Factors Affecting Filterability

In this thesis the factors affecting lime mud filterability were studied. In the literature part there is information about recausticizing process, lime mud properties and filterability, and general filtration theory. In the experimental part the properties of lime mud particles and the properties of lime mud filter cake were investigated and the behavior of lime mud precoat was studied. The experiments were also carried out with R-PCC (rhombohedral precipitated calcium carbonate). The filtration and precoat studies were performed with a laboratory scale pressure filter. The pressure differences used were between 0.25-1.50 bars. Six different lime mud samples with varying amount of impurities and two R-PCC samples were used in the experiments. The average specific cake resistance of different lime mud samples varied quite extensively. The most influential factor affecting the lime mud filterability and dry solids content was found to be silica content. As the lime mud contained silica, the average specific cake resistance was high and the lime mud dryness was low. If the lime mud samples containing silica were not taken into account, the smaller the mean particle size, the higher the average specific cake resistance of the lime mud. The R-PCC had also a high average specific cake resistance, which was because of small particle size. In addition, the pressure difference affected the average specific cake resistance of some lime mud samples. In those cases lime mud was compressible material. During the precoat experiments the lime mud samples having the largest mean particle sizes, compressed. However, the average specific cake resistances of the filtration and precoat part were approximately the same magnitude. A brief displacement by air did not affect the behavior of the precoat. Instead, vibration and a brief but relatively great change in pressure difference had a slight influence.

Höyryn käyttö suodinkakun pesussa ja kuivauksessa

Työssä käsitellään suodinkakkujen kuivapitoisuuksien muuttumista, kun kuivauksessa käytetään paineilman sijasta kylläistä höyryä.

Recovery of Hemicelluloses from Wood Hydrolysates by Membrane Filtration

Hemicelluloses are among the most important natural resources that contain polysaccharides. In this study the separation and purification of hemicelluloses from water extraction liquors containing wood hemicelluloses, lignin compounds and monosaccharide by using membrane filtration was investigated. The isolation of the hemicelluloses from the wood hydrolysates was performed in two steps: concentration of high molar mass hemicelluloses by ultrafiltration and separation of low molar mass hemicelluloses from monomeric sugars using tight ultrafiltration membranes. The purification of the retained hemicelluloses was performed by diafiltration. During the filtration experiments, the permeate flux through ultrafiltration and tight ultrafiltration membranes was relatively high. The fouling ability of the used membranes was relatively low. In our experiments, the retention of hemicelluloses using two filtration steps was almost complete. The separation of monosaccharides from hemicelluloses was relatively high and the purification of hemicelluloses by diafiltration was highly efficient. The separation of lignin from hemicelluloses was partially achieved. Diafiltration showed potential to purify retained hemicelluloses from lignin and other organics. The best separation of lignin from hemicelluloses in the first filtration step was obtained using the UC005 membrane. The GE-5 and ETNA01PP membranes showed potential to purify and separate lignin from hemicelluloses. However, the feed solution of the second filtration stages (from different ultrafiltration membranes) affected the permeate flux and the separation of various extracted compounds from hemicelluloses. The GE-5 and ETNA01PP membranes gave the efficient purification of the hemicelluloses when using diafiltration. Separation of degraded xylan from glucomannan (primary spruce hemicelluloses) was also possible using membrane filtration. The best separation was achieved using the GE-5 membrane. The retention of glucomannan was three times higher than xylan retention.

Weight filtration on the cohomology of complex analytic spaces

We extend Deligne's weight filtration to the integer cohomology of complex analytic spaces (endowed with an equivalence class of compactifications). In general, the weight filtration that we obtain is not part of a mixed Hodge structure. Our purely geometric proof is based on cubical descent for resolution of singularities and Poincaré-Verdier duality. Using similar techniques, we introduce the singularity filtration on the cohomology of compactificable analytic spaces. This is a new and natural analytic invariant which does not depend on the equivalence class of compactifications and is related to the weight filtration.

