A method for controlling the acidity of mother liquor in a sulphuric acid production system

Abstract

The application discloses a kind of ammonium sulfate production system mother liquor acidity control method, comprising: (1) setting normal mother liquor acidity, and the total volume of current mother liquor and the acidity of current mother liquor are obtained by on-line detection;(2) according to the volume of coal gas entering saturator in unit time and the ammonia content of coal gas inlet and outlet, the amount of sulfuric acid consumed in unit time is calculated according to the reaction formula;(3) when the acidity is lower than the normal mother liquor acidity, the volume of sulfuric acid to be added is calculated according to the amount of acid consumed and the amount of acid required to adjust the acidity, when the acidity is higher than the normal mother liquor acidity, the volume of water required to adjust to the normal mother liquor acidity is calculated;(4) when adding concentrated sulfuric acid, first add acid quickly with the target amount of sulfuric acid required to adjust to the normal mother liquor acidity, then add acid uniformly with the target amount of sulfuric acid consumed in unit time, and when adding water, add water quickly.The application realizes automatic adjustment of acidity, improves the level of automation, and is more conducive to improving the quality of ammonium sulfate crystals.

Description

TECHNICAL FIELD

[0001] The application relates to a mother liquor acidity control method for a sulfur-ammonium production system. BACKGROUND

[0002] In a spray-type saturator ammonium sulfate production process, the mother liquor in the spray-type saturator needs to be added with acid and washing water to maintain the solution acidity. In a traditional method, a high-density concentrated sulfuric acid solution is manually added by an on-site operator according to experience, and the recycled sulfur-ammonium mother liquor after coal gas purification is used to form a new sulfur-ammonium mother liquor. During the configuration process, the worker manually samples the mother liquor to detect the acidity every certain time, manually adds the amount of sulfuric acid according to personal experience, and maintains the circulating mother liquor acidity at 3%-5% to ensure the quality of the precipitated crystals. The mother liquor acidity detection is manually detected, and the acidity detection is performed by the acidity detection personnel every half hour or hour. The sampling is performed in an open crystallization tank, and the acidity titration is performed on a test table after sampling to detect the sulfur-ammonium mother liquor acidity. After the mother liquor acidity is detected, the acid adding flow is manually adjusted to maintain the mother liquor acidity in the process requirement range. Since the sulfur-ammonium crystallization process is affected by multiple factors, once a certain factor is not properly controlled in the production, the acidity will be out of limit, and the product quality is affected. The on-site environment is poor, the labor intensity is large, the manual measurement error fluctuation is large, the saturator production control is easily affected and fluctuated, the concentrated sulfuric acid consumption is large, and the sulfur-ammonium product yield and quality are fluctuated. SUMMARY

[0003] In view of the problems in the prior art, the application provides a mother liquor acidity control method for a sulfur-ammonium production system, realizes full-automatic acidity adjustment, improves the automation level, eliminates the quality fluctuation caused by human factors, and is more beneficial to improving the quality of the sulfur-ammonium crystals.

[0004] The technical scheme adopted by the application is as follows: a mother liquor acidity control method for a sulfur-ammonium production system, comprising the following steps:

[0005] Step one, setting the normal mother liquor acidity as a0, obtaining the total volume V of the current mother liquor and the acidity a1 of the current mother liquor through an online detection device; 液

[0006] Step two, calculating the sulfuric acid consumption M in a unit time t 酸 : setting the acid adding interval unit time t, detecting the coal gas volume V entering the saturator in the unit time t, the saturator coal gas import ammonia content C1 and the saturator coal gas export ammonia content C2, and according to the reaction formula: H2SO4+2NH3→(NH4)2SO4+H2O, the sulfuric acid consumption M in the unit time t is 煤气 酸 煤气 ​​​*98 / 2*17;

[0007] Step three, calculate the amount of sulfuric acid or water to be added:

[0008] When a1≤a0, add concentrated sulfuric acid, the volume V 酸 of concentrated sulfuric acid to be added is:

[0009]

[0010] Where K is the compensation factor, C is the molar concentration of potassium hydroxide used in titration, and p is the density of the added concentrated sulfuric acid.

