In the absence of any significant legislation, paper recycling in South Africa has grown to a respectable recovery rate of 43% in 2008, driven mainly by the major paper manufacturers. Recently introduced legislation will further boost the recovery rate of recycled paper. Domestic household waste represents the major remaining source of recycled paper. This source will introduce greater variability into the paper streams entering the recycling mills, which will result in greater process variability and operating difficulties. This process variability manifests itself as lower average brightness or increased bleaching costs. Deinking plants will require new techniques to adapt to the increasingly uncertain composition of incoming recycled paper streams. As a developing country, South Africa is still showing growth in the publication paper and hygiene paper markets, for which recycled fibre is an important source of raw material. General deinking conditions pertaining to the South African tissue and newsprint deinking industry were obtained through field surveys of the local industry and assessment of the current and future requirements for deinking of differing quality materials. A large number of operating parameters ranging from waste mixes, process variables and process chemical additions, typically affect the recycled paper deinking process. In this study, typical newsprint and fine paper deinking processes were investigated using the techniques of experimental design to determine the relative effects of process chemical additions, pH, pulping and flotation times, pulping and flotation consistencies and pulping and flotation temperatures on the final deinked pulp properties. Samples of recycled newsprint, magazines and fine papers were pulped and deinked by flotation in the laboratory. Handsheets were formed and the brightness, residual ink concentration and the yield were measured. It was determined that the type of recycled paper had the greatest influence on final brightness, followed by bleaching conditions, flotation cell residence time and flotation consistency. The residual ink concentration and yield were largely determined by residence time and consistency in the flotation cell. The laboratory data generated was used to train artificial neural networks which described the laboratory data as a multi-dimensional mathematical model. It was found that regressions of approximately 0.95, 0.84 and 0.72 were obtained for brightness, residual ink concentration and yield respectively. Actual process data from three different deinking plants manufacturing seven different grades of recycled pulp was gathered. The data was aligned to the laboratory conditions to take into account the different process layouts and efficiencies and to compensate for the differences between laboratory and plant performance. This data was used to validate the neural networks and select the models which best described the overall deinking performances across all of the plants. It was found that the brightness and residual ink concentration could be predicted in a commercial operation with correlations in excess of 0.9. Lower correlations of ca. 0.5 were obtained for yield. It is intended to use the data and models to develop a predictive model to facilitate the management and optimization of a commercial flotation deinking processes with respect to waste input and process conditions. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.

Techn. Universiẗat, Diss., 2002--Darmstadt.

Résumé non communiqué par le doctorant. / Résumé non communiqué par le doctorant.

Les objectifs de ce travail étaient de déterminer les sources et le devenir de l’arsenic dans une papeterie vosgienne, et en particulier dans sa station d’épuration, afin de comprendre les variations de la concentration en arsenic dans l’effluent traité par la station et rejeté dans la Moselle.Les papiers récupérés utilisés pour la production de pâte désencrée représentent la source majoritaire d’arsenic pour la papeterie, puis les combustibles incinérés dans le secteur énergie. Les sorties majoritaires sont les cendres produites par le secteur énergie, puis le papier produit. Le devenir de l’arsenic dans le procédé de désencrage est complexe et implique des phénomènes de transfert entre le circuit de la pâte à papier et le circuit des eaux. L’arsenic présent dans les eaux blanches semble provenir des matières en suspension. Des dysfonctionnements dans le secteur énergie ont causé le départ de cendres produites dans la chaudière à la station d’épuration via les eaux de lavage du laveur de fumées. Ces cendres peuvent avoir une concentration en arsenic très importante et pourraient être l’une des causes des dépassements de la limite de rejet en arsenic. La station d’épuration peut éliminer de la phase aqueuse jusqu’à 50 % de l’arsenic entrant à la station après neutralisation/décantation et traitement par boues activées. Un traitement tertiaire par coagulation (par des sels d’aluminium) / floculation / flottation permet de diminuer encore la concentration en arsenic dans le rejet en fonction des conditions de fonctionnement / This study was about the sources and the fate of arsenic in a pulp and paper mill located in the Vosges, and particularly in the wastewater treatment plant, in order to understand the variations of the arsenic concentration in the treated effluent discharged in the Moselle River.The recovered papers used for the production of deinked pulp are the main source of arsenic for the pulp and paper mill, followed by the solid fuels incinerated in the boiler of the energy area of the mill. The main outputs are the ashes produced by the boiler, then the produced paper. The fate of the arsenic in the deinking process is complex and involves transfer phenomena between the pulp and the white water of the process. Arsenic present in white water could come from the suspended solids. Malfunctions in the energy area have caused the departure of ashes to the wastewater treatment plant via the washing water of the flue gas washer. Those ashes may contain a high arsenic concentration and could be one of the sources of the large variations of the arsenic concentration in the effluent of the wastewater treatment plant. This wastewater treatment plant is able to eliminate up to 50% of arsenic of the effluent thanks to neutralization/decantation and biotreatment by activated sludge. A tertiary treatment by coagulation (with aluminum salts) / flocculation / flotation permits to decrease the arsenic concentration in the effluent according to the operating conditions

No description available.

