Reactor cleaning

Care must also be exercised when cleaning reactor parts and especially when changing pump oil. The vapors formed or passed through the plasma reactor are dissolved in most oils. Thus, inhalation of vapors and contact of oil with the skin must be avoided during oil changes and pump maintenance. 

Proceed with second batch if required after reducing reactor temperature, or else clean reactor and valves. 

Description The Vinnolit PVC process uses a new high-performance reactor (1), which is available in sizes up to 150 m3. A closed and clean reactor technology is applied thus, opening of the reactors is not necessary, except for occasional inspections. Equally important, high-pressure water cleaning is not necessary. All process operations of this unit are controlled by a distributed process control system (DCS). 

It is important to recognize that all surfaces that contact with the luminous gas phase participate and influence LCVD operation. Therefore, in principle, in a batch operation, the first run with clean reactor wall could not be replicated in the second run with contaminated reactor wall. Thus, it is necessary to include the step for cleaning the reactor. If only hydrocarbons were used in an LCVD, the cleaning could be done by O2 discharge prior to the normal LCVD operation. (The influence of wall contamination was described in Chapter 10.) In this respect, the effort to minimize the deposition on nonsubstrate surfaces is important even in batch operation of LCVD. Magnetron discharge is quite effective in this respect, as described in Chapter 14. 

Refinery or tank farm spills Cleaning reactors and storage tanks Carrier solvent in paints, stains and anti-corrosion coverings... 

Some coal liquefaction methods, such as the Synthoil (5) process and the CO-steam (6) process, are similar to solvent refining in their approach, but more severe conditions or a catalyst are used to give a fiuid product. In the Synthoil reaction, bituminous coal is pulverized, dispersed in a vehicle oil, and hydrogenated in a packed tubular reactor with or without added catalyst. The CO-steam process uses lignite coal and less expensive synthesis gas. The intended product is a heavy liquid fuel having ash, sulfur, and nitrogen contents suflBciently low to avoid stack-gas cleaning. Reactor temperature and pressure are normally 400°-450°C and 4000 psi, respectively. 

Fig. 5.30. Representative trains of oscillatory glow for CO + O2 mixtures in a closed system (a) chloropicrin-treated reactor with p = 33 Torr, = 841 K giving a total of 94 oscillations over 3 hr (b) and (c) light emission and reactant consumption in a clean reactor with p = 22 Torr and T, = 900 K. (Reprinted with permission from reference [60], Royal Society...

Wet Chemistry For sub-micron interconnect systems wet etching of tungsten is not a viable way to pattern tungsten lines. However, to clean reactor parts, or to reclaim or repair (8") precious wafers, a good wet etch chemistry is of importance. 

Pollution Prevention Technologies Practices Batch operations Equipment parts cleaning Reactor design operation High-value waste Water usage Organic solvents pH control... 

An explanation of how workers will be informed about the hazards of nonroutine tasks (such as cleaning reactors) and the hazards of chemicals... 

The amount of corrosion products deposited in the reactor core by precipitation from the dissolved phase depends on the solubilities of these oxides in the primary coolant and, in particular, on the temperature-dependence of their solubilities. Lower solubility at the higher coolant temperature in the reactor core than at the lower temperature in the steam generator (negative temperature coefficient of solubility) would favor enhanced transport to and precipitation in the core, whereas higher solubility at the higher temperature (positive temperature coefficient) would result in a clean reactor core. From the classical investigations of... 

We demonstrate the calculation of a temperature coefficient by considering the initial startup condition of the CP-5 and show how this coefficient may be used to predict the excess reacftivity (or multiplication) of the reactor at room temperature. Specifically, we compute the temperature coefficient of the hot clean reactor from the temperature derivatives of its thermal utilization, fast nonleakage probability, thermal nonleakage probability, and resonance-escape probability. The change in fc for a given change ST in temperature is then easily computed from the relation (6.142). 

The excess multiplication hk for the cold clean reactor (at 20 C) is computed from (6.142) thus,... 

Our primary interest in this calculation is the determination of the critical mass of the hot clean reactor and the radial distribution of the fast and thermal flux throughout the core and reflector. An accurate analysis of this system must necessarily take into account the completely reflected cylindrical geometry shown in Fig. 8.216. However, since this would entail a somewhat involved calculation, we will approximate the actual configuration by an equivalent reflected sphere of the same composition. This will reduce our computation appreciably and yet not obscure any of the essential steps in the application of the two-group model. A study of the effect of the corners in the completely reflected cylinder will be deferred until the next section. 

SDM is the amount of negative reactivity that would be added to a core if the rods in a critical, cold, clean reactor were fully inserted. 

Then the equipment heat transfer coefficient rp can be calculated from Eq. (28) written for a clean reactor. If there was some polymer deposit at the reactor wall during the cooling experiment, its resistance must be taken into account. 

Another invention of the late 1960s and early 1970s found acceptance as the need to reengineer PVC polymerization technology became critical. Clean-reactor technology, a combination of reactor design and wall treatment which inhibited scale formation on reactor walls, domes, and reflux condensers, was developed and implemented by a number of companies. It eliminated the need for human entry for reactor cleaning. 

EVA ethylene-vinyl acetate HDPE high-density PE LLDPE linear low-density PE MDPE medium-density PE MFI melt flow index MMT million metric tonnes NMWD narrow molecular weight distribution ULDPE ultra low-density PE CRT Clean reactor technology ... 

The third process is a continuous self-cleaning reactor process [5,8-10], In the self-cleaning reactor, low adhesion powders can be easily obtained under low SPS conversions. The heat transfer coefficient in the self-cleaning reactor is relatively high. Multiple reactors are necessary to achieve efficiency in the production scale. 

Styrene is polymerized in two reactors. The first one is a self-cleaning reactor (Q-300) and the second one is a stirred tank reactor with a helical ribbon mixer (V-300) [11]. 

The catalyst components are fed to the reactors. Fresh styrene is fed only to the self-cleaning reactor. In the reactors, styrene is polymerized to SPS in... 

---