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1 Introduction

The ring die pellet machine is a key equipment in the production of pellet feed. It combines the various powdered feed into pellets, which changes the physical and biochemical properties of the feed, improves the feed utilization rate and feed palatability, and is a modern feed. Import ant equipment essential to the plant. Therefore, whether the performance of the pellet machine is good or not directly affects the quality of the pellet feed, which requires attention to several main technical parameters when designing or selecting the pellet machine.

2. Ring mold speed

There are four issues to be considered when designing the ring mold speed: ① granulation output: it has no direct or inverse relationship with the speed, and there is an optimal speed range corresponding to the optimal output; ② particle forming rate: too high a speed is easy to throw the compressed particles Crushing and reducing the forming rate is equivalent to a decrease in output; ③ Different feed formulas correspond to different speeds to suppress high-quality feed; ④ Ring mold inner diameter size, the centrifugal force is generated during the operation of the ring mold, the higher the speed, the greater the centrifugal force, which affects the particles Machine stability. Based on the above factors and the experience of manufacturing pellet machines in the world, the rotational speed of the ring die should be determined by the linear velocity of the inner diameter of the ring die. The general linear velocity range is 2.5 to 7.5 m/s. The linear speed of the gear drive is low, and the linear speed of the belt drive is high, which is determined by its transmission mechanism.

Formula for calculating the linear velocity of the inner diameter of the ring die:

V=πnd/60(m/s)

Then the available ring mode speed n=60v/πd(r/min)

In the formula: D is the inner diameter of the ring die (m)

Take a certain model of pellet machine as an example: (belt drive, 55KW)

Inner diameter of ring die: D=350mm=0.35m

Line speed selection: v=5.2m/s

Then the ring mold speed: n=60×5.2/π0.35=284 (r/min)

This is in accordance with the ring die speed range of 100 to 400 r/min empirical parameters. Some models are equipped with a speed change device to suit different formulations.

3. Main motor power P

The power of the main motor has a direct relationship with the granulation output and the inner diameter of the ring die. When designing the granulator, you must first know the granulation output (according to the national formula and the 5mm hole in the middle, and then the power consumption per t of the granulation is integrated Index, you can roughly calculate the main motor power P. Generally, the electricity consumption per ton of material is 10KW.h/t according to the standard of the poor family, then the calculation formula of the main motor power is:

P = output (t) x power consumption / t material = Q.K. (KW)

If a 5 t/h pellet machine is designed, the main motor power P=Q.K=

Sx10=50(KW)

Take standard motor power: 55KW

4. Unit power area

The unit power area refers to the effective die belt area (mm2) of the ring die corresponding to each KW of the pelletizing main motor. It is an import ant parameter to measure the performance of the pelletizer and is also the main basis for designing the pelletizer. This parameter is too large, the main motor power is too small, it will cause overload, otherwise it will waste energy consumption, therefore, the unit power area (mm2/KW) must have an optimal value. Looking at domestic and foreign manufacturers, the unit power area ranges from 2000 to 4000mm2/KW, and 2500mm2/KW is used in the design, so that the pelletizing performance is more stable and the reliability is good.

Calculation formula of unit power area A:

A=S/P=πD·b/p(mm2/KW)

S is the effective area of ??the ring moulding belt (mm2)

D is the inner diameter of the ring die (mm)

b is the ring molding bandwidth (mm)

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5. Ring mold inner diameter D and compression bandwidth b

Derived from the theory of unit power area, the inner diameter D of the ring die should be within an optimal range, calculated from the unit power area A:

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The inner diameter of the ring die on the actual pellet machine is 350mm, which is in accordance with the calculation.

b=0.25D=85.8(mm)

6. Diameter of pressure roller d

The diameter of the pressing roller directly affects the material intake angle during pressing. Therefore, under the best possible conditions, a large-diameter pressing roller (see Figure 2 for details), a ring die granulator with two pressing rollers, the pressing roller diameter d and the ring The relationship of the mold inner diameter D is: 2d<d so d<0.5d<="" p="">

Considering that there are bolts and adjustment gaps between the two pressure rollers, the relationship between d and D is generally:

d=(0.4～0.485)D

As mentioned above, the inner diameter of the ring die D=350mm, and the inner diameter of the pressure roller d=(0.4～0.485)D=170mm

7. Simple diameter of quenching and tempering and rotating speed of quenching and tempering shaft

The steam conditioning process before the material enters the granulation chamber will mature and sterilize the material to make the granulation quality better. The quality of the material quenching and tempering is related to the diameter of the quenching and tempering shaft and the rotational speed of the quenching and tempering shaft.

