A control method for the poisoning of calcium-based desulfurization gypsum slurry

Abstract

The present invention belongs to the technical field of flue gas desulfurization, and in particular relates to a control method for poisoning of calcium-based desulfurized gypsum slurry, which includes the following steps: S1, measure 100-300 ml of fatty alcohol polyoxyethylene ether and add it to the sump, stir and then pump it into the desulfurization tower; S2, measure 200-500 ml of polyether defoamer and mix it with water and stir, add it to the sump 20 minutes after the fatty alcohol polyoxyethylene ether is pumped into the desulfurization tower, and then pump it into the desulfurization tower; S3, control the density of the desulfurized slurry at 1115-1130 kg / m3; S4, keep the density of the limestone slurry in the pulping tank at 1170-1180 kg / m3, and the pH value at 11-12, continuously add it to the sump through a pipeline, continuously supply the slurry to the desulfurization tower through a sump pump, and maintain the pH value of the slurry in the desulfurization tower at 5.0-5.3; S5, start the gypsum slurry discharge pump to discharge the slurry in the desulfurization tower to a vacuum belt filter. The process method of adding fatty alcohol polyoxyethylene ether (AEO) and polyether defoamer increases the activity of the slurry, improves the poisoning of the slurry caused by high tar and asphalt content and the situation of excessive SO2, solves the problem that the gypsum is in a muddy state, and makes the water content of the finished gypsum less than 15%.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas desulfurization, and particularly relates to a method for controlling the poisoning of calcium-based desulfurization gypsum slurry. Background Art

[0002] In technical fields such as flue gas desulfurization, especially in the calcium-based desulfurization system for anode baking flue gas, due to the low flue gas temperature and high tar content in the flue gas, a large amount of tar, carbon powder, and fluoride are contained in the gypsum slurry during desulfurization. During operation, the content of impurities and tar increases, resulting in the poisoning of the desulfurization system slurry. The requirement for the tar pitch content in the flue gas entering the desulfurization tower is low, and a large amount of desulfurized wastewater needs to be discharged regularly to keep the anode baking desulfurization slurry active, meet the desulfurization efficiency, and the gypsum reach normal indicators. The increase in tar and impurities in the slurry easily leads to inactivity of the slurry, non-compliance of SO2 emissions, foaming of the slurry, false high level of the desulfurization tower liquid level, and inability to dehydrate the gypsum sludge. The above phenomena are collectively referred to as the poisoning of gypsum slurry.

[0003] The conventional method for treating slurry poisoning is to first stop the flue gas of the roasting furnace, then stop the desulfurization system, drain all the poisoned slurry in the desulfurization tower, and then re-prepare a new limestone slurry and restart the desulfurization system. Only when the slurry is completely replaced and remains active can the desulfurization effect be achieved. Or a large amount of poisoned sludge-like gypsum is discharged, and desulfurization agents are continuously added in the short term to reduce the SO2 emission value in the flue gas. In this process, overfeeding of slurry is likely to occur, and the slurry operates at a high density, and ultimately slurry poisoning cannot be avoided.

[0004] In addition, it is required that the anode roasting furnace operates continuously. Either two desulfurization towers are built, one for standby. Taking the construction of two desulfurization towers with standby as an example, the cost of one desulfurization tower is high, the site cannot be satisfied, the construction period is long, and the operation cost is high. The method of replacing the poisoned slurry and discharging a large amount of wastewater to solve the slurry poisoning, although the shutdown disposal time is short, and the desulfurization can meet the short-term stable operation after the slurry replacement, but with the increase in the impurity content of the slurry, secondary slurry poisoning cannot be avoided. Long-term and large-scale discharge of sludge-like gypsum and desulfurized wastewater, the gypsum cannot be transported and stored, and the desulfurized wastewater needs to be invested in wastewater treatment equipment. This method can be used as an emergency when the SO2 emissions do not meet the standards, but it is not suitable for continuous production processes and cannot meet the anode calcium-based flue gas desulfurization process.

[0005] The Chinese invention patent with the publication number of "CN111330316A" discloses a method for defoaming limestone slurry in the limestone-wet flue gas desulfurization absorption tower of a thermal power plant based on a desulfurization defoamer. Under the condition of relatively stable operating load, record the relevant operating parameters of the FGD. After 4 hours, start the addition work of the special desulfurization defoamer for the experiment; when the desulfurization rate is qualified and the pH value is between 5.0 and 5.6, keep the number of operating slurry circulation pumps; determine the input amount of the defoamer according to the operating conditions such as the flue gas volume at the inlet of the desulfurization system, the flue gas dust content, the boiler oil injection amount, and the inlet SO2 concentration; add 0.5 kg - 3 kg of the special desulfurization defoamer into the sump, stir for 5 minutes - 10 minutes, and then pump it into the absorption tower through the sump pump of the absorption tower. The invention is mainly applied to the defoaming of limestone slurry in the limestone-wet flue gas desulfurization absorption tower of thermal power plants, municipal coal-fired heating units, steel mills, and coking plants. When the flue gas scours the limestone slurry, a large amount of foam will be generated. The foam wraps and carries impurities such as unreacted SO2 gas, SiO2 particles, undissolved limestone particles, and gypsum crystals. At the same time, inevitably, a part of SO2 does not react with the limestone solution and directly escapes with the flue gas, resulting in a decrease in desulfurization efficiency and even exceeding the SO2 emission standard.

