GB1601909A - Method of preparation of electrode coke suitable for high-intensity electrodes for iron and steel metallurgy - Google Patents

Description

(54) METHOD OF PREPARATION OF ELECTRODE COKE SUITABLE FOR HIGH-INTENSITY ELECTRODES FOR IRON AND STEEL METALLURGY (71) We, INSTYTUT TECHNOLOGII NAFTY of Lukasiewicza Str., 1, Krakow, Poland, a State enterprise organised and existing under the laws of Poland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method for the preparation of electrode-grade coke for the manufacture of high-intensity electrodes for iron and steel metallurgy.

In the manufacture of high-intensity electrodes, which are operated at high and variable current loads, the required electrode coke has to have special structural characteristics i.e. high graphitization ability, low sulphur, metal and ash contents, high density and low thermal expansion coefficient.

Such coke is obtained from selected petroleum feed-stocks containing large quantities of condensed aromatic hydrocarbons with a high carbon to hydrogen ratio, the said feedstocks yielding, in a carbonization process, a hexagonal plate structure poor in cross-bonds, while at high temperatures yielding the graphite structure.

The known methods for the preparation of electrode coke for the manufacture of highintensity electrodes for iron and steel metallurgy comprise processing of petroleum distillates, which may include a temporary polycondensation or aromatic hydrocarbons contained in these distillates, which polycondensed aromatics would eventually be coked, combining these distillates with coal tar distillates or with high-aromatic petroleum distillates and coking the mixture. When coal tars or pitches are used, either their high-molecular components are removed or they are treated by melting them with alkaline compounds to eliminate the heterocyclic compounds which makes it difficult to arrange an orderly crystalline structure during a subsequent high-temperature thermal treatment.

According to the invention there is provided a method for the preparation of electrode coke suitable for making high intensity electrodes for iron and steel metallurgy from petroleum naphtha and coal fractions comprising blending mixtures of petroleum naphtha and coal fractions to form a homogenous feedstock blend so tbat the feedstock blend has a sulphur content of not more than 1% by weight and a total aromatic content of from 7090 /O by weight wherein the mono and bicyclic aromatics content thereof amounts to from 3--8% by weight, and n-hexane insoluble polycyclic ( > 1 ring) aromatics content thereof, which are benzene soluble, amounts to from 30--50% by weight, and benzene insolubles content thereof amounts to from 0 050 5% by weight, coking the blend and optionally returning petroleum and coal distillates formed in the process of coking distillates to the blending process.

The preparation method of electrode-grade coke suitable for high-intensity electrodes for the purpose of iron and steel metallurgy preferably comprises the selection, pretreatment and blending such low-sulphur petroleum and coal feedstocks or distillates from coking coal and petroleum fraction blends that a total contents of aromatics in these blends preferably amounts to a minimum of 85%, provided the contents of mono and bycyclic aromatics does not exceed 5% by weight of the total aromatics, and likewise contents of polycyclic hexanein soluble aromatics which are benzenesoluble is a minimum of 40% by weight.

Also, the benzene-insolubles should not exceed 0 5% by weight of the total aromatics content.

Example 1 An oil from petroleum naphtha pyrolysis is mixed with a distillation residue containing 4e50% by weight of liquid products obtained from coking of a mixture of compounds obtained from coal processing and petroleum fractions, in a ratio of from 1:1 to 2:1. The mixture of oil and distillation residue is characterized by the following chemical properties:: - sulphur content of not more than 1% /Oo by weight; - aromatic hydrocarbons mono- and bicyclic content-of from 3 to 8% by weight; - content of polycyclic hydrocarbons which are n-hexane-insoluble-from 30 to 50% by weight; - content of components which are benzene insoluble-from 0 05 to 0 5% by weight; - content of aromatic hydrocarbons-from 70 to 90% by weight.

The above residue is subjected to a coking process at a temperature of from 480"C to 530"C, under a pressure of from 3 to 5 atm in coke chambers according to known methods.

Example II A coke oven tar after being purified to remove high molecular weight compounds according to one of the known method3, is introduced together with an oil from petroleum naphtha pyrolysis in a ratio of from 1:2 to 1:4, or together with a mixture of an oil from pyrolysis and 40--50% by weight of a distillate residue obtained from coking of a mixture of coal and petroleum fractions, into a stripping column, wherein the counter-current flow exchange of steam and gases from coke chambers ensures that full mixing and homogenization of carbon and petroleum products takes place.

