Application and selection
of
1. Mixing functions
Mixing is a process for getting all ingredients blended
with each other by external forces so that a small unit
volume of the batch possesses the same composition
and characteristics as the entire mixture.
Mixing is an important link for ensuring compound
feed quality and improving feeding performance.
Meanwhile, the production rate of a mixer determines
the scale of a feed mill. Therefore, the mixer is one of
the most important machineries in feed industry.
2. The process steps that need mixing
There are two process steps that need mixing operation in a feed mill:
1. Premixing: It is to mix all micro-components needed for animal
growth such as added vitamins, minerals, medicines, etc. with a
carrier preliminarily before being added to the main mixture so as to
shorten the mixing retention of the complete compound feed, which is
predicated on the homogeneous distribution of micro-components. A
premixer is usually adopted for this purpose.
2. Final step mixing: All feed ingredients are weighed according to the
required proportions and fed into the mixer to be made into the
3. Mixing process
There are three main mixing modes on the basis of
different external forces: diffusion mixing, convection
mixing and shearing mixing. Additionally, there are
also the impacting mixing that is resulted by the
dispersion of each single ingredient particle impacting
with the mixer walls and the crushing mixing because
of the deformation and rubbing or kneading of material
particles.
4. Classification of mixers
In light of the weighing method of a proportioner,
mixers can be divided into the batch mixer and
continuous mixer.
On the basis of layout, mixers can be divided into
vertical mixers and horizontal mixers.
According rotor structure, mixers can be classified
as ribbon mixers and paddle mixers.
In accordance with the structure and working
principle, mixers can be divided into rotary drum
mixers and fixed trough mixers.
5. Twin-shaft paddle mixer
Batch Mixers
The twin-shaft
paddle mixer
consists of a
machine casing, an
outlet and its
sealing, an outlet
control mechanism,
rotors, a main drive,
an geared motor
and its base, an
pipe line for oil
addition, and a
safety guard shield,
etc.
Large access door:
convenient for inspection and cleaning
Shaft-end packing seal: When a new machine has
been used for 2 ～3 months, or when material
leakage has been found, the packing gland needs to be contracted for once so as to compensate the worn-out of the packing. As soon as the clearance between the packing gland and seat disappears, the packing should be renewed.
The fastening conditions of the connecting joints must be checked frequently for protecting against looseness, which will result in material leakage due to that the discharge gate can not be closed tightly.
This point was found easy to be damaged because of higher stress, now it has been improved.
5.1 Structure
The twin-shaft paddle
mixer consists of a
machine casing, an
outlet and its sealing,
an outlet control
mechanism, rotors, a
main drive, an geared
motor and its base, an
pipe line for oil addition,
and a safety guard
shield, etc.
Twin-shaft paddle mixer
1. motor 2. chain drive 3.paddle 4. inlet 5. liquid nozzle 6. sight hole 7. machine body 8. packing gland 9. discharge valve 10. agitating shaft
5.2 Sketch of material movement trace
The material
movement traces
show that
tumbling and
flowing
movements of the
materials coexist,
so the mixing
efficiency is very
good.
5.3 Duplicate-rocking-bar mechanism for
controlling the discharge gate
1. limit switch 2. rocking bar 3. connecting rod 4. universal driving shaft 5. duplicate rocking bar 6. left nut 7. nut 8. joint 9. cylinder
The position indicated by the solid line is the status for gate closing, and that indicated by the dot dash line is the status for gate opening.
When the gate is closed , the parts of 3,5,6,7 must be on a line.
When the gate is opened, these parts can not be on a line.
5.4 Selection principle
The twin-shaft paddle mixer features short mixing retention, gentle mixing
action and high mixing homogeneity. The mixing retention for dry
materials is about 45 s; mixing homogeneity can reach CV ≤5%; and
filling coefficient is as high as 0.4 ～1.
The mixer is a highly efficient machine, suitable for a wide range of materials,
into which multiple liquids can be added, featuring very good mixing
effects, but residue rate is comparatively higher.
In case more liquid is to be added, the discharge gate must be cleaned
frequently to avoiding stock built-up by the gate, otherwise the gate can
not be closed tightly resulting in material leakage.
