Method for calculating descaling efficiency of industrial circulating cooling water electrochemical equipment

Abstract

The invention discloses a method for calculating the electrochemical descaling efficiency of industrial circulating cooling water. Comprising a method for calculating the amount of CaCO3 in the circulating cooling water removed by the electrochemical treatment equipment in unit time, a method for calculating the specific energy consumption of the electric quantity consumed by the electrochemical treatment equipment for removing the unit mass of CaCO3 in the circulating cooling water, and a method for calculating the change of the hardness of the circulating cooling water along with time after the electrochemical treatment equipment is applied. According to the method, basic data and energy consumption of calcium carbonate removal capacity can be provided in the design process of the electrochemical treatment equipment, and the treatment capacity and the configuration number of the electrochemical treatment equipment can be reasonably configured in the descaling engineering project of the industrial circulating cooling water system applied to the electrochemical treatment equipment; and the water quality of the treated circulating cooling water can meet the requirements of users.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical treatment of industrial circulating cooling water, and in particular to a method for calculating the descaling efficiency of electrochemical equipment for industrial circulating cooling water. Background Art

[0002] At present, the industrial circulating cooling water system in the domestic industrial field mainly adopts the traditional process technology of using chemicals to prevent scaling, sterilization and algae removal, so as to prevent the scaling factors (calcium carbonate CaCO3 and magnesium hydroxide Mg(OH)2) in the circulating cooling water from scaling on the surface of pipes and other heat exchange equipment such as heat exchangers, thereby affecting the heat exchange efficiency, thereby affecting the product quality and output of the main process flow, and increasing energy consumption. After the electrochemical technology is adopted, the dosage of the chemical added to the circulating cooling water can be stopped or reduced, and the concentration multiple of the circulating cooling water can also be increased. The use of electrochemical technology to deal with scaling, scale inhibition, sterilization and algae removal in circulating cooling water is a new treatment technology developed in the past decade. At present, the descaling, scale inhibition, sterilization and algae removal of electrochemical treatment equipment in industrial circulating cooling water has been understood and recognized by more and more users. However, there is no method to calculate how much scaling factor (calcium carbonate CaCO3) in circulating cooling water can be removed by relevant electrochemical treatment equipment per unit time, a method to calculate the specific energy consumption of the electricity consumed by electrochemical treatment equipment for descaling, and a method to calculate the change in hardness over time in circulating cooling water after using electrochemical treatment equipment. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for calculating the descaling efficiency of electrochemical equipment for industrial circulating cooling water, so as to provide basic data and energy consumption of calcium carbonate removal capacity in the design process of electrochemical treatment equipment, and to reasonably configure the processing capacity and configuration quantity of electrochemical treatment equipment when the electrochemical treatment equipment is applied to the descaling project of industrial circulating cooling water system, so as to ensure that the water quality of the treated circulating cooling water can meet the requirements of users.

[0004] Technical solution: A method for calculating the electrochemical descaling efficiency of industrial circulating cooling water, including a method for calculating the mass of CaCO3 in circulating cooling water removed by the electrochemical treatment equipment per unit time, a method for calculating the specific energy consumption of the electricity consumed by the electrochemical treatment equipment to remove the unit mass of CaCO3 in circulating cooling water, and a method for calculating the change in hardness over time in circulating cooling water after the electrochemical treatment equipment is applied;

[0005] According to the deposition of CaCO3 generated by the electrochemical reaction on the cathode plate surface, and considering the influence of the circulating cooling water quality conditions and the structural characteristics of the electrochemical treatment equipment itself in actual operation, the deposition amount of CaCO3 generated by the electrochemical treatment equipment on the cathode surface per unit time is deduced. The deposition amount is the mass of CaCO3 removed by the electrochemical treatment equipment per unit time;

[0006] According to the double-sided area of ​​the anode plate of the electrochemical treatment equipment, the distance between the anode and cathode plates, the current density of the anode plate of the electrochemical treatment equipment, and the conductivity of the circulating cooling water, the power consumed between the anode and cathode plates is calculated, and the specific energy consumption of the electrochemical treatment equipment is derived;

[0007] The hardness of the circulating water after the nth hour is derived based on the increase in hardness per unit hour caused by the water replenishment during the operation of the electrochemical equipment, the decrease rate of hardness per unit hour caused by the heat loss from wind and the sewage discharge, the decrease rate of hardness of the initial hardness of the circulating cooling water, and the decrease in hardness per unit hour removed by the electrochemical treatment equipment.

