RU2057725C1 - Method for complex processing of technogen precipitates - Google Patents

Abstract

FIELD: complex processing of precipitates. SUBSTANCE: method involves separation of precipitates into three fractions, the process is followed by separate treatment of each phase. Initially sand component of precipitate is separated, then mud component is separated into phases, and each of it being treated separately. Precipitate is treated with sulfuric acid to prepare coagulant. Said precipitate is processed into sorbent with the help of pyrolysis and activation of precipitate. If said precipitate has high content of organic material then biological decomposition may be used. EFFECT: improves efficiency of method. 5 cl, 5 tbl

Description

 The invention relates to the integrated processing of industrial solid waste, in particular bottom sediments of rivers and ponds, galvanic precipitation, precipitation of excess activated sludge from biological treatment plants and other products that pollute the environment and are formed as a result of environmental management.

 Technogenic precipitation (MOT) is a source of environmental pollution due to the presence of a significant amount of oil products, bitumen suspensions, and heavy metals in them. They are a complex mixture with a high water content, in which the main biologically harmless substance is firmly bound to polluting toxic components of organic and inorganic nature, which involves not only the release of particularly toxic impurities for burial, but also the disposal of useful components.

 There are various methods of processing precipitation, partially solving the problems of extraction and neutralization of industrial precipitation with subsequent disposal of the resulting substances.

There is a method of disposing of sludge from biological wastewater treatment plants to obtain a sorbent after mixing sludge with peat and calcining [1] as well as a method of introducing crushed expanded clay into processed sludge or oil sludge before pyrolysis to increase the efficiency of the resulting sorbent [2]
The disadvantage of these methods is the formation of toxic gases during the pyrolysis process, the presence of high concentrations of heavy metals in the resulting sorbents, as well as the need for mineral additives of peat, expanded clay, which themselves are effective sorption materials.

 A known method of treating sludge from sewage treatment plants, in the implementation of which the sludge of primary sumps and activated sludge after preliminary dewatering is mixed with filler material with sand and a disinfecting reagent, is additionally dehydrated to a product with a humidity of 60% and disposed of as fertilizer [3] This method provides the processing of all waste, sludge, excess activated sludge, sand formed at the treatment plant, but in the case of toxic organics and heavy metals, this method is not applicable.

A known method of processing sludge from sedimentation tanks containing iron or aluminum with a solution of sulfuric acid to produce mineral coagulants used as reagents for wastewater treatment [4]
The disadvantage of this method is that the preparation of the coagulant must be carried out at an increased concentration of sulfuric acid when heated, and the resulting reagent contains a large amount of insoluble residue and free acid, which reduces its quality.

The closest in technical essence is the method of complex processing of wastewater and waste from livestock enterprises, providing fertilizer, biogas and purified water. The system provides for preliminary separation of waste into liquid and solid fractions with subsequent processing of fractions into utilizable products. Fertilizer ash is obtained from the solid fraction of effluents after burning, and a liquid homogeneous organic matter is subjected to anaerobic digestion. The resulting methane is used to burn ground particulate matter from the effluent. After fermentation, the liquid fraction enters the flotator, where the contaminants are separated, and partially purified water is sent for biological treatment to a storage pond and after complete biological treatment can be used for technological needs [5]
The disadvantage of this method is that it cannot be used for disposal if man-made sediments, in particular bottom sediments, contain a number of toxic substances, including: petroleum products, non-ferrous and ferrous metals.

 The objective of the present invention is to provide a method for the integrated processing of industrial precipitation, which allows to obtain disposable products from construction sand, sorbent, coagulant from the neutralized sludge, as well as to provide environmentally friendly gas emissions.

 The problem is solved in that the initial technogenic precipitate is processed in several successive stages. First of all, sediment or bottom sediments after dehydration are subjected to separation into pure sand and silt components, in which the bulk of heavy metals and oil products are concentrated.

 Dehydrated sludge is separated on a drum screen in a hydrocyclone. Separated sand and gravel, comprising up to 50% by weight of the initial sediment, can be used as a commercial product in construction, in the manufacture of pavements, or can be laid at the bottom of the river.

