RU2494985C1 - Method of producing road construction composite materials based on treated sewage sludge from public utilities - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in road construction, in production of fertiliser for roadside landscaping, forestry, reclamation of solid domestic and industrial waste landfills and for biological reclamation of disturbed lands. The method is realised by successive collection of sewage sludge with dilution thereof to working concentration of 5% in a sludge preparation unit. Agents for binding heavy metal ions, disinfection and elimination of foul smells are added to the prepared suspension. A dehydrating flocculant solution is prepared. Areas and equipment for drying the prepared sludge are prepared. The treated sludge is mixed with the flocculant solution and the obtained mixture is put into sacks made from geotextile material. The mixture is held in the sacks until a sludge is obtained, which is dried to a state of 25-28% dry substance. The obtained sludge is mixed with sand and ash, wherein before mixing with the flocculant, the sludge goes through a cavitation mixer.

EFFECT: method provides efficient recycling of a considerable volume of sewage sludge from public utilities to obtain composite materials used for different purposes.

Description

The invention relates to the field of sewage sludge processing for utilities and can be used in road construction, as fertilizers for roadside gardening, afforestation, reclamation of solid domestic waste landfills and industrial waste landfills, for biological reclamation of disturbed lands.

Known (copyright certificate SU 1778209) is a method for producing a mixture that can be used in road construction. According to a known method, crushed stone is used to dump waste water sludge, production waste by phosphating metal surfaces before painting and phosphate sludge.

The disadvantage of this method is that when it is used, components are used that represent the waste of small-tonnage production, the placement of which is not always adequate to the places of road construction. Such components must be available and delivered to the construction of the road in large volumes, which is associated with high material and technical costs.

Known (patent RU 2032319) is a method for producing artificial soil intended for growing plants. When implementing the method, zeolite and a gel-forming water-soluble non-toxic polymer are mixed as a moisture-absorbing material, a plant extract as a biologically active substance, Nostoc Zinckia blue-green algae as a nitrogen-fixing component, and sapropel.

A disadvantage of the known technical solution should recognize a fairly narrow scope.

Known (patent RU 2256632) is a method for producing autoclaved ash foam, which can be used for the manufacture of products in industrial and civil engineering. When implementing the method, cement, lime, sand and ash from burning sewage sludge, water and a foam-forming additive are mixed.

A disadvantage of the known technical solution is that for the manufacture of building products, it is necessary to form and process products in autoclaves. This process requires expensive equipment and high logistical costs for use in the manufacture of pavement.

During the patent information search, the sources of patent information were not revealed, which disclosed a method for producing composite materials for road transport construction based on recycled sewage sludge from public utilities.

The technical result obtained by the implementation of the developed technical solution consists in the utilization of a significant amount of sewage sludge from utilities with the production of composite materials that can be used in road construction, as fertilizers for roadside gardening, afforestation, and reclamation of solid household waste landfills and industrial waste landfills for biological reclamation of disturbed lands.

To obtain the indicated technical result, it is proposed to use the developed method for producing composite materials for road transport construction based on recycled sewage sludge from public utilities. According to the developed method, the sewage sludge suspension is sequentially taken from the utilities with its dilution to a working concentration in the preparation unit, the sludge suspension is added, the odor eliminating agent, the heavy metal ion binding agent and the disinfection agent are added to the prepared suspension, the flocculant solution is prepared to dehydrate the treated suspension sludge, prepare sites and bags of geotextile material for dehydration prepared slurry is mixed treated sludge suspension with flocculant solution, and put the mixture into bags of geotextile material is heated mixture in the bag of the geotextile material to obtain dewatered sludge and produce mixing the precipitate obtained with sand and ash, and the operating concentration slurry sludge is 5% by weight. on dry matter, the formed suspension of the precipitate is mixed with the Praestol flocculant solution, and before mixing with the polymer, the suspension passes through a cavitation mixer.

The developed method in the preferred embodiment is used as follows.

