Steam balance control valve

These operating problems must be overcome by selecting the correct system. Figure 15.15 shows an arrangement that balances the process steam and electrical demands by running the turbo-alternator in parallel with the electrical supply utility. The turbine inlet control valve maintains a constant steam pressure on the turbine exhaust, irrespective of the fluctuation in process steam demand. 

Steam turbines with electrical generators are used to recover the power from high pressure steam when the plant steam balance requires additional low pressure steam. As such, they provide more energy-efficient pressure regulation than a simple pressure control valve. Admission or extraction of steam to a header between stages, and/or condensation of exhaust steam fulfill additional steam balance and energy recovery needs. 

Steam letdown valves are used to give steam supply flexibility and temperature control. However, letdown steam represents lost opportunity for power generation. Steam balance optimization could minimize the letdown steam flow and henee reduee the loss in power-generating potential. 

The purpose is to develop a steam balance for operational supervision as well as for identification of improvement opportunities in the steam system. Models for boilers, turbines, deaerators (DAs), letdown valves, desuperheaters, and steam flash tanks are discussed in the previous chapter. Historian and distributed control system (DCS) data will be coimected to steam balance so that the steam balance is capable of dynamically balancing the steam and power demands due to process variations, units on or off, and weather change. 

In the reflux scheme, a column temperature controller manipulates a control valve in the reflux line. The reflux drum level controller manipulates a valve in the distillate line. The column base level controller manipulates a valve in the bottoms line. The feed and reboiler steam are each on flow rate control. In some cases, there is a controller for the pressure drop across the trays that manipulates the valve in the reboiler steam line. However, it is preferred to use a steam flow rate controller and simply monitor the tower pressure drop. With this scheme the separation power base is derived from the ratio of steam/feed. The distillate/feed material balance split is maintained by the MRT point controller. 

If, for example, the condenser cooling-water valve opens wider than the steam valve, and if its loading signal is less than 4.2 psig, the summer or balance controller calls for a slightly higher column pressure to increase condenser heat transfer. 

A vaporizer is typically used in a process to provide a vapor feed to downstream equipment. In that case, it may be desirable to set the flow of vapor directly with the setpoint of a flow control loop. Then the heat input is adjusted for pressure control and the liquid level is maintained by adjusting the inlet flow, in a reverse material balance manner, as shown in Figure 3.13(A). If heat transfer limits throughput, then both the vapor valve and the steam valve will operate fully open and the pressure will droop to an equilibrium point, where heat transfer equals the flow through the downstream equipment. 

Dryout of the insulation in the reformer furnace of Methanol 1 commenced in late August 1985 and methanol was synthesised on October 12. On October 17th the first gasoline was produced from the MTG plant. Only minor startup problems were encountered - a few valves operating unsatisfactorily, the odd steam leak and initial control system and heat balancing problems. 

The hot water from Tank 5 also supplies Tank 4 and Pump 3 (or 4), This is necessary to start and finish a batch through the sterilizer. For example, to start, the sterilizer is first steam sterilized (no liquid). At the end of this cycle, hot water from Tank 5 is started through the sterilizer to set or balance the instrumentation. When this is achieved, media is fed to Pump 3 (or 4) by remote operating valves. Similarly, after all the media has been pumped, it is necessary to pump water through the sterilizer until the fermenter volume is correct. If another fermenter is to be filled immediately, the sterile water is diverted to the awaiting empty (and sterile) fermenter, and then the new media for the second fermenter is pumped into the sterilizer. The control room for the operation of a continuous sterilizer should be close to Tank 4, Pumps 3 and 4, the main steam valves and the valves of the sterilizer itself This location is essential to sterilize the empty sterilizer and control the pumping of water and/or media. 

Reliability of the safety relief valves were developed to show that the new steam generation capability has not impact in the relief system. Re-circulation system and the performance and capability of the pumps and control system were evaluated, changes in the pump performance were identified, it also has impact in the heat balance. 

Withdrawing a control rod reduces the neutron absorption and increases core reactivity. Reactor power then increases until the increased steam formation just balances the change in reactivity caused by the rod withdrawal. The increase in boiling rate ends to raise reactor pressure, causing the initial pressure regulator fo open the turbine admission valves sufficiently to maintain a constant pressure. When a control rod is inserted, the converse effect occurs. 

The controlled device regulates the flow of steam, water, or air according to the commands of the controller as applied by the actuator. The regulation of these fluids helps to balance the load, gains, or losses in the HVAC system. These devices include motors, valves, and dampers. 

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