RU2848709C1 - Method for resource-saving processing of sewage sludge including fat-containing waste, by means of mechanical-thermal dewatering with heat energy recycling - Google Patents

Abstract

FIELD: water treatment.

SUBSTANCE: invention relates to the processing of multicomponent sludge from the biological treatment of municipal and industrial wastewater containing fats. It is intended for wastewater in which the ratio of fats to suspended solids is at least 1:3. A distinctive feature of the proposed method is the comprehensive processing of heterogeneous waste (wastewater sludge, fat-containing waste, refuse) in a single technological cycle with heat energy recycling. Temperature control at all stages prevents fat oxidation and sediment formation, while a multi-stage gas cleaning system ensures environmental safety.

EFFECT: end product (granules or bulk material) has a high calorific value and can be used as fuel or raw material for secondary processing, which increases the economic efficiency of the method.

3 cl, 4 dwg

Description

The invention relates to the processing of multi-component sludge from the biological treatment of municipal and industrial wastewater containing fats. It is designed for wastewater in which the ratio of fats to suspended solids is at least 1:3.

The relevance of this invention is due to the fact that in Russia there is a ban on the disposal of certain types of waste, including sewage sludge (Government Resolution No. 1581 of December 10, 2020) in solid municipal waste landfills, which should stimulate waste recycling and disposal activities. Also, starting January 1, 2026, the disposal of not only wastewater sludge from sewage treatment plants, but also fat-containing and biological waste will be prohibited (Federal Law No. 89-FZ "On Production and Consumption Waste," Article 12: Prohibits the disposal of waste subject to disposal (including WWS starting in 2026). SanPiN 2.1.7.2790-10 "Sanitary and Epidemiological Requirements for Waste Management" restricts the placement of WWS in landfills without prior treatment (dehydration, thermal drying, disinfection). Thus, there is a growing demand in society for technologies that allow for the transformation of wastewater sludge into secondary material resources directly at the production sites of treatment plants.

An important issue addressed by the proposed method is the specific properties of animal fats, which manifest themselves during the processing process. Currently, the proposed technology yields a dehydrated, environmentally non-toxic, single-phase product suitable for processing into fuel briquettes, for soil reclamation (improving the structure of degraded lands), for landscaping with landscape elements, as a stabilizing additive in road construction, for producing organic fertilizers, and for incineration with energy recovery.

Currently, there are many technological solutions for sludge processing, including both individual operations and complex solutions that allow obtaining a certain final product. The modern technological scheme of sludge processing includes the following processes: compaction (thickening), stabilization of the organic part of the sludge, conditioning, dewatering, utilization of valuable products, liquidation [Khisameeva L.R., Selyugin A.S., Abitov R.N., Busarev A.V., Urmitova N.S. Treatment of municipal wastewater sludge. - Kazan: Publishing house of Kazan. state University of architecture and civil engineering, 2016. - 105 p. p. 15].

The most well-known methods of sewage sludge stabilization are anaerobic digestion and aerobic stabilization.

A known method for treating sewage sludge (patent RU No. 2232135 C2, authors: Daineko F.A., Danilovich D.A. dated September 13, 2002, IPC C02F 11/00, published July 10, 2004) includes clarification of wastewater in primary settling tanks, treatment in aeration tanks, clarification in secondary settling tanks, thickening of excess activated sludge, anaerobic digestion in methane tanks, thickening of digested sludge, and dewatering in filter presses. To reduce the load on the methane tanks and reduce heat consumption, excess activated sludge after secondary settling tanks is divided into streams, one of which is sent to an aeration tank-stabilizer instead of a methane tank.

A method for treating activated sludge and sewage sludge is known (RU Patent No. 2252922 C2 dated October 30, 2002, authors: Akhmadullina F. Yu., Asadullin A. Z., Zakirov R. K. et al. IPC C02F 11/02, published May 27, 2005, Bulletin No. 15). To implement the method, activated sludge and its mixture with raw sewage sludge are subjected to aerobic stabilization. Aerobic stabilization is carried out in a periodic aeration mode, provided that the aeration duration does not exceed two hours. The technical effect is to improve the water-releasing properties of stabilized activated uncompacted sludge and its mixture with sludge, reduce the duration of the stabilization process to 2-4 days and reduce energy costs.

However, the above-described methods of wastewater sludge treatment have a significant drawback: both aerobic stabilization and anaerobic digestion result in mineralization and reduction of the organic content of the sludge, which limits the range of desired products from the sludge and reduces its energy value for subsequent use as fuel. Furthermore, the disadvantages of the above-described sludge treatment methods for this purpose include their relatively lengthy processing time (at least 2-4 days), requiring significant space when processing large volumes, and energy consumption due to the stabilization and digestion processes being carried out under thermophilic conditions. They also do not provide for sufficient reduction of sludge moisture content and are incapable of treating fatty wastewater sludge.

A known method for processing wastewater sludge (RU Patent No. 2486140 C1 dated 23.05.2012, authors: Khalturina T.I., Gavrilova Yu.V., Churbakova O.V., Kurilina T.A. IPC C02F 11/12, C02F 1/46, B01D 43/00, published 27.06.2013, Bulletin No. 18), involves electrical processing with asymmetric alternating current followed by filtration for concentration. Before electrical processing, the sludge is subjected to vibroacoustic action in two frequency sub-range processing modes with a lower frequency of 0.3-0.8 kHz and an upper frequency of 9-18 kHz.