Initially, preparatory work is carried out, consisting of collecting a suspension of sediment and diluting the suspension of sediment to a working concentration.

The extraction (fence) of the suspension of sewage sludge is carried out from silt reservoirs using a mixing pump, which is connected using a reinforced flexible hose to a slurry pipeline. The pump preferably has two operating modes: pumping and mixing.

Before the start of each fence, the suspension of sediment is recommended to be mixed for 15-30 minutes. Two knives are installed on the suction nozzle of the pump for grinding large debris, often present in sewage sludge of public utilities.

After mixing, the sediment is fed into a pressure pipe made of polyethylene, through which a suspension of sediment enters the first receiving tank. An inline sensor for determining the dry matter (SV) content in the sediment is mounted in the pipeline. The sensor online measures the concentration of CB in the sediment suspension transported through the pipeline and, preferably, transmits them to a monitor located in the pump control room.

The suspension of sediment pumped from the sludge tank enters the first tank. The suspension taken from the sludge tank has a concentration of 7-12% according to SW. In the first tank, the suspension is diluted to a working concentration of 5% in SV. Dilution occurs by adding to the suspension water or a return filtrate flowing from geotextile bags. The filtrate is delivered from a sewage collector passing around the sludge storage landfill by a submersible pump with a capacity of 100 m ³ / h. Based on the readings of the inline sensor, the amount of dry matter in the incoming sludge suspension is determined and, accordingly, the volume of the filtrate required to dilute the initial sludge suspension to a 5% concentration by SW is determined. This amount of filtrate is added to the first tank and mixed with paddle mixers for approximately 30 minutes. In the process of mixing, the second inline sensor installed in the wall of tank No. 1 measures the concentration of the mixed suspension of sediment and transmits these readings to a monitor located in the pump control room.

After dilution of the suspension of sediment to a working 5% concentration according to ST, it is pumped into mixing tanks of the suspension of sediment with chemicals - the second and third tanks. Dosing of chemicals in the second and third tanks is carried out using plastic hoses DN8. The complex operates in automatic mode. The reagent supply signal comes from ultrasonic level gauges installed on the second and third tanks.

Pumps for pumping sludge suspension, screw type, have a capacity of 300 m ³ / h each.

The mixing process is as follows.

The following chemicals are added alternately from the chemical dosing complex to the second and third tanks: a means for eliminating unpleasant odors, a means for binding heavy metal ions, and a disinfectant.

Two tanks are necessary to ensure the continuity of the complex. Fill them in turn. When the suspension treated with the reagents is pumped further down the processing chain from the second tank, the process of mixing the chemicals with the suspension and vice versa takes place in the third tank. The process of dispensing chemicals and mixing them with a suspension takes about one hour.

The sludge suspension dewatering unit used consists of two sludge transfer pumps, a water supply pump, a dry substance detection sensor, piping from DN150 metal pipes and vibration dampers made of rubber of the same diameter.

To prepare the flocculant solution, a suspension system is used, consisting of a frame welded from four metal profiles, with hooks for hanging with a total weight of up to 1 ton and two units for preparing a highly concentrated flocculant solution with a concentration of 1-2%.

Each installation includes a 650-liter tank made of corrosion-resistant metal; two-level paddle mixer with electric drive; pump for collecting dry flocculant; a container for dosing a dry flocculant into a cooking tank equipped with a vibrator; bulk metering device (cell dispenser); flowmeter of water entering the dilution tank; pump for pumping the finished flocculant solution; intermediate tank with a capacity of 6 m ³ / h; piping from pipes and hoses DN50 with solenoid valves and pressure sensors and a control cabinet with a Siemens panel, with which control over all the parameters of preparation and dosing of flocculant solution.

The prepared flocculant solutions enter the intermediate (dosing) tank with a volume of 1400 l, made of corrosion-resistant metal, from which a flocculant solution is fed through a screw pump with a capacity of 9 m ³ / h through the unit for introducing the polymer solution into the processed sludge.

A flocculant solution is prepared as follows.