5.5 Main data for selecting Series SLHSJ mixers
Model Effective Volume (m3) Capacity (Kg/batch) Time/Batch Mixing homogeneity (cv) Power (KW) Weight (Kg) SLHSJ10A 10 5000 45S～60S (It can be prolonged properly according to different materials.) ≤5% 55 11340 SLHSJ8A 8 4000 45 8800 SLHSJ7A 7 3500 45 8650 SLHSJ4W 4 2000 30 6720 SLHSJ3A 3 1500 22 5600 SLHSJ2A 2 1000 18.5 5180 SLHSJ1A 1 500 11 2420 SLHSJ0.5A 0.5 250 5.5 1360 SLHSJ0.35A 0.35 175 4 1210 SLHSJ0.2A 0.2 100 2.2 720 SLHSJ0.1A 0.1 50 2.2 620 SLHSJ0.06A 0.06 25 0.75 3706. Premix mixer
6.1 Production characteristics of premix
Compared to normal compound feed manufacturing, more
kinds of ingredients with much complicated components are
needed for the production of premix, there is a great disparity
in their amounts used, and some of them are corrosive and
toxic, so they must be proportioned
accurately, mixed
homogeneously, and packed tightly.
That’s why premix should
be produced by special equipment.
6.2 Requirements for premix mixer
● The mixing homogeneity must be high, which is helpful to carrying capability of premixed ingredients;
● There should be no residue inside the premix mixer after discharging, and the machine should feature self-cleaning function, easy manual cleaning and is free of cross contamination;
● There should be no material leakage at the shaft ends of the premix mixer, and no material attached on the rotor and the inside walls of the trough;
● Special nozzles provided can apply paraffin wax by means of compressed air;
● The clearance between rotor and casing should be adjustable;
● The distance from the top of the rotor to the roof of the mixer casing should larger to increase the spray area.
The mixer for common compound feed can never be used directly as a premix mixer!
According to the requirements on premix mixer in premix production, we have developed a special premix mixer (see the fig. ), which is an
Motor base Access door Air return pipe Air holder for spray Inlet for accessory ingredient s Inlet Top inspectio n door Right pressure release vent Pressure release vent Main shaft Liquid addition Connected to a proportioning scale or a dust filter
nozzle
nozzl
Full-length
discharge
gate
*
The full-length discharge gate is also adopted in common twin-shaft paddle mixers.6.3 Characteristics of premix mixer
1. The packaged design of air return pipe facilitates transportation; the air vents at two sides balance the difference between the inside
and outside pressures during feeding operation very quickly;
2. The full-length double-leaf discharge gate in the trough bottom features quick discharging and little residue;
3. The patented technique of our unique integral air sac used for
sealing the discharge gate can make up the deformation of the gate, featuring reliable sealing and leakage free;
4. The lifting type liquid application device results in convenient and fast cleaning and replacement of the nozzles;
5. The rationally designed spraying piping is strong in self-cleaning capability;
6. The large access door makes things convenient for the operator to clean the inside;
6.4 Precautions for operating a premix mixer
Prior to operating the mixer, it is a must to regulate the
pressure release valve of the air sac before hand, check the
pressure gage, so that the pressure inside the air sac around
the discharge gate does not exceed 0.12 MPa, and during
operation frequently check the indicated value of the pressure
release valve to protest against air sac damage due to
overpressure.
When the air sac is full of air, it is not allowed to operate the
discharge gate manually so as to avoid damage.
Many characteristics of the premix mixer can also be found in a
common twin-shaft paddle mixer.
6.5 Main data for selecting Series SYHSJ premix mixers
model Effective volume (m3) capacity (kg/batch) mixing retention per batch (s) Mixing homogeneity (cv ≤%) power (kW) weight (kg) SYHSJ0.5 0.5 350 120~240 (can be prolonged properly according to different materials.) 5 7.5 1360 SYHSJ1 1 700 5 11 2300 SYHSJ2 2 1400 5 22 5200 SYHSJ4 4 2800 5 37 67207. Double-cycle Paddle Mixer
(1.) main component parts
1. machine body
2. rotor
3. access door
4. discharge gate
5. chain drive mechanism
and package guard shield
6. oil adding device
7. top cover
Double-cycle Paddle Mixer
Patented rotor Split type machine body Large access door oil adding device inlet air current balancing hole Geared motor and guard shieldAir sac for sealing discharge gate
Top
cover
Rotor
1st-cycle large paddle 2nd-cycle small paddle Main shaft gland Lower head
The patented
new double-cycle
rotor, ensuring a
mixing retention
of 45
～60 s, and
the mixing
homogeneity of CV
＜5% (can be up
to 3%)
on the
basis of a mixing
ratio of 1:100000.