[0008] Furthermore, the deposition amount is the mass flow rate Fc per second of CaCO3 crystallized and deposited on the cathode plate as shown in the following formula:

[0009] Fc=ACE*CE*J*S*100*1.0364×10 -5 =ACE*CE*J*S*1.0364×10 -3 (g / s)

[0010] In the formula, Fc-- is the mass flow rate per second;

[0011] ACE--average current efficiency, indicating the number of electrons generated by the actual current converted into OH - The effective conversion rate of ion number, in %;

[0012] CE--Crystallization efficiency, indicating the CO3 produced by the actual electrochemical reaction 2- With Ca 2+ The crystallization efficiency of ions combining between the positive and negative plates of the electrochemical treatment equipment and crystallizing and precipitating on the cathode plate, in %;

[0013] J---current density of the anode plate of the electrochemical treatment equipment, unit is A / cm 2 ;

[0014] S---is the double-sided area of ​​the anode plate of the electrochemical treatment equipment, in cm 2 ;

[0015] Furthermore, ACE is related to the characteristics of the anode and cathode plates and the quality of the circulating cooling water; CE is related to the spacing between the anode and cathode plates of the electrochemical treatment equipment, the flow rate of the circulating water between the plates, the equipment structure, and the structure of the cathode plate.

[0016] ACE = actual hydrogen volume flow / theoretical hydrogen volume flow

[0017] CE = actual deposition amount on the cathode plate / theoretical CaCO3 mass flow rate.

[0018] Furthermore, the calculation formula for the power consumed between the anode and cathode plates is:

[0019] P=I 2 *R / 1000=S 2 *J 2 *1000000*L / ((σ*S)*1000)=1000*S*J 2 *L / σ

[0020] The calculation formula of specific energy consumption EER of electrochemical treatment equipment is as follows:

[0021] EER = [1000*S*J 2 *L / σ] / [3600*(ACE*CE*J*S*1.0364×10 -3 ) / 1000]

[0022] =2.6802*10 5 *J*L / [σ*ACE*CE]

[0023] In the formula, P is the power consumed between the anode and cathode plates, in kW; EER is the specific energy consumption, in kW.h / kg, which means the amount of electricity consumed to remove 1 kg of CaCO3; S is the double-sided area of ​​the anode plate of the electrochemical treatment equipment, in cm 2 ; L is the distance between the anode and cathode plates, in cm; J is the current density of the anode plate of the electrochemical treatment equipment, in A / cm 2 ; σ is the conductivity of circulating cooling water, unit is us / cm.

[0024] Furthermore, the calculation formula of the change of hardness over time is obtained by the hardness of the circulating water after the nth hour;

[0025] The formula for calculating the hardness of circulating water after the nth hour is:

[0026] Yzn=Y0*a n +[(1-a n ) / (1-a)]*b

[0027] a=(1-Kwb)

[0028] b=(Ym1-Yx)

[0029] Ym1=Qm*Ym / Q1

[0030] Kwb=Ywb / Y0

[0031] Ywb=(Qw+Qb)*Y0 / Q1

[0032] Yx=Fc / (1000*Q1)

[0033] Where, Yzn is the change in hardness of circulating water after the nth hour; Qm is the amount of replenished water, unit is m 3 / h; Ym is the hardness of the make-up water, in mg / L; Q1 is the amount of water in the circulating cooling water system, in m 3 ; Ym1 is the increase in hardness per unit hour caused by the water replenishment volume Qm; Y0 is the initial hardness in the circulating water pool, in mg / L; Qb is the amount of sewage discharged, in m 3 / h; Qw is the wind heat loss, unit is m 3 / h; Ywb is the hardness reduction per unit hour carried away by the wind heat loss Qw and the sewage discharge Qb; Kwb is the hardness reduction rate relative to the initial hardness of the circulating cooling water in the circulating water pool; Yx is the hardness reduction per unit hour removed by the electrochemical treatment equipment.

[0034] Compared with the prior art, the present invention has the following significant effects:

[0035] 1. The present invention provides a method for calculating the mass of calcium carbonate (CaCO3) removed from circulating cooling water by an electrochemical treatment device per unit time, which can provide basic design data on the ability of the device to remove calcium carbonate during the design process of the electrochemical treatment device, so as to determine the size structure of the device and the number and area of ​​the anode and cathode plates to be used when designing the treatment capacity of the electrochemical treatment device, as well as the power of the DC constant voltage and constant current power supply to provide the required current density;

[0036] 2. According to the method for calculating the specific energy consumption of the electrochemical treatment equipment for descaling provided by the present invention, the amount of electricity consumed by the designed electrochemical equipment in the actual circulating cooling water descaling application can be understood; according to the method for calculating the change in hardness over time in the circulating cooling water after the application of the electrochemical treatment equipment, the processing capacity and configuration quantity of the electrochemical treatment equipment can be reasonably configured when the electrochemical treatment equipment is used in the descaling project of the industrial circulating cooling water system to ensure that the quality of the treated circulating cooling water can meet the user's requirements. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific implementation modes.

