Rotary Vacuum Filter Accessories Capacity Calculation |SugarTech
In this article briefly discussed about rotary vacuum filter capacity requirement of accessories like mud pump, mud mixer, drum filtering areas, vacuum pumps, condenser with entertainment separators.. etc. And also explained with examples for capacity calculation.
For the equipment details of the rotary vacuum filter purpose please go through the below link
Vacuum Filter Description in sugar industry | Optimization of Sugar Loss
Description of Rotary vacuum filter main accessories:
Mud Pump:
Mud pump is required for pumping the mud from mud tank to mud mixer or mud recirculation. Primary mud has poor fluidity and will have difficulty in optimizing the filter station. If it is necessary to pump the primary mud the pumping action should be as gentle as possible to prevent breakup of the fragile floc particles. The high shear characteristic of centrifugal pumps, as well as flow through narrow pipes and valves orifice should be avoided. It is better to use screw pumps, Positive displacement plunger or diaphragm pumps are more acceptable for this application.
Generally, mud in the clarifier is considered to be about 20 to 25% of the total juice handled.
Mud mixer :
The equipment for mud mixing usually consists of an elongated open mixer vessel stirred with a helical
ribbon agitator. The rotation speed is considered 20 to 24 rpm and the lip speed 0.7 to 0.9 m/sec if paddle arms are used. The bagacillo and mud added at one end of the vessel, and the outflow is taken from the other end to the mixer. Normally the mud mixer is set horizontally.
Generally, mud mixer retention time takes 8 to 10min on the mud percent of juice flow rate. The bottom portion of the mud mixer has semi cylindrical shape with 30% volume of the total mud mixer. The length of the mud mixer minimum will take 3.5 to 4 mtrs for proper mixing.
For the Role of Bagacillo in vacuum filter, bagacillo cyclone Capacity Calculation purposes please go through the below link
Bagacillo Screens, blower & Bagacillo Cyclone Sizing Calculation
Vacuum filter drum :
The filter area follows different figures in different countries. Generally, it is considered 0.5 to 0.7 m2/TCH.
A filtration rate varies according to wash water rate. Generally, it has 250 to 400 lt/m2/hr.
The filter cake weight varies according to the cake thickness. Generally, it having 60 to 120 kg / m2/hr.
Filter cake wash water quantity consider 100 to 150% on weight of filter cake or 4 to 6% on cane.
Vacuum Pump and Condenser:
Air entering into the system is considered 0.3 to 0.4 m3/min./m2 area of the filter drum. According to this we estimate the vacuum pump capacity.
Condenser capacity is considered according to mud temperature and filter juice temperature.
The sizing of lines from the light and heavy filter mound to condenser by considering the 40 m/sec velocity.
The density of the humid air from the condenser to vacuum pump is 0.2kg/m3.
Model example for calculation of Rotary vacuum filter main accessories:
| S.No | Description | Values | UOM | Remarks |
| Required Data for calculation | ||||
| 1 | Crushing Capacity | 230 | TCH | |
| 2 | Juice % cane | 120 | % | 115 to 125% |
| 3 | Mud Juice % cane | 20 | % | 15 to 20% |
| 4 | Vacuum filtering area | 0.6 | m2/TCH | |
| 5 | Filter cake production | 60 | kg/m2/hr | Approx. 60 to 120 |
| 6 | Filtration rate | 250 | Lt/m2/hr | 250 to 400 |
| 7 | Cake wash water quantity | 100 | %on filter cake | 100 to 150% |
| 8 | Air entering into the system | 0.3 | m3/min/m2 | 0.3 to 0.4 |
| 9 | Humid air density | 0.2 | kg/m3 | |
| 10 | Velocity of vapour and humid air | 40 | m/sec | |
| 11 | Mud tank retention time | 10 | min | 8 to 12 min. |
| 12 | Mud tank retention mixer | 10 | min | 8 to 12min. |
| 13 | Mud juice temp. (In VF trough) | 85 | oC | The difference between mud and filter juice is approximately 15 to 20oC |
| 14 | Filter juice temperature | 65 | oC | |
| 15 | Condenser water inlet temp. | 32 | oC | The difference between inlet and outlet water is approximately 5 to 10 oC |
| 16 | Condenser water outlet temp. | 38 | oC | |
Calculation Part:
- Juice handling of clarifier = 230 x 120% = 276 T/hr = 276/1.06 = 260M3/hr.
- Mud juice flow available = 260 x 20% = 52M3/sec.
- Mud pump Capacity required = 52 x 120% = 62M3/hr (Head required as per the elevation of mud mixer).
- Mud tank capacity required = 52 x 10 /60 = 9M3.
- Mud mixer capacity required = 52 x 10 /60 = 9M3.
- Vacuum filter drum sizing requirement = 230 x 0.6 = 138m2. ( It is better to go 2 no.s of 12′ x 24′ sizing) ( 8′ x 16′ = 36m2, 10′ x 20′ = 58m2, 12′ x 24′ = 84m2, 14′ x 28′ = 121m2 ).
Now Take a 12′ x 24′ Rotary Vacuum Filter drum and calculate its accessories
- Filtration area of the vacuum filter = 12′ x 24′ = 904Ft2 = 84m2 ( 1 ft2 = 0.0929m2 ).
- Filter cake production = 84 m2 x 60 kg/m2/hr = 5039 kg/hr
- Filter juice quantity obtained = 84 m2 x 250 Lt/m2/hr = 20995 Lt/hr = 21 M3/hr. = 21 x 1.06 = 22.3T/hr.
- Cake wash water quantity required = 5039 kg/hr x 100% = 5039 kg/hr.
- Vapour production = (Q x Cp x ΔT / λ) = 22.3 x 0.92 x (85 – 65 ) / 520 = 0.787 T/hr.
= 0.787 x 1000/3600 = 0.219 kg/sec.
= 0.219kg/sec x 3.14 M3/kg = 0.746 M3/sec.
- Air load on this system = 84 m2 x 0.3 m3/min/m2 =25.19 m3/min.
= 25.19/60 = 0.42 m3/sec.
=25.19 x 60 = 1511.66 m3/hr.
- Weight of the humid air = 1511.66 m3/hr x 0.2 kg/m3 = 302.22 kg/hr.
=0.3022 T/hr.
- Total load on the condenser (vapour + humid air) = 0.746 M3/sec. + 0.42 m3/sec = 1.166 m3/sec.
= 0.787 T/hr + 0.3022 T/hr = 1.090 T/hr.
- Pipeline dia from Hy/Lt filter mound to condenser ( Q = AV)
= (1.166 m3/sec) / (40 m/sec) = 0.029 m2
= Sqrt ( 0.029 /0.785) = 0.192mtr = 200mm.
- Condenser cross-sectional required = 1.090 T/hr x 0.16 m2/ ton/hr = 0.174 m2
i.e Dia of condenser = sqrt (0.174/0.785) = 0.471 mtr = 500mm.
- Vacuum pump capacity requirement = 1511.66 m3/hr x 120% = 1814 m3/hr.
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