RU2061055C1 - Furnace for continuous melting of materials in melted slag - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: invention refers to equipment for processing of solid home and industrial waste in melted slag. Furnace for continuous melting has partition, fairing and zone after-burning of combustible products of home waste. Shaft is fitted with cyclone generator for effective burning of natural gas. Gas burners are positioned between partition on side of shaft loading unit and fairing and under it. Fairing is manufactured in the form of dog-house duct and is mounted for vertical movement. Front wall of furnace has window with gate to load briquetted mixture, face part of shaft has bevel towards hearth of furnace. EFFECT: improved functional efficiency. 3 cl, 3 dwg

Description

 The invention relates to metallurgical production, in particular to furnaces for processing slag in a liquid bath.

Known furnace for sulphide materials melting and slag depletion in a liquid bath, containing a shaft with charge loading units in its vault, tuyere system, gas duct, a partition fixed to the shaft vault [1]
The disadvantage of this design is that the partition has a limited function of dividing the gas space in the furnace to reduce dust removal, while the output section under the partition is regulated. These functions, as well as the dimensions of the bore, are clearly not enough for the conditions of processing solid domestic waste (MSW) that are toxic.

 Closest to the proposed is a device for continuous melting of materials in a melt [2] containing a shaft with loading nodes of the charge in its arch; a tuyere system, a gas duct fixed to the shaft of the shaft and a coffered septum and a siphon with outlet thresholds lowered into the melt, characterized in that the shaft is sealed and a partition in the form of a flow around at least three vertical distances from the slag siphon outlet to the fairing .

 The disadvantages of this design are: the burning of household waste in an airtight chamber under low pressure creates serious difficulties in the design and is fraught with its depressurization by emissions of harmful products (dioxins) of combustion into the atmosphere; the waste that fell into the common gas space in front of the fairing does not have time to practically dry out, as it is picked up by a torch and blown out under the fairing, which significantly reduces the time spent in the combustion zone, which leads to incomplete solid waste combustion; during the movement of gases under the cowl, which is immersed in the melt, uneven conditions arise for emissions of gases from the sealed chamber into the gas duct, which leads to transverse vibrations of the melt bath and subsequent even greater breakthroughs of gases into the gas duct, thus, an uneven course of the processing of solid waste occurs; it is impossible to use the cheapest type of fuel natural gas as a blow through conventional tuyeres, since the latter does not have time to burn in the bath volume, which leads to cooling of the slag melt in the furnace and the termination of the bubbling process.

 The aim of the invention is to increase the efficiency of the processing of solid household and industrial waste.

 The goal is achieved by the fact that the waste combustion zone located between the partitions is equipped with burner devices on the sides of the shaft, made in the form of cyclone generators with coffered tuyeres; the shaft of the mine, located above the melt at the neck of the gas duct and above the cyclone generators, is made in the form of a fairing.

 In order to effectively flush the gaseous products of waste combustion, the fairing is made in the form of a coffered duct installed in the archway between the side caissons of the mine with supporting screws, with the possibility of selecting the optimal distance from the siphon threshold to the lower plane of the fairing.

 The proposed device allows the most efficient burning of domestic and industrial waste in slag melt, using the cheapest type of fuel, natural gas.

 In this case, there is no need to build expensive oxygen stations and compressor stations.

Natural gas is burned in cyclone generators, which are installed on the sides of the furnace shaft, instead of tuyeres for supplying oxygen-containing blast. Natural gas combustion products with a temperature of 1200-1500 ^о С come from cyclone generators for bubbling a slag bath, burning solid waste and subsequent washing of waste combustion products.

 Significant differences of the proposed device are as follows.

 The ability to use cyclone generators to burn natural gas instead of supplying oxygen-containing fuel. So, instead of 40 tuyeres for supplying oxygen-containing blast, only 10 cyclone generators are installed in the combustion and flushing zones of the combustion products.

