RU2477819C2 - Rotor furnace for pyrolysis of solid domestic wastes - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: rotor furnace for pyrolysis of solid domestic wastes refers to utilisation and processing of solid domestic, industrial, medical and other wastes, their deactivation and secondary use of processing products. Rotor furnace includes a hollow lined cylindrical housing, a cylindrical waste pyrolysis chamber installed coaxially to the housing so that an annular gap is provided between them, drive for its rotation, a process fuel combustion assembly with burners, a furnace waste supply device, removal connection pipes of synthesis gas, fuel combustion products formed during processing of wastes, and outlet connection pipes of solid waste processing residues. Waste pyrolysis chamber is equipped with an independent rotation drive in the direction opposite to the furnace housing rotation. On external surface of the pyrolysis chamber there mounted are blades located along a screw line curling in the direction opposite to the rotation direction of the above chamber. Fuel combustion burners are mounted in circular axis of the annular gap.

EFFECT: improving continuous waste processing productivity.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of disposal and processing of solid household waste (MSW), their disposal and recycling of processed products, more specifically, to devices for waste disposal by thermochemical pyrolysis.

In addition to municipal solid waste, recyclable materials may include medical, industrial and industrial waste, including plastics, paints, rags, sawdust, etc .; city sewage treatment plants waste and other materials.

Known container devices for the pyrolysis of solid household and medical waste developed by many foreign and domestic companies - ATI INCINERATEURS MULLER (France), CJSC TURMALIN (Russia), LLC In-Tech-Synthesis (Russia) and others [1-2]. Installations called incinerators usually consist of a pyrolytic solid waste chamber, a pyrolysis synthesis gas afterburner, a fan for supplying air to the burners, an exhaust gas treatment system, a recuperator for utilizing the generated heat, a tank for liquid diesel fuel, and a process control system MSW, etc.

The disadvantages of container devices for waste pyrolysis are the frequency of the process, low productivity (from 5 to 100 kg / h), the high complexity of loading and unloading, the need to use expensive diesel fuel for the pyrolysis process, etc.

Also known is a container device for the pyrolysis of municipal solid waste [3], not sensitive to heating by microwave radiation. The device is a reactor equipped with a microwave generator for receiving microwave radiation. The pyrolysis chamber is located in the reactor. Before the solid waste pyrolysis, a powdery material containing carbon is placed at the bottom of the pyrolysis chamber, after which waste is loaded onto the powder layer.

After turning on the generator, the powdery material is heated by induction currents to a temperature of about 400 ° C. At the same time, the waste products ignite and the process of pyrolysis begins, which develops due to exothermic reactions and additional heat of the red-hot layer of powder material. The device has disadvantages similar to the aforementioned incinerators.

Known rotary (rotary) gas furnaces for the disposal and smelting of metal waste, pig-iron and steel shavings [4]. The rotary kiln is a lined cylindrical body. Burners are mounted on one end, on the other - a device for loading metal waste and a pipe for the output of combustion products. Remelting of metal waste is carried out under a layer of protective slag melt. A disadvantage of the known furnace is the low productivity and complexity of the process.

Known rotary kiln used in pyrolysis incinerators of the company ATI INCINERATEURS MULLER (France) with a productivity of 600-3000 kg / h [5]. The rotary kiln contains a hollow lined cylindrical body, a drive for rotating it, a fuel combustion unit with burners, a device for supplying waste to the furnace, a branch pipe for removing the products of combustion of fuel, a branch pipe for removing the synthesis gas generated during the processing of waste, and a branch pipe for issuing waste processing residues. The thermal power of the furnace is in the range of 2500-12000 kW / h.

A rotary kiln provides complete waste incineration, neutralization of all types of infected waste at a temperature of 1100-1200 ° C. The productivity of the furnace is ten times higher than the productivity of container incinerators. This ensures the continuity of the processing of solid waste.

The rotary kiln serves for the complete combustion of the processed waste, for which a burner is used, which is installed at the place where the waste is fed into the kiln. The furnace, unlike the container method, is not equipped with a pyrolysis chamber, where without the access of oxygen from the air, the pyrolysis of waste and the decomposition of harmful substances into harmless components would be carried out, which is a drawback of the design of the rotary kiln and the installation as a whole, since the burning of waste does not give an effective destruction result according to the following reasons:

- harmful and hazardous substances do not decompose, do not decompose into less hazardous substances, but pass into the gaseous phase;

- when burning waste, new harmful compounds can form, for example, dioxins, furans and others;

- waste combustion products, as a rule, are non-combustible, and therefore cannot be used as alternative fuel.

