchange module 22 comprises a heat exchange pipe 221 and a circulating pump 222; the brine outlet 212 is communicated with the cooling inlet 11 through the heat exchange pipe 221, the cooling outlet 12 is communicated with the brine inlet 211 to form a circulation, and the circulating pump 222 is arranged on the heat exchange pipe 221;

[0027] The brine chiller unit system 2 further comprises a dynamic control module 23;

[0028] The brine preparation module 21 comprises a concentration sensor 213, which obtains real-time brine concentration C through the concentration sensor; the brine inlet 211 is provided with a temperature sensor 214 to obtain the temperature of the brine inlet 211 ;

[0029] The dynamic control module calculates the critical temperature of salting-out according to the real-time brine concentration C , = × + ×C+ ; calculates the salting-out safety threshold , =min , and ≤ , when Q=0, = ; calculates the optimal flow rate , = , wherein , , is the coefficient; T is the basic safety margin and is positive, Q is the heat load of the persulfate production device, is the optimal working temperature of the persulfate production device, is the minimum heat exchange difference; is the brine density, is the specific heat capacity of the brine, is the flow area of the heat exchange tube;

[0030] The dynamic control module 23 controls the temperature of the brine preparation module 21 output from the brine outlet 212 according to The dynamic control module 23 controls the temperature of the brine preparation module 21 output from the brine outlet 212 according to The dynamic control module 23 dynamically controls the rotating speed of the circulating pump 222.

[0031] As can be seen from the above description, by accurately calculating the salting-out critical temperature of the brine at the current concentration, the fixed concentration corresponding to the fixed freezing point in the prior art is overcome, and an accurate threshold is provided for subsequent salting-out warning. Then, the heat load dynamic correction safety threshold is integrated to realize linkage determination. Then, according to the actual load, the output temperature of the brine preparation module 21 is controlled to avoid the problems of brine preparation module 21 precipitation, freezing blockage, and insufficient low output temperature, while ensuring the operation, safety and meeting the heat load requirements of the brine preparation module 21. Finally, the optimal flow rate is derived in combination with the load to ensure the optimal flow rate and reduce power waste under the condition of avoiding salting-out. The basic safety margin is positive, which ensures that the system does not precipitate absolutely, even if the load is very low, but it is close to the critical temperature without salting-out. Through the dynamic control module 23, the power of the brine preparation module 21 and the circulating pump 222 are adjusted to meet the energy saving, avoid the decrease of the heat transfer coefficient, and prolong the pickling cycle of the brine freezing unit system 2 under the condition of ensuring no salting-out and meeting the production requirements. That is, the unity of salting-out safety, load matching, energy consumption optimization, and pickling cycle.

[0032] Further, the heat load curve of the persulfate production device 1 during production is established, the x-axis of the heat load curve is time, and the y-axis is the heat load Q;

[0033] After the dynamic control module 23 is aligned with the time of the heat load curve, the heat load Q on the x-axis is delayed by a predetermined time t as the input of , .

[0034] As can be seen from the above description, by using the heat load Q delayed by a predetermined time as the input of , , since it takes time for the heat exchange tube to transport cold brine to the persulfate production device, it has a lag, and then the Q delayed by a predetermined time is used as the current input, so that the temperature when the cold brine arrives is optimally matched with the power Q.

[0035] Further, the salt water specific heat capacity The calculation formula of t is: t= ; wherein L is the length of the heat exchange pipe.

[0036] Further, the salt water specific heat capacity t is a fixed value.

[0037] From the above description, by adopting a fixed value, for example, in the case of a relatively short heat exchange pipe, increasing additional variables will lead to an increase in system control difficulty, which is not worth the cost.

[0038] Further, the salt water specific heat capacity and the salt water density are obtained according to the C table.

[0039] From the above description, according to the table formed by the relationship of the real-time salt water concentration C, the salt water density , and the salt water specific heat capacity calibrated by the manufacturer, there is no need to calculate additionally, which ensures accuracy.

[0040] Further, when Q=0, the optimal flow rate is set according to the preset value.

[0041] From the above description, when Q=0, it may be in a just started state or a stopped state, i.e., the persulfate production device is in a stopped state, but the circulating pump cannot be immediately stopped, because even if the salt water preparation module is stopped, the inside may still be in a relatively low temperature condition, and if the circulating pump is immediately stopped, salt precipitation may occur, so the circulating pump needs to be continuously operated for a period of time before it can be stopped to avoid salt precipitation in the salt water preparation module.

[0042] Further, before the concentration sensor 213 initially acquires the real-time salt water concentration C, the circulating pump 222 operates according to a predetermined time.

[0043] From the above description, since the salt water may be stratified for a long time, in order to avoid stratification of the salt water leading to inaccurate detection of C, which in turn leads to large fluctuations in other values, the salt water concentration is further circulated to make the salt water concentration more uniform.

