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Yunusova Zamira, doctor of technical sciences, associate professor Rakhimov Farkhad, Tashkent Institute of Textile and Light Industry Dodaev Kuchkar Odilovich, рrofessor, Tashkent Institute of Chemical Technology* E-mail: daminov.asror86@gmail.com
KNITTED FILTERS AND THEIR APPLICATION IN INDUSTRY
Abstract. This article presents the results of research on knitted filled filters, their application in the food industry, in particular when filtering juices.
Keywords: filtration, textile fabrics, cleaning, sleeve, filler, filled knitted filter, composites.
a solid tubular shape in both ways makes it promising to create filtering composite solid sleeves based on knitted fabric with a filler of the above-mentioned bulk fibrous materials.
Based on the above, a new approach to the formation of filters has been developed, using the capabilities of knitting equipment, including a method for producing filled knitwear from various types of raw materials, both for the base and for the filler, taking into account their thermal resistance, chemical resistance to acid and alkaline media, oxidizing agents, solvents, etc.
Technological regulations for the production of the proposed product have been developed, it is implemented in the production condition of PE "Gam Rakhimov Ishonch" and a pilot batch of highly efficient filter cloths with imitating fibrous materials like cotton and polyacrylonitrile yarn has been obtained. The technological parameters, physicomechanical and operational properties of experimental samples (Tables 1 and 2) were investigated.
Introduction. Advances in the development of new filter materials with specific properties associated with the emergence of new fibers and new ways of modifying existing canvases, as well as a new approach to their formation. The properties of various materials are most successfully realized in their compositions, when the shortcomings of one material are covered by the merits of another or new properties appear that are not inherent in individual components.
Non-traditional fibers (sorption, antimicrobial, basalt, etc.), in particular, chemisorption fibers have low mechanical properties, which makes it difficult to form yarn from them for the manufacture of textile material. All attempts to improve the mechanical properties of nonwoven fabrics formed from them are accompanied by a deterioration in the sorption properties. Fabrics have significant hydraulic resistance when filtering. The lack of physical and mechanical properties of nonwovens, and the increased complexity of the formation of
Table 1. - Refueling and technological parameters filter cloths
Linear density (number) of raw materials, basis filler Density on 100 mm hinges A, mm B, mm The length of the thread in the loop, L, mm Q, g/m2
Wg Rv
Cotton yarn 17.5 (№ 34) tx 1 x 2 54 88-44 0.92 0.6-1.1 4.5 435
Cotton yarn 21 (№ 28) t x 1 x 2
PAN21 (№ 28) t x 2 48 76-38 1 0.7-1.3 5.1 534
Cotton yarn 21 (№ 28) t x 1 x 2
Table 2.- Physico-mechanical and operational properties of the filter cloths
Thickness, mm Breaking load, N Relation. elongation,% Abrasion resistance, cycle Breathability **, cm3/cm2 s
length width
1.35 345 292 9.4 12500 41
1.65 471 201 7.9 28000 101
Note: * force above 6 N; **P = 1 ATM
Taking into account the particular demand of the indus- wear from 100% cotton raw materials have been tested in the try for high-performance filters, new samples of filled knit- chemical and food industries.
- In the chemical industry.
The filtering properties of the filled knitted fabric by comparison with the data of the fabric were tested in laboratory conditions byJSC "Navoyiazot" when filtering liquid samples of the following theorem production flows (TM):
1. Solution of rhodium ammonium for purification from impurities after decomposition of ammonium polysulfide pos. P 301.
2. Suspensions of double salt (DS) after the washer of item 203 for the separation of the double salt from the solution of rhodium ammonium (RARA).
The filtering ability of the tested knitted fabric was compared under similar test conditions with the filtering capacity
Table 3.- Test results on fill
of cotton filter cloth (FST Uz 6.1-56-96) used in the production of theorem.
When filtering a solution of rhodium ammonium from insoluble sulfur-containing compounds, the amount of impurities trapped on the filter, the filtration rate and the optical density of the filtered solution were determined.
The test results on the filtration of the rhodium solution p. P 301 are given in (table 3.)
