Working principle of candle filter:
The candle filter is an automated pressure filter device with one or more filter elements in the cylinder. The filter element is covered with a special filter cloth selected according to the characteristics of the raw material liquid (some special raw material liquids need to add filter aids, such as activated carbon, diatomaceous earth, etc.)1. Its working process is divided into two stages: filtration and backwashing and slag removal:
Filtration stage: When the liquid is pumped into the filter, the liquid phase will pass through the filter medium (filter cake layer formed by filter cloth and possible pre-coated filter aids) into the center of the porous filter element, and then be collected and discharged at the clear liquid outlet. Before the filter cake layer is formed, the discharged “clear liquid” may return to the raw material slurry inlet and be sent to the filter for circulation filtration until the filter cake layer is formed and can meet the filtration requirements. At this time, the clear liquid is no longer circulated, but is sent to the next process through the three-way valve for use. As the filtration proceeds, solid matter continues to accumulate on the surface of the filter cloth. When these solid matter reaches a certain thickness, a “filter cake layer” is formed1. Back-blowing and slag removal stage: After a period of normal filtration, when the filter cake layer reaches a certain thickness, the rate at which the filtrate passes through the filter cake layer decreases, and the filtration efficiency becomes worse. At this time, the system will back-blowing and cake removal operations according to the signal provided by the pressure sensor. Back-blowing gas (such as compressed air, nitrogen or saturated steam) flows from the non-porous central tube to the porous tube, causing the filter cloth to swell and round, effectively vibrating and peeling off the filter cake, while removing the particles in the filter cloth fibers, improving the back-blowing efficiency, and quickly restoring the filter cloth’s filtration capacity. After that, open the valve at the bottom of the cylinder to discharge the slag, close the slag discharge port after the slag discharge is completed, return to the initial state before filtration, and prepare for the next round of filtration.
Advantages of candle filters:
Good filtration effect:
High-precision filtration: It can directly perform fine filtration, with a maximum precision of 0.2μm, and has a significant filtration effect on tiny particles, which can meet the production requirements for high filtrate purity.
Filter cake layer filtration: The gaps between the particles in the filter cake layer are very small, which can effectively prevent the escape of particulate impurities in the liquid, making the filtrate clear and achieving good filtration effect. And by pre-coating the filter aid to form a filter cake layer, the filtration accuracy and clarity can be further improved.
Wide range of applications: Suitable for a variety of special filtration occasions such as high impurity content, high precision requirements, high viscosity, high temperature, strong acid and alkali. Whether it is corrosive liquids in the chemical industry, viscous materials in the food industry, or high-temperature production processes, candle filters can operate stably.
Strong filter cake processing capacity:
Large filter cake recovery: With a large filtration area and excellent filter cake peeling performance, a large amount of high-value filter cake can be recovered from high-solid content liquids at one time, which improves the product recovery rate and production efficiency.
Filter cake can be washed and dried: The intercepted filter cake can be washed multiple times directly in the filter, and after adding the drying design, the filtration, washing, drying and unloading operations can be integrated, reducing investment, shortening the process flow, and saving energy consumption 3.
High degree of automation: The entire filtration process can be fully automated. Through computer control systems, pressure sensors and other equipment, it can automatically complete filtration, backwashing, slag discharge, cleaning and other operations, reducing the workload and errors of manual operations, and improving production efficiency and stability.
Energy saving and environmental protection:
The filter medium can be reused: The filter medium (such as filter cloth, filter aid, etc.) can be reused many times after proper treatment, which saves a lot of filter consumables and reduces production costs.
Low energy consumption: The main body is a static component, and the dynamic backwash design makes the equipment have low energy consumption and relatively low operating costs. In addition, during the filtration process, the liquid is transported and filtered in a closed environment, which reduces the volatilization and leakage of the liquid and reduces the pollution to the environment.
Easy maintenance: The equipment structure is relatively simple, mainly composed of a cylinder, a filter element, a filter cloth, a control system, etc., which is easy to disassemble and install. And the filter element has a long service life and low maintenance cost.
Good airtightness: The cylinder is firmly sealed, ensuring that there is no leakage in the production process. It is suitable for filtering highly corrosive, volatile or dangerous liquids, and improves the safety of production.
