Deposit analysis

An irregular trough of metal loss is apparent along the circumference of the ring (Fig. 16.4). Metal loss is severe near the nozzle holes (Fig. 16.5). The corroded zone is covered with light and dark corrosion products and deposits. Analysis of these revealed substantial quantities of copper and zinc. Microscopic examinations revealed exfoliation of the aluminum ring in corroded regions. 

Offline cleaning can, and should, be entirely successful, with the simplest methods requiring, say, a 10 or 15% inhibited hydrochloric (muriatic) acid solution that is allowed to soak for some hours before neutralization, flushing, and refilling. Where the waterside deposit analysis reveals complex scales, however, it may be necessary to employ several different cleaning solvents. These solvents are added in a multistep process. 

The inspection process is the precursor to determining when a boiler needs cleaning. Visual inspections cutting out tubes and the use of chipping hammers, fiberscopes, Turner gauges, and other aids are employed, together with a full and representative deposit analysis to assess the requirement for cleaning. 

Tannins may be found bound up with magnetite in waterside tube deposits. Degradation products of amines, glycols, polymeric dispersants, chelants, and other organics may also be found and usually are reported in the deposit analysis as a loss on ignition. 

Deposit analysis Deposit binding Deposit control agents... 

Now that we have an idea of the composition of solutions of strong electrolytes, we can move on to consider what happens when we pour one solution into another. A solution of sodium chloride consists of hydrated Na+ cations and hydrated Cl- anions. Similarly, a solution of silver nitrate, AgN03, consists of hydrated Ag+ cations and hydrated NO, anions. When we mix these two aqueous solutions, we immediately get a white precipitate, a cloudy, finely divided solid deposit. Analysis shows that the precipitate is silver chloride, AgCl, an insoluble white solid (Fig. 1.6). The colorless solution remaining above the precipitate in our example contains hydrated Na+ cations and hydrated N03 anions. These ions remain in solution because sodium nitrate, NaNO is soluble in water. 

Fig. 3. Sectioning of monolith for deposit analysis. [From McArthur (27).] (Reprinted with permission from Advances in Chemistry Series. Copyright by the American Chemical Society.)...

A deposit analysis report indicating a high loss on ignition, plus significant organic solvent extractable content would tend to indicate hydrocarbon leakage. 

Organics are often present in large process cooling systems as a result of process contamination. The deposit may have a greasy, waxy, charred, or tarlike texture, but it is more usually found as a black, highly carbonized, friable material. Organic materials are usually reported in the deposit analysis as a loss on ignition. 

The SDI filter pads can also be sent into a lab for analysis of the deposit. The results of the deposit analysis will aid in the development of an appropriate pretreatment scheme, as specific species contributing to the suspended solids loading can be targeted for treatment to reduce their concentration in the feed water to the RO. 

In order to identify the problem more precisely, testing was initiated to determine the characteristics of the deposits. Pilot plant tests were conducted on municipal solid waste fuel at inlet temperatures of 1010 K, 867 K, and 839 K and using aluminum-free fuel such as wood waste. Deposit analysis indicates that the aluminum and glass are the primary elements involved in the deposit growth. 

A combination of modelling and measurement activities has been developed in order to achieve effective emission reductions or in order to monitor the progress in terms of deposition (Erisman et al 2001). While in America and Western Europe the measurement of air pollution has become practically a routine matter for Eastern European countries this is a present-day task. There are many observations in the literature that refer to the importance of wet deposition analysis, in most of Europe, North America and Asia, for obtaining information on the contribution of industrial activities to atmospheric deposition (Agrawal and Singh, 2001 Gao et al., 2001 Nilles and Conley, 2001). 

For the 100 kDa membrane, 450 mL of feed solution were introduced into the reserv oit. Pressure was adjusted to 100 kPa and the filtradon cell was fiUed up. The permeate was sampled once (sample volume 50 mL) and then recycled into the reservoir together with the retentate and filtration was repeated. This was repeated a third rime. This recycling experiment enabled the separation of concentration polarisation effects from fouling effects. The 110 mL of retentate was then also sampled. Pure water flux was measured again after each experiment with approximately 300 mL and 1000 mL of MilliQ filtered for the lOkDa and lOOkDa membranes, respectively. Membrane samples were kept in a Petri dish for deposit analysis. 

In this chapter NF was characterised in terms of membrane characteristics, solute rejection, fouling behaviour, and deposit analysis. 

Mazaheri, A.R. and Ahmadi, G. (2006) Aerosol transport and deposition analysis in a demonstration scale hot-gas filter vessel with alternate designs. Aerosol Science and Technology, 17, 623-639. 

Local weistage of the stainless steel cladding from composite tubes at ports in the waterwall (particularly primary and secondary air ports) has been attributed to hydroxide condensation [223,224]. The localized corrosion of stainless steel cladding from composite tubes at air ports of recovery boilers has been shown by deposit analysis to be a cycUcal mechanism. Laboratory tests in molten salt supported the theory that this corrosion is caused by molten NaOH [225]. 

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