[0038] The present invention provides a method for calculating the electrochemical descaling efficiency of industrial circulating cooling water, including a method for calculating the mass of calcium carbonate (CaCO3) in circulating cooling water removed by an electrochemical treatment device per unit time, a method for calculating the specific energy consumption of the amount of electricity consumed by the electrochemical treatment device to remove a unit mass of calcium carbonate (CaCO3) in circulating cooling water, and a method for calculating the change in hardness over time in circulating cooling water after the electrochemical treatment device is applied, so as to achieve the purpose of evaluating the descaling efficiency of industrial circulating cooling water after the electrochemical device is applied.

[0039] (I) A method for calculating the mass of calcium carbonate (CaCO3) removed from circulating cooling water by an electrochemical treatment device per unit time. The derivation steps are as follows:

[0040] First of all, the electrochemical treatment equipment for industrial circulating cooling water essentially uses an electric field of a certain intensity to cause various ions and polar substances to undergo various changes in the electric field. Current research and field applications believe that there are two main mechanisms for electrochemical scale inhibition. One is a physical mechanism. From the principle of thermodynamics, water molecules tend to be in a stable state with lower energy. The other is a chemical principle, namely the electrolysis principle, which uses electrolysis to produce an alkaline area at the cathode to provide the required ions for the precipitation of calcium ions, thereby achieving the purpose of descaling, depositing scale on the surface of the cathode plate, and reducing the deposition of scale in pipes and heat exchangers.

[0041] The electrochemical reactions occurring in the anode and cathode plate areas of the electrochemical treatment equipment are as follows:

[0042] 1) Electrochemical reaction in the cathode region

[0043] Under the condition of external power supply voltage, the circulating water electrochemical treatment equipment undergoes electrolysis reaction and consumes dissolved oxygen, which will produce a large amount of OH on the surface of the cathode. - , these OH - It is mainly generated by the following two reactions:

[0044] 2H2O+O2+4e-->4OH - (1-1)

[0045] 2H2O+2e-->H2+2OH - (1-2)

[0046] These reactions produce OH - A layer of alkaline area is formed on the surface of the cathode, and the HCO3 in the solution - With OH - The reaction produces CO3 2- The reaction equation is as follows:

[0047] HCO 3- +OH - -->CO3 2- +H2O (1-3)

[0048] CO3 generated 2- With critical supersaturation Ca 2+ The reaction generates CaCO3 precipitation. The generated CaCO3 will be deposited on the surface of the cathode, thereby removing the scaling factor in the circulating cooling water and reducing the hardness of the circulating cooling water.

[0049] CO3 2- +Ca 2+ -->CaCO3 (1-4)

[0050] 2) Electrochemical reaction in the anode area

[0051] At the same time, the CL in the circulating cooling water - The OH produced by electrolysis will produce some active free radicals at the anode, such as hydroxyl radical -OH, hypochlorite radical ClO - , peroxide H2O2 and other substances.

[0052] Cl - and OH - The electrochemical reaction at the anode is as follows:

[0053] 4OH - -4e - -->O2+2H2O (1-5)

[0054] 2Cl - --->C2+2e (1-6)

[0055] Cl2+H2O-->HCl+HClO (1-7)

[0056] These substances are highly oxidizing and permeable, and can cause cell lysis and death, so they can play a good role in removing algae and sterilizing.

[0057] The electrochemical treatment equipment produces CaCO3 through electrochemical reaction, which is deposited on the cathode plate surface, thereby reducing the hardness of the circulating cooling water. The amount of CaCO3 deposited on the cathode surface per unit time produced by the electrochemical treatment equipment can be derived by the following calculation method:

[0058] According to Coulomb's definition: if a wire carries a steady current of 1 ampere, the amount of electricity passing through the cross-section of the wire in 1 second is 1 coulomb.

[0059] The negative charge of an electron is e = 1.602176634 × 10 -19Coulomb, that is, 1 Coulomb is equivalent to 6.24150974×10 18 The total amount of charge carried by an electron.

[0060] From the above definition, it can be seen that if a current of 1 ampere passes through 1 cm 2 The electron velocity of the area is 6.24150974×10 18 (pieces / s);

[0061] According to reaction equation (1-1), one electron can generate one OH - ions, and from reaction equations (1-3) and (1-4) we can know that 1 OH - ions can produce 1 CaCO3 (calcium carbonate) molecule, which means that theoretically there are 6.24150974×10 18 (pcs / s) electrons participate in the reaction to produce CaCO3 molecules, so the number of CaCO3 molecules should be 6.24150974×10 18 (pieces / s).

