Main steam

If the total heat consumed is from an external utility (e.g., mains steam), then a high efficiency is desirable, even perhaps at the expense of a high capital cost. However, if the heat consumed is by recovery from elsewhere in the process, as is discussed in Chap. 15, then comparison on the basis of dryer efficiency becomes less meaningful. 

Steam from the steam generator exits containment through a main steam isulaiion valve (MSrV) to drive the turbine. When most of the energy in the steam has been removed by the turbine, the steam is condensed to liquid and returned to the steam generator by the feedwater puntp. The heat removed by the condenser goes to the heat sink. 

Figure 6,1-2 is a simplified illustration of a BWR. The pressure of the moderator-cooling water at about half the pressure in a PWR forms steam as it flows upward through the core. Steam passes through a moisture separator (shown as vertical lines just above the core) exits the containment through Main Steam Isolation Valves (MSIV) drives the turbine and generates electricity. After the steam is cooled by the turbine, it is condensed, and pumped back to the reactor by the feedwater pump. 

Valve Arrangement of Auxiliary Feedwater System and Main Steam System during Shutdown - the auxiliary feedwater system has six MO Vs in the flow path to the steam generators and the main steam nonreturn valves are normally closed during shutdown. These valves depend on offsite power and are difficult to manually open. 

Piping system Main steam Process steam Feedwater Raw water Treated water Potable water Aux. cooling system Firefighting system Clarified water Filtered water Water-intake system Circulating-water system Chemical dosing Station drains Fuel oil Fuel gas... 

The pressure gauge and associated shut-off valve, the boiler vent cock valve, main steam stop valve, and safety valve can be observed rising above the crown sheet of a FT boiler (the highest point of the boiler), normally in a line running the length of the boiler. 

Automatic NRVs act like check valves and cut out the boiler if its pressure falls below the main steam-header pressure. The installation of an automatic NRV may require the provision of a bypass pressure equalizing line and a pressure equalizing valve. 

BW containing some level of contaminant that is entrained and passes with the steam into the main steam-header. Carryover is always detrimental to the steam cycle process and is primarily caused by BW priming (surging), gulping, misting, or foaming. 

A steam heating line used to warm up the main steam line and equalize the pressure around the main steam stop valve. 

A drain line used to remove condensate from the main steam line. Freeboard ... 

Example 3.5 A 1-in i.d coiled tube, 57 m long, is being used as a tubular reactor. The operating temperature is 973 K. The inlet pressure is 1.068 atm the outlet pressure is 1 atm. The outlet velocity has been measured to be 9.96 m/s. The fluid is mainly steam, but it contains small amounts of an organic compound that decomposes according to first-order kinetics with a half-life of 2.1s at 973 K. Determine the mean residence time and the fractional conversion of the organic. 

Main steam throttle valves fully closed 4,686... 

Pneumatic actuators are normally used to control processes requiring quick and accurate response, as they do not require a large amount of motive force. However, when a large amount of force is required to operate a valve (for example, the main steam system valves), hydraulic actuators are normally used. Although hydraulic actuators come in many designs, piston types are most common. 

It was observed that the water content does not influence ethylene formation. When 5% Rh is added to alumina, the main steam reforming reaction occurs above 460 °C and the products include hydrogen, carbon dioxide, carbon monoxide and methane. 

Nuclear Boiler Assembly. This assembly consists of the equipment and instrumentation necessary to produce, contain, and control the steam required by the turbine-generator. The principal components of the nuclear boiler are (1) reactor vessel and internals—reactor pressure vessel, jet pumps for reactor water circulation, steam separators and dryers, and core support structure (2) reactor water recirculation system—pumps, valves, and piping used in providing and controlling core flow (3) main steam lines—main steam safety and relief valves, piping, and pipe supports from reactor pressure vessel up to and including the isolation valves outside of the primary containment barrier (4) control rod drive system—control rods, control rod drive mechanisms and hydraulic system for insertion and withdrawal of the control rods and (5) nuclear fuel and in-core instrumentation,... 

Personnel Hatches (2) 18. Technical Support Center 28. Main Steam Line... 

A prereformer partially completes the steam reforming reactions upstream of the main steam reformer at a much lower temperature by using a more active catalyst. One advantage... 

The deactivation curves are very varied depending on the catalyst type and experimental conditions- An example of a not common deactivation curve can be seen in fig.3- These curves show a minimum that we think it is due to the following deactivation mechanism tars crack on the catalyst surface with formation and build up of coke on the catalyst. But at these temperatures (840-08O C for the stones ) this coke is simultaneously gasified by many of the gas components (mainly steam) and the catalytic activity is partially restored. 

A small pilot valve controlling admission to and exhaust from this cylinder is mechanically operated by the main steam piston. An example of such a valve motion is the Cameron pump, illustrated in Fig. 

These reactions are about half as endothermic as the main steam reforming reaction (AH = 206 kJ/mol), and, since the carbon value is captured as salable products, CO2 emissions are reduced by at least 80%. However, less hydrogen is produced per unit of natural gas feed, for both reaction and heat requirements. Thus, the value of the carbon based product has a significant impact on the economic viability of the reaction process. 

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