Technical analysis on commissioning and operation of decanter centrifuge
Date：2016-11-08 Hits：
As the debugging of sludge dehydration and main task of the work is in accordance with the existing conditions, the optimal operation parameters for sludge, between equipment and flocculant three, between the three simply rely on one or the other party will ignore the problems of the operation. Good control of these operating parameters to ensure long-term stable operation, and timely scientific and effective adjustment to changes in the scene, which still meet the perfect fit, to achieve the lowest flocculant consumption situation, processing efficiency is the best treatment effect and the biggest, in order to achieve the lowest operating cost, meet the requirements of the best technical and economical.
1.Flocculant adjustment of sludge properties and concentration changes
In the process of sewage treatment plant, equipment commissioning stage, due to the quality and quantity of water, water treatment process condition and other factors, the nature of the sludge treatment may occur many changes, this change depends on the sludge dewatering machine and flocculant will fluctuate, sludge age or sludge storage time will affect the properties of sludge the content of organic matter, such as sludge concentration, sludge (or ash content), sludge, granular sludge (Sludge Density specifications itself skeleton structure condition) dependent fluctuation of flocculants and dewatering machine will be more obvious, so at the scene according to the situation in a timely manner to adjust to ensure the normal operation and management of sludge dewatering. This stage of the sludge dewatering effect and drug consumption and the normal operation may have some differences, this difference with the field of water treatment facilities running gradually normal and sludge discharge processing gradually stable and tend to be stable.
Even in the sewage treatment plant to achieve the normal operation, the actual nature or concentration of sludge to be treated will change, especially for those who are not directly to the sludge thickening tank sludge was dewatered for this change may be more frequent fluctuations will be larger, there is relative variation of sludge concentration tank small, these conditions tend to be ignored or overlooked. The main reason for this change is：
A because of the change of influent load, the residence time of a sink or two settling tank is changed, and the actual settling time of the suspended substance changes, which results in the change of sludge density and concentration;
Because of the change of sludge flow rate or sludge discharge cycle, the sludge concentration in the sludge dewatering workshop is changed in B;
C due to the abnormal operation of the site (such as maintenance, etc.) lead to changes in the sludge, or because of seasonal reasons, especially in the event of a change in the nature of the sludge and concentration changes.
These changes are often difficult to observe on the surface, but also easy to be ignored, but a simple calculation of the magnitude of the impact of this change can be aware of the impact.
The sludge concentration for processing as an example: if the emissions to be treated sludge water content changes from 96% to 97% the sludge dewatering workshop, namely solid content from 4% to 3%, the 1% concentration of absolute value changes in the relative value of amplitude has reached 25%, the flocculant consumption and treating sludge solid content is proportional to the normal when running, the consumption of flocculant also reduced about 25%. If this is not timely adjustment to reduce the dosage of flocculant, flocculant and sludge flow in the same flow conditions, the flocculant can be wasted by about 25%, while the apparent mud cake and there is no obvious change. On the contrary, if the sludge concentration increases, and the flocculant does not follow the increase, the sludge dewatering effect will decrease accordingly.
This change occurs in the process of sewage treatment plant in the operation, especially in the absence of sludge concentration tank, this change will be more significant. Therefore, in the field should always pay attention to the important effect of flocculant consumption factors, great changes in the nature of sludge, to timely adjust the suitable flocculant to sludge dewatering operation; the sludge concentration changes, timely adjustments to the flow of supply flocculant so that it can not only meet the treatment effect and to avoid waste.
The specific method is often observed out of the mud, and then decreasing flocculant fluid supply flow, can reduce the frequency of each flocculant dosing pump 0.5-1.0Hz, observe the mud cake and the supernatant and torque data after a few minutes, according to the situation to decide whether to continue to reduce the frequency of dosing pump, until you find the most economical dosing pump operating frequency, or can be used every increase in pump frequency around 0.5-1.0Hz to observe and adjust.
