1、 Operating principle

Horizontal spiral centrifuge is a type of horizontal spiral discharge settling centrifuge, mainly used for solid-liquid separation of materials. It is pushed to the slag discharge port at the small end of the drum by the blades on the spiral feeder, and the liquid phase overflows through the overflow hole at the large end of the drum. In this continuous cycle, to achieve the goal of continuous separation.

After the hollow shaft is fed into the drum, it is immediately thrown into the drum cavity under the centrifugal force generated by high-speed rotation. The high-speed rotating drum generates strong centrifugal force to throw solid particles with higher density than the liquid phase onto the inner wall of the drum, forming a solid layer (known as the solid ring layer due to its annular shape); Due to its low density and centrifugal force, water can only form a liquid layer on the inner side of the solid ring layer, known as the liquid ring layer. Due to the different rotational speeds of the screw and the drum, there is a relative motion (i.e. speed difference) between the two. The relative motion of the screw and drum is used to slowly push the sludge in the fixed ring layer to the cone end of the drum, and after passing through the drying zone, it is continuously discharged from the outlet distributed around the drum circumference; The liquid in the liquid ring layer is continuously "overflowed" by gravity from the weir mouth to the outside of the drum, forming a separated liquid.

2、 Application in biogas engineering

The horizontal spiral discharge settling centrifuge is mainly used in biogas engineering for the treatment of biogas slurry after anaerobic fermentation. It is commonly used for solid-liquid separation of low concentration biogas slurry or as a secondary solid-liquid separation of biogas slurry after primary solid-liquid separation.

The entire feeding and separation process is continuous, closed, and automatic.

3、 Equipment operation characteristics and experience

As a high-speed rotating centrifuge, its advantages are obvious:

1. It has a great adaptability to materials and can separate a wide range of solid particle sizes ranging from 0.005 to 2mm. It can also be separated as usual even when the solid particle size is uneven;

2. It can operate continuously and smoothly for 24 hours without interruption. It has advantages such as better performance, greater processing capacity, better separation effect, energy saving and drug saving, stability and reliability, and simple operation compared to ordinary centrifuges.

3. The centrifuge has excellent sealing performance, and solid-liquid separation operates in a fully sealed state, making the environment clean and clean.

4. Good operational stability, using a two-stage involute planetary gear differential, high transmission ratio, constant torque control, and reliable performance.

5. The entire machine is equipped with multiple protection devices such as torque protection, power control, vibration and temperature measurement, which are safe and reliable to use and can achieve DCS control.

6. The contact part with the material is made of high-quality stainless steel material with strong corrosion resistance. The entire machine adopts an overall frame structure, which is safe and convenient for lifting, and occupies a small area.

7. The back drive device can automatically adjust the differential speed according to changes in material concentration and flow rate, resulting in changes in screw torque, to ensure the constant dryness of the mud cake. According to the material situation, the back drive device can change the rotation direction to achieve forward and reverse functions, and discharge the material from the drum.

But common faults and solutions during operation:

Due to structural limitations, the stiffness of the centrifuge's drum and screw is not large, and they remain in a constant position for a long time. Due to their own weight, they bend and deform, causing vibration to be excited. For machines that are not used for a long time, they need to be cranked once every half a month.

Be sure to follow the prescribed startup and shutdown cleaning procedures.

Pay attention to the vibration and noise of the machine at all times, eliminate them in a timely manner, and do not work with diseases.

Common Fault 1: Machine Blockage

The first phenomenon is that slag is not discharged for a long time. Under other unchanged conditions, the discharged clear liquid gradually becomes turbid and dark, approaching the color and state of the feed. The drum current increases and the drum speed significantly decreases, while the slag discharge torque gradually increases and remains high. All indicate the possibility of internal blockage in the centrifuge.

Firstly, we should not press the emergency button. The centrifuge is running at high speed and there is no braking device, and the emergency button cannot provide any assistance at this time. The feed to the centrifuge should be immediately cut off. In most cases, the centrifuge can rely on the pushing action of the screw to eliminate blockages. If it is not possible to push and remove blockages by itself, the speed of the drum should be immediately reduced or the drum drive machine should be turned off, but the screw motor should not be turned off. After the centrifuge drum slows down, the blocked solid residue may gradually relax and be discharged by the screw outside the machine.

For centrifuges that have indeed experienced blockage, after the drum has completely stopped rotating, we should still inject water into the machine and do everything possible to restore the operation of the spiral. As long as the screw can rotate, the centrifuge will not be truly blocked and there is still a possibility of returning to normal.

Common Fault 2: Abnormal Machine Vibration

The abnormal vibration of a centrifuge is a destructive force that can cause serious damage to the machine. Machine vibration is divided into two types: chronic vibration and sudden vibration.

Chronic vibration mostly indicates wear and tear on the centrifuge, wear or detachment of external components, and gradual damage to the bearing system.

Sudden vibration often indicates internal material blockage, significant damage and detachment of internal components. In most cases, it is necessary to first check whether the slag discharge system has malfunctioned, causing solid slag accumulation to rise, and whether the clear liquid pipeline is blocked, causing liquid to spread back to the centrifuge drum body, etc.

Common Fault 3: Bearing Temperature Too High

When the bearing temperature is high, the first step is to check whether the amount of grease added to the bearing is too large, whether there is excessive vibration in the centrifuge, and whether there is abnormal noise during the bearing operation.

At the same time, we need to observe the color of the bearing waste grease. The normal color of the waste grease should be light gray. If the color of the bearing waste grease turns black, rusty yellow, or other abnormal colors, it indicates that the bearing may have been damaged and should be replaced in advance.

Regarding the issue of noise in the bearing area, not all noise indicates a problem with the machine. We pay special attention to distinguishing between a normal type of "oil layer stack ring" sharp noise. It is a grease lubricated friction component inside the bearing seat, and it emits a specific sharp sound during normal operation of the centrifuge. The characteristic is that the noise is intermittent. After performing the greasing action 1-2 times, the noise will temporarily disappear and then sound again later. This judgment relies on regular observation and continuous accumulation of experience.

Common Fault 4: Drum Manual Turning

The manual turning of the drum is one of the important methods for manually determining whether there is internal material accumulation and whether the drum can start smoothly when the centrifuge is stationary.

When we manually rotate a normal free drum, the rotation of the drum is very easy, and the drum can freely slow down until it stops, with a random stop angle position. If the rotation of the drum is very heavy, and after manually turning and releasing the hand, the drum will reverse and almost stay in the position before rotation. After repeatedly turning, each time the drum stays at an angle position, it indicates that there is solid slag accumulation inside the drum. At this time, if the drum is started to increase the speed, serious imbalance vibration will occur. When encountering this situation, please run the screw push while injecting water, empty the internal materials of the centrifuge, and then start it.