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Analysis of Cow Dung Dewatering Machine

Abstract

This experiment studied the solid-liquid separation effect of cow dung dewatering machine.
The results show that the solid-liquid separation efficiency comparison of the unit time of the cow-dung dewatering machine:
  • 1.0mm screen > 0.5mm screen > 0.3mm. 
  • Screen and short moment > long moment. 
  • The higher the water content in the feed is, the better it is for the operation of the solid-liquid separator. 

Under the existing test conditions, the water content of the solid part after solid-liquid separation is lower than 60%. However, the solid recovery rate of the cow dung dewatering machine is not high (all lower than 30%). The recovery rate of solid nitrogen and phosphorus is less than 20%.  
Therefore, it is necessary to further improve the solid-liquid separation efficiency of the cow-dung dewatering machine. 
Generally, the water content of livestock and poultry excrement without bedding is more than 80%. For direct composting, the water content needs to be adjusted to about 65% with a conditioner. However, due to the limited resources of the conditioner or the high price. Many compost farms are unbearable. Therefore, before high-temperature composting, necessary dehydration or drying treatment should be carried out for livestock and poultry manure.
The main methods used at home and abroad for the dehydration of livestock and poultry excrement are high-temperature rapid drying, biological dehydration, and mechanical dehydration.
Compared with the heating dehydration method, the energy consumption of mechanical extrusion is relatively low. Therefore, mechanical dehydration is widely used in solid-liquid separation.
In many areas, it has become a consensus to apply the cow dung drying machine to the pre-treatment of pig manure. In this experiment, the BLUSLOT brand solid-liquid separator was used to analyze the operation parameters and comprehensive utilization benefits of pig manure solid-liquid separation.

Materials and Methods for Testing Cow Dung Dewatering Machine

The experiment was conducted on a large local pig farm. The basic properties of the tested manure: are pH 6.3, water content 77.69%, total nitrogen 2.83%, total phosphorus 3.57%, and total potassium 2.71%.

Select manure with different water content (75%~90%). Select three factors, namely, different aperture mesh screens (0.3mm, 0.3mm, 1.0mm) and different moments (that is, the counterweight is placed at the end and front end of the rod and marked as long force short and short moment respectively). 

The operation test of the solid-liquid separator was carried out. At the same time, the water content, nitrogen, and phosphorus content of manures before and after solid-liquid separation were analyzed. Record the power consumption and other parameters of the solid-liquid separator.  

Analysis and determination of items and methods: Moisture content is determined by drying at 105 ℃ for 6h. The content of nitrogen and phosphorus is determined by the standard method of organic fertilizer.

Test Results of Cow Dung Dewatering Machine

Effects of mesh size, moment, and feed concentration on solid-liquid separation efficiency

Slot SizeFeed water contentProcessing capacity(kg/h)Discharge quantity(kg/h)
(mm)(%)Under short momentUnder long moment of forceUnder short momentUnder long moment of force
0.376.43225.88±16.32172.30±9.8667.97±8.9850.03±5.61
0.380.7996.71±11.7273.94±8.9748.89±7.163.63±5.34
0.382.4376.34±41.79142.25±27.7839.41±9.4128.49±7.33
0.385.0684.71±9.85163.24±11.1941.48±3.1238.19±3.26
0.388.4479.14±12.11172.81±10.1340.63±2.3936.57±1.59
0.389.6292.67±15.63147.42±8.9044.15±8.0132.26±3.57
0.577.92356.68±8.90404.41±10.7493.15±5.8681.69±7.16
0.579.60510.66±21.41473.50±16.5996.70±6.50102.62±8.11
0.55.34410.40±6.32381.74±32.0685.63±8.2477.65±2.31
0.588.22563.57±18.96328.02±15.67122.87±9.14 63.53±4.54
0.591.15431.74±16.17332.81±9.7097.54±4.3167.26±4.67
1.076.21605.05±56.75209.01±47.45113.68±10.8935.35±4.72
1.078.57 887.70±91.14758.80±32.51168.19±14.57136.99±8.99
1.081.001183.84±16.351160.72±20.68200.73±5.68220.82±9.12
1.084.031854.62±35.611804.24±37.33361.72±9.98347.62±10.61
1.05.631973.17±150.56760.24±79.36395.65±32.33349.93±19.77
1.09.362046.69±79.44934.34±68.23436.21±16.21413.29±14.46
1.02.811184.59±160.60946.15±60.41 294.79±20.17176.20±9.84

It can be seen in Table 1. 

  • The material handling capacity (dry matter, the same as below) of the low dung dewatering machine with different feed concentrations per unit time under the short moment of 0.3mm aperture sieve is about 200kg/h. 
    The average material handling capacity per unit of time under long torque is about 160kg/h. 
    At the same moment, the feed concentration has little effect on the solid-liquid separation efficiency. 
  • 0.5mm aperture sieve under long or short torque conditions. The feed concentration affects the treatment efficiency of the unit time cow-dung dewatering machine. When the short torque and feed water content are 88.2%. The solid-liquid separator has the largest material handling capacity per unit time (up to 563.57kg/h). At the same time, the discharge volume is also the largest (122.87kg/h). 
    When the long torque and feed water content are 79.6%. The maximum material handling capacity of the solid-liquid separator per unit time is 473.50kg/h, and the discharge capacity is 102.60kg/h. 
  • The 1.0mm aperture sieve is under both long and short moments. With the gradual increase of feed water content, the number of materials processed per unit of time and the amount of discharged materials both increase at first and then decrease. 
    When the water content of the feed is 89.4%, the amount of material processed per unit of time and the amount of material discharged reach the maximum value under long and short torque. The amount of material handled per unit of time is 1934.34kg/h and 2046.69kg/h under long and short torque respectively. The discharge capacity of the unit time of the low dung dewatering machine is 413.29 kg/h and 436.21 kg/h under the long and short torque respectively. 