On the contrary, when the sludge concentration increases, it is adjusted in the opposite direction.
In addition, the centrifuge structure determines the high quality into the mud into the mud, not a large number of large size particles and fibrous material, otherwise easily lead to blockage of equipment, vibration increase, effect of treatment efficiency. Therefore, the sludge must be done before the sludge into the centrifuge cutting treatment.
2．Control of processing capacity of decanter centrifuge
Any decanter centrifuge has a maximum processing capability requirement, which requires two data reference guidance:
A．Maximum handling dry solids load, i.e., maximum solids weight per hour of treatment, to KGDS (dry solids) /h representation;
B．The maximum available hydraulic load, i.e., the sludge flow into the plant, is expressed in m3/h, which is the product of dry solids loading with the sludge concentration (solid content).
In the normal sludge concentration, should ensure that the maximum dry equipment load theory solid loading equipment manufacturers in the 70% - 90% calibration as well, to avoid the equipment utilization rate is low, while avoiding the long-term operation of equipment under high load caused by equipment loss accelerated, shorten the maintenance cycle.
In the case of large equipment load, in any case will not increase the dosage of flocculant, the treatment effect is better, the mud biscuit is not ideal, was carrying solid high, rate of decline, due to the overflow sediment carrying supernatant caused by equipment wear, dynamic balance, vibration intensified damage.
In some cases, due to the increase of sludge concentration, due to the original flow into the mud, the actual load into the mud more than the admissibility of the load index of the device to reduce the processing effect. At this time in a timely manner to gradually reduce the mud into the frequency, observe the effect, after the effect is stable, continue to try to control the flow of flocculant to the most economic dosage.
On the contrary, when the sludge concentration is reduced, to gradually increase the flow into the mud, the same period with the adjustment of dosing pump.
If the sludge concentration is too low, although the equipment for dry solid load is not high, but the hydraulic load is large, into the low concentration of sludge due to the high hydraulic loading equipment can not form effective mud ring layer, uniform thickness, solid settlement will be a large number of supernatant carry overflow, which directly affect the treatment effect and treatment efficiency. The low concentration of sludge, such as two sedimentation tank not concentrated sludge after best concentration treatment (such as concentration of postprocessing), or with a high concentration of sludge (as a sludge) mixed after dehydration treatment.
To avoid the sludge load is too large due to excessive torque overload caused by centrifuge will decrease, feeding pump frequency, this situation occurs mainly in the increase of sludge concentration, but still with the original operating condition into the mud flow.
3.Adjustment of separation factors
According to Storck's law：
Vg=d2(ρp-ρ1)g/(18η)
Vg—Gravity settling velocity, M / s;
D - solid particle diameter, m;
P p - solid particle density, kg/m3；
P 1 - liquid density, kg/m3;
ETA - liquid viscosity, kg/m s?;
G - gravity acceleration, 9.81m / s2；
The formula of centrifugal sedimentation can be obtained from the above formula:
Vc=d2(ρp-ρ1)rω2/(18η)
Vc - centrifugal sedimentation velocity, M / S
R - centrifugal radius，m
Omega angular velocity，1／s
ω＝2πN／60
N—r／min
According to the formula only centrifuge radius R and the angular velocity reaches a certain value, in the centrifuge limited space, in the shortest possible time can obtain satisfactory settlement effect, so hope to get the better effect of sludge treatment, centrifugal machine is inevitable.
The separation factor indicates the centrifugal force field, which is controlled by adjusting the rotation speed of the centrifuge. Improve the separation factor, production capacity and improve the separation effect, but the wear and power consumption of the drum and the spiral increases, should meet the production capacity and separation requirements in a low separation factor, the data refer to the device description and actual operating conditions to determine the control speed of centrifugal machine to achieve normal and stable equipment the normal operation and treatment of sludge dehydration effect for reference.
