Desulfurization system and method for preparing low-water-content gypsum

Abstract

The invention provides a desulfurization system and method for preparing gypsum with low water content. The desulfurization system comprises a desulfurization unit and an oxidation unit, a spraying layer and a first slurry pool area in which desulfurization slurry is pre-stored are arranged in the desulfurization tower; the first pipeline is used for conveying the desulfurization slurry to the spraying layer to spray the flue gas to remove SO2; the first pulp pool area conveys the mixed pulp in the first pulp pool area to the second pulp pool area through a second pipeline; the oxygen supply equipment is used for conveying oxygen to the slurry in the second slurry pool area to generate gypsum crystals; and the slurry containing gypsum crystals after being oxidized in the second slurry pool area is conveyed to the first slurry pool area by the third pipeline. By controlling the pH values of the desulfurization tower slurry pool area and the oxidation tower slurry pool area and the slurry retention time, on the premise of ensuring the desulfurization efficiency, the gypsum is fully oxidized, the moisture content of the generated gypsum is reduced, and the later gypsum utilization rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wet desulfurization in cement industry, and more specifically to a desulfurization system and method for preparing low-water-content gypsum. Background Art

[0002] The desulfurizer of the wet desulfurization system in the cement industry is generally selected from the kiln dust of the kiln tail zipper machine or the kiln dust of the waste heat power generation zipper machine. The effective limestone content of this desulfurizer is only about 40%. Using kiln dust as a desulfurizer can achieve zero external purchase of desulfurizers for the wet desulfurization system, saving system operating costs. However, the disadvantage is that the moisture content of the dehydrated gypsum produced is high, up to more than 20%. There are two reasons for this:

[0003] 1. The high impurity content of kiln dust leads to high moisture content of gypsum. The limestone content in the kiln dust of the cement production line is about 40%, which contains many impurities, mostly fly ash, uneven particle size distribution, and small average particle size. It enters the dehydrated gypsum through the dehydration system, affecting the moisture content of the gypsum.

[0004] 2. Insufficient oxidation of desulfurization slurry leads to high moisture content of desulfurization gypsum. When the desulfurization system has a high inlet sulfur content for a long time and requires a large amount of desulfurizer slurry, the desulfurization slurry is not fully oxidized, resulting in high moisture content of desulfurization gypsum, which in severe cases causes slurry poisoning bubbles and other problems.

[0005] The moisture content of dehydrated gypsum is relatively high, resulting in poor quality and high viscosity of the gypsum. At this time, it can no longer be used as a cement retarder in the cement production line and can only be discarded as solid waste, increasing the operating cost of the desulfurization system.

[0006] The invention solves the problem of high moisture content of desulfurized gypsum in the desulfurization system, ensures that the moisture content of the desulfurized gypsum is 10%, and ensures stable operation of the desulfurization system. Summary of the invention

[0007] The present invention provides a desulfurization system and method for preparing gypsum with low water content, which are used to solve the problem of high water content of gypsum prepared by the desulfurization system in the prior art.

[0008] The present invention provides a desulfurization system for preparing low-water content gypsum, comprising a desulfurization tower and an oxidation tower;

[0009] The desulfurization tower is provided with a spray layer and a first slurry pool area pre-stored with desulfurization slurry; a first pipeline is provided between the first slurry pool area and the spray layer, and the first pipeline is used to transport the desulfurization slurry to the spray layer to spray the flue gas entering the desulfurization tower to remove SO2, and after spraying, the first slurry pool area contains a mixed slurry of the desulfurized slurry and the original desulfurized slurry;

[0010] The bottom of the oxidation tower is the second slurry pool area; the first slurry pool area transports the mixed slurry in the first slurry pool area to the second slurry pool area through the second pipeline; the second slurry pool area is provided with an oxygen supply device, and the oxygen supply device is used to transport oxygen to the slurry in the second slurry pool area to generate gypsum crystals; the second slurry pool area is connected to the desulfurization tower through the third pipeline, and the third pipeline is used to transport the slurry containing gypsum crystals after oxidation in the second slurry pool area to the first slurry pool area.

[0011] Optionally, it further comprises a dehydration unit and an external discharge unit, wherein the dehydration unit comprises a cyclone and a centrifuge, and the external discharge unit comprises a filtrate water tank;

[0012] The dewatering unit is connected to the second slurry pool area through a fourth pipeline, and the fourth pipeline is used to transport the gypsum slurry in the second slurry pool area to the cyclone for primary dehydration to obtain overflow and underflow; the overflow enters the filtrate water tank for storage; the outlet of the filtrate water tank goes to the raw material mill or the wastewater treatment system;

[0013] The centrifuge performs secondary dehydration on the bottom flow to obtain an upper layer of liquid and a lower layer of gypsum; the upper layer of liquid returns to the desulfurization tower by gravity.