Adjustable gapRotor
Fast flow zone
Slow flow zone
Full-length discharge gate and its sealing air sac
Four air sacs are
used for sealing the
discharge gate. They
can make up the
deformation of gate
and ensure airtight
without any material
leakage, the inflation
pressure inside the
air sac being
0.08MPa~0.12MPa.
The full-length
discharge gate
results in reduced
residue.
compresse d air intake Air sacLifting type oil adding device
Compressed air intaking
Liquid intaking
Atomizing spray ejector
Liquid ejector Compressed
air ejector Compressed air ejector
7. Double-cycle Paddle Mixer
(1) Machine characteristics
1.The novel patented double-cycle rotor ensures a mixing retention of 45～ 60 s and the mixing homogeneity of CV ＜5% (can be up to 3%) on the basis of a mixing ratio of 1:100000;
2.The discharge gate is as long as the mixer tough, ensuring complete exhaustion of the materials；
3.The gap between the paddle and the inside wall of the casing is adjustable;
4.The residue ratio is less than 0.05%～0.15%，which effectively protect product from cross contamination;
5. The large access door makes it easy to clean the mixing chamber and to renew the paddles;
6. The discharge gate is sealed by formed rubber air-sacs so as to ensure the air-tightness of the gate. During opening and closing the gate, there is no friction between the gate and the sac, thus extending the service life of the sealer;
7. The atomized spray injectors or nozzles used in the oil addition device greatly improve the atomizing effect.
(2) Application range
Series SJHS double-cycle paddle mixers are widely
used for mixing powdery, granular, flaky, lumping
and miscellaneously shaped or sticky materials in
feed, grain, food, chemical, pharmaceutical and farm
chemical industries, etc. They can also be used for
drying and cooling operations of various materials.
Series SJHS double-cycle paddle mixers are made of
anti-corrosive materials, so they can also be used
for premix production.
(3) Data for selecting Series SJHS Mixers
model Effective volume (m3) Capacity (kg/batch) Mixing homogeneity (CV ≤%) mixing retention per batch (s) power (kW) SJHS0.2 0.2 100 5 (up to2~3) 45-60 (can be prolonged properly according to different materials) 3、4 SJHS0.5 0.5 250 5.5、7.5 SJHS1 1 500 11、15 SJHS2 2 1000 18.5、22 SJHS4 4 2000 37、45 SJHS6 6 3000 559. Operation and maintenance of mixers
(1) Operation and maintenance
Prior to production operation the mixer should be put into idle running to see if it runs smoothly and stably without any abnormal vibration, and discharging mechanism should also be checked for normal working.
Before operation, start up the geared motor firstly, then start feeding after the rotor gets into normal running.
The level of the stock bed inside the mixing chamber can be neither lower than the axis of the main shaft nor higher than the top of the rotor.
Additives can only be added when half batch of the main ingredients have already been fed in the machine, and oil spraying should not be started until all the main ingredients have fed in, and after the oil application is finished the ingredients can not be discharged until they have been mixed for a proper while.
When stopping the machine, no oil residue is allowed inside the oil adding pipe so as to avoid pipe blocking due to oil solidification.
No metal impurities can be contained in the ingredients so as to protest the paddles from damage.
The operation of the geared motor, cylinder and other accessory elements should coincide with regulations in the operation manual.
10. Operation and maintenance of mixers
(continued)
(2) Maintenance
The discharge mechanism must be kept running freely and clean.
The lubricate in all bearings should be renewed periodically. And the
lubricate should be sodium-base grease.
The driving chain should be properly oiled and rinsed periodically.
Name of the reducer grease: molybdenum sulfide-2 or ZL-2 lithium
base grease.
When the machine has run for 500 hours after the first lubricating, the
grease should be renewed. Then during the continuous operation of
the machine, the grease should be renewed once every half a year
( based on a 8-h working system). If the working time is longer, the
grease renewing intervals needs to be properly shortened.