4.Differential speed adjustment
The size of the differential velocity determines the processing power and the. To improve the speed, discharge capacity increased rapidly, but the slag with high moisture content, low recovery rate; reduce the speed difference, the mud cookies increased, showing screw torque, reducing handling capacity. So to meet the maximum processing capacity and the best treatment effect of this contradiction, to find the best speed difference value, this value can be adjusted up and down according to the actual situation, combined with the sludge and mud flow, to determine the status of supernatant cookies.
It should be noted that, in the case of the same sludge flow rate and sludge concentration, the differential velocity increases, the torque decreases, and the moisture content of the mud cake increases; on the contrary, the differential velocity decreases, the torque increases, and the moisture content of the mud cake decreases. In principle to principle to determine the differential velocity parameters to maximum throughput with the best treatment effect, to ensure reasonable dosage of flocculant dosage in the range, the speed of the centrifuge is fixed, the concentration of mud into relatively stable situation, equipment processing capacity and dewatering effect depends on the speed difference.
The torque is also related to the dry solids load in the centrifuge, so it is necessary to adjust the load. With the change of sludge concentration, the change of dry solid load will lead to the change of torque when the mud flow rate is equal to the same. So, in the scene will often be the case, when a lot of great torque, but out of the mud cookies is not high, and sometimes the torque is not high, but the mud biscuit is very good, this is due to the impact load caused by different devices so that understanding is not only of mud cookies, observation equipment torque parameter, finally the actual mud cake shall prevail.
If the sludge load is too large, the difference is too large, it will not only affect the mud biscuit degree, but also make the supernatant quality decreased, the recovery rate of sludge treatment effect.
5.Flocculant dosing point adjustment
A flocculant dosing point is different, will directly affect the drug mud mixing and reaction conditions, thus affecting the floc strength and slurry separation state, state, and ultimately affect the consumption and the effect of sludge treatment flocculant. The flocculant dosing point has a variety of options, in general, can be arranged into a sludge pump before dosing, sludge pump dosing and centrifuge sludge dosing entrance pipeline. Set up and adjust the specific dosing point is decided according to the nature of sludge, the characteristics and features of the flocculant through practical application, to determine the general test.
At present, some manufacturers of centrifuges using a mixture of materials into the centrifuge position adjustable manner, the specific adjustment can be determined according to the actual situation.
三.The basic principles of sludge dewatering operation management and condition adjustment：
In order to achieve the best treatment effect, the maximum processing capacity and the lowest drug consumption, should be in accordance with the following principles of on-site management:
1.Processing capacity of sludge dewatering machine is controlled within an appropriate range, combined with the sludge flow, flow rate and the difference of flocculant is adjusted to avoid the sudden increase in load caused by the system and equipment overload frequent fluctuations in the treatment effect, and can achieve greater efficiency of equipment;
2.The sludge concentration changes to adjust the flow and speed difference of flocculant, both to ensure the treatment effect and avoid the waste sludge flow; increase or increase of sludge concentration, flow velocity difference tracking flocculant increased, a corresponding increase; sludge flow decreased or sludge concentration decreased, flocculent flow tracking is reduced, a corresponding reduction in speed difference;
3.The mud performance to determine the best cookies to speed range with torque data, in principle does not cause congestion and meet the processing capacity of centrifuge under the condition of low margin of use as far as possible to achieve better treatment effect and reduce the consumption of flocculant;
4.The flocculant is not the best, only the most suitable match, flocculant type and consumption depends on the quality and properties of sludge agent, also depends on the matching and equipment structure and operation, only three had the best operation combination, in order to achieve the minimum consumption of flocculant, the effect of the best and highest treatment efficiency.
5.All on-site management and operation personnel work to be done is: continuous observation, timely adjust and be good at summing up, as far as possible for all the perfect best working parameters, the relative stability of the complexes in a variety of possible changes in the. In general, the observation and the adjustment of the best 1 ~ 2 hours should be done once, to strictly avoid the boot after the operating parameters of equipment or a shift to persist for a long time without any adjustment of the situation, field operators lazy or strong sense of responsibility is a long-term operation efficiency of sludge dewatering workshop is not high, mainly due to consumption volatility and waste treatment effect of medicine.
