Biomass Gasification - Process analysis and dimensioning aspects for downdraft units and gas cleaning lines

In such territories where food production is mostly scattered in several small / medium size or even domestic farms, a lot of heterogeneous residues are produced yearly, since farmers usually carry out different activities in their properties. The amount and composition of farm residues, therefore, widely change during year, according to the single production process periodically achieved. Coupling high efficiency micro-cogeneration energy units with easy handling biomass conversion equipments, suitable to treat different materials, would provide many important advantages to the farmers and to the community as well, so that the increase in feedstock flexibility of gasification units is nowadays seen as a further paramount step towards their wide spreading in rural areas and as a real necessity for their utilization at small scale. Two main research topics were thought to be of main concern at this purpose, and they were therefore discussed in this work: the investigation of fuels properties impact on gasification process development and the technical feasibility of small scale gasification units integration with cogeneration systems. According to these two main aspects, the present work was thus divided in two main parts. The first one is focused on the biomass gasification process, that was investigated in its theoretical aspects and then analytically modelled in order to simulate thermo-chemical conversion of different biomass fuels, such as wood (park waste wood and softwood), wheat straw, sewage sludge and refuse derived fuels. The main idea is to correlate the results of reactor design procedures with the physical properties of biomasses and the corresponding working conditions of gasifiers (temperature profile, above all), in order to point out the main differences which prevent the use of the same conversion unit for different materials. At this scope, a gasification kinetic free model was initially developed in Excel sheets, considering different values of air to biomass ratio and the downdraft gasification technology as particular examined application. The differences in syngas production and working conditions (process temperatures, above all) among the considered fuels were tried to be connected to some biomass properties, such elementary composition, ash and water contents. The novelty of this analytical approach was the use of kinetic constants ratio in order to determine oxygen distribution among the different oxidation reactions (regarding volatile matter only) while equilibrium of water gas shift reaction was considered in gasification zone, by which the energy and mass balances involved in the process algorithm were linked together, as well. Moreover, the main advantage of this analytical tool is the easiness by which the input data corresponding to the particular biomass materials can be inserted into the model, so that a rapid evaluation on their own thermo-chemical conversion properties is possible to be obtained, mainly based on their chemical composition A good conformity of the model results with the other literature and experimental data was detected for almost all the considered materials (except for refuse derived fuels, because of their unfitting chemical composition with the model assumptions). Successively, a dimensioning procedure for open core downdraft gasifiers was set up, by the analysis on the fundamental thermo-physical and thermo-chemical mechanisms which are supposed to regulate the main solid conversion steps involved in the gasification process. Gasification units were schematically subdivided in four reaction zones, respectively corresponding to biomass heating, solids drying, pyrolysis and char gasification processes, and the time required for the full development of each of these steps was correlated to the kinetics rates (for pyrolysis and char gasification processes only) and to the heat and mass transfer phenomena from gas to solid phase. On the basis of this analysis and according to the kinetic free model results and biomass physical properties (particles size, above all) it was achieved that for all the considered materials char gasification step is kinetically limited and therefore temperature is the main working parameter controlling this step. Solids drying is mainly regulated by heat transfer from bulk gas to the inner layers of particles and the corresponding time especially depends on particle size. Biomass heating is almost totally achieved by the radiative heat transfer from the hot walls of reactor to the bed of material. For pyrolysis, instead, working temperature, particles size and the same nature of biomass (through its own pyrolysis heat) have all comparable weights on the process development, so that the corresponding time can be differently depending on one of these factors according to the particular fuel is gasified and the particular conditions are established inside the gasifier. The same analysis also led to the estimation of reaction zone volumes for each biomass fuel, so as a comparison among the dimensions of the differently fed gasification units was finally accomplished. Each biomass material showed a different volumes distribution, so that any dimensioned gasification unit does not seem to be suitable for more than one biomass species. Nevertheless, since reactors diameters were found out quite similar for all the examined materials, it could be envisaged to design a single units for all of them by adopting the largest diameter and by combining together the maximum heights of each reaction zone, as they were calculated for the different biomasses. A total height of gasifier as around 2400mm