Calcium desulfurization gypsum high-efficiency separation method based on slurry density regulation

Abstract

This invention discloses a high-efficiency separation method for gypsum in calcium-based desulfurization based on slurry density control, relating to the field of industrial flue gas purification. The method includes: S1, real-time monitoring of the density of the gypsum slurry in the calcium-based desulfurization system, which is about to be transported to the first-stage hydrocyclone for solid-liquid separation; S2, obtaining a target addition ratio based on a preset dynamic correlation model between slurry density and defoamer addition ratio, and adding defoamer to the gypsum slurry in real-time according to the target addition ratio; S3, transporting the gypsum slurry with added defoamer to the first-stage hydrocyclone for solid-liquid separation. This method achieves precise foam suppression through dynamic control, creating an excellent separation environment for the hydrocyclone, enabling efficient separation of gypsum crystals. Simultaneously, it achieves on-demand distribution of defoamer, reducing the total amount of reagent consumed while ensuring effectiveness and saving operating costs.

Description

Technical Field

[0001] This invention relates to industrial flue gas purification technology, specifically to a high-efficiency separation method for calcium-based desulfurization gypsum based on slurry density control. Background Technology

[0002] In industrial production using limestone-gypsum wet desulfurization (calcium-based desulfurization), such as in the carbon, power, and metallurgical industries, the gypsum slurry generated in the absorption tower needs to be separated into solid and liquid components using equipment such as hydrocyclones to produce gypsum byproducts that can be recycled. The efficiency and stability of this separation process directly determine the operating cost of the desulfurization system and the value of the byproducts.

[0003] In existing technologies, chemical defoamers are commonly added to the system to suppress harmful foam generated during the mixing, conveying, and separation of slurry. However, the current mainstream method of adding defoamers has a significant technical problem: the proportion of defoamer added is usually fixed or manually adjusted only based on experience, which cannot respond to the real-time dynamic changes in the physicochemical state of the slurry.

[0004] The drawback of this fixed-ratio addition method is that when fluctuations in flue gas composition and changes in reaction conditions lead to a decrease in the solid content and an increase in foaming tendency in the slurry, the original fixed addition amount is insufficient to effectively suppress foam. Foam entrainment severely deteriorates the hydrocyclone's separation environment, resulting in decreased centrifugal separation efficiency. The direct consequence is an increased water content and decreased purity in the gypsum slurry discharged from the hydrocyclone's underflow, while the overflow carries a large number of solid particles (i.e., "slurry runoff"). More seriously, stable foam can cause frequent blockages in the hydrocyclone's overflow pipe and underflow outlet, forcing the system to shut down for flushing, severely threatening the long-term, continuous, and stable operation of the desulfurization unit. Therefore, how to accurately match the real-time state of the slurry with the addition of defoamer to fundamentally stabilize the separation process is a pressing technical problem in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a high-efficiency separation method for calcium-based desulfurization gypsum based on slurry density control, so as to solve the problems of low separation efficiency and system instability caused by the fixed proportion of defoamer added in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a highly efficient separation method for calcium-based desulfurization gypsum based on slurry density control, comprising:

[0007] S1. Real-time monitoring of the density of the gypsum slurry that is about to be transported to the first-stage hydrocyclone for solid-liquid separation in the calcium desulfurization system, and obtaining the density value;

[0008] An online density meter is installed on the pipeline that delivers the gypsum slurry to the first-stage hydrocyclone for solid-liquid separation (preferably in the section between the hydrocyclone feed pump outlet and the hydrocyclone inlet); the instrument continuously and in real time measures the instantaneous density value of the slurry and transmits the signal to the central control system in real time.

[0009] S2. Based on the preset dynamic correlation model between slurry density and defoamer addition ratio, and the density value, the target addition ratio is obtained, and defoamer is added to the gypsum slurry in real time according to the target addition ratio; the dynamic correlation model specifies the negative correlation control relationship between slurry density value and defoamer addition ratio;

[0010] S3. The gypsum slurry with added defoamer is conveyed to a primary hydrocyclone for solid-liquid separation to obtain desulfurized gypsum.

