Processing contaminants

It has been very difficult to predict which chemicals might be formed during food processing and might pose a hazard to consumers. It cannot be assumed that this class of substances does not exist. There are already a few established examples  

Each of these process contaminants was discovered by studies on the foods in question, either by chance or after research on chemical contamination of the environment. A more systematic approach is needed to identify processing contaminants. If this can be achieved, and this is no easy task, work on the above processing contaminants has shown how they can be researched so that levels are reduced and hence consumers protected. 

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Neutralizing Amines. Neutralizing amines are used to neutralize the acid (H" ) generated by the dissolution of carbon dioxide or other acidic process contaminants in the condensate. These amines hydrolyze when added to water and generate the hydroxide ions required for neutralization ... 

The design of the exhaust system is first influenced by the type of contaminant emission caused by the process. Contaminant emissions are possible due to... 

Zone, pressure A zone within a building or a process that is held at a given positive, negative, or neutral pressure in order to contain process contaminants. 

In this mixing process, contaminants such as solvent and/or diluents as well as their removal problems can be avoided. Degradation of the polymers is avoided by proper maintenance of the viscosity and shearing rates. 

If the steam is used in certain manufacturing processes, contamination may be undesirable, e.g. in food plant. 

Where small quantities of high-purity steam is required for electronic chip, pharmaceutical, sterilization, food preparation, and similar process applications, a small risk of steam contamination may exist. This may be caused directly by the use of amine treatments or indirectly through process contaminants or the transport of iron oxides. Consequently, alternative arrangements for steam generation are made. 

Within these tortuous systems there exists considerable opportunity for process contamination, corrosion, and equipment malfunction to occur, with cause-and-effect problems creating further impact downstream and placing additional demands on monitoring and control efforts. 

Crystalline scales and other minerals may form deposits that reduce the effectiveness of the boiler as a heat transfer device or cause fouling that can impede the flow of water and cause overheating by reducing the level of furnace cooling below design specifications. The presence of process contaminants also leads to fouling. 

Fouling, like deposition and corrosion, also takes many forms but generally involves the physical adherence to waterside surfaces of materials such as oils, process contaminants, corrosion products, and settled boiler sludges. 

NOTE Oil and process contaminants may lead to steam-condensate system deposit problems in a fashion similar to entrainment. 

Almost all larger FT and HP boiler plants employ some form of external capital equipment for MU water and FW treatment. The rationale for installing capital equipment is to eliminate (or at least minimize) the level of mineral impurities, process contaminants, and noncondensable gases entering the boiler via the FW system to reduce the potential for the development of waterside deposition, corrosion, steam contamination, and other waterside problems. 

Process contamination may, unfortunately, occur regularly in certain industries, and these process materials inevitably find their way into the FW system, and from there to the boiler, unless adequate precautions are taken. The result is severe fouling of the boiler, contamination of the steam generation process, and the potential for damage and boiler failure caused by overheating. 

Process contamination. Sticky films (LP boilers) Varnish (HP boilers) Steam discoloration FW pH fluctuations Acid corrosion Stable foams leading to carryover... 

Deposition commonly reflects a combination of physicochemical processes and localized effects. It may occur through fouling as a result of contamination by process materials, perhaps plus scaling from the supersaturation of dissolved salts, and coupled with some active under-deposit corrosion. As a consequence, deposits forming within a boiler are almost never single mineral scales but typically consist of a variable mix of scale and corrosion debris, chemical treatment residuals, process contaminants, and the like. 

Where acid process contaminant or acidic water ingress occurs, the bulk BW pH may quickly drop as low as 5.0. This may occur, for example, where there is only limited alkaline buffering of BW because of low cycles of concentration and/or high-purity FW. Where acidic incursions occur, a general thinning of the boiler tubes, drums, and shell rapidly takes place, giving rise to a clearly visible irregular surface. 

Acidic process contaminant in-leakage combining with condensate (or alternatively the decomposition of process organics, resulting in the production of acids)... 

Process contaminants such as black liquor or saponified organic oils (soaps). 

There are many process contaminants that may be inadvertently carried back with the condensate following either the purposeful injection of live steam into, say, an industrial manufacturing process or that can infiltrate the system due to a leaking heating coil, an open surge tank, or similar access point. 

Industrial process contamination results in Cross-contamination Malodors and discoloration Sticky films and varnishes Stable foams Chemical incompatability Impingement corrosion Fluctuating pH/acid corrosion... 

There are a number of major, international manufacturers of coagulant and flocculant polymers whose primary markets are high-volume users (i.e., cities, states, and national governments). There are also many smaller regional manufacturers who tend to specialize in niche markets and produce various polymer blends (organic polymers blended with various ratios of inorganic coagulants such as ACH, PAC, and alum). These polymer blends are particularly useful in industrial facilities where process contamination and difficult clarification problems may exist. 

Carryover control. This necessitates control of foam, priming (surging), misting, and process contaminants. 

Additionally, comparison of MU water usage and steam production with chemical treatment supplied, fuel consumption records, and flue gas analysis will provides early warning signs of deposit formation. Water analysis records can indicate problems of process contamination, BW carryover, and inadequate oxygen scavenging (and therefore the potential for corrosion). 

Waterside, organic-based process contaminants and deposits,... 

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