[0006] Problems existing in the prior art:

[0007] (1) Using the above operation method, the wet desulfurization gypsum of anode baking flue gas can eliminate the foaming of the slurry and improve some slurry conditions. However, since a large amount of tar accumulates in the slurry, the fundamental problem has not been solved, the poisoning situation of the slurry has not improved, the water content is still high during gypsum dehydration, and finally the gypsum product still contains a large amount of water, and it is impossible to produce dry and loose gypsum with a water content lower than 15%.

[0008] (2) The difficulty in solving the above technical problems lies in that a large amount of dehydration and slurry replacement are required during the adjustment of the slurry in the prior art. A large amount of sludge-like gypsum and waste slurry are discharged during the process, and even all the slurry in the tower is discharged and discarded when the tower is stopped, which is difficult to handle. Summary of the Invention

[0009] In view of the technical problems existing in the background art, the present invention provides a control method for the poisoning of calcium-based desulfurization gypsum slurry.

[0010] To achieve the above object, the technical solution provided by the present invention is as follows:

[0011] A control method for the poisoning of calcium-based desulfurization gypsum slurry, comprising the following steps:

[0012] S1, measure 100 - 300 ml of fatty alcohol polyoxyethylene ether, continuously add it to the sump in small amounts under stirring conditions, start the sump pump to pump it into the desulfurization tower reactor after stirring for 10 - 30 minutes;

[0013] S2, Measure 200 - 500 ml of polyether defoamer and mix it with 50 L of water in a container. Stir well for 15 - 30 minutes to disperse the polyether defoamer, and connect the dosing pump for standby;

[0014] S3, After the fatty alcohol polyoxyethylene ether is pumped into the desulfurization tower for 20 minutes, start the dosing pump to continuously add the diluted polyether defoamer to the sump while adjusting the addition amount;

[0015] S4, Keep the sump stirrer and the sump pump running normally, and pump the sump mixed slurry containing polyether defoamer into the desulfurization tower;

[0016] S5, Keep the density of the limestone slurry in the pulping tank at 1170 - 1180 kg / m 3 , with a pH value of 11 - 12. Continuously add it to the sump through a gravity flow pipeline, and continuously supply the slurry to the desulfurization tower reactor through the sump pump, and maintain the pH value of the slurry in the desulfurization tower at 5.0 - 5.3 and the density of the desulfurization slurry at 1115 - 1130 kg / m 3 ;

[0017] S6, Start the vacuum belt filter press, control the speed at 25 - 32 Hz, start the gypsum slurry discharge pump to discharge the slurry in the desulfurization tower to the vacuum belt filter press for dehydration, and produce gypsum with a moisture content of less than 30% after the slurry is dehydrated; During the dehydration process, the sump pump continuously supplies slurry to maintain the liquid level in the desulfurization tower unchanged.

[0018] Preferably, S7, after step S6, 50% of the wastewater pumped out by the vacuum pump is recycled for secondary dehydration in the vacuum belt filter press, and 50% is discharged to the filtration pond, and after precipitation, it is discharged into the cooling tower three - stage sedimentation pond for use as flue gas cooling water.

[0019] Preferably, a hydrocyclone is provided between the slurry discharge pump and the vacuum belt filter press, and the pressure of the hydrocyclone is 0.2 - 0.3 MPa.

[0020] Preferably, S8, after step S7, during the gypsum dehydration process, when the moisture content of the gypsum is greater than 15%, re - prepare 1 L of polyether defoamer, stir it evenly with 50 L of water, start the dosing pump and continuously spray it into the underflow slurry of the hydrocyclone at 5 L / h in a continuous atomized manner, and directly enter the vacuum belt filter press. After the slurry is dehydrated, the produced gypsum has a moisture content of less than 15%.

[0021] Preferably, the control method for the poisoning of the calcium - based desulfurization gypsum slurry includes a desulfurization system. The desulfurization system includes a desulfurization tower, and the desulfurization tower is connected with a return pipe leading to the sump. A densitometer and a pH value measuring device are sequentially arranged on the return pipe.

[0022] Preferably, the upper end of the return pipe is connected with a back - flushing water pipe.

[0023] Preferably, a separation pipe one with a high solid content and a separation pipe two with a low solid content are provided at the outlet of the hydrocyclone. The separation pipe one is connected to a vacuum belt filter, and the separation pipe two is connected to a sump.

[0024] Preferably, in step S1, the fatty alcohol polyoxyethylene ether is 300 ml, and the stirring reaction time is 10 minutes; in step S2, the polyether defoamer is 500 ml, and the stirring reaction time is 30 minutes.