[0011] Furthermore, the dynamic correlation model is a piecewise function model, which divides the slurry density into at least three continuous control intervals. Each control interval corresponds to an independent defoamer addition ratio range, and the defoamer addition ratio range corresponding to the control interval with a lower density value is higher than that of the control interval with a higher density value.

[0012] The dynamic correlation model is a control rule established based on extensive industrial experimental data to guide the addition of defoamers. Its establishment methods include:

[0013] a) Data acquisition phase: Under typical operating conditions of different loads, different coal types (or raw materials), and different desulfurizing agent qualities of the target desulfurization system, record the slurry density value corresponding to the system when it is stable;

[0014] b) Effect testing and calibration stage: Under each recorded density condition, manually fine-tune the amount of defoamer added to find the defoamer addition ratio that enables the hydrocyclone to achieve the best separation state (defined as the ratio of defoamer volume flow rate to slurry volume flow rate).

[0015] The criteria for optimal separation include: clear overflow from the hydrocyclone with no obvious solid particles, moderate viscosity of the underflow gypsum slurry, and a moisture content of the sample that is lower than the set target.

[0016] c) Model induction stage: Correlation analysis of all data pairs reveals a negative correlation between decreasing density and increasing defoamer ratio; based on data distribution characteristics and system control precision requirements, the density range is divided into several continuous control intervals, and an optimal defoamer addition ratio range is set for each interval.

[0017] Furthermore, the piecewise function model is specifically as follows:

[0018] When the density of the gypsum slurry is within the first density range, the defoamer addition ratio is 0.05% to 0.08% of the volumetric flow rate of the gypsum slurry, which is defined as the normal control zone.

[0019] When the density of the gypsum slurry is in the second density range, the defoamer addition ratio is 0.08% to 0.12% of the volumetric flow rate of the gypsum slurry, which is defined as the enhanced control zone;

[0020] When the density of the gypsum slurry is in the third density range, the defoamer addition ratio is 0.12% to 0.15% of the volumetric flow rate of the gypsum slurry, which is defined as a high foam risk zone and requires maximum foam suppression.

[0021] Wherein, the lower limit of the density of the first density interval is higher than the upper limit of the density of the second density interval, and the lower limit of the density of the second density interval is higher than the upper limit of the density of the third density interval.

[0022] Furthermore, the first density range is 1180 kg / m³ to 1130 kg / m³, the second density range is 1130 kg / m³ to 1100 kg / m³, and the third density range is 1050 kg / m³ to 1100 kg / m³.

[0023] Furthermore, the real-time addition of defoamer to the gypsum slurry is performed by an automatic control system; the automatic control system is configured to: receive the density signal of the gypsum slurry from an online densitometer, calculate the target defoamer addition ratio based on the dynamic correlation model, and control the metering pump to inject defoamer according to the target defoamer addition ratio.

[0024] The control system receives density signals from the online densitometer in real time. Based on the aforementioned dynamic correlation model, it quickly determines the control range to which the current density belongs and immediately outputs the corresponding defoamer addition ratio set value to the defoamer metering pump. The metering pump (usually a high-precision diaphragm pump) automatically adjusts its stroke frequency according to this set value and the real-time detected total slurry flow rate, precisely and continuously injecting the defoamer (preferably a high-efficiency organosilicon composite defoamer) into the hydrocyclone feed pipe or slurry tank, achieving on-demand distribution.

[0025] Furthermore, the automatic control system is a programmable logic controller system or a distributed control system.

[0026] Furthermore, the inlet pressure of the first-stage hydrocyclone is controlled within the range of 0.15MPa to 0.25MPa, preferably 0.18-0.22MPa, and the installation tilt angle is adjusted to 10° to 15°, preferably 12°±2°.

[0027] Inlet pressure: Controlled at 0.18-0.22 MPa to ensure sufficient separation force and processing capacity.

[0028] Installation tilt angle: Adjust the angle between the hydrocyclone axis and the horizontal plane to 12°±2°, which is conducive to the smooth discharge of the underflow and reduces blockage.

[0029] The optimized hydrocyclone operates in a low-foaming environment, allowing its inherent centrifugal separation efficiency to be fully utilized.

[0030] Furthermore, the defoamer is an organosilicon composite defoamer.