As can be seen from (table 3), the cleaning efficiency of the test knitted fabric from sulfur-containing impurities is lower than that of cotton filter cloth.
of the birthing solution
No. p/o Name of the indicator The norm under the rules № 63 The solution of rhodium ammonium p. P 301
Before filtering After filtering
Test stuffed jersey Severe fabric STP Uz 6. 156-96
1. Mass fraction of polysulfides in solution in terms of sulfur,% n/b 0.028 0.012 0.011 0.0069
2. Optical density, cu n/b 0.8 0.012 0.006 0.0045
3. Degree of cleaning,% - - 50.0 62.5
4. Filtration rate (0.5 dm3), s - 20 30
When testing samples during the filtration of double salt, the yield and composition of the double salt were evaluated. The ratio of TM: RA was determined in the double salt and mother liquor. By the same indicators, the initial suspension of p. 203 was also analyzed. In addition, the filtration rate of the suspension was determined through the test and compared samples.
Table 4.- Sample Test Results
Filter samples were pre-soaked in water. In the amount of 0.5 dm3 of the DS suspension, p. 203 was filtered on a Buchner funnel under a vacuum of 0.5 - 0.6 kg/cm2 through filter samples.
The filtered crystals were diluted to a salt concentration (35 - 37)% and the ratio TM: PA was determined. The test results are shown in (table 4).
Ex. Sample suspension DS (TM: RA) After filtering
No p/o Name of the indicator Through the test filled jersey Through the compared fabric SPT Uz 6.1-56-96
Double salt (TM: RA) Mother liquor Double salt (TM: RA) Mother liquor
1. The amount of salts (TM + PA) in suspension,% G 62.87 36.5 235.09 58.4 490.6 36.0 236.1 57.2 478.5
2. Ratio (TM: RA),% G 16.07: 46.8 20.1: 16.4 47.3: 38.5 11.75: 46.65 57.6: 228.9 21.3: 14.7 50.3: 34.7 10.2: 47.0 48.8: 224.9
3. Filtration rate (0.5 dm3) s - 75 - 96 -
As can be seen from the data on the output of double salt given in (Table 4), filtering samples (test and harsh cloth (STP Uz 6.1-5696)) showed approximately the same results.
The ratio of TM: in this salt was slightly better when filtered through the compared severe fabric.
Filtration rate through the test filled knit more than through harsh fabric.
On the basis of the conducted studies, it can be concluded that the filled knitwear is inferior to the harsh fabric currently used in the shop in terms of the filtering ability of the RA. solution from impurities (STP Uz 6.1-56-96).
Manufacturers found that for a more accurate assessment of the filtering ability of the subject filled with knitwear when filtering double salt requires experimental testing on a pilot plant.
- in the food industry.
On the filters, the juice is passed through a porous septum, sediment is retained. Cardboard, pressed asbestos, and bulk materials - fibrous asbestos, diatomaceous earth, ben-tonite clay, which are applied to the metal mesh or filter fabric (belting) are used as a partition. Consideration is being given to replacing the filter fabric with a fabric filled jersey filter.
The sediment contained in the juice, partially deposited on the surface, and partially penetrates into the pores of the filter septum. In this case, the filtering is intermediate between the slurry and clogging. The sediment first accumulates in the pores of the material used, then forms a layer of particles on the surface. Due to the growth of sediment filtering takes place at a variable pressure.
Fruit juices are filtered only at constant and low pressure - up to 68.6-78.4 kN/m2 (0.7-0.8 atm.). The sediment consisting of organic particles contained in the juice is easily compressed at an elevated pressure, which causes a filter blockage that prevents further process.
The studies were conducted on grape and Jerusalem artichoke juices, under the production conditions of LLC "Dal-varzintamirlash", "SAYOHAT AGRO MAHSULOT" in the Tashkent region LLC "Namangan Sharbati" in the Namangan region. The filtration rate increases significantly with decreasing precipitate amount. To speed up the process, the clarified juice is decanted from the precipitate and centrifuged, and then filtered.
