Reference for design, selection and maintenance.
A continuous crystallization unit, the original design is to use two pneumatic switch ball valves for each crystallizer to control the production and recirculation of the internal materials. When the unit is operated in the automatic state, the two valves alternately switch according to the liquid level change in the mold. However, the process has two shortcomings: First, when a valve is closed for a long time, the low temperature material will crystallize in the pipe before the valve, causing partial blockage; second, when any crystallizer needs to be repaired due to failure, The entire unit must be parked, resulting in reduced equipment utilization. To this end, the author made a technical transformation, replaced the original two billiard valves with a three-way valve, and redesigned the control scheme, and achieved the expected results after the actual operation.
1. Introduction to the process
The process of continuous crystallization after transformation is shown in Figure 1. It can be seen from the figure that the material is first pumped into the crystallizer A from the raw material tank through the feed pump (transport pump) for cooling and cooling; the material after the temperature reduction is turned from the crystallizer A to the crystallizer B by the turning pump. Further cooling and cooling; and so on, the material is turned to the mold F to continue cooling and cooling; after the Zui crystallizer F contains crystal material, and then used to transfer the centrifugal pump to the centrifugal separation process for centrifugation, drying and packaging, Get qualified products.
Each crystallizer uses a three-way valve to control the liquid level: when the liquid level in the crystallizer is higher than the high set value, the material is automatically turned to the next stage crystallizer through the DCS control valve; when the liquid level in the crystallizer is lower than the lower level When the value is set, the valve is automatically recirculated through the DCS control loop. Each crystallizer controls the cooling water volume through a regulating valve to ensure the cooling temperature.
When any crystallizer needs to be repaired, the operator only needs to press the service button as shown in Figure 2 in the manual state, and the manual bypass valve on the site is opened, and the manual feed valve and the manual return valve are closed. . At this point, the material will pass through the valve directly from the upper mold to the next stage crystallizer, which will be listed from the system for maintenance.
2, pneumatic three-way ball valve composition and working principle
The pneumatic three-way ball valve is composed of a solenoid valve, a three-position pneumatic actuator and a three-way valve body. The principle and function of each part are described below. 2.1, solenoid valve structure principle
Whether it is a two-position or three-position pneumatic actuator, a solenoid valve is required to control the air circuit switching to realize the valve switching action.
After the single electric control coil is energized, the solenoid valve is reversed. After the power is lost, the solenoid valve is reset by the spring inside the valve. 8~12mm copper tube (plastic tube) connection or NAMUR connection can be used between the solenoid valve and the actuator cylinder.
Solenoid valves can be divided into two-position three-way and two-way five-way according to the internal structure. The solenoid valve in the two-way three-way mode includes an air inlet (connected to the intake air supply), an air outlet (provided to the cylinder air supply) and a vent (installation silencer), which is usually matched with a single-acting cylinder. Use, to achieve two-way control of the valve opening and closing; the solenoid valve in the two-way five-way working mode has an air inlet (connected to the intake air source), a positive action air outlet and a reverse action air outlet (respectively the cylinder Provides a positive and negative reaction air source), a positive-action venting port and a counter-acting venting hole (both are equipped with a muffler), which is usually used in conjunction with a double-acting cylinder to achieve two-position control of valve opening and closing. The voltage level of the solenoid valve coil is generally 24V (DC), 220V (AC), etc., and there are explosion-proof and non-explosion-proof points.
YT-S350
YT-S350
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