The use of vibroacoustic stimulation followed by electrical treatment with asymmetric current effectively improves the water-releasing capacity of sludge. A disadvantage of this method for solving the problem is the complexity of the equipment and process involved, the need for separate study for the treatment of fat-like substances, and the need for it to be part of a complete sludge treatment cycle.

A method for biological treatment of wastewater with waste reduction is known (RU Patent No. 2106317 C1, authors: Magiy M. Yu., Stepakin A. F., Radchenko D. A. et al. dated 20.12.1995, IPC C02F 11/02, published 10.03.1998), in which, in order to destroy the structure of excess activated sludge and implement a closed cycle of biological treatment, the excess sludge is compacted and subjected to thermochemical destruction at a pH of 1.8-4.0, a temperature of 130-180 ° C and a pressure of 0.3-1.0 MPa for 1.5-2.0 hours. The technical result of the proposed method is the maximum destruction of the structure of excess activated sludge. The disadvantage of this method for solving the problem is that the proposed method requires high temperatures and low pH values for implementation, is difficult to implement and involves the treatment of only activated sludge without taking into account other types of wastewater sludge.

A method is known for improving the dewatering capacity of activated sludge (patent RU No. 2090522 C1, author: Geza Louis Kovacs, convention priority 31.05.1990 US 531059, C02F 11/18, published 20.09.1997), including heat treatment with preliminary acidification of activated sludge to pH 2-4 and subsequent dewatering, wherein heat treatment of activated sludge with a solids content above 15% by weight is carried out in an oxygen-free environment at a temperature of 126-200 °C and a pressure above atmospheric to maintain the sludge in a liquid state for at least 15 minutes, then the activated sludge is neutralized to a pH of at least 5 and again subjected to heat treatment, and dewatering is carried out until the solids content is more than 30% by weight. Thermal treatment is carried out by direct contact of concentrated activated sludge with pressurized steam. A disadvantage of this method for improving the dewatering capacity of activated sludge for this purpose is that it is an expensive technology that does not take into account the specific presence of fat-like substances in wastewater sludge.

A known method for processing wastewater sludge (RU Patent No. 2342204 C1, authors: F.V. Karmazinov, F.I. Lobanov, et al.) involves converting the sludge into a paste-like state by mixing it with a paste-forming agent in the form of aluminosilicates, followed by granulation and drying of the resulting granules. A disadvantage of this method for solving the stated problem is the low environmental friendliness of the resulting granules due to the presence of aluminosilicates in their composition. It also fails to take into account the specifics of preparing and drying sludge containing fat-like substances.

A method for processing wastewater sludge is known (patent RU No. 2671742 C1, authors: Katlovsky A.V., Elistratov A.V., Patrakov A.V. et al.), including the processing of wastewater sludge and other products polluting the environment and formed as a result of the process of nature management. The sludge processing system comprises a device for mechanical cleaning of the sludge, a mechanical thickener, a reactor for thermal decomposition of liquid sludge, including a tubular body having an inlet for feeding sludge under a pressure of at least 25 MPa and an outlet for decomposition products, as well as a heater installed around the body, configured to heat the sludge to a temperature of at least 450°C, a device for separating the resulting decomposition products into combustible gas and sludge, a device for dewatering the sludge, connected to the outlet of the decomposed sludge of the sludge separation device. The combustible gas outlet from the sludge separation unit is connected to a gas generator unit for generating heat and/or electricity from the combustible gas. A disadvantage of this method for solving the problem is its inability to process fat-like substances, as fats tend to adhere to the chamber walls and nozzles, leading to clogging of the spray heads and the formation of a crust on the internal surfaces, reducing heat transfer, and, consequently, increased energy costs for purification. Furthermore, at the high temperatures specified in the method, there is a high risk of ignition due to the finely dispersed fat suspension in the hot air. Furthermore, the reactor pressure of 30 MPa (300 atm) during processing, combined with a temperature of 500°C, indicates an increased risk of the process.

An analysis of other literary sources indicates the absence of a technological solution for the preparation of fat-containing sludge for its joint thermal treatment with excess sludge and raw sludge from industrial and/or domestic wastewater.

The objective of the present invention is to develop a method for the thermal utilization of all types of wastewater sludge—screenings or other filtering equipment, raw sludge, excess activated sludge, floating products from grease traps, and fat-containing flotation sludge—by means of their combined drying with preliminary preparation of each component, taking into account its specific properties. This method simultaneously achieves process stability and the reliable production of a single-fraction processed sludge in the form of bulk material or granules. It also reduces the energy consumption of fuel for heating fat-containing waste by recovering heat from the drying process. The gas component of sludge drying is also treated, thereby ensuring a stable, positive environmental situation in the area occupied by wastewater treatment facilities and in areas adjacent to wastewater treatment facilities. The method results in an environmentally friendly product that can be used as fuel due to its high calorific value or as a raw material for further processing in road construction, municipal services, and agriculture.

The technical result of the claimed invention is a sequence of sewage sludge treatment stages, taking into account the specific properties of fats as a component of the sewage sludge mixture, manifested during thermal treatment. This process substantiates and achieves optimal temperature effects and enables the recovery of thermal energy used to optimize the technology for producing a homogeneous sludge component. It should also be noted that the disposal of dry sewage sludge containing fats by incineration can significantly improve the system's energy efficiency and reduce incineration operating costs.