Development of a Filter Aid Proportioning, Mixing, and Feeding System for a Polishing Filter

The purpose of this work was to study the characteristics of the most commonly used filter aid materials and their influences on the design of proportioning, mixing, and feeding system for polishing filter family. Based on the literature survey and hands-on experience a system was designed with defined equipment and capital and operating costs. The system was designed to serve precoating and bodyfeeding applications and is easily extended to be used in multiple filter processes. Also a test procedure was carried out where influences of flux and filter cloths to accumulated cake were studied. Filter aid is needed in challenging conditions to improve filtration efficiency and cleaning, and thus extend the operating life of the filter media. Filter aid preparation and feeding system was designed for the use of two different filter aids; precoat and bodyfeed. Precoating is used before the filtration step initiates. If the solids in the filterable solution have a tendency to clog the filter bag easily, precoat is used on the filter bag to obtain better filtration efficiency and quality. Diatomite or perlite is usually used as a precoating substance. The intention is to create a uniform cake to the overall surface of the filter cloth, with predetermined thickness, 2 – 5 mm. This ensures that the clogging of the filter cloth is reduced and the filtration efficiency is increased. Bodyfeed is used if the solids in the filterable solution have a tendency to form a sticky impermeable filter cake. The cake properties are enhanced by maintaining the permeability of the accumulating cake by using the filter aid substance as bodyfeed during the filtration process.

Electrochemical Characterisation of Filter Media Properties and Their Exploitation in Enhanced Filtration

Streaming potential measurements for the surface charge characterisation of different filter media types and materials were used. The equipment was developed further so that measurements could be taken along the surfaces, and so that tubular membranes could also be measured. The streaming potential proved to be a very useful tool in the charge analysis of both clean and fouled filter media. Adsorption and fouling could be studied, as could flux, as functions of time. A module to determine the membrane potential was also constructed. The results collected from the experiments conducted with these devices were used in the study of the theory of streaming potential as an electrokinetic phenomenon. Several correction factors, which are derived to take into account the surface conductance and the electrokinetic flow in very narrow capillaries, were tested in practice. The surface materials were studied using FTIR and the results compared with those from the streaming potentials. FTIR analysis was also found to be a useful tool in the characterisation of filters, as well as in the fouling studies. Upon examination of the recorded spectra from different depths in a sample it was possible to determine the adsorption sites. The influence of an external electric field on the cross flow microflltration of a binary protein system was investigated using a membrane electroflltration apparatus. The results showed that a significant improvement could be achieved in membrane filtration by using the measured electrochemical properties to help adjust the process conditions.

Towards integrated operation of membrane bioreactors : effects of aeration on biological and filtration performance

Two experimental studies evaluated the effect of aerobic and membrane aeration changes on sludge properties, biological nutrient removal and filtration processes in a pilot plant membrane bioreactor. The optimal operating conditions were found at an aerobic dissolved oxygen set-point (DO) of 0.5mgO2L-1 and a membrane specific aeration demand (SADm) of 1mh-1, where membrane aeration can be used for nitrification. Under these conditions, a total flow reduction of 42% was achieved (75% energy reduction) without compromising nutrient removal efficiencies, maintaining sludge characteristics and controlled filtration. Below these optimal operating conditions, the nutrient removal efficiency was reduced, increasing 20% for soluble microbial products, 14% for capillarity suction time and reducing a 15% for filterability. Below this DO set-point, fouling increased with a transmembrane pressure 75% higher. SADm below 1mh-1 doubled the values of transmembrane pressure, without recovery after achieving the initial conditions

Biosorption and removal of chromium from water by using moringa seed cake (Moringa oleifera Lam.)

This study evaluated the adsorption capacity of chromium from contaminated aqueous solutions by using Moringa oleifera Lam. seeds. Parameters such as solution pH, adsorbent mass, contact time between solution and adsorbent, isotherms, thermodynamic, kinetics, and desorption were evaluated. The maximum adsorption capacity (Qm) calculated to be 3.191 mg g-1 for the biosorbent. Activated carbon was used for comparison purposes in addition to the biosorbent. The best fit was obtained by the Langmuir model for both adsorbents. The average desorption value indicated that both the biosorbent and activated carbon have a strong interaction with the metal. The results showed that the biosorbent has advantages owing to its low cost and efficiency in Cr3+ removal from contaminated waters.

