Staging systems

The urea solution is evaporated in a two-stage system (99.8%) if the final product is prills, and a single-stage system (+95%) if granules are to be provided. 

FoUowiag Monsanto s success, several companies produced membrane systems to treat natural gas streams, particularly the separation of carbon dioxide from methane. The goal is to produce a stream containing less than 2% carbon dioxide to be sent to the national pipeline and a permeate enriched ia carbon dioxide to be flared or reinjected into the ground. CeUulose acetate is the most widely used membrane material for this separation, but because its carbon dioxide—methane selectivity is only 15—20, two-stage systems are often required to achieve a sufficient separation. The membrane process is generally best suited to relatively small streams, but the economics have slowly improved over the years and more than 100 natural gas treatment plants have been installed. 

Table 1. Flux Comparisons Between Batch and Staged Systems Operating on Cheese Whey...

FIG. 11-78 Typical two-stage system with two evaporating temperatures, flash-gas removal, and intercooling. 

Two-stage systems should be seriously considered when the evaporating temperature is below—20°C. Such designs will save on power and reduce compressor discharge temperatures, but will increase initial cost. 

Multistage Systems The majority of steam-jet systems being currently instaUed are multistage. Up to five stage systems are in commercial operation. 

Particle charging and collection can taltc place in different sections, as illustrated in Fig. 13.6. In this two-stage system, the collection of particles takes place in a region without gas ions, i,e the electric field is generated by the high-voltage electrode only. 

A typical pictorial flow diagram for the ammonia system is given in Figure 11-14 for a single-stage system and in Figure 11-15 for a two-stage ammonia system. 

Determine the approximate horsepower and condenser duty for the two-stage system of Figure 11-47. Note A simpler system omits the suh-cooler and smaller evaporator (see diagram on Figure 11-37). 

Refrigerant evaporating temperature Consider the 25MM Btu/hr —40°F independently as a simple two-stage system. Thus, condensing at +120°F... 

In a two-stage system, the vapors from the compressor s first stage discharge are partially condensed and flashed in an interstage drum. The liquid hydrocarbon is pumped forward to the gas plant, either to the high pressure separator (HPS) or directly to the stripper. 

Smaller items are tested in self-contained cabinets with a chamber the size of a large domestic refrigerator. Two-stage and three-stage systems are used, with R.13 in cascade at the lower end and R.22 for the high stage(s). 

The multi-stream multi-stage system is a valuable means for obtaining steady-state growth when, in a simple chemostat, the steady-state is unstable eg when the growth-limiting substrate is also a growth inhibitor. This system can also be used to achieve stable conditions with maximum growth rate, an achievement that is impossible in a simple chemostat (substrate-limited continuous culture). 

Despite the advantages of continuous cultures, the technique has found little application in the fermentation industry. A multi-stage system is the most common continuous fermentation and has been used in the fermentation of glutamic add. The start-up of a multi-stage continuous system proceeds as follows. Initially, batch fermentation is commenced in each vessel. Fresh medium is introduced in the first vessel, and the outflow from this proceeds into the next vessel. The overall flow rate is then adjusted so that the substrate is completely consumed in the last vessel, and the intended product accumulated. The concentration of cells, products and substrate will then reach a steady state. The optimum number of vessels and rate of medium input can be calculated from simple batch experiments. 

Figure 26 is the schematic diagram of the FFM designed by Lu (one of the present authors) et al. [9] in 1995. It consists of a stage system, circuitry controlling system, and computer controlling system. 

The National Kidney Foundation (NKF) developed a classification system for CKD (Table 23-11.1 The staging system defines the stages of CKD based on GFR level, but also accounts for evidence of kidney damage in the absence of changes in GFR, as in stage 1 CKD. The GFR is calculated using the abbreviated Modification of Diet in Renal Disease (MDRD) study equation ... 

An alternative classification, the Cierny-Mader staging system, is based on anatomic site and physiologic status of the patient.1 This classification scheme was developed for chronic osteomyelitis involving long bones and has limited application for small bones and digits. The detailed stratification has the greatest utility in clinical trials since it would permit comparison of treatment regimens in patients with diverse comorbidities and infection sites. 

Singletary SE, Allred C, Ashley P, et al. Revision of the American Joint Committee on Cancer staging system for breast cancer. J Clin Oncol 2002 20 3628-3636. 

The stage of colorectal cancer is determined by the TNM staging system and is the most important prognostic factor for patient survival. Stage I to III disease is curable, whereas patients with stage IV disease are treated with the goal of palliation. 

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