[0044] Further, if the concentration sensor 213 acquires a real-time salt water concentration C lower than a preset minimum concentration, the dynamic control module 23 prohibits the salt water preparation module 21 from starting.

[0045] From the above description, since the real-time salt water concentration C is lower than the preset minimum concentration, i.e., the salt water preparation module 21 is easily frozen and expanded, which easily leads to damage to the salt water preparation module 21, pipe rupture, and other problems.

[0046] Further, the salt water refrigeration unit system 2 of the present application is characterized in that The temperature of the salt water is -3℃; the temperature of the reaction system is -5~0℃, which is the intermediate value of the process requirement, and takes into account the reaction efficiency and the inhibition of side reactions, and provides a reference for the calculation of heat transfer temperature difference. The temperature of the salt water is 6℃.

[0047] From the above description, it can be seen that by The temperature of the salt water is -3℃, which is the intermediate value of -5~0℃ of the process requirement, and takes into account the reaction efficiency and the inhibition of side reactions, and provides a reference for the calculation of heat transfer temperature difference. The value of 6℃ ensures effective heat transfer between the salt water and the reaction system.

[0048] Example one

[0049] A salt water refrigeration unit system 2 for a persulfate production device 1, for cooling the persulfate production device 1, the persulfate production device 1 comprising a cooling inlet 11 and a cooling outlet 12; the salt water refrigeration unit system 2 comprising a salt water preparation module 21 and a heat exchange module 22; the salt water preparation module 21 comprising a salt water inlet 211 and a salt water outlet 212; the heat exchange module 22 comprising a heat exchange pipe 221 and a circulating pump 222; the salt water outlet 212 being in communication with the cooling inlet 11 through the heat exchange pipe 221, the cooling outlet 12 being in communication with the salt water inlet 211 to form a circulation, and the circulating pump 222 being arranged on the heat exchange pipe 221;

[0050] The salt water refrigeration unit system 2 further comprises a dynamic control module 23;

[0051] The salt water preparation module 21 comprises a concentration sensor 213 for obtaining the real-time salt water concentration C; the salt water inlet 211 is provided with a temperature sensor 214 for obtaining the temperature of the salt water inlet 211 ;

[0052] The dynamic control module 23 calculates the critical temperature of salting-out according to the real-time salt water concentration C ,

[0053] = × + ×C+ ;

[0054] Wherein, 、 、 , 、 、 are respectively: 0.008, -0.76, -0.52;

[0055] The salt water refrigeration unit system 2 further comprises a dynamic control module 23; ,

[0056] = min , and ≤ when Q = 0, = ;

[0057] wherein, T is a basic safety margin and is positive, Q is a heat load of the persulfate production device, T is a basic safety margin and is positive, Q is a heat load of the persulfate production device, is a minimum heat exchange difference (set to 6℃); by taking the minimum of the two values, it can be ensured that the cold quantity is within an appropriate range, T is positive to avoid excessive low temperature of the equipment leading to salting out, and ensure sufficient cold quantity to maintain the progress of the persulfate production device reaction;

[0058] Calculate the optimal flow rate ,

[0059] = ,

[0060] wherein, is the density of the brine, is the specific heat capacity of the brine, is the flow area of the heat exchange tube;

[0061] The dynamic control module 23 controls the temperature output from the brine outlet 212 of the brine preparation module 21 according to , and dynamically controls the rotation speed of the circulating pump 222 according to .

[0062] A heat load curve of the persulfate production device 1 during production is established, the x-axis of the heat load curve is time, and the y-axis is the heat load Q;

[0063] After the dynamic control module 23 is aligned with the time of the heat load curve, the heat load Q on the x-axis is delayed by a predetermined time t as the input of , .

[0064] The calculation formula of the t is: t= ; wherein, L is the length of the heat exchange tube.

[0065] The brine specific heat capacity and the brine density are obtained according to the C table.

[0066] Optimal flow rate when Q = 0 According to the preset value.

[0067] Before the concentration sensor 213 acquires the real-time brine concentration C for the first time, the circulating pump 222 works for a predetermined time.

[0068] If the concentration sensor 213 acquires the real-time brine concentration C lower than the preset minimum concentration, the dynamic control module 23 prohibits the brine preparation module 21 from starting.

[0069] The brine used by the brine preparation module 21 is calcium chloride brine, which meets the industrial grade GB / T 26520-2011, has a purity of 94%, and has an applicable concentration range of 20-30%;

[0070] For example:

[0071] The measured C is 26%, and the table ρ = 1259 kg / m³, = 3.68 kJ / (kg·℃); The measured temperature is 5℃; the persulfate production device load Q = 100 kW (low load); and the heat exchange tube length L = 200 m; T = 3℃; = 0.00196 m²;

[0072] = 0.008 × 26²- 0.76 × 26- 0.52 ≈ -14.9℃;

[0073] = min[-14.9 + 3 × (1 + 100 / 100), -3-6] = [-14.9 + 6, -9] = -9℃;

[0074] = 100 / (1259 × 3.68 × 0.00196 × (5 - (-9))) ≈ 0.787 m / s;

[0075] t = 200 / 0.787 = 254.1 s.