The solid waste burning zone is separated by a partition from the loading zone, which makes it possible to complete the drying process of solid waste. Drying of solid waste begins on the slopes of hopper feeders. With the sequential operation of the feeders according to the program, the drying time can be brought up to 10 minutes. Further, the waste flying through the drying chamber, fall into the loading part of the furnace and on the surface of the melt. Air heated up to 200 ^о С is supplied to the vault part of the bunkers in the amount necessary for the combustion of solid waste.

 Industrial waste: burnt earth, cast-iron shavings, fluxes are poured into one of the group of bins. The mixture is supplied with a given capacity continuously into the furnace with a plunger feeder.

 Steel chips in briquettes are fed with a pusher through a window located at the end of the furnace.

 To preheat briquettes and reduce damage to the hearth when feeding briquettes and small scrap into the bath, in the zone of their supply the hearth is made in a stepped form with a slope to the hearth.

The combustion of solid waste occurs in the middle of the furnace between the partition and the fairing. The MSW incineration zone above the melt surface creates an oxidizing atmosphere at a temperature ^of 1200-1400 C. In these conditions, the wastes are combusted efficiently in the spray and splashes of the melt. Further, the combustion products fall under a cowling, 2-6 m long. The latter is abundantly wetted by splashes and bursts of melt, and through this curtain, combustion products are sucked from the slag, freeing up most of the ash containing dioxins and furans.

 It is very important to set the fairing in height relative to the drain threshold. With a constant length of the fairing, it is possible to rinse the combustion products as much as possible by increasing the contact time of the slag curtain with passing gases. This can be achieved by increasing the distance from the threshold of the siphon to the fairing, however, an excessive increase in the distance will decrease the efficiency of washing with slag of the fairing and will reduce the degree of dust collection.

 Therefore, it is proposed to make a fairing in the form of a coffered box and install it with the possibility of height adjustment relative to the siphon drain threshold. In case of chef launches and trial melts, it is necessary to find the optimal position of the fairing ("know-how") for specific (average) household waste.

The final afterburning and thermal decomposition of solid waste products occurs in the throat of the mine, gas duct and dust chamber, where the temperature is maintained within the range of 1400-1200 ^о С. The length of this zone is more than 18 m, which fully complies with the European standards for toxic gases. The residence time of the combustion products in the afterburning and thermal decomposition zone should be at least 2 s. These requirements guarantee the absence of dioxin and furans in the products of combustion.

 In FIG. 1 shows the proposed device; in FIG. 2, section AA in FIG. 1; in FIG. 3 section BB in FIG. 1.

The device is made in the form of a furnace containing a hearth 1, a molten bath 2, lances 3 for supplying natural gas combustion products to the melt; cyclone generators 4; siphon 5 for draining slag, threshold 6 siphon 5; side caissons 7, arch 8, fairing 9, neck 10, gas duct 11, dust chamber 12, recuperator 13; a partition 14 separating the boot part 15 of the mine from the combustion zone, a briquette 16 of steel chips loaded into the bath 2 with a pusher 17. To seal the window 16 for briquettes, a gate 18 is provided. The latter is lifted using the drive 19. The loading window 20 for the charge is located in vault 8 of the furnace. A drying chamber 21 is installed above the loading window 20, to which air is heated in the recuperator 13 to 200 ^o C.

 Above the drying chamber 21, a group of hoppers 22 with plunger feeders 23 and covers 24 is installed.

 Plunger feeders make reciprocating movements from the drives 25. The bins 22 are connected by a vault 26. In the vault 26 a pipe 27 is installed for supplying heated air.

 One of the bins 22 is engaged in industrial, and the rest is intended for household waste (MSW).

 The distance from the fairing 9 to the threshold 6 of the siphon 5 is adjusted using the support screws 28. The box-shaped fairing 9 is coffered and has channels 29 for the cooling medium. The gaps along the contour between the fairing 9, the arch 8 and the side caissons 7 are sealed by the packing 30.

 On the side of the shaft of the furnace (Fig. 3) there is a chamber 31, which communicates with a channel 32 with a bath 2. In the chamber 31, a cooled seed 33 is suspended for the continuous formation of cast iron ingots.

 The process of processing solid waste and industrial waste (PO) in the slag melt is carried out as follows.

