Centrifuges for drilling generally include high-speed centrifuges and medium-speed centrifuges. 1000-2000r/min is a medium-speed centrifuge, and higher than 2000r/min is a high-speed centrifuge.
The choice of centrifuge is affected by the particle size of the solid phase particles to be separated, the diameter of the centrifuge drum, the highest speed, and the separation factor. The sedimentation centrifuge commonly used on the drilling site is the difference in the density of solid and liquid as the separation basis, mainly used to remove the solid phase material in the drilling fluid of 2-10μm, and is the last level of drilling fluid solid control equipment.
In response to this problem, we should first trek the decanter centrifuge drum speed, of course, within the safety tolerance range, and the material is non-corrosive or less corrosive. Then trudge the filtration area inside the centrifuge drum. The method is to increase the lining mesh, so that there is a small gap between the filter bag and the centrifuge drum, and the trekking permeability; Increase the section area, such as adding V-shaped filter baffles.
In the process of using the decanter centrifuge, the problem of slow dewatering power of the decanter centrifuge is encountered, which is manifested as the increase of solid image material in the drum, the extension of dewatering time of the decanter centrifuge, and the appearance of non-drying. This phenomenon belongs to the general phenomenon.
It can be a few times dehydration methods, reducing the amount of centrifuge dehydration filter material per time, more, less discharging method. If the material is sticky, wash it within the limits allowed by the process. Trudging solid phase material particle size, in the case of unchanged process, if you want to trek fear rate, you can consider increasing, such as adding flocculant.
Decanter centrifuge is one of the widely adaptable solid-liquid separation equipment on the market, mainly used for solid-liquid separation. When selecting the equipment, it depends on the specific condition of the material, the separation or not of the decanter centrifuge and the separation function are determined by the dryness of the solid particles in the suspension, such as salt and sugar and other water-soluble items, which need to be separated after using flocculant.
Kosun_decanter centrifuge is mainly composed of a drum, screw, differential system, liquid level baffle, drive system, and control system. It is a special equipment for solid-liquid separation designed according to the characteristics of petroleum drilling fluid, which can complete various processes such as feeding, centrifugal sedimentation, and unloading at full speed. It is mainly used for recovering barite, removing fine solids, reducing the solid content of drilling fluid, controlling the density and viscosity of drilling fluid, ensuring the performance of drilling fluid, and playing an important role in rapid drilling. The LW series centrifuge separates the drilling suspension by the principle of centrifugal sedimentation. The suspension enters the rotary drum from the feed pipe through the liquid outlet hole in the screw pusher. Under the action of centrifugal force, the solid particles are pushed to the inner wall of the rotary drum and discharged through the slag discharge port at the small end of the rotary drum through the blade on the screw pusher. This is repeated to achieve the purpose of continuous separation. Sedimentation centrifuge belongs to the category of horizontal spiral centrifuge, full name horizontal spiral sedimentation centrifuge. Factors affecting the use effect of decanter centrifuge
The use effect of decanter centrifuge, the impact of its mechanical part is divided into adjustable factors and non-adjustable factors, now respectively explained, first understand its principle of action, you can effectively control it in use
1, non-adjustable mechanical factors are drum diameter and effective length. Half cone Angle of the drum. Pitch. The following categories are described: drum diameter and effective length: The larger the drum diameter and the longer the effective length, the larger the effective settling area and the greater the processing capacity. Half cone Angle: When the sediment settling inside of the centrifuge drum is pushed to the discharge port along the end of the drum cone, it is subjected to the downward sliding reflux force due to the action of centrifugal force. Drum half cone Angle: a more important parameter in centrifuge design. In terms of clarifying effect, the cone Angle should be as large as possible. In terms of slag delivery and dehydration effect, the cone Angle is required to be as small as possible. Pitch: that is, the distance between two adjacent spiral blades, is a very important structural parameter, which directly affects the success or failure of slag transport. When the spiral diameter is fixed, the larger the pitch and the larger the spiral lift Angle, the greater the chance of the material being blocked between the spiral blades. At the same time, the large pitch will reduce the number of turns of the spiral blade, resulting in uneven material distribution at the end of the drum cone, resulting in increased vibration of the machine. Therefore, for difficult-to-separate materials such as activated sludge, slag delivery is more difficult, and the pitch should be smaller. Spiral type: According to the liquid and solid relative movement in the drum is divided into countercurrent and forward flow. The feeding chamber of the countercurrent centrifuge is in the middle of the spiral, that is, near the boundary between the dry zone and the settling zone, to ensure that the liquid phase has enough settling distance, but the solid phase can only stay for the time required to pass through the cone, so a higher centrifugal force is required; The material entering the drum from here will cause the settled solid particles in this area to float again due to disturbance, and will also produce turbulence and additional eddy currents, which will reduce the separation effect. 2, adjustable mechanical factors are drum speed, difference speed (difference ratio), liquid ring layer thickness, and process factors, the following categories are described: drum speed: drum speed adjustment is usually achieved by variable frequency motor or hydraulic motor. The higher the rotational speed, the greater the centrifugal force, which is helpful to improve the solid content of mud cake. However, excessive rotation speed will destroy the sludge flocculation, but reduce the dehydration effect. At the same time, the higher speed has high requirements for materials, the wear of the machine increases, and the power consumption, vibration, and level will also increase accordingly. Difference velocity (difference ratio), the difference velocity directly affects the slag discharge capacity, mud biscuit degree, and filtrate quality to improve the difference velocity, which is conducive to improving the slag discharge capacity, but the sludge dehydration time will be shortened, the water content of the mud cake after dehydration is large, and too large difference velocity will increase the disturbance of the spiral to the liquid pool in the clarified area, and the filtrate quality is relatively poor (commonly known as “back mixing”). Liquid ring layer thickness: liquid ring layer thickness is an important parameter for equipment optimization, which directly affects the effective sedimentation volume of the centrifuge and the length of the dry zone (bank zone), and then affects the treatment effect of sludge dehydration. Generally, it is achieved by manually adjusting the level of the liquid level baffle in the shutdown state, and the adjustment must ensure that the level of each level baffle is the same, otherwise, it will cause severe vibration when the centrifuge is running. The increase in the thickness of the liquid ring layer will increase the settling area, the residence time of the material in the machine will also increase correspondingly, and the quality of the filtrate will be improved, but the length of the dry zone (bank zone) at the same time will be shortened, resulting in the reduction of the mud biscuit degree. On the contrary, lower liquid ring layer thickness can obtain higher solid content of mud cake, but at the cost of filtrate quality. Process factors: To improve the sludge dewatering performance, an appropriate amount of organic polymer flocculant, such as polyacrylamide (PAM), should be uniformly added before mechanical dewatering to reduce the specific resistance of the sludge, so that the sludge solid phase and liquid phase separation is easier to dehydrate, and the type of flocculant must be adapted to the characteristics of the sludge and the type of equipment and operating conditions. In many cases, the agent with better performance in the flocculant selection beaker test does not have better performance in practical applications, and the important reason is that although the agent characteristics meet the sludge characteristics to a certain extent, it cannot fully meet the operating conditions of the equipment.
Many factors affect the dewatering effect of decanter centrifuge, and all factors affect each other, so the treatment effect is the result of the comprehensive action of the above factors, the selection of centrifuge should be combined with the actual situation of the project, the adjustment of operating parameters should be considered from the expected mud cake moisture content, solid rate and economic factors required by the disposal method of the mud cake after dehydration
