How to design and calculate the tube settler?

 

 

How to design and calculate the tube settler?

 

-The Technical Description Of Honeycomb Tube SettlersSedimentation Tank 

 

According to the sedimentation principle, at a certain flow rate q and a certain particle sedimentation velocity u Under the condition of, the sedimentation efficiency e is proportional to the plane area a of the pool, i.e. E=U A/Q. The pool is divided into n intervals in height, which increases the plane area of the pool, shortens the settling time and improves the settlingefficiency.

 

Combined with the need of sludge discharge, the inclined plate is added to the inclined plate sedimentation tank, which increases the water flow area and wet area of the tank, reduces the hydraulic radius, reduces Reynolds number and turbulence of water at the same horizontal flow rate, and has good sedimentation effect.

 

Inclined tube sedimentation tank is a sedimentation tank in which many parallel inclined tubes with smaller intervals are installed. The sedimentation principle of inclined tube sedimentation tank is the same as that of inclined plate sedimentation tank. On hydraulic condition, the hydraulic radius of inclined tube is smaller than that of inclined plate, so Reynolds number is lower and sedimentation effect is more remarkable. Inclined tube sedimentation tank has small tank capacity and saves floor space.It has been adopted by many water plants at home and abroad and accumulated a lot of experience in operation and management. The problem is that the maintenance and management are complicated, and the inclined plates of inclined pipes need to be cleaned and replaced regularly. Due to the short settling time of inclined plate and inclined tube sedimentation tank, attention and management should be strengthened when water quantity and water quality change during operation.When using this kind of sedimentation tank, attention should also be paid to the perfection of flocculation and the reasonable arrangement of sludge discharge.

 

① There are three main water flow directions in inclined plate sedimentation tank: upward flow, lateral flow and downward flow.

② The designed particle settling velocity μ of inclined plate sedimentation tank, and the liquid level load should be determined by experiment or referring to the operation experience of waterworks under similar conditions. The designed particle settling velocity can be 0.16~0.3mm/s, the liquid level load can be 6.0 ~ 12 m/(m h), and the lower limit value should be adopted for low temperature and low turbidity water.

 

 

Tube Setter Design Case 1

-Design and calculation of tube settler sedimentation tank(lamella water treatment)

 

Design conditions: water consumption is 15000m³/d.

The influent concentration is 280mg/L.

Sludge water content 97.50%

Effluent suspended solids concentration 30 mg / L

Design parameter:

The number of sedimentation tanks n = 4

Surface load of sedimentation tank: q = 2.4m³/(m²·h)

The diameter of inclined pipe is 100 mm

The length of inclined pipe is 1.0m

The horizontal angle of inclined pipe is 60^o

 

Design calculation:

 

1. Surface area of sedimentation tank

 

Water consumption q = 15000m³/d=625m³/h=0.174m³/s

 

Number of sedimentation tanks n = 4

 

Surface load Q₀= 2.4m³/(m³*h)

 

2. Plane size of sedimentation tank 

 

3. Residence time in tank

 

Height of clear water layer in the upper part of inclined pipe area H₂=1.0m

 

Vertical height of inclined pipe H₂=1.0m

 

4. Required volume of sludge

 

Sludge storage time t = 24h

 

The influent suspended solids concentration C₁= 280mg / L = 0.28x10^-3 t/m³

 

The effluent suspended solids concentration C₂= 30 mg / L = 0.03x10^-3 t/m³

 

Sludge densityγ=1t/m³

 

Moisture content of sludge

 

 

5. Sludge hopper volume

 

A square hopper is set at the bottom. The side length of the upper area is 8.5m, the side length of the lower area is a₂= 1.0m, and the slope degree is 50

The volume of the sludge hopper is V₁=122.63m³.

∵ V₁>V

∴Can meet that requirement of sludge storage.

 

6. Total height of sedimentation tank.

 

Ultra-high h₁of sedimentation tank = 0.3m.

 

Buffer layer h₄at the bottom of sedimentation tank = 1.0m.

 

7. Design of inflow tank and water distribution hole.

 

Strip-shaped flat-bottom grooves are adopted, and water distribution holes are arranged at equal intervals: Hole size 200mmx200mm

 

Inflow tank: let the width of inflow tank be B=1.0m, and the flow velocity in the tank be v = 0.25m/s. There are two water tanks in total, and every two sedimentation tanks share one water tank, so the water depth in the tank is

 

Average flow velocity of water holes v=0.25m/s,

 

Then the number of water distribution holes , take 5.

 

Hole spacing l =8.5/5=1.7m

 

 

8. Triangle weir calculation:

 

The triangle weir height is 0.10m, the water depth of the triangle weir is 3/5 of the weir height, that is, h=0.06m, and the weir angle is 90^o, then

 

Then

9. Check solid load.

Meet the solid load requirements.

③ Inclination angle o: It varies according to the materials and particles of the inclined plate, and it is usually 60 for the convenience of mud discharge.

④ plate distance p: that is, the distance between two inclined plates, and lateral flow inclined plate p is generally 80~100mm; The length of single-layer inclined plate should not be greater than 1.0m.

⑤ velocity v in plate: calculated according to surface load when flowing upward; The lateral flow can refer to the horizontal velocity equivalent to the horizontal sedimentation tank, which is generally

10~20mm/s; When flowing downwards, it can be calculated according to the downward surface load.

⑥ In the pool of lateral flow inclined plate, in order to prevent the water from passing through the inclined plate, a choke wall should be set, and the top of the inclined plate should be higher than the water surface.

⑦ In order to distribute and collect the water evenly, the inlet and outlet of the inclined plate sedimentation tank in lateral flow should be provided with rectifying walls. The opening rate of the rectifying wall at the inlet shall be such that the flow velocity of the through hole is not greater than the flow velocity at the outlet of the flocculation tank, so as to avoid floc breakage.

⑧ Punched pipe or mechanical sludge discharge equipment is generally used, and the design of perforated pipe sludge discharge is the same as that of general sedimentation tank.

(2) Key points of inclined pipe process design

① The cross section of inclined pipe is generally honeycomb hexagonal, and its inner diameter is generally 25 ~ 35mm.

② The diameter of inclined pipe is 30 ~ 40mm, the length of inclined pipe is generally about 1000mm, and the horizontal inclination angle isθ60 ° is often used.

③ The height of clear water area in the upper part of inclined pipe should not be less than 1.0 m. The higher clear water area is conducive to the uniformity of water outlet and the reduction of sunlight impact

and algae propagation.

④ The height of water distribution area at the lower part of inclined pipe should not be less than 1.5m.In order to distribute water evenly, perforated wall or grid should be set at the inlet of sedimentation tank.

⑤ The height of the sludge area should be determined according to the amount of sediment, the concentration degree of sediment and the way of sludge discharge.The sludge discharge equipment is the same as the horizontal flow sedimentation tank, and the perforated sludge discharge or mechanical sludge discharge can be used.

⑥ The effluent system of inclined tube sedimentation tank should make the effluent of the tank uniform, and perforated pipe or perforated water collecting tank can be used for collecting water.

⑦ The liquid level load of inclined tube sedimentation zone should be determined according to the operation experience under similar conditions, which can be 5.0 ~ 9.0 M²/(m²·h)