[0025] The present invention has the following advantages and beneficial effects:

[0026] Compared with the slurry without adding fatty alcohol polyoxyethylene ether (AEO) for oil removal and adding polyether defoamer, the method of adding fatty alcohol polyoxyethylene ether (AEO) and polyether defoamer in the present invention increases the activity of the slurry, reduces the poisoning situation, can improve the gypsum output product, and its water content is significantly reduced. It is extremely dry visually, there is no muddy state, and the water content can be below 15%. Further verification shows that its performance meets the poisoning of the slurry caused by high tar asphalt content. By changing the operation mode and comparing the slurry with added fatty alcohol polyoxyethylene ether (AEO) and polyether defoamer with the poisoned slurry without changing the operation method and without addition, the poisoned slurry can solve the problem of excessive SO2 through this method, and the gypsum can reach the standard for dehydration.

[0027] According to the feedback of the tar content in the slurry, fatty alcohol polyoxyethylene ether (AEO) is added to remove the tar in the slurry in the absorption tower, and the foam generated by the reaction is removed using polyether defoamer. The tar is discharged with the desulfurized gypsum and wastewater; the liquid level height and pH value are accurately controlled, and the slurry density in the desulfurization tower is accurately controlled to operate at a lower density, effectively controlling the slurry poisoning caused by excessive slurry supply and frequent pH fluctuations. Description of the Drawings

[0028] Figure 1 is the calcium-based desulfurization process flow provided by the present invention Figure 1 ;

[0029] Figure 2 is the calcium-based desulfurization process flow provided by the present invention Figure 2 ;

[0030] Figure 3 is the flow chart of the control method for the poisoning of calcium-based desulfurization gypsum slurry provided by the present invention;

[0031] Figure 4 is a schematic diagram of the muddy gypsum produced before optimizing the process;

[0032] Figure 5 is a schematic diagram of the qualified loose gypsum produced after optimizing the process;

[0033] Icons: 1 - Full evaporation spray cooling tower, 11 - Electrostatic tar precipitator, 12 - Induced draft fan, 2 - Desulfurization tower, 21 - Demisting device, 22 - Spraying device, 23 - Desulfurization circulation pump, 3 - Process water tank, 31 - Process water pump, 32 - Backwash water pipe, 4 - Hopper, 41 - Pulping tank, 42 - Gravity flow pipe, 5 - Emergency pond, 51 - Emergency pump, 6 - Sump, 61 - Sump pump, 62 - Pulp supply pipe, 63 - Pipe 1, 7 - Valve, 71 - Hydrocyclone, 72 - Separation pipe 1, 73 - Separation pipe 2, 74 - Slurry tank, 75 - Gypsum slurry discharge pump, 76 - Chemical dosing pump, 8 - Return pipe, 81 - pH measuring device, 9 - Vacuum belt filter press, 91 - Vacuum pump, 92 - Pipe 2, 93 - Filter tank, 94 - Filtrate recovery pump, 95 - Pipe 3, 96 - Pipe 4. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention.

[0035] Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0036] Embodiment

[0037] The present invention provides a method for controlling the poisoning of calcium-based desulfurization gypsum slurry. Specifically, it is a method for preventing the poisoning of limestone slurry in the limestone-wet flue gas desulfurization absorption tower for anodic baking calcium-based desulfurization (flue gas purification for aluminum carbon anodic baking).

[0038] The specific technical solution is as follows:

[0039] (I) Layout of calcium-based desulfurization process

[0040] As Figure 1 shown, the calcium-based desulfurization process device includes a full evaporation spray cooling tower 1, an electrostatic tar precipitator 11, an induced draft fan 12, a desulfurization tower 2 purification system, etc. The anodic baking flue gas (flue gas volume 200000 m 3 / h) enters the desulfurization tower 2 purification system after passing through the full evaporation spray cooling tower 1, the electrostatic tar precipitator 11 and the induced draft fan 12, and the desulfurization and defluorination purification system is arranged in a positive pressure manner.

[0041] As Figure 2As shown in the figure, the flue gas desulfurization system includes a desulfurization tower 2, a spraying device 22, a demisting device 21, etc. The desulfurization tower 2 operates with 3 layers of spraying, and 1 layer of spraying position is reserved. The coverage area of each layer reaches 200%, and the spraying liquid is supplied by one or more professional desulfurization circulating pumps 23. The demisting device 21 is placed above the spraying device 22, and the flue gas is discharged from the top chimney after being demisted by the demisting device 21.

[0042] In the present invention, the desulfurization process adopts the limestone-gypsum method. The flue gas enters the desulfurization tower 2 for desulfurization after passing through the electrocatalytic tar precipitator 11.

[0043] Principle of limestone-gypsum wet flue gas desulfurization:

[0044] (1)SO2+H2O→H2SO3 Absorption (2)CaCO3+H2SO3→CaSO3+CO2+H2O Neutralization (3)CaSO3+1 / 2O2→CaSO4 Oxidation (4)CaSO3+1 / 2H2O→CaSO3•1 / 2H2O Crystallization (5)CaSO4+2H2O→CaSO4•2H2O Crystallization (6)CaSO3+H2SO3→Ca(HSO3)2 pH Control

[0045] The normal operation of the equipment meets the requirements of sulfur dioxide emission < 100mg / Nm 3 , hydrogen fluoride emission < 3mg / Nm 3 , particulate matter emission < 30mg / Nm 3 Requirements.