Abstract Paper recycling is an ecological strategy for disposing of waste paper, but more importantly, recovered paper is an important source of raw material in the paper and board industry. Deinked pulp production from recovered paper has proved economically viable by comparison with virgin fibre pulp manufacturing, but this viability is now threatened by increasing waste disposal costs, as up to 25% of the raw material available for deinked pulp production can end up in the reject streams, which then have to be disposed of. The most common practice at present is incineration and disposal of the resulting ash in landfills, but tightening legislation has meant that landfills have become very expensive and are likely to be completely banned in the near future. Thus new ways have to be sought for managing the waste problem in deinked pulp production in order to ensure that the recycled paper production remain both economically and environmentally feasible. The aim of this thesis was to study means of improving the material efficiency of a deinked pulp mill without excessively detracting from end product quality or the performance of the combined sludge dewatering stage. First, an analytical procedure was developed for determining the utilisation potential of reject streams, and a considerable potential for material recovery from these streams was identified. The results presented here show that 80% of the most valuable long fibres from the fine-screening rejects and 15% of the fine material from the flotation froth reject can be recovered. Altogether, with the simultaneous recovery of both categories of reject, it would be possible to improve the material efficiency at the deinked pulp mill by a total of about 5 percentage units, which can be considered significant for process efficiency. Moreover, this would enable the fibre content of the combined sludge to be kept above a certain limit, so that the combined sludge dewatering properties would not be affected. Consequently, the results presented in this thesis provide several widely applicable means for improving the resource efficiency of a deinked pulp mill. / Tiivistelmä Paperin kierrätys uusiksi paperituotteiksi on ympäristöystävällinen tapa jätepaperin käsittelemiseksi. Uusiomassan valmistus on myös taloudellisesti kannattavaa verrattuna paperimassan valmistukseen neitseellisistä raaka-aineista. Taloudellinen kannattavuus on kuitenkin vaarassa jätemaksujen alati kasvaessa, sillä siistausmassan valmistuksessa jopa 25 % kierrätyspaperiraaka-aineesta päätyy jätejakeisiin, jotka hävitetään yleisesti polttamalla ja läjittämällä syntynyt tuhka kaatopaikalle. Lainsäädäntö on rajoittanut kaatopaikkasijoittamista ja se on nykyään hyvin kallista. Tulevaisuudessa jätteiden kaatopaikkasijoittaminen voi olla jopa täysin kiellettyä. Jäteongelman ratkaisemiseen tarvitaan siis uusia menetelmiä, jotta kierrätyspaperin valmistus säilyisi sekä taloudellisista että ympäristöllisistä näkökulmista kannattavana toimintana. Tämän väitöskirjatyön tavoitteena oli etsiä keinoja parantaa siistausmassan valmistuksen resurssitehokkuutta palauttamalla käyttökelpoisia materiaaleja jätevirroista takaisin prosessiin siten, ettei heikennetä lopputuotteen laatua eikä lietteidenkäsittelyprosessin toimintaa. Väitöstyön alussa kehitettiin analyysiproseduuri rejektivirtojen hyötykäyttöpotentiaalin arvioimiseksi ja siistamon rejektijakeissa havaittiin merkittävästi hyödynnettävää materiaalia. Tulokset osoittavat, että 80 % hienolajittelun rejekteissä poistuneista arvokkaista pitkistä kuiduista voidaan palauttaa takaisin prosessiin. Lisäksi flotaation vaahtorejektistä voidaan palauttaa 15 % hienoainetta. Palauttamalla yhtäaikaisesti sekä kuituja hienolajittelun rejekteistä että hienoainetta flotaation vaahtorejektistä, voidaan siistausmassan valmistuksen materiaalitehokkuutta parantaa yhteensä noin 5 prosenttiyksikköä, mikä on merkittävä parannus prosessitehokkuuteen. Kuitujen ja hienoaineen samanaikainen palauttaminen pitää lisäksi lietteiden käsittelyssä seoslietteen kuitupitoisuuden tarpeeksi korkeana, jotta sen vedenerotusominaisuudet säilyvät hyvinä. Tämän tutkimuksen tuloksena löydettiin siis useita laajalti sovellettavissa olevia keinoja siistausmassan valmistuksen resurssitehokkuuden parantamiseksi.