would be obtained in this case. Besides, by arranging air injecting nozzles at different levels along the reactor, gasification zone could be properly set up according to the particular material is in turn gasified. Finally, since gasification and pyrolysis times were found to considerably change according to even short temperature variations, it could be also envisaged to regulate air feeding rate for each gasified material (which process temperatures depend on), so as the available reactor volumes would be suitable for the complete development of solid conversion in each case, without even changing fluid dynamics behaviour of the unit as well as air/biomass ratio in noticeable measure. The second part of this work dealt with the gas cleaning systems to be adopted downstream the gasifiers in order to run high efficiency CHP units (i.e. internal engines and micro-turbines). Especially in the case multi–fuel gasifiers are assumed to be used, weightier gas cleaning lines need to be envisaged in order to reach the standard gas quality degree required to fuel cogeneration units. Indeed, as the more heterogeneous feed to the gasification unit, several contaminant species can simultaneously be present in the exit gas stream and, as a consequence, suitable gas cleaning systems have to be designed. In this work, an overall study on gas cleaning lines assessment is carried out. Differently from the other research efforts carried out in the same field, the main scope is to define general arrangements for gas cleaning lines suitable to remove several contaminants from the gas stream, independently on the feedstock material and the energy plant size The gas contaminant species taken into account in this analysis were: particulate, tars, sulphur (in H2S form), alkali metals, nitrogen (in NH3 form) and acid gases (in HCl form). For each of these species, alternative cleaning devices were designed according to three different plant sizes, respectively corresponding with 8Nm3/h, 125Nm3/h and 350Nm3/h gas flows. Their performances were examined on the basis of their optimal working conditions (efficiency, temperature and pressure drops, above all) and their own consumption of energy and materials. Successively, the designed units were combined together in different overall gas cleaning line arrangements, paths, by following some technical constraints which were mainly determined from the same performance analysis on the cleaning units and from the presumable synergic effects by contaminants on the right working of some of them (filters clogging, catalysts deactivation, etc.). One of the main issues to be stated in paths design accomplishment was the tars removal from the gas stream, preventing filters plugging and/or line pipes clogging At this scope, a catalytic tars cracking unit was envisaged as the only solution to be adopted, and, therefore, a catalytic material which is able to work at relatively low temperatures was chosen. Nevertheless, a rapid drop in tars cracking efficiency was also estimated for this same material, so that an high frequency of catalysts regeneration and a consequent relevant air consumption for this operation were calculated in all of the cases. Other difficulties had to be overcome in the abatement of alkali metals, which condense at temperatures lower than tars, but they also need to be removed in the first sections of gas cleaning line in order to avoid corrosion of materials. In this case a dry scrubber technology was envisaged, by using the same fine particles filter units and by choosing for them corrosion resistant materials, like ceramic ones. Besides these two solutions which seem to be unavoidable in gas cleaning line design, high temperature gas cleaning lines were not possible to be achieved for the two larger plant sizes, as well. Indeed, as the use of temperature control devices was precluded in the adopted design procedure, ammonia partial oxidation units (as the only considered methods for the abatement of ammonia at high temperature) were not suitable for the large scale units, because of the high increase of reactors temperature by the exothermic reactions involved in the process. In spite of these limitations, yet, overall arrangements for each considered plant size were finally designed, so that the possibility to clean the gas up to the required standard degree was technically demonstrated, even in the case several contaminants are simultaneously present in the gas stream. Moreover, all the possible paths defined for the different plant sizes were compared each others on the basis of some defined operational parameters, among which total pressure drops, total energy losses, number of units and secondary materials consumption. On the basis of this analysis, dry gas cleaning methods proved preferable to the ones including water scrubber technology in al of the cases, especially because of the high water consumption provided by water scrubber units in ammonia adsorption process. This result is yet connected to the possibility to use activated carbon units for ammonia removal and Nahcolite adsorber for chloride acid. The very high efficiency of this latter material is also remarkable. Finally, as an estimation of the overall energy loss pertaining the gas cleaning process, the total enthalpy losses estimated for the three plant sizes were compared with the respective gas streams energy contents, these latter obtained on the basis of low heating value of gas only. This overall study on gas cleaning systems is thus proposed as an analytical tool by which different gas cleaning line configurations can be evaluated, according to the particular practical application they are adopted for and the size of cogeneration unit they are connected to.