The technical result is achieved in that the components of sewage sludge are subjected to special preparation, waste from screens and/or other filtering equipment is collected in a receiving tank, then sent to a crushing and dewatering shop with subsequent feeding to a storage tank, activated sludge/or a mixture of activated sludge and raw sludge, if any, is sent to a receiving tank and then fed to a joint dewatering shop, using mechanical equipment and reagents to a moisture content of 72% to 85%, and sent to a storage tank for receiving the sludge mixture, fats, when their concentration in wastewater in a ratio to suspended solids of no more than 1:3, are separated in settling-type structures, for example, in combined grease traps, the resulting fat mass with a moisture content of 60-75%, which is an emulsion of the 1st kind, is placed in a fat mass averager with a mixer with a rotation speed of 30 to 60 rpm to obtain a homogeneous mass and a system Heating the fat mass to 60 to 80°C. The temperature is selected depending on the type of fat mass. This prevents the fat mass from solidifying and improves separation from water. It also ensures the temperature is not too high to prevent fat dissolution and homogenization of the system. Heat for heating is supplied by a system transporting purified hot gases generated in a paddle-type dryer and transported from the scrubber through a fan. Heat recovery from the wastewater sludge drying process not only reduces the costs of mandatory heating of the fat mass during processing but also has an environmental benefit, as it prevents the release of hot steam and gases into the atmosphere. From the fat mass blender with a paddle mixer, the fat mass is transferred to a tank with a paddle mixer, where it is mixed with a portion of the dried sludge, which is heated to 70-110°C and discharged from the dry, free-flowing sludge bin, at a ratio of 1 part fat to 2-3 parts dry sludge (by weight). In this case, the dried sludge acts as an additive and acts as an adsorbent, reducing the agglomeration and clumping of the dehydrated fat mass, facilitating transportation by improving flowability, and ensuring uniform drying. This process is also optimized—sludge drying time can be reduced, as some of it has already been dried. This approach utilizes the principle of sludge recirculation, which maintains a high temperature after drying and improves the processes described above. The resulting mixture is combined with a pre-dewatered mixture of raw sludge and/or activated sludge and crushed dewatered screenings and sent to a sludge mixture receiving tank equipped with a ventilation system and screw conveyors installed at the bottom of the bin for mixing the sludge and feeding it into the receiving hopper of a dosing screw pump installed directly below the bin and designed to transport portions of the dewatered sludge to a paddle-type dryer. In this case, the use of a paddle-type dryer is justified by its specific design, which incorporates mechanical mixing within the drying unit, preventing clumping and adhesion of the fat component of the sludge. Intensive mixing ensures uniform heat distribution, which is important for sludges with a high fat content, prone to localized overheating or uneven moisture evaporation. Furthermore, the ability to adjust the temperature, paddle speed, and residence time of the material allows the drying process to be tailored to different types of fat-containing sludge. The sealed design prevents the spread of unpleasant odors typical of fatty sludge. During the drying process, the mixture is exposed to a hot gas environment at a temperature of 70-110°C, preventing the oxidation of fats and the formation of sticky deposits in the dryer. At temperatures above 110°C, fats begin to oxidize, forming sticky polymer deposits, and valuable organic components are destroyed. Heating of the environment in the paddle-type dryer is achieved by heat transfer from the coolant through a metal barrier. The coolant used is diathermic oil at a temperature of 200-250°C, prepared by heating diathermic oil in a thermal oil boiler. The sludge is dried to a moisture content of 5 to 10%. During the sludge drying process, byproducts are formed consisting of vapors, gases, including volatile fatty acids, and dust from the dried sludge. Heated air is introduced into the body of the paddle-type dryer to remove the byproducts. The byproducts are transferred to a discharge channel through an outlet and sent first to dry gas cleaning in a mechanical cleaning unit—inertial cyclones, where mechanical impurities are precipitated from the gas component. These impurities are then sent to a big bag to collect the captured dust. The gas component, freed from mechanical impurities, is sent to a gas scrubber (Venturi scrubber) for cleaning, where vapor condensation and wet cleaning of fine dust particles occur. The gas scrubber uses industrial water circulating in a closed circuit and supplied by a pump to the sprayers, contaminated water after the gas scrubber is sent to sewage treatment facilities, the purified gas component is removed from the gas scrubber through a special fan for heating the fat mass in the equalizer, the fan also serves to create the necessary vacuum in the system of the paddle-type drying apparatus, the dried sludge with a moisture content of 5-10% and a temperature of 70-110 ° C is removed from the paddle-type drying apparatus through an opening arranged at its end and fed by an inclined screw conveyor into a big bag with a heat-resistant liner, then part of the dried loose sludge is fed into a container with a paddle mixer and a heating system for mixing with the fat mass, the remaining dried loose sludge can be sent to a screw conveyor and subjected to molding in The granule size is determined by the optimization of the combustion process to obtain a fully ashed product. Previous studies on the incineration of wastewater treatment plant sludge have shown that granule sizes between 0.8 and 1 cm yield unmineralized sludge at the fracture, limiting its applicability. Furthermore, insufficiently dried sludge is prone to rotting. Dried granular or free-flowing sludge can be used as a secondary fuel resource, as the presence of fat-containing sludge in this case results in its high calorific value, or it can be used as raw material for further processing.