The closest in technical essence is a rotary kiln according to the patent for utility model RU No. 75711 U1 "Technological scheme of the installation for thermal neutralization of industrial oil-containing and solid household waste" [6]. The known rotary kiln contains a hollow rotating cylindrical drum (lined housing) and a cylindrical retort coaxially mounted inside the housing (waste pyrolysis chamber). The furnace body and the pyrolysis chamber are rigidly interconnected. An annular gap is formed between the body and the pyrolysis chamber. The furnace is inclined to the horizon and contains a drive for rotating the housing, a syngas combustion unit, a device for supplying waste to the furnace, pipes for the discharge of the resulting synthesis gas, combustion products of the process fuel and the delivery of processed products. The technological fuel of the furnace is the synthesis gas generated during the pyrolysis of solid waste.

The waste recycling process in the known furnace is as follows. Shredded waste is fed into the pyrolysis chamber by a screw. On the other hand, in the annular gap between the pyrolysis chamber and the lining of the casing, combustion products of synthesis gas with a temperature of 1100-1200 ° C are fed, which heat the walls of the pyrolysis chamber to a temperature of 500-550 ° C. At this temperature, the pyrolysis of waste is carried out in the chamber.

At the end of the pyrolysis chamber, the products of processing and synthesis gas are dispensed, which are sent for afterburning and purification. The products of combustion of the synthesis gas after afterburning are sent to the annular gap for heating the furnace and the pyrolysis chamber. The introduction of combustion products into the aforementioned annular gap is carried out through a pipe in the upper part of the side surface of the cylindrical body. The waste recycling process takes place in the counterflow of waste and combustion products of synthesis gas in the axial direction.

A significant disadvantage of the known furnace is the irrational arrangement of the pipe for introducing combustion products into the furnace. Firstly, due to the upper one-sided arrangement of the gas supply pipe, uniform heating of the entire surface of the furnace lining and the pyrolysis chamber along their length and cross section is not ensured; secondly, the location of the pipe on the side surface of the rotating housing is irrational and violates the sealing of the housing. The temperature of the furnace lining is not evenly distributed along the length; there are areas in the furnace where the temperature will be lower than the pyrolysis onset temperature of individual components of the waste, which will lead to the fact that some of the waste will not be involved in the process of thermochemical treatment. The maximum temperature in the furnace will be observed in the upper part of the body, which can lead to burnout of the lining. Ultimately, the described circumstances lead to a decrease in the rate of heating of the waste in the pyrolysis chamber, the speed of their thermochemical treatment, and a decrease in the productivity of the furnace.

In addition, the rotation of the furnace body and the pyrolysis chamber in one direction and at the same speed leads to the fact that the processed waste and hot combustion products of the process fuel in the cross section move relative to each other in the same direction. The nature of the movement of combustion products along the furnace is laminar. The noted features do not contribute to the intensification of waste heating and the process of their pyrolysis. As is known, heat transfer processes most intensively take place in the countercurrent of reacting phases with the turbulent nature of their mutual movement.

Among the disadvantages, it can also be noted that the pyrolysis temperature of 500-550 ° C for some types of waste, such as infected medical waste, is insufficient for their safe disposal.

The present invention is directed to the development of such a design of a rotary kiln, which would provide high-temperature and high-speed pyrolysis with deep destruction of recyclable waste at a higher process productivity and high environmental safety of waste disposal.

The problem is solved in that in a rotary kiln for the pyrolysis of municipal solid waste containing a hollow lined cylindrical body, a cylindrical waste pyrolysis chamber mounted coaxially with the body with an annular gap between them; a drive for rotating the housing, a unit for burning process fuel with burners, a device for feeding waste to the furnace, branch pipes for the discharge of synthesis gas generated during the processing of waste products, fuel combustion products and the delivery of solid residues from waste processing, the pyrolysis chamber is equipped with an independent rotation drive in the opposite direction to rotation the furnace body, while on the outer surface of the pyrolysis chamber mounted blades located along a helical line winding in a direction opposite to the direction of rotation of the mentioned removed chamber, and the burner for burning fuel mounted on the average diameter of the annular gap between the pyrolysis chamber and the furnace body. In addition, the pyrolysis chamber and the furnace body are made with diameters calculated on the basis of the ratio of the outer diameter of the pyrolysis chamber d _kp and the inner diameter of the lining of the body d _f equal to d _kp : d _f = 0.3 ... 0.5.

