RU2006251C1 - Process for washing a single-layer bed pressure filter - Google Patents

Abstract

FIELD: washing of pressure filters. SUBSTANCE: process for washing a single-layer pressure filter comprises lowering the water level in the filter shell until the fluidized bed level is reached. Then the filter bed is air-loosened. The washing water and the air are supplied until the washing water level attains a drain device. Then the air supply is cut off and the washing water delivery is increased. EFFECT: increased efficiency of filter washing. 2 dwg

Description

 The invention relates to a washing technology of filtering granular materials in pressure lighting filters with a single layer loading and can be used in the power industry, chemical and other industries during the operation of water treatment plants.

 The purpose of the invention is improving the quality of washing, saving washing water.

 In FIG. 1, 2 shows a device and a graph that implements the proposed method.

 The method is implemented by the following sequence of operations: drainage of water in a disabled filter. The water level 9 (Fig. 1) above the charge 7 is left equal to the relative expansion of the fluidized bed, which is formed upon subsequent loosening of the charge with air.

The value of the relative expansion of the layer (l) for specific conditions is determined by the formula (L1 p. 11): l = (LL ₀ ) / L ₀ = (mm ₀ ) / (1-m ₀ ) [1] where L _o , m _o - the height and porosity of the filter layer in a stationary state, respectively;
L, m - height and porosity in a fluidized state;
L _o , m _o - depend on the shape of the grains, stacking, aspect ratio, degree of compaction of the layer, as well as the influence of the filter walls.

According to (L4) for the filter material - anthracite, we take m _o = 0.54.

The porosity in the fluidized state is considered according to the formula of O. M. Todes (L1, p. 12)
m = (18Re + 0.36Re ² ) ^0.21 xx Ar ^-0.21 , [2] where Re, Ar are the criteria for the similarity of Reynolds and Archimedes.

 The next step is loosening the air.

 When loosening, the useful properties of the fluidized bed (L2) are used, namely: intensive mixing of the solid phase; the impossibility of countercurrent phases within the "fluidized" layer; reduced hydraulic resistance of the layer.

 In practice, due to defects in the lower drainage system, uneven distribution of loosening air (“keys”) over the filter area is possible.

 With the proposed method of loosening, the intensity of the air flow can be increased, achieving uniform "boiling" over the entire filter area, without changing the degree of expansion of the layer limited by the "mirror" of water.

 After the specified loosening time, the washing stage begins with water supplied through the lower drainage under the loading layer, without stopping the air supply.

 Water-air washing according to the proposed method is equally suitable for any type of filter media: quartz, crushed anthracite, expanded clay, etc.

 The air flow rate for this operation remains unchanged, and the flow rate of flushing water is set equal to 15-25% of the maximum allowable.

 It was established (L3) that if the grains of the filter load are below the drain level 11 (Fig. 1) by 150-200 mm, then when washing with water alone, no removal is observed.

 For this, when the "mirror" reaches level 10 in the proposed method, the air supply is stopped. During the time that elapses from the moment the air supply is turned off to the overflow of water into the discharge device, the falling particles of the filter charge are separated from the sludge brought to the surface.

 The delamination time depends on the flow rate of the wash water, the type and composition of the load, the characteristics of the drainage system and is determined experimentally. At the same time, a highly concentrated suspension collected at the surface and prepared for ejection is lifted without draining water from the filter.

 At the final stage, when the “mirror” reaches level 11 of the drain, the sludge is removed from the filter by means of a volley supply of the maximum permissible flow rate of the wash water.

 PRI me R. The source water in the filter (Fig. 1) is fed through the valve 1, the water passes through the filter charge 7, the lower drainage 8, through the valve 2 and sent to the consumer.

 Upon accumulation of contaminants in the filter, the latter is switched on for regeneration.

 To do this, close the valves 1 and 2. Then make the descent of the water level in the filter. To do this, open the valves 4 and 5. The thickness of the layer of water left above the load is determined by the formulas [1] and [2] and for the filter shown in the example was 180 mm. The drainage time to this value was 19 minutes. After this time, the valve 5 is closed.

During the next operation - loosening the air, open the valve 6, connecting the lower drainage with the compressed air line. The air flow rate for loosening was selected experimentally and for this example was 400 m ³ / h, the loosening time was 5 minutes.

After loosening, the stage of water-air washing begins. The air flow rate remains equal to 400 m ³ / h and additionally, after the valve 3 is opened, rinsing water is supplied with a flow rate of 50 t / h.

 The time of air-water washing is selected equal to 7 minutes For the filter under test, at a flow rate of washing water of 50 t / h, the level of water column in the filter increased at a rate of 90 mm per minute.

 At a distance from the load to the discharge equal to 1000 mm, the “mirror” of water in 7 minutes of lifting will be below the discharge level by 190 mm. After 7 minutes, the air supply is stopped, the valve 6 closes and the rising “mirror” overcomes the remaining distance to the drain in 2 minutes, after which the water flow rate is increased to 200 t / h.

 Duration of washing 9 min. During this time, sludge has been removed from the filter. No removal of filter material was noted.

 In FIG. 2 shows graphs of the dependence of the amount of elongated contaminants over time for two washing modes. The results are based on chemical analyzes of suspended solids.

Curve I was obtained for the standard mode using air-water washing, when the air flow due to the removal of the filter load is limited to 65 m ³ / h.

 Curve II is obtained by washing the same filter by the proposed method.

 The graphs show that the number of contaminants removed from the filter (the area bounded by the curve) during flushing mode II is significantly higher. Due to the implementation of the proposed washing method, the filter cycle increases, the dirt capacity of the filter load.

 In addition, it was noted that the duration of a volley rinse is shorter than the duration of a conventional water rinsing operation.

 The resulting technical effect leads to a total saving of water for own needs. (56) Flushing the quick filters. Overview Information, N 7, 1981. Central Bureau of Scientific and Technical Information of the Ministry of Water Economy of the USSR, pp. 11, 12, 13.

 Halperin N.I., Kvasha V. B., Apshtein V. G. Fundamentals of the fluidization technique. M.: Chemistry, 1967.

 Meshchersky N. A. et al. Operation of water treatment in metallurgy. M.: Metallurgy, 1988.

 Gromoglasov A. A., Kopylov A. S., Pilshchikov A. P. Water treatment: Processes and devices. M.: Energoatomizdat, 1990, p. 51.

Claims (1)

 METHOD OF WASHING A HEAD-UP FILTER WITH A SINGLE-LAYER LOAD, including lowering the water level in the filter housing, loosening the air load, supplying the washing water from the bottom up and removing it by means of a discharge device, characterized in that, in order to improve the washing quality, the water level is lowered to a level the fluidized bed, after loosening, water-air washing is carried out by supplying a flow of washing water and air under the loading layer, the air supply is stopped until the level of washing water reaches the outlet present device and on reaching the level of the wash water discharging washing water supplying device is increased.

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