Hydrogen Pinch

Hydrogen pinch, applications of, 20 764 Hydrogen polysulfides, 23 568, 639-640 Hydrogen processing, 12 404 15 217 Hydrogen-producing reactions, 13 766-767 Hydrogen product oxidation, in styrene manufacture, 23 343... 

Hydrogen Pinch Technology has been applied commercially by several companies including AspenTech, BP-Amoco, Engineers India, Exxon, ICI, Linnhoff-March, M.W. Kellogg and UOP.44-45... 

Hydrogen is today a major product because its large-scale application in refining and from the perspective of fuel cells for the automotive industry. Hydrogen Pinch method has been developed to optimise the use and production of hydrogen in the context of integrated sites (Chapter 11). 

At this point we should be able to begin process engineering of the proposed re-use project. However, if we were to do so we would find that the simulated benefits ate very much lower than those predicted by the optimiser. This is due to another major limitation of the hydrogen pinch approach, its assumption of a binary mixture. 

Consider two hydrogen streams, each of 85 mol% purity. The first is ethylene plant export, containing almost 15% methane. The second is catalytic reformer export, containing roughly equal amounts of methane, ethane and propane, plus small amounts of heavier material. Hydrogen pinch techniques cannot differentiate between these streams, and would identify no penalty or benefit from switching between them as a source of make-up gas. Yet in reality the ethylene plant gas would require operation with a much... 

As temperatures decrease, closer temperature approaches are needed in the heat exchangers to achieve low energy requirements. Consequendy, temperature pinches in Hquid hydrogen plants range from 1 degree K at 20 K to 6 degrees K at 300 K. 

A 250-ml flask is charged with 28 g (0.20 mole) of 2-acetyIcyclohexanone and 25 g (0.22 mole) of 30% hydrogen peroxide in 100 ml of /-butyl alcohol. The solution is refluxed for 3 hours, cooled, and a pinch of palladium on charcoal (10%) is cautiously added. The mixture is refluxed for an additional hour to decompose excess peroxide. The cooled mixture is then filtered through celite, and the volume is reduced by removal of /-butyl alcohol and water at reduced pressure. Distillation of the residue affords about 85% of cyclopentanecarboxylic acid, bp 59-6271 rnm, 123727 mm, 215-21671 atm. 

An example of this kind, in which the energy and angular momentum of the two critical points coincide, occurs for the hydrogen atom in crossed electric and magnetic helds (see Section IVC). The pinched torus then has two pinch points. 

The purge gas from a petrochemical process is at 25°C and contains a mole fraction of methane of 0.6, the balance being hydrogen. This purge gas is to be burnt in a furnace to provide heat to a process with a cold stream pinch temperature of 150°C (A= 50°C). Ambient temperature is 10°C. 

Discussions on how to increase the hydrogen generation efficiency therefore often focus on how to maximise the temperature that can be used by the process, whether by maximising the HTR outlet helium temperature or by reducing pinches in heat exchangers. On the lower end of the secondary helium temperature spectrum, the importance of the helium return temperature is often overlooked. However, as a component of the average heat source temperature, it must, according to the Carnot principle, have an influence on the efficiency. 

Conversely, would the GA process be compatible with CEA secondary helium The answer is yes, but the overall production of the HTR coupled plant would be lower. Indeed, one could say that the GA Q(T) curve, as it is, is compatible with the CEA s helium Q(T) curve in both processes, secondary helium leaves Section II at a temperature around 600°C. However, this coupling implies the presence of a pinch point at the end of Section II which precludes increasing the helium flow rate, and hence the hydrogen production rate. Furthermore, setting the helium return temperature to 400°C implies that its heat content between 600°C and 400°C must be used in some way. 

Thirty grams of pure iron powder (0.54 mol) is placed in the bottom of a three-necked 2-1. flask equipped with (1) a reflux condenser with a stopper and small glass tube or Bunsen valve at the terminal end to allow venting of the hydrogen and to minimize entrance of air into the system (2) a siphon linej with a glass-wool plug as a strainer, filled with wTater and closed with a stopcock or pinch clamp until needed and (3) a separatory funnel. Twelve hundred milliliters of distilled water and 100 ml. of 45 % formic acid are introduced into the flask. The contents are boiled until... 

To 10 cc. of a 3 per cent solution of hydrogen peroxide in a test tube, add a pinch of powdered manganese dioxide. Note that a vigorous effervescence ensues and that the escaping gas will cause a glowing splinter to burst into flame. 

Around the same time as this, Reinhoudt developed a calix[4]arene system with only two urea or thiourea functionalities attached on opposite faces 70-72 [167]. These less substituted systems display both inter- and intramolecular hydrogen bonding as a result of the calixarene adopting a pinched cone conformation (demonstrated by the use of NOESY NMR). In some spectra it is impossible for the connectivities to be made within a single molecule, so the only possibility left is that dimerisation occurs. As with the initial experiments of Rebek and Bohmer, the extent of hydrogen bonding was observed to be solvent dependent. Concentration dependant FTIR was also used, to observe the effects on the NH stretching vibrations, but no concentration dependence was observed. Of the three urea derivatives used, only 72 showed no evidence of dimerisation... 

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