[0014] Optionally,

[0015] The second pipeline and the third pipeline are both provided with a density meter and a pH meter, which are used to detect the pH and density of the slurry in the first pulp pool area and the second pulp pool area respectively.

[0016] Optionally, the oxidation tower wall is also provided with a valve;

[0017] When the desulfurization tower is operating normally, the valve is in an open state and serves as an overflow pipe;

[0018] When the desulfurization tower needs to be repaired, the valve is in a closed state, and the oxidation tower is used to store all the slurry in the first slurry pool area.

[0019] Optionally, the first pulp pool area and the second pulp pool area are both provided with pressure transmitters, and the liquid levels of the first pulp pool area and the second pulp pool area are monitored in real time by converting the pressure into the liquid level.

[0020] Optionally, the oxygen supply device includes an oxidation fan, an external oxidation air duct arranged outside the oxidation tower, and an internal oxidation air duct arranged inside the oxidation tower;

[0021] The oxidation fan is connected to the oxidation air duct outside the tower and the oxidation air duct inside the tower in sequence to deliver oxygen-containing air into the oxidation tower;

[0022] The oxidation air duct outside the tower includes a ring pipe, a first main air inlet pipe and a plurality of first branch pipes; the ring pipe includes a plurality of first branch pipes evenly installed on it; the air outlet of the oxidation fan is connected to the air inlet of the first main air inlet pipe, and the air outlet of the first main air inlet pipe is connected to the ring pipe;

[0023] The oxidation air duct in the tower includes a plurality of second main pipes connected to the plurality of first branch pipes respectively, each main pipe is connected to a plurality of second branch pipes, and the gas outlets of the plurality of second branch pipes are evenly distributed in the oxidation tower.

[0024] The present invention also provides a method for preparing low-water content gypsum, which is implemented based on the desulfurization system of the present invention, comprising:

[0025] The slurry in the first pulp pool area is transported to the spray layer to spray the flue gas and then falls into the first pulp pool area;

[0026] The slurry in the first slurry pool area is transported to the second slurry pool area of ​​the oxidation tower, and the oxygen supply equipment is turned on to supply oxygen to the second slurry pool area; when the slurry stays in the second slurry pool for more than a first time, the slurry in the second slurry pool area is transported to the first slurry pool area;

[0027] Monitoring and controlling the pH value of the slurry in the second pipeline to be a first pH value to ensure the desulfurization efficiency in the desulfurization tower;

[0028] The pH value of the slurry in the third pipeline is monitored and controlled to be a second pH value to ensure smooth generation of gypsum crystals in the oxidation tower.

[0029] Optionally, after the slurry in the first slurry pool area is transported to the second slurry pool area, the gypsum slurry can be discharged externally only when the density of the slurry in the second slurry pool area is a preset density and the residence time exceeds a second time length.

[0030] Optionally, the flow rates in the second pipeline and the third pipeline are less than or equal to the flow rate in the fourth pipeline.

[0031] Optionally,

[0032] The first time period is 24 hours, the first pH is 6 to 6.5, and the second pH is 4.5 to 5.5.

[0033] Optionally, the preset density is 1.12-1.16 g / cm 3 ;

[0034] The second time period is 14 to 18 hours. The present invention has at least the following beneficial effects:

[0035] The present invention provides a desulfurization system and method for preparing low-water-content gypsum, wherein a desulfurizer in a slurry pool area of ​​a desulfurization tower is used to spray flue gas to remove SO2, and the slurry after the reaction is passed into an external oxidation tower for oxidation, and at the same time, the gypsum crystal part generated after oxidation is transported to the slurry pool area of ​​the desulfurization tower. By controlling the pH of the slurry pool area of ​​the desulfurization tower and the slurry pool area of ​​the oxidation tower, as well as the slurry residence time, the gypsum is fully oxidized, the water content of the gypsum is reduced, and the utilization rate of the gypsum in the later stage is improved while ensuring the desulfurization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A schematic diagram of a desulfurization system for preparing low-water content gypsum provided in an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the arrangement of an external oxidation air duct structure provided by an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of the arrangement of a second main pipe in an oxidation tower provided in an embodiment of the present invention;

[0040] Figure 4 A schematic diagram of the arrangement of a second branch pipe in an oxidation tower provided in an embodiment of the present invention;

[0041] Reference numerals:

[0042] 1. Desulfurization tower; 1-1. First slurry pool area; 1-2. Spray layer; 1-3. Demister; 2. Oxidation tower; 2-1. Second slurry pool area; 2-2. Accident slurry area; 2-3. Oxygen supply device; 2-3-1. Oxidation air duct outside the tower; 2-3-1-1. First main pipe; 2-3-1-2. First branch pipe; 2-3-1-3. Ring pipe; 2-3-2. Oxidation air duct inside the tower; 2-3-2-1. Second main pipe; 2-3-2-2. Second branch pipe; 2-3-3. Outlet main pipe; 2-4. Valve; 3. First pipeline; 4. Second pipeline; 5. Third pipeline; 6. Fourth pipeline; 7. Circulation pump; 8. Gypsum discharge pump; 9. Agitator; 10. Pressure transmitter; 11. Density meter; 12. pH meter; 13. Filtrate water pump; 14. Cyclone; 15. Centrifuge; 17. Filtrate water tank. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The present invention provides a desulfurization system for preparing low-water content gypsum, comprising a desulfurization tower 1 and an oxidation tower 2;

[0045] The desulfurization tower 1 is provided with a spray layer 1-2 and a first slurry pool area 1-1 pre-stored with desulfurization slurry; a first pipeline 3 is provided between the first slurry pool area 1-1 and the spray layer 1-2, and the first pipeline 3 is used to transport the desulfurization slurry to the spray layer 1-2 to spray the flue gas entering the desulfurization tower 1 to remove SO2, and after spraying, the first slurry pool area 1-1 contains a mixed slurry of the desulfurized slurry and the original desulfurized slurry;

[0046] The bottom of the oxidation tower 2 is the second slurry pool area 2-1; the first slurry pool area 1-1 transports the mixed slurry in the first slurry pool area 1-1 to the second slurry pool area 2-1 through the second pipeline 4; the second slurry pool area 2-1 is provided with an oxygen supply device 2-3, and the oxygen supply equipment is used to transport oxygen to the slurry in the second slurry pool area 2-1 to generate gypsum crystals; the second slurry pool area 2-1 is connected to the desulfurization tower 1 through the third pipeline 5, and the third pipeline 5 is used to transport the slurry containing gypsum crystals after oxidation in the second slurry pool area 2-1 to the first slurry pool area 1-1.

[0047] Specifically, the bottom of the desulfurization tower 1 is the first slurry pool area 1-1, which is pre-stored with a desulfurizer, mainly limestone slurry. The slurry of the first slurry pool area 1-1 is transported to each spray layer 1-2 through the first pipeline 3, and the spray layer 1-2 is multi-layered. The desulfurizer sprayed from the spray layer 1-2 flushes the flue gas entering the desulfurization tower 1 from the air inlet. The first slurry pool area 1-1 has no oxygen supply equipment. The flue gas from the kiln tail enters the desulfurization tower 1 through the flue, and is fully washed by the desulfurization slurry sprayed downward. The desulfurized slurry falls to the slurry pool area. The flue gas continues to move upward and is intercepted by the demister 1-3. After the droplets are discharged from the outlet of the desulfurization tower 1, there are multiple demisters 1-3. At this time, the desulfurization tower 1 only guarantees the efficiency of the desulfurization system. The kiln tail flue gas containing SO2 fully contacts and reacts with the sprayed limestone slurry to generate calcium sulfite. The reaction equation is:

[0048] 2CaO+2SO2+H2O→CaSO3·1 / 2H2O (1)

[0049] The generated calcium sulfite is transported to the second pulp pool area 2-1 in the oxidation tower 2 through the second pipeline 4. The oxygen supply device supplies oxygen to the slurry in the second pulp pool area 2-1 to oxidize the reacted calcium sulfite into calcium sulfate. The reaction equation is:

[0050] CaSO3·1 / 2H2O+1 / 2O2+3 / 2H2O→CaSO4·2H2O (2)

[0051] The slurry containing gypsum crystals in the oxidation tower 2 enters the first slurry pool area 1-1 in the desulfurization tower 1 through the third pipeline 5. The gypsum crystals enter the first slurry pool area 1-1 as seeds to prevent the calcium sulfite in the desulfurization tower 1 from undergoing a reversible reaction and prevent the secondary generation of SO2.

[0052] The pH value is a key parameter for controlling the stable operation of the desulfurization system. The applicant has found that a pH value of the desulfurization slurry above 6 is beneficial to the desulfurization efficiency of the desulfurization system, but is not conducive to the formation of gypsum crystals. A pH value of about 5 is beneficial to the formation of gypsum crystals, but is not conducive to the desulfurization efficiency. Therefore, the present application separates the desulfurization part from the oxidation part, and while ensuring the desulfurization efficiency, a densely structured gypsum crystal can be obtained, and the moisture content of the gypsum obtained after production and treatment is less than 10%.