The achievement of technical results is also affected by the fact that if industrial wastewater contains fats in a concentration of more than 300 mg / l, the wastewater is sent to grease traps, the separated fat mass is sent for processing into technical fat or biodiesel fuel, wastewater with the remaining concentration of fats is sent to a pressure flotation tank, into which reagents are introduced, since the fats are emulsified, for better separation of the emulsion, it is advisable to introduce a demulsifier and a cationic flocculant, the dispersion medium is sent for further purification in biological treatment facilities, and the separated fat mass with a moisture content of 90-96% is sent to an equalizer with a mixing device and a first heating system to 60-80 ° C, then sent to a tank with a second heating system to 60-80 ° C, equipped with a mixing zone with a paddle mixer and a settling zone, a demulsifier solution is dosed into the mixing zone. The demulsifier is selected based on the characteristics of the fat mass and cost considerations. Nonionic surfactants (such as OR-10) may be the most preferred in this case, as they effectively reduce emulsion stability and are applied at a dosage of 0.01-0.1% of the fat mass. The resulting heating reduces viscosity and accelerates subsequent coalescence. The emulsion is stirred at a stirrer speed of over 100 rpm for 10-20 minutes, resulting in a homogeneous mass. The mixing speed depends on the nature of the fat mass, and its range is determined, firstly, by the sufficient creation of a homogeneous mass. In the settling zone, additional water is separated from the fat mass, reducing the fat mass moisture content to 85-92%. The separated water is sent to the head of the treatment plant. The fat mass, pre-treated with an emulsifier solution at a dose of 0.1-0.4%, is sent to vibrating screens. Treatment with the emulsifier optimizes the vibratory separation process, increasing the efficiency and quality of fat mass separation in the subsequent fat separation step – separation. The use of vibrating screens allows for the production of fat mass with a particle size of no more than 1 mm, which is important for subsequent separation. The separated fat mass, which is a finely dispersed emulsion, is treated with a demulsifier and sent to a disk separator, where effective phase separation occurs due to centrifugal force. A demulsifier significantly improves separation efficiency; demulsifier doses are 0.05-0.2% of the fat mass. After passing through the disc separator, the fat mass, with a moisture content of 88-90%, is sent to a container with a paddle mixer, where it is mixed with a portion of the dried cake, discharged from the paddle dryer at a temperature of 70-110°C, for mixing with the hot dried cake. The procedure then follows claim 1.

Also, achieving technical results is affected by the fact that, when raw sludge (active excess sludge) acidifiers are used in the wastewater treatment process, a reagent system is added to the sludge preparation process to prepare a lime or soda solution to alkalize the sludge to a pH of 6.5 to 7.5. High VFA (acetic, propionic, and butyric acid) content lowers the pH to 4.5-5.5, altering the sludge structure and reducing viscosity, which impacts the dewatering and drying processes. This can affect the drying process. The drying temperature is maintained at 75-90°C, as volatile fatty acids are released into the gas environment as the temperature rises. This set temperature is maintained to avoid overheating and increased acid evaporation. An alkaline scrubber is added to the gas purification process to capture _H2S and volatile acids. This sediment has a reduced calorific value and can be used for the formation of engineering barrier landfills, land reclamation, terrain leveling, etc.

Taking into account the above, along with the disclosed cause-and-effect relationship between the set of features of the claimed invention and the achieved technical results, it can be stated that the problem posed as the basis for creating a method for resource-saving processing of sewage sludge, including fat-containing waste, through mechanical-thermal dewatering with thermal energy recycling, has been fully solved. The invention, through a logically justified sequence of processing stages, enables the greening of the sewage sludge treatment process and allows all operations to be performed directly at the treatment facility site, without alienating land for sludge beds, thereby enabling the conversion of sludge into secondary material resources. Heat recovery will also reduce energy costs for heating the fat mass.

Fig. 1 shows a flow chart of the implementation of a method for resource-saving processing of wastewater sludge, including fat-containing waste, by mechanical-thermal dewatering with recycling of thermal energy.

Legend:

The claimed method is implemented in accordance with the process flow diagram shown in Fig. 1.

Legend to Fig. 1:

1 - a receiving tank for waste from screens and/or other filtering equipment;

2 - waste crushing and dewatering shop;

3 - receiving tank for excess activated sludge;

4 - excess activated sludge dewatering shop;

5 - storage tank for receiving dewatered sludge and waste and prepared fat mass;

6 - screw metering pump;

7 - fat mass averager with a paddle mixer and a heating system;

7.1 - homogenizer mixer;

8 - container with a paddle stirrer and heating system;

8.1 - container stirrer;

9 - paddle type drying apparatus;

10 - bunker for dried bulk sludge (big bag with heat-resistant liner);

11 - screw conveyor;

12 - thermal oil boiler;

13 - inertial cyclone;

14 - big bag for collecting captured dust;

15 - gas scrubber (Venturi scrubber);

16 - sewage treatment facilities;

17 - fan.

