Keywords SS type centrifuge exhaust
1. Overview The application of centrifuges in pharmaceutical and chemical companies is relatively extensive. There are many types of centrifuges. According to its working principle, it can be divided into filtration type, sedimentation type, separation type, table top, biological freezing, side filter type and the like. In the equipment of the pharmaceutical industry, the centrifuge zui is extensive.
Filter centrifuges can be divided into three categories: intermittent discharge type, piston push type, continuous discharge type. The application of Zui in the actual production of the enterprise is a three-legged type, which is a kind of intermittent centrifuge. The three-legged centrifuge has three typical models: SS, SX and XZ. In this paper, the SS type three-legged upper discharge centrifuge is taken as an example to introduce several exhaust methods commonly used in centrifuge exhaust.
2. Design principle of exhaust type of SS type centrifuge The three-legged centrifuge adopts manual intermittent operation mode, which has the advantages of simple structure, stable operation, convenient operation, sturdy and durable, good washing separation effect, and difficult to break solid particles. Separation of suspensions containing solid phase particles ≥0. 01 mm, such as granular, crystalline, fibrous materials. The SS type three-legged centrifuge is a centrifuge for manual upper discharge.
The main discharge of the harmful substances in the SS type centrifuge is its discharge port. The drum of the centrifuge is driven by the motor to perform the centrifugal movement of high-speed rotation. The large amount of exhaust gas generated during the operation is discharged in a centrifugal manner under the strong centrifugal force generated by the high-speed rotation of the drum, and the diffusion speed is large. It is difficult for the conventional exhaust method to completely capture the exhaust gas and discharge it. The exhaust of the centrifuge has become a difficult problem for pharmaceutical and chemical companies to improve their working environment.
The SS type centrifuge exhaust method follows the following design principles:
(1) In order to ensure the effective control and exhaust effect of harmful substances, the exhaust hood should be as close as possible to the discharge opening of the centrifuge, so as not to hinder the production and operation;
(2) The amount of exhaust air should be as small as possible;
(3) Indoors, especially in the exhaust hood of the clean room, the determination of the amount of exhaust air should take into account the amount of air supply. If the exhaust air volume is too large, it will cause negative pressure inside the room and affect the cleanliness;
(4) When there are multiple centrifuges in production, a butterfly valve and other regulating valves shall be arranged on the exhaust hood of each centrifuge;
(5) When multiple centrifuges are used at different times, the appropriate simultaneous use factor should be considered.
3, SS type centrifuge exhaust mode selection According to the work and structural characteristics of the SS type centrifuge, the current exhaust air for the SS type centrifuge mainly has the following four ways:
3. 1 upper row
The SS centrifuge is manually unloaded from the top. The discharge port above the drum is open, and a large amount of exhaust gas is discharged from the discharge port during operation. The upper row mainly uses a circular umbrella cover. The size of the lower edge of the cover can be slightly larger than the discharge opening by 100-200mm, and the height of the cover skirt should be controlled below 150mm. The height of the umbrella cover can be determined according to the opening angle of the cover opening and the space on the spot. The diameter of the exhaust duct can be calculated according to the amount of exhaust air. Taking the SS-1000 as an example, the diameter of the exhaust duct is generally determined to be <250.
The upper row is simpler and the effect is worse. In order to be as close as possible to the discharge opening of the centrifuge, the effect of the exhaust is enhanced. Some designers design the umbrella cover to be rotatable, turn it off when discharging, and turn back when running, and the effect is improved.
The literature (1) gives the formula for determining the circular umbrella cover (D = d0 + 0. 4h) It should be noted that due to the operating characteristics of the centrifuge, this formula is not fully applicable to the exhaust of the centrifuge.
3. 2 The side-discharge centrifuge discharges the centrifugal movement of the high-speed rotation. Therefore, it is close to the discharge port of the centrifuge, and a semi-annular side suction cover (180°) is arranged along the circular arc of the discharge opening. The characteristics of the machine exhaust. The diameter of the inner circle of the semi-annular side suction hood is the same as the diameter of the discharge opening, the outer diameter is slightly smaller than the diameter of the centrifuge, the height is 300 mm or the space is fixed, and the exhaust pipe is arranged on the side wall of the exhaust hood, as shown in FIG. Show.
The semi-annular side suction hood takes into account the characteristics of the centrifugal exhaust, and the effect is better than that of the upper row. The disadvantage is that the side suction hood is semi-annular, and the exhaust of the centrifuge close to the operator can only be raised by the side. The suction speed of the suction hood is controlled, and the increase in the suction speed is limited.
3. 3 Closed type The closed discharge port of the SS type centrifuge is enclosed by a closed cover, so that harmful substances such as exhaust gas are placed in the cover, which is a good way to control the exhaust of the centrifuge. Small, the effect is better. In order not to hinder the operation, at the side of the sealing surface corresponding to the operating surface of the centrifuge, an active discharge port is opened, the discharge opening is opened when used, and is closed when not in use, and the size of the discharge opening depends on the discharge mode and the size of the discharge barrel. And so on. The airtight exhaust duct can be placed on the opposite side. The structure of the closed cover is shown in Figure 2.
Practice has proved that the air venting effect of the airtight cover is good and does not affect the operation.
3. 4 self-discharge type The self-discharge type refers to the centrifuge itself with a fully enclosed cover. When the centrifuge is running, the cover is closed, and the exhaust gas accumulates to a certain extent and is automatically discharged through the liquid outlet. At present, there are many pharmaceutical factories in China that produce this type of centrifuge. Most of the centrifuges are equipped with a quick-loading hanging bag structure, which not only is convenient to operate, fast and labor-saving, but also avoids cross-contamination of separated materials and greatly improves the operating environment. In the case of high requirements for the production environment, especially in clean rooms, this type of centrifuge should be preferred.
4. Conclusions (1) The exhaust of the centrifuge is a difficult point, and the designer needs to combine the advantages and disadvantages of the above-mentioned several exhaust methods according to the production situation, and carefully compare and adopt.
(2) The air volume of the centrifuge is based on the principle of “small air volume and good air exhausting effectâ€. The air volume of the centrifuge in the clean room should consider the positive and negative pressure requirements.
(3) The exhaust valve of multiple centrifuges should be equipped with a regulating valve and consider the simultaneous use factor.
(4) It is recommended to use a fully closed bag centrifuge. A closed cover is recommended when the hood must be installed.
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