[0062] According to the resolution adopted by the General Conference on Weights and Measures, 1 mole will be defined as "containing exactly 6.02214076×10 23 The amount of substance in a system of basic units such as atoms or molecules", also defined as Avogadro's constant (NA).

[0063] 1cm 2 The number of moles of CaCO3 produced by the cathode and cathode plates of the electrochemical treatment equipment at a current density of 1 ampere is:

[0064] Number of moles of CaCO3 = number of CaCO3 molecules / number of moles = 6.24150974 × 10 18 (pieces / s) / 6.02214076×10 23 / mol=1.0364×10 -5 mol / s (2-1)

[0065] The molar mass of CaCO3 is 100 g / mol, so the current density of the anode plate of the electrochemical treatment equipment is J (unit A / cm 2 ), the double-sided area of ​​the anode plate is S (in cm 2 ), the CaCO3 mass flow rate F (g / s) produced per second can be derived from the following formula:

[0066] F=J*S*100*1.0364×10 -5 =J*S*1.0364×10 -3 (g / s) (2-2)

[0067] Formula (2-2) is the mass flow rate per second of CaCO3 (calcium carbonate) produced by the electrochemical treatment equipment obtained by theoretical calculation. However, in actual operation, it is affected by factors such as the water quality conditions of the circulating cooling water and the structural characteristics of the electrochemical treatment equipment itself. The actual mass flow rate per second Fc of CaCO3 (calcium carbonate) crystallized and precipitated on the cathode plate is shown as follows:

[0068] Fc=ACE*CE*J*S*100*1.0364×10 -5 =ACE*CE*J*S*1.0364×10 -3 (g / s) (2-3)

[0069] Where: ACE---is the average current efficiency, which means the number of electrons generated by the actual current is converted into OH - The effective conversion rate of ion number (unit %);

[0070] CE---is the crystallization efficiency, which indicates the CO3 produced by the actual electrochemical reaction 2- With Ca 2+ The crystallization efficiency (in %) of ions combining between the positive and negative plates of the electrochemical treatment equipment and crystallizing and precipitating on the cathode plate.

[0071] J is the current density of the anode plate of the electrochemical treatment equipment (unit A / cm 2 );

[0072] S---- is the double-sided area of ​​the anode plate of the electrochemical treatment equipment (unit: cm 2 )

[0073] ACE is related to the characteristics of the anode and cathode plates and the quality of the circulating cooling water; CE is related to the spacing between the anode and cathode plates of the electrochemical treatment equipment, the flow rate of the circulating water between the plates, the equipment structure and the cathode plate structure.

[0074] From reaction formula (1-2), it can be seen that two electrons are needed to produce one hydrogen molecule. The molar mass of hydrogen H2 is 2g / mol. The mass flow rate of hydrogen produced can be calculated by the following formula:

[0075] F H =J*S*2*1.0364×10 -5 / 2=J*S*1.0364×10 -5 (g / s) (2-4)

[0076] Under standard conditions, the density of hydrogen is 0.089 kg / m 3 =0.089g / L, then the theoretical hydrogen volume flow rate is:

[0077] Theoretical hydrogen volume flow rate = J*S*1.0364×10-5 (g / s) / (0.089g / L)=J*S*1.1645×10 -4 (L / s)

[0078] By measuring the actual volume flow of hydrogen produced by the electrochemical device experiment, it can be concluded that ACE = actual volume flow of hydrogen produced / theoretical volume flow of hydrogen.

[0079] CE can be calculated by formula (2-3) by taking CE as 1 to obtain the theoretical CaCO3 mass flow rate. Then, the actual deposition amount on the cathode plate can be measured by conducting an electrochemical device experiment. The ratio of the two is CE = actual deposition amount on the cathode plate / theoretical CaCO3 mass flow rate.

[0080] The above is a theoretical calculation of the electrochemical reaction to generate OH - ions, thereby forming HCO3 and OH to form CO3 2- and Ca 2+ The reaction generates CaCO3 which crystallizes and precipitates on the cathode plate.

[0081] (II) The derivation steps of a method for calculating the specific energy consumption of an electrochemical treatment device for removing a unit mass of calcium carbonate (CaCO3) from circulating cooling water are as follows:

[0082] According to the double-sided area of ​​the anode plate of the electrochemical treatment equipment S (unit: cm 2 ), the distance between the anode and cathode plates L (cm), the current density of the anode plate of the electrochemical treatment equipment J (unit A / cm 2 ), the electrical conductivity of the circulating cooling water σ (us / cm), the specific energy consumption EER (kW.h / kg) of the electrochemical treatment equipment (i.e. the amount of electricity consumed to remove 1 kg of calcium carbonate CaCO3) can be obtained, thereby judging the power consumption efficiency of the electrochemical treatment equipment.