For the daily use, cleaning, maintenance and repair of other sludge dewatering equipment and facilities, please refer to the equipment specifications and equipment operating procedures provided by the equipment manufacturer.
1.Flocculant adjustment of sludge properties and concentration changes
In the process of sewage treatment plant, equipment commissioning stage, due to the quality and quantity of water, water treatment process condition and other factors, the nature of the sludge treatment may occur many changes, this change depends on the sludge dewatering machine and flocculant will fluctuate, sludge age or sludge storage time will affect the properties of sludge the content of organic matter, such as sludge concentration, sludge (or ash content), sludge, granular sludge (Sludge Density specifications itself skeleton structure condition) dependent fluctuation of flocculants and dewatering machine will be more obvious, so at the scene according to the situation in a timely manner to adjust to ensure the normal operation and management of sludge dewatering. This stage of the sludge dewatering effect and drug consumption and the normal operation may have some differences, this difference with the field of water treatment facilities running gradually normal and sludge discharge processing gradually stable and tend to be stable.
Even in the sewage treatment plant to achieve the normal operation, the actual nature or concentration of sludge to be treated will change, especially for those who are not directly to the sludge thickening tank sludge was dewatered for this change may be more frequent fluctuations will be larger, there is relative variation of sludge concentration tank small, these conditions tend to be ignored or overlooked. The main reason for this change is：
A because of the change of influent load, the residence time of a sink or two settling tank is changed, and the actual settling time of the suspended substance changes, which results in the change of sludge density and concentration;
Because of the change of sludge flow rate or sludge discharge cycle, the sludge concentration in the sludge dewatering workshop is changed in B;
C due to the abnormal operation of the site (such as maintenance, etc.) lead to changes in the sludge, or because of seasonal reasons, especially in the event of a change in the nature of the sludge and concentration changes.
These changes are often difficult to observe on the surface, but also easy to be ignored, but a simple calculation of the magnitude of the impact of this change can be aware of the impact.
The sludge concentration for processing as an example: if the emissions to be treated sludge water content changes from 96% to 97% the sludge dewatering workshop, namely solid content from 4% to 3%, the 1% concentration of absolute value changes in the relative value of amplitude has reached 25%, the flocculant consumption and treating sludge solid content is proportional to the normal when running, the consumption of flocculant also reduced about 25%. If this is not timely adjustment to reduce the dosage of flocculant, flocculant and sludge flow in the same flow conditions, the flocculant can be wasted by about 25%, while the apparent mud cake and there is no obvious change. On the contrary, if the sludge concentration increases, and the flocculant does not follow the increase, the sludge dewatering effect will decrease accordingly.
This change occurs in the process of sewage treatment plant in the operation, especially in the absence of sludge concentration tank, this change will be more significant. Therefore, in the field should always pay attention to the important effect of flocculant consumption factors, great changes in the nature of sludge, to timely adjust the suitable flocculant to sludge dewatering operation; the sludge concentration changes, timely adjustments to the flow of supply flocculant so that it can not only meet the treatment effect and to avoid waste.
The specific method is often observed out of the mud, and then decreasing flocculant fluid supply flow, can reduce the frequency of each flocculant dosing pump 0.5-1.0Hz, observe the mud cake and the supernatant and torque data after a few minutes, according to the situation to decide whether to continue to reduce the frequency of dosing pump, until you find the most economical dosing pump operating frequency, or can be used every increase in pump frequency around 0.5-1.0Hz to observe and adjust.
On the contrary, when the sludge concentration increases, it is adjusted in the opposite direction.
In addition, the centrifuge structure determines the high quality into the mud into the mud, not a large number of large size particles and fibrous material, otherwise easily lead to blockage of equipment, vibration increase, effect of treatment efficiency. Therefore, the sludge must be done before the sludge into the centrifuge cutting treatment.
