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Guangzhou Longyue Environmental Protection Machinery Equipment

Co., Ltd.

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Phone: 020-86861928

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Concentrated belt filter press (hereinafter referred to as belt filter press) is a high-efficiency solid-liquid separation device based on the principle of chemical flocculation contact filtration and mechanical extrusion, because it has a simple process flow, high degree of automation, continuous operation, A series of advantages such as easy operation control and adjustable work process are achievable, and sludge thickening tanks are saved, which saves construction funds to a certain extent and are being used more and more widely. The flocculated sludge enters the gravity dewatering zone first, and most of the free water is filtered through the filter belt under the action of gravity; with the operation of the filter belt, the sludge enters into a wedge-shaped zone consisting of two filter belts, and two filter belts Slowly pressurize the sludge, gradually thicken the sludge, reduce the flowability, and transfer to the press area; in the press area, the sludge is subjected to increasing pressure and the shear force generated by alternately changing the upper and lower positions of the two filter belts. As a result, most of the free water and interstitial water remaining in the sludge are filtered out, and the sludge becomes a flake-shaped filter cake with a lower moisture content; the upper and lower filter belts are separated by a discharge roller, and are utilized by virtue of changes in the curvature of the filter belt. The scraper scrapes the filter cake to achieve the solid-liquid separation of the material, and the upper and lower filter belts are washed and reused for the next cycle of concentrated pressure filtration.

The main technical and economic indicators involved in the practical engineering application of belt filter press are: 1 processing capacity, 2 mud cake moisture content, 3 chemical dosage, 4 power consumption, 5 flush water consumption, 6 belt tension, 7 The main indicators such as effective bandwidth, 8 filter belt operating speed, 9 air supply pressure, etc. Among them, the processing capacity is the first indicator to evaluate the overall performance of the belt filter press. There are many factors affecting the processing capacity of belt filter presses, but they are mainly manifested in the gravity dewatering zone, the press zone and its filter belt operating speed, filter belt tension, roller diameter (size, wrap angle and center distance), and filter belt (air permeability ) Selection, drug conditioning effects, etc., is also a comprehensive expression of the quality of belt filter presses such as structural design and manufacturing. Therefore, understanding the calculation method of the belt filter press processing capacity has certain guiding significance for the optimization design of the belt filter press, the selection of operating parameters, the reasonable dosage of the dosage.

Calculation of the processing capacity of the belt filter press 2.1 The first calculation method for the processing capacity of the belt filter press The main calculation parameters for the wet cake thickness produced by the belt filter press are based on the calculated wet cake output. Calculate the amount of feed (ie, processing capacity), the formula is as follows: Q wet mud cake = B · ξ · δ · v · s · γ · β type: Q wet mud cake - wet cake output t /hB - width of the filter belt m - filter belt width utilization factor, generally take 0.85 ~ 0.9δ - wet cake thickness m, generally take 6 ~ 10mm (0.006 ~ 0.01m) v - pressure filter belt with the actual work Speed m/min, generally take 3 ~ 6m/mins - unit time 60min/h γ - wet mud cake weight t/m3, generally take 1.03 t/m3β - solid phase recovery rate, generally take ≥ 95% Q feed Volume = (solid content of wet cake / solid content of feed) × Q wet cake (t / h) From the above formula can be seen, the calculation method is to produce wet cake thickness with a belt filter press The main calculation parameters, while the formation of wet cake thickness on the one hand and the belt filter press operating parameters such as filter speed, filtration pressure has a great relationship; the other is also with the sludge properties such as solids concentration The viscosity and the specific resistance of the sludge after conditioning are also of great importance; the formation of wet cake thickness depends on the design of the filter press, such as the length of the enrichment section, the capacity of the enrichment section, the filter press time and pressure. Filter cycle, the choice of filter air permeability. In the calculation formula, the wet cake thickness of wet cake is linear with the wet cake thickness δ. The thickness range of wet cake thickness is selected from 3 to 10mm, and the thickness of the wet cake formed during the actual operation of many belt filter presses is within the width of the filter belt. Also uneven. Therefore, the author believes that this kind of calculation method is not combined with the main technical parameters of the concentrating section and the press section and the main property parameters of the sludge, and does not reflect the adjustment effect of sludge dosing, the design of filter press structure parameters, and the change of operating parameters. The influence of other factors on the processing capacity of the belt filter press, and the calculated Q wet cake value range is larger, generally applicable to the design selection of the belt filter press, the optimized structural design of the belt filter press, There is little point in guiding the operation. 2.2 Another calculation method of belt filter press processing capacity: The sludge dewatering system of municipal sewage and industrial waste water requires the sludge to be conditioned before sludge dewatering. The purpose of adding medicine conditioning is to improve the dewatering performance of the sludge, reduce the water affinity in the sludge, reduce the specific filtration resistance (ie, the resistance of the filter cake) and the capillary water absorption time (CST) of the sludge. When the filtration starts, the filtrate must overcome the resistance of the filter medium (filter belt). When the filter cake is gradually formed, it must also overcome the resistance of the filter cake itself, which is the basic form of filter cake filtration. The calculation of the filtration yield (ie, processing power) can be performed using the Carman filter basic equation derived from the basic principle that the liquid flows through the filter residue layer. According to Karman filtration basic equation: (1) Type: V - filtrate volume m3t - filtration time sP - filtration pressure PaA - filtration area m2μ - the dynamic viscosity of the filtrate Pa · s ω - filtration unit volume of filtrate The weight of dry solid retained on the filter media kg/m3r-specific resistance m/kg, ie the resistance of the filter cake, is defined as the resistance Rf per unit of dry weight filter cake per unit area - the impedance of the filter medium 1/m2 The following formula can be written from the definition of ω: (2) In the formula: Q0——into the sludge volume (processing capacity) m3Qf——filtrate volume m3Ck——solid concentration of the filter cake in kg/m3 according to the liquid phase equilibrium relationship: Q0 = Qf + Qk based on the solid-phase equilibrium relationship: Q0C0 = QfCf + QkCk obtained: (3) where: C0 - solids concentration in the raw sludge, g/LCf - concentration of solids in the filtrate, g/L, sludge Dehydration system generally requires a solids recovery rate ≥ 95%, Cf value is very small, the actual calculation is desirable Cf = 0Qk - filter cake volume L according to the definition of filtration yield: filter unit weight per unit of time produced on the filter area weight kg / (m2·s) or kg/(m2·h). For calculation convenience, tentatively set the impedance of the filter medium Rf = 0, then the Karmen filter basic equation (1) becomes: (4) set the filter biscuit weight to W, then W = ωV, V = W / ω substitution (4 ) Finished:

