knelson concentrator

Alireza Mirzaeian & Masoud Abdollahi

1.Motivation of using Knelson separator

2. Introduction

3.Technical solution

4.Defining capacity and separation quality

5.conclusion

Presented by Alireza mirzaeian

Treatment of flotation slurries, waste waters containing a large amount of: solid particles, dissolved air or gas, chemicals etc.

There are numerous technical solutions and devices which use the centrifugal force for: separation, classification, dewatering, etc., in mineral processing, waste water treatment, etc.

Motivation of using Knelson separator

introduces improvements in the sphere of self-suction, continual discharge and product transport.

this new solution can be used for the treatment of flotation tailings containing large amounts of finest particles.

Motivation of using Knelson separator

2. Introduction

5.conclusion

Technological, economical and ecological requirements impose the need for extraction of useful components or for cleaning of these mixtures. Separation is one of many processes for removal of particles (solid or liquid) from multi-phase mixtures.

According to the dominating force, there are four basic concepts of mechanical separation: gravity, centrifugal, impingement and filters

Introduction

gravitational separators are used for the primary separation due to the settling velocity of the solid particles which are low

the final product often does not satisfy the needs of the technological approach

Introduction

The weaknesses of the gravitational separation are removed using the inertial procedures where the gravitational acceleration (g, m/s2) is interchanged with centrifugal acceleration (ω2r, m/s2).

Introduction

The basic advantage of centrifugal separators lies in the fact that the settling velocity, which with gravitational separators for fine (+ 2 to − 50 μm) particles revolves from 10− 9–10− 4 m/s, increases for 500–30,000 times

Introduction

The increase of settling velocity shortens the particle settling time, in the rotor of separator, which results in smaller separator dimensions, at the same capacity

often, separators are used in the flotation of mineral raw materials, dewatering, thickening, waste water treatment, regeneration of chemicals used in the flotation process, etc.

Introduction

centrifugal separators have long been present in the processes of waste water treatment, crude oil and natural gas treatment

Significant shortcomings of centrifugal separators are the complex construction, wearing sensitivity, vibrations etc.

Introduction

The problem with which the flotation in “Suva Ruda”-Raškamine comes across, is a great amount of solid particles (clay) in the return water in the flotation cycle of lead and zinc ore.

Introduction

The existing technical solution, settling in the thickener, has proved inefficient.

Particle of +0.053 mm size relatively easily settle in the primary treatment in the thickener and are transported to the deposition place via the slurry pumps.

Introduction

Since the particle settling time −0.053 mm in the thickener was too long, there were attempts to accelerate the settling process by applying the coagulation procedure. It turned out that this solution, coagulation, does not give good results.

Introduction

2. Introduction

5.conclusion

The separator will be used for the secondary treatment of the slurry with solid content 100%–50 μm and a significant amount of free and dissolved air (5–8%);

the separator should be part of the facility for the continual separation process and the transport of flotation tailing and recycled water.

Technical solution

perceived weaknesses were removed during the design and the making of the following prototype.

Technical solution

Fig. 1, Fig. 2: product feed device with vacuum pump, rotor with disk stack insert, pump for tailing, pump for water, motor with frequent regulator, ancillaries system and measuring equipment.

Technical solution

Fig.1:Centrifugal Separator-Prototype.

Technical solution

Fig.2:Centrifugal Separator-Cross section.

Technical solution

The rotor of separator consists of two parts. The lower half, of the rotor, with disk stack insert is connected to the motor via the belt drive. The insert in the rotor, with its disks, splits the working space into thinner segments in which the separation process is developing easier, i.e. achieves higher quality of finer solid particle separation.

Technical solution

on the lower half of the rotor, are the jets used for the drainage of the separation products (tailing, sludge). The rotor drainage is controlled by opening and closing the plugs which are part of the rotor construction.

Technical solution

The periphery edge, of the lower and upper half of rotor, and the jets, forms the impeller of the pump for tailing (slurry).

The lower half is connected to the upper half of the rotor by bolts. The upper half holds the impellers of pump, for clean water, and vacuum pump.

Technical solution

The installation of the vacuum pump, in the separator construction, is justified by the suction process facilitation, which is significant for the treatment of mixtures: solid–liquid–gaseous.

Technical solution

The sealing, of the periphery edge of the: rotor (impeller of the slurry pump), the water pump's impeller and impeller of the vacuum pump are realized using mechanical seals.

enables achieving of great rotation speeds, and the rotor stability is significantly improved. As a lubrication fluid, in the zone of sliding rings, water that has been acquired as separation product, is used.

Technical solution

The sealing, of the periphery edge of the: rotor (impeller of the slurry pump), the water pump's impeller and impeller of the vacuum pump are realized using mechanical seals.

enables achieving of great rotation speeds, and the rotor stability is significantly improved. As a lubrication fluid, in the zone of sliding rings, water that has been acquired as separation product, is used.

Technical solution

By introducing water in the lubrication process, the density of the slurry is controlled, prevents the pollution and reduces the separation expenses.

