RU2265773C2 - Method and device for burning solid waste - Google Patents

Abstract

FIELD: combustion.

SUBSTANCE: method comprises setting waste on the grate, supplying heat agent, burning waste, using heat of combustion, and purifying discharged gases. The layer of limestone is set under the waste to be burnt out. The limestone layer simultaneously heats absorber and sorbent of toxic components of the discharged gases and is converted into construction lime. The ratio of the thickness of the waste layer to that of the lime layer is 9:2.5. The heat agent flows through both of the layers from the side of the waste layer.

EFFECT: expanded functional capabilities.

2 cl, 2 dwg

Description

The invention relates to methods and devices for burning solid waste (MSW) with the preliminary separation of useful components from them for further processing. It can be most useful for the thermal destruction of municipal solid waste generated in large settlements.

The incineration of solid waste is associated with difficulties in neutralizing the toxic components of flue gases and in utilizing the generated heat. Incinerator filters are usually comparable in value to the furnace itself. The energy received in such furnaces does not compensate for the cost of burning solid waste. Subsidized expenses range from 50 USD per 1 ton of MSW (Moscow) to 80 USD per 1 ton of MSW (Germany). This is due to the fact that the capital cost of a heat recovery system is 3-5 times higher than the cost of furnace units.

The tendency to increase the combustion temperature to 1150 ° С and more allows to destroy dioxins and furans, but toxic oxides, although in smaller volumes, are still preserved. In this regard, the relevance of creating a combustion process, accompanied by sorption of toxic gases, is still maintained.

A device is known (US patent No. 5143000, F 23 G 05/00 from 01/09/1992), which allows you to implement a method of burning solid waste in a tank. The tank is filled with solid waste and a coolant from gas burners is supplied under their layer. The combustion products exit through an opening in the lid of the tank and are sent to the filters.

The disadvantage of this method is the need for complex and expensive filters, as well as the difficulty of ash removal from the tank.

A known method for producing fluxed agglomerate (SU 692875 A1, C 22 B 1/16, 10.25.79), including layer-by-layer placement on a grate of limestone and a pelletized mixture of coke and iron ore chips, ignition of a pelletized mixture, absorption of toxic components of combustion by limestone and partial thermochemical conversion limestone to lime.

The disadvantage of this method is only a partial conversion of limestone into lime and the need to return the unfinished limestone to the grate with the accompanying this process of incomplete neutralization of flue gases.

There is also known the prototype method of burning solid waste in the device (US patent No. 5265587, F 23 H 07/04 from 11/30/1993). The method includes laying solid waste with a layer on the grate, burning solid waste, using heat from burning at the thermal power station and cleaning the exhaust gases. The grate is given vibrations that contribute to the mixing of solid waste and thereby provide faster combustion.

The disadvantage of this method is its low productivity, low efficiency, the complexity of heat recovery of exhaust gases and the need for an expensive and multi-stage system for cleaning harmful impurities.

The main objective of the present invention is the provision of utilization of the bulk of the heat generated during the combustion of solid waste directly in the furnace unit with the conversion of limestone into building lime and the elimination of emissions of harmful components of the gas phase from the furnace unit.

Another objective is to simplify the mechanism for delivering solid waste to the furnace and the complete removal of combustion products.

The third task is to improve the quality and market value of combustion products (complete conversion of limestone to lime).

The solution to all these problems ensures self-sufficiency and even profitability of the process of thermal destruction of solid waste.

All the tasks are solved by the fact that in the method of burning solid household waste, including laying them in a layer on the grate, supplying a coolant, burning waste, using heat from burning and purifying the exhaust gases, in accordance with the present invention, they are laid on the grate for burning waste limestone layer in the form of crumbs of a fraction of 5-15 mm, which is both a heat sink and a sorbent of toxic components of the exhaust gases and is converted into building lime during combustion wearing layer thicknesses wastes and limestone is 9: 2.5, wherein the coolant is passed through both layers from the waste layer.

The method is as follows. A layer of limestone, which acts as a heat sink and a sorbent, is laid on a moving grate; it is then loaded with solid waste. With holes in the grate close to 4 mm, the particle size distribution of the limestone layer must be within the 5 + 15 mm fraction to ensure the necessary sorption efficiency. When the size of limestone is less than 5 mm, its particles fall through the grate, and when the size of limestone is more than 15 mm, its dissociation - heat absorption is inefficient. For a sufficiently complete cleaning of the exhaust gases, the ratio of the thickness of the MSW and limestone layers should be 9: 2.5. Then limestone cleans the gases well and absorbs maximum heat. If the limestone layer is made thinner than claimed, the temperature of the exhaust gases will increase, which will lead to the burning of the grate. If its layer is increased more than claimed, then there will be a decrease in the performance of the unit for the incineration of solid waste. Thus, on the basis of an industrial experiment, the claimed particle size distribution and the ratio of the thickness of the layers are necessary and sufficient for the optimal solution of the problem.

To burn solid waste, various devices are used, the efficiency level of which is the efficiency and purity of gas emissions into the atmosphere. This is facilitated in the device by mechanisms that ensure the loosening and promotion of solid waste in the drying and burning zones.