[0046] (II) Process of calcium-based desulfurization subsystem

[0047] As Figure 2 shown, the desulfurization system includes components such as a desulfurization tower 2, a sump 6, a sump pump 61, a chemical dosing pump 76, a feed tank 4, a pulping tank 41, a process water tank 3, an accident pool 5, pipes and valves. The reaction kettle components inside the desulfurization tower 2: a stirrer is provided on the side to stir the slurry at the bottom of the desulfurization tower 2; an air distribution device, a Venturi rod grid, a spraying layer, a tube-type distribution device, etc.

[0048] As Figure 2 shown, the lime slurry preparation system: includes a limestone powder storage tank 4, a pulping tank 41, a stirrer, a gravity pipe 42, a valve, etc. The sulfur agent uses limestone, and the content of limestone (CaCO3) > 90%; particle size: the passing rate of 250 mesh sieve > 90%. The feed tank 4 is connected to the pulping tank 41 through a feeder, and a gravity pipe 42 leading to the sump 6 is provided at the bottom end of the pulping tank 41, and a valve is provided on the gravity pipe 42 to control the flow rate of the self-flowing lime slurry.

[0049] As Figure 2As shown in the figure, the gypsum dehydration system includes: gypsum hydrocyclone 71, vacuum belt filter press 9, filter cloth flushing water tank, filter cloth flushing water pump, vacuum pump 91, filtration tank 93, mixer, filtrate recovery pump 94, pipelines and valves, etc.

[0050] As Figure 2 shown in the figure, the pulping tank 41 is connected to the pit 6 through a gravity flow pipe 42; inside the pit 6, it is connected to the desulfurization tower 2 through a pulp supply pipe 62. A pit pump 61 is provided on the pulp supply pipe 62. The pulp supply pipe 62 can directly lead into the desulfurization tower 2 or be connected to the spraying device 22; a slurry return pipe 8 is connected between the bottom of the desulfurization tower 2 and the pit 6. A densitometer and a pH measuring device 81 are successively installed on the return pipe. A pH measuring device 81 (low point) is provided on the return pipe 8 on the side of the pit 6, and a backwashing pipe 32 (high point) is provided at the upper end of the return pipe 8.

[0051] As Figure 2 shown in the figure, the bottom end of the desulfurization tower 2 is successively connected to a gypsum slurry discharge pump 75, a hydrocyclone 71, a slurry tank 74, and a vacuum belt filter press 9 through pipelines. A hydrocyclone 71 is provided between the gypsum slurry discharge pump 75 and the slurry tank 74. The pressure of the hydrocyclone 71 is 0.2 - 0.3 MPa, which is used for the first solid-liquid separation of the slurry; a separation pipe one 72 with a high solid content and a separation pipe two 73 with a low solid content are provided at the bottom end of the hydrocyclone 71. That is, the slurry with a high solid content flows through the separation pipe one 72 to the vacuum belt filter press 9, and the slurry with a low solid content flows through the separation pipe two 73 to the pit 6. The first fixed separation provides a prerequisite for gypsum dehydration, improves the solid content, and at the same time, the slurry with a low solid content is recycled back to the pit for continuous utilization. The dosing pump 76 is connected through pipelines and valves 7, and the valves 7 are respectively connected to the pit 6 and the underflow slurry of the hydrocyclone 71; the vacuum belt filter press 9 extracts wastewater through the vacuum pump 91. The vacuum pump 91 is connected to the slurry tank 74 and the filtration tank 93 through pipeline two 92. 50% of the wastewater extracted by the vacuum pump 91 is recycled into the vacuum belt filter press 9 for secondary dehydration, and 50% is discharged to the filtration tank 93; the gypsum after dehydration by the vacuum belt filter press 9 enters the gypsum warehouse for collection.

[0052] As Figure 2 shown in the figure, this process further includes a process water tank 3. A process water pump 31 is connected to the pipeline of the process water tank 3. One branch of the process water pump 31 is connected to the backwashing water pipe 32, and the other pipeline leads to the demisting device 21; the other pipeline leads to the pulping tank 41. Multiple backwashing water pipes 32 are provided, which are used for flushing the emergency pump 51, for flushing the pit pump 61, for flushing the gypsum slurry discharge pump 75, for flushing the desulfurization circulation pump 23, and for flushing the densitometer and the pH measuring device 81 on the return pipe 8.

[0053] As Figure 2As shown, the process also includes an accident pool 5, which is connected to the desulfurization tower 2 through a pipeline and is provided with an accident pump 51 to prevent the slurry in the desulfurization tower 2 from being poisoned and to take operations such as slurry extraction and replacement.

[0054] like Figure 2 As shown, a plurality of pipes 63 are provided on the slurry supply pipe 62 , wherein the pipe 63 is used to lead to the accident pool 5 , and the pipe 63 is used to lead to the slurry making tank 41 .

