Dual temperature systems

Fig. 1. Simplified flow diagrams for H2S/H2O heavy water processes, (a) Dual-temperature system where the pressure is 1.90 MPa (b) siagle-temperature...

NOTE Dual-temperature systems provide both HW and chilled water functions and employ common piping for much of the system. Water temperatures range from 34 °F/1.1 °C up to perhaps 250 °F/121.1 °C. 

D-type WT boiler design Dual-amine technology program Dual-chelant programs Dual-temperature systems inhibitor requirements Ductile fracture... 

Dual Temperature Process. A unit of a dual temperature cascade is shown schematically in Figure 8. The dual temperature system operates on the principle that isotope exchange reactions, like all chemical reactions, change their equilibrium constants with temperature. The general, but far from universal (22), rule is that in systems with large isotopic... 

Hydrogen sulfide is conserved by returning depleted Hj S from the top of the cold tower to the bottom of the hot. Heat is conserved by heat exchange between hot and cold liquid and between hot and cold vapor. In principle, no materials other than feed water are consumed in the dual-temperature system energy consumption can be reduced by efficient heat exchange, with a lower bound set by the minimum required by thermodynamics for the separation. 

The detailed maimer in which the dual-temperature system effects separation will be explained in Sec. IIJ. That separation is possible can be made plausible by the simple qu tative considerations of Fig. 13.26. This represents one vessel containing cold water and a second containing hot water throu which water flows in series and through which hydrogen sulfide may be recirculated. 

Even though flow conditions for the dual-temperature system. Fig. 13.37, were chosen to give a minimum number of stages, the increase from 5.7 stages for the monothermal system to... 

Some fabrication processes, such as continuous panel processes, are mn at elevated temperatures to improve productivity. Dual-catalyst systems are commonly used to initiate a controlled rapid gel and then a fast cure to complete the cross-linking reaction. Cumene hydroperoxide initiated at 50°C with benzyl trimethyl ammonium hydroxide and copper naphthenate in combination with tert-huty octoate are preferred for panel products. Other heat-initiated catalysts, such as lauroyl peroxide and tert-huty perbenzoate, are optional systems. Eor higher temperature mol ding processes such as pultmsion or matched metal die mol ding at temperatures of 150°C, dual-catalyst systems are usually employed based on /-butyl perbenzoate and 2,5-dimethyl-2,5-di-2-ethyIhexanoylperoxy-hexane (Table 6). 

The potential for electrochemical corrosion in a boiler results from an inherent thermodynamic instability, with the most common corrosion processes occurring at the boiler metal surface and the metal-BW interface (Helmholtz double layer). These processes may be controlled relatively easily in smaller and simpler design boilers (such as dual-temperature, LPHW heating, and LP steam boiler systems) by the use of various anodic inhibitors. 

Dual-temperature and simple LPHW heating systems typically require 1,000 to 1,300 ppm as N02 (1,500-2,000 ppm as NaN02) when a standard nitrite/borate/TTA formulation is employed. (This is about twice the level required for cold and chilled water closed loop systems.)... 

Where molybdate/nitrite programs are employed in dual-temperature and simple HW heating systems, they typically require 150 to... 

In a similar way, electrochemistry may provide an atomic level control over the deposit, using electric potential (rather than temperature) to restrict deposition of elements. A surface electrochemical reaction limited in this manner is merely underpotential deposition (UPD see Sect. 4.3 for a detailed discussion). In ECALE, thin films of chemical compounds are formed, an atomic layer at a time, by using UPD, in a cycle thus, the formation of a binary compound involves the oxidative UPD of one element and the reductive UPD of another. The potential for the former should be negative of that used for the latter in order for the deposit to remain stable while the other component elements are being deposited. Practically, this sequential deposition is implemented by using a dual bath system or a flow cell, so as to alternately expose an electrode surface to different electrolytes. When conditions are well defined, the electrolytic layers are prone to grow two dimensionally rather than three dimensionally. ECALE requires the definition of precise experimental conditions, such as potentials, reactants, concentration, pH, charge-time, which are strictly dependent on the particular compound one wants to form, and the substrate as well. The problems with this technique are that the electrode is required to be rinsed after each UPD deposition, which may result in loss of potential control, deposit reproducibility problems, and waste of time and solution. Automated deposition systems have been developed as an attempt to overcome these problems. 

The synergism of a dual-catalyst system comprising of Pt/ZSM-12 and H-Beta aiming to improve the benzene product purity during transalkylation of aromatics has been studied. Catalyst compositions of the dual-catalyst system were optimized at various reaction temperatures in terms of benzene product purity and premium product yields. Accordingly, a notable improvement in benzene purity at 683 K that meets the industrial specification was achieved using the cascade dual-bed catalyst. 

Fig. 8.13 Schematic diagram of one stage of a GS dual temperature chemical exchange system...

Fluoridated apatite crystals can grow using the dual membrane system involving on the one hand a calcium acetate solution and on the other hand a phosphate solution at physiological temperature with a pH of 6.5. lijima et al. showed that the combination of fluoride ions, added to the phosphate solution, and amelogenin (a major protein in the enamel extracellular matrix), present in the reaction space between the two membranes, controlled the transformation of octacalcium phosphate (OCP) into fine rod-like fluoridated apatite crystals with habit, size... 

The problems associated with the multifunctional curing agents for CTPB and the resultant aging behavior of the cured polymers have led to a practical solution for curing binders and propellants—i.e., using mixed aziridines or a mixture of an aziridine and an epoxide. Such mixtures, when appropriately balanced, usually provide satisfactory mechanical behavior and high temperature stability. In dual curing systems such as MAPO and BITA or MAPO and a suitable multifunctional epoxide,... 

The chemical exchange system employed for lithium-6 enrichment is lithium amalgam and aqueous lithium hydroxide. It also employs paired dual-temperature columns. 

In the dual-cycle system, all steps take place in a single vessel. The cosolvent is first introduced from a separate module into the cleaning vessel at a selected temperature and atmospheric pressure and circulated around the work to dissolve the contaminant. Then the... 

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