That is, the processing capacity of the belt filter press L (based on the dry sludge amount, that is, filter biscuit weight) is: (kg/m2.s) (5) (5) is the processing capacity of the belt filter press Another calculation formula. For the sludge dewatering system of municipal wastewater treatment plants, the sludge specific resistance, r, is controlled at (1～4)×1012m/kg after the sludge is conditioned by medicines (the laboratory determines the economical dosing amount by determining the r value). Among them, for the belt filter press, the specific resistance r of the sludge after conditioning by adding the drug in the laboratory is (1~3)×1012 m/kg (centrifugal dehydration r=(2~4)×1012 m/kg). . When the ambient temperature is 20°C, the kinematic viscosity of the sludge is μ=0.001 Pa·s. When using the formula (5), the belt filter press integrated machine should be divided into two parts: the concentration section and the press section. The concentration section is dewatered by gravity filtration. The filtration pressure P is calculated as the sludge height (average thickness, 1 mm=9.5 Pa) in the sludge section of the concentration section. The concentration C0 is the infiltration concentration, and the Ck is the concentration of the concentration of sludge in the enrichment section. It is 8 to 10% (concentration when the sludge loses its fluidity after gravity dewatering through the concentration section). The filtration time t is determined by the length of the concentration section and the travel speed of the filter belt. For the press section, the pressure P is calculated by the filter belt tension, the contact area between the press roll and the filter belt, the concentration C0 entering the press section is the concentration of the concentrated sludge (8 to 10%), and Ck is the final filter cake concentration (25%). ~ 20%), filter press time t = m/T, m = ts/T (ie t = ts/T2), ts is the actual filter press time (contact length between the filter belt and press roll in the press section, filter belt run in the press section Speed obtained), T is the filter press cycle (press section running time). The sum of the amount of treatment of the concentration section and the press section is the throughput of the belt filter press. Since the impedance Rf of the filter medium of the filter medium is not taken into account in the calculation, the resistance Rf of the filter belt is related to the material of the filter belt and the ventilation volume [generally selected from 8000 to 10000 m3/(h·m2)], so the final amount of treatment should be It is the processing amount of the belt filter press that multiplies the processing amount calculated above by a coefficient K (K is generally 0.9 to 0.95). 3. Conclusions Although the second calculation method is more complex than the first calculation method, the calculation method includes the influence of the design parameters of the belt filter press, the sludge property parameters, the operating parameters, etc. The structural design of the belt filter press, the reasonable dosage of the dose, and the choice of operating parameters have certain guiding significance for improving the throughput of the belt filter press. And calculated by examples, the treatment capacity of the concentrated section plays a major role in the processing capacity of the belt filter press.

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