2．Control of processing capacity of decanter centrifuge
Any decanter centrifuge has a maximum processing capability requirement, which requires two data reference guidance:
A．Maximum handling dry solids load, i.e., maximum solids weight per hour of treatment, to KGDS (dry solids) /h representation;
B．The maximum available hydraulic load, i.e., the sludge flow into the plant, is expressed in m3/h, which is the product of dry solids loading with the sludge concentration (solid content).
In the normal sludge concentration, should ensure that the maximum dry equipment load theory solid loading equipment manufacturers in the 70% - 90% calibration as well, to avoid the equipment utilization rate is low, while avoiding the long-term operation of equipment under high load caused by equipment loss accelerated, shorten the maintenance cycle.
In the case of large equipment load, in any case will not increase the dosage of flocculant, the treatment effect is better, the mud biscuit is not ideal, was carrying solid high, rate of decline, due to the overflow sediment carrying supernatant caused by equipment wear, dynamic balance, vibration intensified damage.
In some cases, due to the increase of sludge concentration, due to the original flow into the mud, the actual load into the mud more than the admissibility of the load index of the device to reduce the processing effect. At this time in a timely manner to gradually reduce the mud into the frequency, observe the effect, after the effect is stable, continue to try to control the flow of flocculant to the most economic dosage.
On the contrary, when the sludge concentration is reduced, to gradually increase the flow into the mud, the same period with the adjustment of dosing pump.
If the sludge concentration is too low, although the equipment for dry solid load is not high, but the hydraulic load is large, into the low concentration of sludge due to the high hydraulic loading equipment can not form effective mud ring layer, uniform thickness, solid settlement will be a large number of supernatant carry overflow, which directly affect the treatment effect and treatment efficiency. The low concentration of sludge, such as two sedimentation tank not concentrated sludge after best concentration treatment (such as concentration of postprocessing), or with a high concentration of sludge (as a sludge) mixed after dehydration treatment.
To avoid the sludge load is too large due to excessive torque overload caused by centrifuge will decrease, feeding pump frequency, this situation occurs mainly in the increase of sludge concentration, but still with the original operating condition into the mud flow.
3.Adjustment of separation factors
According to Storck's law：
Vg=d2(ρp-ρ1)g/(18η)
Vg—Gravity settling velocity, M / s;
D - solid particle diameter, m;
P p - solid particle density, kg/m3；
P 1 - liquid density, kg/m3;
ETA - liquid viscosity, kg/m s?;
G - gravity acceleration, 9.81m / s2；
The formula of centrifugal sedimentation can be obtained from the above formula:
Vc=d2(ρp-ρ1)rω2/(18η)
Vc - centrifugal sedimentation velocity, M / S
R - centrifugal radius，m
Omega angular velocity，1／s
ω＝2πN／60
N—r／min
According to the formula only centrifuge radius R and the angular velocity reaches a certain value, in the centrifuge limited space, in the shortest possible time can obtain satisfactory settlement effect, so hope to get the better effect of sludge treatment, centrifugal machine is inevitable.
The separation factor indicates the centrifugal force field, which is controlled by adjusting the rotation speed of the centrifuge. Improve the separation factor, production capacity and improve the separation effect, but the wear and power consumption of the drum and the spiral increases, should meet the production capacity and separation requirements in a low separation factor, the data refer to the device description and actual operating conditions to determine the control speed of centrifugal machine to achieve normal and stable equipment the normal operation and treatment of sludge dehydration effect for reference.
4.Differential speed adjustment
The size of the differential velocity determines the processing power and the. To improve the speed, discharge capacity increased rapidly, but the slag with high moisture content, low recovery rate; reduce the speed difference, the mud cookies increased, showing screw torque, reducing handling capacity. So to meet the maximum processing capacity and the best treatment effect of this contradiction, to find the best speed difference value, this value can be adjusted up and down according to the actual situation, combined with the sludge and mud flow, to determine the status of supernatant cookies.