[0011] When a1>a0, add water, the volume V 水 of water to be added is:

[0012]

[0013] Step four, add concentrated sulfuric acid or water: when adding concentrated sulfuric acid, the acid is added in two steps. The first step is rapid adjustment, with the target value of adjusted by PID, and the opening degree of the concentrated sulfuric acid regulating valve first reaches the maximum during the adjustment process, until it approaches the value of V 酸 , then gradually decreases, and becomes 0 when reaching the value of V 酸 , so that the ammonium sulfate mother liquor acidity quickly reaches the set acidity value a0. The second step is uniform adjustment, which divides into a flow curve within a unit time t, and controls the opening degree of the acid regulating valve through PID control, to ensure that the actual flow is controlled according to the set flow, so that the acid addition and acid consumption are synchronized, and the acidity is stable. When adding water, V 水 is the PID adjustment target value, and water is added quickly.

[0014] Step five: after the mother liquor circulates for a unit time t, repeat the process of mother liquor acidity measurement, calculation of sulfuric acid or water addition amount, and addition of concentrated sulfuric acid or water, and record the measured data.

[0015] Further, the modification of the compensation coefficient is also included, specifically: the concentration of sulfuric acid or the amount of water added is calculated for each measurement of the mother liquor acidity value, and the next measurement adjustment is measured again to obtain a mother liquor acidity value, which is compared with the adjustment target acidity of this time, that is, the deviation, the deviation value is related to the acidity adjustment amount, the deviation rate E = 1 + (target acidity - last measurement acidity) / (target acidity - this measurement acidity); the initial compensation coefficient K = 1, the deviation rate E = 1, after each measurement, a deviation rate is obtained according to the deviation rate E = 1 + (target acidity - last measurement acidity) / (target acidity - this measurement acidity), and after multiple acid adjustment, multiple deviation rates can be obtained, and the average deviation rate E under a certain compensation coefficient K can be calculated by taking the average of the multiple deviation rates and the smoothing mathematical processing method, so as to calculate the new compensation coefficient K' = K*E eve . eve The more samples, the more accurate the compensation coefficient obtained. After inputting the compensation coefficient K', the system will still calculate and record the subsequent deviation rate E value, and a more accurate K"' can be obtained by the same average method.

[0016] Further, the total volume V 液 of the mother liquor is the sum of the volume V1 of the mother liquor in the saturator, the volume V2 of the mother liquor in the full-flow tank, and the volume V3 of the mother liquor in the crystallization tank.

[0017] Further, the volume V1 of the mother liquor in the saturator is a fixed value, the volume V2 of the mother liquor in the full-flow tank is obtained by real-time calculation of the detection data of the liquid level meter arranged at the full-flow tank combined with the cross-sectional area of the full-flow tank, and the volume V3 of the mother liquor in the crystallization tank is obtained by real-time calculation of the detection data of the liquid level meter arranged at the crystallization tank and the solid-liquid interface online detection device for detecting the position of the solid-liquid interface in the crystallization tank combined with the cross-sectional area of the crystallization tank.

[0018] Further, the unit time t is 0.5-2 hours.

[0019] The beneficial effects of the present application are: the present application upgrades the traditional manual measurement and manual experience manual adjustment to full-automatic acidity adjustment, improves the automation level, eliminates the quality fluctuations caused by human factors, and is more conducive to the improvement of the quality of ammonium sulfate crystals. The method of detecting once and adjusting once in a fixed time online is more in line with the actual working conditions. The calculation adjustment based on the acidity deviation calculates the amount of concentrated sulfuric acid or water to be added, and then compares and corrects the adjustment deviation data of the previous times, so that the acidity control accuracy is high. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention provides a method for controlling the acidity of mother liquor in an ammonium sulfate production system, comprising the following steps:

