CN1189890A - Process for melting of metal materials in a shaft furnace - Google Patents

Abstract

The invention relates to a process for melting of metal materials substances in a shaft furnace. During said process, coke is burned with pre-heated air and substantially clean oxygen, and the flue gases heat in counterflow the metal charge. The melt is overheated and carburized in the coke bed, a blast of a fixed portion of the oxygen being injected into the coke bed at very high speed and as far as possible to improve the gespenetration through the coke bed, and a blast of a second variable quantity of oxygen being injected into the blastring.

Description

The method of smelting metal furnace charge in shaft furnace

With the air of preheating and quite pure oxygen combustion, and flue gas adverse current heating of metal material, and wherein melt overheated and carburizing in coke bed.

The present invention relates to the method for smelting metal furnace charge in shaft furnace, coke wherein, although develop the method for electrical heating and flame heat melting, but still in the shaft (tower) furnace of coke heating smelting metal and nonmetal raw material, as ferrous metal and non-ferrous metal, basalt and diabase, therefore, about 60% of current all iron materials be still and in the cupola furnace, produce.

The reason of this high occupation rate of market in cupola furnace is that it constantly further develops, and wherein in the improvement of many known methods, the exploitation of hot-blast cupola and the use of oxygen are significant.

Therefore, for example remedied the technical process defective and the metallurgical imperfection in cold-blast cupola furnace greatly by the exploitation hot-blast cupola, as:

---the iron temperature is low

---the burnup height of silicon

---carburizing is low

---the coke consumption height

---the sulphur absorption is big

---the refractory material abrasion are high.

By using oxygen also to obtain similar improvement, wherein oxygen or by making enrichment is up to 25% in the air blast of cupola furnace, perhaps blast the cupola furnace by directly injecting with subsonic speed.Yet because the operating cost height, oxygen can only be to use discontinuously, for example, so that cold cupola furnace starts rapidly or the temperature of iron is raise.Only just might improve smelting capacity, promptly use oxygen continuously in special circumstances.

Although introduced the corrective measure of these methods,

---melting output

---the temperature of iron

---coke feeds in raw material when optimal point of operation, still might only change in very narrow scope.

Relation between the smelting capacity and the blow rate required and the oxygen addition is described with known Jungbluth equation.This equation derives from the generation of quality and energy, and wherein coke is reinforced must determine each cupola furnace like the experience with ratio of combustion.

With various parameters, promptly reinforced the and ratio of combustion of the blow rate required, coke interrelates with target component, promptly draws feed in raw material melting output figure Fig. 1 with identical blow rate required curve of identical coke.

So-called J ungbluth figure, promptly this melting output figure must determine each experience ground, cupola furnace.To be used for another cupola furnace be impossible to cover, and this is because work as boundary condition, and during as changes such as the reactivity of coke size, coke, feed composition, blast rate, furnace pressure power, temperature, operating characteristics changes immediately.

When temperature is the highest, the thermal loss minimum.Too high when the blow rate required, when promptly flowing velocity was very high, the cupola furnace was by over-blowing.Too small when air capacity, promptly flowing velocity is crossed when hanging down, cupola furnace young blow (underblown).In both of these case, ignition temperature all reduces, this be because, on the one hand must heat the N that brings into simultaneously ₂, the CO that additionally generated of heat takes away on the other hand.And when over-blowing, the accompanying element of iron is by strong oxidation.

By using oxygen for example to be up to 24% (volume) of the blow rate required, working curve towards directly over change, promptly towards the iron output of higher temperature and Geng Gao.Temperature maximum flattens smooth, and the cupola furnace also becomes and is not subjected to the influence of young blow or over-blowing.

Constant at the iron output, when the blow rate required reduced, the reinforced minimizing of coke also was impossible when adding oxygen continuously, and this is because the temperature of iron descends, and other metallurgy and technical process problem have occurred, as

---carburizing is lower

---the burnup of silicon increases

---FeO content increases in the slag

---because the minimizing of blast velocity, air-flow flows along the furnace wall.The iron that can not cast is produced in the cupola furnace.

From the viewpoint of combustion technology, because coke is with big excessive the existence, so when smelting capacity was constant, the amount that reduces coke was significant economically, this is because the production cost of molten iron is subjected to the influence of the melting cost and the cost of raw material basically again.

In addition, be known that for a long time particularly and in the situation in cupola furnace,, still have what is called " ladle heel " at the center, cupola furnace although be rich in oxygen in the air blast or directly inject oxygen with subsonic speed with very big cupola well diameter.Oxygen that is blown into and the reaction between the carbon take place near the zone limited air-blast nozzle, and the cupola furnace is moved under the situation that exists air-flow to flow along the furnace wall.

The coke that is present in the stove center is to not contribution of reaction, and this is because because momentum is low, combustion air can not infiltrate into the bed that is positioned at its place ahead.Conversion zone is positioned near the most close air-blast nozzle, and (Fig. 2 a).Utilize known to be blown into the way of oxygen with the stove air blast of oxygen enrichment or with subsonic speed, length of penetration does not increase basically.By more oxygen is provided, conversion zone will upwards broaden gradually because of pressure condition (Fig. 2 b).

