Plant control references

Plant Species Ozone Concentration, ppm Exposure Time, h Plant Growth Response, % reduction from control Foliar Injury Response, % increase over control Reference... 

The temperature of a gas oil product flowing through a pipe is monitored using a chromel/alumel thermocouple. The measurement junction is inserted into the pipe and the reference junction is placed in the plant control room where the temperature is 20°C. The emf at the thermocouple junction is found to be 6.2 mV by means of a potentiometer connected into the thermocouple circuit adjacent to the reference junction. Find the measured temperature of the gas oil. 

Two very useful review articles on the various aspects of complete plant control system design with lists of relevant references are the following ... 

Supervisory control refers to the role a human plays in operating a semiautomatic process or system. Examples include control of large systems such as a nuclear power plant and specific instrumentation such as a robotic or assistive device. Performing supervisory control is high-level task that predominantly consists of mental components. This task is used to generically illustrate the use of analytic techniques to model a task. 

The pharmacopeias describe the quality control of the plant extracts by the succession of the separated spots obtained after TLC, including the color, order and position on the plate compared to the reference substances. The description should match the TLC separation of the plant extract. The correspondence of the spots is important for the qualitative analysis of the medicinal plant. The reference substances chosen and mentioned in pharmacopeias can also be present in the analyzed plant extract, or can be... 

When discussing steam turbines one needs to keep in mind that these are applicable for nuclear plants also. Refer to Fig. XII/3.0-1 to see that the turbine generator part in both cases is the same. In nuclear applications, naturally reliability and availability are of immense importance. Similarly, in fossil fuel power stations, if turbine safety is compromised, then the high-cost turbine cannot survive and would incur huge financial loss. There following points need to be considered for turbine control and safety systems ... 

Unlike 25 % Oleum, 65 % Oleum can be manufactured only by use of pure SO3 gases evaporated out of 25 % Oleum in a boiler heated by energy available in the hot gases of the Contact Sulphuric Acid Plant. Please refer to Block Diagram (see Fig. 2.8). The pure SO3 vapours are sent to 65 % Oleum Tower having facilities for cooling the heat generated due to exothermic absorption as well as dilution by addition of 25 % Oleum. A Level Controller is provided to maintain Tank level in the circulation boot. 

The Authors make only brief reference to the commissioning of plant control systems. Could they explain what commissioning techniques were used, and also their usefulness In the light of experience ... 

Since the Super LWR is a plant with a direct-steam cycle like BWRs, those components are selected by referring to BWRs. The control rods, the feedwater pumps and the turbine control valves are to be used for plant control of the Super LWR. It is noted that the Super LWR has no recirculation pumps. 

The plant dynamics of the Super LWR were understood by plant transient analyses. Although the Super LWR is a thermal spectrum reactor, the reactor power is not very sensitive to the flow rate because the water rods with large volume fraction mitigate fluctuation of the average water density. Based on the plant transient analyses and also referring to LWRs and FPPs, the plant control system of the Super LWR was designed and tuned. Finally, the adequacy of the control system was assessed by plant stability analyses. 

There are two principal approaches to the biological control of weeds (483—485). The first approach is referred to as classical or inoculative biological weed control. Plants that have been introduced to areas outside of their natural range often encounter fewer growth and seed dissemination... 

Emissions control systems play an important role at most coal-fired power plants. For example, PC-fired plants sited in the United States require some type of sulfur dioxide control system to meet the regulations set forth in the Clean Air Act Amendments of 1990, unless the boiler bums low sulfur coal or benefits from offsets from other highly controlled boilers within a given utiUty system. Flue-gas desulfurization (FGD) is most commonly accomphshed by the appHcation of either dry- or wet-limestone systems. Wet FGD systems, also referred to as wet scmbbers, are the most effective solution for large faciUties. Modem scmbbers can typically produce a saleable waUboard-quaUty gypsum as a by-product of the SO2 control process (see SULFURREMOVAL AND RECOVERY). 

In most process plant situations where feedforward control is appropriate, a combination of the feedforward and feedback control is usually used. The feedforward portion reduces the impact of measured disturbances on the controlled variable while the feedback portion compensates for model inaccuracies and unmeasured disturbances. This control strategy is referred to as feedforward control with feedback trim. 

Hazardous Air Pollutants. Tide 3 of the CAAA of 1990 addresses the release of hazardous air poUutants (HAPs) by requiring both the identification of major stationary sources and area source categories for 189 toxic chemicals and the promulgation of control standards. Major sources of air toxics, also referred to as HAPs, include any stationary source or group of sources emitting 10 or more tons/yr of any single Hsted toxic chemical or 25 tons/yr of a combination of any Hsted toxic. Area sources of HAPs include smaller plants that emit less than the 10 or 20 tons/yr thresholds. The major sources of HAPs are typically industrial faciHties. However, Tide 3 requites the EPA to study potential health affects associated with emissions of HAPs from electric UtiHty boilers (11). 

Persistence of pesticides in the environment is controlled by retention, degradation, and transport processes and their interaction. Retention refers to the abihty of the soil to bind a pesticide, preventing its movement either within or outside of the soil matrix. Retention primarily refers to the sorption process, but also includes absorption into the soil matrix and soil organisms, both plants and microorganisms. In contrast to degradation that decreases the absolute amount of the pesticide in the environment, sorption processes do not affect the total amount of pesticide present in the soil but can decrease the amount available for transformation or transport. 

In the early 1970s, air pollution requirements led to the adoption of the double contact or double absorption process, which provides overall conversions of better than 99.7%. The double absorption process employs the principle of intermediate removal of the reaction product, ie, SO, to obtain favorable equiUbria and kinetics in later stages of the reaction. A few single absorption plants are stiU being built in some areas of the world, or where special circumstances exist, but most industriali2ed nations have emission standards that cannot be achieved without utili2ing double absorption or tad-gas scmbbers. A discussion of sulfuric acid plant air emissions, control measures, and emissions calculations can be found in Reference 98. 

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