The proposed rotary kiln for the pyrolysis of municipal solid waste is illustrated by drawings. Figure 1 shows a rotary kiln in longitudinal and transverse sections. Figure 2 presents the temperature distribution along the length of the furnace. Figure 3 shows the technological scheme of processing municipal solid waste.

The rotary kiln consists of a hollow cylindrical casing 1, the inner part of which is lined with refractory brick 2. On the outer surface of the casing, gears 3 are mounted for engagement with the drive wheel 4. A device 6 is installed on the left end of the furnace for continuous waste feeding into the furnace with a screw 7. Here, a nozzle 8 for removing the combustion products of the process fuel and a nozzle 9 for removing the synthesis gas generated during processing are mounted. At the right end of the furnace is mounted a unit 10 for burning process fuel with burners 11.

In the cavity of the lined housing 1 of the furnace, a rotating sealed pyrolysis chamber 12 is mounted coaxially with it. The pyrolysis chamber 12 has its own autonomous rotation drive 13, wherein the rotation of the pyrolysis chamber is arranged in the opposite direction to the rotation of the furnace body. Between the surface of the lining of the housing and the outer surface of the pyrolysis chamber there is an annular gap 14 for the passage of combustion products along the entire furnace.

Blades 15 are mounted on the outer surface of the pyrolysis chamber, arranged along a helical line winding in the direction opposite to the direction of rotation of the pyrolysis chamber. The blades serve for swirling and turbulizing the combustion products of the process fuel in order to intensify heat transfer.

The waste is supplied to the left side of the pyrolysis chamber. At the right end of the pyrolysis chamber, a pipe 16 for the delivery of solid processed products is installed.

The outer diameter of the pyrolysis chamber d _kp and the inner diameter of the lining of the furnace body d _{f are} calculated based on the ratio d _kp : d _f = 0.3 ... 0.5.

The pyrolysis chamber is made of heat-resistant anticorrosive steel, for example 18XH10T, 23XH10T, etc. It is possible to manufacture a pyrolysis chamber from malleable or high-strength cast iron.

The technological fuel of the furnace is natural gas, synthesis gas, a mixture of natural gas and synthesis gas, fuel oil, coke oven gas, etc.

The proposed rotary kiln for the pyrolysis of municipal solid waste is as follows. Kindle gas burners and gradually warm the lining of the furnace to a temperature of 1000-1200 ° C. In this case, the furnace body and the pyrolysis chamber are rotated in opposite directions. The rotation speed is in the range of 10-60 rpm. The rotation of the furnace body ensures uniform heating of the lining, and the rotation of the pyrolysis chamber, in addition, ensures the transportation of waste along its axis.

The gas is burned with an air flow coefficient of 0.6-1.00. At a coefficient of <1.00, the products of gas combustion are less oxidative, which increases the resistance of the walls of the pyrolysis chamber.

The temperature of the combustion products at the outlet of the burners is 1350-1450 ° C, the temperature of the walls of the pyrolysis chamber is up to 900 ° C. The approximate temperature distribution in the annular gap of the furnace and in the pyrolysis chamber by zones is shown in Fig.2.

After setting the optimal conditions and achieving stable operation of the burners, they start loading waste into the pyrolysis chamber using a screw device. The download speed is regulated during the pyrolysis process. The atmosphere in the pyrolysis chamber is neutral, the pressure is atmospheric. In zone I of the pyrolysis chamber, the waste is heated to a temperature of about 200 ° C and moisture is removed. In zone II, at a temperature of 300-400 ° C, thermochemical decomposition reactions begin to develop.

The decomposition reactions are exothermic, the heat of these reactions is spent on the development of the pyrolysis process and temperature increase.