[0055] like Figure 2 As shown, the vacuum pump 91 is connected to the slurry tank 74 through the pipeline 92, and is connected to the filter tank 93 through the pipeline. 50% of the waste water extracted by the vacuum pump 91 is recycled into the vacuum belt dehydrator 9 for secondary dehydration, and 50% is discharged to the filter tank 93. A filtrate recovery pump 94 is provided on the filter tank 93, and the filtrate recovery pump 94 circulates back to the desulfurization tower 2 through the pipeline 96, and the rest is used to pass through the pipeline 95 to the pit 6, the accident pool 5, and the slurry tank 41, so as to realize the full circulation of water resources.

[0056] (III) Operation control process

[0057]

[0058] During the desulfurization process, the slurry density in the desulfurization tower 2 and the pit 6 is controlled to be: 1115-1130kg / m 3 During the gypsum dehydration process, the slurry is continuously supplied to the desulfurization tower 2 through the pit pump 61 to maintain the liquid level of the desulfurization tower 2 at 6.5-7m; the pH of the slurry in the desulfurization tower 2 is supplied by the limestone slurry tank and controlled at 5.0-5.3; the slurry density of the limestone slurry is: 1170-1190kg / m 3 By controlling the slurry density, pH value, etc., the final flue gas emission through the desulfurization tower is controlled to: SO2<100mg / Nm 3 , HF emission <3mg / Nm 3 , particulate matter emission <30mg / Nm 3 .

[0059] like Figure 4 As shown, a method for controlling poisoning of calcium desulfurization gypsum slurry comprises the following steps:

[0060] S1, measure 100-300 ml of fatty alcohol polyoxyethylene ether, and add it into the pit 6 in small amounts under stirring. After stirring for 10-30 minutes, start the pit pump 61 and pump it into the reactor of the desulfurization tower 2.

[0061] S2, measure 200-500 ml of polyether defoamer and mix it with 50 L of water in the container, stir it for 15-30 minutes to disperse the polyether defoamer, and connect the dosing pump 76 for standby use.

[0062] S3. After the fatty alcohol polyoxyethylene ether is pumped into the desulfurization tower 2 for 30 minutes, the coal tar pitch in the slurry and the slurry are stratified. A large amount of foam starts to form in the slurry in the desulfurization tower 2, and the coal tar pitch precipitates stably, and a false rise in the liquid level begins to occur. The dosing pump 76 is activated to continuously adjust the addition amount and add the diluted polyether defoamer to the sump 6.

[0063] S4. The agitator of the sump 6 and the sump pump 61 keep running normally, and the mixed slurry in the sump 6 (including the polyether defoamer solution, the reflux slurry from the desulfurization tower 2, fatty alcohol polyoxyethylene ether, etc.) is pumped into the desulfurization tower 2 to eliminate the foam in the slurry, accurately control the liquid level, and avoid the problem of false high liquid level.

[0064] S5. The density of the limestone slurry in the pulping tank 41 is maintained at 1170 - 1180 kg / m 3 , and the pH value is 11 - 12. It is continuously added to the sump 6 through the pipeline, and continuously supplied to the reaction kettle of the desulfurization tower 2 by the sump pump 61, and the pH value of the slurry in the desulfurization tower 2 is maintained at 5.0 - 5.3, and the density of the desulfurized slurry is maintained at 1115 - 1130 kg / m 3 .

[0065] S6. Start the vacuum belt filter press 9, control the speed at 25 - 32 Hz, start the gypsum slurry discharge pump 75 to discharge the slurry in the desulfurization tower 2 to the vacuum belt filter press 9. After the slurry is dewatered, gypsum with a moisture content of less than 30% is produced. During the dewatering process, the sump pump 61 continuously supplies slurry to keep the liquid level in the desulfurization tower 2 unchanged and keep the density of the slurry in the desulfurization tower 2 unchanged, so as to maintain the pH value at 5.0 - 5.3 during the continuous slurry supply process and reduce the fluctuation of the pH value.

[0066] S7. After step S6, 50% of the wastewater is pumped out by the vacuum pump 91 and recycled into the vacuum belt filter press 9 for secondary dewatering, and 50% is discharged to the filter pond 93 and discharged into the cooling tower three - stage sedimentation pond after precipitation.

[0067] S8. After step S7, during the gypsum dewatering process, when the moisture content of the gypsum is greater than 15%, that is, when the dewatering does not meet the requirement of a moisture content of less than 15%, re - prepare 1 L of polyether defoamer, stir it evenly with 50 L of water, activate the dosing pump 76 and continuously spray it into the underflow slurry of the hydrocyclone 71 at a rate of 5 L / h in a continuous atomization manner, which directly enters the vacuum belt filter press 9. After the slurry is dewatered, gypsum with a moisture content of less than 15% is produced.

[0068] A reflux pipe 8 leading to a sump 6 is connected to the bottom end of a desulfurization tower 2, and a pH measuring device 81 is provided on the reflux pipe 8 on the side where the sump 6 is located; a backwashing pipe 32 is provided on the reflux pipe 8 on the side where the desulfurization tower 2 is located. With this arrangement, the slurry in the desulfurization tower 2 can be circulated back to the sump 6, so that the pH value of the slurry can be conveniently and quickly measured in the sump 6. The slurry supply amount is adjusted based on the measured pH value, and real-time control is carried out to always keep the pH value of the slurry between 5.0 and 5.3; the backwashing pipe 32 is provided on the reflux pipe 8, which can flush the continuous reflux pipe 8 with water to prevent the reflux pipe 8 from accumulating scale and ensure that the slurry can flow by gravity. At the same time, water can be added through the backwashing pipe 32 and flow into the sump 6 to mix with the slurry in the sump 6 to adjust the slurry level in the tower.

