X-ray difraction analysis of desulfurant sorbents prepared by mixing calcined sewage sludge and CaO in distilled or seawater

Desulfurant sorbents prepared by hydration, in sea or distilled water, of calcined sewage sludge (ash) and CaO at CaO/ash weight ratios of 0.2 or 3 at room temperature or at 90 º C, were characterized by X-ray diffraction in order to relate the X-ray composition of the sorbents to the preparation process and to the specific surface area of the obtained sorbents. Results show that the main compounds detected in the sludge´s ash are the same than those found in bibliography for the calcined sludge. In all the sorbents, independently of the preparation conditions, Ca(OH)2 was found instead of CaO used as raw material. New and different crystalline products were found in the sorbents depending on the preparation conditions. All the sorbents prepared in seawater contain NaCl in their composition; the specific surface area of the sorbents increased with hydration time and temperature and was lower when seawater was used for hydration.We are thankful to MICINN in Spain, National Plan for scientific Research, Development and innovation, for financial support under Project: MAT2010-18862

Slow pyrolysis of specialty coffee residues towards the circular economy in rural areas

Coffee, as one of the most consumed beverages, generates a wide variety of waste materials that can be used as biofuels and bio-products. Conventional pyrolysis can be used in rural areas, improving the circular bioeconomy of these places. In this work, the characterization and slow pyrolysis of specialty coffee residues, coffee silverskin (CSS), and spent coffee (SC) were conducted at temperatures from 300 to 600 °C. Physico-chemical and thermal analysis were carried out. In addition, the quantification of individual compounds as acetic, formic, and levulinic acids, caffeine, and other minor compounds was performed. The results indicate the differences between both waste materials in the obtained pyrolysis fractions. The biochar fraction for SC is lower at all temperatures and the liquid fraction higher, reaching maximum values of 62 wt.% in the liquid at 600 °C compared to 47% in CSS. The higher yield in the liquid fraction of SC corresponds to the higher contents of hemicellulose and extractives and the lower ash content. The calculated calorific value for the pyrolysis solid fractions reaches 21.93 MJ/kg in CSS and 26.45 MJ/kg in SC. Finally, biorefinery options of major components of the liquid fraction were also presented.This research was funded by EUROPEAN COMMISSION, Marie Sklodowska-Curie Actions—RISE, grant number 101007733 (CELISE project), by Solvay, under projects 3399 and 3824, and the European LignoCOST Action, number CA17128 (https://lignocost.eu/, accessed on 1 February 2023)

Procedimiento para la obtención de un sorbente captador de SO2.

Procedimiento para la preparación de una composición sorbente captador de SO2, constituido por la mezcla en agua de hidróxido de calcio y una arcilla a seleccionar dentro de sepiolita, esmectita o atapulgita. La mezcla se realizará a temperatura ambiente y sin el uso de catalizadores; dando como resultado tras el filtrado y secado del material un sorbente con elevado porcentaje de captación de SO2 por mol de calcio.Solicitud: 200901994 (14.10.2009)Nº Pub. de Solicitud: ES2336636A1 (14.04.2010)Nº de Patente: ES2336636B1 (24.11.2010

Use of TG-DSC-MS and gas analyzer data to investigate the reaction of CO2 and SO2 with Ca(OH)2 at low temperature

To investigate the reaction of calcium hydroxide with CO2 and SO2 simultaneously, a gas containing both gases reacted with the calcium base at 58 ºC and a relative humidity of 55 %. Different CO2 and SO2 concentrations were performed being the composition of the gas stream 12, 6 or 0 % CO2; 5000, 2500, 1000 or 0 ppm SO2, 9.5 % synthetic air and balanced N2, with a flue gas rate of 1000 mL/minute. A continuous gas analyzer controlled the CO2 and SO2 concentrations in the effluent gas and the breakthrough curves of both gases were obtained. The gas analyzer data show that SO2 and CO2 compete to react with the base reacting simultaneously. By using thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) techniques, calcium sulphite hemihydrate, CaSO3.1/2H2O, was identified as the unique desulfurization product detected. CaSO4 was not identified although O2 was present in the gas mixture. CaCO3 was the main product of the reaction of calcium hydroxide and CO2 being the complex CaO.CO2 another possible product synthesized in low amounts. From analyzer data it was proved that a part of the CaCO3 present in the sorbent or synthesized in the process reacts with the SO2 and release CO2. Results of this work show that the combination of continuous gas analyzer data and TG-DSC-MS techniques, not used before to study this reaction, is a good and easy way to clarify the process and the products of reaction.Our acknowledgment to M.C. y T. for financial support of this work under Project MAT 2010-18862