When the cooking unit is turned on, the dry flocculant is taken from the bag by a pump for bulk solids and, through polyethylene hoses equipped with a wire winding to relieve static stress, is fed into a dosing tank. The vibrator on the dosing tank prevents the flocculant from sticking to the walls and ensures uniform distribution of the flocculant inside the tank. At the same time, about a hundred liters of water are supplied to the V = 650 L tank using a pump. Thus, the dry flocculant after dosing begins to fall directly into the water, and not on the dry surface of the tank. Dosage of the dry flocculant is carried out using a cell dispenser driven by an electric motor. The speed of the cell dispenser is set automatically depending on the given concentration of the flocculant solution. The performance of the flocculant dosage unit is up to 30 kg of dry polymer per hour.

After preparation, the flocculant solution is pumped by a screw pump into the intermediate (dosing) tank V = 1400 l. from where a screw pump transfer pump is fed into the installation for mixing a flocculant solution with a suspension of sediment.

The CB content sensor installed in the pressure pipe with the suspension immediately after the sludge transfer pump sends a signal to the flocculant solution transfer pump. Depending on the decrease or increase in the concentration of CB in the suspension, the supply of the flocculant solution decreases or increases. Also, the volume of the supplied flocculant solution is regulated depending on the volume of the incoming suspension of sediment. To control this parameter, a flow meter is mounted in the pressure head pipeline with the suspension, which in turn sends a signal to the pump for transferring the flocculant solution into the mixing system of the prepared sludge suspension with the flocculant solution.

The mixing system is mounted in the pressure pipe for pumping sludge suspension and consists of two mixers. The first is a cavitation mixer designed to break up lumps in suspension and ensure uniformity of the mixture. The second mixer is a spatula with slots on the sides. Inside this scapula and serves a solution of flocculant. Leaving through the slots, the flocculant solution is wound on the suspension, as it were, while the best mixing, especially of highly concentrated solutions with the suspension, is achieved. The speed of rotation of the blades can vary from 300 to 3000 rpm. In the pipeline after the mixing blade of the flocculant with the suspension, a viewing window is installed through which the flocculation process, that is, the separation of the liquid and solid phases, can be visually monitored.

In the process of preparing static dehydration of the mixture, platforms and bags and geotextiles are preliminarily prepared. Bags are placed on specially prepared sites. In preparation, the site is covered with waterproofing material and covered with large gravel. The site is made under a slight slope towards the sewer. This is necessary to drain the filtrate from the bag.

After mixing with the flocculant, the suspension of the flocculated sludge is fed into geotextile bags through a pressure pipe made of 4 m metal pipes. Dimensions of the geotextile bag: length 65 m, height 2.5 m. Each bag has three holes for introducing sediment inside. To enter the suspension of the flocculated sludge into geotextile bags, pressure hoses are connected to the pressure pipe through the adapters, which are connected in turn to the holes for introducing the suspension inside. Geotextile bags are made using membrane technology, that is, they have one-sided conductivity. The filtrate formed during the flocculation process leaves the bag freely, and precipitation or any other liquid from the outside does not enter the bag.

Thus, as a result of static dehydration, only dehydrated sediment remains in the bag, which, under the influence of its own weight for 4-8 months after the last injection, is dehydrated to a state of 25-28% in NE (it looks like a little damp earth).

The filtrate released from the geotextile bags enters the sewage collector passing near all the concrete maps where the bags are located. Through the drainage well, the filtrate is taken into the first tank by a submersible pump and then used to dilute the suspension of sediment from the sludge tank. Thus, the secondary use of the recovered filtrate, i.e. a cyclical process is achieved.

The technology for producing composite materials provides for the removal of bio-sludge after opening the geotube with an excavator and placing it on a previously prepared site, usually a concrete map. At the same time, sand and ash are placed on adjacent sites.

After being in the geotube for at least one month, the processed primary raw materials (OPS), depending on the percentage of minerals, are ready for further processing.

Further processing of bio-sludge in the geotube depends on the results of chemical and microbiological analysis.