Pretreatment in membrane filtration of wood hydrolysate

Interest in recovery of valuable components from process streams has increased in recent years. Purpose of biorefinery is to utilize components that otherwise would go to waste. Hemicelluloses, for example, could be utilized in production of many valuable products. One possible way to separate and fractionate hemicelluloses is membrane filtration. In the literature part of this work membrane fouling in filtration processes of pulp and paper process- and wastewaters was investigated. Especially purpose was to find out the possible fouling compounds, after which facilities to remove or modify such components less harmful were studied. In the experimental part different pretreatment methods, mainly to remove or degrade lignin from wood hydrolysate, were studied. In addition, concentration of hemicelluloses and separation from lignin were examined with two ultrafiltration membranes; UFX5 and RC70PP. Changes in feed solution, filtration capacity and fouling of membranes were used to evaluate the effects of pretreatment methods. Changes in hydrolysate composition were observed with different analysis methods. Filtration of hydrolysate proved to be challenging, especially with the UFX5 membrane. The more hydrophilic RC70PP membrane did not seem to be fouled as severely as the UFX5 membrane, according to pure water flux measurements. The UFX5 membrane retained hemicelluloses rather well, but problems arose from rapid flux decline resulting from concentration polarization and fouling of membrane. Most effective pretreatment methods in the case with the UFX5 membrane proved to be prefiltration with the RC70PP membrane, activated carbon adsorption and photocatalytic oxidation using titanium dioxide and UV radiation. An additional experiment with PHW extract showed that pulsed corona discharge treatment degraded lignin quite efficiently and thus improved filtration capacity remarkably, even over six times compared to the filtration with untreated extract.

Online Ultrasound Measurements of Membrane Compaction

There are several filtration applications in the pulp and paper industry where the capacity and cost-effectiveness of processes are of importance. Ultrafiltration is used to clean process water. Ultrafiltration is a membrane process that separates a certain component or compound from a liquid stream. The pressure difference across the membrane sieves macromolecules smaller than 0.001-0.02 μm through the membrane. When optimizing the filtration process capacity, online information about the conditions of the membrane is needed. Fouling and compaction of the membrane both affect the capacity of the filtration process. In fouling a “cake” layer starts to build on the surface of the membrane. This layer blocks the molecules from sieving through the membrane thereby decreasing the yield of the process. In compaction of the membrane the structure is flattened out because of the high pressure applied. The higher pressure increases the capacity but may damage the structure of the membrane permanently. Information about the compaction is needed to effectively operate the filters. The objective of this study was to develop an accurate system for online monitoring of the condition of the membrane using ultrasound reflectometry. Measurements of ultrafiltration membrane compaction were made successfully utilizing ultrasound. The results were confirmed by permeate flux decline, measurements of compaction with a micrometer, mechanical compaction using a hydraulic piston and a scanning electron microscope (SEM). The scientific contribution of this thesis is to introduce a secondary ultrasound transducer to determine the speed of sound in the fluid used. The speed of sound is highly dependent on the temperature and pressure used in the filters. When the exact speed of sound is obtained by the reference transducer, the effect of temperature and pressure is eliminated. This speed is then used to calculate the distances with a higher accuracy. As the accuracy or the resolution of the ultrasound measurement is increased, the method can be applied to a higher amount of applications especially for processes where fouling layers are thinner because of smaller macromolecules. With the help of the transducer, membrane compaction of 13 μm was measured in the pressure of 5 bars. The results were verified with the permeate flux decline, which indicated that compaction had taken place. The measurements of compaction with a micrometer showed compaction of 23–26 μm. The results are in the same range and confirm the compaction. Mechanical compaction measurements were made using a hydraulic piston, and the result was the same 13 μm as obtained by applying the ultrasound time domain reflectometry (UTDR). A scanning electron microscope (SEM) was used to study the structure of the samples before and after the compaction.