Abstract The amount of printing ink in a pulp suspension produced from recovered paper and its impact on overall brightness is commonly estimated from the reflectance-based ink content measured at a wavelength of 700 nm or 950 nm. The method uses a light scattering coefficient that can be measured from a slightly translucent test medium, i.e. of an opacity less than 97%. This is the case with machine-made papers in most instances. Alternatively, suitable opacity can be achieved by preparing a standard low-grammage sheet on a wire screen, but this results in poor retention of fibre fines, mineral fillers and printing inks, which is especially detrimental to ink measurement when the pulp suspension contains substantial amounts of printing inks. Hence opaque pads are often prepared on filter paper to achieve high retention. Unfortunately their high opacity prevents measurement of the light scattering coefficient, and thus a constant coefficient must be used for the determination of ink content. The aim of this thesis was to clarify the effects of retention and fine material changes on the light scattering coefficient in ink content measurement. The results showed that the light scattering properties of pulp in the wavelength region used for ink content analysis do not remain constant when the fine material content varies. The grade of the recovered paper, hyperwashing and flotation alter the fine material content and thus affect the light scattering. Printing ink also affects light scattering, but its practical impact is smaller than that of fibre fines and mineral fillers. The light scattering coefficient used for each ink content measurement needs to be representative, otherwise a systematic bias in ink content measurements may result from changes in the nature of the fine material and in its content. It is recommended that the light scattering coefficient should be measured in order to avoid this. The measurement should preferably be performed from a low-grammage sheet prepared on filter paper, as this ensures high retention and a measured value that represents better the initial state of the pulp suspension. / Tiivistelmä Mustepitoisuusmittaus perustuu hajaheijastukseen joko 700 nm tai 950 nm aallonpituudella ja sitä käytetään usein arvioitaessa keräyspaperista valmistetun massasuspension soveltuvuutta painopaperien valmistukseen ja painomusteen vaikutusta massan vaaleuteen. Mustepitoisuuden mittauksessa käytetään valonsirontakerrointa, joka voidaan mitata hieman läpikuultavasta näytteestä eli näytteen opasiteetin on oltava pienempi kuin 97 %. Tämä opasiteettiraja toteutuu useimmiten paperikoneella tehdyille painotuotteille. Riittävän alhainen opasiteetti saavutetaan myös valmistamalla standardin mukainen matalaneliömassainen arkki viiralle, mutta tämä johtaa kuitumaisten hienoaineiden, mineraalisten täyteaineiden ja painomusteiden alhaiseen retentioon. Matala retentio on erityisen haitallinen piirre mustemittauksen kannalta massoilla, jotka sisältävät huomattavia määriä painomusteita. Siten usein valmistetaan läpikuultamattomia arkkeja suodatinpaperin päälle, joiden retentio on korkea. Korkeasta opasiteetista johtuen näistä arkeista ei voida määrittää valonsirontakerrointa, jolloin mustepitoisuuden määritys perustuu vakiokertoimeen. Tämän väitöskirjan tavoitteena oli selvittää retention ja hienoaineiden muutoksien vaikutuksia valonsirontakertoimeen ja mustemittaustulokseen. Tutkimuksen tulokset osoittivat että valonsirontakerroin, joka mitataan mustepitoisuuden yhteydessä, ei pysy vakiona hienoainepitoisuuden muuttuessa. Hienoainepitoisuuteen ja siten valonsirontakertoimeen vaikuttavat keräyspaperin laji, hyperpesu ja vaahdotus. Myös painomuste vaikuttaa valonsirontakertoimeen, mutta käytännössä vaikutuksen suurusluokka on pienempi kuin hieno- ja täyteaineilla. Mustepitoisuuden määrityksessä käytetyn valonsirontakertoimen on oltava edustava, muutoin arvot voivat olla systemaattisesti virheellisiä hienoainemäärän tai laadun muuttuessa. Virheen välttämiseksi olisi suositeltavaa määrittää valonsirontakerroin mustepitoisuusanalyysin yhteydessä. Tämä olisi mahdollista tehdä suodatinpaperin päälle valmistetusta matalaneliömassaisesta arkista, jolloin saavutetaan korkea retentio ja näin mitattu arvo edustaa paremmin massasuspension alkuperäistä tilaa.

