RU2287111C2 - Method of reworking solid domestic wastes in oxygen converter - Google Patents

Abstract

FIELD: thermal reworking of solid domestic wastes; ferrous metallurgy.

SUBSTANCE: proposed method includes incineration of solid domestic wastes and carbon-containing materials in liquid slag bath lanced by oxygen-containing gas. Mixture of combustible non-toxic components of wastes is loaded on oxygen converter bottom in lumped form at combustion heat of MJ/kg in the amount of 0.5-20 kg/t of liquid steel, after which metal scrap is charged and carbon-containing materials are added; then, charge thus formed is heated with oxygen at flow rate exceeding nominal level by 0.59-0.73 m³/kg of loaded wastes and molten iron is poured at oxidizing lancing. Used as combustible non-toxic components of wastes are food wastes, textile, rubber, leather, waste wood, bones.

EFFECT: possibility of combining processes of oxidizing refining of metal and thermal reworking of wastes in converter.

2 cl, 1 ex

Description

The invention relates to methods for the thermal processing of municipal solid waste (MSW) and can be used in ferrous metallurgy, in particular in oxygen-converter production.

There is a method of thermal processing of solid waste in furnaces, boilers with grates / Grechko A.V. Thermal methods for processing municipal solid waste: energy consumption and environmental friendliness // Electrometallurgy, 2000, No. 8, p. 33-39 /.

The known method allows you to burn solid waste and, thus, solve the problem of their disposal.

The disadvantage of this method is the low process temperature (600-900 ° C), at which highly toxic compounds such as dioxins, furans, etc. are most intensively formed, in addition, secondary solid waste (25-30%), infected with these toxic substances, is formed, which require burial.

A known method of thermal processing of solid waste in aggregates with a liquid slag bath / US No. 4294433, F 27 B 001/20, 1981 /.

The known method allows you to recycle (utilize) MSW in high-temperature furnaces (1200-1400 ° C and above), widespread in non-ferrous metallurgy and called Vanyukov (PV) furnaces, characterized by the absence of secondary solid waste.

The disadvantage of this method is the high energy consumption, harmful emissions into the atmosphere and low processability associated with specific factors of a regional nature: the construction or reconstruction of units with a liquid slag bath to work on new technology, the presence of other waste and their value for joint processing with solid waste and volumes in the use of processed products, etc.

The closest in technical essence and the achieved result to the proposed one is a method of thermal processing of solid waste, which includes loading waste and carbon-containing fuel into a molten slag bath, purged with oxygen-containing gas / SU No. 1315738, 4 F 23 G 5/00, 1987 /.

The known method allows for the rapid heating of solid waste and their burning directly in the volume of slag melt, to exclude the emission at low temperature of gases containing organic compounds, including especially dangerous ones such as dioxins.

The disadvantage of this method is the high investment in the design and construction of plants for the incineration of solid waste in bubbling slag melt, the complexity of their industrial operation, additional costs for cleaning flue gases from dust and gaseous harmful inorganic compounds, continuous removal of the resulting slag from the furnace.

The objective of the invention is to reduce capital costs by combining the process of oxidative refining of metal and thermal processing of solid waste in existing metallurgical units.

The problem is solved as follows.

In the method for processing municipal solid waste, including loading waste, carbon-containing materials and purging with oxygen, according to the invention after loading to the bottom of the converter of municipal solid waste in the form of a mixture of agglomerated combustible non-toxic solid waste components with a calorific value of 4-15 MJ / kg in an amount of 0.5- 20 kg / t of liquid steel, heaped up with scrap metal and heated with oxygen with a flow rate in the range of 110-200% of the nominal, then pour molten iron and conduct oxidative refining.

As combustible non-toxic components of solid waste use food waste, textiles, rubber, leather, wood waste, bones.

The presented sequence of the method for thermal processing of solid household waste in an oxygen converter allows to significantly increase the process temperature in the first minutes of purging and accelerate the induction of primary ferrous slag, which ensures the complete burning of combustible non-toxic solid waste components in the volume of slag melt and does not complicate the oxidative refining of metal.

MSW is pre-sorted to separate valuable, non-combustible, toxic components and / or components that release toxic compounds during decomposition and combustion. After sorting, the residual portion of solid waste is grained in order to increase the density and reduce the likelihood of the removal of light and small components from the steelmaking unit. The sizes of the pieces (briquettes, bags, granules, etc.) should ensure their convenient placement in loading devices, unimpeded introduction into an oxygen converter and their complete combustion in the volume of slag melt.

The heating of charge materials with oxygen after they are loaded onto the bottom of the converter improves the process of slag formation, accelerates mass transfer processes between metal and slag, provides deep refining of metal from harmful impurities, and reduces metal loss with peroxidized slag.

The introduction of solid waste into the heated part of charge materials enhances the exothermic effect of the combustion of carbon-containing materials due to the presence of easily ignitable and quick-burning components (paper, textiles, etc.) in the solid waste and helps to reduce oxygen consumption due to the presence of its own oxygen-containing gas in the waste organic mass.

Rapid heating of solid waste and their burning directly in the volume of high-temperature slag melt completely eliminates the formation of gaseous highly toxic compounds such as dioxins, furans, etc., does not require additional costs for cleaning flue gases from dust and gaseous harmful inorganic compounds, as well as special removal from the unit the resulting slag.