[0069] Example 1

[0070] Add 100 ml of fatty alcohol polyoxyethylene ether (AEO) and add it to the sump 6 and stir for 30 minutes; add 200 ml of polyether defoamer and stir for 15 minutes. Control the pH value of the slurry to be 5.5 - 6.0, and the density to be 1140 - 1150 kg / m 3 , control the liquid level to be 6.5 - 7 m, the gypsum thickness to be 15 mm - 25 mm, and the belt conveyor to run at 25 - 30 HZ. After pumping the fatty alcohol polyoxyethylene ether (AEO) into the desulfurization tower 2 through the sump pump 61 for fifteen minutes, start the dosing pump 76 to pump 200 ml of polyether defoamer into the sump 6 and then into the desulfurization tower 2 to prevent a large amount of foam from being generated in the slurry. After the slurry foam is eliminated, start the vacuum pump 91 for dehydration.

[0071] Example 2

[0072] Add 300 ml of fatty alcohol polyoxyethylene ether (AEO) and add it to the sump 6 and stir for 15 minutes; add 500 ml of polyether defoamer and stir for 15 minutes. Control the pH value of the slurry to be 5.4 - 5.7, and the density to be 1135 - 1140 kg / m 3 , control the liquid level to be 6.5 - 7 m, the gypsum thickness to be 10 mm - 20 mm, and the belt conveyor to run at 25 - 30 HZ. After pumping the fatty alcohol polyoxyethylene ether (AEO) into the desulfurization tower 2 through the sump pump 61 for twenty minutes, start the dosing pump 76 to pump 300 ml of polyether defoamer into the sump 6 and then into the desulfurization tower 2 to eliminate a large amount of foam generated after oil removal, and then start the vacuum pump 91 for dehydration.

[0073] Example 3

[0074] Add 300 ml of fatty alcohol polyoxyethylene ether (AEO) and add it to the sump 6 and stir for 10 minutes; add 500 ml of polyether defoamer and stir for 30 minutes. Control the pH value of the slurry to be 5.0 - 5.3, and the density to be 1115 - 1130 kg / m 3, the gypsum thickness is 10 mm - 20 mm, and the belt conveyor operates at 25 - 30 HZ. After pumping fatty alcohol polyoxyethylene ether (AEO) into the desulfurization tower 2 through the sump pump 61 for thirty minutes, start the dosing pump 76 to pump 300 ml of polyether defoamer into the sump 6 and then into the desulfurization tower 2; meanwhile, re-prepare 1 L of polyether defoamer and mix it evenly with 50 L of water, and use the dosing pump 76 to continuously atomize and add it (5 L / h) to the underflow slurry of the cyclone 71 in small amounts to eliminate a large amount of foam in the slurry after oil removal, and then start the vacuum pump 91 for dehydration.

[0075] Since the commissioning of roasting wet desulfurization, due to defects in equipment and unfamiliarity with process technology, and the fact that the original flue gas SO2 is far higher than the design value of 500 mg / m 3 , twice the amount, with a high tar content, the average SO2 content at the desulfurization inlet flue gas reaches 1070 mg / m 3 , the water content of the produced gypsum is more than 38%, and the desulfurization efficiency is less than 80%. Before optimizing the process, it was difficult to control the slurry concentration in the desulfurization tower 2. The bottom slurry was extremely viscous, the overall slurry activity was low, and during the continuous desulfurization process, the slurry was frequently poisoned. It was difficult to discharge and dehydrate the viscous slurry. Even the dehydrated gypsum of the discharged slurry had extremely poor dehydration efficiency, and the dehydrated gypsum was in a muddy state, as Figure 4 shown. Analyze the desulfurized gypsum produced, and the specific situation is as follows in the table:

[0076]

[0077] After optimizing the process, analyze the desulfurized gypsum produced, and the specific situation is as follows in the table:

[0078]

[0079] Analyze the samples of gypsum dehydration in Examples 1 - 3 of the implementation case, conduct water content detection, and then take 3 bottles of 500 ml slurry each and let them stand for 2 hours to observe the stratification thickness of the sediment, and at the same time detect the sulfur dioxide content at the desulfurization inlet and outlet. The specific situation is as follows in the table:

[0080]

[0081] The results show that the slurry poisoning solved in Example 3 of the implementation case can maintain the slurry activity, pump out the slurry, and has good stability for its gypsum dehydration method. As Figure 5 shown, the dehydrated gypsum is in a loose state, the water content of the gypsum is greatly reduced, and the quality of the gypsum is further improved; SO2 can meet the emission requirements for a long time, and in the operation of a wet desulfurization system with a high tar content in the flue gas, it can effectively solve and avoid the phenomenon of slurry poisoning.