[0076] When the persulfate production device load Q = 500 kW (high load); and other parameters remain unchanged.

[0077] = 0.008 × 26²- 0.76 × 26- 0.52 ≈ -14.9℃;

[0078] =min[-14.9+3×(1+100 / 500),-3-6]=[-14.9+3.6,-9]=-11.3℃;

[0079] =500 / (1259×3.68×0.00196×(5 - (-11.3)))≈3.38m / s;

[0080] t = 200 / 2.97 = 59.17 s.

[0081] When the measured C is 25.8%, according to the table, ρ = 1210 kg / m³. =3.69 kJ / (kg·℃); The temperature was measured at 6℃; the load of the persulfate production unit was Q = 600kW (the load continued to increase); other parameters remained unchanged.

[0082] =0.008×25.8²-0.76×25.8-0.52≈-14.8℃;

[0083] =min[-14.8+3×(1+100 / 600),-3-6]=[-14.8+3.5,-9]=-11.3℃;

[0084] =600 / (1259×3.68×0.00196×(6 - (-11.3)))≈3.82m / s;

[0085] t = 200 / 3.82 = 52.35s.

[0086] Example 2

[0087] A brine refrigeration unit system for persulfate production, which is the same as in Example 1 and will not be described again, wherein, the... t is a fixed value that can be determined based on the actual heat exchanger tube length and the most commonly used optimal flow rate. For example, if the heat exchanger tube length L is 200m and the most commonly used optimal flow rate is 4m / s, t is set to 50s; or the heat exchange tube length L is 120m, and the most commonly used optimal flow rate is 2m / s. t is set to 60s; that is, adjust according to the actual scenario. The above values ​​are for illustrative purposes only.

[0088] The above merely illustrates the embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent transformation or direct or indirect application in the related technical field based on the content of the present application specification and drawings is also included in the patent protection scope of the present application.

Claims

1. A brine chiller system for persulfate production, used for cooling a persulfate production unit, the persulfate production unit including a cooling inlet and a cooling outlet; the brine chiller system includes a brine preparation module and a heat exchange module; the brine preparation module includes a brine inlet and a brine outlet; the heat exchange module includes heat exchange tubes and a circulating pump; the brine outlet is connected to the cooling inlet through the heat exchange tubes, the cooling outlet is connected to the brine inlet to form a circulation, and the circulating pump is mounted on the heat exchange tubes; characterized in that, The brine chiller system also includes a dynamic control module; The brine preparation module includes a concentration sensor to obtain the real-time brine concentration C; a temperature sensor is installed at the brine inlet to obtain the brine inlet temperature. ; The dynamic control module calculates the critical temperature for salt precipitation based on the real-time brine concentration C. , = × + ×C+ ; Calculate the salting-out safety threshold , =min ,and ≤ When Q=0, = ; Calculate the optimal flow velocity , = ,in, , , For coefficients; T is the basic safety margin and is a positive value, and Q is the heat load of the persulfate production unit. The optimal operating temperature for persulfate production equipment. Minimum heat transfer difference; The density of the salt water is... The specific heat capacity of salt water, This refers to the cross-sectional area of ​​the heat exchange tubes. The dynamic control module according to The temperature of the brine output from the brine outlet of the brine preparation module is controlled according to... Dynamically control the speed of the circulating pump.

2. The brine refrigeration unit system for persulfate production according to claim 1, characterized in that, Establish the heat load curve for the persulfate production unit during production. The x-axis of the heat load curve represents time, and the y-axis represents the heat load Q. After aligning the dynamic control module with the heat load curve, it will delay the x-axis by a predetermined time. The heat load Q of t is used as and Input.

3. The brine refrigeration unit system for persulfate production according to claim 2, characterized in that, The t is a fixed value.

4. The brine refrigeration unit system for persulfate production according to claim 1, characterized in that, The specific heat capacity of the brine and salt water density Obtained by looking up the table in C.

5. The brine refrigeration unit system for persulfate production according to claim 1, characterized in that, When Q=0, the optimal flow rate Set according to the preset values.

6. The brine refrigeration unit system for persulfate production according to claim 1, characterized in that, If the concentration sensor detects a real-time saline concentration C that is lower than the preset minimum concentration, the dynamic control module will prevent the saline preparation module from starting.

7. The brine refrigeration unit system for persulfate production according to claim 1, characterized in that, The -3℃; the The temperature is 6℃.

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