The filtering process requires a pressure drop on both sides of the filter septum. With an increase in pressure, the porosity of the septum, as well as the speed of the process, first increase, and then due to slump compression and clogging of the filter pores. For grape juice, the highest filtration rate is achieved at a pressure drop of 68.6 KN/m2 (0.7 atm), apple juice - 78.4 KN/m2 (0.8 atm).
The precoat filter consists of vertical frames, covered on both sides with a thick metal mesh and located in a common
receptacle for unfiltered juice. A layer of fabric knitted fabric filters is applied to the mesh. The filtered juice is collected in the space between the grids and is discharged through a common channel. Before starting, the filter frames are removed and washed, as well as the internal cavity of the filter with hot water. Then the filter is collected.
Textile bag filter from the filled jersey is washed and sterilized for 30 minutes in water with a temperature of550 °C, after which the water is wrung out.
To charge the filter, juice is loaded into the pressure tank in such a way that it is possible to fill the filter and pipelines with a slight excess. The prepared filter material in the amount of 125-150 g/m2 of the filter septum is stirred in the juice in the pressure tank. The mixture is fed into an empty filter, after opening the purge valves to remove air, which resists filtering.
The filtered juice is allowed to be recycled until the filtrate becomes crystal clear. After that, the filtered juice is fed for bottling, and new portions of unfiltered juice are loaded into the pressure tank, but without adding any filtering material.
During operation, shocks and vibrations of the apparatus, as well as reduction of the juice level should not be allowed, in order to avoid breaking the continuous filtering layer and clouding the juice.
As sediment deposits, the filtration rate slows down, so the filter is periodically stopped, the precipitate is removed along with the filtering material, and the process starts over.
In the production of fruit juices, chamber and frame filter presses are used.
Chamber filter press consists of filter plates, equipped with two protruding hollow ribs. The edges are located on one side of the slab (top and bottom). The surface of the plates has grooves and communicates with the hollow space of the flanges.
When assembling the filter plate even numbers set flanges in one direction, and odd - in the opposite direction. In this case, the holes in the flanges of each row form channels. The upper and lower channels of odd numbers (1.3) are used to supply juice, even numbers (2.4) - to drain the filtrate. The movement of the juice can have the opposite direction - from even to odd numbers.
The material or plates sandwiched between the plates of the filter press serve simultaneously as a partition and filter material.
The juice supplied by the pump enters the channels formed by the flanges of one row, then goes to the plate grooves, passes through the filter septum and falls on the grooves of adjacent plates, from where it is drained through the flanges of the plates of the opposite side of the filter.
Frame filter press in contrast to the chamber consists of alternating plates and frames. Each frame with plates adj acent to it from two sides forms a chamber. The filter is placed between the plates and the frames.
A sample of the filled knitwear is placed between the plates of the filter press and tightly clamped with a screw. Then open the air purge valves on the filter press and pump the pre-clarified and decanted or centrifuged juice. When the filter is filled with juice, the air taps are closed. The first portions of juice may be cloudy. In this case, they are fed for recycling. Since the release of crystal clear juice, it goes on bottling.
Thus, the results of the research and the judgments of the manufacturers confirm that the filled one-piece bag filters can be formed only in the knitted way. With an increase or decrease in the proportion of filler in the process of knitting, it is easy to adjust the technological parameters, physic-mechanical and other operational properties of the filter used. By applying various specific raw materials, both base and filler, according to the production requirements,
you can create a series of import-substituting and export oriented filter materials.
In filter presses, porous knitted material (without filler) can be used to clean unclarified juice from large particles of fruit tissue. The porosity and deformability of the structure of the filled knitwear, in contrast to the fabric, positively accelerates the process of filtration and removal of sediments prior to re-use. Replaceable performance filters periodic action depends on the recharge mode. Since the filtering goes with a gradually decreasing speed, the more often the filtering layer changes, the higher the filtrate yield per unit time of useful work. However, with an increase in the number of recharges, which require a large expenditure of time on disassembling the filter, changing the filter layer and assembling the apparatus, the downtime is significantly longer.
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