Application of ionic liquids and enzymes for the removal of proteinaceous layers from polychrome of works of art and evaluation of the cleaning effectiveness

Dissertação Apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Ciências da Conservação, especialização em Pintura

CFD modeling of dispersion water feed in wastewater cleaning application

Fluid particle breakup and coalescence are important phenomena in a number of industrial flow systems. This study deals with a gas-liquid bubbly flow in one wastewater cleaning application. Three-dimensional geometric model of a dispersion water system was created in ANSYS CFD meshing software. Then, numerical study of the system was carried out by means of unsteady simulations performed in ANSYS FLUENT CFD software. Single-phase water flow case was setup to calculate the entire flow field using the RNG k-epsilon turbulence model based on the Reynolds-averaged Navier-Stokes (RANS) equations. Bubbly flow case was based on a computational fluid dynamics - population balance model (CFD-PBM) coupled approach. Bubble breakup and coalescence were considered to determine the evolution of the bubble size distribution. Obtained results are considered as steps toward optimization of the cleaning process and will be analyzed in order to make the process more efficient.

Ambiente data cleaning: suporte extensível, semântico e automático para análise e transformação de dados

Pós-graduação em Ciência da Computação - IBILCE

Cleaning Conveyor Belts in the Chicken-Cutting Area of a Poultry Processing Plant with 45 degrees C Water

Conveyor belts are widely used in food handling areas, especially in poultry processing plants. Because they are in direct contact with food and it is a requirement of the Brazilian health authority, conveyor belts are required to be continuously cleaned with hot water under pressure. The use of water in this procedure has been questioned based on the hypothesis that water may further disseminate microorganisms but not effectively reduce the organic material on the surface. Moreover, reducing the use of water in processing may contribute to a reduction in costs and emission of effluents. However, no consistent evidence in support of removing water during conveyor belt cleaning has been reported. Therefore, the objective of the present study was to compare the bacterial counts on conveyor belts that were or were not continuously cleaned with hot water under pressure. Superficial samples from conveyor belts (cleaned or not cleaned) were collected at three different times during operation (T1, after the preoperational cleaning [5 a.m.]; T2, after the first work shift [4 p.m.]; and T3, after the second work shift [1:30 a.m.]) in a poultry meat processing facility, and the samples were subjected to mesophilic and enterobacterial counts. For Enterobacteriaceae, no significant differences were observed between the conveyor belts, independent of the time of sampling or the cleaning process. No significant differences were observed between the counts of mesophilic bacteria at the distinct times of sampling on the conveyor belt that had not been subjected to continuous cleaning with water at 45 degrees C. When comparing similar periods of sampling, no significant differences were observed between the mesophilic counts obtained from the conveyor belts that were or were not subjected to continuous cleaning with water at 45 degrees C. Continuous cleaning with water did not significantly reduce microorganism counts, suggesting the possibility of discarding this procedure in chicken processing.

HTHP syngas cleaning concept of two stage biomass gasification for FT synthesis

The EU intends to increase the fraction of fuels from biogenic energy sources from 2% in 2005 to 8% in 2020. This means a minimum of 30 million TOE/a of fuels from biomass. This makes technical-scale generation of syngas from high-grade biomass, e.g. straw, hay, bark, or paper/cardboard waste, and the production of synthetic fuels by Fischer-Tropsch (FT) synthesis highly attractive. The BTL concept (Biomass to Liquids) of the Karlsruhe Research Center, labeled bioliq, focuses on this challenge by locally concentrating the biomass energy content by fast pyrolysis in a coke/oil slurry followed by slurry conversion to syngas in a central entrained flow gasifier at 1200C and pressures above 4MPa. FT synthesis generates intermediate products for synthetic fuels. To prevent the sensitive catalysts from being poisoned the syngas must be free of tar and particulates. Trace concentrations of H2S, COS, CS2, HCl, NH3, and HCN must be on the order of a few ppb. Moreover, maximum conversion efficiency will be achieved by cleaning the gas above the synthesis conditions. (T>350C, P>4MPa). The concept of an innovative dry HTHP syngas cleaning process is presented. Based on HT particle filtration and suitable sorption and catalysis processes for the relevant contaminants, an overall concept will be derived, which leads to a syngas quality required for FT synthesis in only two combined stages. Results of filtration experiments on a pilot scale are presented. The influence of temperature on the separation and conversion, respectively, of particulates and gaseous contaminants is discussed on the basis of experimental results obtained on a laboratory and pilot scale. Extensive studies of this concept are performed in a scientific network comprising the Karlsruhe Research Center and five universities; funding is provided by the Helmholtz Association of National Research Centers in Germany.

