Cycle attracting

Possible solutions - Harvesting has much in common with brood-stock acquisition, in that it deals with concentrating and capturing sexually mature, i.e., marketable animals. In fact, the brood-stock is often sorted out from the harvested animals to start a new culture cycle. Attractive chemical cues, such as sex pheromones involved in chemical communication between adult crustaceans, might be integrated into the aforementioned harvesting techniques, to increase the efficiency and rapidity of animal capture and to reduce the stress and loss of animals associated with this action. For example, such chemical cues might be released from traps or the collection basin. 

The eady use of natural gas reHed on its availabiHty from small, local, shallow fields. This frequendy created a chaotic cycle of events consisting of the discovery of a field, followed by the development of a local distribution system which, in turn, attracted new industries and other customers to the... 

Gas turbine-based power plants, particularly natural gas-fired cogeneration and combined-cycle faciUties, have proven to be highly rehable, efficient, and environmentally attractive. Advances in machine design, more efficient plant integration, and optimistic forecasts for the availabiUty of affordable natural gas worldwide have boosted the appeal of these systems for both base-load and peaking service. 

Although the continuous-countercurrent type of operation has found limited application in the removal of gaseous pollutants from process streams (Tor example, the removal of carbon dioxide and sulfur compounds such as hydrogen sulfide and carbonyl sulfide), by far the most common type of operation presently in use is the fixed-bed adsorber. The relatively high cost of continuously transporting solid particles as required in steady-state operations makes fixed-bed adsorption an attractive, economical alternative. If intermittent or batch operation is practical, a simple one-bed system, cycling alternately between the adsorption and regeneration phases, 1 suffice. 

Water injection, or steam injection systems, are being used extensively to augment power. Corrosion problems in the compressor diffuser and combustor have not been found to be major problems. The increase in work and efficiency with a reduction in NO makes the process very attractive. Split-shaft cycles are attractive for use in variable-speed mechanical drives. The off-design characteristics of such an engine are high efficiency and high torque at low speeds. 

Only one melamine molecule is formed from six urea molecules, whilst three molecules of ammonia carbamate are formed. Whilst this can be recycled to urea the conversion from urea to melamine per cycle is at most 35%. Both the main route and the recycling operation involve high pressures and the low process efficiency offsets some of the apparent economic attractions of the route compared to those from dicy . 

The process is attractive for a number of reasons. Firstly, since it is a low pressure process the moulds are generally simple and relatively inexpensive. Also the moulded articles can have a very uniform thickness, can contain reinforcement, are virtually strain free and their surface can be textured if desired. The use of this moulding method is growing steadily because although the cycle times are slow compared with injection or blow moulding, it can produce very large, thick walled articles which could not be produced economically by any other technique. Wall thicknesses of 10 mm are not a problem for rotationally moulded articles. 

The life cycle cost of a process is the net total of all expenses incurred over the entire lifetime of a process. The choice of process chemistry can dramatically affect this life cycle cost. A quantitative life cycle cost cannot be estimated with sufficient accuracy to be of practical value. There is benefit, however, in making a qualitative estimate of the life cycle costs of competing chemistries. Implicit in any estimate of life cycle cost is the estimate of risk. One alternative may seem more attractive than another until the risks associated with product liability issues, environmental concerns, and process hazards are given due consideration. Value of life concepts and cost-benefit analyses (CCPS, 1995a, pp. 23-27 and Chapter 8) are useful in predicting and comparing the life cycle costs of alternatives. 

Clearly, these figures suggest that the plant is very sensitive to the amount of flue gas recycled. There appears to be no full parametric or economic calculation published in the literature for this FG/TCR cycle, which suggests that it has not been considered as an attractive option. 

The IGCC cycle was described in Section 7.4.2. Obviously, there is an attraction in burning cheap coal instead of expensive gas, but the IGCC plant will discharge as much carbon dioxide as a normal coal burning plant unless major modifications are made to remove the CO2 (Table 8.IE). 

In particular, the cycles involving fuel or oxidant modification do not look sufficiently attractive for their development to be undertaken, with the possible exception of the multiple PO combustion plant proposed by Harvey et al. [14]. The Matiant plant has the advantage of relatively simple CO2 removal and high efficiency and may prove to be attractive, but it again looks complex and expensive. 

In open cycle, the diesel has the higher efficiency, making it more attractive for light fuel oils. However, in combined cycle, the gas turbine often has the highest overall efficiency, but there is the penalty associated with the additional cost for boiler and turbine. Nevertheless, unless the prime fuel is of low cost, the use of combined-cycle gas turbine plant will prove to be the more economic. 

The overall efficiency of the condensing thermal cycle, as discussed, is dictated primarily by the steam conditions used. There are some small industrial stations with outputs up to 2 MW using shell-type boilers for the generation of steam. Here the steam conditions are limited to approximately 17 bara and 250°C. For larger installations these conditions will rise sharply when watertube boilers become attractive and more common steam conditions are of above 60 bara and 540°C. 

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