Pipe flocculators

Such pipe flocculators tend to create rather high velocity gradients at practical flow rates and need to be very long to give the required detention times. Therefore it may be useful to utilize an existing pipe as a flocculator, but it is not economic to build one for the purpose, as a concrete channel with baffles would be more compact and cost less. 

In pipes at higher Reynolds numbers, ranging from 2000 to 25 000, and therefore in turbulent flow, Doll has demonstrated the mixing and flocculation conditions in laboratory systems. These employed silica particle suspensions, flocculated with three different cationic polymers, and the turbulent root mean square velocity gradient (G) characterized the influence of flow rate on reaction rate. In West Berlin, a practical pipe flocculator has been used prior to the entry of treated waste water into a sedimentation tank, based on the concepts set out in section 4.10.3, with the pipe set out in a snake-like pattern on the ground surface. 

Figure 1 shows the particulate loading of a pipe containing gas and particulates where the nonuniformity induced by a disturbance, ie, a 90° bend, is obvious (2). A profile of concentration gradients in a long, straight, horizontal pipe containing suspended soHds is shown in Figure 2. Segregation occurs as a result of particle mass. Certain impurities, eg, metal-rich particulates, however, occur near the bottom of the pipe others, eg, oily flocculates, occur near the top (3). Moreover, the distribution may be affected by Hquid-velocity disturbances and pipe roughness.

End-of-pipe treatment refers to the application of chemical, biological, and physical processes to reduce the toxicity or volume of downstream waste. Treatment options include biological systems, chemical precipitation, flocculation, coagulation, and incineration as well as boilers and industrial furnaces (BIFs). 

Heywood, N. I. and RICHARDSON, J. F. J. Rheology 22 (1978) 599. Rheological behaviour of flocculated and dispersed aqueous kaolin suspensions in pipe flow. 

It should be noted that in all cases the size (and hence cost) of end-of-pipe treatment has a direct relationship to both the volume of effluent to be treated and the concentration of pollutants contained in the discharge. For example, the size of most physicochemical reactors (balancing, neutralizing, flocculation, sedimentation, flotation, oxidation, reduction, etc.) is determined by hydraulic factors such as surface loading rate and retention time. 

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

Cellulose acetate dust (flocculated) o——o Pipe-line dusl, Copwell... 

Flocculation during flow through pipes has also received some attention. ... 

Continuous flocculation in stirred tanks shows similar trends with regard to agitation/mixing conditions as for batch systems. The overall performance of continuous flocculation processes tends to be inferior to that which can be obtained in batch systems. This is attributed to a closer approach to equilibrium in the continuous case. In-line flocculation, by injection of polymer into turbulent flow in a pipe, is widely practised in industry and offers certain advantages. Multiple addition at several points along the length of a pipe is preferred to single-point addition. 

The pilot plant provides flocculation of neutralized mine wastewater in 240 ft of 2 in. PVC pipe, then stripping of carbon dioxide by spraying or trickling through a vertical height of 15 ft, followed by solids separation in a tarpaulin-lined basin retained by a lumber dam, and filtration through straw bales. 

Enough soap to consume Ca2+ and Mg2+ must be used before soap is useful for cleaning. Hard water leaves solid deposits called scale on pipes when it evaporates. It is not believed that hard water is unhealthy. Hardness is beneficial in irrigation water because alkaline earth ions tend to flocculate (cause to aggregate)... 

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