As an analogue, the aforementioned US patent No. 5265587, F 23 H 07/04 of 11/30/1993, in which vibroprotectors are used that mix and transport burnt solid waste, can be adopted. The disadvantage of this device is the hard to remove slagging of the lattice and the need for expensive multi-stage filters.

A device (SU 692875 A1, C 22 B 1/16, 10.25.79), containing a grate, combustion chambers, heat recovery and gas purification, is accepted as an analogue.

A disadvantage of the known device is the incomplete conversion of limestone into lime and the incomplete neutralization of gases.

As a prototype, a device for burning solid waste-US 5265587 A, F 23 H 7/04, 30/11/1993 is used, containing a grate in the form of an endless conveyor for laying on it with layers of limestone and solid waste, a combustion chamber in which a part of the conveyor is placed , means of loading grates and chambers for cleaning and venting gases. The known device does not ensure the full implementation of the operations of the proposed method, in particular the complete conversion of limestone into lime, as well as the full purification of exhaust gases. In addition, the known device is notable for its complexity and high cost.

The objective of the claimed device is the creation of such a waste incinerator, which could be as simple and cheap as possible and easy to maintain, and environmentally friendly.

The problem is solved in that in the device for implementing the method of burning solid household waste, characterized in that it contains a movable grate, made in the form of an endless conveyor, one part of its loop placed inside the heat unit, means for separate loading on the grate of limestone and waste , the specified thermal unit includes nodes for separate drying of limestone and waste, coolant supply, combustion chambers and exhaust gas, flue gas afterburning units and recuperation heat recovery, in accordance with the invention, the gas removal chamber is divided into several zones, the last two of which are equipped with collectors for supplying gases for afterburning, final neutralization of toxic components and heat recovery.

The inventive device provides a method with increased efficiency with effective absorption of the toxic components of the flue gas by the sorbent and with the maximum simplification and cheapening of the technology.

Schematic diagram of the device shown in figure 1, and its structural diagram in figure 2.

The device (Fig. 1) contains an endless conveyor 1 with a grate bottom 2, a limestone loading unit 3 and a solid waste loading unit 4 onto the conveyor 1. A part of the conveyor loop is located inside the thermal unit 5, and an unloading unit 6 of the conveyor 1 is located at the outlet of it. thermal unit 5 is supplied with air and natural gas.

The structural diagram (figure 2) of the device shows an endless conveyor 1, a limestone hopper 2 with a feeder 3 and a solid waste hopper 4 with a feeder 5. A part of the conveyor 1 loop is located inside the heat generating unit 6, which includes a limestone drying unit 7, a solid waste drying unit 8, a chamber 9 heating the MSW prior to ignition, the MSW combustion chamber 10 and the limestone cooling chamber 11.

In the sub-conveyor zone, guide tanks 17 are located for the temperature distribution of the exhaust gases through the exhauster 18 to the consumer for utilization of their thermal energy and additional cleaning through the cyclone 15 and filter 16.

The calcined limestone is carried out by the conveyor 1 to the unloading device 12 and further to the screen 13 and the conveyor 14.

The method using the device works as follows. Limestone is fed from the hopper 2 to the endless conveyor 1 (FIG. 2), which is laid in even layer with the help of feeder 3 on the grate of the conveyor. Passing over node 7, the limestone is dried. From the hopper 4 on the surface of the limestone feeder 5 is loaded with solid waste so that the ratio of the thickness of the layers of solid waste and limestone was 9: 2.5. The loaded conveyor feeds the material to the thermal unit 5, where the solid waste in the zone of the node 8 is dried, and under the node 9 it is ignited and burns under the node 10. In the chamber 11, the limestone and ash are cooled and fed to the unloading device 12 and then to the screen 13 for classifying the calcined limestone (lime). Then it is conveyor 14 is fed into the storage bins. Flue gases through the distribution tanks 17 and the exhauster 18 are sent to heat the boilers, then partially returned for heat recovery to the head of the heat generator 5, and the other part is sent through the cyclone 15 and filters 16 to the chimney.

Thus, the proposed method and device, in accordance with the distinguishing features, is significantly simpler than traditional units and does not require expensive and complex filters for flue gas purification, and at the process outlet, commodity lime is obtained that provides profit from a traditionally expensive process.

Claims (2)

1. A method of burning solid household waste, including laying them in a layer on the grate, supplying coolant, burning waste, using heat from combustion and purifying the exhaust gases, characterized in that a layer of limestone is placed in the form of crumbs of fraction 5- under the waste on the grate; 15 mm, which is both a heat sink and a sorbent of toxic components of the exhaust gases and is converted into building lime during combustion, the ratio of the thicknesses of the layers of waste and limestone is 9: 2.5, with this coolant is passed through both layers from the side of the waste layer. 2. A device for implementing the method of burning solid household waste according to claim 1, characterized in that it contains a movable grate, made in the form of an endless conveyor, one part of its loop placed inside the heat unit, means for separate loading on the grate of limestone and waste, the specified heat unit includes nodes for separate drying of limestone and waste, coolant supply, a combustion chamber and exhaust gases, nodes for the afterburning of exhaust gases and heat recovery, while the chamber The gas ode is divided into several zones, the last two of which are equipped with collectors for supplying gases for afterburning, the final neutralization of toxic components and heat recovery.

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