It should be noted that, in the case of the same sludge flow rate and sludge concentration, the differential velocity increases, the torque decreases, and the moisture content of the mud cake increases; on the contrary, the differential velocity decreases, the torque increases, and the moisture content of the mud cake decreases. In principle to principle to determine the differential velocity parameters to maximum throughput with the best treatment effect, to ensure reasonable dosage of flocculant dosage in the range, the speed of the centrifuge is fixed, the concentration of mud into relatively stable situation, equipment processing capacity and dewatering effect depends on the speed difference.
The torque is also related to the dry solids load in the centrifuge, so it is necessary to adjust the load. With the change of sludge concentration, the change of dry solid load will lead to the change of torque when the mud flow rate is equal to the same. So, in the scene will often be the case, when a lot of great torque, but out of the mud cookies is not high, and sometimes the torque is not high, but the mud biscuit is very good, this is due to the impact load caused by different devices so that understanding is not only of mud cookies, observation equipment torque parameter, finally the actual mud cake shall prevail.
If the sludge load is too large, the difference is too large, it will not only affect the mud biscuit degree, but also make the supernatant quality decreased, the recovery rate of sludge treatment effect.
5.Flocculant dosing point adjustment
A flocculant dosing point is different, will directly affect the drug mud mixing and reaction conditions, thus affecting the floc strength and slurry separation state, state, and ultimately affect the consumption and the effect of sludge treatment flocculant. The flocculant dosing point has a variety of options, in general, can be arranged into a sludge pump before dosing, sludge pump dosing and centrifuge sludge dosing entrance pipeline. Set up and adjust the specific dosing point is decided according to the nature of sludge, the characteristics and features of the flocculant through practical application, to determine the general test.
At present, some manufacturers of centrifuges using a mixture of materials into the centrifuge position adjustable manner, the specific adjustment can be determined according to the actual situation.
三.The basic principles of sludge dewatering operation management and condition adjustment：
In order to achieve the best treatment effect, the maximum processing capacity and the lowest drug consumption, should be in accordance with the following principles of on-site management:
1.Processing capacity of sludge dewatering machine is controlled within an appropriate range, combined with the sludge flow, flow rate and the difference of flocculant is adjusted to avoid the sudden increase in load caused by the system and equipment overload frequent fluctuations in the treatment effect, and can achieve greater efficiency of equipment;
2.The sludge concentration changes to adjust the flow and speed difference of flocculant, both to ensure the treatment effect and avoid the waste sludge flow; increase or increase of sludge concentration, flow velocity difference tracking flocculant increased, a corresponding increase; sludge flow decreased or sludge concentration decreased, flocculent flow tracking is reduced, a corresponding reduction in speed difference;
3.The mud performance to determine the best cookies to speed range with torque data, in principle does not cause congestion and meet the processing capacity of centrifuge under the condition of low margin of use as far as possible to achieve better treatment effect and reduce the consumption of flocculant;
4.The flocculant is not the best, only the most suitable match, flocculant type and consumption depends on the quality and properties of sludge agent, also depends on the matching and equipment structure and operation, only three had the best operation combination, in order to achieve the minimum consumption of flocculant, the effect of the best and highest treatment efficiency.
5.All on-site management and operation personnel work to be done is: continuous observation, timely adjust and be good at summing up, as far as possible for all the perfect best working parameters, the relative stability of the complexes in a variety of possible changes in the. In general, the observation and the adjustment of the best 1 ~ 2 hours should be done once, to strictly avoid the boot after the operating parameters of equipment or a shift to persist for a long time without any adjustment of the situation, field operators lazy or strong sense of responsibility is a long-term operation efficiency of sludge dewatering workshop is not high, mainly due to consumption volatility and waste treatment effect of medicine.
For the daily use, cleaning, maintenance and repair of other sludge dewatering equipment and facilities, please refer to the equipment specifications and equipment operating procedures provided by the equipment manufacturer.