Caracterização de dois equipamentos de beneficiamento e classificação de tomates para mesa

On the last years, in Brazil, sorting and classifying fruits and vegetables using packing lines have increased. This work aimed at characterizing the cleaning process for fresh market tomatoes at two packing lines, one imported and one national located at Campinas, São Paulo State. Characterization included data, number, types and brushes velocity, water use, fruit standing time and cleaning efficiency. Standing time was measured correlating to fruit diameter (CEAGESP). For measuring cleaning efficiency an equipment was developed that was mainly composed of a ring involved with white cloth. Samples were taken before and after the cleaning step and evaluated using a colorimeter HUNTER Lab. The results showed a strong difference between the two equipments. The imported equipment showed lower number on brushes and rotation than national one, however a higher water consumption. For imported equipments this relation was not found. Both packing lines showed the same cleaning efficiency. Cleaning efficiency is related to be an interaction among the studies parameters, and it could be necessary a better management than the one used on both equipments.

Otimização da eficiência de limpeza em equipamento de beneficiamento de tomate de mesa

The post-harvesting cleaning process in fresh market tomatoes production is essential to the consumer acceptance, since the degree of dirtiness of the fruits is directly related to its quality. However, the washing stage of the cleaning process of commercial packinghouse demands an excessive water volume, bringing serious environmental concerns. The objective of this work was to compare the cleaning efficiency in two cleaning systems through the evaluation of different operational conditions of the cleaning process, related with the brush rotation, water flow and fruit standing time under the system. It was compared the conventional system utilized in commercial equipment with a system using commercial sprays. The results showed that the cleaning efficiency was not directly related to the water volume used, but to the water pressure, standing time and brushes rotation. Therefore, the use of commercial sprays can bring benefits to the cleaning efficiency, increasing it up to 13%, and to the environmental, decreasing water consumption.

Removal of selected metals from drinking water using modified powdered block carbon

This paper presents the possible alternative removal options for the development of safe drinking water supply in the trace elements affected areas. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causes various adverse effects on living bodies. Performance of three filter bed method was evaluated in the laboratory. Experiments have been conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe/Fe(3)C (iron/iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon (PBC), powder carbon steel and ball ceramic in the ion-sorption columns as a cleaning process. The PBC modified is a satisfactory and practical sorbent for trace elements (arsenite and chromate) dissolved in water.

Three filter beds for arsenite and chromate removal

Arsenic (As) and chromium (Cr) are two of the most toxic pollutants introduced into natural waters from a variety of sources, and they cause various adverse effects on living bodies when their concentrations exceed permissible limits. Laboratory experiments have been conducted to investigate the sorption of As and Cr on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of As and Cr species for iron/iron carbide (Fe/Fe3C) sites is the key factor in controlling the removal of the elements. The method is based on the use of powder carbon steel, powdered block carbon, and ball ceramic in the ion-sorption columns as a cleaning process. The presence of carbon steel in a system that contains As3+ and Cr6+ might have a potential effect.

Trace elements removal from water using modified activated carbon

This paper present the possible alternative options for the remove of trace elements from drinking water supplies in the trace. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causing various adverse effects on living bodies. The performance of three filter bed methods was evaluated in the laboratory. Experiments were conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe / Fe3C (iron / iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon, powder carbon steel and ceramic spheres in the ion-sorption columns as a cleaning process. The modified powdered block carbon is a satisfactory and economical sorbent for trace elements (arsenite and chromate) dissolved in water due to its low unit cost of about $23 and compatibility with the traditional household filtration system.

