Start-up conditions

Since for constant pressure filtration, the tjV versus Vdata can be linearized, as shown in Figure 4.15, the resistances of cake and cloth plus cake held up in cloth can be determined. The former value is usually fairly reproducible while the latter is often variable, being particularly sensitive to start up conditions when cloth blinding occurs. Such tests can be rerun at different pressures and the extent of cake compressibility determined. Similarly, a wash cycle can be introduced. 

It is, however, important to avoid condensation. Although the condensate from gas combustion is generally considered non-acidic, if the flue has not been designed for conditions of continual wetting condensation should be avoided. Intermittent condensation under start-up conditions can usually be tolerated. 

The capacity of any steam trap will depend on the difference in pressure between its inlet and outlet connections. Under system start-up conditions the steam pressure in the line will at first be only marginally above atmospheric. If the trap discharge line rises to a higher level, or delivers to a pressurized return pipe, no condensate will flow through the trap until the line pressure exceeds the back pressure. It is important that steam traps which can drain by gravity, with zero back pressure, are fitted... 

One of the liquid contaminants is water, the presence of which is brought about by the fact that when fuel is burnt it produces approximately its own weight in water. When the engine is warm, this water is converted into steam, which passes harmlessly out of the exhaust. However, with cold mnning or start-up conditions this water is not converted and drains into the sump. Having dissolved some of the combustion gases, it will be acidic in nature and will form sludge. 

For a single continuous reactor, the model predicted the expected oscillatory behaviour. The oscillations disappeared when a seeded feed stream was used. Figure 5c shows a single CSTR behaviour when different start-up conditions are applied. The solid line corresponds to the reactor starting up full of water. The expected overshoot, when the reactor starts full of the emulsion recipe, is correctly predicted by the model and furthermore the model numerical predictions (conversion — 25%, diameter - 1500 A) are in a reasonable range. 

Anticipated process variations that may affect the sizing of the driver (such as changes in pressure, temperature, or properties of the liquid handled, as well as special plant start-up conditions) will be specified. 

SIS trip The ESP is de-energized when the SIS trips and pulls feed. Start-up Start-up conditions represent a risk for upset conditions. The ESP is typically not commissioned until after the unit has reached steady-state. 

KINPTR s real-time activity kinetics determine the adiabatic reactor inlet temperature required to make a target octane. The accuracy of KINPTR s reactor inlet temperature predictions is shown in Fig. 30 for a wide range of process conditions. The average deviation is + 3.8 K with no significant bias. This degree of accuracy is very reasonable considering the sensitivity of catalyst activity to start-up conditions and initial catalyst state (e.g., chloride added). 

It is clear that during start-up, conditions conducive to hydrate formation can exist at the wellhead, flowline and in the riser. Once flow has stabilised, conditions suitable for hydrate formation can exist in the subsea flowline, particularly at higher GOR s. 

An alternative that is less resource-intensive than the flow loop is the flow wheel apparatus (Bakkeng and Fredriksen, 1994 Lippmann et al., 1994) shown in Figure 6.4b. The wheel (torus) is nominally a 2-5 in. (5.1-12.7 cm) pipe, 2 m in diameter that rotates at 0.3-5.0 m/s while filled with gas and less than 50 vol% liquid. Conceptually, the wheel is spun past the gas and liquid rather than the reverse. Therefore, the flow wheel apparatus does not require circulating devices such as pumps or compressors. Hydrate formation is deduced visually, or by a sharp increase in torque required to turn the wheel. Urdahl et al. (1995) and Lund et al. (1996) report good field transferability from results obtained with this apparatus. Pilot flow loops and flow wheels have been also used to simulate shut-in/start-up conditions (12 h stagnant period) and to test kinetic inhibitors (e.g., Palermo and Goodwin, 2000 Rasch et al., 2002). 

Viscoelastic fluids can be further subcategorized as (1) thixotropic fluids, which show a reversible decrease in shear stress with time at a constant rate of shear, and (2) rheopectic fluids, which show an opposite effect. In normal reactor operation, these time dependencies usually become important for start-up conditions and for significant system perturbations. 

Figure 13.3 Comparison of cleaning when performed within 15% of performance decline and when performance has fallen more than 15% from start-up conditions.

The exponential term in the conversion equation arises from the assumed start-up condition of a reactor filled only with degased water and then fed at time zero with a stream having monomer concentration [Mp],... 

Start-up conditions Start-up should always be close to optimum conditions to prevent fouling the punch faces. If maintaining the force above a minimum is necessary to prevent picking, starting up near aim conditions of compression force prevents initial picking. 

Also, during start-up conditions with systems that nucleate heavily or with systems that exhibit cycling behavior with regard to crystal size, it will be found that lower-than-equilibrium values of the finer crystal sizes will be present for a time during the growth cycle. 

The table as shown applies to a fully loaded platform with all four 4 MW generators running at a load factor of approximately 80%. At first sight it may appear that too many items are included in the table. However, as the platform becomes loaded from its start-up condition the nmnber of items in their on state increases from a small number, and each item may be only partially loaded. Once the total load requires two generators to be on-line, then the PMS can be enabled to take load shedding action. 

The safety technical assessment of the start-up conditions has to check on the correct choice of initial temperature and initial conversion, as well as to ensure that the dynamic process does not lead to the development of limit cycle oscillations but to a short transient time with decreasing amplitudes, followed by a steady state. 

In principle, the safety assessment of a process performed in a cooled CSTR under normal operating conditions is fully completed if start-up conditions as well as static and dynamic stability have been evaluated. The assessment performed this way yields unambiguous yes/no statements. 

The above table is based on start-up conditions. During continued operation the gas load from air saturated water will be negligible. 

This makes the thermostatic trap suitable to remove large quantities of air and cold condensate at the start-up condition, especially for batch-wise processes. 

The RO unit has several start-up conditions that must be specified ... 

A loss of selenium from the surface was observed upon exposure to potentials greater than 0.85 V, and this can have a detrimental effect on the implementation of RuSe/C as a cathode material in fuel cell applications which should, therefore, be further investigated. While steady-state operation could be confined to low cathode potentials, exposure to higher potentials in transients, e.g. during start-up conditions, could lead to selenium loss with a concomitant drop in fuel cell performance. The commercially available rhodium sulphide underperformed and exhibited higher susceptibility to methanol compared to RuSe/C, but was found to be more stable under similar testing conditions. 

Table 3.6 Typical start up conditions for various TPEs.

Low mass The low densities of plastics materials gives an assembly of low mass, and hence low inertia. This can be useful under start-up conditions, and may even allow the use of a lower-power motor. 

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