Stabilizer reflux system

A stabilizer reflux system consists of a reflux condenser, reflux accumulator, and reflux pumps. The system is designed to operate at a temperature necessary to condense a portion of the vapors leaving... 

SiC fiber was produced from polycarbosilane (PCS) by Yajima et al. " in 1975, which is the earliest case of organosilicon polymer utilization for an industrial structural material. In the Yajima process, PCS was mainly synthesized from polydimethylsilane (PDS) by a thermal conversion process using an autoclave or an open reflux system. This is the commonly available PCS. Its melt spinability, solubility in various orgaiuc solvents, and stability for storing at room temperature are critically important for industrial uses. 

A total reflux startup is best performed with a mixture whose composition resembles the feed composition. Alternatively, total reflux operation can be carried out using one or more of the feed components. The column, reboiler, condenser, and reflux system are stabilized at... 

This stream(s) consists of materials up to an ASTM end point of approximately 400 degrees F. Until relatively recently, stabilized catalytic naphtha was blended directly into motor fuel. In most modern refineries, however, this product is now desulfurized by mild hydrogen processing. Olefin saturation usually occurs also. Since catalytic naphtha is seldom used without further processing, it is not the usual practice to split the naphthas in the main fractionator. If the split should be required, it can be done easily. In any event, the tower and the reflux system should be designed to allow a reasonable variation in naphtha end point and sharpness of fractionation between the naphtha and light cycle oil. 

The cooler may be an air-cooled exchanger or a shell-and-tube exchanger, which is quite often used when there is another system that needs to be heated. For a stabilizer with a reflux system, the bottom product may be cooled by exchanging heat with the feed to the stabilizer. The presentation on heat exchangers, covered in Volume 2 of the "Surface Production Operations" series, provides procedures for the selection and sizing of shell-and-tube heat exchangers. 

For stabilizers with a reflux system, a feed heater may be required. If a feed heater is used, it is normally a shell-and-tube type that exchanges heat between the cold-feed and the hot bottom product, which is then cooled before going to storage. 

A tandem radical addition/cyclization process has been described for the formation of benzindolizidine systems from l-(2-iodoethyl)indoles and methyl acrylate <00TL10181>. In this process, sun-lamp irradiation of a solution of the l-(2-iodoethyl)ethylindoles 149 in refluxing benzene containing hexamethylditin and methyl acrylate effects intermolecular radical addition to the activated double bond leading to the stabilized radical 150. Intramolecular cyclization to the C-2 position of the indole nucleus then affords the benzindolzidine derivatives 151 after rearomatization of the tricyclic radical. 

Even in an excess of ligands capable of stabilizing low oxidation state transition metal ions in aqueous systems, one may often observe the reduction of the central ion of a catalyst complex to the metallic state. In many cases this leads to a loss of catalytic activity, however, in certain systems an active and selective catalyst mixture is formed. Such is the case when a solution of RhCU in water methanol = 1 1 is refluxed in the presence of three equivalents of TPPTS. Evaporation to dryness gives a brown solid which is an active catalyst for the hydrogenation of a wide range of olefins in aqueous solution or in two-phase reaction systems. This solid contains a mixture of Rh(I)-phosphine complexes, TPPTS oxide and colloidal rhodium. Patin and co-workers developed a preparative scale method for biphasic hydrogenation of olefins [61], some of the substrates and products are shown on Scheme 3.3. The reaction is strongly influenced by steric effects. 

The tetraazapentalene ring system forms the core of the thermally insensitive explosive TACOT (Section 7.10) and so its fusion with the furoxan ring would be expected to enhance thermal stability and lead to energetic compounds with a high density, y-DBBD (95) is prepared from the nitration of tetraazapentalene (91), nucleophilic displacement of the o-nitro groups with azide anion, further nitration to (94), followed by furoxan formation on heating in o-dichlorobenzene at reflux. The isomeric explosive z-DBBD (96) has been prepared via a similar route. ... 

Monocyclic l,2-dihydro-l,2-azaborines (3) easily form polymers with the exception of the 2-phenyl derivative (109 R = Ph), probably because of interaction between the two rings. In contrast, the alkyl substituted monocyclic system (155) is stable towards polymerization although it is easily oxidized by air and hydrolyzed by water. This stability order between (3) and (155) was predicted by semi-empirical methods. However, the ring system (7), isosteric with pyridine, seems to be the most stable of the monocyclic systems. Some of its alkyl derivatives remain unchanged after 50 h in concentrated sulfuric acid at 80 °C. After reflux in 1M sodium hydroxide almost all of the compound was recovered. 

It may be found advantageous to replace or supplement one or more of the lower stages of a separation system with a stabilizer tower. A stabilizer is a fractionator, operating either with or without reflux, and may be of various degrees of efficiency. The number of trays and height is limited by the platform configuration, but towers with 20-30 trays are feasible on many offshore platforms. 

The improvement in system stability is clearly shown in Figure 3.43. Reactor temperature is well controlled in the face of the disturbance in F. The CB concentration drops to about 0.06 kmol/m3. The FB0 flowrate is constant. The FA0 flowrate increases initially because the reactor level drops, but it gradually returns to the initial value. Reflux, vapor boilup and recycle flows all increase because of the increase in F, but the product stream P returns to its initial level. 

---