Technical solution

Fig.3:Forces acting on a particle Due to centrifugal acceleration.

Technical solution

The solid fraction gets caught on the largest diameter of the rotor, goes through the jets and through the impeller, of the slurry pump, is transported to the desired place. The density of the slurry is controlled by the water flow, from the mechanical sealing of the rotor edge. The drainage of the solid fraction is controlled by a device with plugs that are part of the rotor construction.

Technical solution

The liquid fraction (water) gets caught on centripetal pump and is directed to the water pump's impeller. The easiest fraction (air) gets caught at the place closest to the rotation axis and is directed to the vacuum pump.

Technical solution

Innovations introduced in the separator construction were as following:

the periphery edge of the upper and lower half of rotor is constructed as an impeller for the pump for tailing transport; the sealing of impellers is done by mechanical seals, which are, also, axial bearings for rotator; by the water, used for lubrication and cooling in mechanical seals, we

control the density of the slurry; by introducing the vacuum pump into the separator construction, suction of mixtures (solid–liquid–gaseous) is facilitated.

Technical solution

The advantages of thus formed solutions are as following:

all types of mixtures can be treated with central charging and self-suction; one engine controls the power of several sections; combining radial-axial bearings, great rotation speeds can be achieved

together with excellent rotor stability.

Technical solution

Among the weaknesses one should mention:

the complex construction; expensive production and wearing of the separator

elements which are in contact with the solid material.

Technical solution

2. Introduction

5.conclusion

Presented by Masoud Abdollahi

The feed flow rate and the critical diameter of the particle are the two main indicators of how successful the separator construction is.

the solid particle size (ds, m), settling velocity (cg, m/s), length of settling road (L, m), settling time (t, s), and viscosity (η, Pas) of the feed fluid has a great influence to the separation feed flow rate and quality of separation.

Defining capacity and separation quality

the settling velocity, in the sphere of centrifugal acceleration, is defined by the following equation:

The relation between centrifugal settling velocity (cc) and the Stokes settling velocity (cg) is defined by the following equation:

In order to estimate the separation feed flow rate in the centrifugal separator the ∑-concept is often used. The theoretical feed flow rate (qt) is defined as follows:

The critical solid particle diameter (dp) is the diameter of a particle that is separated according to the defined rotation speed and diameter of rotor.the critical particle diameter (dp1) is defined, according the Σ-theory, as:

presumption that:

the speed of the mixture is equal to the rotor speed; the particle concentration is small so the settling velocity is

seen as settling of unit particle in an unlimited space;the particle speed is even throughout the whole settling

process; the particle movement in the gap between the disks is

laminar and symmetrical.

the initial presumption that in the rotor 50% of the solid particles (–dp) are removed, makes the actual capacity significantly different from the theoretical:

Thickness (vertical) of fluid in gap is:

Change of speed of particles, in a thick layer, in the direction of disks periphery is:

the particle critical diameter is:

Moving practically (tgθ = g/ω2r b b 1) radial in the gap between the disks, the solid particle touches the inner disk side, Fig. 3, While sliding on it comes to the disk's exit edge (radius r2).

The minimal values of the boundary layer thickness for laminar and turbulent flow are:

The optimal gap size (topt. = δopt.) between the disks is defined as following:

It is common that this gap, on industrial facilities is (t=0.5– 3 mm).

Leaning, on the inner side of the disks, the particles move at the speed of:

2. Introduction

5.conclusion

The new technical solution that we are hereby presenting when compared to the existing solutions has the following advantages:

The possibility of self-suction, that with the possibility of continual transport of the separation products, becomes acceptable to a great number of users;

The separators in general, as well as this technical solution, have the possibility of achieving high levels of acceleration (500– 30000 g), which makes it acceptable for fine and ultra-fine separations;

conclusion

The new technical solution that we are hereby presenting when compared to the existing solutions has the following advantages:

The facilities with these separators are of smaller dimensions, which directly influences, the amount of investments (example: the relation of thickener dimension and the separator of the same feed flow rate);

The vacuum pump, which is part of the separator construction, extends the sphere of application of these separators to the treatment of mixtures: solid–liquid–gas, liquid–gas, solid–gas. This is significant for the treatment of waste waters, natural and industrial gases, etc.

conclusion

The model for calculating the separation capacity and quality, considers a great number of factors:

characteristics of the treated mixture (settling velocity, viscosity, solid concentration etc.); separator construction characteristics (diameter, particle path- way length, etc.); working regime of separator (rotation speed).

conclusion

It should be expected that by reducing the quantity of the solid in the overflow (return water), flotation reagents will be saved, etc.

conclusion

Further attention should be paid to the removal of the weakness spotted on the separator construction (mechanical seals and the device for the opening–closing of the jets), improvement of the vacuum pump construction and precise definition of its feed flow rate.

conclusion

special attention should be paid to the separator's operation on the activities (treatment of waste waters, waste oils, etc.).

conclusion

ThanksPresented by Masoud Abdollahi

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