[0031] Furthermore, the method is applied to a desulfurization system for flue gas from anode carbon calcination.

[0032] Compared with existing technologies, the present invention provides a high-efficiency separation method for calcium-based desulfurization gypsum based on slurry density control. Through dynamic control, it achieves precise foam suppression, creating an excellent separation environment for the hydrocyclone, enabling efficient separation of gypsum crystals. It also effectively prevents frequent blockages and slurry leakage accidents in the hydrocyclone and subsequent pipelines caused by foam. At the same time, it changes the insufficient or excessive state caused by the traditional fixed addition, realizing the on-demand distribution of defoamer, reducing the total amount of reagents consumed while ensuring the effect, and saving operating costs. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0034] Figure 1 A flowchart illustrating the method steps provided in an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] As attached Figure 1 As shown:

[0037] Example 1:

[0038] This invention provides a highly efficient gypsum separation method based on slurry density control in calcium-based desulfurization. This method is applied to the calcination flue gas desulfurization system of an anode carbon plant. The method improves upon the gypsum discharge and dewatering unit of the traditional calcium-based desulfurization process. The system hardware mainly includes the following components:

[0039] Monitoring Unit: An online densitometer is installed on the pipeline between the outlet of the gypsum slurry discharge pump (or hydrocyclone feed pump) and the inlet of the first-stage hydrocyclone to continuously and in real-time measure the instantaneous density of the gypsum slurry during transportation. The output signal of the densitometer (4-20mA or Modbus protocol, etc.) is connected to the plant's distributed control system (DCS).

[0040] Control and execution unit: Includes an antifoaming agent storage tank, a high-precision mechanical diaphragm metering pump, and a dynamic control program module integrated into the DCS. The inlet of the metering pump is connected to the antifoaming agent storage tank, and the outlet is located in the gypsum slurry pump outlet pipe or slurry buffer tank via a pipeline injection point. The DCS system receives real-time density signals from an online density meter and signals from a slurry flow meter.

[0041] Separation unit: First-stage hydrocyclone assembly. Its operating parameters are pre-optimized: the inlet operating pressure of the hydrocyclone is stabilized within the range of 0.18-0.22 MPa by adjusting the pump frequency; its installation tilt angle (the angle between the axis and the horizontal plane) is adjusted to approximately 12°±2° to facilitate smooth discharge of underflow.

[0042] Original system conditions: gypsum moisture content 28%, purity 86%, hydrocyclone blocked once every 2 hours and overflowed twice during gypsum removal.

[0043] The method steps in this embodiment are as follows:

[0044] S1. Real-time monitoring: The online density meter continuously monitors the gypsum slurry flowing in the pipeline and transmits the continuous density signal to the DCS in real time. The normal density fluctuation range of the gypsum slurry is between 1050 kg / m³ and 1180 kg / m³, comprehensively reflecting the changes in the solid content, air bubble entrainment, and chemical composition of the slurry.

[0045] S2. Dynamically regulate the addition of defoamer:

[0046] a) Model Query: The control program module within the DCS has a preset piecewise function model. The program reads the density signal in real time and determines its corresponding density range.

[0047] If the density signal is ≥1130kg / m³, the program determines it to be in the first density range (1180-1130kg / m³), and the target addition ratio is set to 0.065% (the median value between 0.05% and 0.08%).

[0048] If 1100kg / m³ ≤ density signal < 1130kg / m³, the program determines it to be in the second density range (1130-1100kg / m³), and the target addition ratio is set to 0.10% (the median of 0.08%-0.12%).

[0049] If the density signal is <1100kg / m³, the program determines it to be in the third density range (1100-1050kg / m³), and the target addition ratio is set to 0.135% (the median of 0.12%-0.15%).

[0050] b) Dosage Calculation and Execution: The DCS synchronously reads the real-time volumetric flow rate (m³ / h) of the gypsum slurry. Based on the formula: Defoamer Required Flow Rate = Slurry Flow Meter Signal × Target Addition Ratio, the instantaneous target flow rate of the metering pump is calculated. The DCS then sends a control command (usually an analog signal or a pulse frequency signal) to the metering pump, driving it to precisely inject the defoamer (in this embodiment, a high-efficiency silicone composite defoamer) at the required flow rate. This process is a closed-loop, continuous, dynamic adjustment.

