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Classification of carbon additives for petroleum coke

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Classification of carbon additives for petroleum coke

Date:2017-10-28 Author: Click:

Petroleum coke carburant is black or dark gray hard solid petroleum products, with metallic luster, porous, is formed by the crystallization of tiny graphite granular, columnar or needle-like carbon. Petroleum coke is composed of hydrocarbons, 90-97% carbon and 1.5-8% hydrogen. It also contains nitrogen, chlorine, sulfur and heavy metal compounds.

The output of raw petroleum coke is less than 5% of the crude oil used. The annual output of raw petroleum coke in the United States is about 30 million T. The content of impurities in raw petroleum coke is high and can not be directly used as carburizing agent. The classification of carbon additives in raw petroleum coke is sponge like, needle like, granular and flowing.

Graphitized petroleum coke carburizer is a product of crude oil which is separated from light and heavy oil by distillation and then converted into heavy oil by hot cracking. Petroleum coke is a black block with irregular shape and different sizes. It has a metallic luster and porous structure. The main elements are carbon, accounting for more than 80 wt%. The rest are hydrogen, oxygen, nitrogen, sulfur and metal elements. . Volatile and mineral impurities (sulfur, metal compounds, water, ash, etc.) determine the chemical properties of petroleum coke.

Characteristics of petroleum coke increasing agent (function of petroleum coke carbon additive):

1, the chemical composition is pure, high carbon, low sulfur, harmful ingredients are extremely small, absorption rate is high.

2. The graphitization degree of the product is high, the nucleation ability of the molten iron is improved, the number of nodular graphite cast iron is increased during inoculation, the graphite nucleation is increased in the molten iron of electric furnace, and the distribution of graphite in the casting is refined and uniform.

3. The particle size is moderate, the porosity is large, and the absorption speed is fast.

Carbon additive for petroleum coke

4, excellent performance and stability. Quality helps to reduce smelting production costs, improve the quality of metals and castings, so that users can obtain significant benefits in both cost and quality. The use of petroleum coke carburizer is the key to smelting gray iron with more scrap steel in electric furnace, and the cost determines that many factories use the cheapest carburizer. The use of it is sometimes very good, no serious quality problems have been found. At present, most of the graphitized petroleum coke carburizer is suitable for electric furnace smelting, but also a small part of it is absorbed. The calcined petroleum coke, which is specially fast, is used as a carbon increasing agent for cupola. The feeding mode of electric furnace smelting should be that the carburizer should be put in with the scrap and other burden, and small doses of carburizer can be added to the surface of molten iron. Petroleum coke carbon increasing agent is made from petroleum coke calcined and purified, and its appearance is round or multi prism. It is characterized by high carbon, low sulfur and low ash. It is an ideal carbon-adding material and reaction intermediate in metallurgical, chemical, mechanical and electric industries, and has been widely used.

Petroleum coke carbon increasing agent is made from petroleum coke calcined and purified, and its appearance is round or multi prism. It is characterized by high carbon, low sulfur and low ash. It is an ideal carbon-adding material and reaction intermediate in metallurgical, chemical, mechanical and electric industries, and has been widely used.

The main uses of petroleum coke are pre-baked anodes and pastes for aluminum electrolysis, carbon industry to produce carbon additives, graphite electrodes, smelting industrial silicon and fuels.

According to the structure and appearance of petroleum coke, petroleum coke products can be divided into acicular coke, sponge coke, projectile coke and powder coke.

(1) Needle coke, with obvious needle-like structure and fiber texture, is mainly used as high-power and ultra-high-power graphite electrode in steelmaking. Because needle coke has strict quality requirements in sulfur content, ash, volatile and true density, it has special requirements for needle coke production process and raw materials.

(2) sponge coke has high chemical reactivity and low impurity content. It is mainly used in the aluminum smelting industry and the carbon industry.

(3) Projectile coke or spherical coke: spherical shape, diameter 0.6-30mm, generally produced by high sulfur, high asphaltene residue, can only be used as power generation, cement and other industrial fuels.

(4) Powdered coke: It is produced by fluidized bed coking process with fine particles (0.1-0.4 mm in diameter), high volatile matter and high coefficient of thermal expansion. It can not be directly used in electrode preparation and carbon industry.

According to the different sulfur content, it can be divided into high sulfur coke (more than 3% sulfur content) and low sulfur coke (less than 3% sulfur content). Low sulphur coke can be used as anode paste and prebaked anode for aluminum plant and graphite electrode for steel plant. High quality low sulfur coke (sulfur content less than 0.5%) can be used to produce graphite electrodes and carbon additives. Low sulfur coke (sulfur content less than 1.5%) of common quality is commonly used to produce prebaked anode. Low quality petroleum coke is mainly used for smelting industrial silicon and producing anode paste. High sulfur coke is generally used as fuel for cement plants and power plants. 2. the influence of adding amount of carburizing agent.

Under certain conditions of temperature and chemical composition, the saturation concentration of carbon in molten iron is certain. The dissolution limit of carbon in cast iron is ([C%]=1.3+0.0257T-0.31 [Si%]-0.33 [P%]-0.45 [S%]+0.028 [Mn%] (T is molten iron temperature). At a certain saturation, the more the carburizer is added, the longer the dissolution and diffusion time is required, the greater the corresponding loss, and the lower the absorption rate.

3. effect of temperature on absorbance of carburant

From the point of view of kinetics and thermodynamics, the oxidation of molten iron is related to the equilibrium temperature of C-Si-O system, that is, O in molten iron reacts with C and Si. However, the equilibrium temperature varies with the target C and Si content. When the molten iron is above the equilibrium temperature, carbon oxidation takes precedence. C and O form CO and C O2. In this way, the oxidation loss of carbon in molten iron increases. Therefore, above the equilibrium temperature, the absorbency of carburizing agent decreases; below the equilibrium temperature, the saturated solubility of carbon decreases, and the dissolution and diffusion rate of carbon decreases, resulting in a lower yield; at the equilibrium temperature, the absorbency of carburizing agent is the highest.

4. the influence of iron stirring on the absorbance of carburant

Mixing is conducive to the dissolution and diffusion of carbon, so that the carburizing agent will be burned on the surface of molten iron. The stirring time is long and the absorption rate is high before the carburizing agent is completely dissolved. Stirring can also reduce the carburizing and holding time, shorten the production cycle and avoid the burning loss of alloy elements in molten iron. However, too long stirring time not only has a great impact on the service life of the furnace, but also increases the carbon loss in molten iron after the carburizer dissolves. Therefore, suitable iron stirring time should be guaranteed to completely dissolve the carburizing agent.


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