[0053] A plurality of stirrers 9 are provided in both the first slurry pool area 1 - 1 and the second slurry pool area 2 - 1 . The stirrers 9 are used to stir the various components in the slurry so as to evenly distribute the components, thereby improving the mixing efficiency.

[0054] In a possible embodiment, it further includes a dehydration unit and an external discharge unit, wherein the dehydration unit includes a cyclone 14 and a centrifuge 15, and the external discharge unit includes a filtrate water tank 17;

[0055] The dehydration unit is connected to the second slurry pool area 2-1 through a fourth pipeline 6, and the fourth pipeline 6 is used to transport the gypsum slurry of the second slurry pool area 2-1 to the cyclone 14 for primary dehydration to obtain overflow and underflow; the overflow enters the filtrate water tank 17 for storage; the outlet of the filtrate water tank 17 goes to the raw material mill or the wastewater treatment system;

[0056] The centrifuge 15 performs secondary dehydration on the bottom flow to obtain an upper layer of liquid and a lower layer of gypsum; the upper layer of liquid returns to the desulfurization tower 1 by gravity.

[0057] Specifically, the dehydration unit includes a cyclone 14 and a centrifuge 15, wherein the cyclone 14 is a hydrocyclone 14 and the centrifuge 15 is a gravity centrifuge 15. The impurities in the kiln dust of the cement production line are mostly fly ash, which has a light specific gravity and a small particle size. The mature gypsum has a heavy specific gravity and a large particle size. The hydrocyclone 14 can separate the gypsum with a larger and heavier particle size, and also perform a primary dehydration on the gypsum slurry. The fourth pipeline 6 uses the hydrocyclone 14 to classify the impurity slurry and gypsum crystals in the gypsum slurry with a concentration of about 15%. The bottom flow slurry of the cyclone 14 is concentrated to about 50% and sent to the centrifuge 15 through the gypsum bottom flow distributor. In order to avoid the enrichment of chloride ions and fly ash with a lighter specific gravity in the desulfurization slurry, the overflow of the hydrocyclone 14 enters the filtrate water tank 17. In addition, the enrichment of chloride ions will cause calcium ions to react preferentially with chloride ions to generate calcium chloride, which inhibits the formation of desulfurized gypsum. In addition, when the hydrocyclone 14 is running, if the diameter of the grit nozzle is too large or the inlet pressure is too low, impurities with a lighter specific gravity and smaller particle size will enter the bottom flow. Studies have shown that when selecting a grit nozzle for the desulfurization system of a cement production line, a grit nozzle with a diameter of less than 18 mm should be selected, and the inlet pressure of the hydrocyclone 14 should be controlled at 0.23 Mpa during operation. A stirrer 9 is also provided in the filtrate water tank 17.

[0058] The external discharge unit includes a filtrate water tank 17 and a filtrate water pump 13. In order to ensure the stable operation of the desulfurization system, the desulfurization system needs to discharge the slurry regularly. The functions of external discharge are: 1. The slurry overflowing from the cyclone 14 is mostly impurities with a lighter specific gravity. Such impurities are enriched in the desulfurization system and affect the water content of gypsum; 2. Chloride ions are enriched in the slurry of the desulfurization system, corroding the desulfurization equipment; 3. The kiln dust of the kiln tail zipper machine usually contains heavy metal ions and oil. The enrichment of these impurities will cause slurry poisoning.

[0059] The filtrate tank 17 is used to store the slurry overflowing from the cyclone 14. When the system is operating normally, the slurry in the filtrate tank 17 is transported to the raw material mill or wastewater treatment system through the filtrate pump 13. The water volume is controlled at 3m 3 / h. The function of the raw material mill is to spray water to cool down. In order to prevent the impurities in the desulfurized slurry from being enriched, the filtrate pump 13 needs to operate stably for a long time.

[0060] The bottom flow slurry after the cyclone 14 enters the gravity centrifuge 15, and uses centrifugal force to concentrate about 50% of the gypsum slurry into gypsum with a moisture content of 10%. The upper layer of the centrifuge 15 returns to the desulfurization system by gravity, and the lower layer of gypsum is recycled as a cement retarder.

[0061] In one possible implementation,

[0062] The second pipeline 4 and the third pipeline 5 are both provided with a density meter 11 and a pH meter 12, which are used to detect the pH and density of the slurry in the first pulp pool area 1-1 and the second pulp pool area 2-1 respectively.

[0063] In a possible implementation, the wall of the oxidation tower 2 is further provided with a valve 2-4;

[0064] When the desulfurization tower 1 is operating normally, the valves 2-4 are in an open state and serve as overflow pipes;

[0065] When the desulfurization tower 1 needs to be repaired, the valve 2-4 is in a closed state, and the oxidation tower 2 is used to store all the slurry in the first slurry pool area 1-1.

