Inhibitors continuous injection

This method (Fig. 9.5 B) was designed to test whether any inhibition reaction occurred in the presence of a water-insoluble substrate during lipase hydrolysis. Lipase was injected into the reaction vessel of a pH-stat containing the emulsified substrate maintained under vigorous stirring. The inhibitor was injected a few minutes after lipase addition. Lipase activity was then continuously recorded (Fig. 9.5 B). 

The inhibitor was injected before the enzyme addition at various concentrations into a hpolysis assay containing the emulsified substrate under vigorous stirring. Lipase activity was then continuously recorded (Fig. 9.5 C). 

Inhibitors act to control corrosion, particularly in piping systems. They form a very thin (perhaps monomolecular) adsorbed layer that acts as a barrier. Film-forming amines are a common example. Because inhibitors may locally de-adsorb, they are usually continuously injected. For large-diameter pipelines, batch inhibition may be necessary. Inhibition is usually not permitted in processes for high-purity products. 

Continuous injection of corrosion inhibitors is practiced in once-through systems where slugs or batch treatment cannot be distributed evenly through the fluid. This method is used for water supplies, oil field injection water, once-through cooling water, open annulus oil or gas weUs, and gas lift wells. Liquid inhibitors are injected with a chanical injection pump. These pumps are extremely reliable and require little maintenance. Most chemical injection pumps can be adjusted to deliver at the desire injection rate (Chen et al. 2010). 

Boilers, closed cooling water systems, and other closed circulating fluid systems can be treated with inhibitors with continuous injection. When snch systems are started up after construction or major maintenance, the inhibitor is often injected at higher-than-normal concentration to permit rapid development of protective films (Tang et al. 2012). 

Protection in this case may be achieved through continuous injection of film-forming corrosion inhibitors, as they can be transported by the water phase and film over the full pipe surface. Attention should be paid in this case to the flow velocity, as highly turbulent flow may produce high shear stresses on the pipe wall and remove the inhibitor film. 

Gas wells corrode mostly in the reflux zone, which is an area of the well somewhere between the bottom and the wellhead, where condensation occurs. As the gas flows up the well, its temperature drops due to expansion, and this causes condensation when the temperature reaches the dew point of the gas. Volatile inhibitors such as formaldehyde and ammonia, injected into gas wells have been used successfully to inhibit corrosion. Many gas weUs today are protected by injecting amine inhibitors continuously, in batches, or by squeezing, which means they coat the well when injected and also enter the gas stream partially by vaporization and partially by entrainment. 

Continuous injection is generally the best method, if it can be applied. Inhibitor is always present to repair places where the old inhibitor has been removed. Some wells are completed with parallel strings, concentric strings, and U-tube-type strings. If the well will support the column of inhibited fluid (parallel and concentric completions), then continuous injection can be accomphshed. In most cases, a U-type completion will have a back pressure valve toward the bottom of the small string and can be loaded with the inhibited fluid. 

Gas lift wells are sometimes treated by injecting the inhibitor with a chemical pump into the lift gas line. This inhibitor gives protection only from the operating valve to the surface. For this kind of application continuous injection-type inhibitors or batch-type inhibitors are effective. It is best to inject at the well, but injecting at the compressor is also possible. 

Pipeline inhibition is accompbshed after clean-up by mixing an oU-dispersible inhibitor with hydrocarbon and batching between two pigs, using the formula proposed hy the suppher. In wet gas systems a continuous injection-type method should be used, at an economical rate speeified by the suppher, depending on the severity of the problem and the amount of water being handled. 

Continuous injection is used after clean-up and batch treatment has heen accomplished. In dry gas systems handling condensate, the same programs apply. Condensate should always he considered to contain some water. In dry gas systems that handle no hquids, clean-up and hatch treatments are recommended. Continuous injection is not desirable because there is nothing to help carry the inhibitor down the hne. Pipeline programs have to be designed for each system separately. 

Inhibitor concentrations vary from a few parts per million in continuous injection applications, to several thousand parts per million in closed systems, to batch treatments of the neat or undiluted inhibitor. Concentrations used influence test conditions and often determine whether or not... 

Use of inhibitors. Because corrosion is such a vital aspect of the erosion-corrosion process, inhibitors that will reduce corrosion under conditions of high fluid velocity have been a cost-effective method of dealing with erosion-corrosion. For example, injection of ferrous sulfate either intermittently or continuously has been successful in inhibiting erosion-corrosion, especially with copper-base alloys. 

Fig. 5.1 Principle of MS-based enzyme assays. Enzyme (E) molecules react with the substrate (S) to form an enzyme-substrate complex (ES), leading, for example, to a subsequent cleavage into two products Pi and P2. Pi and P2 are monitored continuously by ESI-MS. The injection of an inhibitor, I, results in the temporary formation of an inactive enzyme-inhibitor (El) complex, resulting in a reduction of Pi and P2 and negative peaks in the corresponding mass traces.

You are asked to treat a 55-year-old patient for continuing ventricular arrhythmias. The patient is receiving timolol drops for glaucoma, daily insulin injections for diabetes melUtus, and an ACE inhibitor for hypertension. You decide to use phenytoin instead of procainamide because of what pharmacological effect of procainamide ... 

Bleed water can be taken from the sump (but not from any point where dirt or sludge can block the valve) or from the return line after the heat exchangers. Where bleed is taken from the return line, this should be at a point before the injection of chemical inhibitor. For large cooling systems, it may prove useful to employ a small manual bleed valve to continuously discharge perhaps 70 to 80% of the required flow and to provide the balance via a conductivity controlled, solenoid valve. 

ALFENTANIL, BUPRENORPHINE, FENTANYL, TRAMADOL PROTEASE INHIBITORS Possibly t adverse effects when buprenorphine is co administered with indinavir, ritonavir (with or without lopinavir) or saquinavir Inhibition of CYP3A4 (CYP2D6 in the case of tramadol) Halve the starting dose and titrate to effect. For single injection of fentanyl, monitor sedation and respiratoiy function closely. If continued use of fentanyl, i dose may be required. Concomitant use of ritonavir and transdermal fentanyl is not recommended... 

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