11. Mixer performance evaluation
It is neither possible nor necessary to mix all the
ingredients into an absolutely homogeneous state.
Thus there should be unified standard to judge the
mixer performance, that is the coefficient of variation
of mixing homogeneity (i.e. CV value). The lower is CV
value, the better the mixing effect will be. In light of
Chinese standard, the CV value for a common mixer is
≤7%, and that for a premix mixer is ≤5%.
The determination of mixing homogeneity
CV value can be calculated by means of the
following formula:
CV=S/X ×100%
In which,
S - standard deviation of the content of the detected
ingredient in each sample of mixture;
X - average value of the content of the detected
ingredient in each sample of mixture
3.3 Maintenance
3.1 Periodically check and clean the filter, heat the liquid
tank for periodic blow-off.
3.2 Check the solenoids frequently to see if they act freely,
and to see if the system pressure is increased.
3.3 Check the piping frequently for any leakage.
3.4 For a long-term shutdown, the system should be
cleaned to avoid blockage.
1. Liquid storage tank 2. heat insulating layer 3. geared motor for output 4. filter 5. pneumatic ball valve 6. pilot
electromagnetic valve 7. flow meter 8. geared motor for input 9. coupling 10. geared pump 11. manual ball valve
The maximum adding amount per batch for this
system is 60 Kg, which is weighed by means of an
electromagnetic flow meter.
3）Post coating system
The continuous liquid coater positioned after pelleting
or extrusion is suitable for spraying the liquids such as
oil, enzyme preparations, vitamins, antioxidant, amino
acids etc. It can effectively protect these nutritive
substances and medicines against heat damage.
There are models of surface coaters made in Muyang:
Main components of the surface coater
The coater mainly consists of the following parts:
1.differential scale
2.conveyor
3.drum part
4.liquid output pumping system
5.liquid coating pipe line and nozzles
6.automatic control unit
Technical data for liquid coater
selection
model SYPL15A SYPL25A
Capacity (t/h) 0.5～7 0.8～15
Motor power for drum (Kw) 2.2 3
Motor power for feeding（kW） 1.1 1.1
4）vacuum coating system
1.The limits of surface coating technology:
1) liquid adding ratio <6%
2.The obvious superiorities of vacuum
coating technology:
1) high liquid adding ratio (35%-40%)
3.Technological process
1. Vacuum pump 2. vacuum tank 3. dust filter 4. gate 5.scale 6.vacuum valve 7. feeding valve 8.vacuum mixer 9.electromagnetic valve 10. liquid scale 11.liquid tank 12.outtake valve
4. Production flow
E F E Pellet mill or extruder drier cooler Vacuum coater sifter bin5. Experiment site
The experiment
of vacuum
coater in
Muyang Testing
Center
Touch screen
of the
computer
control
system
6. The schematic diagram for installing Muyang
Series SYPZ vacuum coater
7. Overall performance of Muyang Series
SYPZ vacuum coater
1.capacity：2.5t/h, 5t/h, 10t/h；
2.vacuum degree≤150mbar；
3.product homogeneity after oil coating CV≤7%；
4.weighing accuracy of batching scale＜0.3%；
8. Working process of Muyang SYPZ
vacuum coater
1.feeding 40s
2.vacuumization 1.5min
3.liquid addition 1.5min
4.vacuum release 1min
5.discharging 50s
5）Other equipment for liquid treatment
（1）liquid proportioner / mixer
● Available models are SYPC100B,SYPC200 and SYPC400，their
adding amount per batch are 100Kg, 200Kg and 400Kg
respectively;
● Three liquids can be added simultaneously, and this number
can be increased. Experimentally, six liquids have already
been tried for simultaneous addition；
Outline drawing of the
main machine of the
liquid proportioner / mixer
3 liquid intakes
load cell
liquids mixing device
Mixing drum, with an outside heat water insulating layer output pump filter Weighing drum
5）Other equipment for liquid treatment
（2）water adding equipment
For adding water into a batch mixer so as to
improve conditioning effects.
SSTZ60 water adding system
1. Electromagnetic valve for water intake
2. water storage tank 3.filter 4.self-priming pump 5. pressure gauge 6. overflow valve
7. flow meter 8.electromagnetic valve for water spraying 9. power panel 10. intelligent flow controller