Kaasutuskaasun puhdistus

Tässä diplomityössä on selvitetty hiilestä, jätteestä tai biopolttoaineesta kaasutetun kaasun märkä- ja kuivapuhdistusta. Kaasutuskaasun puhdistuksella voidaan likainen ja jopa ongelmallinen aines muuttaa tai puhdistaa sellaiseksi ympäristökelpoiseksi polttoaineeksi, että sitä voidaan käyttää nykyisissä kulutuskohteissa ongelmitta. Lisäkannustusta kaasutuskaasun puhdistus saa uusista EU-direktiiveistä, jotka tulevat rajoittamaan jätteiden läjittämistä kaatopaikoille. Loppusijoitukseen meneviä jätevirtoja voidaan energiakäytöllä pienentää huomattavasti.Työ on tehty PVO-Engineering Oy:n voimalaitostekniikan osastolle kevään 2001 aikana. Työn tavoitteena oli kasvattaa yrityksen tietomäärää kaasutuskaasun puhdistuksen osalta. Lisäksi pyrittiin selvittämään uuden keraamisen pussisuodatinmateriaalin käyttöä kaasutuskaasun kuumakuivasuodatuksessa. Työn ensimmäisessä osassa esitetään kaasutuskaasun koostumuksen ja syntymisen lisäksi tämän työn lähtökohdat ja tavoitteet. Toisessa osassa selvitetään kaasulle asetettavia vaatimuksia eri käyttötapojen mukaan. Kolmannessa ja neljännessä osassa selvitetään puhdistettavien komponenttien käyttäytymistä ja sopivia puhdistusmenetelmiä.Kaasutuskaasun puhdistustekniikka vaihtelee paljonkin riippuen kaasun käyttökohteesta. Eroja syntyy käyttökohteen asetettamista vaatimuksista polttoaineelle, kaasutettavan polttoaineen koostumuksesta ja laadun vaihtelusta. Puhdistuksessa keskitytään kloori -, rikki -, typpi - ja metalliyhdisteiden poistamiseen kaasuvirrasta. Erotuskyvyllä arvioituna eri puhdistusmenetelmistä tehokkaimpia ovat pesurisähkösuodatinyhdistelmät. Niiden suuret jätemäärät ovat kuitenkin iso ongelma. Kuumakuivapuhdistuksessa pyritään kehittämään menetelmä, jossa syntyvät jätemäärät ovat pieniä ja puhdistustulos on riittävä. Puhdistuksen apukeinona käytetään usein erilaisia katalyyttejä. Tunnetuimpia ovat erilaiset kalsiumpohjaiset materiaalit ja mineraalit. Katalyyteillä voidaan tehostaa tarpeellisia kemiallisia reaktioita puhdistusprosessissa. Kaikki puhdistukseen liittyvät ongelmat ovat kooltaan niin suuria, että niiden ratkaisemiseksi on tulevaisuudessa tehtävä lujasti töitä. Markkinanäkymät toimivalle puhdistustekniikalle ovat nykymaailmassa hyvät. Niinpä tuotekehitykseen laitetut panokset voivat tulevaisuudessa olla yritykselle kullan arvoisia.

Kaatopaikkakaasun hyväksikäyttö lietteen kuivauksessa

Tällä hetkellä suuri osa esikäsiteltyjen jätevesilietteiden loppusijoitusvaihtoehdoista ei pysty kattamaan lopullisesti kasvavien lietemäärien loppusijoitustarvetta, mikä lisää lietteen loppusijoitusta kaatopaikoille. Kuitenkin EU:n tiukentuneen jätehuoltolainsäädännön sekä ilmastonlämpenemisen suurien haasteiden vuoksi, kaatopaikoille sijoitettavien jätteiden määrää täytyy pyrkiä vähentämään. Tämän työn tavoitteena on tutkia jätevedenpuhdistamoilta tulevan lietteen termistä kuivausta yhtenä lietteenkäsittely vaihtoehtona. Tavoitteena on selvittää voidaanko lietettä kuivaamalla saada liete paremmin hyödynnetyksi. Työssä tarkasteltiin yleisesti yhdyskuntalietteen termisessä kuivaamisessa nykyisin käytettäviä menetelmiä, sen ympäristövaikutuksia, energian tarvetta ja kustannuksia sekä siitä saatavaa hyötyä lietteen loppusijoittamisessa. Lisäksi arvioitiin kuinka kaatopaikkakaasun hyödyntäminen soveltuisi lietteen kuivauksessa tarvittavan energian tuotantoon. Työssä tehdyn selvityksen mukaan kaatopaikkakaasua voidaan hyödyntää suhteellisen helposti lämmöntuotannossa ilman merkittäviä laitosmuutoksia tai kaasun puhdistusta. Ongelmana pidettiin kaatopaikkakaasun kuljetuksia, joka on suhteellisen vaikeaa ja taloudellisesti kannattamatonta. Kuitenkin noin 10 km välimatkan säteellä kaatopaikasta sen hyödyntäminen olisi mahdollista. Työn laskelmien mukaan Suomessa hukkaan poltetulla kaatopaikkakaasulla voitaisiin kuivata noin 250 tuhatta tonnia lietettä vuosittain.