[0051] S3. High-efficiency solid-liquid separation: The gypsum slurry, treated online with defoamer, enters the primary hydrocyclone. Under optimized inlet pressure, the slurry acquires sufficient centrifugal force. Because foam is effectively suppressed, solid particles (gypsum crystals) efficiently move towards the hydrocyclone wall and settle in a clear liquid environment, discharging through the underflow outlet to form a high-concentration gypsum underflow slurry (with significantly reduced water content). The clear liquid (or overflow containing extremely fine particles) returns to the system from the top overflow outlet.

[0052] Results: After applying this embodiment, the system ran continuously for one month without any blockage or overflow of slurry in the primary hydrocyclone. Testing showed that the average moisture content of the produced desulfurized gypsum decreased steadily from 28% before the modification to below 12%, and the purity of the gypsum (calcium sulfate dihydrate content) increased from 86% to over 95%.

[0053] Working principle: Slurry density is a key indirect parameter reflecting its tendency to foam: a decrease in density often means a decrease in solid content or an increase in bubble content, making separation more difficult. Through a preset negative correlation dynamic model, the system can proactively and proportionally increase the amount of defoamer added before foaming problems appear (i.e., when the density decreases), achieving "preventive defoaming." Combined with the optimization of the hydrocyclone's own parameters, this ensures that the separation process always operates under efficient and stable conditions.

[0054] Example 2:

[0055] This embodiment is basically the same as the previous embodiment, except that the dynamic association model is established.

[0056] The model building steps are as follows:

[0057] Data acquisition preparation: During the stable operation of the target desulfurization system, cover its common operating conditions (different calciner loads, different raw material batches, etc.). Ensure that the online density meter, slurry flow meter, and defoamer metering pump are all calibrated and operating normally.

[0058] Manual optimization test: During each relatively stable operating period, record the average slurry density. Then, under this density background, manually adjust the output of the defoamer metering pump to change the addition ratio. Simultaneously, closely observe the operating status of the first-stage hydrocyclone and periodically sample and analyze the moisture content of the gypsum in the hydrocyclone underflow.

[0059] Determine the optimal ratio: For each density point, find the defoamer addition ratio that simultaneously satisfies the following two conditions:

[0060] Process conditions: The overflow from the hydrocyclone is clear and transparent, with no visible slurry leakage; the underflow discharge is smooth, without interruption or blockage.

[0061] Results conditions: After sampling and laboratory dehydration, the moisture content of the bottom flow gypsum slurry was found to be lower than the preset target value (15%).

[0062] This ratio is the empirically optimal addition ratio for this density.

[0063] Data Analysis and Model Fitting: A series of data pairs (average slurry density, defoamer addition ratio) were collected. Plotting these points on a coordinate system revealed a general trend (negative correlation) where the defoamer addition ratio increased as the average slurry density decreased. Based on the clustering of data points and considering the need for stability control in actual operation (avoiding frequent minor adjustments to the ratio), several continuous density intervals were defined. As shown in Example 1, cluster boundaries appeared near 1130 kg / m³ and 1100 kg / m³, naturally dividing the data into three intervals. Then, by taking the statistical range (mean ± standard deviation) of all defoamer addition ratio data within each interval, the corresponding defoamer addition ratio range (0.05%-0.08%) could be determined.

[0064] Determine model parameters: Perform statistical analysis on the data of each cluster region, select a reasonable range of proportion values, and finally determine the control model of the system as follows:

[0065] When the density signal is ≥1120kg / m³, the target addition ratio is 0.04%-0.07%.

[0066] When 1080 kg / m³ ≤ density signal < 1120 kg / m³, the target addition ratio is 0.07% - 0.11%.

[0067] When the density signal is <1080 kg / m³, the target addition ratio is 0.11%-0.16%.

[0068] Model implantation and verification: The established "density interval - proportional range" correspondence is programmed into the control logic of the DCS or PLC in the form of a lookup table or conditional statement. The effect is continuously observed during actual automatic operation, and boundary values ​​and proportional values ​​can be fine-tuned and optimized.