The sludge component is divided into 3 fractions, quantitatively depending on the ratio of organic and inorganic substances in the sediment, which undergo the following complex processing:
The first fraction by pyrolysis at 500-550 ^{° C} and subsequent activation of the resulting solid residue gaseous activating agent (a mixture of flue gases and steam) at 750-850 ^C for 5-10 minutes while shooting neutralization of the gaseous products at t < 1000 ^about With turns into a sorption material.

The second fraction after treatment of the aqueous slurry sludge at a flow rate of 0,49-0,5 mg / kg of sulfuric acid to precipitate the content of the latter in pulp and 50-51% at 85 ^{° C} under cooling crystallizes and the obtained substance that is basically a mixture of aluminum sulfate and iron, as well as small amounts of the compounds Mn, Zn, Cu can be used as a mixed coagulant.

 The third fraction of the sludge part of the initial industrial sediment (excess activated sludge, waste and sludge from treatment facilities of agricultural and food enterprises, household waste) is subjected to biodegradation during the cultivation of fungi or microorganisms to reduce its mass. These processes require minimal energy, are simple to implement and, which is essential, environmentally friendly due to their natural origin.

 The proposed scheme for the complex processing of technogenic precipitation, including several heterogeneous technological processes of influencing the initial precipitate, allows us to solve the complex problem of cleaning, neutralizing and disposing of its components.

 The method is carried out on the example of bottom sediments of the river. Moscow, which are heterogeneous in terms of particle size distribution, in terms of the degree of contamination with oil products, heavy metals, and in chemical composition.

 Pretreatment consists in dewatering the sediment to 30-35% moisture and separating it into clean sand and silt components. The bulk of heavy metals and petroleum products are found in sludge. Separation is carried out on a drum screen, which distinguishes particle size classes +10 mm; -10 + 4 mm; -4 + 0 mm, or in a centrifugal field on industrial hydrocyclones along grain of boundary size.

 In the acoustic rotary pulsation apparatus, desorption of organics, including oil oils, from the surface of the solid phase is ensured. The purified sand fraction of precipitation is a commercial product and can be used.

 On the example of one of the samples of bottom sediments when separating by a boundary grain of 74 μm, it was shown that in the thin class of the silt component (-74 μm) after separation of the sandy part, 70% of the material concentrating heavy metals, humus, oil, other organics is concentrated (see table .1).

 The table shows that the sorption material obtained by thermal activation of the sludge of the bottom sediments in water purification from organic pollutants is not inferior to BAU activated carbon in its properties, and significantly exceeds it in the extraction of heavy non-ferrous metals.

 Since the sludge component of sediments and many sediments contains a large amount of metals, it is advisable to process a significant part of it in order to obtain a mixed coagulant, which is used in the future to treat various effluents or to thicken sediments. In addition to aluminum and iron, bottom sludges also contain other metals Mn, Zn, Cu, Ca, which, when the coagulant is extracted, provide it with additional positive qualities in terms of the degree of coagulation.

The process of obtaining coagulant in the proposed method consists in processing the aqueous pulp of the precipitate after separation of the sand component with sulfuric acid, and the water flow in the preparation of the pulp should be 0.49-0.5 kg / kg of sediment, and the sulfuric acid content in the pulp is 50-51 % found that for effective mixing and to ensure completeness of reaction time with a minimum sulfuric acid treatment, the pulp should be heated to ^about 85 and maintaining T: F not less than 1: 0.9.

 A decrease in the concentration of sulfuric acid in the pulp below 50-51% at an optimal water flow rate leads to the formation of aluminum sulfates and iron of greater basicity, which have less solubility, which increases the insoluble precipitate and reduces the yield of commodity coagulant. With an increase in the concentration of sulfuric acid in the pulp above the optimum, medium salts are formed and the product cakes during storage.

 A decrease in the amount of water in the pulp below the optimum (0.49-0.5 kg / kg sludge) dramatically reduces the content of crystalline water, which negatively affects the solubility of the basic salts, and the resulting product is caked during storage. An increase in the amount of introduced water above the optimum leads to the formation of sulfates with great basicity, which, as shown above, is undesirable.

