United Carbon process

Figure 28.5 Flow chart of the United Carbon Process...

Precipitated Calcium Carbonate. Precipitated calcium carbonate can be produced by several methods but only the carbonation process is commercially used in the United States. Limestone is calcined in a kiln to obtain carbon dioxide and quicklime. The quicklime is mixed with water to produce a milk-of-lime. Dry hydrated lime can also be used as a feedstock. Carbon dioxide gas is bubbled through the milk-of-lime in a reactor known as a carbonator. Gassing continues until the calcium hydroxide has been converted to the carbonate. The end point can be monitored chemically or by pH measurements. Reaction conditions determine the type of crystal, the size of particles, and the size distribution produced. 

Chlorination of natural rubber (NR) is carried out with chlorine in carbon tetrachloride solution at 60-90°C to yield a chlorinated rubber containing about 65% chlorine, which corresponds to 3.5 chlorine atoms per repeat unit. The process is complex and includes chlorine addition to the double bond, substitution at allylic positions, and cyclization. Chlorinated rubber has high moisture resistance and is resistant to most aqueous reagents (including mineral acids and bases). It is used in chemical- and corrosion-resistant paints, printing inks, and textile coatings. Bromination of butyl rubber is also practiced [Parent et al., 2002]. 

T0848 University of Southern California, Hybrid Microfiltration-Bioactive Carbon Process T0852 US EPA Risk Reduction Engineering Laboratory, Mobile Volume Reduction Unit (VRU)... 

Cracking is the process of breaking down hydrocarbons with many carbon atoms into smaller units whereas alkylation is the process of combining smaller hydrocarbons into larger units. Both processes are carried out catalytically and both are used to convert hydrocarbons into units having 6 to 10 carbon atoms suitable for use in gasoline. 

This is a serious misnomer as these inert constituents of pitch are certainly not inert during the carbonization processes. It is well-established that the size of the optical texture of a coke can be reduced by the presence within the pitch of primary QI material (102-105). The QI material within the pitch becomes adsorbed on the surfaces of the growth units of mesophase. This thereby prohibits coalescence of these growth units into the larger sized optical textures. When this process is viewed by hot-stage optical microscopy (106) this lack of coalescence is seen to reduce markedly the flow characteristics of the mesophase - it becomes almost static. 

The optical texture of mesophase and resultant carbons is observed readily by means of a reflected polarized light microscope and may be classified according to the shape and size of the isochromatic units. Such a classification is useful to evaluate the properties of mesophase and carbons such as needle cokes. The mesophase has been defined as the intermediate state which shows optical anisotropy and is quinoline-insoluble at room temperature (5,51) (liquid crystal glass), although it is a viscous liquid crystal during the carbonization process (6). ... 

Chemetics has developed a process for treating spent alkylation sulfuric acid with nitric acid to produce a sulfuric acid that can be used to acidulate phosphate rock, the major use for sulfuric acid. The organic contaminants are converted to carbon particles that are removed with the gypsum on filtration of the phosphoric acid. Special alloys are used in the fabrication of the acid reactor. Topsoe developed and, by the year 2005 had built, more than 45 Wet Sulfuric Acid (WSA) process units. This process is especially suited for... 

The physical characteristics of the plastic input influence the carbonization process. In static conditions, the heating rate of small particles is higher than for large particles. In this case, difficulties could occur for the extrapolation from small-scale carbonization data to pilot- and industrial-scale units. The physical and chemical properties of the material are of great importance in order to be able to evaluate the heat transfer from the reactor inside the material. 

Alkylbenzenes (BTX) are mainly made from petroleum and coal in the United States. Petroleum refineries produce about 95% of BTX and the rest comes from coal. Coal based BTX is obtained as a by-product from high temperature carbonization of coal employed for the production of metallurgical coke. Carbonization process yields only 2-3 gallons of BTX per ton of coal. BTX can be produced in larger quantities by hydrogenation and hydrocracking of coal (1,2). The organic... 

Direct solvent extraction is the most widely used oil-recovery method for soybeans, but it also requires considerable capital and large scale to compete. In actual practice, solvent extraction is used to crush over 98% of the soybean processed in the United States. Process flow diagrams are shown in Figures 3 and 4. Most soybean solvent-extraction plants process more than 2,500 MT/day (Figure 5), and some are capable of processing as much as 5,000 MT/day (especially newly constructed plants in Brazil). Direct-solvent-extraction plants smaller than 1,000 MT/day have difficulty competing in the United States. At various times, soybeans have been extracted commercially with petroleum distillate fractions that resemble gasoline, acetone, carbon disulfide, ethanol, trichloroethylene, and even water. 

About a pound of dry slndge will be generated per pound of carbon added. If regeneration is practiced, carbon slndge is reactivated and reused with only a small portion removed to prevent buildup of inert. PAC physicochemical process systems are reasonably reliable from both a unit and process standpoint. In fact, PAC systems can be used to improve the process reliability of existing systems. Readers are referred to recent reports for additional information (29,30). 

Like all unit chemical processes, the RO is usually not capable of standing entirely by Itself. The important thing to remember is that a system must be developed to give a complete product. In the case of Cummins, the complete system includes dissolved air flotation, anthracite/sand filtration, activated carbon filtration and RO. In the case of Whitestone Chemical, the complete system includes RO and a cleaning regimen to maintain the RO at the required permeate flow rate. Time will tell which of these alternatives has the best economics. The economics and the proper system using RO are both dependent on the problem that requi res a solution. 

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