Feed streams control

Ethylene and comonomer are purified and dissolved in a solvent. An activated catalyst is added to that solution, which is then fed to a stirred reactor. The temperature of the feed stream controls reactor temperature, which is a major determinant of polymer molecular weight. Reactor temperatures are usually 170-250°C with pressures of 4-14 MPa (500-2000 psi). The solution is then fed to a secondary, trimmer reactor where further polymerization takes place. Chelating agents are injected into the solution to neutralize active catalyst. A high pressure flash vessel is used to remove monomer and about 90% of the solvent. A secondary devolatilization step is required to completely remove solvent. Granular polymer is then conveyed for pelletization. 

The size of the leakage was determined as follows. Radiation detectors were mounted on the inlet of the first side, and the outlet of the second side of the heat exchanger and at additional locations for control. A short pulse of Kr-85 tracer (<0.1 sec) was injected into the feed stream, which gave rise to detector responses shown in figure 3. 

An extraction plant should operate at steady state in accordance with the flow-sheet design for the process. However, fluctuation in feed streams can cause changes in product quaUty unless a sophisticated system of feed-forward control is used (103). Upsets of operation caused by flooding in the column always force shutdowns. Therefore, interface control could be of utmost importance. The plant design should be based on (/) process control (qv) decisions made by trained technical personnel, (2) off-line analysis or limited on-line automatic analysis, and (J) control panels equipped with manual and automatic control for motor speed, flow, interface level, pressure, temperature, etc. 

In order to faciUtate heat transfer of the exothermic polymerization reaction, and to control polymerizate viscosity, percent reactives are adjusted through the use of inert aromatic or aUphatic diluents, such as toluene or heptane, or higher boiling mixed aromatic or mixed aUphatic diluents. Process feed streams are typically adjusted to 30—50% polymerizable monomers. 

The two portions of the feed stream recombine and flow into the high pressure separator where the Hquid is separated from the vapor and is fed into an intermediate section of the demethanizer with Hquid level control. The decrease in pressure across the level-control valve causes some of the Hquid to flash which results in a decrease in the stream temperature. The pressure of the vapor stream is decreased by the way of a turboexpander to recover... 

Fig. 23. Two types of hollow-fiber modules used for gas separation, reverse osmosis, and ultrafiltration applications, (a) Shell-side feed modules are generally used for high pressure appHcations up to - 7 MPa (1000 psig). Fouling on the feed side of the membrane can be a problem with this design, and pretreatment of the feed stream to remove particulates is required, (b) Bore-side feed modules are generally used for medium pressure feed streams up to - 1 MPa (150 psig), where good flow control to minimise fouling and concentration polarization on the feed side of the membrane is desired.

Both propylene and isobutylene ate comonomers that are incorporated along the chain, resulting in additional short-chain branching. One important factor in controlling polymer crystallinity is the choice of chain-transfer agent. Ethane and methane, for example, are inefficient agents whose presence in the monomer feed stream must be considered in reaction control. 

The success of a reverse osmosis process hinges direcdy on the pretreatment of the feed stream. If typical process streams, without pretreatment to remove partially some of the constituents Hsted, were contacted with membranes, membrane life and performance would be unacceptable. There is no single pretreatment for all types of foulants. Pretreatment methods range from pH control, adsorption (qv), to filtration (qv), depending on the chemistry of the particular foulant. Some of the pretreatment methods for each type of foulant are as foUow (43—45) ... 

A selective poison is one that binds to the catalyst surface in such a way that it blocks the catalytic sites for one kind of reaction but not those for another. Selective poisons are used to control the selectivity of a catalyst. For example, nickel catalysts supported on alumina are used for selective removal of acetjiene impurities in olefin streams (58). The catalyst is treated with a continuous feed stream containing sulfur to poison it to an exacdy controlled degree that does not affect the activity for conversion of acetylene to ethylene but does poison the activity for ethylene hydrogenation to ethane. Thus the acetylene is removed and the valuable olefin is not converted. 

The refining of oil produces the monomer feed streams for tackifiers as byproducts of the process. Tackifiers are low molecular weight polymers, typically 300-5000 g/mol, most often 500-1000 g/mol. Generally molecular weights are well below Mg and thus, within a given class of resins, softening points are controlled primarily by molecular weight (see Fig. 1). 