[0022] Step 1: Set the normal acidity of the mother liquor to a0, and obtain the current total volume V of the mother liquor using online monitoring equipment. 液 and the current acidity a1 of the mother liquor; wherein, the total volume V of the mother liquor 液 This refers to the sum of the mother liquor volumes V1 in the saturator, V2 in the full-flow tank, and V3 in the crystallization tank. For example, the mother liquor volumes V1, V2, and V3 in the saturator and crystallization tank can be obtained as follows: Since the saturator contains an overflow pipe, the mother liquor volume V1 in the saturator is a fixed value. The mother liquor volume V2 in the full-flow tank is calculated in real-time using the detection data obtained from the level gauge installed at the full-flow tank, combined with the cross-sectional area of ​​the full-flow tank. The mother liquor volume V3 in the crystallization tank is calculated in real-time using the detection data from the level gauge installed at the crystallization tank and an online solid-liquid interface detection device used to detect the position of the solid-liquid interface in the crystallization tank, combined with the cross-sectional area of ​​the crystallization tank. The current acidity a1 of the mother liquor is the real-time acidity data of the ammonium sulfate mother liquor obtained through a linear acidity detector.

[0023] Step 2: Calculate the amount of sulfuric acid M consumed in the reaction per unit time t. 酸 Set the acid addition interval unit time t, where t is a fixed time, such as half an hour, one hour, one and a half hours, two hours, etc. Detect the volume V of gas entering the saturator online within unit time t. 煤气 The ammonia content at the saturator gas inlet (C1), the ammonia content at the saturator gas outlet (C2), and the volume of gas entering the saturator per unit time (t) (V) 煤气 The ammonia content at the gas inlet can be automatically detected and controlled via a gas inlet flow meter and regulating valve. The ammonia content at the gas inlet (C1) and the ammonia content at the saturator gas outlet (C2) can be detected by an online detector. Based on the reaction equation: H2SO4 + 2NH3 → (NH4)2SO4 + H2O, the amount of sulfuric acid consumed per unit time (t) is M. 酸 =(C1-C2)*V 煤气 *98 / 2*17;

[0024] Step 3: Calculate the amount of sulfuric acid or water to be added: When a1 ≤ a0, add concentrated sulfuric acid, and the volume of concentrated sulfuric acid to be added is... Wherein, K is the compensation coefficient, C is the molar concentration of potassium hydroxide used for titration when detecting acidity, and p is the density of added concentrated sulfuric acid;

[0025] When a1>a0, water is added, and the volume V 水 is:

[0026] Step four, when adding concentrated sulfuric acid, the acid is added in two steps, the first step is rapid adjustment, to as the target value, adjusted by PID, and during the adjustment process, the opening degree of the concentrated sulfuric acid regulating valve first reaches the maximum, until it approaches V 酸 , and then the opening degree gradually decreases, and when it reaches V 酸 , the opening degree becomes 0, so that the ammonium sulfate mother liquor acidity quickly reaches the set acidity value a0, and the second step is uniform adjustment, and is divided into a flow curve in unit time t, and the opening degree of the acid adding regulating valve is controlled by PID control, so that the actual flow is controlled according to the set flow, so that the acid adding and acid consumption are synchronized, and the stability of the acidity is ensured; when adding water, V 水 is the PID adjustment target value, and the water is quickly added.

[0027] Step five: after the mother liquor circulates for unit time t, the process of mother liquor acidity measurement, calculation of the amount of added concentrated sulfuric acid or water, and addition of concentrated sulfuric acid or water is repeated, and the measured data is recorded.

[0028] To improve the accuracy of the adjustment, a compensation coefficient correction is also included, specifically: the measured mother liquor acidity value each time will calculate an amount of added concentrated sulfuric acid or water, and the next time the adjustment is measured, another mother liquor acidity value is measured, and the mother liquor acidity value is compared with the adjustment target acidity, that is, the deviation, the deviation value is related to the acidity adjustment amount, the deviation rate E = 1 + (target acidity - last measured acidity) / (target acidity - this time measured acidity); the compensation coefficient K = 1 at the beginning, the deviation rate E = 1, and after each measurement, a deviation rate is obtained according to the deviation rate E = 1 + (target acidity - last measured acidity) / (target acidity - this time measured acidity), and after multiple acid adjustments, multiple deviation rates can be obtained, and through the average of multiple deviation rates and the smoothing mathematical processing method, the average deviation rate E eve under a certain compensation coefficient K can be calculated, so as to calculate a new compensation coefficient K' eve , the more samples, the more accurate the compensation coefficient obtained. After inputting the compensation coefficient K', the system will still calculate and record the subsequent deviation rate E value, and the same average method can be used to obtain a more accurate K

[0029] Embodiment:

[0030] Generally, the acidity of ammonium sulfate saturated mother liquor should be controlled between 3% and 5%. Too high or too low an acidity will affect the quality of ammonium sulfate mother liquor crystallization. Here, an intermediate acidity of 4% is used as the target acidity value a0 for adjustment. The average gas generation V introduced into the saturator is monitored in real time. 煤气 60000m 3 / h, the average ammonia content (C1) at the saturator gas inlet is 8.6 g / m³. 3 The exported ammonia content (C2) is ≤0.05 g / m³. 3 Therefore, the average hourly ammonia consumption is 60000*(8.6-0.05)÷1000=513kg. According to the reaction formula: H2SO4+2NH3→(NH4)2SO4+H2O, the hourly sulfuric acid consumption is M. 酸 =513*98 / 2*17=1479kg.

[0031] Assuming that after significant acid adjustment, when stable crystal precipitation occurs, the acidity a1 measured in the first measurement is 3%, and the total volume V of the mother liquor measured at this time is assumed to be... 液 =V1 + V2 + V3 = 31000L, calculate V according to the following formula. 酸 :

[0032]

[0033] Where K = 1, C = 1.78 mol / L, and the density of the sulfuric acid solution ρ = 1.26 kg / L, that is:

[0034]

[0035] The acid addition is done in two steps. The first step is a quick adjustment. =438L is the target value. After PID adjustment, the opening of the concentrated sulfuric acid regulating valve first reaches its maximum during the adjustment process, until it approaches V. 酸 After reaching the ' value, the aperture gradually decreases, eventually reaching V. 酸 When the value is ', the opening becomes 0, allowing the acidity of the ammonium sulfate mother liquor to quickly reach the set acidity value a0. The second step is to uniformly adjust the acidity within one hour. The flow rate was divided into a curve and calculated to be 19.56 L / min. PID control was implemented with the flow rate setpoint of 19.56 L / min as the target value to synchronize acid addition and acid consumption, thus ensuring the stability of acidity.

[0036] Assume the total volume V of the mother liquor measured at this time is... 液 =V1+V2+V3=31000L, the measured acidity a1 is 5%, which needs to be diluted with water, according to the formula With V 水 =7750L is the PID adjustment target value for rapid water addition.

[0037] Compensation coefficient correction calculation: assuming that the compensation coefficient K=1 at the beginning, the deviation rate E=1, the first measurement of acidity is 3.5%, after one cycle of acid addition, the measured acidity is 2.5%, the deviation rate of the mother liquor is E1=1+(4%-3.5%) / (4%-2.5%) =1.33, the data of continuous measurement for one day is obtained, n=24, and E1~E24 is obtained.

[0038] If 24 deviation rates are obtained in one day, a curve with time axis as X axis and E value as Y axis can be obtained, and the user can view the change rule of E value according to the curve. It is assumed that E1=1.33, E2=K3=..=E24=1.2 are measured in one day,

[0039] Average deviation rate E eve =(E1+E2+E3+....+En) / 24=(1.33+1.2+1.2+_=..+1.2) / 24=1.205,

[0040] The first corrected compensation coefficient K' is:

[0041] K'=K*E eve =1*(1.33+1.2+1.2+_=..+1.2) / 24=1.205,

[0042] After the compensation coefficient K' value is input, the system can continue to calculate the deviation rate. It is assumed that the first corrected compensation coefficient K' value is 1.205, and 24 deviation rates are measured again after 24 hours, and it is assumed that the newly calculated 24 deviation rates are E1'=0.9.1, E2'=E3'=..=E24'=1.1,

[0043] The average deviation rate of the mother liquor under the compensation coefficient K' is E eve ':

[0044] E eve '=(E1'+E2'+E3'+....+En') / 24=(0.9+1.1+1.1+..+1.1) / 12=1.09,

[0045] The second calculated compensation coefficient K''=K'*E eve '=1.205*1.09=1.313, and the corrected compensation coefficient 1.313 is used for adjustment.