Part of the sludge product enriched with organic technogenic inclusions is subjected to sequential heat treatment, including preliminary drying at t ≅ 150 ^о С to humidity ≅ 30%, the process of organic pyrolysis at t 500-550 ^о С, subsequent treatment with a gaseous activating agent (a mixture of flue gases and water pair) at t 750-850 ^C for 5-10 minutes while shooting neutralization of the gaseous products at t ≅ ^{1000 °} C. Since all vapors generated during heating and the gaseous products of pyrolysis and act novation one stream subjected to thermal treatment at 1000 ^o C t at the optimum conditions of the organization of the combustion process, the flue gases produced contain no environmentally harmful emissions. The process of pyrolysis and activation in these parameters leads to the production of activated semi-coke of a porous structure with good sorption properties. The activated material is discharged into the cooler and then through the classifier to the hopper of the bag stitching machine. The spent gaseous activating agent is supplied as a coolant to the pyrolyzer reactor, hot water from the cooler to the steam generator, and excess steam to the hot water supply system.

EXAMPLE EXAMPLE 1 The starting product samples taken sediment sludge portion has a carbon content of 2.72% and 5.03% first sample subjected to heat treatment and activation at t750 ^{° C} for 8 minutes and the second at t790 ^about C and time 9 min.

As a result, materials with the following sorption properties were obtained:
iodine sorption activity, respectively 17.3% and 27.16%
sorption activity according to methylene blue, respectively 72.0 and 62.9 mg / L.

 In the table. 2 shows comparative indicators of the sorption properties of sample N 2 with respect to BAU grade activated carbon (birch activated carbon) traditionally used in water purification.

 The tests were carried out on water contaminated with the following products with a content in mg / l: oil 2.4; flotation reagents GFR collectors (tar flotation reagent) 8.4 and tallactam 51.0, as well as non-ferrous metal ions: zinc 106.0, copper 8.3. The experiments were conducted under static conditions by contacting sorption materials at a ratio of 1 g of sorbent to 250 g of water for 3 hours. After the end of the process, the filtrate (purified water) was separated on a sieve from the sorbent and analyzed for the residual content of the above pollutants.

PRI me R 2. 300 g of sediment containing 22.4% of FeO ₃ ; 6.6% Al ₂ O ₃ ; 2.6% CaO, pulp in 147 g of water and with stirring 183 g of 93% sulfuric acid begin to be fed. Moreover, the water flow rate is 0.49 kg / kg of sediment, T: W 1: 1,1. С (Н ₂ SO ₄ ) 51%; Acid supply rate 12--15 ml / L min; stirring rate 300-400 1 / min. By the end of supplying heat and acids include slurry temperature was raised ^to 85 ° C, stirring was conducted for an hour, maintaining a constant liquid level. Then the pulp was poured into a crystallizer and cooled to room temperature. In this case, crystallization of salts occurs. The product is dried at room temperature and analyzed, determining the content of Fe ₂ O ₃ , Al ₂ O ₃ , SO ₄ (-2), H ₂ O, insoluble precipitate, free acid and caking during storage for 1 month in air. The composition of the obtained product according to this example is described by the gross formula (Fe, Al) ₂ O ₃ x 2.5 SO ₃ x x 16.8 N ₂ O. The content of insoluble precipitate (N.O.) 2.1% free acid 0.5% The indicators of experience are given in table.3.

 As can be seen from the analysis of the data (Table 3), a deviation from the optimal flow rate of water and acid introduced into the pulp leads to a deterioration in the quality of the coagulant and process indicators.

PRI me R 3. The use of the coagulant obtained by the above technology is possible, for example, when cleaning the effluent of the red department of the fur industry and fermenting the pulp of the Kuryanovskaya aeration station. As a control, commodity aluminum sulfate and technical mixture, CaO 25, are used; FeCl ₃ 5. Sample N3 was used as a coagulant (see Table 2), in which the content of Fe ₂ O ₃ was 15.7 wt. and Al ₂ About ₃ 8.3 wt. The data obtained are given in table.4.

 As can be seen from the obtained data, the degree of purification of the treated waters increases when using a reagent obtained from bottom sludge of the Moscow River as a coagulant.