As the prerequisite of hope minimizing combustion of coke amount, wish that burning is even on the cross section, cupola furnace, the oxygen that can provide evenly distributes.For this reason, must make momentum, promptly the speed of air or oxygen stream increases, and surpasses the desired value that prior art up to now can reach.

Patent application GB 2,018,295 has described a kind of system, and in this system, oxygen promptly is blown into supersonic speed, to reduce the abrasion of refractory liner by pack into the Laval nozzle of air-blast nozzle of middle heart (centrally).But it is reinforced to reduce coke.

By contrast, with in the heart test that the supersonic nozzle of air-blast nozzle carries out of packing into show astoundingly, if the stove blow rate required is by 500～600m simultaneously ³(i.D.)/ton Fe reduce to 400～480m ³(i.N.)/and ton Fe and be blown into oxygen (Fig. 3) in addition with the stove diameter variation, combustion of coke can reduce 20～30kg/ ton Fe so, and stove running and iron smelting are not had adverse effect.Must change the concrete requirement of oxygen according to Fig. 3.At hot-blast cupola (500～600 ℃ of hot blast temperatures) and stove diameter is under the situation of 1m, the about 15～22m of the aerobic gas of iron per ton ³(i.N.), when the stove diameter is 4m, the aerobic gas 40～61m of iron per ton ³(i.N.).Oxygen Flow must be adjusted to 1.1＜M＜3 at the Mach number of nozzle exit by the stove diameter variation.Theoretical opposite with known up to now cupola furnace, tapping temperature raises simultaneously and is up to 30 ℃.The burnup of silicon reduction as a result 10%, carburizing amount improve 0.2%.If the amount of oxygen of a part of fixed amount is injected in the cupola furnace with supersonic speed, then obtain saving the best result of coke, this is owing to exist more uniform oxygen to distribute on the cross section, cupola furnace.The oxygen of surplus mixes (Fig. 4) in controlled mode with air blast in air blast ring (blastring).This measure makes constant analysis and Control become possibility.Making and being rich in oxygen in the air blast is by the component CO in the furnace gas, CO ₂And O ₂Control and regulate.Because inject with supersonic speed, reaction zone is advanced to center, cupola furnace (Fig. 2 c) with the tongue type, upwards broaden and become more even, this is because because the suction of supersonic jet is rich in O ₂Combustion air further sent into stove center (Fig. 2 d).

Owing to reduce the stove air blast, furnace pressure power reduces and the furnace gas amount reduces by 20%.Because flowing velocity is lower in the stove, Dust Capacity also reduces pro rata with the furnace gas amount.Because owing to reduce the blow rate required, recuperator only needs to be up to 30 ℃ in lower degree operation so the hot blast temperature raises

Following principle is applicable to the distribution of oxygen in air blast ring and nozzle under the various situations.

Quantum can be selected from OCI1.XLS figure.Determine to add the absolute magnitude of oxygen by the temperature of required iron.When the temperature of coke bed raise, the temperature of iron also raise.When the cooling effect at the nitrogen of following oxygen not, the temperature of coke bed raises.

The oxygen amount that will add by spray gun with supersonic speed increases with the size of stove.After the startup, seek by amount of oxygen=01 of spray gun adding and as the optimal proportion between oxygen amount=02 that the air blast oxygen enrichment is added, be preset on the controller then by the temperature of measuring iron.

Determine CO and CO in the furnace gas by the total value of the production cost that draws ₂The optimal proportion of volume fraction.The higher tool of the CO content more atmosphere of strong reducing property can be saved silicon, improve the cost of coke.Therefore, the best setting also depended on the raw-material concrete market price.In some period with in some country, the method for operating that oxidisability is stronger is more economical.Therefore, must check best CO/CO every now and then ₂Ratio, and must set suitable amount of oxygen.

The CO/CO of anticipation ₂The best setting fluctuateed, and this is because the number change of the carbon/iron that adds causes.Can remedy the fluctuation of this short-term by suitably adding oxygen.Because when adding oxygen, the temperature of coke bed very rapidly raises, so the Boudouard reaction takes place immediately.Therefore adding 01 and 02 the total speed of oxygen is controlled to and makes CO/CO ₂Ratio remain on the most economical level.Use this method of operating, also in analysis, obtain minimum change.

Claims (5)

1. the method for smelting metal furnace charge in shaft furnace, wherein coke is with the air and the quite pure oxygen combustion of preheating, and flue gas adverse current heating of metal material, and wherein melt overheated and carburizing in coke bed, it is characterized in that, in order to improve the gas permeability (gaspenetration) in the coke bed, the oxygen of a part of fixed amount is sprayed into coke bed and second strand of variable amount of oxygen injected air blast ring (blast ring) with high as far as possible speed.

2. according to the method for claim 1, it is characterized in that described a part of fixed amount is chosen to reach high as far as possible iron temperature.

3. according to the method for claim 1, it is characterized in that for the stove loss, can adjusting CO/CO in the furnace gas ₂Optimum content.

4. according to the method for claim 1 and 2, it is characterized in that utilizing control loop to make best iron temperature keep constant.

5 methods according to claim 1 and 3 is characterized in that utilizing control loop to make best furnace atmosphere keep constant.

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