In zone III of the pyrolysis chamber at a temperature of 800-900 ° C, pyrolysis has the highest speed and stability. By the end of the third zone, the entire volume of waste is being destroyed. Solid residues in zone IV are cooled and discharged through pipe 16.

In the process of pyrolysis, synthesis gas is released, which is removed through the pipe 9 and sent either to the heating system of the rotary kiln, or for use in other thermal units as fuel.

The combustion products of the process fuel are removed through the pipe 8, burned with heat recovery and are discharged into the atmosphere.

Compared with the prototype, the proposed design of the rotary kiln contains the following new structural elements, which are essential signs of novelty:

- the rotation of the pyrolysis chamber is carried out in the direction opposite to the rotation of the furnace body. This novelty element makes it possible to intensify the process of heat transfer from the lining of the housing to the surface of the pyrolysis chamber due to the opposite rotation of the heat transfer and heat transfer surfaces;

- the pyrolysis chamber is equipped with an autonomous rotation drive, which ensures the independence of the rotation of the chamber from the rotation of the housing and the ability to control the speed of rotation of the pyrolysis chamber depending on the conditions of the pyrolysis process;

- the outer surface of the pyrolysis chamber is equipped with blades that contribute to the turbulence and turbulization of the flow of fuel combustion products, which ensures the intensification of heat transfer processes;

- the blades are mounted on a helix, which allows you to swirl the flow of combustion products and more evenly disperse the hot gases over the cross section of the furnace;

- the direction of the helical line along which the blades are mounted is set in the opposite direction of rotation of the pyrolysis chamber, which provides a counterflow of the chamber surface and hot gases and acceleration of heat transfer between them;

- fuel burners are mounted along the axial circumference of the average diameter of the annular gap, which ensures uniform distribution of heat flux over the furnace cross section and uniform heating of all heat-absorbing surfaces without local overheating and burnout;

- the pyrolysis chamber and the lining of the furnace body are made with diameters calculated on the basis of the ratio d _KP : d _f = 0.3 ... 0.5.

The indicated ratio is optimal, as this creates favorable conditions for the sustainable and efficient burning of process fuel, as well as for ensuring a high heat transfer coefficient from hot gases and a hot lining to the surface of the pyrolysis chamber. With this ratio less than 0.3, the heat transfer conditions are violated, the surface temperature of the pyrolysis chamber decreases, the productivity of the pyrolysis waste processing decreases. With a ratio of more than 0.5, the width of the annular gap decreases, the surface temperature of the pyrolysis chamber increases sharply, which will lead to burnout of the housing and depressurization of the chamber.

The proposed rotary kiln for the pyrolysis of municipal solid waste can be used as the main unit in the technological chain of the installation for waste disposal (figure 3).

The present invention provides the following positive effect:

- increased productivity of pyrolysis in a rotary kiln. High productivity is determined by the following factors: an increase in the heating rate of the walls of the pyrolysis chamber and, accordingly, of the processed waste; high temperature in the pyrolysis chamber (up to 800-900 ° C); an increase in the rate of thermochemical pyrolysis reactions; intensification of heat transfer processes in the furnace. The increase in the heating rate of the walls of the pyrolysis chamber and waste is ensured by the fact that heat is transferred by all types of heat transfer - convection from hot products of fuel combustion, radiation from a hot lining and thermal conductivity upon contact of hot gases and waste with the surface of the chamber. The increase in the heating rate is facilitated by the rotation of the pyrolysis chamber, the constant mixing of waste and the presence of blades on the surface of the pyrolysis chamber. The blades swirl the flow of combustion products and turbulize it, which intensifies heat transfer processes. The increase in the heating rate is also facilitated by the uniform distribution of heat over the furnace cross section and the absence of zones with a reduced temperature, achieved by a uniform arrangement of the burners along the axial circumference of the annular gap. Organization of countercurrent movement of waste and hot combustion products, rotation of the furnace body and the pyrolysis chamber in opposite directions, as well as swirling the flow of combustion products in the direction opposite to the rotation of the pyrolysis chamber, provide intensification of heat transfer processes and an increase in the heating rate. Due to the high temperature in the pyrolysis chamber, the rate of thermochemical reactions increases, which contributes to an increase in the productivity of the rotary kiln. In aggregate, the described design features of the rotary kiln are significant and provide an increase in unit productivity by 5-7% compared to the prototype and by 20-30% compared to the containerized pyrolysis method of waste processing due to the continuity of the pyrolysis process in the rotary kiln. The specific productivity of the rotary kiln also increases to 3-4 tons per 1 m ^{2 of} furnace section per hour.