Use of ash from sewage sludge in the preparation of desulfurant sorbents

This work aims to develop new uses for sewage sludge, which is a byproduct of municipal wastewater treatment plants, by examining the calcination of this waste, the characterization of ashes is obtained, and its use to prepare desulfurant sorbents. Samples of sewage sludge were obtained from a local municipal wastewater treatment plant. This plant applies a pre-treatment followed by a biological treatment, where anaerobic digestion and centrifugation reduces the sludge. Three samples were characterized (in humidity, volatile and fixed solids content), dried, and ignited at two temperatures, 550 and 750 C. The composition of the ash obtained at both ignition temperatures was studied by x-ray fluorescent spectroscopy and the BET specific surface area of the two ashes and of the prepared sorbents was measured. Ash composition was similar for the two temperatures tested, where the components were Si, Ca, Al, Fe, P, S, Mg, K, Cl, Zn and Ti. BET specific surface area values indicate that the lower temperature of calcination produces ash with the highest SSA values (18 m2/g against near 10 m2/g). Preparation of desulfurant sorbents was carried out by mixing the ash with CaO or Ca(OH)2 at room temperature and different experimental conditions. The BET SSA of the prepared desulfurant sorbents showed higher values for the sorbents prepared with the ashes obtained at the lowest temperature. The behaviour of the ash and the prepared sorbents was tested in a fixed bed reactor at 58 C with a flue gas containing 5000 ppm of SO2 with a relative humidity of 55%. Results in the desulfurization process show that the calcium from the sludge seems more efficient than the calcium added as CaO or Ca(OH)2 to prepare the sorbents

Study of the thermal behavior of sewage sludge from a WWTP in Cantabria (Spain) by TG-DSC-MS

According to European Directive and national regulations in Spain, techniques based on thermal decomposition are proposed for the sewage sludge disposal. In this work, the sludge from the wastewater treatment plant (WWTP) of Casar de Periedo, in Cantabria (Spain) is studied by Thermogravimetry – Differential Scanning Calorimetry – Mass Spectrometry (TG –DSC – MS). A sample of this sludge was submitted, after drying, to different atmospheres: 100 % He, N2 /air or He/air 80/20 and 100 % air, from 20 to 900 ºC, to study primary decomposition reactions in pyrolysis, gasification and combustion respectively. The purpose was to determine the weight loss at different temperatures, the heat flow at each atmosphere and the presence of some gas products like H2, CO, CO2, CH4, or HCl, SO2, SO3, NO and NO2 released, these last five gases to know the contaminants emitted. Combustion conditions (air) rend the greatest mass loss and energy production. Reactions take place at lower temperatures, being mainly CO2 and H2O the products detected in MS, with little amounts of CH4, as it is expected for mainly total oxidation reactions. In gasification conditions, essayed with two atmospheres (N2-air and He-air), quantitative results found are similar, but the highest thermal conductivity of He produces exothermic reactions at lower temperatures, observed in the mass loss and heat flow profiles. From reactions of decomposition, partial oxidation and total oxidation, CO2, H2, H2O and CH4, were identified by MS. Pyrolysis conditions (He) produce the lowest mass loss and slightly endothermic reactions, mainly because of decomposition reactions. Higher H2 amounts were obtained at higher temperatures than in gasification conditions. No gas contaminant (HCl, SO2, SO3, NO and NO2) has been detected by MS, considering this sewage sludge as a “clean sludge”. Comparing the thermal behaviour of the sewage sludge of this plant to that obtained in the WWTP of Santander, the sludge from Casar de Periedo is more appropriated to thermal valorization.We are thankful to MICINN in Spain, National Plan for scientific Research, Development and innovation, for financial support under Project: MAT2010-18862

Química (G986). Febrero 2015

Grado en Ingeniería en Electrónica Industrial y Automátic

Química (G986). Septiembre 2014

Grado en Ingeniería en Electrónica Industrial y Automátic

Desulfurization behaviour of CaCO3 added during the calcination of wastewater sludge at 900º C: reuse of the ash after reactivation

In the present work dry sewage sludge from a local municipal wastewater plant, has been incinerated at 900 º C with CaCO3 added at two sludge/CaCO3 ratios: 10 sludge /1 CaCO3 or 10 sludge /10 CaCO3 in weight. The ability of this salt to capture the SO2 produced during the incineration is studied. The SO2 captured is quantified as mole SO2 / mole of Ca. Results shows that the amount of SO2 captured /mole of CaCO3, is much higher at the 10 sludge /1 CaCO3 ratio. With the resulting ashes, reactivated at different ways, desulfurant sorbents were prepared and essayed in a desulfurization process at low temperature. Results of the process at low temperature showed that the highest value of SO2 captured was found with the sorbent coming from the ashes obtained from the mixture 10 sludge /1 CaCO3 and reactivated by hydration at room temperature