CZ2022394A3 - A method of the waste sludge energy and material recovery using pyrolysis and an equipment to perform the method - Google Patents

Abstract

The subject of the invention is a method of energy and material recovery of waste substances and equipment (8) for carrying out this method, while the method of energy and material recovery of waste substances by pyrolysis in a pyrolysis unit (2) includes the preparation (100) of a raw material mixture (3) containing waste sludge (1) ), pyrolysis (101) of the raw material mixture (3) and subsequent collection (102) of the pyrolysis products (4) from the pyrolysis unit (2), whereby the preparation (101) of the raw material mixture (3) containing waste sludge (1) includes a treatment step ( 103) waste sludge (1), the step of treating (104) at least one energy raw material (7) and the subsequent step of mixing (105) the waste sludge (1) and the energy raw material (7), and that the pyrolysis products (4) taken from the pyrolysis unit (2) are used as fuel for the pyrolysis unit (2).

Description

Method of energy and material recovery of waste sludge by pyrolysis and equipment for carrying out this method

Field of technology

The invention relates to a method of energy and material recovery of waste sludge by pyrolysis, which solves the processing of waste sludge by thermal desorption in a pyrolytic device and at the same time dealing with pyrolysis products, and equipment for carrying out this method.

Current state of the art

Wastewater treatment sludges are concentrated waste products from sewage treatment plants that contain up to 90% water and especially high levels of toxic chemicals, heavy metals and pathogens including viruses, bacteria, etc. In the area of waste processing, dealing with them is very problematic, as their subsequent processing is limited by the limit values of these dangerous substances. Therefore, thermal treatment of waste sludge is most often used, which can eliminate part of the hazardous substances and at the same time use the waste sludge for energy.

Thermal treatment of waste sludge is carried out by conventional combustion or by thermolysis in pyrolysis retorts, which consists in thermal decomposition at high temperatures (up to 900 °C) and without air access. Pyrolysis products are pyrolysis liquid (pyrolysis oil), pyrolysis gas and solid residue (pyrolysis semi-coke). Due to the low calorific value of the waste sludge and high moisture content, the waste sludge is usually treated by drying and granulation before entering the retort and mixed with a suitable fuel, e.g. with coal, unusable coal, processed petroleum products or biomass.

In the current state of the art, methods of pyrolysis of waste sludge together with another waste substance are known. Document CN 111269729 A describes a method and device for the pyrolytic processing of waste sludge mixed with waste tires. Both raw materials are first suitably prepared, then mixed, chemically treated together and then dried. The proportion of particles from waste tires is 5 to 15% of the total weight of the solid part of the mixture, and the chemical modification of the mixture takes several days. The energy line is adapted only for the use of waste sludge and tires.

Document CN 211625265 U describes a method and system for the co-pyrolysis of sewage sludge and municipal waste, but the pyrolysis of both raw materials takes place separately in two pyrolysis units and only the flue gas treatment system is common. Another document CN 107325830 A also describes the joint pyrolysis of sewage sludge with municipal waste, but does not specify in any way the procedure for their co-pyrolysis or the equipment adapted for it.

The above-mentioned methods and equipment are adapted to the pyrolysis of waste sludge with only one specific type of other energy raw material, and their disadvantage is that they do not also use a range of other waste products that can be used as fuel (biomass, used tires, waste plastics, sorted municipal waste). The mentioned methods of co-pyrolysis of waste sludge are not variable according to the current availability of individual energy raw materials, i.e. for example, when there is a lack of waste tires, they do not allow pyrolysis to be carried out using waste plastics, they are very energy-intensive, and moreover, they do not fully utilize the energy potential of the pyrolysis products themselves.

The essence of the invention

The above-mentioned shortcomings are removed to a certain extent by the method of energy and material recovery of waste sludge by pyrolysis in a pyrolysis unit, which includes the preparation of raw material

- 1 CZ 2022 - 394 A3 mixture containing waste sludge, pyrolysis of the raw material mixture and subsequent collection of pyrolysis products from the pyrolysis unit, while the preparation of the raw material mixture containing waste sludge includes the step of treating the waste sludge, the step of treating the first and second energy raw materials and the subsequent mixing step sewage sludge and first and second energy raw materials, wherein the first energy raw material is processed petroleum products and the second energy raw material is biomass or coal, and that pyrolysis products taken from the pyrolysis unit including pyrolysis liquid and pyrolysis gas are used as fuel for the pyrolysis unit.