[0066] Specifically, the oxidation tower 2 also has the function of storing accident slurry. When the desulfurization system operates normally, the valve 2-4 is in an open state and acts as an overflow pipe. When the desulfurization tower 1 of the desulfurization system needs to be repaired or the slurry is discharged, the valve 2-4 is closed, and the space above the valve 2-4 in the oxidation tower 2 is the accident slurry area 2-2. The accident slurry in the desulfurization tower 1 is transported to the oxidation tower 2 through the second delivery pipeline. This function not only solves the problem of short residence time of desulfurized gypsum, but also reduces the one-time investment of the system, and fully displays the oxidation tower 2 and the accident tower without increasing the civil engineering foundation.

[0067] In a possible implementation, the first pulp pool area 1-1 and the second pulp pool area 2-1 are both provided with a pressure transmitter 10, which converts the liquid level by pressure to monitor the liquid level of the first pulp pool area 1-1 and the second pulp pool area 2-1 in real time.

[0068] In the present application, a circulation pump 7 is provided on the first pipeline 3, the second pipeline 4, and the third pipeline 5, and a gypsum discharge pump 8 is provided on the fourth pipeline 6. The circulation pump 7 and the gypsum discharge pump 8 respectively provide power for the slurry transportation in the corresponding pipelines. The internal circulation pump 7 and the gypsum discharge pump 8 have pipeline flushing water access points. When the system is shut down or the pump is switched, the pump body and the pipeline are flushed to prevent the slurry from being deposited in the pipeline and the pump body. The deposited slurry after flushing is discharged into the ditch.

[0069] In a possible implementation manner, the oxygen supply device 2-3 includes an oxidation fan, an external oxidation air duct 2-3-1 arranged outside the oxidation tower 2, and an internal oxidation air duct 2-3-2 arranged inside the oxidation tower 2;

[0070] The oxidation fan is connected to the oxidation air duct 2-3-1 outside the tower and the oxidation air duct 2-3-2 inside the tower in sequence to deliver oxygen-containing air into the oxidation tower 2;

[0071] The outer oxidation air duct 2-3-1 of the tower includes a ring pipe 2-3-1-3, a first main air inlet pipe and a plurality of first branch pipes 2-3-1-2; the ring pipe 2-3-1-3 includes a plurality of first branch pipes 2-3-1-2 evenly installed thereon; the air outlet of the oxidation fan is connected to the air inlet of the first main air inlet pipe, and the air outlet of the first main air inlet pipe is connected to the ring pipe 2-3-1-3;

[0072] The oxidation air duct 2-3-2 in the tower includes a plurality of second main pipes 2-3-2-1 respectively connected to the plurality of first branch pipes 2-3-1-2, each main pipe is connected to a plurality of second branch pipes 2-3-2-2, and the air outlets of the plurality of second branch pipes 2-3-2-2 are evenly distributed in the oxidation tower 2.

[0073] Specifically, when designing the oxidation unit, attention should be paid to the selection of the oxidation fan and the layout of the oxidation duct. Only with sufficient oxidation air and reasonable layout of the oxidation duct can you achieve twice the result with half the effort. For the oxidation fan: If the oxidation fan is too large, it will not only increase the one-time investment cost, but also increase the operating power consumption of the desulfurization system; if the oxidation fan is too small, it will affect the oxidation of calcium sulfite, and then affect the formation of gypsum, and it is difficult to ensure the moisture content of gypsum. For the oxidation duct: Reasonable selection and layout of the oxidation duct can ensure that the desulfurization slurry is fully and effectively in contact with the oxidation air, and ensure the stable operation of the oxidation tower 2. Unreasonable layout of the oxidation duct will cause the oxidation duct to be blocked or broken. In severe cases, the desulfurization system has to be shut down for maintenance, affecting the stable operation of the desulfurization system.

[0074] The factors to be considered in the theoretical calculation of the oxidation fan of the cement production line desulfurization system include:

[0075] Air volume: The effect of oxygen required after the reaction of alkaline substances with SO2 should be considered.

[0076] Pressure: The pipeline loss pressure caused by the pipeline should be considered.

[0077] Number of oxidation fans and layout of oxidation air ducts:

[0078] Number of oxidation fans: Two in total, one for use and one for backup.