Screenings from screens and/or other screening equipment are collected in a receiving tank (1), then sent to the crushing and dewatering shop (2), followed by feeding to the sludge mixture receiving tank (5). Activated sludge and raw sludge are sent to a receiving tank (3) and then fed to the combined dewatering shop (4). Dewatered sludge with a moisture content of 72% to 85% is sent to the sludge mixture receiving tank (5). Fats are separated from wastewater in settling-type structures, for example, in combined grease traps, the resulting fat mass with a moisture content of 60-75% is placed in a fat mass equalizer (7) with a stirrer (7.1) with a rotation speed of 30 to 60 rpm to obtain a homogeneous mass and a system for heating the fat mass to 60 to 80°C, heat for heating is supplied by a system for transporting purified hot gases formed in a paddle-type drying apparatus (9) and transported from a scrubber (15), through a fan (17), from the fat mass equalizer (7) with a paddle stirrer (7.1). The averaged fat mass is sent to a container (8) with a paddle mixer (8.1), in which the fat mass is mixed with a portion of the hot dried sediment removed from the paddle-type drying apparatus (9) into the bin of dried bulk sediment (10) in a ratio of 1 part of fat to 2-3 parts of dry sediment (by weight), the resulting mixture is combined with a pre-dewatered mixture of raw sediment and/or activated sludge and crushed dewatered waste and sent to a bin for receiving the sediment mixture (5), equipped with a ventilation system and screw conveyors installed at the bottom of the bin for mixing the sediment and feeding it into the receiving funnel of the dosing screw pump (6), installed directly under the bin and intended for transporting portions of the dewatered sediment into the paddle-type drying apparatus (9), in which the mixture comes into contact with a hot gaseous medium having a temperature 70-110°C, which will prevent the possibility of oxidation of fats and the formation of sticky deposits in the paddle-type dryer (9), heating of the medium in the paddle-type dryer (9) is carried out by heat transfer from the coolant through a metal barrier, diathermic oil with a temperature of 200-250°C is used as a coolant, which is prepared by heating diathermic oil in a thermal oil boiler (12), drying of the sediment is carried out to a humidity of 5 to 10%, in the process of drying the sediment, by-products are formed consisting of vapors, gases, including volatile fatty acids and dust from the dried sediment to remove by-products inside the body of the paddle-type dryer (9) heated air is supplied, which is heated, by-products are moved into the discharge channel through the outlet and are first sent to dry gas cleaning in the mechanical cleaning unit - inertial cyclones (13), in which the sedimentation of mechanical impurities from the gas component occurs, they are sent to a big bag for collecting the captured dust (14), the gas component, purified from mechanical impurities, is sent for cleaning to a gas scrubber (Venturi scrubber) (15), in which condensation of vapors and wet cleaning from small fractions of dust occurs, in the gas scrubber (15) they use industrial water circulating in a closed circuit and fed by a pump to the sprayers, contaminated water after the gas scrubber (15) is sent to sewage treatment facilities (16), the purified gas component is removed from the gas scrubber (15), through a special fan (17) for heating the fat mass in the averaging tank (7), the fan also serves to create the necessary vacuum in the system of the blade-type drying apparatus (9), the dried sediment with a moisture content of 5-10% and with a temperature of 70-110°C is removed from the paddle-type drying apparatus (9) through an opening arranged at its end and fed by an inclined screw conveyor into a big bag with a heat-resistant liner (10), then part of the dried loose sediment is fed into a container with a paddle mixer and a heating system (8) for mixing with fat mass, the remaining dried loose sediment can be sent to a screw conveyor (11) and subjected to molding in the form of granules measuring 0.5 by 0.5 cm, the dried granulated or loose sediment can be used as a secondary material resource as a fuel, since in this case the presence of fat-containing sediment determines its high calorific value or can be used as a raw material for further processing.

Fig. 2 shows a workshop for mechanical dewatering and drying of sludge.

Legend to Fig. 2:

5 - Accumulator for receiving dewatered sludge and waste and prepared fat mass;

6 - Screw metering pump;

7 - Fat mass averager with a paddle mixer and a heating system;

7.1. - Mixer mixer;

8 - Container with a paddle stirrer and heating system;

8.1 - Container stirrer;

9 - Paddle type drying apparatus;

10 - Bunker for dried bulk sludge;

10.1 - Big bag with heat-resistant liner

11- Inclined screw conveyor (screw conveyor);

12 - Thermal oil boiler;

13 - Inertial cyclone;

14 - Big bag for collecting trapped dust;

15 - Gas scrubber (Venturi scrubber);

16 - Sewage treatment plants;

17 - Fan;

18 - Scrubber capacity;

19 - Circulation pump for scrubber;

Pipelines:

P ₁ - an air duct that removes vapors from a blade-type drying apparatus into an inertial cyclone;

P ₂ - drainage pipeline;

P ₃ - pipeline for feeding dewatered sludge to the drying unit;

P ₄ - air duct for mechanically cleaned air;

P ₅ - technical water pipeline.

Fig. 3 shows a photograph of the dewatered sediment and the dried sediment.

Fig. 4 shows a flow chart of an example of the implementation of the claimed method. ("Mechanical Dewatering and Sludge Drying Plant of the BMZ-CMOS series").

The implementation of the claimed method is demonstrated using the example of the operation of a sludge dewatering and drying plant with a capacity of 500 kg/hour.

The BMZ-CMOS series Mechanical Dewatering and Drying Plant (hereinafter referred to as the “BMZ-CMOS Plant”) is designed to carry out mechanical dehydration of sludge from sewage treatment plants, followed by drying of the dewatered sludge to a residual moisture content of less than 20%.