Abstract The aim of the deinking process is to produce deinked pulp from recovered papers (RCPs) with sufficient brightness and cleanliness to fulfil the quality requirements set by the paper grade to be produced. Due to the excessive production costs and material losses of modern deinking processes, there is a need to simplify deinking lines. A prerequisite for this action is that ink content bound to fibres, dirt content and ink fragmentation are minimised in the pulping stage. Thus, it is important to recognise the factors affecting ink behaviour in pulping, to search for new ways to improve ink detachment from RCPs in pulping and to search pulping methods that could efficiently process RCPs printed with various inks. The aim of this thesis was to obtain new information on how the environmental conditions that prevail during the storage and transportation of RCPs affect ink behaviour in subsequent pulping and to find out whether there is further potential to decrease ink content bound to fibres, not only by treating recovered papers chemically before the actual pulping process, but also by removing the detached ink particles during the pulping process. The results show that if some RCPs are very moist and exposed to high temperatures for a reasonable time before the pulping process, the problems in releasing ink from the fibres in pulping become more pronounced and the pulp is dirtier compared to pulp from RCPs that are thermally aged but dry. Properly wetting some RCPs with conventional alkaline deinking chemicals in suitable conditions ahead of the pulping process reduces the ink content that remains bound to the fibres after the pulping process. The efficiency of the pre-wetting treatment in aiding ink detachment from fibres in subsequent pulping is highly dependent on the alkalinity, temperature and duration of the treatment. Semi-continuous ink removal during the pulping process offers the possibility to continue defibering, ink detachment from fibres and dirt fragmentation in pulping without fear of ink redeposition into or onto the fibres, thus resulting in fully disintegrated pulp with lower ink content bound to fibres than in conventional pulping. This enables efficiently simultaneous processing of, for example, papers printed with water-based inks and toners. / Tiivistelmä Siistausprosessin tavoitteena on tuottaa keräyspapereista valmistettua vaaleaa ja puhdasta massaa, jota voidaan käyttää uusien paperituotteiden valmistamiseen. Siistausprosesseja pyritään yksinkertaistamaan nykyisten monimutkaisten prosessien korkeiden tuotantokustannusten ja materiaalitappioiden vuoksi. Eräs edellytys siistausprosessien yksinkertaistamiselle on, että kuiduissa kiinni olevan musteen pitoisuus, massan likapitoisuus ja musteen liiallinen pilkkoutuminen minimoidaan siistausprosessin ensimmäisessä vaiheessa, pulpperoinnissa. Täten on tärkeää tunnistaa musteen käyttäytymiseen pulpperoinnissa vaikuttavat tekijät, etsiä uusia mahdollisuuksia parantaa musteen irrotusta keräyspapereista sekä kehittää pulpperointimenetelmiä, joilla voitaisiin prosessoida tehokkaasti eri painomenetelmillä painettuja papereita. Tämän työn tavoitteena oli saada uutta tietoa siitä miten ympäristöolosuhteet, joille keräyspaperit voivat altistua varastoinnin ja kuljetuksen aikana, vaikuttavat musteen käyttäytymiseen pulpperoinnissa. Lisäksi tavoitteena oli selvittää voitaisiinko kuituihin kiinni jääneen musteen pitoisuutta vähentää esiliottamalla keräyspapereita sopivissa kemiallisissa olosuhteissa ennen pulpperointia ja poistamalla irronneet mustepartikkelit massan seasta pulpperoinnin aikana. Tulokset osoittavat, että jos tietyt keräyspaperit ovat erittäin kosteita ja altistuvat korkealle lämpötilalle riittävän pitkän ajan ennen pulpperointia, tulee musteen irrottaminen kuiduista pulpperoinnissa vaikeammaksi ja tuotettu massa likaisemmaksi, kuin sellaisista keräyspapereista, jotka ovat altistuneet kuivina korkealle lämpötilalle. Kuituihin kiinnittyneen musteen pitoisuutta voidaan vähentää esiliottamalla tiettyjä keräyspapereita alkalisilla siistauskemikaaleilla sopivissa olosuhteissa ennen pulpperointia. Esiliotuksen kyky parantaa musteen irrotusta kuiduista pulpperoinnissa riippuu voimakkaasti esiliotusvaiheen alkalisuudesta, lämpötilasta ja kestosta. Kun irronneet mikroskooppiset mustepartikkelit poistetaan massasta useassa vaiheessa pulpperoinnin aikana, voidaan paperin kuidutusta, musteen irrottamista kuiduista ja likapilkkujen hajottamista jatkaa ilman että haitallista musteen takaisin kiinnittymistä kuituihin tapahtuu. Tämä mahdollistaa esimerkiksi vesipohjaisten musteiden ja lasertulosteiden samanaikaisen prosessoinnin.