[0069] Results: The system operated smoothly, and the hydrocyclone separation effect was good. At the end of the validation period, the average moisture content of the underflow gypsum was 14.2%, which met the design target (<15%), confirming the reliability of the model.

[0070] Example 3:

[0071] This embodiment provides a highly efficient separation method for calcium-based desulfurization gypsum based on slurry density control. This method is applied to the flue gas desulfurization system of an anode carbon calcination process. This embodiment is basically the same as Embodiment 1, except that:

[0072] Field test modeling was performed according to the method in Example 2. Due to differences in slurry characteristics, the determined control model obtained is as follows:

[0073] When the density signal is ≥1140kg / m³, the target addition ratio is 0.06%-0.09%.

[0074] When 1090 kg / m³ ≤ density signal < 1140 kg / m³, the target addition ratio is 0.09% - 0.13%.

[0075] When the density signal is <1090kg / m³, the target addition ratio is 0.13%-0.18%.

[0076] Original system conditions: gypsum moisture content 35%, purity 81%, hydrocyclone blocked twice in 2 hours during gypsum removal process, overflowed slurry 3 times.

[0077] Results: After adopting this method, the system ran continuously for 30 days without any blockage or overflow during the gypsum removal process. It successfully reduced the gypsum moisture content from about 35% to below 20%, and increased the purity from 81% to over 90%. The stability of the hydrocyclone operation was greatly improved.

[0078] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A highly efficient separation method for calcium-based desulfurization gypsum based on slurry density control, characterized in that, include: S1. Real-time monitoring of the density of the gypsum slurry that is about to be transported to the first-stage hydrocyclone for solid-liquid separation in the calcium desulfurization system, and obtaining the density value; S2. Based on the preset dynamic correlation model between slurry density and defoamer addition ratio, and the density value, the target addition ratio is obtained, and defoamer is added to the gypsum slurry in real time according to the target addition ratio; the dynamic correlation model specifies the negative correlation control relationship between slurry density value and defoamer addition ratio; S3. The gypsum slurry with added defoamer is conveyed to a primary hydrocyclone for solid-liquid separation to obtain desulfurized gypsum.

2. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 1, characterized in that, The dynamic correlation model is a piecewise function model, which divides the slurry density into at least three continuous control intervals. Each control interval corresponds to an independent range of defoamer addition ratios, and the defoamer addition ratio range corresponding to the control interval with a lower density value is higher than that of the control interval with a higher density value.

3. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 2, characterized in that, The piecewise function model is specifically as follows: When the density of the gypsum slurry is within the first density range, the defoamer is added at a ratio of 0.05% to 0.08% of the volumetric flow rate of the gypsum slurry. When the density of the gypsum slurry is within the second density range, the defoamer is added at a ratio of 0.08% to 0.12% of the volumetric flow rate of the gypsum slurry. When the density of the gypsum slurry is in the third density range, the defoamer is added at a ratio of 0.12% to 0.15% of the volumetric flow rate of the gypsum slurry. Wherein, the lower limit of the density of the first density interval is higher than the upper limit of the density of the second density interval, and the lower limit of the density of the second density interval is higher than the upper limit of the density of the third density interval.

4. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 3, characterized in that, The first density range is 1180 kg / m³ to 1130 kg / m³, the second density range is 1130 kg / m³ to 1100 kg / m³, and the third density range is 1050 kg / m³ to 1100 kg / m³.

5. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 1, characterized in that, The real-time addition of defoamer to the gypsum slurry is performed by an automatic control system; the automatic control system is configured to: receive the density signal of the gypsum slurry from an online densitometer, calculate the target defoamer addition ratio based on the dynamic correlation model, and control the metering pump to inject defoamer according to the target defoamer addition ratio.

6. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 5, characterized in that, The automatic control system is a programmable logic controller system or a distributed control system.

7. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 1, characterized in that, The inlet pressure of the first-stage hydrocyclone is controlled within the range of 0.15MPa to 0.25MPa, and the installation tilt angle is adjusted to 10° to 15°.

8. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 1, characterized in that, The defoamer is an organosilicon composite defoamer.

9. The efficient separation method for calcium-based desulfurization gypsum based on slurry density control according to claim 1, characterized in that, The method is applied to the desulfurization system for flue gas from anode carbon calcination.

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