Ash Impurities Research Articles

Dissolution of carbon from alumina-carbon mixtures into liquid iron: Influence of carbonaceous materials

Due to their excellent thermal shock and wear resistance at high temperatures, alumina-carbon based refractories are used extensively in the steel industry. A clear understanding of factors affecting the dissolution of carbon from refractories is of crucial importance, as carbon depletion from the refractory can significantly deteriorate refractory performance and metal quality. Atomistic simulations on the alumina-graphite/liquid iron system have shown that nonwetting between alumina and liquid iron is an important factor inhibiting the penetration of liquid metal in the refractory matrix and limiting carbon dissolution. This study investigates the role played by the carbonaceous material in the dissolution of carbon from the refractory composite. Two carbonaceous materials, namely, petroleum coke and natural graphite, respectively, containing 0.35 and 5.26 pct ash, were used in this study. Substrates were prepared from mixtures of alumina and carbon over a wide concentration range. Using a sessile drop arrangement, carbon pickup by liquid iron from alumina-carbon mixtures was measured at 1550 °C and was compared with the carbon pickup from alumina-synthetic graphite mixtures. These studies were supplemented with wettability measurements and microscopic investigations on the interfacial region. For high alumina concentrations (>40 wt pct), carbon dissolution from refractory mixtures was found to be negligible for all carbonaceous materials under investigation. Significant differences however were observed at lower alumina concentrations. Carbon dissolution from alumina-petroleum coke mixtures was much lower than the corresponding dissolution from alumina synthetic graphite-mixtures and was attributed to poor wettability of petroleum coke with liquid iron, its structural disorder, and the presence of sulfur. Very high levels of carbon dissolution, however, were observed from alumina-natural graphite mixtures, with carbon pickup by liquid iron from mixtures with up to 30 wt pct alumina reaching saturation. A sharp reduction to near zero levels was observed in the 30 to 40 wt pct alumina range. Along with implications for commercial refractory applications, these results are discussed in terms of material characteristics, interactions between ash impurities and alumina, and formation of complexes in the interfacial region.

The effect of ash impurities on coal gasification kinetics

The effect of ash impurities on coal gasification kinetics

Cost Functions and Nonlinear Prices: Estimating a Technology with Quality-Differentiated Inputs

The paper is concerned with developing a production theory for the case when some inputs have nonlinear prices because the price depends on endogenous quality. This involves extending the notion of a cost function to the case where nonlinear prices are parameters of costs. After developing the appropriate theory, we apply our results to the case of coal-fired electric power generation where fuel quality depends on sulfur and ash impurities. Environmental regulations induce a negative value on sulfur whereas ash impurities degrade performance and thus reduce production possibilities. A number of empirical results emerge, including significant rates of technological change that are sulfur and ash saving though capital using. This change may explain in part the recent drop in the price of sulfur allowances in the United States.

PRODUCTION OF ENRICHED ?-LACTOGLOBULIN AND ?-LACTALBUMIN WHEY PROTEIN FRACTIONS

This is a process based on (1) 90% volume reduction of whey by ultrafiltration, (2) partial demineralization of the UF retentate by electrodialysis or diafiltration, (3) pH adjustment of the UF retentate before and after demoralization to pH 4.65, and (4) centrifugation of the retentate produced β-lactoglobulin-enriched fractions containing 33% of the original acid whey protein and 17% of the original sweet whey proteins. Lactose and ash impurities in the β-lactoglobulin-enriched fraction were reduced by 18% by resuspending the pellet in distilled water at pH 4.65 and recentrifuging. Diafiltration of the α-lactalbumin-enriched fraction with 2, 4 and 6 volumes of distilled water reduced the lactose and ash content of this fraction by 53%, 62% and 81%, respectively. Gel electrophoresis patterns of the two protein enriched fractions confirmed selective enrichment of β-lactoglobulin or α-lactalbumin in each fraction.

A method of removing helium ash and impurities from fusion reactors

By injecting streams of small pellets through the edge of a reactor plasma, helium ash and other impurities can be captured and removed from the reactor. Calculations show that sufficient pumping capacity is available to remove 1021 He/s and that the equilibrium density of pellet material in the plasma is probably tolerable. If successful, this method of ash removal and impurity control simplifies reactor design considerably.

Characteristics of graphite and cast iron particle dissolution in iron during sintering

1. The dissolution of graphite in iron may take place with the formation of a liquid phase; the temperature at which this phase appears is determined by the amount of ash impurities in the graphite. 2. The pearlite produced as a result of impregnation of iron with carbon forms discrete fields arranged in directions of preferential diffusion of carbon into iron rather than a continuous zone around the periphery of the impregnation source. 3. The appearance of a large quantity of a liquid phase accompanying the sintering of iron with a high-ash graphite is chiefly responsible for the formation of structurally free cementite.

Low-temperature method of de-ashing petroleum coke

1. A method of low-temperature de-ashing of petroleum cokes with nitric acid has been studied. 2. Upon prolonged treatment of petroleum cokes with nitric acid it is possible to attain practically complete removal of ash impurities from them. 3. A scheme in principle has been suggested for a process of de-ashing petroleum coke.

Study of structure formation during sintering of iron-graphite alloys

1. Nonuniform saturation of austenite by carbon from graphite during sintering is the main cause of the anomalous structure of iron-graphite cermet alloys. The relatively high contents of ash and other impurities in the available graphite have an adverse effect on the structure of sintered alloys and impair their mechanical properties. 2. The low rate of diffusion during sintering is another cause of the anomalous structure of the iron-graphite alloys. It is desirable to search for an apply such activating admixtures that would speed up the diffusion of carbon and smooth out the microstructure. 3. The circumstance that the nonuniform concentration of carbon iron-graphite cermet products causes the pearlitic conversion to proceed by a mechanism differing from that in molten steels is also responsible for the anomalous structure. 4. Observations on iron-copper-graphite alloys during heating from room temperature up to the melting point have shown that a liquid copper phase does not form in mixtures with a copper content within the solubility range in austenite. Consequently, sintering of these mixtures takes place in the solid phase.