Utilisation of magnetic field in membrane filtration

As it is known, the major problem of membrane filtration is fouling of membrane during the filtration process. There are a lot of methods to prevent or reduce fouling. One very little studied method is applying of magnetic field in membrane filtration. Magnetic field has such advantages as bulk, contact free, nondestructive impact on the sample, thus it can be combined with different types of processes. In addition, the use of magnetic fields has given positive results in various areas of science and life. So, the present thesis is devoted to the research of influence of magnetic field on performances of nanofiltration. In the literature part of the thesis a short description of membrane process and mechanism of reorientation of nanoparticals in magnetic field is presented. The utilization of magnetic field in different spheres of life, in general, and membrane area, in particular, is represented. In the experimental part the influence of magnetic field created by two permanent magnets on filtration of two solutions (citric acid and sodium dodecyl sulfate) was investigated. Factors, which affect on the impact of magnetic field was estimated. The effect of magnetic field was evaluated by measuring a change of pure water permeability after the filtration of model solution. This work demonstrated that direction of magnetic field and the type of molecules of filtered solution has significant effect to the efficiency of nanofiltration. Utilization of magnetic field might increase retention of membrane and flux through membrane and reduce fouling.

Water treatment by multistage filtration system with natural coagulant from Moringa oleifera seeds

This study presents an evaluation of a pilot multistage filtration system (MSF) with different dosages, 131 mg L-1 and 106 mg L-1, of the natural coagulant extracted from Moringa oleifera seeds in pre-filtration and slow filtration stages, respectively. The system was comprised by a dynamic pre-filter unit, two upflow filters in parallel and four slow filters in parallel, and in one of the four filters had the filter media altered. The performance of the system was evaluated by monitoring some water quality parameters such as: turbidity, apparent color and slow filter load loss. The stages that have received the coagulant solution had better treatment efficiency compared with the steps without it. However, the direct application of the coagulant solution in the slow filter caused rapid clogging of the non-woven blanket and shorter career length.

Impact of irrigation on yield and energy balance of the production of oil and cake of two sunflower varieties

The energy balance for the production of sunflower oil and cake was carried out during the agricultural and industrial stage phase, where it was considered a cold extraction by hydraulic pressing, with the plant location in a rural area with a radius of 30km range. Data on productivity was used in two varieties of sunflower (Helio 358 and Aguará 04) grown in different seasons (2007/2008, 2008/2009), under different irrigation levels. Data showed that irrigation resulted in an increase in productivity of both varieties, and the best response was observed for Aguará 04 variety. Moreover, the increased intensity of irrigation negatively affected the energy balance, reducing the ratio between energy produced and energy used in the production chain. The most significant inputs in the energy intake were fertilizer followed by diesel oil, when irrigation was not used for. When the irrigation technique was used, the most significant inputs, in order of representativeness, were: energy, fertilizer and equipment.

