SU1723152A1 - Method of operation of a controlled atmosphere carburizing electric furnace - Google Patents

Abstract

The invention relates to the chemical and heat treatment of materials, in particular to the operation of electric furnaces with carbon-containing atmospheres. The purpose of the invention is to increase the reliability of the furnace elements by reducing the degree of carburization. According to the method, the content of CO in the cementation furnace is within 34-70% by supplying to the furnace an additional oxidizing agent containing oxygen and / or carbon compounds with oxygen and hydrogen, which have 1- to 1 carbon atom and 1 oxygen atom. 3; 5 hydrogen atoms. A change in the flow rate of the main oxidizer (e.g. air, water, oxygen) is maintained at a given carbon potential in the furnace. The method allows to increase the re; Sura heaters from 2850 (prototype) to 4700h. ate with

Description

The invention relates to chemical heat treatment - material vi can be used in the operation of electric furnaces with carbon-containing atmospheres. ; .- ;: -. .; ... ..... -; : h :: - .;

The purpose of the invention is to increase the reliability of the operation of the furnace elements by reducing the degree of carbonization.

The method is carried out as follows. - ..; -. :; .. ..-: -, -:

When cementation is carried out, for example in the SShTs-4.9 / 10 furnace, the furnace is heated to 930–950 ° C and the carbon-containing compound and oxidizer (for example, kerosene and air) are fed into the furnace space so that

an atmosphere is present: kotra: it has the carbon potential necessary for the technological process (PP) / In the accepted practice of cementation it is 1.15-1.35% C. At the same time, the partial pressure of carbon monoxide is measured. By reducing its compound to 34%, an oxidizing agent, such as carbon dioxide (C02), is additionally fed into the furnace space. In the specific case, after reaching a temperature of 940 ° C, kerosene at a flow rate of $ 16 / drip / min is fed into the furnace SSC-4.9 / 10. After 1.6 hours from the moment of kerosene supply, air is supplied to the furnace, gradually increasing its consumption over 1 hour to 1.7 m3 / h. After that,

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go w

ate yu

the carbon potential of the furnace atmosphere and the content of CO and C02 (U. P. 0.73% C, CO 25.2%. CO2 - 0.31%). The composition of the gas (CO, C02) is determined by a Gazokhrom 3101 chromatograph and an ASGA-C1 system, and the carbon potential is determined by the foil method. In order to achieve the required content of CO and% C, an air supply of 0.94 m3 / h is changed by supplying additional COA to the furnace in an amount of 0.144 m3 / h. The results of the measurements after 1.0 h after the filing of CQ2 are as follows: 0.85% C, CO 36.2%, C02 0.51%.

Through 4 HU.P. 1.17% C, CO 36.1%, C02 0.32%. The carbon potential corresponds to the technological mode of cementation, and Рсо - to the favorable operating mode of the heaters. Zigzag heaters of Ø 5.5 mm from alloy X20H8QH were used as heaters in the furnace.

It was established experimentally that when the content of carbon polyoxide in the working atmosphere of the furnace is 25% (as in the prototype), the heater resource was 2850 h, which indicates a decrease in reliability, and at 34% 4650 h, the reliability of the heaters in this case is much higher due to the lower degree and the carburization rate due to the presence in this case of protective oxide film heaters. Therefore, as the lower limit, carbon monoxide content was set at 34% ...

Experimentally, it was found that with a carbon monoxide content of 70%, the heater resource was 4,700 hours. But with a carbon monoxide content of more than 70%, for example 75%, a decrease in the carbonization rate of products was observed due to different decreases in the mass transfer coefficient of carbon to metal, which is extremely undesirable because the performance of the process is reduced.

In this connection, carbon monoxide content in 70% hot heater life and, consequently, reliability even increased (the resource amounted to 4750 h) was taken over the upper boundary. The optimal mode of operation of the cementing furnace was observed at Rso 40% and the resource of heaters was 4670 hours.

Entering an additional amount of the oxidizing agent oxygen and / or the combination of carbon with oxygen, and / or the combination of carbon with oxygen and hydrogen, in which both 1-3 carbon atoms and 1 oxygen atom have 1-3.5 hydrogen atoms, is carried out simultaneously a decrease in the supply of the main oxidant in such a way that the value of the carbon potential remains unchanged.

For example, kerosene as a hydrocarbon, air С1bНз4 + 8 (02 + 3,76N2) + 17Н2 + 30IM2 as an oxidizing agent

(D

Rso "25%

C02 is used as an additional oxidizing agent.