The advantage of the combined use of waste sludge in a mixture with other energy raw materials is the great variability in the composition of the raw material mixture intended for pyrolysis, while the pyrolytic processing of such a raw material mixture results in a higher efficiency of pyrolysis and the quality of pyrolysis products than when processing waste sludge separately. The advantage of this method is the energy utilization of pyrolysis products for heating the pyrolytic unit, while the consumption of externally supplied energy is reduced and a better energy balance of the entire system is achieved. This method of evaluating waste sludge is a variable and effective solution, especially for small pyrolysis units.

The method of energy and material recovery of waste sludge by pyrolysis preferably includes the use of pyrolysis liquid and pyrolysis gas as fuel for the pyrolysis unit. The advantage of this method is the consumption of the majority of energy-usable pyrolysis products directly at the place of their production, which contributes to the energy self-sufficiency of the process and reduces the requirements for further storage or processing of pyrolysis products.

Energy raw material in the form of processed petroleum products or biomass is advantageously used for the method of energy and material recovery of waste sludge by pyrolysis. The advantage of this method is the possibility of disposal of a number of waste substances and at the same time their energy use, as they have a higher calorific value than waste sludge and fulfill the function of fuel.

The preparation of a raw material mixture containing waste sludge advantageously includes the step of treating the first and second energy raw materials, whereby the first energy raw material is processed petroleum products and the second energy raw material is biomass or coal, especially coal that cannot be used for energy. The mentioned method of waste sludge recovery enables the combined use of several different energy raw materials and, at the same time, the optimization of the properties of the raw material mixture.

The step of treating the waste sludge and the step of treating the energy feedstock preferably include physical or chemical processes leading to drying and comminution of the feedstock. The raw material processing methods mentioned can optimize the properties of the raw material mixture and the subsequent quality of the pyrolysis products.

The device for carrying out the method of energy and material recovery of waste sludge by pyrolysis includes a pyrolysis unit and a reservoir of pyrolysis products, while the pyrolysis unit includes a retort, a dosing device for feeding the raw material mixture into the retort, and a heating element adapted to heat the retort, while the device further includes a preparation line for the treatment of waste sludge and treatment of the first and second energy raw materials, a mixing station adapted for mixing waste sludge and the first and second energy raw materials, and further connecting pipelines, while the preparation line for waste sludge and the first and second energy raw materials as well as the mixing station are upstream of the dosing device and the connecting pipeline connects the reservoir of pyrolysis products with the heating element of the pyrolysis unit.

The inclusion of a preparation line, a mixing station and a connecting pipe to the pyrolysis unit enables the assembly of a complex pyrolytic device for the processing of waste sludge by co-pyrolysis with one or more selected energy raw materials and at the same time a circular system with the direct use of pyrolysis products as fuel for heating the retort of the pyrolysis unit.

- 2 CZ 2022 - 394 A3

The reservoir of pyrolysis products in an advantageous embodiment includes a reservoir of pyrolysis liquid and a reservoir of pyrolysis gas, with a connecting pipe connecting the reservoir of pyrolysis liquid with the heating element of the pyrolysis unit and the reservoir of pyrolysis gas with the heating element of the pyrolysis unit. Between the retort and the reservoir of pyrolysis products, the device further includes a cooler adapted to cool the pyrolysis products, wherein the cooler is connected to the reservoir of pyrolysis liquid and to the reservoir of pyrolysis gas. Said arrangement with a cooler enables the condensation separation of captured pyrolysis products into pyrolysis liquid and pyrolysis gas, whereby the pyrolysis liquid, pyrolysis gas or both of these pyrolysis products can be used individually or together.

