During Start-Up

The main steps involved in start-up of a sulfuric acid plant after a long stoppage are [Pg.77]

Boxing up of all equipment opened up for cleaning/maintenance/inspection, etc., testing for leaks, smooth running. [Pg.77]

Establishing sufficient acid circulation in all the acid towers. [Pg.77]

Heating up the various units of the plant so as to bring the temperatures of the furnace to a satisfactory level for the burning of sullur, bringing the catalyst in the converter passes up to conversion temperature, removing moisture from [Pg.77]

Ashar and K.R. Golwedkeir, A Practical Guide to the Manufacture of Sulfuric Acid, Oleums, and Sulfonating Agents, DOI 10.1007/978-3-319-02042-6 8, [Pg.77]

Sulfur. Sulfur in diesel fuel should be kept below set limits for both environmental and operational reasons. Operationally, high levels of sulfur can lead to high levels of corrosion and engine wear owing to emissions of SO that can react with condensed water during start-up to form sulfuric acids. From an environmental perspective, sulfur bums to SO2 and SO, the exact spHt being a function of temperature and time in the combustion chamber. [Pg.192]

Thermal Stresses. When the wak of a cylindrical pressure vessel is subjected to a temperature gradient, every part expands in accordance with the thermal coefficient of linear expansion of the steel. Those parts of the cylinder at a lower temperature resist the expansion of those parts at a higher temperature, so setting up thermal stresses. To estimate the transient thermal stresses which arise during start-up or shutdown of continuous processes or as a result of process intermptions, it is necessary to know the temperature across the wak thickness as a function of radius and time. Techniques for evaluating transient thermal stresses are available (59) but here only steady-state thermal stresses are considered. The steady-state thermal stresses in the radial, tangential, and axial directions at a point sufficiently far away from the ends of the cylinder for there to be no end effects are as fokows ... [Pg.85]

In most existing styrene processes, the catalyst is loaded into large, radial flow reactors, which are operated adiabaticaHy at low pressure and temperatures near 600°C. Heat is suppHed by superheated steam. During start-up, dehydrogenation begins slowly and accelerates as the Fe (HI) is reduced to Fe (II,III). The catalyst, which was red in color when fresh, turns to the characteristic black color of Fe O. ... [Pg.198]

Take-Ups. A take-up is requited on a belt conveyor to ensure the proper belt tension at the drive pulley and along the conveyor, as weU as to ensure the proper troughing contour between idlers. A take-up is also needed to compensate for changes in belt length caused by elastic stretch during start-up, and any elongation characteristics of the belt that occur over a period of time. [Pg.155]

If the process feed does not He in the Hquid—Hquid region it can be made to do so by dehberately feeding either pure or pure B to the decanter, as required. This may only be necessary during start-up or for control purposes because the recycled azeotrope has the beneficial effect of dragging the decanter composition further into the Hquid—Hquid region. [Pg.194]

During start-ups, as changes may be necessary to get the plant on line. [Pg.2270]

The magnetic field rotates at a synchronous speed, so it should also rotate the rotor. But this is not so in an induction motor. During start-up, the rate of cutting of llux is the maximum and so is the induced e.m.f. in the rotor circuit. It diminishes with motor speed due to the reduced relative speed between the rotor and the stator flux. At a synchronous speed, there is no linkage of flux and thus no induced e.m.f. in the rotor circuit, consequently the torque developed is zero. [Pg.6]

The last two parameters are maximum during start-up, diminish with speed and become zero at the synchronous speed (when S = 0). Therefore 7 = 0 when, 2 = 0. [Pg.6]

During start-up or at high slips, the value of will be too high compared to / i and equation (1.3) will modify to... [Pg.6]

This is a vital relationship, which reveals that during start-up and until such speed, the reactance of the motor windings / 2> the rotor current will also remain almost the same as the starting current and will fall only at near the rated speed. (Refer to the current curves in Figures 1.5(a) and (b)). The initial inrush current in a squirrel cage induction motor is very high. In a slip-ring motor, however, it can be controlled to a desired level. (Refer to Section 5.2.1.)... [Pg.8]

During start-up, at lower voltages, the starting torque is... [Pg.10]

During start-up since only the outer cage is in the circuit with a very high current, the motor is heated up quickly by every start and may not be suitable for frequent starts and reversals. [Pg.39]

The rotor and stator heats, during start-up and run, arc interrelated and vary in the same proportion as their respective resistances. (See circle diagram Figure 1.16 in Section 1.10.)... [Pg.43]

During start-up the rotor, due to its lighter weight compared to the stator, and during a run, the. stator, due to overload are more vulnerable to damage through excessive heat. [Pg.43]

A rotor fails during start-up, possibly due to a lower supply voltage than desired or a smaller accelerating torque than required or reasons leading to similar conditions. In such cases the rotor tails first, due to higher rotor currents and a prolonged acceleration time or a locked rotor. At this instant, unless the motor control gear trips, the stator may also fail due to excessive heat. Instances can be cited where even... [Pg.43]

I. A CMR motor therefore can be operated at higher outputs on short-time duties as shown in curve (d). The extent to which a CMR motor cun be over-rated to perform a particular short-time or intermittent duty is considered in the follow ing example. While evaluating the rating for such duties, the heat during start-up and during braking and their frequency of occurrence should be considered. [Pg.59]

During start-up, the firing angle is kept high to keep the V and low. It is then reduced gradually to raise the... [Pg.139]

Ki = mean load factor, i.e. the ratio of the average load torque to the motor torque which depends upon the loading on the motor during start-up. [Pg.162]

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