CieH34 + 5 (02 + 3.76N2) + 6C02: 22CO + + 17H2 + 18N2 (2)

Rso "38%.

By reducing the oxygen supply in the composition of the air by 3 g - mol, they increased the supply of additional oxidizer C02 by 6 g - mol. The conversion of hydrocarbons by these oxidizing agents is not exactly the same, but these minor deviations are eliminated by regulation on the main oxidizer, which can be done, for example, by regulating carbon dioxide.

(CO) 2 potential according to the ratio Vr When

(CO} 2 Standing C - potential n also must be v v J2

wives be unchanged. Smoothly reducing the flow of one oxidant and increasing the flow of additional, do not change

the value of V Q and, accordingly, the carbon potential. In the case of manual adjustment, the proportions are preliminarily estimated in which the supply of one is reduced and the supply of another acidic is increased. If, for example, oxygen is used as an additional oxidizing agent

C1bN3 + 3 (02 + 3.76N2) + 502 ± 16CO + + 17H2 + 11N2, (3).

when 5 g-mol of oxygen is supplied, the oxygen supply in the air is reduced by 5 g-mol (the reduction of the air supply is 24 g-mol).

. In reaction (3), changes in oxygen are proportional; in reaction (2), one oxidant (CCJ2) is fed 2 times more than reducing oxygen in the other oxide, the body. . : - v; . . -.

An example of using oxygen is shown in reaction (3), an example of using a compound of carbon with oxygen is given in reaction (2).

As an oxidizing agent, carbon compounds with oxygen and hydrogen, formic acid (CH202) are used.

С1бНз4 + СН202 32CO + 33H2 (4)

Rso 47%

For formic acid, there are 2 hydrogen atoms per 1 carbon atom, and 1 hydrogen atom per 1 oxygen atom.

Pcd is freely controlled by varying the amount of additionally oxidizing agent, for example, as in (2).

You can also use mixtures of the listed oxidizing agents, for example, С1бНз3 + 40а + 4С02 + 4СНа02 2 24СО + + 21Н2 (5)

Rso 53%

By adding a similar mixture, it is easy to increase the CO content in the furnace, for example,

С1бНз4 + 5 (02 + 3.76N2) + 02 + 2С02 + 2СН202 - & 20СО + 17Н2 + 19N2 (6)

Rso 36%

If compounds with more than 3.5 hydrogen atoms per atom of oxygen or carbon as an oxidizing agent are used as an oxidizing agent, then it is impossible to achieve a monoxide content in the atmosphere of more than 34%.

For example, if methanol CH3OH is taken as an additional substance fed into the furnace space, from which there are 4 hydrogen atoms per 1 carbon atom and 1 hydrogen atom, then CH3 OH2CO2H2 (7)

Рсо 0,33 (33%)

And no matter how much additional substances are injected, a partial pressure of CO of more than 33% will not rise. .

Therefore, the number of hydrogen atoms arriving at 1 carbon or oxygen atom is more than 3.5 undesirable.

The fewer hydrogen atoms per carbon or oxygen atom, the less substance is needed to restore the Pc value to the required limits, but since compounds with the ratio of hydrogen to oxygen or carbon less than 1 are unknown to us, the lower limit of the ratio was equal to 1.

Thus, the proposed method allows to significantly increase the reliability of the heating elements by reducing the speed and degree of their carburization.

The implementation of the method does not require scarce and expensive devices and can be quite simply implemented.

The method can be applied in any shaft and chamber grouting furnaces. The implementation of the proposed method does not require expensive and scarce materials.

Claims (1)

The Invention Method for Operating a Cementing Furnace with a Controlled Atmosphere, including heating to operating temperature, supplying hydrocarbon and nitrogen containing compounds and an oxidizing agent to the furnace space, such as air, water, oxygen, to form carbon monoxide, hydrogen and nitrogen, and maintaining a given carbon potential by changing the consumption of these oxidizing agents, o tl and h aa yu, and so that, in order to increase the reliability of operation of the furnace elements by reducing the degree of their carburization, the content of e carbon monoxide in the furnace atmosphere and maintain its content in the range of 34-70% by filing an additional oxidizing agent containing oxygen and / or carbon-oxygen compounds and / or carbon-oxygen compounds, which have both 1 carbon atom and 1 an oxygen atom is 1-3.5 hydrogen atoms. Editor A.Dolinich Tehred M. Morgenthal Order 1044 Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab. Proofreader M.Maksimishinets