[0079] like Figure 2As shown, the direction of the arrow is the direction of the air flow. The oxidation air duct 2-3-1 outside the tower is connected to the air outlet main pipes 2-3-3 of the two oxidation fans. The air inlet of each air outlet main pipe 2-3-3 is connected to the air outlet of the 1# oxidation fan or the air outlet of the 2# oxidation fan. The pipeline direction is in the direction of the oxidation tower 2. A ring pipe 2-3-1-3 is arranged outside the oxidation tower 2. The ring pipe 2-3-1-3 connects three first branch pipes 2-3-1-2. Each first branch pipe 2-3-1-2 has an air outlet. The air outlet of each first branch pipe 2-3-1-2 is connected to the air inlet of the second main pipe 2-3-2-1 in the oxidation tower 2. Electric valves are installed at the outlets of the two oxidation fans. Only the electric valve of the oxidation fan in operation is in the normally open mode, and the electric valve of the oxidation fan that is not in operation is in the normally closed mode. Under normal circumstances, only one oxidation fan is in operation. In order to reduce the impact of local resistance and resistance along the pipeline, the air outlets of the air outlet main pipes 2-3-3 of the two oxidation fans are connected to the air inlet of the first main pipe 2-3-1-1, and the air outlet main pipes 2-3-3 of the two oxidation fans are symmetrically arranged on both sides of the air inlet of the first main pipe 2-3-1-1. The elbow type at the internal connection of the air outlet main pipe 2-3-3 is consistent, and the air outlet of the first main pipe 2-3-1-1 is connected to the middle of the ring pipe 2-3-1-3. The flow rate of the first main pipe 2-3-1-1 should be controlled at 15-18m / s, the structural dimensions of each first branch pipe 2-3-1-2 are the same, and the flow rate of each first branch pipe 2-3-1-2 is controlled at 20-25m / s, that is, the flow rate of the first branch pipe 2-3-1-2 ≥ the flow rate of the first main pipe 2-3-1-1. To prevent pipeline corrosion caused by shutdown of the oxidation fan, the elevation of the oxidation air ring pipe 2-3-1-3 of oxidation tower 2 should be more than 0.5m higher than the elevation of the overflow port of oxidation tower 2, and the pipeline material from the oxidation fan outlet to the oxidation air ring pipe 2-3-1-3 of oxidation tower 2 is Q235B, and the three branch pipes from the oxidation air ring pipe 2-3-1-3 of oxidation tower 2 to the pipeline inside oxidation tower 2 are all made of 2507.

[0080] The form of the oxidation duct 2-3-2 in the oxidation tower 2 and the top view of the service area are as follows: Figure 3 As shown, S1, S2, and S3 of the three oxidation air ducts 2-3-2 in the tower are represented, and the service area S1=S2=S3, ensuring that each area of ​​the cross section of the oxidation tower 2 can receive oxygen-containing air. Each oxidation air duct 2-3-2 in the tower includes a second main pipe 2-3-2-1 and a plurality of second branch pipes 2-3-2-2 vertically arranged in the oxidation tower 2 and connected to the second main pipe 2-3-2-1. In order to ensure the uniformity of the tower oxidation air arrangement, the plurality of second branch pipes 2-3-2-2 on each second main pipe 2-3-2-1 are evenly spaced, as shown in FIG. Figure 4As shown. In order to ensure the uniformity of the flow rate and layout of the oxidation air duct 2-3-2 in the tower, the second main pipe 2-3-2-1 is arranged with a gradual change in diameter from the air inlet end to the other end. In order to ensure smooth mud discharge in the air duct, the second main pipe 2-3-2-1 is arranged at an angle between 5° and 10°. In order to ensure the same pressure at the end of each second branch pipe 2-3-2-2, the end of each second branch pipe 2-3-2-2 should be at the same height. At the same time, the second branch pipe 2-3-2-2 is evenly arranged vertically in the slurry pool area, and the flow rate in the second branch pipe 2-3-2-2 is controlled at 25-30m / s. Since the moisture content of the hot air at the outlet of the oxidation fan is relatively low, it will enter the oxidation tower 2 pipe network and there will be a dry-wet interface with the slurry. The blockage of the air duct generally starts here and continues to enrich until the air duct is completely blocked. In order to prevent such problems from happening, the hot air at the oxidation fan outlet should be cooled and humidified. The amount of humidification water is the amount of water required to convert the hot air into saturated wet flue gas.

[0081] When oxidation tower 2 is in operation, the oxidation fan should be turned on and the cooling and humidifying water valve of the oxidation air should be opened. To prevent the existence of a dry-wet interface between the oxidation air and the slurry, the amount of humidification water is the amount of water required to convert the oxidation air into saturated wet flue gas.

