Laboratory simulation of belt press dewatering: Application of the Darcy equation to gravity drainage

Severin, Blaine F.; Grethlein, Hans E.

doi:10.2175/106143096x127802

Cited by 23 publications

(19 citation statements)

References 7 publications

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“…Thus, when the filter cake is formed, small particles often clog the filter pores (Severin and Grethlein, 1996). A mixture of particles with a particle size distribution between 1 and 100 μm will produce a cake with a high SRF.…”

Section: Operation and Separation Efficiencymentioning

confidence: 99%

Solid—liquid separation of animal slurry in theory and practice. A review

Hjorth

Christensen

et al. 2010

Agron. Sustain. Dev.

336

235

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-Animal slurry contains plant nutrients that are essential for crop production. However, intensive livestock production may lead to a surplus of plant nutrients on farms and, as a consequence, discharge or emission to the environment. In order to ensure that the slurry applied to fields matches the nutrient requirements of the crops, techniques have been developed to reduce the nutrient content of slurry by means of separation. This review discusses the separation technologies used for animal slurry treatment and the physical and chemical processes involved in separation. These processes need to be understood before efficient, reliable and cheap separation technologies that take into account the actual properties of slurry and the likely end-use of the separation products can be developed. A simple separation efficiency expression can be used to assess the efficiency of slurry separation. It is indeed important to measure the amount and composition of the slurry before treatment, the dry-matter-rich fraction and the liquid fraction. The separation efficiency of mechanical separators for the removal of dry matter and phosphorus (P) is ranked as follows: centrifugation > sedimentation > non-pressurized filtration > pressurized filtration. In general, the separation of total N and NH + 4 follows the same pattern, but the separation efficiency is lower than for dry matter and P. Treatment with a flocculant before separation improves separation efficiency significantly. Of the polyacrylamide polymers tested, high-molecular-weight, linear cationic polymers with a medium charge density (20-40 mol%) were found to be the most efficient flocculants. The best mechanical separation techniques for flocculated slurry are screens or filter belts. The separation efficiency of polyacrylamide-treated slurry can be improved by adding a multivalent ion to coagulate particles and for precipitation of phosphorus. Aluminium sulfate (Al 2 (SO 4 ) 3 ) or ferric chloride (FeCl 3 ) seem to be very efficient for improving the mechanical separators. Alternatively, the mineral struvite (MgNH 4 PO 4 ) may be formed by changing the slurry characteristics, such as by the addition of magnesium (Mg) or by increasing the pH to 9. The struvite crystals are removed during solid-liquid separation. The products of the solid-liquid separation may be further treated by evaporation, membrane filtration or ammonia stripping in order to obtain the desired end-products; however, low-maintenance and/or cost-efficient operation of these post-treatments has not yet been demonstrated. The separation should be developed as a whole-system approach, paying attention to parameters such as the value of end-products, environmental consequences and economy.

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Section: Operation and Separation Efficiencymentioning

confidence: 99%

Solid—liquid separation of animal slurry in theory and practice. A review

Hjorth

Christensen

et al. 2010

Agron. Sustain. Dev.

336

235

View full text Add to dashboard Cite

show abstract

“…2 As the concentration of dry material is low in sludge and manure, solid-liquid separation is an important part of pretreatment in order to lower transportation costs, minimize the need for storage capacity, or increase the energy output from incineration. There are several methods for solid-liquid separation, including gravity drainage; for example, organic slurries can be drained using belt filter presses 3 or sludge drying reed beds. 4 The critical pressure above which the dewatering rate is constant has been determined to be in the range of 5-50 kPa for biological sludge.…”

Section: Introductionmentioning

confidence: 99%

“…Applying such high pressures leads to the problem of transforming and applying the obtained cake resistances to the low-pressure conditions encountered in gravity drainage experiments. Furthermore, studies that describe the gravity drainage processes of inorganic particles 7,8 and biological sludge, 3,9 for example, do not include cake compression in the model. Cake compression may influence the drainage processes, but it is not known whether cakes are compressible at the low pressure achieved during drainage.…”

Section: Introductionmentioning

confidence: 99%

Gravitational drainage of compressible organic materials

et al. 2010

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A model was developed to simulate drainage of compressible particle suspensions, and study how cake compression and volumetric load influence the process. The input parameters were settling velocity, cake resistance and compressibility. These parameters were found using a new experimental method. Dextran-MnO 2 particle suspensions were drained as these resemble organic waste slurries with respect to settling and compressibility. It was demonstrated that cake compressibility must be taken into account to obtain adequate simulations. This implies that pressurized filtration resistances cannot be used for drainage simulations. In the filtration step, a distinct increase of dry matter from top to bottom of the cake was observed. During the subsequent consolidation, the cake compressed and a uniform dry matter profile was found. The final dry matter content of the cake increased with feed concentration and volumetric load. The drainage time increased proportionally with feed concentration and, more importantly, proportionally with squared volumetric load. V V C 2010 American Institute of Chemical Engineers AIChE J, 56: 3099-3108, 2010

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“…Finally, increasing pressures (and shear) are applied at each successive roller, by decreasing the turn radius, to give continued expression and, ultimately, the final dewatered cake. These latter stages will provide unsatisfactory water removal, lateral escape of material off the belts, and loading limitations [1,2] if effective chemical conditioning is not effected in the initial stage. These problems should be observable in a good lab simulation procedure as well.…”

Section: Introductionmentioning

confidence: 99%