The heat of combustion of a mixture of combustible non-toxic components of solid waste is determined by the ratio of its components: food waste, textiles, rubber, leather, wood waste, bones. The use of solid waste with a calorific value of less than 4 MJ / kg leads to a "cold" start of smelting, poor dissolution of lime, a decrease in the reactivity of slag at the beginning of purging, slows down the mass transfer processes between metal and slag, and does not allow combining the process of oxidative refining and thermal processing of solid waste in oxygen converter.

The use of a mixture of combustible non-toxic solid waste components with a calorific value of more than 15 MJ / kg requires additional sorting of waste and removal of low-calorie solid waste components (for example, food waste) from the mixture and increases the cost of thermal processing of solid waste in an oxygen converter.

When the amount of the mixture of combustible non-toxic components of solid waste is less than 0.5 kg / t of liquid steel, the exothermic effect of the combustion of carbon-containing materials is reduced, which leads to a "cold" start of smelting, slows down slag formation in the first minutes of purging and complicates the oxidative refining of the metal, does not allow combining it with thermal processing of solid waste in an oxygen converter.

When the amount of the mixture of combustible non-toxic components of MSW is more than 20 kg / t of liquid steel, the amount of slag and flue gases generated during the combustion of MSW increases, which pollutes the metal with secondary solid components, requires additional costs for cleaning flue gases from dust and inorganic compounds and does not allow combining thermal processing of solid waste with oxidative refining of metal in an oxygen converter.

When the oxygen consumption for heating the charge materials is less than 110% of the nominal supplied to scrap metal heating, the exothermic effect of burning carbon-containing materials and easily ignitable and quick-burning solid waste components (paper, textiles, etc.) is reduced, and the necessary heating of the charge materials is not ensured, which leads to a "cold" "at the beginning of the process, it slows down slag formation at the beginning of purging, complicates the oxidative refining of the metal and does not allow combining it with the thermal processing of solid waste in an oxygen convoy rtere.

With an increase in the oxygen consumption for heating the charge materials more than 200% of the nominal supplied to the heating of scrap metal, the degree of its assimilation decreases, the cost of oxidative refining of metal and thermal processing of solid waste in an oxygen converter increases.

A new technical result of the invention is to achieve optimal conditions for the rapid induction of primary ferrous slag immediately after casting iron at the beginning of purging and burning of combustible non-toxic solid waste components in the volume of high-temperature slag melt without the formation of gaseous, highly toxic compounds and secondary solid components that pollute the metal, which allows the process to be combined oxidative refining of metal and thermal processing of solid waste in an oxygen converter.

The method is implemented at the West Siberian Metallurgical Combine in the oxygen-converter shop No. 2.

Example: In a 350-ton converter with overhead oxygen blast, 2 tons of pelletized solid waste (6.25 kg / ton of liquid steel) are charged. Preliminary MSW sorts and allocates valuable (ferrous and non-ferrous metals, glass, plastic, waste paper and cardboard), non-combustible (stones) and toxic (mercury lamps, galvanic cells) components. The residual part of solid waste is a mixture of non-toxic combustible components of solid waste with a heat of combustion of 11.6 MJ / kg of the following composition (wt.%): Food waste - 74; waste paper unsuitable for recycling - 8; textiles - 12; skin - 1.7; wood waste - 1.7; rubber - 1.3; bones - 1.3, which is pressed into bags of 800 × 500 × 500 mm in size and tied with 3 rows of metal wire. After loading the solid waste at the bottom of the converter, they are heaped up with scrap metal, carbon-containing materials (gas coal), lime and lime-magnesia flux are added. Next, the oxygen lance is lowered and oxygen is heated for 7.5 minutes with a flow rate of 200 m ³ / min, which is 140% of the nominal supplied to the scrap metal heating. After warming up, cast iron is poured into the converter. The temperature of cast iron is 1400 ° C, the chemical composition,%: Si 0.48; Mn 0.40; S 0.018; P 0.15. Next, oxidative refining is carried out, seeding slag-forming materials (lime and manganese sinter) during purging, moving the tuyere in the vertical direction with a change in oxygen consumption. Purge Duration 18 min. The temperature of the metal on the felling 1650 ° C, the metal contains,%: C 0.10; Mn 0.16; P 0.015; S 0.013. Slag basicity 3.0; FeO content of 18.5%; yield 92.0%.

The application of the proposed method for the thermal processing of municipal solid waste in the converter allows to reduce capital costs by combining the process of oxidative refining of metal and thermal processing of solid waste in existing metallurgical units.

Claims (2)

1. The method of thermal processing of solid household waste, including loading waste, carbon-containing materials and purging with oxygen, characterized in that the loading of solid household waste in the form of a mixture of agglomerated combustible non-toxic components with a calorific value of 4-15 MJ / kg in an amount of 0.5-20 kg / t of liquid steel with carbon-containing materials is carried out at the bottom of the converter, heaped up with scrap metal and purged with oxygen with a flow rate of 110-200% of the nominal, then liquid cast iron is poured and oxidative refining is carried out. 2. The method according to claim 1, characterized in that food waste, textiles, rubber, leather, wood waste, bones are used as combustible non-toxic components of solid household waste.