If the resulting product meets the requirements of GOST R 17.4.3.07-2001, then it is a fertilizer and can be used: without further processing and is called “GREENLIFE-P”.

If the product for some parameters does not meet the GOST requirements for soils, then to bring its parameters to these requirements, a sludge mixing system with various fillers-diluents located on the landfill is used: ash from sludge burning, sand from sand traps. The resulting composite material has the trade name “GREENLIFE-K” and can be used in road transport construction, as fertilizers for roadside gardening, afforestation, reclamation of solid domestic waste landfills and industrial waste landfills, for biological restoration of disturbed lands.

To obtain composite materials "GREENLIFE-K", it is preferable to use a three-chamber mobile installation on the chassis, equipped with a diesel installation for autonomous operation of the mixing unit.

The mixing unit is placed on a uniaxial chassis with a drawbar. The total length is about 13000 mm, width - 2750 mm, height 4000 mm. The total weight of 13,000 kg.

The unit consists of three bins. The first bunker with a loading volume of 10-12 m ^{3 is} designed to accommodate bio-sludge from geotubes. Main surface - 4000 mm × 1900 mm, loading hole - 4000 mm × 2200 mm, side walls - 1250 mm, one-sided removable side - 500 mm hinged, nozzle for the front wall - 500 mm inserted, base plate - 5 mm Hardox, side walls - 4 mm Hardox, scraper conveyor chain type 125 HV, scraper strips of the U-shape - 60 × 30 × 6 closed, loading height approximately 2800 mm, metering flap opening hydraulically - 800 mm Hub, metering flap walls 3 mm Hardox, bottom scraper conveyor drive above the spur gear th transmission, electro-service conveyor and metering valve.

The second hopper with a loading volume of 5.7-9 m ^{3 is} designed to load sand. Main surface - 3000 mm x 1900 mm, loading hole - 3000 mm × 1900 mm, side walls - 1000 mm, one-sided removable side - 500 mm reclining, front wall nozzle - 500 mm inserted base plate - 5 mm Hardox, side walls - 4 mm Hardox, scraper conveyor chain - type 125 HV, scraper conveyor strips U-shaped - 60 × 30 × 6 closed, loading height approx. - 3800 mm, metering flap that opens hydraulically - 800 mm Hub, metering flap walls - 3 mm Hardox, bottom scraper conveyor drive, mixing rollers with hydraulic drive and hardened cutters, electro-hydraulic maintenance for the scraper conveyor and metering shutter.

The third hopper has a loading volume of 2 m ³ and is designed to accommodate ash. After adding the initial volumes of the components to the mixing unit, the resulting product is fed by an internal conveyor to the disk screen: screen surface: width - 1200 mm, length - 3500 mm, total structure width - 2100 mm, total structure length - 4200 mm, number of shafts - 22, the distance between the blade knives is 25 mm, the rotational speed is approximately 250 rpm, the dump conveyor is a belt width of 980 mm, the drive motor power is 5.5 kW.

After passing through the screen, the finished product is fed by a working conveyor to an autonomous telescopic conveyor and placed on a specially prepared site or served for loading on the appropriate transport. Each batch of the product is analyzed according to the main quality indicators and a product passport is written out before shipment to the consumer.

Claims (1)

A method of producing composite materials for road transport construction based on recycled sewage sludge from utilities, characterized in that sewage sludge is collected sequentially with dilution to a working concentration in the sludge preparation unit, a means for eliminating unpleasant odors, a tool for binding heavy metal ions and a disinfectant, prepare a flocculant solution for dewatering the treated sludge, prepare sites and bags of geotextile material for dewatering the prepared sludge, mix the treated sludge with a solution of flocculant and place the mixture in bags of geotextile material, withstand the mixture in a bag of geotextile material until the sludge is dehydrated to a state of 25-28% by dry matter, the resulting precipitate is mixed with sand and ash, and the working concentration is 5 wt.% on dry matter, while before mixing with the flocculant sludge ok passes a cavitation mixer.