[0083] Assume that the resistance R (Ω) and current I (A) of the circulating water between the anode and cathode plates are:

[0084] R=1000000*L / (σ*S) (2-5)

[0085] I=S*J (2-6)

[0086] The power consumed between the anode and cathode plates is P (kW):

[0087] P=I 2 *R / 1000=S 2 *J 2 *1000000*L / ((σ*S)*1000)=1000*S*J 2 *L / σ(kW) (2-7)

[0088] Then the specific energy consumption EER (kW.h / kg) can be derived and expressed by the following formula:

[0089] EER = [1000*S*J 2 *L / σ] / [3600*(ACE*CE*J*S*1.0364×10 -3 ) / 1000]

[0090] =2.6802*10 5 *J*L / [σ*ACE*CE](kW.h / kg) (2-8)

[0091] (III) A method for calculating the change of hardness over time in circulating cooling water after electrochemical treatment equipment is derived as follows:

[0092] According to GBT 50050-2017 Industrial Circulating Cooling Water Treatment Design Specification, the calculation formula for circulating cooling water in industrial open systems is as follows:

[0093] The amount of make-up water for circulating cooling water in an open system can be calculated according to the following formula:

[0094] Qm=Qe+Qw+Qb (3-1)

[0095] Qe=k1*Δt*Qr (3-2)

[0096] Qm=Qe*N / (N-1) (3-3)

[0097] Qw=k2*Qr (3-4)

[0098] In the formula: Qm---Supplementary water volume (m 3 / h);

[0099] Qe---evaporated water (m 3 / h);

[0100] Qw---Wind heat loss (m 3 / h);

[0101] Qb---wastewater discharge (m 3 / h);

[0102] k1---evaporation loss coefficient (1 / ℃), take the value according to Table 1 below, and use interpolation method to calculate when the temperature is the middle value;

[0103] Δt---the temperature difference between circulating cooling water inlet and outlet of cooling tower (℃);

[0104] Qr---Circulating cooling water volume (m 3 / h);

[0105] k2---wind loss coefficient;

[0106] N---concentration multiple;

[0107] Table 1 Evaporation loss coefficient table

[0108] Inlet air temperature ℃ -10 0 10 20 30 40 Evaporation loss coefficient (1 / ℃) 0.0008 0.0010 0.0012 0.0014 0.0015 0.0016

[0109] The concentration multiple can also be calculated by the following formula:

[0110] N=Qm / (Qw+Qb) (3-5)

[0111] Qb=(Qe / (N-1))-Qw (3-6)

[0112] The calculation of the change in the hardness of the circulating cooling water over time under the operation of the electrochemical equipment can be derived from the following steps:

[0113] Assumption: The circulating water volume is Qr(m 3 / h), the circulating cooling water system has a water volume of Q1 (m 3 ), the amount of water added is Qm(m 3 / h), the sewage discharge volume is Qb(m 3 / h), wind heat loss Qw(m 3 / h), the initial hardness in the circulating water pool is Y0 (mg / L), the hardness of the make-up water is Ym (mg / L), and the amount of calcium carbonate removed per hour by the electrochemical device is Fc (mg / h).

[0114] a) The increase in hardness per unit hour Ym1 caused by the water replenishment Qm is:

[0115] Ym1=Qm*Ym / Q1(mg / Lh) (4-1)

[0116] b) The hardness reduction per unit hour carried away by the wind heat loss Qw and the sewage discharge Qb is:

[0117] Ywb=(Qw+Qb)*Y0 / Q1(mg / Lh) (4-2)

[0118] Hardness reduction rate relative to the initial hardness of circulating cooling water in the circulating water pool:

[0119] Kwb=Ywb / Y0 (4-3)

[0120] c) The hardness reduction per unit hour Yx removed by the electrochemical treatment equipment is:

[0121] Yx=Fc / (1000*Q1)(mg / Lh) (4-4)

[0122] d) According to the above data, the hardness Yz1 of the circulating water changes in the first hour of the electrochemical device operation:

[0123] Yz1=Y0+(Ym1-Yx)-Kwb*Y0=Y0*(1-Kwb)+(Ym1-Yx)=Y0*a+b (4-5)

[0124] Where: a = (1-Kwb); b = (Ym1-Yx)

[0125] e) In the second hour, the hardness Yz2 of the circulating water changes to:

[0126] Yz2=Yz1*a+b (4-6)

[0127] f) From formulas (4-5) and (4-6), we can see that this is a calculation formula for a differential equation, from which we can derive the calculation method for the change in circulating cooling water hardness over time, that is, the change in the circulating water hardness Yzn after the nth hour is:

[0128] Yzn=Y0*a n +[(1-a n ) / (1-a)]*b (4-7)

[0129] According to the above calculation method, the application is as follows: In a certain industrial circulating cooling water application project, the operating parameters, water quality parameters, and electrochemical equipment parameters of the circulating cooling water system are assumed as follows:

[0130] A1) The current density of the anode plate of the electrochemical device is J = 0.02 (A / cm 2 );

[0131] A2) The double-sided area of ​​the anode plate of the electrochemical treatment equipment is S = 289000 (unit: cm 2 )

[0132] A3) Average current efficiency ACE of electrochemical treatment equipment = 80%, crystallization efficiency CE = 88%;

[0133] A4) Circulating cooling water conductivity σ=2200us / cm;

[0134] A5) The distance between the positive and negative plates of the electrochemical treatment equipment is L = 1 cm;

[0135] A6) The circulating water volume is Qr = 5000 (m 3 / h);

[0136] A7) The circulating cooling water system has a water volume of Q1 = 1000 (m 3 );

[0137] A8) The initial hardness in the circulating water pool is Y0 = 700 (mg / L);

[0138] A9) The hardness of the supplementary water is Ym=350 (mg / L);

[0139] A10) The concentration multiple of the open circulating cooling water system is set to 4, and the temperature difference between the circulating cooling water entering and leaving the cooling tower is Δt = 10°C.

[0140] A11) Evaporation loss coefficient k1 = 0.0016 (the coefficient when the air temperature entering the tower is 40°C);

[0141] A12) Wind heat loss coefficient k2 = 0.05% (select wind tube type natural ventilation cooling tower);

[0142] The mass flow rate Fc per second of CaCO3 (calcium carbonate) precipitated onto the cathode plate is:

[0143] Fc=ACE*CE*J*S*100*1.0364×10 -5 =ACE*CE*J*S*1.0364×10 -3 (g / s)

[0144] Where: ACE---is the average current efficiency, which means the number of electrons generated by the actual current is converted into OH - The effective conversion rate of ion number (unit %);

[0145] CE---is the crystallization efficiency, which indicates the CO3 produced by the actual electrochemical reaction 2- With Ca 2+ The crystallization efficiency (in %) of ions combining between the positive and negative plates of the electrochemical treatment equipment and crystallizing and precipitating on the cathode plate.

[0146] J is the current density of the anode plate of the electrochemical treatment equipment (unit: A / cm 2 );

[0147] S----is the double-sided area of ​​the anode plate of the electrochemical treatment equipment (unit: cm 2 )

[0148] Specific energy consumption EER of electrochemical treatment equipment:

[0149] EER=2.6802*10 5 *J*L / [σ*ACE*CE](kW.h / kg)

[0150] Where: L---is the distance between the positive and negative plates of the electrochemical treatment equipment (in cm);

[0151] σ---is the conductivity of circulating cooling water (unit: us / cm).

[0152] Circulating cooling water hardness change over time Yzn:

[0153] Yzn=Y0*a n +[(1-a n ) / (1-a)]*b

[0154] Where: Y0---is the initial hardness in the circulating water pool (unit: mg / L);

[0155] a=(1-Kwb), Kwb is the hardness reduction rate (in %) relative to the initial hardness of the circulating cooling water in the circulating water pool. b=(Ym1-Yx), which is the difference (in mg / L) between the hardness increase per hour Ym1 brought by the replenishment water volume Qm and the hardness reduction per hour Yx removed by the electrochemical treatment equipment.

[0156] According to formula (2-3), the following calculation can be done:

[0157] The amount of calcium carbonate removed per hour by electrochemical equipment is:

[0158] Fc=ACE*CE*J*S*1.0364*10 -3

[0159] =80%*88%*0.02*289000*1.0364*10 -3

[0160] =4.217(g / s)=1.518*10 7 (mg / h);

[0161] According to formula (2-8), its specific energy consumption EER can be calculated as follows:

[0162] EER=2.6802*10 5 *J*L / [σ*ACE*CE]

[0163] =2.6802*10 5 *0.02*1 / [2200*0.8*0.88]

[0164] =3.46(kW.h / kg)

[0165] According to formulas (3-1) to (3-6), the following calculations can be made:

[0166] B1) Evaporated water amount Qe = k1*Δt*Qr = 0.0016*10*5000 = 80 (m 3 / h);

[0167] B2) Wind heat loss Qw = k2*Qr = 0.05%*5000 = 2.5 (m 3 / h);

[0168] B3) Wastewater discharge volume Qb = (Qe / (N-1))-Qw = (80 / (4-1))-2.5 = 24.2 (m 3 / h);

[0169] B4) Make-up water volume Qm = Qe + Qw + Qb = 80 + 24.2 + 2.5 = 106.7 (m 3 / h).