[0082] The fatty alcohol polyoxyethylene ether (AEO) acts in the desulfurization tower 2 to precipitate and separate tar from the slurry, increase the activity of the slurry, reduce the viscosity of the slurry, and avoid poisoning; the polyether defoamer and one are used in the desulfurization tower 2 to eliminate the slurry foam, ensure accurate detection of the slurry level, and avoid false high level; however, the dosage of the defoamer needs to be within a certain range, and the slurry concentration, pH value, etc. need to be controlled during the desulfurization process. Excessive defoamer will affect the slurry concentration, pH value, etc., thus affecting the desulfurization effect; therefore, after adding a certain dose of defoamer to the desulfurization tower 2, it is ensured that the desulfurization tower 2 is stable in the state of high-efficiency desulfurization; however, during the gypsum dehydration process, the extracted slurry has an increasing amount of foam again due to continuous stirring and other reasons. By leading the defoamer into the underflow slurry of the cyclone and fully mixing, the slurry with a large water content has a tendency to separate water and slurry. During the gypsum dehydration process, a large number of bubbles are often generated, and these bubbles will adhere to the gypsum particles and hinder the separation of water. Therefore, the defoamer can reduce the surface tension of the liquid surface, make bubbles not easy to form, and can destroy the formed bubbles, thereby promoting the separation of water, helping the gypsum dehydration, improving the efficiency of gypsum dehydration, reducing the dehydration time, and increasing the output and quality. By leading the defoamer into the slurry in the desulfurization tower and the slurry to be dehydrated in sections, the desulfurization efficiency of the desulfurization tower can be ensured, the poisoning of the slurry can be avoided, and at the same time, high-efficiency gypsum dehydration can be achieved.

[0083] The test results show that, compared with the slurry without adding fatty alcohol polyoxyethylene ether (AEO) for oil removal and with polyether defoamer added, the slurry in the desulfurization tower 2 with fatty alcohol polyoxyethylene ether (AEO) added according to the present invention is stratified (tar and other impurities and the slurry). After the tar is precipitated, its density is lower than that of the slurry (containing impurities, etc.) and it floats relatively on the upper layer, and can be pumped away in time by the slurry gypsum slurry discharge pump 75; after the tar and the slurry are separated and precipitated, the tar will not be contained in the slurry, especially in the viscous slurry, which will cause the tar and the slurry to sink to the bottom as a whole, and then be stirred, and then be pumped away by the desulfurization circulating pump 23 for circulating spraying, resulting in poor desulfurization efficiency. That is, when the desulfurization circulating pump 23 pumps the bottom slurry for circulating spraying for desulfurization, it is necessary to avoid pumping the slurry containing high tar as much as possible to ensure the desulfurization efficiency. The present invention adds fatty alcohol polyoxyethylene ether (AEO) to analyze the tar from the viscous slurry in time, and the tar can be pumped away or float on the upper layer, and then by supplementing fresh slurry, the viscosity of the slurry is reduced, so as to ensure the desulfurization efficiency; the slurry is also more easily pumped out by the gypsum slurry discharge pump 75 for dehydration, so that during the continuous dehydration process, the slurry is continuously supplemented to the desulfurization tower from the sump, avoiding the poisoning phenomenon of the slurry. By adding polyether defoamer to the desulfurization tower 2, the accurate detection of the slurry level is ensured; adding the prepared polyether defoamer to the underflow of the hydrocyclone 71 can solve the problem that the gypsum has a high water content and presents a sludge-like state; through the optimized control of the overall process, the activity of the slurry is increased and the poisoning situation is alleviated, which can improve the quality of the produced gypsum, and its water content is significantly reduced, visually extremely dry, without the sludge-like state, and the water content can be below 15%. Further verification shows that its performance meets the slurry poisoning caused by high tar asphalt content. Compared with the poisoned slurry without changing the operation method and without adding fatty alcohol polyoxyethylene ether (AEO) and polyether defoamer, the poisoned slurry can solve the problem of excessive SO2 emissions through this method, and the gypsum can meet the standard for dehydration.

[0084] Conclusion: Using the method for removing oil from poisoned slurry of the present invention results in lower SO2 emissions, lower water content of the slurry gypsum, and more accurate and stable pH of the desulfurization tower 2. The false liquid level of the desulfurization tower 2 is eliminated. When the content of pitch fume in the flue gas is greater than 40%, the probability of slurry poisoning decreases, maintaining high dehydration efficiency and avoiding production interruption caused by replacing the slurry in the desulfurization tower 2.

[0085] The wet desulfurization system studied in the present invention solves the technical problem of the sludge-like gypsum, reduces SO2 emissions, and thus provides a guarantee for increasing the proportion of high-sulfur coke in the anode carbon block. It is of great significance for the stable operation of the wet desulfurization system in the future, the production and sales of gypsum, the reduction of anode production costs, and the improvement of high-sulfur carbon block production.

[0086] After optimizing the process, the pass rate of flue gas emissions is 100%, the quality of gypsum has been improved, meeting the production requirements of high-sulfur carbon blocks in the roasting furnace. At the same time, the desulfurization process has been stabilized, ensuring the normal dehydration of gypsum, reducing the risks of safety and environmental protection, lightening the labor intensity of workers, and improving production efficiency.

