Compressors standard units

On those compressors where rotor dynamics can be a problem, which is on all but the standard units (even them sometimes) and reciprocaiiiit compressors, this is the point where the acceptance of the compressor for vibration and critical speed criteria should take place. Finding these in the field later is what the user and vendor want to avoid, and this is why ail the elaborate and careful work is done at the running test time,... 

Classifications 477. Standard Units 481. General Calculations 481. Reciprocating Compressors 484. Rotarv Compressors 487. Centrifugal Compiessors 493. Axial-Flow Compressors 494. 

Another example is the systematic analysis undertaken by Palsson et al. on combined SOFC and gas turbine cycles [36]. In combination with a robust and accurate 2-D SOFC model, the system-level model attempts to provide an unbiased evaluation of performance prospects and operational behaviours of such systems. The 2-D SOFC model was integrated into a process simulation tool. Aspen Plus , as a user-defined model, whereas other components constituting the system are modelled as standard unit operation models. Parametric studies can be carried out to gain knowledge of stack and system behaviour such as the influence of fuel and air flow rate on the stack performance and the mean temperature and the effects of cell voltage and compressor pressure on the system efficiency. The pressure ratio is shown to have a large impact on performance and electrical efficiencies of higher than 65% are possible at low-pressure ratios. 

The lubrication system for the turbine is designed to provide both lubrication and cooling. It is not unusual that in the case of many gas turbines the maximum temperatures reached in the bearing section is about 10-15 minutes after the unit has been shutdown. This means that the lubrication system should continue to operate for a minimum of 20 minutes after the turbine has been shutdown. This system closely follows the outline in API Standard 614, which is discussed in detail in Chapter 15. Separate lubrication systems for various sections of the turbine and driven equipment may be supplied. Many vendors and some manufacturers provide two separate lubrication systems One for hot bearings in the gas turbines and another for the cool bearings of the driven compressor. These and other lubrication systems should be detailed in the specifications. 

Probably the biggest single advantage of dry gas seals is getting rid of the seat oil. The seal oil system, even when part of a combined lube and seal system, is a complex assembly. With the dry gas seal, the lubrication oil system is all that is needed to service the compressor train bearings and, on turbine driven units, to also supply turbine control oil. As. ui aside, it makes feasible the dream long held by the compressor vendor of having a standardized lube system line. 

A process engineer s task is often to evaluate the performance of a compressor unit based on gas throughputs and terminal pressures. Since compressor stations are complex machines and operations, the analysis required is sophisticated and goes well beyond simple computations on a personal computer, although some preliminary evaluations can certainly be made. In this section we summarize the working expressions for standard compressor operations. Compressor operations can be categorized under three thermodynamic categories ... 

Here, we first discuss whether such semi-closure (which is introduced so that CO2 separation can be undertaken more easily) is likely to lead to higher or lower thermal efficiency, and in this discussion it is helpful to consider recirculation in relation to an air standard cycle (see Fig. 8.4). Fig. 8.4a shows a closed air standard cycle with unit air flow Fig. 8.4b shows an open cycle similarly with unit air flow and an air heater rather than a combustion chamber. The cycles are identical in every respect except that in the former the turbine exhaust air from the turbine is cooled before it re-enters the compressor. In the latter, the turbine exhaust air is discharged to atmosphere and a fresh charge of air is taken in by the compressor. The quantities of heat supplied and the work output are the same for each of the two cycles, so that the thermal efficiencies are identical. 

Typically, in specifying a unit, the suction and discharge pressures, capacity (MMsefd), inlet temperature, and gas properties are given. The actual sizing of the cylinders is left to the manufacturer from his specific combinations of standard cylinders, pistons, and liners. However, once a proposal is received from a manufacturer, sometimes it is beneficial to check the cylinder sizing and make sure that indeed the compressor will perform. Sometimes it is necessary to size a new cylinder for an existing compressor or to verify that an existing compressor will perform in a different service. 

Centrifugal compressor cases are classified as horizontally split or vertically split (Figures 12-40A-C). The 5th Edition, April, 1988, API Standard 617 refers to the horizontally split style as Axial Split and vertically split units as Radial Split The first terminology is more standard than that of the API-617. Figure 12-40D illustrates one flow arrangement for back-to-back internal flow, with the following advantages ... 

Figure 12-40A. Centrifugal compressor case types. These usually apply to multistage units rather than single-stage units. See Figures 12-39A and 12-39B. [Note API standards 617, April 1988, Par. 2.2.8.] (Used by permission Bui. 423, 1992. Dresser-Rand Company.)...

The spiral-lobe and helical-screw compressors are rotary positive-displacement machines and quite adaptable to a wide assortment of process and refrigeration gases. This class of equipment is usually built to comply with the American Petroleum Institute Standard 619. These units oper-... 

A small amount of nickel in the FCC feed has a significant influence on the unit operation. In a clean gas oil operation, the hydrogen yield is about 40 standard cubic feet (scf) per barrel of feed (0.07 wi /r ). This is a manageable rate that most units can handle. If the nickel level increases to 1.5 ppm, the hydrogen yield increases up to 100 scf per barrel (0.17 wt%). Note that in a 50,000 barrel/day unit, this corresponds to a mere 16 pounds per day of nickel. Unless the catalyst addition rate is increased or the nickel in the feed is passivated (see Chapter 3), the feed rate or conversion may need to be reduced. The wet gas will become lean and may limit the pumping capacity of the wet gas compressor. 

Mr. Kletz provides a story about a packaged unit containing a reciprocating compressor. The compressor was started in error. The discharge valve was in the closed position, and the pressure increased until the packing around the cylinder rod blew out. This compressor was equipped with a relief valve that was merely a sentinel to warn the operator to take action. The sentinel was incapable of relieving the full output of the equipment. It is not an acceptable design standard today, but this example supports the need for available process-safety information on all equipment. [2]... 

The gas turbine installed in the plant is an almost standard Typhoon from ABB Alstom Gas Turbines in Lincoln, England. Modified components are the combustors, the burners and the addition of an air bleed from the compressor, Furthennore, has a special design gas control module been developed to control the product gas, steam and nitrogen to the unit. 

Nowadays, the standard cryostats are closed-cycle helium refrigerators. They are commercially available. We use either the Displex Closed-Cycle System CSA from Air Products or the Closed-Cycle Compressor Unit RW 2 with Coldhead Base Unit 210 and Extension Module ROK from Leybold. These systems can run for thousands of hours with minimal maintenance. The sample holder can be cooled to temperatures from room temperature to about 10 K. A typical example of a closed-cycle helium matrix apparatus is shown in Figure 1.1. 

These pieces of equipment are also expensive to operate. With the industry standard price of compressed air at approximately 29 cents/1,000 cfm, oftentimes a new compressor is needed or the costs do not justify using the ionizers. At one company, the cost for operating compressed air ionizing units on a single line was 200,000 per year. 

The characteristics of the process wastewaters from each pretreatment sub-group are shown in Table 3. Daily wastewater flows are characterized as intermittent because some major unit processes, e.g., cheese and butter making, are batch, and because milk processing equipment must be shut down daily for sanitizing to maintain rigid health standards. Relatively clean water may be a substantial portion of the total wastewater from a dairy plant. These waters are from condensers, refrigeration compressors, milk coolers, and air conditioning systems. 

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