Balance point

Thermochemistry. From an overall heat and mass balance point of view, the main chemical reactions of the blast furnace include oxidation of carbon in the zone in front of the tuyeres (raceway) to give CO plus heat. 

FIG. 11 96 Balance points of compressor and condenser determines performance of condensing unit for fixed temperature of condenser cooling fluid (flow rate and heat-transfer coefficient are constant). 

Exploitation of boundaiy curvature for breaking azeotropes is veiy similar to exploiting pressure sensitivity from a mass-balance point of view, and suffers from the same disadvantages. Separation schemes have large recycle flows, and in the case of minimum-boiling azeotropes, the recycle streams are distillates. However, in the case of maximum-boihng azeotropes, these recycles are underflows and... 

Involved in producing the curves for Figs. 29-53 and 29-55 is a calculation of the so-called balance point at which the flow and revolutions per minute required by the recovery unit match those provided by the pump. If the recovery turbine is the sole driver (as for the lean pump of Fig. 29-54), both the speed and the brake horsepower of the recoveiy turbine and its driven pump must be the same at the so-called balance point. If there is a makeup driver and the recovery unit has available to it just the flow from the pump that it is driving, as for the pump of Fig. 29-56, then the speea ana capacity must match at the balance point. 

Example 2 Units for a Power Recovery System The scheme of Fig, 29-52 and the actual units supplied (Figs, 29-58 and 29-59) will he used for purposes of illustration. Since this case has the recovery unit as the sole driver, the balance point is set hy speed and horsepower. 

The same procedure maybe used at other pump flows to permit plotting the series of balance-point curves as has been done in Fig. 29-61. From such curves, one can establish the maximum lean pump at any total tower outflow, and combining this with the semilean-pump performance curve results in Fig. 29-55. Bypass flow plotted in Fig. 29-55 is obtained by adding simultaneous lean- and semilean-pump flows and subtracting the recovery pump-turbine flow required to make the balance point at that lean-pump flow. 

Heat balance The thermal balance that occurs in a building when the heat gains equal the heat losses. Also known as balance point or break-even point. 

The pressure drop remains essentially constant as long as the liquid flow on tray remains steady during the period point A to point B on the diagram (the open balance point) [201]. At point B all valves are completely open off their seats, but are on the verge of closing and may be oscillating from open to closed. At point B the vapor velocity through the holes, opened balance point is ... 

Figure 8-148. Typical operating valve tray pressure drop profile. Valves start to open at A, the closed balance point. Used by permission, Klein, G. F. Chem. Eng. V. 89, No. 9 (1982) p. 81 all rights reserved.

Vpt, B = vapor velocity through holes, open balance point, ft/sec... 

Coefficients for the Closed and Open Balance Point Equations Equations 8-311 and 8-312... 

The failure to identify the necessary authigenic silicate phases in sufficient quantities in marine sediments has led oceanographers to consider different approaches. The current models for seawater composition emphasize the dominant role played by the balance between the various inputs and outputs from the ocean. Mass balance calculations have become more important than solubility relationships in explaining oceanic chemistry. The difference between the equilibrium and mass balance points of view is not just a matter of mathematical and chemical formalism. In the equilibrium case, one would expect a very constant composition of the ocean and its sediments over geological time. In the other case, historical variations in the rates of input and removal should be reflected by changes in ocean composition and may be preserved in the sedimentary record. Models that emphasize the role of kinetic and material balance considerations are called kinetic models of seawater. This reasoning was pulled together by Broecker (1971) in a paper called "A kinetic model for the chemical composition of sea water."... 

As an indispensable source of fertilizer, the Haber process is one of the most important reactions in industrial chemistry. Nevertheless, even under optimal conditions the yield of the ammonia synthesis in industrial reactors is only about 13%. This Is because the Haber process does not go to completion the net rate of producing ammonia reaches zero when substantial amounts of N2 and H2 are still present. At balance, the concentrations no longer change even though some of each starting material is still present. This balance point represents dynamic chemical equilibrium. 

Thus, the effect of the spin inversion would be to shift the balanced point by 8z = z o — z0. In order to estimate the shift 8z, we note that the field times the field gradient B(dB/dz) should shift by... 

Fortunately, our interest in micro-constituents in the seawater both from the environmental and the nutrient balance points of view has coincided with the availability of advanced instrumentation capable of meeting the analytical needs. 

In the equilibrium shown opposite, the see-saw is not moving and a balance point has been achieved. 

Heat balances occur at the intersection of the heat generation curve and the heat removal line (points C and D). Stable operation will occur at point C. A reaction temperature lower than point C will result in self-heating up to point C because the heat generation rate exceeds the heat removal rate. At temperature Tb, the heat removal rate exceeds the heat generation rate, so the reaction temperature will fall until point C is reached. Although point D is a heat balance point, no stable operation is possible here a temperature slightly lower than that at point D will result in a decrease in reactor temperature to... 

Single-phase operation moves the rotor from 0°, to 90°, to 180°, to 270°, and to 360°, whereas the two-phase mode uses adjacent pairs of electromagnets so that rotor comes to a balance point between them, pulling the rotor from 45°, to 135°, to 225°, and to 315°. With pairs of electromagnets activated, the torque is increased. The half-step mode is a combination of both single phase and two phase, pulling the rotor from... 

There are unusual hazards associated with partial desolvation of crystalline solvated oxosalts, notably perchlorates. This may be because desolvation causes the oxygen balance to approach the zero balance point and maximum energy release potential. A similar effect has also been seen with an hydrated salt. 

While these contending forces will no doubt continue to contend, and to confuse the public, we should hope that mainstream science and thoughtful risk management policies will prevail. The risk assessment framework is central in the continuing search for the right balance point in these debates. 

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