High productivity of the rotary kiln is also ensured by the optimal ratio of the outer diameter of the pyrolysis chamber and the inner diameter of the lining of the furnace body, equal to 0.3 ... 0.5, which allows for a high coefficient of heat transfer from hot gases and the lining to the surface of the pyrolysis chamber and, therefore, high performance;

- increasing the degree of waste processing due to the organization of high-temperature pyrolysis of waste and the intensification of thermochemical processes throughout the volume of waste along the entire length of the pyrolysis chamber. The degree of processing of solid waste reaches 95-98%;

- improving the environmental safety of air emissions, achieved through deep high-temperature and high-speed pyrolysis of waste and the subsequent afterburning of exhaust gases. As a result of this waste treatment, toxic substances are degraded into less or completely safe compounds, and the high speed of the process prevents the formation of dioxins and furans;

- technical and economic efficiency and cost recovery of solid waste processing through the use of processed products as sources of heat and other energy, building materials, chemicals, etc.

The table shows the estimated comparative technical indicators of the proposed rotary kiln and furnace, taken as a prototype.

No. p / p Indicator Units ism Prototype The proposed image. one Oven temperature ° C 1100-1200 1350-1450 2 Pyrolysis temperature ° C 500-550 800-900 3 Specific produces. t / m ² 2.5-3.0 3.0-4.0 four The nature of the movement. gas - Laminar Turbulent 5 Heat transfer coefficient rel. units 1,0 1.2-1.3 6 Degree of processing % 90-95 95-98

Thus, the present invention provides a high-performance pyrolysis processing of municipal solid waste with a continuous process, minimal labor costs for loading and unloading, ensuring environmental safety and economic feasibility.

INFORMATION SOURCES

1. Vasyutina L.F., Popov A.A. Safety: infected medical and bioorganic wastes are the best methods for their thermal destruction. Conf. Materials "Fair of high-tech medical projects." Moscow, 2008, pp. 23-24.

2. Vostrikov M.M., Kofman D.I. Disposal of medical waste: sterilization or disposal? Materials of the conference "Fair of high-tech medical projects." Moscow, 2008, pp. 17-19.

3. RF patent No. 2080994 dated July 26, 1991 "Method for the pyrolysis of waste."

4. AS of the USSR No. 1616999 "Method for melting chips in a rotary kiln." Kl. C21C 1/08. Authors - Grachev V.A., Kirin E.M., Gorelov N.A., Morgunov V.N. Publ. BI No. 48 dated 12.30.90.

5. Pyrolysis incinerators for hazardous waste incineration model FRCD (rotary). ATI INCINERATEURS MULLER (France) - Distributor of ELVEKO GROUP (Russia). - M., 2008.

6. RF patent for utility model No. 75711 "Technological scheme of the installation for thermal neutralization of industrial oil-containing and solid household wastes." IPC F23G 5/14. Authors - Vyatkin A.V., Ermolaev V.V. et al. 08/20/2008.

Claims (2)

1. A rotary furnace for pyrolysis of municipal solid waste, containing a hollow lined cylindrical body, a cylindrical waste pyrolysis chamber, mounted coaxially with the body to provide an annular gap between them, a drive for rotating it, a process fuel combustion unit with burners, a device for supplying waste to the furnace , branch pipes for the discharge of synthesis gas generated by the processing of waste products, fuel combustion products and the issuance of solid residues of waste processing, characterized in that the waste pyrolysis chamber is equipped with genomic driven rotation in the direction opposite to the rotation of the furnace body, the blades are mounted on the outer surface of the pyrolysis chamber being disposed along a helix that winds in the opposite direction of rotation of said chamber, and a burner for burning fuel are mounted on the axial circumference of the annular gap. 2. A rotary kiln for the pyrolysis of municipal solid waste according to claim 1, characterized in that the pyrolysis chamber and the lining of the furnace body are made with diameters calculated based on the ratio of the outer diameter of the pyrolysis chamber d _CP to the inner diameter of the shell lining d _f equal to d _CP : d _f = 0.3 ... 0.5.

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