[0046] The above is only an example and description of the structure of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the structure of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. A method for controlling the acidity of mother liquor in an ammonium sulfate production system, characterized in that, Includes the following steps: Step 1: Set the normal acidity of the mother liquor to a0, and obtain the current total volume V of the mother liquor using online monitoring equipment. 液 and the current acidity a1 of the mother liquor; Step 2: Calculate the amount of sulfuric acid M consumed in the reaction per unit time t. 酸 Set the acid addition interval unit time t, and detect the volume V of gas entering the saturator within unit time t online. 煤气 And the ammonia content C1 at the saturator gas inlet and the ammonia content C2 at the saturator gas outlet, according to the reaction formula: H₂SO₄ + 2NH₃ → (NH₄)₂SO₄ + H₂O The amount of sulfuric acid consumed per unit time t is M. 酸 =(C1-C2)*V 煤气 *98 / 2*17; Step 3: Calculate the amount of sulfuric acid or water that needs to be added: When a1≤a0, the volume of concentrated sulfuric acid added is V. 酸 for: Where K is the compensation coefficient, C is the molar concentration of potassium hydroxide used in the titration during acidity detection, and ρ is the density of the added concentrated sulfuric acid; When a1 > a0, water is added, and the volume of water added is V. 水 for: Step 4, add concentrated sulfuric acid or water: When adding concentrated sulfuric acid, the acid addition should be done in two steps. The first step is a quick adjustment to... As the target value, after PID adjustment, the opening of the concentrated sulfuric acid regulating valve first reaches its maximum during the adjustment process, until it approaches V. 酸 After reaching the ' value, the aperture gradually decreases, eventually reaching V. 酸 When the value is ', the opening becomes 0, allowing the acidity of the ammonium sulfate mother liquor to quickly reach the set acidity value a0. The second step is uniform adjustment, which involves adjusting the acidity within a unit time t. The flow rate is divided into curves, and PID control is used to control the opening of the acid addition regulating valve to ensure that the actual flow rate is controlled according to the set flow rate, so that acid addition and acid consumption are synchronized to ensure acidity stability; when adding water, it is based on V 水 Adjust the target value for the PID controller and add water quickly; Step 5: After the mother liquor is circulated for a unit time t, repeat the process of measuring the acidity of the mother liquor, calculating the amount of sulfuric acid or water to be added, adding concentrated sulfuric acid or water, and record the measured data.

2. The method for controlling the acidity of mother liquor in an ammonium sulfate production system as described in claim 1, characterized in that, This also includes the correction of the compensation coefficient. Specifically, for each measurement of the mother liquor acidity value, a concentrated sulfuric acid addition amount or water addition amount is calculated. During the next measurement and adjustment, another mother liquor acidity value is measured and compared with the target acidity for this adjustment; this is the deviation, and the deviation value is related to the acidity adjustment amount. Initially, the compensation coefficient K = 1, and the deviation rate E = 1. After each measurement, a new deviation rate is obtained according to the deviation rate E = 1 + (target acidity - previous measured acidity) / (target acidity - current measured acidity). After multiple acid adjustments, multiple new deviation rates can be obtained. Through weighted averaging and smoothing mathematical processing methods, the average deviation rate E under a certain compensation coefficient K can be calculated. eve The value is used to calculate the new compensation coefficient K' = K*E. eve The more samples there are, the more accurate the compensation coefficient will be.

3. The method for controlling the acidity of mother liquor in an ammonium sulfate production system as described in claim 1, characterized in that, The total volume V of the mother liquor 液 It is the sum of the mother liquor volume V1 in the saturator, the mother liquor volume V2 in the full flow tank, and the mother liquor volume V3 in the crystallization tank.

4. The method for controlling the acidity of mother liquor in an ammonium sulfate production system as described in claim 1, characterized in that, The mother liquor volume V1 in the saturator is a fixed value. The mother liquor volume V2 in the full flow tank is calculated in real time by combining the detection data obtained by the level gauge installed at the full flow tank with the cross-sectional area of ​​the full flow tank. The mother liquor volume V3 in the crystallization tank is calculated in real time by combining the detection data of the level gauge installed at the crystallization tank and the online solid-liquid interface detection device used to detect the position of the solid-liquid interface of the crystals in the crystallization tank with the cross-sectional area of ​​the crystallization tank.

5. The method for controlling the acidity of mother liquor in an ammonium sulfate production system as described in claim 1, characterized in that, The unit time t is 0.5 to 2 hours.

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