The dried product is aimed at forming pilots.

Gas emissions from sludge drying are purified to meet established emission standards for atmospheric air.

The workshop consists of prefabricated modular units installed on a concrete foundation. The assembled modules form an insulated building, housing separate process areas performing specific process functions, along with auxiliary rooms. This design ensures thermal insulation and ease of operation of the equipment. The modules are connected by bolted and welded joints.

The BMZ-CMOS workshop operates in conjunction with a thermal oil boiler house located in close proximity to the site.

Fig. 4 shows the process flow diagram of sludge dewatering in the BMZ-CMOS series mechanical dewatering and drying plant (Drying capacity 500 kg/hour).

Legend to Fig.4:

1.1 Intermediate sediment capacity;

1.1.1 Stirring system (pneumatic stirring system with disc aerators);

2.1 Screw pump for feeding thickened sludge for dewatering;

3.1 Screw sludge dewaterer (screw dehydrator);

4.1 Flocculant dosing pump;

5.1. Automatic flocculant preparation unit equipped with a dry matter dispenser;

6. Accumulator for receiving dewatered sludge and prepared fat mass;

7. Fat mass averager with a paddle mixer and heating system;

7.1. Mixer mixer;

8. Container with a paddle stirrer and heating system;

8.1 Container stirrer;

6. Screw metering pump;

9. Paddle type dryer;

10. Bunker for dried bulk sludge;

11. Inclined screw conveyor;

10.1. Big bag with heat-resistant liner;

12. Thermal oil boiler;

13. Inertial cyclone;

14. Big bag for collecting trapped dust;

15. Gas scrubber (Venturi scrubber);

16. Sewage treatment plants;

17. Fan.

The characteristics of sediment and fat mass are presented in Table 1:

Table 1 - Main technological characteristics of sediment and fat mass

Name Units of measurement Calculated data Note Sludge dewatering process line Calculated dehydration parameters Original product compacted sediment humidity 95-99% Estimated flow rates of compacted sludge entering dewatering - by dry matter kg/day 1800 kg/h 75.0 - by volume with humidity of 98% ^m3 /day 89.1 at a density of 1.01 t/m³ The moisture content of dewatered sludge is not more than % 85.0 Volume of dewatered sludge ^m3 /day 11.3 at a density of 1.06 t/m³ Amount of dewatered sludge kg/day 12000.0 kg/h 500.0 Volume of centrate removed during dehydration ^m3 /day 86.8 Consumption of centrate removed during dewatering ^m3 /h 3.2 Flocculant dose* g/kg d.v. 5 Daily consumption of commercial reagent* kg/day 9.0 Strength of the dosing solution % 0.1 Daily volume of solution l/day 9000 Estimated consumption of fat mass - by dry matter kg/day 180 Humidity after a grease trap % 70 Volume of hydrated fat mass ^m3 /day 257 Mass of the introduced dried sediment kg/day 360

The compacted sludge is fed through a pressure pipeline to the dewaterer's dosing tank. The sludge then enters the flocculation tank through a V-shaped overflow. In this tank, a reagent, supplied by a flocculant solution dosing pump, is mixed with the sludge by a special mixer until flocculation occurs. The reagent-bound sludge then enters the dewatering drum, which consists of a screw conveyor rotating at a constant speed within a cylindrical housing. The housing consists of a series of alternating fixed rings, floating rings, and gap spacers. The pitch of the screw flights decreases from the thickening zone to the dewatering zone.

One section of the drum is designed for sludge thickening, the other for dewatering. In the thickening zone, the filtrate flows out under the force of gravity. In the dewatering zone, the pitch of the screw flights decreases, increasing the pressure in the drum. The filtrate flows out through the gaps between the rings. The pressure plate (E), installed at the end of the screw, increases the internal pressure in the drum.

The dewaterer is designed so that water is used only to wet the sludge inside the drum, preventing it from drying out during short shutdowns (between shifts). The constant movement of the rings relative to each other prevents the drum from clogging.

The treatment of sediment with a flocculant solution occurs as follows:

To increase water yield, it is necessary to change the structure of the solid phase of the sludge, which is achieved by adding a flocculant to the sludge. Working solutions are used at a concentration of 0.1-0.2%. The flocculant grade, solution concentration, and reagent dosage are determined experimentally during commissioning.

The flocculant solution is prepared using the AFP-500 automated unit (5.1), equipped with a dry matter dispenser. The operator loads the commercial reagent into the dry matter dispenser's receiving bin.

The AFP-500 (5.1) unit has a three-section body with overflow baffles. The prepared solution is dispensed from the last section, and after it is empty, water is fed into the first section at the level sensor's command, displacing the solution prepared in the previous cycle into the second section. It matures there during the time between fillings. Simultaneously with the water, a dry matter dosing auger feeds granulated commercial flocculant from the receiving bin into the first section. The amount of commercial reagent fed is determined by the feed time. The solution from the first section correspondingly displaces the solution from the second to the third. The level in the third section rises, and when the upper operating level is reached, the level sensor signals that water flow into the first section is stopped. The dissolution process is intensified by mixers located in all sections.

The prepared solution is fed into the receiving tank of the screw sludge dewaterer (3.1) using a dosing pump (4.1) in automatic mode.