[0082] The present application also provides a method for preparing low-water content gypsum based on a desulfurization system, comprising:

[0083] The slurry in the first pulp pool area 1-1 is transported to the spray layer 1-2 to spray the flue gas and then falls into the first pulp pool area 1-1;

[0084] The slurry in the first slurry pool area 1-1 is transported to the second slurry pool area 2-1 of the oxidation tower 2, and the oxygen supply device is turned on to supply oxygen to the second slurry pool area 2-1; when the slurry stays in the second slurry pool for more than a first time, the slurry in the second slurry pool area 2-1 is transported to the first slurry pool area 1-1;

[0085] Monitor and control the pH value of the slurry in the second pipeline 4 to be a first pH value to ensure the desulfurization efficiency in the desulfurization tower 1;

[0086] The pH value of the slurry in the third pipeline 5 is monitored and controlled to be a second pH value to ensure smooth generation of gypsum crystals in the oxidation tower 2 .

[0087] Specifically, the pre-stored desulfurization slurry in the first pulp pool area 1-1 sprays the flue gas for desulfurization and then falls into the first pulp pool area 1-1 to generate calcium sulfite.

[0088] At the initial stage of system operation, the desulfurized slurry containing calcium sulfite in the desulfurization tower 1 is transported to the oxidation tower 2. After entering the oxidation tower 2, the slurry is fully oxidized by the oxidizing wind to form desulfurized gypsum. At the initial stage of system operation, the residence time of the slurry in the second slurry pool area 2-1 must exceed the first time length to ensure that the gypsum in the second slurry pool area 2-1 has grown into thick and dense gypsum crystals, which can be used as gypsum "seeds" for the oxidation tower 2. When the slurry in the second slurry pool area 2-1 has been running for more than the first time length, the slurry containing gypsum crystals is transported to the first slurry pool area 1-1 of the desulfurization tower 1 through the third pipeline 5.

[0089] The pH value of the slurry in the first slurry pool area 1-1 is monitored and controlled to be at the first pH to ensure the desulfurization efficiency in the desulfurization tower 1. The pH value of the slurry in the second slurry pool area 2-1 is monitored and started to be at the second pH to allow the gypsum crystals to be generated smoothly.

[0090] In a possible implementation, after the slurry in the first slurry pool area 1-1 is transported to the second slurry pool area 2-1, the gypsum slurry can be discharged externally only when the density of the slurry in the second slurry pool area 2-1 reaches a preset density and the residence time exceeds a second time length.

[0091] Specifically, the residence time of the slurry in the second slurry pool area 2-1 is a dynamic equilibrium time for gypsum crystallization. The formation of new crystal seeds and crystal growth occur simultaneously. Only when the residence time exceeds a certain value can the desulfurized gypsum be discharged. Therefore, when the system is running, the residence time of the slurry in the oxidation tower 2 must be greater than the second time to ensure that the desulfurized gypsum is fully oxidized.

[0092] In a possible implementation manner, the flow rates in the second pipeline 4 and the third pipeline 5 are less than or equal to the flow rate in the fourth pipeline 6 .

[0093] Specifically, in order to ensure that the desulfurized gypsum slurry in the second slurry pool area 2 - 1 has sufficient residence time and the gypsum is fully oxidized, the flow rates in the second pipeline 4 and the third pipeline 5 shall not be greater than the flow rate in the fourth pipeline 6 .

[0094] In one possible implementation,

[0095] The first time period is 24 hours, the first pH is 6 to 6.5, and the second pH is 4.5 to 5.5.

[0096] Specifically, the main function of the desulfurization tower 1 is the desulfurization function. The pH value control parameter at 6-6.5 is conducive to the absorption of SO2 and ensures the emission of SO2 at the outlet of the desulfurization tower 1. The main function of the oxidation tower 2 is to oxidize gypsum. The pH value control parameter at 4.5-5.5 is conducive to the formation of gypsum.

[0097] In a possible implementation, the preset density is 1.12-1.16 g / cm 3 ;

[0098] The second duration is 14 to 18 hours.

[0099] Specifically, when the density of the slurry in the oxidation tower 2 is between 1.12 and 1.16 g / cm 3 After a sufficient residence time, the slurry in the second pulp pool area 2-1 can be discharged into the dewatering unit. The optimal second duration is 16 hours.

[0100] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0101] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A desulfurization system for preparing low-water content gypsum, characterized in that: Including desulfurization tower and oxidation tower; The desulfurization tower is provided with a spray layer and a first slurry pool area pre-stored with desulfurization slurry; a first pipeline is provided between the first slurry pool area and the spray layer, and the first pipeline is used to transport the desulfurization slurry to the spray layer to spray the flue gas entering the desulfurization tower to remove SO2, and after spraying, the first slurry pool area contains a mixed slurry of the desulfurized slurry and the original desulfurized slurry; The bottom of the oxidation tower is the second slurry pool area; the first slurry pool area transports the mixed slurry in the first slurry pool area to the second slurry pool area through the second pipeline; the second slurry pool area is provided with an oxygen supply device, and the oxygen supply device is used to transport oxygen to the slurry in the second slurry pool area to generate gypsum crystals; the second slurry pool area is connected to the desulfurization tower through the third pipeline, and the third pipeline is used to transport the slurry containing gypsum crystals after oxidation in the second slurry pool area to the first slurry pool area.