The mixing station preferably includes a screw mixer. The screw mixer can be placed directly next to the raw material preparation line as a vertical mixing station, which takes up less space.

Clarification of drawings

The essence of the invention is further clarified by examples of its realization, which are described using the attached drawings, where on:

Fig. 1 shows a block diagram of the individual steps of the method of energy and material evaluation of waste sludge according to the invention; and Fig. 2 shows a diagram of a device for performing the method of energy and material recovery of waste sludge by pyrolysis according to the invention.

Examples of implementation of the invention

The method of energy and material recovery of waste sludge 1 by pyrolysis and the device 8 for carrying out this method according to the invention will be further explained on examples of implementation with reference to the relevant drawings. One example of implementation is the method of processing waste sludge 1 simultaneously with another waste energy raw material 5, which is shown schematically in Fig. 1, and using the device 8 shown in Fig. 2.

The method of energy and material recovery of waste sludge 1 consists in optimizing the composition of the raw material mixture 3 entering the pyrolysis unit 2, whereby the raw material mixture 3 includes waste sludge 1 and at least one other energy raw material 5. Energy raw material 5 means any processed, preferably secondary or waste raw material that can be used as fuel in the co-pyrolysis of waste sludge 1. It is a raw material based on hydrocarbons from processed petroleum products, such as, for example, waste tires, waste plastics, sorted municipal waste based on plastics, etc., or based on biomass, whereby biomass any type of energetically usable biological material is meant, i.e. wood chips, wood pellets and briquettes, waste from plant production and others.

The raw material mixture preparation step 100 includes the waste sludge treatment step 103 and the energy raw material treatment step 104, which can take place in any order or independently of each other at the same time. Waste sludge 1 and energy raw materials 5 are separately treated in these steps by processes leading mainly to drying and comminution of the raw material, whereby the comminution of the raw material means adjusting the granulometry of the raw materials to a smaller particle size, e.g. by crushing or grinding. Other raw material treatment processes may include plasticization, chemical modification, granulation, and more. After the treatment 103 of the waste sludge and the treatment 104 of the energy raw material, the step of mixing 105 of the waste sludge and the energy raw material follows, when the treated waste sludge 1 and the treated energy raw material 5 are mixed into a homogeneous raw material mixture 3.

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The homogeneous raw material mixture 3 is subsequently processed by pyrolysis 101 of the raw material mixture in the pyrolysis unit 2, whereby the raw material mixture 3 is dosed at the inlet end 19 of the retort of the pyrolysis unit. The pyrolysis products 4 obtained by collecting 102 pyrolysis products from the pyrolysis unit 2 at the outlet end 21 of the retort include three main components: pyrolysis liquid 6 (pyrolysis oil), pyrolysis gas 7 and solid carbonaceous residue 20 (pyrolysis semi-coke), wherein pyrolysis liquid 6 and pyrolysis gas 7 are obtained from the flue gases withdrawn from the retort 10 and the solid carbonaceous residue 20 is removed through the valve at the outlet end 21 of the retort.

The method of energy and material recovery of waste sludge 1 includes the use of 106 pyrolysis products collected from the pyrolysis unit 2 in the actual pyrolysis process 101 of the raw material mixture. In the first exemplary embodiment, it is a pyrolysis liquid 6 and a pyrolysis gas 7, and these pyrolysis products 4 are used after cleaning together with natural gas as fuel for heating the retort 10 of the pyrolysis unit. The ratio of processed input substances (waste sludge 1, energy raw materials 5) and pyrolysis products 4 (pyrolysis liquid 6, pyrolysis gas 7) during the pyrolysis process is adapted to achieve the required energy balance of pyrolysis, while the goal is a positive or at least a balanced energy balance that does not require additional energy supply for pyrolysis. A negative energy balance during pyrolysis is also possible, but it consists only in the disposal of input raw materials and is loss-making from the point of view of convenience and economic return of device 8.