Fats separated from wastewater when their concentration in wastewater in a ratio to suspended matter is no more than 1:3 are separated in settling-type structures, for example in combined grease traps with a humidity of 60-75%, the fat mass, which is an emulsion of the 1st kind, is placed in a fat mass equalizer (7) with a mixer (7.1) with a rotation speed of 30 to 60 rpm to obtain a homogeneous mass and a system for heating the fat mass to 60 to 80 °C, heat for heating is supplied by a system for transporting purified hot gases formed in a paddle-type drying apparatus (9) from a scrubber (15), through a fan (17), from the fat mass equalizer (7) with a paddle mixer 7.1, the fat mass is sent to a tank (8) with a paddle mixer (8.1), in which the fat mass mixed with a portion of the hot dried sludge discharged from the paddle-type dryer (9) into the bin for dried bulk sludge (10) in a ratio of 1 part fat to 2 parts dry sludge (by weight), the resulting mixture is combined with a pre-dewatered mixture of raw sludge and/or activated sludge and crushed dewatered waste and sent to a sludge mixture receiving tank (5) equipped with a ventilation system and screw conveyors installed at the bottom of the bin for mixing the sludge and feeding it into the receiving funnel of a screw dosing pump (6) installed directly under the bin and designed to transport portions of dewatered sludge to the paddle-type dryer (9), in which the mixture comes into contact with a hot gas medium having a temperature of 70-110°C, which will prevent the possibility of oxidation of fats and the formation of sticky deposits in the paddle-type dryer (9), heating the medium in the drying in a paddle-type device (9) it is produced by heat transfer from the coolant through a metal barrier, diathermic oil with a temperature of 200-250°C is used as a coolant, which is prepared by heating the diathermic oil in a thermal oil boiler (12), the sediment is dried to a moisture content of 5 to 10%, during the drying process of the sediment by-products are formed, consisting of vapors, gases, including volatile fatty acids and dust from the dried sediment to remove by-products inside the housing of the paddle-type drying device (9) heated air is supplied, which is heated, the by-products are moved into the discharge channel through the outlet and sent first to dry gas cleaning in the mechanical cleaning unit - inertial cyclones (13), in which the sedimentation of mechanical impurities from the gas component occurs, they are sent to a big bag for collecting the captured dust (14), cleaned of mechanical impurities, the gas component is sent for cleaning to the gas scrubber (Venturi scrubber) (15), in which condensation of vapors and wet cleaning from small fractions of dust occurs, in the gas scrubber (15) they use technical water circulating in a closed circuit and supplied by a pump to the sprayers, contaminated water after the gas scrubber (15) is sent to the sewage treatment plant (16), the purified gas component is removed from the gas scrubber (15), through a special fan (17) for heating the fat mass in the equalizer (7), the fan also serves to create the necessary vacuum in the system of the paddle-type drying apparatus (9), the dried sediment with a moisture content of 5-10% and a temperature of 70-90 ° C is removed from the paddle-type drying apparatus (9) through an opening arranged at its end, and is fed by an inclined screw conveyor to a big bag with a heat-resistant liner (10.1), then part of the dried bulk sediment is fed into a container with a paddle mixer and a heating system (8) for mixing with fat mass, the remaining dried bulk sediment can be sent to a screw conveyor (11) and molded into granules measuring 0.5 by 0.5 cm.

The results of the analysis of the dried sediment are presented in Table 2.

Table 2 - Results of the analysis of dried sediment

Moisture content of the original sediment % 85 Moisture content of dried sediment % 20 The amount of dry matter in the sediment kg/hour 74 Feeding the initial sludge kg/hour 490 Dried product kg/hour 92 Evaporated moisture kg/hour 398 Moisture in sediment kg/hour 18 Minimum sewage treatment plant productivity. ^m3 /day 5880 Sewage treatment plant capacity max. ^m3 /day 8880 Thermal energy consumption kW*h 319

The results of the analysis of the OSC sediment after drying are presented in Table 3.

Table 3 - Results of the analysis of the OSC sediment after drying

Indicator The result of the analysis of sludge sediment after drying MAC
according to GOST R 17.4.3.07-2001
Requirements for sewage sludge when used as fertilizers for group 1 for all types of agricultural crops Environmental hazard class Applies to sludge from domestic and municipal wastewater Hydrogen index of salt extract, units, pH 5.9 5.5-8.5 Mass fraction of moisture, not more than 6.7 Not standardized Mass fraction of organic matter, % of dry matter, not less than 30 >20 Mass fraction of total phosphorus (P ₂ O ₅ ), not less than 1.63 >1.5 Mass fraction of total potassium (K ₂ O), not less than Not standardized Gross content of heavy metals, mg/kg, no more than Lead <250 Cadmium <15 Nickel 13.4 <200 Chromium <500 Copper 99 <750 Zinc 394 <1750 Mercury <7.5 Arsenic <10

Claims (3)