Since in some technogenic sediments, the sludge part is the largest percentage, it is effective to reduce the total mass by biodegradation of organic substances, for example, during the cultivation of fungi and microorganisms. This process requires minimal energy and is environmentally friendly. During the cultivation of microorganisms-destructors, organic matter decomposes to CO ₂ , H ₂ O and other simple compounds. When decomposing bottom sediments, it is advisable to use different types of cap mushrooms (oyster mushroom, donut, champignons). Depending on the purpose and duration of cultivation of mushrooms on the waste, it can be brought to the stage of formation of fruiting bodies with the harvest and sale of the resulting food products.

 Example 4. The process of biotechnological decomposition of the sludge component of sediments, containing a significant part of organic compounds of plant origin, is similar to the well-known process of biotechnological disposal of plant waste (see table 5).

 This process has several stages. At the first stage, a nutrient substrate is prepared from plant waste for the cultivation of fungi or microorganisms.

In the experiment, 500 g of waste, crushed to particles 2-3 cm in size, was poured with water, boiled for 20 minutes. Then water was decanted, the substrate was added at 1.5% gypsum, and 0.5% of chalk were sterilized and stirred for 1 hour at 100 ^C. After cooling, it was entered in the substrate portion of oyster mushroom mycelium. After 8 days of culture mycelia at ²⁶ ° C formed efficient seed for the 2nd stage of the main process of recycling organic waste.

 At the 2nd stage, the crushed waste was placed in the main working cultivator, mixed, moistened, diluted with neutral ballast to improve the physical structure. Mineral (gravel, expanded clay crumbs, etc.) and organic (crushed polyethylene, polystyrene, etc.) material were used as ballast.

For example, in one of the organic waste disposal implementations to 276 h (dry weight) of crushed waste was added 960 ml water and autoclaved for 1 h at 100 ^C. After cooling the warmed waste into it was added 8.28 g of seed. Step mitseleobrazovaniya held in the dark at 26 ^{° C} and continued for 14 days.

The next stage of the formation of fruiting bodies held at light mycelium superior surface 640, and relative humidity 90% and temperature of 17 ^° C were formed fruiting bodies and crop fungi obtained 19.3 g of dry matter. At the same time, 40% of the organic waste material was decomposed, part of the formed compounds were included in the mycelium and fruiting bodies.

 Thus, the proposed integrated technological scheme allows us to solve the problem of cleaning, neutralizing and disposing of various technogenic sediments, including river bottom sediments, while the sediments are completely processed into recycled substances.

Claims (5)

 1. METHOD FOR INTEGRATED PROCESSING OF TECHNOGENIC SEDIMENTS, including the separation of sludge into fractions, followed by separate processing of each fraction and obtaining useful recyclable products, characterized in that after dehydration and separation of the sand component of sludge, the sludge component is divided into fractions in a ratio depending on the content of organic and inorganic substances, moreover, from one fraction by pyrolysis of the precipitate and activation of the obtained solid residue with a mixture of flue gases and water vapor receive a sorbent, from another fraction after treatment with sulfuric acid, an iron-aluminum coagulant is obtained, and the third fraction is subjected to biotechnological decomposition with cultivation of fungi and microorganisms.  2. The method according to p. 1, characterized in that the separation of the precipitate into sand and silt components is carried out either on a drum screen or in a hydrocyclone. 3. The method according to p. 1, characterized in that the pyrolysis of the precipitate fraction is carried out at 500 550 ^o C, and activation is carried out at 750 850 ^o C for 5 10 minutes with simultaneous fire neutralization of gaseous products at t <1000 ^o C. 4. The method according to p. 1, characterized in that before processing the precipitate fraction with sulfuric acid, an aqueous pulp of the precipitate is prepared at a flow rate of 0.49 0.5 kg / kg of sediment, and the sulfuric acid content in the pulp is 50 51%, and by the end of the feed sulfuric acid, the temperature of the pulp was raised to 85 ^o C and stirred for 1 h 5. The method according to p. 1, characterized in that the substrate for cultivation of fungi or microorganisms is preliminarily prepared from plant waste, the mycelium is cultured at 26 ^° C in the absence of illumination, and then when the surface of the mycelium is illuminated at 640 lux, relative humidity of 90% and temperature 17 ^o With form fruiting bodies.

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