Carbon black processing

Acetylene black is derived from feeding acetylene into high-lempcralure retorts whereupon the acetylene dissociates into carbon and hydrogen. This reaction is exothermic (other carbon black processes arc endothermic). Temperature control of the furnace is effected by throttling the acetylene feed. 

The observed almost universal value of the surface fractal dimension ds 2.6 of furnace blacks can be traced back to the conditions of disordered surface growth during carbon black processing. It compares very well to the results evaluated within the an-isotropic KPZ-model as well as numerical simulations of surface growth found for random deposition with surface relaxation. This is demonstrated in some detail in [18]. 

Fig. 20 Schematic view of carbon black processing in a furnace reactor. Primary aggregates are built by two simultaneous growth processes (i) surface growth (SG) and (ii) aggregate growth (AG)...

Gas Black A process for making carbon black. Similar to the Carbon Black process, but uses a coal tar oil as the feedstock. Developed in the 1930s and still in use in 2005. 

Although the efficiency of the carbon black process has improved steadily, there is still much that can be done. Depending upon the grade of black and type of feedstock, from 50-65% of the theoretical carbon content is now being recovered from the oil as quality carbon black. A typical stack gas analysis is shown in Table III. 

EPM is preferred for dynamic applications because its age resistance retains initial product design over time and environmental expo-sure.i2 ePDM is preferred for its high resilience.12 ePM is resistant to acids, bases (alkalis), and hot detergent solution. EPM and EPDM are resistant to salt solutions, oxygenated solvents, and synthetic hydraulic fluids. 2 Properties are determined by the composition of the base compound. A typical formulation includes Vistalon EP(D)M, carbon black, process oil, zinc oxide, stearic acid, and sulfur. 12... 

Several modem processes for the production of carbon-based blacks (flame carbons . v.) are based on the thermal decomposition of lower gaseous hydrocarbons in the absence of air. Developed in the 1930s, the thermal black process is still used for the production of pigments. In distinction from other carbon black processes, the method is discontinuous the reaction furnace is heated to about 1400°C with a mixture of natural gas and air, then the air is switched off. The gas is decomposed, an andothermic process which cools the furnace. This cycle is then repeated. Fine thermal blacks of particle size 120-200 nm and medium thermal blacks of 300-500mn are typically produced (Buxbaum, 1998). 

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

Nitrile Rubber. Vulcanized mbber sheets of NBR and montmorillonite clay intercalated with Hycar ATBN, a butadiene acrylonitrile copolymer have been synthesized (36). These mbber hybrids show enhanced reinforcement (up to four times as large) relative to both carbon black-reinforced and pure NBR. Additionally, these hybrids are more easily processed than carbon black-filled mbbers. 

The carbon black (soot) produced in the partial combustion and electrical discharge processes is of rather small particle si2e and contains substantial amounts of higher (mostly aromatic) hydrocarbons which may render it hydrophobic, sticky, and difficult to remove by filtration. Electrostatic units, combined with water scmbbers, moving coke beds, and bag filters, are used for the removal of soot. The recovery is illustrated by the BASF separation and purification system (23). The bulk of the carbon in the reactor effluent is removed by a water scmbber (quencher). Residual carbon clean-up is by electrostatic filtering in the case of methane feedstock, and by coke particles if the feed is naphtha. Carbon in the quench water is concentrated by flotation, then burned. 

Processing conditions also significantly affect the lengths and numbers of continuous carbon black chains, therefore the semiconducting shields must be appHed with a minimum of residual mechanical stress. 

The aimual worldwide production of carbon blacks, which iaclude a large variety of carbonaceous products, was estimated to be around six million metric tons ia 1994. More than 90% of this pigment is consumed by the mbber iadustries, ia particular, by the tire iadustry as a reinforcing agent. The rest (- 500, 000 t) is used for coloring plastics, printing inks, and paints. Particle size of carbon blacks varies from 5 to 500 p.m and can be controlled by the process conditions and feedstock (see Carbon, carbon black). 

Two processes, partial oxidation and thermal decomposition, are used for the production of carbon blacks. The partial oxidation process can be represented by the foUowiag reaction ... 

The production process or the feedstock is sometimes reflected ia the name of the product such as lamp black, acetylene black, bone black, furnace black, or thermal black. The reason for the variety of processes used to produce carbon blacks is that there exists a unique link between the manufactuting process and the performance features of carbon black. 

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