1. A method for resource-saving processing of sewage sludge, including fat-containing waste, by mechanical-thermal dewatering with recycling of thermal energy, characterized in that the components of the sewage sludge are subjected to special preparation, namely, waste from screens and/or other filtering equipment is collected in a receiving tank, then sent to a crushing and dewatering shop with subsequent feeding to a storage tank, activated sludge or a mixture of activated sludge and raw sludge, if any, is sent to a receiving tank and then fed to a combined dewatering shop, using mechanical equipment and reagents to a moisture content of 72% to 85%, and sent to a storage tank for receiving the sludge mixture, fats, when their concentration in wastewater in a ratio to suspended solids of no more than 1:3, are separated in settling-type structures, for example, in combined grease traps, the resulting fat mass with a moisture content of 60-75%, representing an emulsion of the 1st kind is placed in a fat mass equalizer with a stirrer with a rotation speed of 30 to 60 rpm to obtain a homogeneous mass and a fat mass heating system from 60 to 80 °C, heat for heating is supplied by a system for transporting purified hot gases formed in a paddle-type drying apparatus and transported from a scrubber, through a fan, from a fat mass equalizer with a paddle stirrer, the fat mass is sent to a container with a paddle stirrer, in which the fat mass is mixed with a portion of the dried sediment having a temperature of 70-110 °C and removed from the bin of dried loose sediment in a ratio of 1 part fat to 2-3 parts dry sediment by weight, the resulting mixture is combined with a pre-dewatered mixture of raw sediment and/or activated sludge and crushed dewatered waste and sent to a mixture receiving tank sludge, equipped with a ventilation system and screw conveyors installed at the bottom of the bin for mixing the sludge and feeding it into the receiving funnel of a dosing screw pump installed directly under the bin and designed to transport portions of dewatered sludge into a paddle-type dryer, in which the mixture comes into contact with a hot gas medium having a temperature of 70-110 ° C, which will prevent the possibility of oxidation of fats and the formation of sticky deposits in the paddle-type dryer, heating of the medium in the paddle-type dryer is carried out by heat transfer from the coolant through a metal barrier, diathermic oil with a temperature of 200-250 ° C is used as a coolant, which is prepared by heating diathermic oil in a thermal oil boiler, drying of the sludge is carried out to a moisture content of 5 to 10%, in the process of drying the sludge, by-products are formed consisting of vapors, gases, including volatile fatty acids and dust from the dried sediment, to remove by-products, heated air is supplied into the housing of the paddle-type drying apparatus, by-products are moved into the discharge channel through the outlet and sent first to dry gas cleaning in the mechanical cleaning unit - inertial cyclones, in which the sedimentation of mechanical impurities from the gas component occurs, they are sent to a big bag to collect the captured dust, the gas component cleaned of mechanical impurities is sent for cleaning to the gas scrubber - a Venturi scrubber, in which condensation of vapors and wet cleaning from small fractions of dust occur, in the gas scrubber they use industrial water circulating in a closed circuit and fed by a pump to the sprayers, contaminated water after the gas scrubber is sent to sewage treatment facilities, the purified gas component is removed from the gas scrubber, through a fan for heating the fat mass in the averaging tank, the fan also serves to create the required vacuum in the paddle-type drying apparatus system, the dried sludge with a moisture content of 5-10% and a temperature of 70-110°C is removed from the paddle-type drying apparatus through an opening arranged at its end and fed by an inclined screw conveyor into a big bag with a heat-resistant liner, then part of the dried loose sludge is fed into a container with a paddle mixer for mixing with fat mass, the remaining dried loose sludge can be sent to a screw conveyor and subjected to molding in the form of granules measuring 0.5 by 0.5 cm, the dried granulated or loose sludge can be used as a secondary material resource as a fuel, since in this case the presence of fat-containing sludge determines its high calorific value, or can be used as a raw material for further processing. 2. The method according to paragraph 1, characterized in that if industrial wastewater contains fats in a concentration of more than 300 mg/l, the wastewater is sent to grease traps, the separated fat mass is sent for processing into technical fat or biodiesel fuel, the wastewater with the remaining concentration of fats is sent to a pressure flotation tank into which reagents are introduced, the separated fat mass with a moisture content of 90-96% is sent to an equalizer with a mixing device and a first heating system up to 60-80°C, then sent to a tank with a second heating system up to 60-80°C, equipped with a mixing zone with a paddle mixer and a settling zone, a demulsifier solution is dosed into the mixing zone and mixed for 10-20 minutes, obtaining a homogeneous mass, in the settling zone for 20-30 minutes, additional separation of water from the fat mass occurs and a decrease in the moisture content of the fat mass to 85-92%, the separated water is sent to the head of the treatment plant, the fat mass, pre-treated with an emulsifier, is sent to vibrating screens, the separated fat mass, which is a finely dispersed emulsion, is treated with a demulsifier and sent to a disk separator, in which an effective separation of the phases occurs due to centrifugal force, after the disk separator, the fat mass with a moisture content of 88-90% is sent to a container with a paddle mixer, in which the fat mass is mixed with a portion of the dried sediment with a temperature of 70-110 ° C, removed from the paddle-type drying apparatus, for mixing with the hot dried sediment, then proceed according to paragraph 1. 3. The method according to paragraph 1, characterized in that, if acidifiers for raw sludge - active excess sludge - are present in the wastewater treatment technology, a reagent system for preparing a solution of lime or soda is introduced into the sludge preparation process flow chart, which is introduced into the raw sludge before dehydration to achieve a pH of 6.5 to 7.5, the drying temperature is maintained at 75-90°C, and an alkaline scrubber is introduced into the gas purification process flow chart to capture _H2S and volatile acids.