HAT cycle

De Ruyck et al. [lOJ proposed another variation of the EGT cycle, in an attempt to reduce the exergy los.ses involved in water injection (the REVAP cycle). Rather than introducing the complication of a saturator, De Ruyck proposed several stages of water heating (in an economiser, an intercooler and an aftercooler). The efficiency claimed for this cycle is only a little less than the HAT cycle. 

A modification of the HAT cycle has been proposed by Nakhamkin [11], which is known as the cascaded humid air turbine (CHAT). The higher pressure ratios required in humidified cycles led Nakhamkin to propose reheating between the HP and LP turbines. Splitting the expansion in this way is paralleled by splitting the compression, and enables the HP shaft to be non-generating, as indicated in Fig. 6.15. This implies that the capital cost of the plant can be reduced, but the cycle is still complex. 

Another water injection cycle proposed is the TOPHAT cycle [12] (see Fig. 6.16). As for the HAT cycle, the purpose is to introduce water into the cycle with low exergy loss and this is achieved by injecting water continuously in the compressor in an attempt to... 

Macchi et al. presented similar calculations for the HAT cycle based on comparable a.ssumptions (Fig. 6.20). As to be expected, they obtain efficiencies about 2% higher... 

Humid Air Turbine Cycle. One innovative improvement and modification of the I-STIG turbine cycle is the humid air turbine (HAT) cycle (37), which eliminates the use of the HRSG to generate steam. In the HAT cycle, a flue gas heat recuperator, replaces the HRSG and is used to preheat both humidified combustion air and water. 

Analysis of the HAT cycle integrated with coal gasification (called IG-HAT) shows promising results of 15% lower cost of electricity relative to conventional IGCC (37). 

This is principally due to significant capital cost savings because the HAT cycle avoids the expensive syngas coolers by effectively utilizing low-level heat from quench gasification. There is also a reduction in NO emission and slight improvement in thermal efficiency. 

The biggest challenge facing developers is the need for a combustion turbine that provides intercooling for higher-pressure (24-30 atmospheres) operation. In addition, the ratio of the air compressor mass flow to flue gas turboexpansion mass flow differs markedly from that of a conventional combustion turbine. Development of a new combustion turbine is difficult and quite expensive. However, recent analysis shows that the large aircraft-derived combustion turbines can be effectively modified for use in the HAT cycle (38). 

A Comparison of Humid Air Turbine (HAT) Cycle and Combined-Cycle Power Plants. Palo Alto, California Electric Power Research Institute, March 1991, EPRI lE-7300s. 

To this figure, some of the calculations carried out by various authors for wet cycles have been added RWI and HAT [9] REVAP [10] CHAT [11] TOPHAT [12],... 

Macchi et al. [9] made an extensive study of water injection cycles in their two classic papers and their results are worth a detailed study. Some of their calculations (for ISTIG, RWI and HAT) are reproduced in Figs. 6.18-6.20, all for surface intercooling (parallel calculations for evaporative intercooling are given in the original papers). 

The previous discussion has shown us how to calculate the total number of possible cyclic states. We also know, from Lemma 2, that all cycle lengths must divide the maximal cycle length Hiv obtain the exact number of distinct cycles and their lengths takes a little bit more work. If flw prime, we know that the only possible cyclic lengths are 1 and It can then be shown that only the null configuration is a fixed point unless N is some multiple of 3, it which case there are exactly four distinct cycles of length one. If Hat i ot prime, there can exist as many cycles as there are divisors of Although there is no currently known closed form... 

In agreement with the aberrant HDAC/HAT activity equilibrium in cancer, HDAC inhibitors have been shown to induce cell-cycle arrest, terminal differentiation and/or apoptosis in a broad spectrum of human tumor cell Unes in vitro, to inhibit angiogenesis and to exhibit in vivo antitumor activity in human xenograft models in nude mice [10-12]. Several HDAC inhibitors are in advanced stages of development and antitumor activity has been observed in hematological malignancies at doses that were well tolerated (Sect. 3). 

Curcumin has also been found to interrupt the cell cycle, to have cytotoxic effects, and to have a role in antiproliferation and the induction of apoptosis in a hepatocarcinoma cell line. Curcumin is a potent inhibitor of phenol sulfotransferase (SULT1A1) in human liver and extrahepatic tissues [Vietri et al., 2003]. Curcumin inhibited the interleukin-6 (IL-6) production, histone acetyltransferase (HAT) activity, and API activation [Chen et al., 2003a] and prevented cell death and apoptotic biochemical changes, such as the... 

Scheme 16 Coupled cycles for Rh-catalyzed HAT to P-titanoxy radicals...

The use of hydrogen as terminal reductant has been accomplished by its activation with transition metal complexes. The resulting weak M-H bonds can be used in both radical generation and reduction through HAT. In this manner, conceptually novel radical chain reactions, such as hydrogen mediated cyclizations, or metal catalyzed processes with coupled catalytic cycles for radical generation and reduction, have been realized. The latter transformations are especially attractive for enantioselective synthesis. 

The cardinal difference between the associative and dissociative hydrofoimyla-tion cycles is that in the associative cycle, the rhodium never has fewer than two tertiary phosphine ligands, and consequently it is sterically more demanding and would, therefore, be expected to strongly favour a more linear product formation. This is borne out by the experimental observation (hat increasing the tertiary phosphine-rhodium ratio increases the system towards the formation of linear-products. 

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