In the first exemplary embodiment, the device 8 for carrying out the method of energy and material recovery of waste sludge 1 by pyrolysis includes a total of 4 units: a preparation line 13 for treating input raw materials connected to a mixing station 14, a pyrolysis unit 2, an energy end for processing pyrolysis products 4 and a material end for deposition of the solid residue 20 of pyrolysis (pyrolysis semi-coke). The individual elements of the device 8, e.g. the preparation line 13 and the mixing station 14, the pyrolysis retort 10 with indirect heating and the cooler 18, or the cooler 18 and the container 9 for capturing the pyrolysis products 4, are connected by transport paths, whereby transport paths are understood as any continuous ways transport (pipes, screw conveyors, bucket conveyors, etc.) or periodic methods of transport (transport by wheeled vehicle). The arrangement of the elements of the device 8 is shown schematically in Fig. 2, while the transport paths are shown only schematically by the respective arrows.

The preparation line 13 includes all equipment for the physical and chemical treatment of waste sludge 1 and energy raw materials 5, which are separately treated by the methods mentioned above (these equipment are not shown in the figure). The preparation line 13 further includes reservoirs 22 of treated raw materials, i.e. waste sludge 1 and energy raw materials 5, while in the first exemplary embodiment one energy raw material 5 is in the form of waste plastic. Reservoirs 22 of processed raw materials are connected to a box feeder and mixing station 14, which includes a screw mixer. The screw mixer is followed by a conveyor and a storage container 24 for depositing the raw material mixture 3. From the storage container 24, the raw material mixture 3 is transported to the pyrolysis unit 2 using a wheeled vehicle.

The pyrolysis unit 2 includes a dosing device 11, a retort 10 with a screw driver and a heating element 12 adapted to heat the retort 10. The dosing device 11 includes a dosing reservoir and a hopper, the dosing reservoir and the hopper being located at the inlet end 19 of the retort and separated from each other by a slide valve , which is opened only when filling the hopper from the dosing reservoir, the hopper comprising a valve adapted to ventilate the contents of the hopper with an inert gas (N2) and exhaust air from the hopper by a vacuum connected to the valve. The pyrolysis unit 2 includes a heating element 12 in the form of four combined burners and deflectors adapted to direct the heat from the burners around the body of the retort 10. The fuel of the burners is natural gas, clean pyrolysis liquid 6 and clean pyrolysis gas 7. At the outlet end 21, the retort 10 includes an overflow hole with a ball valve for draining the solid residue 20 of pyrolysis.

The energy terminal includes a pipeline for the removal of pyrolysis products 4 in the form of flue gas from the retort 10 to the cooler 18, whereby the cooler 18 is adapted for cooling the flue gas, and therefore for separation

- 4 CZ 2022 - 394 A3 of pyrolysis products 4 by condensation into raw pyrolysis liquid 6 and raw pyrolysis gas 7. Raw pyrolysis liquid 6 is taken to the pyrolysis liquid intermediate tank 25, the filter device (calolis) (not shown in the diagram) and subsequently as pure pyrolysis liquid 6 to reservoir 16 of pyrolysis liquid. The reservoir 16 of the pyrolysis liquid is further connected by the connecting pipe 15 to the mixing row of the combined burners of the retort 10, while the pyrolysis liquid 6 is pumped by a gear pump. In case of sudden closing of the burner valve, the connecting pipe 15 includes a bypass (not shown in the diagram) by which the clean pyrolysis liquid 6 can be returned back to the reservoir 16 of the pyrolysis liquid. The pyrolysis gas 7 is drawn from the cooler 18 to the cleaning unit 26 and subsequently as pure pyrolysis gas 7 to the pyrolysis gas reservoir 17, while the pyrolysis gas reservoir 17 is, like the pyrolysis liquid reservoir 16, connected by a connecting pipe 15 to the mixing line of the combined burner.

The material end of the device includes, at the outlet end 21 of the retort 10, a solid residue removal system 23 comprising a water-cooled screw conveyor opening into a closed container, the closed container including an outlet to the screw conveyor and an open container. The open container is transportable to the solid residue processing point 20, which is located outside the entire facility 8.