It can be seen from the comparison of the treatment efficiency of the screen with different apertures. At the same feed concentration, the unit time processing capacity and discharge capacity of each aperture screen under short torque is better than that under long torque. 

The amount of material handled and discharged per unit of time between mesh screens with different apertures is significantly different. 

The treatment efficiency of small aperture screen and large aperture screen is several times higher. And with the increase in the mesh size, the greater the difference in the treatment efficiency between different cow-dung dewatering machine mesh screens. 

Slot SizePower consumptionKW/HPower consumptionKW/H
(mm)Under short momentUnder long moment of forceUnder short momentUnder long moment of force
0.33.974.7216.7120.59
1.51.722.027.779.95
1.00.651.093.466.11

It can be seen in Table 2. 

Under the same aperture screen, the energy consumption under short torque is less than that under long torque for each 100kg of raw material processed. 

The energy consumption per 100kg fecal residue output is also shorter than the long torque. Among different screens, the mesh diameter increases gradually. The energy consumption per 100kg of raw material and 100kg of fecal residue is also gradually reduced. 

Under the condition of a short moment of 1.0mm mesh screen, the average power consumption per 100kg of raw material is the lowest, 0.65kW · h. 

Effluent after treatment of different concentrations of manure with different aperture screen

Slot SizeFeed water contentDischarge water content(%)Solid content of effluent(%)
(mm)(%)Under short momentUnder long moment of forceUnder short momentUnder long moment of force
0.376.4354.6960.9118.4118.00
0.380.7957.8558.0514.3914.47
0.382.4357.6954.6412.6012.92
0.385.0655.8749.7110.9611.00
0.388.4451.8851.558.318.34
0.389.6254.0153.917.417.63
0.577.9258.4253.1317.7617.17
0.579.6054.8852.2116.2415.72
0.55.3454.3353.8812.0812.08
0.588.2251.7353.418.919.19
0.591.1552.8852.366.366.49
1.076.2160.5359.6020.0620.65
1.078.5757.5356.6217.7218.04
1.081.0057.5255.6715.3415.37
1.084.0356.4256.2712.3912.29
1.05.6357.4656.4810.8011.30
1.09.3655.6755.088.239.48
1.02.8156.7654.735.975.95

It can be seen in Table 3. 

Regardless of the feed concentration, the size of the sieve aperture, and the length of the moment, the water content of the discharge is mostly about 55%. It can reach the moisture content required by high-temperature composting. 

The maximum water content of the discharge is 60.91%, and the minimum water content of the discharge is 49.71%. 

At the same feed concentration. Regardless of the mesh size, the overall trend is that the water content of discharge under a short moment is higher than that under a long moment. 

The solid content of effluent under short torque is lower than that under long torque. With the decrease of feed concentration, the solid content of effluent under long and short torque decreases gradually. 

Under the condition that the feed concentration of the raw material of the cold dewatering machine is basically the same. Compare the distribution of nitrogen and phosphorus in the solid and liquid after separation when the mesh screen with different apertures and operating at different moments. The results are shown in Table 4. 

No matter what kind of screen, the proportion of nitrogen and phosphorus distribution in solids under short moments is higher than that under long moments. 

Whether under a short moment or a long moment. The proportion of nitrogen and phosphorus distribution in solids of small pore sieve is higher than that of large pore sieve.

The distribution ratio of nitrogen and phosphorus in solids is the highest under the 0.3 mm mesh screen. 

The average nitrogen content is 19.15% and the phosphorus content is 20.65%. However, the distribution ratio of nitrogen and phosphorus in solids is the lowest under a 1.0mm mesh sieve, with an average of 7.14% and 7.38% respectively. 

Comparison of solid recovery rate under different aperture screens and different moment

It can be seen in Figure 2.

The solid recovery rate of the 0.3mm aperture sieve is the highest under the working condition of a short moment.  

The solid recovery rate of a 1.0mm aperture sieve is the lowest under the working condition of long moments. 19.02%.

Under the same aperture screen, the recovery rate of short-moment solids is higher than that of long-moment solids. This is mainly due to the greater pressure on the manure in the raw press screen under the long moment of force, which makes more small particles in the feces squeeze out of the screen.

Therefore, the recovery rate of long-moment solids is lower than that of short-moment solids. However, for different mesh screens, the solid recovery rate of the small mesh screens is higher than that of large mesh screens under long or short torque. This is mainly because the smaller the mesh diameter is, the easier it is to intercept small particles of solid.

Therefore, the size of the screen aperture of the cow-dung dewatering machine is the main factor limiting the solid recovery rate of the solid-liquid separator.  

Comparing the solid recovery rate and the distribution ratio of nitrogen and phosphorus in the solid after the solid-liquid separation of pig manure by the cow dung dewatering machine, it is found that: 

The distribution ratio of nitrogen and phosphorus in solids is lower than the recovery rate of solids. After solid-liquid separation by a solid-liquid separator, most nitrogen and phosphorus in pig manure enter the liquid.

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