Acyclic C5. The C5 petroleum feed stream consists mainly of isoprene which is used to produce rubber. In a separate stream the linear C5 diolefin, piperylene (trans and cis), is isolated. Piperylene is the primary monomer in what are commonly termed simply C5 resins. Small amounts of other monomers such as isoprene and methyl-2-butene are also present. The latter serves as a chain terminator added to control molecular weight. Polymerization is cationic using Friedel-Crafts chemistry. Because most of the monomers are diolefins, residual backbone unsaturation is present, which can lead to some crosslinking and cyclization. Primarily, however, these are linear acyclic materials. Acyclic C5 resins are sometimes referred to as synthetic polyterpenes , because of their similar polarity. However, the cyclic structures within polyterpenes provide them with better solvency power and thus a broader range of compatibility than acyclic C5s. 

When a fire occurs, it is assumed that all fluid flow to and from the fire risk area has been stopped. Therefore, flow loads such as control valve failure or incoming feed streams are not additive to the fire load. Credit is not generally given to flow out through normal channels, since they could also be blocked during the fire emergency. 

All feed streams are sterilised before being metered into the fermentation vessel. Contaminants resistant to the antibiotic rarely find their way into the fermenter. When they find a way to contaminate media, their effects are so catastrophic that prevention is of paramount importance. A resistant, (3-lactamase producing, fast-growing bacterial contaminant can destroy the penicillin.5 The contaminants not only consume nutrients intended for the fungus, but also cause loss of pH control and interference with the subsequent extraction process. 

Achieving steady-state operation in a continuous tank reactor system can be difficult. Particle nucleation phenomena and the decrease in termination rate caused by high viscosity within the particles (gel effect) can contribute to significant reactor instabilities. Variation in the level of inhibitors in the feed streams can also cause reactor control problems. Conversion oscillations have been observed with many different monomers. These oscillations often result from a limit cycle behavior of the particle nucleation mechanism. Such oscillations are difficult to tolerate in commercial systems. They can cause uneven heat loads and significant transients in free emulsifier concentration thus potentially causing flocculation and the formation of wall polymer. This problem may be one of the most difficult to handle in the development of commercial continuous processes. 

In a typical example (33) a fresh feed of 8% polybutadiene rubber in styrene is added with antioxidant, mineral oil, and recycled monomer to the first reactor at 145 lbs./hr. The reactor is a 100-gallon kettle at approximately 50% tillage with the anchor rotating at 65 rpm. The contents are held at 124°C and about 18% conversion. Cooling is effected via the sensible heat of the feed stream and heat transfer to the reactor jacket. In this reactor the rubber phase particles are formed, their average size determined and much of their morphology established. Particle size is controlled to a large measure by the anchor rpm. 

Temperature control is primarily obtained via the sensible heat of the cooled feed stream with the remaining heat of reaction being removed by the reactor jacket. 

Solution Ideal gas behavior is a reasonable approximation for the feed stream. The inlet concentrations are 287mol/m of methane and 15mol/m of carbon dioxide. The column pressure drop is mainly due to the liquid head on the trays and will be negligible compared with 8 atm unless there are an enormous number of trays. Thus, the gas flow rate F will be approximately constant for the column as a whole. With fast reaction and a controlling gas-side resistance, c = 0. The gas-phase balance gives everything that is necessary to solve the problem ... 

Figure 1. Principle of 3-way exhaust emission control. Catalyst efficiencies measured in the laboratory with a steady feed stream composition at various simulated air/fuel ratios. Catalyst 0.042 wt % Pt/0.018 wt % Kh/alumina.

Semi-batch reactor with heat production Feedback control of feed stream Jacket cooling... 

The experiments were performed in a CINC V-02 separator also known as the CS-50 (15). Two Verder VL 500 control peristaltic tube pumps equipped with a double pump head (3,2 x 1,6 x 8R) were used to feed the CCS. In case of the enzymatic reaction, the low mix bottom plate was applied. To operate the reactor at a desired temperature, it was equipped with a jacket which was coimected to a temperature controlled water bath with an accuracy of 0.01°C. The CCS was fed with pure heptane and pure water, both with a flow rate of 6 mL/min. Subsequently, the centrifuge was started (40 Hz, which corresponds to 2400 rpm) and the set-up was allowed to equilibrate for a period of 1 h. At this point, the heptane feed stream was replaced by the organic feed stream (oleic acid (0.6M) and 1-bntanol (0.9M) in heptane). After equilibration for 10 minutes, the reaction in the CCS was started by replacing the water stream with the aqueous feed stream (0.1 M phosphate buffer pH 5.6 containing 1 g/1 of the lipase form Rhizomucor miehei). Samples were taken at regular intervals and analysed by GC. 

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