To design a reasonable diameter of the quenching and tempering shaft and the rotational speed of the quenching and tempering shaft, it is necessary to consider from the tempering time t. In addition to adding steam to meet the requirements, the length of conditioning time is very import ant. The conditioning time of the traditional pellet machine is 9~20s, and now the new theory proposes 20~60s. Especially when processing aquatic feed, the conditioning time is longer.

7.1 Simple diameter of quenching and tempering D

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In the formula: v-Quenifying and tempering simple volume (m3)

D-Quenient Diameter (m)

I-Temperature barrel length (m), take I=6D

v-feed bulk density (t/m3), take v=0.55 t/m3

k-feed full coefficient, take k=0.3

Q-Quenching and tempering shaft conveying capacity (t/h), the designed output of the pellet is 1.5～2.0 times of q, which can be initially determined as Q=1.8q

Substitute the above relevant parameters into the formula for the conditioning time t:

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In addition, according to the author's years of experience and the integration of domestic and foreign prototype parameters, the tempered simple diameter D is approximately equal to the ring die. Is it suitable for everyone to discuss? If this argument is feasible, many unnecessary calculations can be reduced.

7.2 Rotating speed of quenching and tempering shaft

The quenching and tempering shaft is mainly composed of a shaft copper tube and blades. There are many types of blades, all of which are to enhance the mixing effect of feed and steam. The rotation speed of the conditioning shaft has a great influence on the mixing effect. The speed is too high, the material maturation time is short, and the feed quality is not ideal before it is completely gelatinized. Conversely, if the conditioning time is too long, too much vitamin is lost , Poor fluidity, high water content, affecting the pelletizing performance and cooling effect. The speed of the quenching and tempering shaft is affected by many factors, and it cannot be directly deduced and calculated by the formula, generally taking the range of 100 ~ 300r/min. Some pellet machine conditioning cylinders are equipped with an inter-frequency device, which makes the speed of the conditioning shaft variable, and changes the rotating belt of the conditioning shaft according to the different conditioning time required for different feeds, so that the effect of feed ripening reaches the best state. In addition, the pellet machine for producing aquatic materials is equipped with 2 or 3 conditioning cylinders, the purpose is also to extend the conditioning time, so that the materials are fully cooked, suitable for the special requirements of aquaculture.

8. Feeding screw conveyor

The feeding screw conveyor installed at the top of the granulator is used to adjust the material conveying amount according to the size of the pelletizing output, so the conveyor is designed to be variable speed. There are two ways: drive with an electromagnetic speed controller with a reducer or reducer motor controlled by a frequency converter. The former is less technically difficult and has a lower cost, and manufacturers use more; while the latter has a compact structure and high cost, so it is rarely used at present.

Some of the blades of the spiral shaft adopt a full blade variable pitch structure, and some adopt a single blade installation structure. The former is impulsive when feeding, which has a certain effect on pellet pressure, but the residual amount is small; while the latter is just the opposite, and its shaft speed is higher than the former. At present, most pellet machines use a full-helical blade variable-pitch spiral shaft structure. Welding 4 single-blade dials at the shaft outlet can reduce the pulse of the material. The conveying amount is exactly the spiral shaft of this structure. The biggest advantage (see Figure 3). Calculation of the conveying quantity Q of the full spiral blade conveyor:

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In the formula: S-pitch (m)

D-spiral diameter (m)

n-spiral shaft speed (r/min)

v-feed bulk density, v=0.55t/m3

k-full coefficient, generally take k=0.8～0.95

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9. Summary

The main technical parameters of the pellet machine are discussed above, and there are many factors that affect these parameters. Just like some assumed parameters in the article, so you need to refer to the relevant prototype when designing, and design with a specific process level, without violating the main Under the premise of technical parameters, make it more perfect and more distinctive.

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