Carbon residual

The heavy vacuum bottoms stream is fed to a Flexicoking unit. This is a commercial (125,126) petroleum process that employs circulating fluidized beds at low (0.3 MPa (50 psi)) pressures and intermediate temperatures, ie, 480—650°C in the coker and 815—980°C in the gasifier, to produce high yields of hquids or gases from organic material present in the feed. Residual carbon is rejected with the ash from the gasifier fluidized bed. The total Hquid product is a blend of streams from Hquefaction and the Flexicoker. 

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. 

Spent shale zone residual carbon burned... 

The moisture content of cmde sulfur is determined by the differential weight of a known sample before and after drying at about 110°C. Acid content is determined by volumetric titration with a standard base. Nonvolatile impurities or ash are determined by burning the sulfur from a known sample and igniting the residue to remove the residual carbon and other volatiles. 

Sodium a2idodithiocarbonate decomposes with evolution of nitrogen gas on addition of iodine, thus providing a useful quaHtative test for the presence of residual carbon disulfide ia aqueous solutions (25). 

A flow diagram for the system is shown in Figure 5. Feed gas is dried, and ammonia and sulfur compounds are removed to prevent the irreversible buildup of insoluble salts in the system. Water and soHds formed by trace ammonia and sulfur compounds are removed in the solvent maintenance section (96). The pretreated carbon monoxide feed gas enters the absorber where it is selectively absorbed by a countercurrent flow of solvent to form a carbon monoxide complex with the active copper salt. The carbon monoxide-rich solution flows from the bottom of the absorber to a flash vessel where physically absorbed gas species such as hydrogen, nitrogen, and methane are removed. The solution is then sent to the stripper where the carbon monoxide is released from the complex by heating and pressure reduction to about 0.15 MPa (1.5 atm). The solvent is stripped of residual carbon monoxide, heat-exchanged with the stripper feed, and pumped to the top of the absorber to complete the cycle. 

The first-order reaction of hydrogen with Ni3C at 443 K is relatively more rapid than the decomposition [669], indicating facile hydrogenation of the residual carbon at the reactant surface and the possibility of diffusion control is mentioned. 

Many of these salts melt or sublime before or during decomposition and reaction temperatures generally increase with molar mass. Thermal analyses for a selection of ammonium carboxylates have been given by Erdey et al. [915] who conclude that the base strength of the anion increases with temperature until it reaches that of NH3. Decompositions of ammonium acetate (>333 K) and ammonium oxalate (>473 K) proceed through amide formation. Ammonium benzoate and ammonium salicylate sublime (>373 K) without decomposition but ammonium citrate decomposes (>423 K) to yield some residual carbon. 

Changes in the composition of gaseous products as reaction proceeds may make definition of the fractional decomposition, a, difficult. For example, product CO and residual carbon may be capable of reducing a metallic oxide, particularly at high a and the catalytic properties of an accumulating solid product may result in promotion of secondary gas reactions. 

The decompositions of these compounds are of interest since they are used as binders in electron-emissive coatings [1023]. The initial stage of the endothermic reaction in vacuum or nitrogen (520—820 K) yields residual carbonate and a small quantity of carbon. Changes in surface area during reactions have been measured. The main volatile product is HCHO, but secondary, exothermic reactions occur on the surface of the product carbonate so that the overall reaction is... 

The thermal reactions of CaC204 H20 have been very fully investigated and this substance has been used as a thermal analysis reference material [1058], Dehydration, decomposition to the carbonate, and dissociation to CaO are all well separated, though kinetic characteristics are influenced by the presence of C02, 02 and H20 as well as by the reaction conditions, including heating rate, sample size, and sample container. Kinetic parameters for the oxalate decomposition reaction have been summarized by Gurrieri et al. [1059]. Values of E are close to 314 8 kJ mole-1. Decompositions [1057,1060,1061] of Sr (643—743 K) and Ba (663—743 K) oxalates involves some disproportion of CO, yielding residual carbon. 

Figure 2 Methyl coverage in monolayers (ML) as a function of methyl exposure, in langmuirs (L) of mixture of gases from pyrolysis source. Symbols are data showing the sum of methane formed plus residual carbon. Consistent values are obtained by summing hydrogen appearing in CH4 and H2 gas-phase products. Solid line is a guide to the eye.

V metals, vanadium has the least tendency to deoxidize by carbon monoxide evolution. This means that, at a given temperature and a given value of Pco, the residual carbon and/or oxygen contents in vanadium will be compared more to niobium and tantalum. In other words, the removal of carbon and/or oxygen from vanadium will occur to a much lesser extent than in the cases of niobium or tantalum. The effect of carbon deoxidation can be quite complicated if there is a significant loss of the metal by vaporization. The requirement of a low vapor pressure is also better satisfied by niobium and tantalum than by vanadium. 

In the case of vanadium, the suboxide, vanadium monoxide, would be more volatile than carbon monoxide except at very high carbon concentrations in the metal. The removal of the residual oxygen from this metal by carbon deoxidation is, therefore, difficult. In the case of niobium and tantalum, the partial pressure of carbon monoxide is higher than that of niobium monoxide or tantalum monoxide, even when the residual carbon concentration in the metal is as low as 200 ppm. It may therefore be expected that practically all the oxygen would be removed by evaporation of carbon monoxide without any metal loss from niobium and tantalum metals containing both oxygen and carbon. 

This expectation is consistent with the approach adopted in deoxidation practice, where the metals containing carbon and oxygen are treated at temperatures of about 2000 °C under high vacuum. It must, however, be mentioned here that the oxygen to carbon mole ratio in such metals should be more than unity in order to ensure that no residual carbon is left behind at the end of deoxidation. 

The residual carbon-carbon double bond in nitrile butadiene rubber (NBR) can be catalytically hydrogenated to yield its tougher and more stable derivative, hydrogenated nitrile butadiene rubber (HNBR).2 This class of specialty elastomer was developed to expand the range of operating environments possible for nitrile butadiene rubber NBR in environments that expose the rubber to chemical and thermal attack. 

It reacts similarly to the disodium salt [1], If heated to 150°C, it decomposes extensively, evolving gas which ignites in air owing to presence of pyrophoric carbon. The residual carbon is also highly reactive [2], The dry powder (lfom solution in liquid ammonia) may ignite if exposed to air as an extended layer, e.g. on filter paper [3],... 

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