Impinging fouling

Concentrations of tar fouling beaches of southeast Florida and the Florida Keys averaged 9.8 g m-2, an order of magnitude greater than the mean for the rest of the state (31). Remarkably, there was no significant increase over the amount observed on Florida beaches 30 years previously (32). Further, there was no evidence that the oil anticipated from the IXTOC-I blowout ever impinged upon the beaches of Florida (14, 33). 

Impingement-plate scrubbers are easy to clean and maintain and are not subject to fouling as packed-bed wet scrubbers are, hence they are more suited to PM control and there are no practical limits to inlet PM concentrations. 

Flame impingement. This is often caused by dirty burner tips, lack of combustion air, poorly designed burners, high burner tip pressure, improper adjustment of the burner, or improper draft. I have seen a heater in Cartagena, Colombia, with the flames being forced outward against the upper radiant wall tubes. The problem was an extreme positive pressure in the firebox, due to excessive pressure drop of the flue gas in the fouled convective section. 

A variety of animals and plants, as well as colonies of microorganisms, may deposit from natural sea water onto the metal surface. The life processes and decomposition products may contribute directly to attack on the metal. Fouling may obstruct flow in heat exchangers and pipes, leading to such corrosive effects as are caused by overheating or impingement at local high-water velocities. 

Titanium. Unlike other metals, titanium normally does not pit, is not susceptible to stress corrosion, is free from local corrosion under fouling organisms, is free from impingement and cavitation attack at velocities which attack copper-base alloys, and is not susceptible to sulfide attack in contaminated sea water. Experiments with water velocities at 20 to 50 feet per second show no attack on titanium. 

Robustness test for the impinging-jet mixer - fouling sensitivity during precipitations... 

Calculate the pressure drop for the conditions of Example 7.20. Assume that the nozzle velocities are 5 ft/s (1.52 m/s), that the fluid density is 55 lb/ft3 (881 kg/m3), and that there are 24 baffles. Assume that there is also an impingement plate at the inlet nozzle. Calculate the pressure drop for both fouled and clean conditions. 

In operation with particulates containing gases, the LFR is more prone to fouling than is the PPR. Similarly, as in a normal fixed bed, dust particles may be caught by impingement on solid surfaces, and this may give rise to plugging of the bed. However,... 

Shell side corrosion is caused by decomposition of the bath. (The decomposition products of amines and glycols are corrosive.) Some decomposition and corrosion are inevitable however, excessive decomposition is usually due to overheating near the firetube. Corrosion inhibitors are commonly added. There are numerous reasons for overheating the bath localized ineffective heat transfer caused by fouling, excessive flame impingement, etc. An improper flame can sometimes be modified without system shutdown. Fouling, however, requires removal of the firetube. 

We apply simple effective medium models in an attempt to understand the diffusion process in the complex pore network of a porous SiC sample. There is an analogy between the quantities involved in the electrostatics problem and the steady state diffusion problem for a uniform external diffusion flux impinging on a coated sphere. Kalnin etal. [17] provide the details of such a calculation for the Maxwell Garnett (MG) model [18]. The quantity involved in the averaging is the product of the diffusion constant and the porosity for each component of the composite medium. The effective medium approach does not take into account possible effects due to charges on the molecules and/or pore surfaces, details in the size and shape of the protein molecules, fouling (shown to be negligible in porous SiC), and potentially important features of the microstructure such as bottlenecks. 

Because the sulfur contained in crude oil is concentrated in the residue material, residual fuel sulfur levels naturally vary from less than 1 to over 6%. The sulfur level is not a critical factor for the combustion process as long as the flue gases do not impinge on cool surfaces. However, residual fuels may contain large quantities of heavy metals such as nickel and vanadium these produce ash upon burning and can foul the burner systems. Such contaminants are not easily removed and usually lead to lower market prices for fuel oils with high metal contents. 

It may be concluded from the data that the severe fouling experienced in RDF fuelled boiler plant, is due to the volatilisation of alkali metals from the fuel bed. Oxides in reaction with acidic oxides of sulphur, or sulphates, are extremely sticky at the temperatures encountered in the equipment and tend to adhere to the cooler heat transfer surfaces. In coal burning, the alkali metal compounds constitute a sticky matrix which retains the impinging fly-ash, whereas in RDF combustion the concentration of alkali salts in the flue gas is so high that the rate of condensation exceeds the rate of fly ash retention. 

---