En una tesi anterior (Puig, 2004) es varen estudiar els aspectes mecànics vinculats al desfibratge i als consums energètics associats al procés de desintegració per acabar quantificant les forces implicades en el procés d'individualització dels components de diferents paperots. Aquest estudi, ha permès conèixer les condicions de desintegració que condueixen a un mínim consum energètic, aspecte complementari al reciclatge i destintatge del paperot però molt important per aconseguir un procés realment sostenible.Degut als requeriments del mercat, hi ha un altre aspecte o vessant realment important com és l'eliminació de tinta. Aquest procés, malgrat la complexitat industrial, es pot reduir o simplificar en dues etapes: la desintegració i la flotació. Ambdues, per raons d'eficàcia i condicionades pels agents químics que s'utilitzen, es realitzen en medi fortament alcalí (entorn d'un pH a 12). Aquest fet, genera una forta contaminació (DQO elevada) i per tant, és un procés poc respectuós amb el medi ambient.Els factors que condicionen treballar en medi alcalí són principalment, el despreniment de la tinta del suport, clarament accelerat en medi bàsic i fonamental per un bon destintatge i la utilització de tensioactius aniònics. Aquests tensioactius són sensibles al pH i la seva eficàcia disminueix en medi neutre o quasi neutre.Atès el que s'ha exposat, s'ha plantejat aquesta tesi que porta per títol "Aspectes Físics i Químics del Destintatge de Paper Revista mitjançant Tensioactius Catiònics", com un estudi del procés de destintatge de paper revista recuperat parant especial atenció a les variables físico-químiques i mecàniques del procés i a la seva influència en el despreniment i fragmentació de la tinta, així com en el procés d'eliminació de la tinta per flotació per tal d'avaluar la viabilitat d'un procés de destintatge en medi neutre enfront del destintatge alcalí convencional. S'ha utilitzat, com a paperot a destintar, el paper revista ja que aquest tipus de paper representa un percentatge elevat del paper recuperat a la Unió Europea. A més, aquest tipus de paper és utilitzat habitualment en les plantes de destintatge industrials per millorar les propietats de les suspensions destintades de paper de diari.La utilització de tensioactius catiònics és deguda a que la seva activitat no es veu afectada pel pH de la suspensió. Així, durant la comparació dels processos de destintatge en medi neutre i en medi alcalí, les eficàcies dels processos no es veuran influenciades pel grau d'ionització del tensioactiu.Donada l'absència d'estudis sobre la influència de les variables del procés en les mesures de concentració efectiva de tinta residual (ERIC) i ja que s'ha emprat aquest paràmetre per avaluar el despreniment i fragmentació de la tinta durant l'etapa de desintegració. En primer lloc, s'ha plantejat un estudi fonamental de la influència que poden tenir les variables del procés (granulometria, concentració de tinta i tipus de suport) en aquest paràmetre. Pel que fa a l'etapa de flotació, s'estudiarà l'efectivitat d'aquesta etapa, posant especial atenció a la capacitat del tensioactiu per eliminar tota la tinta despresa en l'etapa de desintegració. A més, donada la poca informació bibliogràfica referida als mecanismes de flotació amb tensioactius catiònics i la influència que té l'adsorció d'aquests agents per part de la suspensió paperera en l'etapa de flotació, s'ha dut a terme un estudi de l'adsorció dels tensioactius catiònics per part dels components d'una suspensió paperera.Per tant, la tesi realitzada té com a objectius: Estudi fonamental de les mesures de ERIC (concentració efectiva de tinta residual) amb suports específics. Estudi de la desintegració en medi neutre i comparació amb la desintegració clàssica. Modelització del desfibratge de paperot a l'etapa de desintegració. Estudi de l'eliminació de tinta per flotació en medi neutre i comparació amb la flotació clàssica. Estudi del mecanisme d'adsorció de tensioactius en suspensions de cel·lulosa sintètica i de paperot. / A previous thesis (Puig, 2004) have studied the mechanical aspects related to defibering and to energetic consumptions related to the disintegration process to end up quantifying the forces involved in the process of individualization of the different components of recovered papers. This study has permitted to know the disintegration conditions that lead to a minimum energetic consumption which is a complementary aspect to the recycling and deinking of waste paper but very important to get a really sustainable process.Due to the requests of the market, there is another really important aspect in the wastepaper recycling process which is the elimination of ink. Ink elimination, can be summarized in two unit operations: Disintegration and flotation. Both unit operations are strongly conditioned by the chemical agents used. Usually disintegration is carried out in a highly alkaline