[0170] According to formulas (4-1) to (4-7), the following calculations can be made:

[0171] C1) The increase in hardness per unit hour Ym1 caused by the water replenishment Qm is:

[0172] Ym1=Qm*Ym / Q1=106.7*350 / 1000=37.3(mg / Lh);

[0173] C2) The hardness reduction Kwb per unit hour carried away by the wind heat loss Qw and the sewage discharge Qb is:

[0174] Ywb=(Qw+Qb)*Y0 / Q1=(24.2+2.5)*700 / 1000=18.69(mg / Lh);

[0175] Hardness decrease rate: Kwb = Ywb / Y0 = 18.69 / 700 = 0.0267;

[0176] C3) The hardness reduction per unit hour Yx removed by the electrochemical treatment equipment is:

[0177] Yx=Fc / (1000*Q1)=1.518*10 7 / (1000*1000)=15.18(mg / Lh);

[0178] C4) According to formula (4-5), we can get:

[0179] a=(1-Kwb)=1-0.0267=0.9733;

[0180] b1=(Ym1-Yx)=37.3-0=37.3(mg / Lh)----no electrochemical equipment operation;

[0181] b2=(Ym1-Yx)=37.3-15.18=22.12(mg / Lh)----Electrochemical equipment is in operation;

[0182] C5) According to formula (4-7), after the first hour, the hardness Yz1 of the circulating water changes to:

[0183] Yz1=Y0*a+b1=700*0.9733+37.3=718.7(mg / L)----the case where no electrochemical equipment is running;

[0184] Yz1=Y0*a+b2=700*0.9733+22.12=703.4(mg / L)----When electrochemical equipment is running;

[0185] C6) After 24 hours, the hardness of circulating water Yz24 changes to:

[0186] Yz24=Y0*a 24 +[(1-a 24 ) / (1-a)]*b1

[0187] =700*0.9733 24 +[(1-0.9733 24 ) / (1-0.9733)]*37.3

[0188] =1034.1 (mg / L)----no electrochemical equipment in operation;

[0189] Yz24=Y0*a 24 +[(1-a 24 ) / (1-a)]*b2

[0190] =700*0.9733 24 +[(1-0.9733 24 ) / (1-0.9733)]*22.12

[0191] =762.4 (mg / L)----When electrochemical equipment is running;

[0192] C7) When the electrochemical equipment is running, the hardness of the circulating water changes from Yz200 to

[0193] becomes:

[0194] Yz200=Y0*a 200 +[(1-a 200 ) / (1-a)]*b1

[0195] =700*0.9733 200 +[(1-0.9733 200 ) / (1-0.9733)]*37.3

[0196] =1397 (mg / L)----no electrochemical equipment in operation;

[0197] Yz200=Y0*a 200 +[(1-a 200 ) / (1-a)]*b2

[0198] =700*0.9733 200 +[(1-0.9733 200 ) / (1-0.9733)]*22.12

[0199] =830 (mg / L) ---- when electrochemical equipment is running;

[0200] After running for 200 hours, the hardness of the circulating water reaches a balance point, and the hardness no longer increases over time. It can be seen that when using electrochemical equipment, the hardness balance point of the circulating water is 830mg / L; while without electrochemical equipment, the hardness balance point of the circulating water is 1397mg / L. After using the electrochemical treatment equipment, the hardness of the circulating cooling water is reduced by 567mg / L. When the hardness of the circulating water reaches the balance point, as long as the hardness of the make-up water quality, the circulating water volume, the evaporated water volume and the drainage volume remain relatively stable, this balance point remains unchanged, and the hardness of the entire circulating water system will reach a stable state.

Claims

1. A method for calculating the electrochemical descaling efficiency of industrial circulating cooling water, characterized in that: Including the calculation method of how much CaCO3 mass in circulating cooling water is removed by electrochemical treatment equipment per unit time, the calculation method of the specific energy consumption of the amount of electricity consumed by electrochemical treatment equipment to remove unit mass of CaCO3 in circulating cooling water, and the calculation method of the change of hardness in circulating cooling water over time after applying electrochemical treatment equipment; According to the deposition of CaCO3 generated by the electrochemical reaction on the cathode plate surface, and considering the influence of the circulating cooling water quality conditions and the structural characteristics of the electrochemical treatment equipment itself in actual operation, the deposition amount of CaCO3 generated by the electrochemical treatment equipment on the cathode surface per unit time is deduced. The deposition amount is the mass of CaCO3 removed by the electrochemical treatment equipment per unit time; According to the double-sided area of ​​the anode plate of the electrochemical treatment equipment, the distance between the anode and cathode plates, the current density of the anode plate of the electrochemical treatment equipment, and the conductivity of the circulating cooling water, the power consumed between the anode and cathode plates is calculated, and the specific energy consumption of the electrochemical treatment equipment is derived; The hardness of the circulating water after the nth hour is derived based on the increase in hardness per unit hour caused by the water replenishment during the operation of the electrochemical equipment, the decrease rate of hardness per unit hour caused by the heat loss from wind and the sewage discharge, the decrease rate of hardness of the initial hardness of the circulating cooling water, and the decrease in hardness per unit hour removed by the electrochemical treatment equipment.

