Probe testing, chemical processing

The experiments must be done, preferably at steady state, at the same conditions of temperature, pressure and concentrations (even of minor components) as in the intended process, to avoid unpredictable changes in coalescence. They must be carried out in a system of the recommended configuration, preferably at similar power per unit volume and superficial gas velocity as may be used at full scale. The agitator speed should be varied to check whether mass transfer is important and gas hold-up should be measured (e.g. by level probe or y-ray density scan). In cases involving chemical reactions, further tests are required as described in section 15.10. 

Electrical resistance (ER) corrosion probes are commonly used in petroleum, chemical processing, and other environments where on-hne corrosion rate readings are required (see Figure 8.2). Whereas test coupons must be removed from the process for evaluation, corrosion probes can allow corrosion rate determination without probe removal. Probes can be manufactured according to specific requirements for temperature, pressure, and other conditions. Hydrogen, sampling, injection, and custom-designed probes can be made as well. 

The power of the pooled GST fusion protein approach will increase as new biochemical reagents and assays become available. The development of chemical probes for biological processes, termed chemical biology, is a rapidly advancing field. For example, the chemical synthesis of an active site directed probe for identification of members of the serine hydrolase enzyme family has recently been described (Liu et al., 1999). The activity of the probe is based on the potent and irreversible inhibition of serine hydrolases by fluorophosphate (FP) derivatives such as diisopropyl fluorophosphate. The probe consists of a biotinylated long-chain fluorophosphonate, called FP-biotin (Liu et al., 1999). The FP-biotin was tested on crude tissue extracts from various organs of the rat. These experiments showed that the reagent can react with numerous serine hydrolases in crude extracts and can detect enzymes at subnanomolar... 

Mechanical and chemical methods for qualitative and quantitative measurement of polymer structure, properties, and their respective processes during interrelation with their environment on a microscopic scale exist. Bosch et al. [83] briefly discuss these techniques and point out that most conventional techniques are destructive because they require sampling, may lack accuracy, and are generally not suited for in situ testing. However, the process of polymerization, that is, the creation of a rigid structure from the initial viscous fluid, is associated with changes in the microenvironment on a molecular scale and can be observed with free-volume probes [83, 84]. 

Waterside problems that lead to decreases in efficiency and material deterioration can be caused by a variety of mechanisms, such as electrochemical corrosion and deposition of foulants. These problems can be exacerbated by low flow, poor operational practice, process contamination, or specific stresses. It is also important to try to determine cause and effect relationships in order to provide a logical and practical water treatment solution. Such a solution will usually involve some form of cleaning, plus a combined engineering and chemical action plan. Inspection may be made easier by the use of a Boroscope or similar optical/video recording device. The color, texture, and quantity of all deposits should be noted, measurements of pits taken, and microbiological contaminants analyzed. It may be useful to conduct biocide efficiency tests on bacterial slimes. The period when a heat exchanger is open for inspection may be an opportune time for the permanent installation of ports for corrosion-monitoring probes. 

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