medium (pH 12). This fact, cause a high contamination in process waters (high COD) and therefore, the process is not environmentally friendly. The factors that condition the high alkaline medium are mainly ink detachment from the cellulosic support which is clearly accelerated by the alkaline medium, and the utilization of anionic surfactants. These surfactants are sensitive to the pH and its efficiency diminishes in neutral or almost neutral medium. So it has been proposed this thesis entitled "Aspectes Físics i Químics del Destintatge de Paper Revista mitjançant Tensioactius Catiònics" (Physico-chemical aspects of deinking of OMG using cationic surfactants) as a study of the viability of neutral deinking versus alkaline deinking.OMG has been used since this grade represents a high percentage of paper recovered in the European Union. Besides, this grade is used in industrial deinking plants to improve deinked ONP properties.Cationic surfactants are used because its properties are not affected by the pH of the suspension. So during the comparison of deinking processes in neutral and alkaline medium, the process efficiency will not be influenced by the surfactant ionization degree.OMG deinking study begins with a modelization of disintegration followed by an analysis of ink detachment and fragmentation achieved in neutral conditions and comparing them with the results obtained in alkaline conditions.Due to the absence of studies on the influence of the variables of the process in the measurements of effective residual ink concentration (ERIC) and since this parameter has been used to evaluate the detachment and fragmentation of ink during disintegration itself, it has been done a fundamental study of the influence of process variables such as ink particles size, ink concentration and type of the cellulosic support on this parameter.Regarding flotation stage, the effectiveness of this process will be studied focusing on the capability of the surfactant to eliminate all the ink detached during disintegration. Since deinking process is strongly influenced by surfactant adsorption on the different components of wastepaper suspensions and that there is a little information related to flotation mechanisms when cationic surfactants are used it has been accomplished a study of the adsorption of cationic surfactants by the components of a wastepaper suspension (cellulosic support and ink) and the results have been compared with the adsorption of an anionic surfactant in the same conditions.Therefore, the thesis has the following objectives: Fundamental study of ERIC measurements with specific supports. Study of neutral disintegration in comparison of traditional alkaline disintegration. Modelization of paper defibering during disintegration process. Study of ink elimination by means of a flotation process in neutral medium in comparison with a traditional alkaline flotation process. Study of the adsorption mechanism of surfactants by a wastepaper suspension.

La tesi realitza un estudi detallat dels principals processos que tenen lloc durant l'eliminació de tinta tòner per flotació.L'estudi del procés d'adhesió de tinta a la superfície de bombolles d'aire s'ha realitzat mitjançant visió artificial. Els resultats obtinguts han mostrat que un excés de tensioactiu provoca una disminució de la quantitat de tinta unida a la bombolla d'aire i per tant una disminució de l'eficàcia del procés de flotació. La caracterització de les bombolles d'aire presents en una cel·la de flotació ha posat de manifest que tant el cabal d'aire com la velocitat de l'agitador configuren la distribució de diàmetres final. L'estudi del procés d'eliminació de tinta per flotació en absència de fibres cel·lulòsiques ha mostrat que les variables físico-químiques estudiades són les que tenen una major influència en el procés d'eliminació de tinta tòner per flotació.Finalment s'han addicionat fibres cel·lulòsiques a la suspensió. S'ha pogut comprovar que s'aconsegueix una bona eliminació de tinta sempre i quan les condicions hidrodinàmiques siguin les adequades. / First of all the adhesion of ink particles to air bubbles surface was studied by means of artificial vision. Results obtained showed that an excess of surfactant decreases ink adsorption decreasing flotation efficiency. Air bubbles created in a lab-scale flotation cell were characterized by means of artificial vision. Results showed that air flow and agitation rate configure the final air bubble distribution.Ink removal from a flotation cell was studied without the presence of cellulose fibers. Results obtained showed that the physico-chemical variables studied had a major influence on ink removal than hydrodynamic variables studied.Finally, cellulose fibers were added to the suspension. Results obtained showed that it was possible to obtain good flotation results provided that the hydrodynamic conditions were carefully adjusted.