Acidic dissolution of iron oxides and regeneration of a ceramic filter medium

The dewatering of iron ore concentrates requires large capacity in addition to producing a cake with low moisture content. Such large processes are commonly energy intensive and means to lower the specific energy consumption are needed. Ceramic capillary action disc filters incorporate a novel filter medium enabling the harnessing of capillary action, which results in decreased energy consumption in comparison to traditional filtration technologies. As another benefit, the filter medium is mechanically and chemically more durable than, for example, filter cloths and can, thus, withstand harsh operating conditions and possible regeneration better than other types of filter media. In iron ore dewatering, the regeneration of the filter medium is done through a combination of several techniques: (1) backwashing, (2) ultrasonic cleaning, and (3) acid regeneration. Although it is commonly acknowledged that the filter medium is affected by slurry particles and extraneous compounds, published research, especially in the field of dewatering of mineral concentrates, is scarce. Whereas the regenerative effect of backwashing and ultrasound are more or less mechanical, regeneration with acids is based on chemistry. The chemistry behind the acid regeneration is, naturally, dissolution. The dissolution of iron oxide particles has been extensively studied over several decades but those studies may not necessarily be directly applicable in the regeneration of the filter medium which has undergone interactions with the slurry components. The aim of this thesis was to investigate if free particle dissolution indeed correlates with the regeneration of the filter medium. For this purpose, both free particle dissolution and dissolution of surface adhered particles were studied. The focus was on acidic dissolution of iron oxide particles and on the study of the ceramic filter medium used in the dewatering of iron ore concentrates. The free particle dissolution experiments show that the solubility of synthetic fine grained iron oxide particles in oxalic acid could be explained through linear models accounting for the effects of temperature and acid concentration, whereas the dissolution of a natural magnetite is not so easily explained by such models. In addition, the kinetic experiments performed both support and contradict the work of previous authors: the suitable kinetic model here supports previous research suggesting solid state reduction to be the reaction mechanism of hematite dissolution but the formation of a stable iron oxalate is not supported by the results of this research. Several other dissolution mechanisms have also been suggested for iron oxide dissolution in oxalic acid, indicating that the details of oxalate promoted reductive dissolution are not yet agreed and, in this respect, this research offers added value to the community. The results of the regeneration experiments with the ceramic filter media show that oxalic acid is highly effective in removing iron oxide particles from the surface of the filter medium. The dissolution of those particles did not, however, exhibit the expected behaviour, i.e. complete dissolution. The results of this thesis show that although the regeneration of the ceramic filter medium with acids incorporates the dissolution of slurry particles from the surface of the filter medium, the regeneration cannot be assessed purely based upon free particle dissolution. A steady state, dependent on temperature and on the acid concentration, was observed in the dissolution of particles from the surface even though the limit of solubility of free iron oxide particles had not been reached. Both the regeneration capacity and efficiency, with regards to the removal of iron oxide particles, was found to be temperature dependent, but was not affected by the acid concentration. This observation further suggests that the removal of the surface adhered particles does not follow the dissolution of free particles, which do exhibit a dependency on the acid concentration. In addition, changes in the permeability and in the pore structure of the filter medium were still observed after the bulk concentration of dissolved iron had reached a steady state. Consequently, the regeneration of the filter medium continued after the dissolution of particles from the surface had ceased. This observation suggests that internal changes take place at the final stages of regeneration. The regeneration process could, in theory, be divided into two, possibly overlapping, stages: (1) dissolution of surface-adhered particles, and (2) dissolution of extraneous compounds from within the pore structure. In addition to the fundamental knowledge generated during this thesis, tools to assess the effects of parameters on the regeneration of the ceramic filter medium are needed. It has become clear that the same tools used to estimate the dissolution of free particles cannot be used to estimate the regeneration of a filter medium unless only a robust characterisation of the order of regeneration efficiency is needed.

The Combined treatment of UV Light and Titanium Dioxide (TiO2) in Grease Filtration Technique

The aim of this thesis was to identify the best grease removal technique with the application of low power of UV light to TiO2 coated grease filters. The treatment with various power series of ozone generating and ozone free lamps to normal grease filters and TiO2 coated grease filters were examined and the obtained results are compared to each other in this paper. The effect of ozone reaction was observed and compared with the effect of TiO2. The experiments were solely based on the photo oxidation and photo catalytic oxidation reactions. TiO2 is a green catalyst used in the photocatalytic reaction. Sunflower oil was used for grease production and tetracholoroethylene as a solvent. Grease samples were collected from the ventilation duct connected to the cooking hood system. Sample extraction was done in ultrasonic bath with the principle of sonication. The sample analysis was done by FTIR machine. The result determining the concentration of grease was the quantification of saturated C-H bonds in the chosen peak group of the spectrum. A very low power of UVC light functions perfectly with the Titanium dioxide. The experimental results have shown the combined treatment of titanium dioxide and UV light is an effective method in grease removal process. The photocatalytic reaction with titanium dioxide is better than photo oxidation reaction with ozone treatment. Photocatalytic reaction is environmentally friendly, energy efficient and economical.