2. The method for calculating the electrochemical descaling efficiency of industrial circulating cooling water according to claim 1 is characterized in that: The deposition amount is the mass flow rate Fc per second of CaCO3 crystallized and deposited on the cathode plate, as shown in the following formula: Fc=ACE*CE*J*S*100*1.0364×10 -5 =ACE*CE*J*S*1.0364×10 -3 (g / s) In the formula, Fc-- is the mass flow rate per second; - ACE--average current efficiency, which indicates the effective conversion rate of the number of electrons generated by the actual current into the number of 0H ions, in %; CE--Crystallization efficiency, indicating the CO3 produced by the actual electrochemical reaction 2- With Ca 2+ The crystallization efficiency of ions combining between the positive and negative plates of the electrochemical treatment equipment and crystallizing and precipitating on the cathode plate, in %; J---current density of the anode plate of the electrochemical treatment equipment, unit is A / cm 2 ; S---is the double-sided area of ​​the anode plate of the electrochemical treatment equipment, in cm 2 .

3. The method for calculating the electrochemical descaling efficiency of industrial circulating cooling water according to claim 2 is characterized in that: ACE is related to the characteristics of the anode and cathode plates and the quality of the circulating cooling water; CE is related to the spacing between the anode and cathode plates of the electrochemical treatment equipment, the flow rate of the circulating water between the plates, the equipment structure and the structure of the cathode plate. ACE = actual hydrogen volume flow / theoretical hydrogen volume flow CE = actual deposition amount on the cathode plate / theoretical CaCO3 mass flow rate.

4. The method for calculating the electrochemical descaling efficiency of industrial circulating cooling water according to claim 2 is characterized in that: The calculation formula for the power consumed between the anode and cathode plates is: P=I 2 *R / 1000=S 2 *J 2 *1000000*L / ((σ*S)*1000)=1000*S*J 2 *L / s The calculation formula of specific energy consumption EER of electrochemical treatment equipment is as follows: EER=[1000*S*J 2 *L / σ] / [3600*(ACE*CE*J*S*1.0364×10 -3 ) / 1000] =2.6802*10 5 *J*L / [σ*ACE*CE] In the formula, P is the power consumed between the anode and cathode plates, in kW; EER is the specific energy consumption, in kW.h / kg, which means the amount of electricity consumed to remove 1 kg of CaCO3; S is the double-sided area of ​​the anode plate of the electrochemical treatment equipment, in cm 2 ; L is the distance between the anode and cathode plates, in cm; J is the current density of the anode plate of the electrochemical treatment equipment, in A / cm 2 ; σ is the conductivity of circulating cooling water, unit is us / cm.

5. The method for calculating the electrochemical descaling efficiency of industrial circulating cooling water according to claim 2 is characterized in that: By calculating the hardness of the circulating water after the nth hour, we can get the calculation formula of hardness changing with time; The formula for calculating the hardness of circulating water after the nth hour is: Yzn=Y0*a n +[(1-a n ) / (1-a)]*b a=(1-Kwb) b=(Ym1-Yx) Ym1=Qm*Ym / Q1 Kwb=Ywb / Y0 Ywb=(Qw+Qb)*Y0 / Q1 Yx=Fc / (1000*Q1) Where, Yzn is the change in hardness of circulating water after the nth hour; Qm is the amount of replenished water, unit is m 3 / h; Ym is the hardness of the make-up water, in mg / L; Q1 is the amount of water in the circulating cooling water system, in m 3 ; Ym1 is the increase in hardness per unit hour caused by the water replenishment amount Qm; Y0 is the initial hardness in the circulating water pool, in mg / L; Qb is the amount of sewage discharged, in m 3 / h; Qw is the wind heat loss, unit is m 3 / h; Ywb is the hardness reduction per unit hour carried away by the wind heat loss Qw and the sewage discharge Qb; Kwb is the hardness reduction rate relative to the initial hardness of the circulating cooling water in the circulating water pool; Yx is the hardness reduction per unit hour removed by the electrochemical treatment equipment.