2. A desulfurization system for preparing low-water content gypsum according to claim 1, characterized in that: It also includes a dehydration unit and an external discharge unit, wherein the dehydration unit includes a cyclone and a centrifuge, and the external discharge unit includes a filtrate water tank; The dewatering unit is connected to the second slurry pool area through a fourth pipeline, and the fourth pipeline is used to transport the gypsum slurry in the second slurry pool area to the cyclone for primary dehydration to obtain overflow and underflow; the overflow enters the filtrate water tank for storage; the outlet of the filtrate water tank goes to the raw material mill or the wastewater treatment system; The centrifuge performs secondary dehydration on the bottom flow to obtain an upper layer of liquid and a lower layer of gypsum; the upper layer of liquid returns to the desulfurization tower by gravity.

3. A desulfurization system for preparing low-water content gypsum according to claim 1, characterized in that: The second pipeline and the third pipeline are both provided with a density meter and a pH meter, which are used to detect the pH and density of the slurry in the first pulp pool area and the second pulp pool area respectively.

4. A desulfurization system for preparing low-water content gypsum according to claim 1, characterized in that: The oxidation tower wall is also provided with a valve; When the desulfurization tower is operating normally, the valve is in an open state and serves as an overflow pipe; When the desulfurization tower needs to be repaired, the valve is in a closed state, and the oxidation tower is used to store all the slurry in the first slurry pool area.

5. A desulfurization system for preparing low-water content gypsum according to claim 1, characterized in that: The first pulp pool area and the second pulp pool area are both provided with pressure transmitters, which convert the liquid level by pressure to monitor the liquid level of the first pulp pool area and the second pulp pool area in real time.

6. A desulfurization system for preparing low-water content gypsum according to claim 1, characterized in that: The oxygen supply device includes an oxidation fan, an external oxidation air duct arranged outside the oxidation tower, and an internal oxidation air duct arranged inside the oxidation tower; The oxidation fan is connected to the oxidation air duct outside the tower and the oxidation air duct inside the tower in sequence to deliver oxygen-containing air into the oxidation tower; The oxidation air duct outside the tower includes a ring pipe, a first main air inlet pipe and a plurality of first branch pipes; the ring pipe includes a plurality of first branch pipes evenly installed on it; the air outlet of the oxidation fan is connected to the air inlet of the first main air inlet pipe, and the air outlet of the first main air inlet pipe is connected to the ring pipe; The oxidation air duct in the tower includes a plurality of second main pipes connected to the plurality of first branch pipes respectively, each main pipe is connected to a plurality of second branch pipes, and the gas outlets of the plurality of second branch pipes are evenly distributed in the oxidation tower.

7. A method for preparing low-water content gypsum, characterized in that: The desulfurization system according to any one of claims 1 to 6 is implemented, comprising: The slurry in the first pulp pool area is transported to the spray layer to spray the flue gas and then falls into the first pulp pool area; The slurry in the first slurry pool area is transported to the second slurry pool area of ​​the oxidation tower, and the oxygen supply equipment is turned on to supply oxygen to the second slurry pool area; when the slurry stays in the second slurry pool for more than a first time, the slurry in the second slurry pool area is transported to the first slurry pool area; Monitoring and controlling the pH value of the slurry in the second pipeline to be a first pH value to ensure the desulfurization efficiency in the desulfurization tower; The pH value of the slurry in the third pipeline is monitored and controlled to be a second pH value to ensure smooth generation of gypsum crystals in the oxidation tower.

8. A method for preparing low-water content gypsum according to claim 7, characterized in that: After the slurry in the first slurry pool area is transported to the second slurry pool area, the gypsum slurry can be discharged out only when the density of the slurry in the second slurry pool area is a preset density and the residence time exceeds the second time length.

9. A method for preparing low-water content gypsum according to claim 7, characterized in that: The flow rates in the second pipeline and the third pipeline are less than or equal to the flow rate in the fourth pipeline.

10. The method for preparing low-water content gypsum according to claim 7, characterized in that: The first time period is 24 hours, the first pH is 6 to 6.5, and the second pH is 4.5 to 5.

5.

11. A method for preparing low-water content gypsum according to claim 8, characterized in that: The preset density is 1.12-1.16 g / cm 3 ; The second duration is 14 to 18 hours.

Images