The case study on n-octane production (Example 1.1) is used for illustration throughout the chapter.ħ.1 EXAMPLE ON N-OCTANE PRODUCTION A simple example that involves the production of n-octane (C8H18) is demonstrated (Foo et al., 2005), with detailed descriptions given in Chapter 1. The concept of simulation is based on sequential modular approach and follows the onion model for flowsheet synthesis (see Chapter 1 for details). This chapter aims to provide a step-by-step guide in simulating an integrated process flowsheet using SimSci PRO/II (Schneider Electric, 2015). Simply stated, the analyzer monitors the pressure and relates it to volume by tracking the crankshaft motion.Basics of Process Simulation With SimSci PRO/II Chien Hwa Chong Taylor’s University, Subang Jaya, Malaysia It was beyond the scope of this study to provide a rigorous assessment of electronic engine analyzer accuracy however, Table 2 shows excellent deadweight pressure indications that were recorded during a routine test using the digital type analyzer and a "factory-calibrated" pressure transducer. Both types of analyzers obtain pressure data by using strain-gauge type transducers. Another type of analyzer uses a digital computing device to calculate a table of volume increments as a function of crankshaft rotation. One type of analyzer simulates piston velocity, and thus volume, with voltage generators. P-V Simulation: The Method and its Advantages P-V Simulation: The Method and its Advantages Because the emphasis was on matching the horsepower indication of engine analyzers, the first question to be addressed was, how does an analyzer determine horsepower? The electronic analyzer simulates the indicated mean effective pressure (IMEP), and applies appropriate multipliers for speed and cylinder swept volume to model the horsepower. All previously used formulas and curves were eliminated as a fresh approach was sought. Accuracy with regard to calculated gas throughput was not considered important because maximum throughput is achieved as the load on the compressors is maximized.
A rough approximation of horsepower expended in inactive cylinder ends also was desired. Our goal was to develop a horsepower calculation method that matched E/CA test results within2% over a wide range of operating pressures and cylinder clearances. In early 1982, work was begun to develop a more precise method of predicting engine loads. Every suite of engine analyzer tests precipitated load revisions of 5 to 10%.
After operating the system for 3 years, most of the questions about loading accuracy remained unanswered. Typewritten loading tables were prepared on the basis of manufacturer's data adjusted for E/CA results. Further, the average suction pressure was declining by about 15 psi per month as a result of reservoir depletion. In this plant, it was mandatory that the operators be furnished with loading data because the suction pressure often varied by 50 psi owing to gas-demand fluctuations. 2 also reports problems of insufficient accuracy in the manufacturer's compressor loading data. Table 1 shows that significant differences were not limited to a narrow range of Operation. When new cylinders were installed on nine 2,000-hp units in 1977, discrepancies of more than 20% were seen between values from the manufacturer's load curves and the engine analyzer results. This practice, which is cost effective on the basis of reduced maintenance expense through early detection of worn or damaged parts, also verifies actual compressor load. These engine/compressors are tested several times annually by company technicians using electronic engine/compressor analyzer (E/CA) equipment. The Clark units include models designated TCV-10, TLA-8, TRA-8, and HBA-6T. The Engine Room 2 consists of 12 Clark integral engine/compressors totaling 23,000 hp. The Engine Room 1 houses nine 2,000-hp Cooper-Bessemer GMWA-8 integral compressors and six 1,350-hp GMVA-10 units, totaling 26,100 hp. Two large compressor installations at the plant provide boost service for much of the incoming gas. The King Ranch Gas Plant, located 50 miles southwest of Corpus Christi, TX, processes about 700 million cu ft/D of gas from fields in Kleberg and surrounding counties.
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