A homogeneous mixture having the following chemical properties is received from the bottom of the said column: - sulphur content of not more than 1 1% by weight; - content of aromatic hydrocarbons monoand bicyclic of from 3 to 8 by weight; - content of aromatic hydrocarbons polycyclic in n-hexane insoluble-from 30 to 50% by weight; - content of components which are benzene insoluble-from 0 05 to 0 5% by weight; total content of aromatic hydrocarbons- from 70 to 90% by weight.

The said homogeneous mixture is subjected to coking in coke chambers according to known methods. The raw coke obtained by one of the said methods, after thermal processing in calcining furnaces, shows a high ability for graphitization, low sulphur, metal and ash content, high density and low coefficient of heat expansion, and the graphite electrodes obtained from this coke are characterized by low electrical resistivity and high resistance to heat shocks and current loads, as demanded of high intensity electrodes for iron and steel metallurgy.

WHAT WE CLAIM IS: 1. A method for the preparation of electrode coke suitable for making high intensity electrodes for iron and steel metallurgy from petroleum naphtha and coal fractions comprising blending mixtures of petroleum naphtha and coal fractions to form a homogeneous feedstock blend so that the feedstock blend has a sulphur content of not more than 1 1% by weight and a total aromatic content of from 70--90% by weight wherein the mono and bicyclic aromatics content thereof amounts to from 38/oo by weight, and n-hexane insoluble polycyclic ( > 1 ring) aromatics content thereof, which are benzene soluble, amounts to from 30--50% by weight, and benzene insolubles content thereof amounts to from 0.05#).5% by weight, coking the blend and optionally returning petroleum and coal distillates formed in the process of coking to the blending process.

2. A method for the preparation of electrode coke substantially as hereinbefore described.

3. An electrode coke whenever made by a method according to either one of the Examples hereinbefore.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. - sulphur content of not more than 1% /Oo by weight; - aromatic hydrocarbons mono- and bicyclic content-of from 3 to 8% by weight; - content of polycyclic hydrocarbons which are n-hexane-insoluble-from 30 to 50% by weight; - content of components which are benzene insoluble-from 0 05 to 0 5% by weight; - content of aromatic hydrocarbons-from 70 to 90% by weight. The above residue is subjected to a coking process at a temperature of from 480"C to 530"C, under a pressure of from 3 to 5 atm in coke chambers according to known methods. Example II A coke oven tar after being purified to remove high molecular weight compounds according to one of the known method3, is introduced together with an oil from petroleum naphtha pyrolysis in a ratio of from 1:2 to 1:4, or together with a mixture of an oil from pyrolysis and 40--50% by weight of a distillate residue obtained from coking of a mixture of coal and petroleum fractions, into a stripping column, wherein the counter-current flow exchange of steam and gases from coke chambers ensures that full mixing and homogenization of carbon and petroleum products takes place. A homogeneous mixture having the following chemical properties is received from the bottom of the said column: - sulphur content of not more than 1 1% by weight; - content of aromatic hydrocarbons monoand bicyclic of from 3 to 8 by weight; - content of aromatic hydrocarbons polycyclic in n-hexane insoluble-from 30 to 50% by weight; - content of components which are benzene insoluble-from 0 05 to 0 5% by weight; total content of aromatic hydrocarbons- from 70 to 90% by weight. The said homogeneous mixture is subjected to coking in coke chambers according to known methods. The raw coke obtained by one of the said methods, after thermal processing in calcining furnaces, shows a high ability for graphitization, low sulphur, metal and ash content, high density and low coefficient of heat expansion, and the graphite electrodes obtained from this coke are characterized by low electrical resistivity and high resistance to heat shocks and current loads, as demanded of high intensity electrodes for iron and steel metallurgy. WHAT WE CLAIM IS:

1. A method for the preparation of electrode coke suitable for making high intensity electrodes for iron and steel metallurgy from petroleum naphtha and coal fractions comprising blending mixtures of petroleum naphtha and coal fractions to form a homogeneous feedstock blend so that the feedstock blend has a sulphur content of not more than 1 1% by weight and a total aromatic content of from 70--90% by weight wherein the mono and bicyclic aromatics content thereof amounts to from 38/oo by weight, and n-hexane insoluble polycyclic ( > 1 ring) aromatics content thereof, which are benzene soluble, amounts to from 30--50% by weight, and benzene insolubles content thereof amounts to from 0.05#).5% by weight, coking the blend and optionally returning petroleum and coal distillates formed in the process of coking to the blending process.

2. A method for the preparation of electrode coke substantially as hereinbefore described.

3. An electrode coke whenever made by a method according to either one of the Examples hereinbefore.