Power train

Rotating machinery usually performs efficiently if it works under design point conditions. However, off-design conditions require a predictive model of the machine s performance. In a FCC power train system, mass flow deviation is quite common for adjusting production capacity to meet the requirements of petrochemical product markets. 

There are many reasons for significant investment in FCC power trains and, thus, power train maintenance. These power recovery machines handle catalyst-laden gas at high temperature. Because the recovery system is connected to the processing plant, the steam pipe network and the electrical power grid, a power train upset is likely to rapidly extend from the FCC unit to the entire plant. 

It would be an understatement to say that the gas expander turbine forms a major part of the power train. Evaluating off-design performance for the expander installed in the Sinopec Jinan Oil Refinery is presented as an example of an appropriate evaluation method. It should be noted that calculations are based on actual field measurements and plant experience. 

The power train (Figure 8-10) was eommissioned in May 1989. Table 8-1 provides data on the maehine in question. Tables 8-2 and 8-3 show flue gas analysis from the regenerator to the gas expander turbine inlet and the relevant metallurgy, respeetively. There are many possible failure modes in gas expanders, whieh inelude erosion, eatalyst deposition, and exeessive meehanieal vibration. Obviously, these faetors may also eause power loss, and some power trains do indeed fall short of produeing the expeeted power. Nevertheless, in some eases operation at off-design expander system eonditions eould be the primary eause of performanee defieieneies. 

Specification of power train in Sinopec Jinan oil refinery... 

In a hot gas expander, the major problems associated with catalyst fines are centered on erosion of components and particulate plugging. Either problem can cause machine vibration and sometimes power train emergency shutdown. Because many failures have resulted from these factors, machinery manufacturers recommend that the maximum permissible solids concentration upstream of an expander not exceed 200 ppm. It is further stipulated that 97% of the particles be smaller than 10 p. Allowing concentrations of 160 ppm with 95% of the particle less than 10 p is considered reasonable. 

The power train consists of an HP and LP expander arranged in series that drives the motor/generator, which in this mode is declutched from the compressor train and is connected by clutch to the HP and LP expander train. The HP expander receives air from the cavern that is regeneratively heated in a recuperator utilizing exhaust gas from the LP expander, and then further combusted in combustors before entering the HP expander. The... 

The equations and performance parameters for all the major components of a power train must be corrected for ambient conditions and certain parameters must be further corrected to design conditions to accurately compute the degradation. Therefore, to fully compute the performance, and degradation of the plant and all its components, the actual, corrected, and transposed to reference conditions of critical parameters must be computed. 

The great disadvantage of any battery, however advanced, for automobile power trains, is the long time required to charge a battery, and in my view this will be decisive. Here, fuel cells have an enormous advantage over batteries, and so I turn to fuel cells next. 

Consider a plant having two power trains A and B with diesel generators DA connected to... 

Figure 4-9. Power train on a drawworks with accessories.

A typical power train for such a generating station is shown in Figure 15.35. A further refinement, capable of improving cycle efficiency by several percentage points,... 

Power recovery trains recover energy from the flue gas. The FCC starts to resemble a large jet engine air is compressed into a combustion zone and expanded across a turbine. Power recovery increases the efficiency of the unit but adds one more mechanical device to an already long list. Since they are too big to bypass, power trains need to be as reliable as the rest of the unit. 

A common metric used to compare different alternative fuels and power trains to a benchmark fuel and vehicle are C02 avoidance costs, which take into account cost of fuel, infrastructure and vehicles. However, depending on the calculation methods, and system boundaries, as well as the assumptions about C02 emissions reduction achievable and vehicle prices relative to the benchmark, significant variations in C02 avoidance costs are possible. For this reason, the discussion about C02 avoidance costs is not addressed in great detail. 

Today, the power train costs of fuel-cell vehicles are still far from being competitive. They have the largest influence on the economic efficiency of hydrogen use in the transport sector and the greatest challenge is to drastically reduce fuel-cell costs from currently more than 2000/kW to less than 100/kW for passenger cars. On the other hand, fuel-cell drive systems offer totally new design opportunities for... 

The power train on the extruder was also limiting the rate of the process. The extruder was driven by a 190 kW motor with a maximum speed of 1750 rpm and a maximum current of 262 A. The motor was directly coupled to a gearbox with a ratio of 13.91, providing a maximum screw speed of 125 rpm. The maximum torque available to the screw from the drive system was 14,200 Nm. As will be shown later, this gearbox-motor combination did not provide a high enough torque to the screw for this process. 

Hohlein, B., von Andrian, S., Grube, Th., Menzer, R. 2000. Critical assessment of power trains with fuel-cell systems and different fuels. J Power Sources 86 243-249. 

The DMFC, based on a polymer electrolyte fuel cell (PEFC), uses methanol directly for electric power generation and promises technical advantages for power trains. The fuel can be delivered to the fuel cell in a gaseous or liquid form. The actual power densities of a DMFC are clearly lower than those of a conventional hydrogen-fed polymer electrolyte fuel cell. In addition, methanol permeates through the electrolyte and oxidizes at the cathode. This results in a mixed potential at the cathode (Hohlein et al., 2000). 

There is now a great interest in developing different kinds of fuel cells with several applications (in addition to the first and most developed application in space programs) depending on their nominal power stationary electric power plants (lOOkW-lOMW), power train sources (20-200kW) for the electrical vehicle (bus, truck and individual car), electricity and heat co-generation for buildings and houses (5-20 kW), auxiliary power units (1-100 kW) for different uses (automobiles, aircraft, space launchers, space stations, uninterruptible power supply, remote power, etc.) and portable electronic devices (1-100 W), for example, cell phones, computers, camcorders [2, 3]. 

HYTRAN is a program for developing and integrating components and sub-systems into a direct H2 PEM power-train (80 kW) and APU Diesel re-formulate PEM (10 kW). The research consortium includes about 20 partners including the EU-wide car industry. 

Many fuel cell systems have been developed since the first discovery of Sir William Grove. Fuel cell systems can produce electricity from several fuels (hydrogen, natural gas, alcohols, etc.) for many applications stationary power plants, power train sources, APU, and electronic portable devices, with nearly the same energy efficiency (around 40% in electric energy), irrespective of their size (from tens of MW for power plants to a few W for portable electronics). 

Fig. 13.32. Series fuel cell-battery hybrid power train model. The two-way energy flow between the drive motor and electric bus indicates the potential for regenerative braking. (Reprinted with permission from Research and Development of Proton-Exchange-Membrane (PEM) Fuel Cell System for Transportation Applications, Phase I. Final Report, prepared for the U.S. Dept, of Energy by General Motors, 1996, Fig. 3.5.2.1.)...

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