In another embodiment of the method of energy and material recovery of waste sludge 1 in the mentioned device 8, it is possible to use several types of energy raw materials 5, e.g. 2 different energy raw materials 5, while in an advantageous embodiment the first energy raw material 5 is based on processed petroleum products and the second energy raw material 5 on the basis of biomass (e.g. processed wood matter), or coal that cannot be used energetically. The preparation line 13 in this embodiment includes the appropriate number of reservoirs 22 of treated raw materials, while waste sludge 1 and a combination of selected energy raw materials 5 can be used to prepare the raw material mixture 3 in the mixing station 14, or only one of the pair of energy raw materials 5 that is currently available .

In an alternative embodiment of the device 8 according to the invention, the heating element 12 and only the reservoir 16 of the pyrolysis liquid or only the reservoir 17 of the pyrolysis gas or, in general, the reservoir 9 of pyrolysis products including the raw mixture of pyrolysis products 4 can be connected by the connecting pipe 15.

Industrial applicability

The above-described method of energy and material recovery of waste sludge by pyrolysis and equipment for carrying out this method can also be used for co-pyrolytic processing of other raw materials or mixtures of raw materials.

Claims (5)

PATENT CLAIMS 1. Method of energy and material recovery of waste sludge (1) by pyrolysis in a pyrolysis unit (2), including preparation (100) of raw material mixture (3) containing waste sludge (1), pyrolysis (101) of raw material mixture (3) and subsequent collection (102) of pyrolysis products (4) from the pyrolysis unit (2), characterized in that the preparation (100) of the raw material mixture (3) containing the waste sludge (1) includes a treatment step (103) of the waste sludge (1), a treatment step (104) the first and second energy raw materials (5) and the subsequent step of mixing (105) the waste sludge (1) and the first and second energy raw materials (5), wherein the first energy raw material (5) is processed petroleum products and the second energy raw material (5 ) is biomass or coal, and that the pyrolysis products (4) taken from the pyrolysis unit (2), including pyrolysis liquid (6) and pyrolysis gas (7), are used as fuel for the pyrolysis unit (2). 2. The method of energy and material recovery of waste sludge (1) by pyrolysis according to claim 1, characterized in that the treatment step (103) of the waste sludge (1) and the treatment step (104) of the energy raw material (5) include physical or chemical processes leading to their drying and diminution. 3. Device (8) for carrying out the method of energy and material recovery of waste sludge (1) by pyrolysis according to claims 1 or 2, comprising a pyrolysis unit (2) and a reservoir (9) of pyrolysis products, wherein the pyrolysis unit (2) includes a retort (10) , a dosing device (11) for feeding the raw material mixture (3) into the retort (10) and a heating element (12) adapted to heat the retort (10), characterized in that it further includes a preparation line (13) for the treatment of waste sludge (1) ) and the treatment of the first and second energy raw materials (5), a mixing station (14), adapted for mixing waste sludge (1) and the first and second energy raw materials (5), and also the connecting pipe (15), while the preparation line (13) waste sludge (1) and the first and second energy raw materials (5) and the mixing station (14) are upstream of the dosing device (11), and the connecting pipe (15) connects the reservoir (9) of pyrolysis products with the heating element (12) of the pyrolysis unit. 4. Device (8) for carrying out the method of energy and material recovery of waste sludge (1) by pyrolysis according to claim 3, characterized in that the reservoir (9) of pyrolysis products includes a reservoir (16) of pyrolysis liquid and a reservoir (17) of pyrolysis gas, wherein the connecting pipe (15) connects the reservoir (16) of the pyrolysis liquid with the heating element (12) of the pyrolysis unit and the reservoir (17) of the pyrolysis gas with the heating element (12) of the pyrolysis unit, and that the device (8) between the retort (10) and the reservoir ( 9) of pyrolysis products includes a cooler (18) adapted for cooling pyrolysis products (4), wherein the cooler (18) is connected to a reservoir (16) of pyrolysis liquid and a reservoir (17) of pyrolysis gas. 5. Device (8) for carrying out the method of energy and material recovery of waste sludge (1) by pyrolysis according to claims 3 to 4, characterized in that the mixing station (14) includes a screw mixer.