[0087] Specifically: the online detection of sulfur dioxide in flue gas exceeded the standard 0 times throughout the year; the water content of gypsum was reduced to less than 15%; the abnormal shutdown of the desulfurization system was 0 times, and the slurry poisoning and the shutdown time of the faulty machine were reduced from 6 days / year to 0 days / year, meeting the production requirements of high-sulfur carbon blocks in the roasting furnace throughout the year.

[0088] The research and popularization of the wet desulfurization system for anode baking flue gas reduce the risks of slurry poisoning and SO2 emission exceeding the standard in the desulfurization system, achieving ultra-low emissions. It has a good demonstration effect on the treatment of baking flue gas in aluminum carbon, and at the same time eliminates the production stoppage of the roasting furnace caused by the shutdown of the desulfurization system due to slurry poisoning, producing good environmental and social benefits, and having good prospects for popularization and application.

[0089] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for poisoning of calcium-based desulfurization gypsum slurry, characterized in that, It includes the following steps: S1. Measure 100 - 300 ml of fatty alcohol polyoxyethylene ether, continuously add it to the pit in small amounts under stirring conditions, start the pit pump to pump it into the desulfurization tower reactor after stirring for 10 - 30 minutes; S2. Measure 200 - 500 ml of polyether defoamer and mix it with 50 L of water in a container, stir well for 15 - 30 minutes to disperse the polyether defoamer, and connect the chemical dosing pump for standby; S3. After the fatty alcohol polyoxyethylene ether is pumped into the desulfurization tower for 20 minutes, start the chemical dosing pump to continuously add the diluted polyether defoamer to the pit while adjusting the addition amount; S4. Keep the pit stirrer and the pit pump running normally, and pump the pit mixed slurry containing polyether defoamer into the desulfurization tower; the pit mixed slurry includes polyether defoamer solution, reflux slurry from the desulfurization tower, and fatty alcohol polyoxyethylene ether; S5. The density of the limestone slurry in the pulping tank is maintained at 1170 - 1180 kg / m 3 , the pH value is 11 - 12, and it is continuously added to the sump through a gravity pipeline. The sump pump continuously supplies the slurry to the reaction kettle of the desulfurization tower, and maintains the pH value of the slurry in the desulfurization tower at 5.0 - 5.3 and the density of the desulfurization slurry at 1115 - 1130 kg / m 3 ; S6. Start the vacuum belt filter press, control the speed at 25 - 32 Hz, start the gypsum slurry discharge pump to discharge the slurry in the desulfurization tower to the vacuum belt filter press for dehydration, and the gypsum with a water content of less than 30% is produced after the slurry is dehydrated; during the dehydration process, the pit pump continuously supplies slurry to keep the liquid level in the desulfurization tower unchanged.

2. The control method for the poisoning of the calcium-based desulfurization gypsum slurry according to claim 1, characterized in that, It includes the following steps: S7. After step S6, the vacuum pump extracts 50% of the wastewater for recycling and secondary dehydration in the vacuum belt filter press, and 50% is discharged to the filtration pond, and after precipitation, it is discharged into the three - stage sedimentation pond of the cooling tower for use as flue gas cooling water.

3. The control method for the poisoning of calcium desulfurization gypsum slurry according to claim 2, characterized in that: A hydrocyclone is arranged between the slurry discharge pump and the vacuum belt filter press, and the pressure of the hydrocyclone is 0.2 - 0.3 MPa.

4. The control method for the poisoning of the calcium-based desulfurization gypsum slurry according to claim 3, characterized in that, It includes the following steps: S8. After step S7, during the gypsum dehydration process, when the water content of the gypsum is greater than 15%, re - prepare 1 L of polyether defoamer, stir it evenly with 50 L of water, start the chemical dosing pump to continuously spray it into the underflow slurry of the hydrocyclone at 5 L / h in a continuous atomization manner, and directly enter the vacuum belt filter press. After the slurry is dehydrated, the produced gypsum has a water content of less than 15%.

5. The control method for the poisoning of the calcium-based desulfurization gypsum slurry according to claim 4, characterized in that: It includes a desulfurization system, and the desulfurization system includes a desulfurization tower. The desulfurization tower is connected with a reflux pipe leading to the pit, and a densitometer and a pH value measuring device are sequentially arranged on the reflux pipe.

6. The control method for the poisoning of the calcium-based desulfurization gypsum slurry according to claim 5, wherein: The upper end of the reflux pipe is connected with a backflush water pipe.

7. The control method for the poisoning of the calcium-based desulfurization gypsum slurry according to claim 3, characterized in that: The outlet of the hydrocyclone is provided with a separation pipe one with a high solid content and a separation pipe two with a low solid content. The separation pipe one is connected with the vacuum belt filter press, and the separation pipe two is connected with the pit.

8. The control method for the poisoning of calcium-based desulfurization gypsum slurry according to claim 1, characterized in that: In step S1, the fatty alcohol polyoxyethylene ether is 300 ml, and the stirring reaction time is 10 minutes; in step S2, the polyether defoamer is 500 ml, and the stirring reaction time is 30 minutes.

Images