Puuperäisten biomassahydrolysaattien likaamien membraanien pesu

Tässä diplomityössä tutkittiin biomassahydrolysaatilla liattujen ultrasuodatusmembraanien pesua. Työn kirjallisuusosassa käsitellään membraanien likaantumista ja pesua, puuperäistä biomassahydrolysaattia sekä biomassahydrolysaatin suodatusta membraaneilla ja membraanien karakterisointia. Kokeellisessa osassa tutkittiin pesuaineiden vaikutusta koivuhydrolysaatilla liattujen membraanien peseytyvyyteen. Käytetyt ultrasuodatusmembraanit olivat Alfa Lavalin UFX5 ja ETNA01PP. Membraanien pesussa käytettiin Ecolabin entsymaattisia P3-ultrasil 53 ja P3-ultrasil 67 pesuaineita yhdessä emäksisen P3-ultrasil 69 pesuaineen kanssa sekä hapanta P3-ultrasil 75 pesuainetta. Lisäksi emäksisiä P3-ultrasil 110, P3-ultrasil 112 ja P3-ultrasil 115 pesuaineita. Emäksisten pesujen tehokkuutta vertailtiin pelkällä natriumhydroksidilla tehtyyn pesuun. Membraanien likaantumista arvioitiin mittaamalla puhtaan veden vuota ennen ja jälkeen likaantumissuodatuksen ja laskemalla niiden vuoarvojen erotus. Samalla tavalla arvioitiin pesuaineiden vaikutusta membraanin peseytyvyyteen. Lisäksi peseytyvyyttä arvioitiin FTIR–analyyseillä, kontaktikulmamittauksilla ja membraanin sisältämän ligniinin värjäyksellä. Tutkimuksissa havaittiin, että koivuhydrolysaatilla liatuille UFX5 membraaneille vesivuon sekä FTIR–spektrin muuttumisen perusteella sopii parhaiten emäksisen ja happaman pesuaineen kaksivaiheinen pesu. Kontaktikulman palautumisen perusteella parhaiten sopi pelkällä emäksisellä P3-Ultrasil 115 tehty pesu. Ligniiniä parhaiten, mikroskooppiin liitetyllä kameralla otettujen kuvien perusteella, poisti entsymaattinen P3-ultrasil 67, mutta tämä samalla modifioi membraanin pintaa. Tässä tutkimuksessa havaittiin, että emäksinen ja entsymaattinen pesuaine pesevät melko hyvin koivuhydrolysaatilla liattuja membraaneja. Lisäksi havaittiin, että ligniini tunkeutuu suodatuksissa membraanin sisään, joten pelkkä pesuaineen kierrättäminen laitteistossa ei riitä vaan tarvitaan paineellista pesua.

Adhesion and production of degrading enzymes by bacteria isolated from biofilms in raw milk cooling tanks

Biofilms in milk cooling tanks compromise product quality even on farms. Due to the lack of studies of this topic, this study evaluated the microbiological conditions of raw milk cooling tanks on farms and characterized the microorganisms isolated from these tanks. Samples were wiped off with sterile swabs from seven milk cooling tanks in three different points in each tank. Mesophiles and psychrotrophic counts were performed in all samples. The isolation of Pseudomonas spp., Bacillus cereus and atypical colonies formed on selective media were also performed, totalizing 297 isolates. All isolates were tested for protease and lipase production and biofilm formation. Of the total isolates, 62.9% produced protease, 55.9% produced lipase, and 50.2% produced biofilm. The most widespread genus inside the milk cooling tank was Pseudomonas since it was not possible to associate this contamination with a single sampling point in the equipment. High counts of microorganisms were found in some cooling tanks, indicating poor cleaning of the equipment and providing strong evidences of microbial biofilm presence. Moreover, it is worth mentioning the milk potential contamination with both microbial cells and their degrading enzymes, which compromises milk quality.