 The MSW is unloaded from the bins 22 with the help of plunger feeders 23, which operate according to a given program, averaging the MSW by composition and humidity.

 In order to increase the efficiency and stability of the waste processing process and to eliminate one-off emissions of harmful combustion products into the gas duct 11 of the MSW furnace, they are dried on the slopes with hot air and heat from the radiation of the roof. MSW, flying over the drying chamber, fall into the loading zone of the furnace and on the surface of the slag bath 2. In the loading zone of the furnace, a small vacuum of 5-10 mm water column is created.

 The MSW bins 22 have a height of at least 8 m. The MSW column height in the bunker 22 and the cover 24 prevent the emission of gases from the furnace shaft.

 Dried waste is carried away by hot air under the partition 14 and into the solid waste incineration zone.

In the combustion zone through lance 3 cyclone 4 generators fed natural gas combustion products, heated to 1200-1500 ° ^C to obtain a temperature ^of 1200-1500 C in the cyclone generator 4 is fed with preheated air t 200 ^o C. The composition of natural gas combustion products at α 1 wt. H 1.5; CO 1.5; CO ₂ 9.8; O ₂ 0.5; H ₂ O 18.7; N ₂ rest.

The combustion products of natural gas by bubbling the melt, burn MSW at 1400 ^C in an oxidizing atmosphere. Iron oxides are reduced by CO to cast iron. To obtain the desired melt viscosity, limestone is used as a flux when blowing.

 With lateral supply of blast in the bath, the processes of melting the mixture and reducing cast iron occur, similar to low semerization.

 Gases from the neck 10 of the furnace enter the gas duct 11 for thermal decomposition of the combustion products. Thanks to the supply of natural gas combustion products to the melt, it is possible: to compensate for all heat losses of the furnace; organize effective bubbling of slag melt and conduct solid waste combustion under effective heat and mass transfer; flush the waste products of solid waste from ash, dioxins and furans.

 Liquid cast iron accumulates at the bottom of the bath 2 and enters the heated chamber 31 through the channel 32.

 From the chamber 31, the cast iron is extracted in the form of cast iron ingots. A cast iron ingot (seed 33) is formed continuously by the method of freezing.

 An example of a specific implementation is the installation of UPO-16-34M.

 In addition to solid waste, industrial waste is used as a charge: steel and cast-iron shavings, small scrap, burnt earth. It is planned to recycle other types of mass industrial waste. As fluxes limestone.

 The UPO-16-34M installation provides processing per hour: 16 tons of MSW; 12 tons of software; 6 tons of fluxes.

The hourly yield of solid products is: 16.5 tons of dense granular slag (γ 1.2 t / m ³ ); 6 tons of cast iron ingots.

 The unit is equipped with 10 cyclone generators (5 pcs. On each side).

The consumption of natural gas for a cyclone generator is 350 m ³ / h. The diameter of the lance is 150 mm.

The flue gases leaving the furnace have a temperature of ¹⁴⁰⁰ ° C and do not contain dioxins and furans. Dust removal from the furnace 0.5-0.8% The latter after electrostatic precipitators can be returned to the furnace.

Claims (3)

 1. Furnace for continuous melting of material in a slag melt, containing a coffered shaft, partitions mounted on its arch, dividing the shaft into chambers, a charge loading unit, a tuyere system located in the side walls of the shaft, a gas duct with a neck, a siphon with an outlet threshold and a notch, characterized in that it is equipped with connected with tuyeres made by coffered gas burner devices in the form of cyclone generators for burning natural gas, while the partition located on the side of the gas duct is made in the form of tekatelya and gas burner units are located between the partition from the loading unit charge and fairing, and under it.  2. The furnace according to claim 1, characterized in that the fairing is located in the archway between the side caissons of the shaft and is made in the form of a coffered box mounted on supporting screws with the possibility of its vertical movement.  3. The furnace according to claim 1, characterized in that in the front end wall of the furnace there is a window with a gate for loading the briquetted charge, while the end part of the shaft in the briquette feed zone is sloped to the hearth of the furnace.

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