• Aqueous carbonation of oil shale wastes from Estonian power production for CO2 fixation and PCC productionUibu, Mai; Velts, Olga; Kuusik, Rein, keemikCYSENI 2011 : the 8th Annual International Conference of Young Scientist on Energy Issues, May 26-27, 2011, Kaunas, Lithuania : conference proceedings2011 / p. 415-424 : ill
• Ca2+-ioonide leostuvus põlevkivituhkadestVelts, Olga; Uibu, Mai; Rudjak, Irina; Kuusik, Rein, keemikXXX Eesti keemiapäevad : teaduskonverentsi teesid = 30th Estonian Chemistry Days : abstracts of scientific conference2007 / lk. 187-188
• Calcium carbonate crystallization on the basis of waste oil shale ash leachatesVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikISIC 18 : 18th International Symposium on Industrial Crystallization : 13-16 September 2011, Zurich, Switzerland : book of abstracts2011 / p. 501 : ill
• CO2 mineral trapping : modeling of calcium carbonate precipitation in a semi-batch reactorVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikEnergy procedia2011 / p. 771-778 : ill
• CO2 mineralisation : concept for co-utilization of oil shale energetics waste streams in CaCO3 productionVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikEnergy procedia2013 / p. 5921-5928 : ill https://www.sciencedirect.com/science/article/pii/S1876610213007613 https://doi.org/10.1016/j.egypro.2013.06.518 https://www.scopus.com/sourceid/17700156736 https://www.scopus.com/record/display.uri?eid=2-s2.0-84898720725&origin=resultslist&sort=plf-f&src=s&sot=b&sdt=b&s=DOI%2810.1016%2Fj.egypro.2013.06.518%29&sessionSearchId=45109fc468f65f7960967c9a10ed35d7 https://www.webofscience.com/wos/woscc/full-record/WOS:000345500506020
• CO2 mineralisation : production of CaCO3-type material in a continuous flow disintegrator-reactorVelts, Olga; Kindsigo, Merit; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikEnergy procedia2014 / p. 5904-5911 : ill https://doi.org/10.1016/j.egypro.2014.11.625 https://www.scopus.com/sourceid/17700156736 https://www.scopus.com/record/display.uri?eid=2-s2.0-84922883005&origin=inward&txGid=031b6c77f1a2c07fdf8c730a5b1da22e https://www.webofscience.com/wos/woscc/full-record/WOS:000361211506011
• CO2 trapping from flue gases by oil shale ash aqueous suspension : Intensification and modeling of the processKuusik, Rein, keemik; Uibu, Mai; Velts, Olga; Trikkel, Andres; Kallas, JuhaThird International Conference on Accelerated Carbonation for Environmental and Materials Engineering : ACEME10 : November 29 - December 1, 2010, Turku, Finland : proceedings2010 / p. 227-235 : ill
• Co-utilization of CO2 and oil shale combustion wastes for production of PCC-type materialVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemik12th International Conference on Carbon Dioxide Utilization : ICCDU XII 2013 : June 23-27, 2013, Alexandria, VA, USA, Westin Hotel2013 / p. 230
• Co-utilization of CO2 and waste oil shale ash to produce calcium carbonateVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemik11th International Conference on Carbon Dioxide Utilization (ICCDU XI), June 27-30, 2011, Dijon, France : programm & abstracts2011 / p. P133 : ill
• Crystallization of calcium carbonate on the basis of oil shale waste ash in a continuous flow disintegrator-reactorVelts, Olga; Kindsigo, Merit; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikISIC 19 : 19th International Symposium on Industrial Crystallization : book of abstracts : 16-19 September 2014, Toulouse - France2014 / p. 359-360 : ill
• Developments in CO2 mineral carbonation by oil shale ashUibu, Mai; Velts, Olga; Trikkel, Andres; Kallas, Juha; Kuusik, Rein, keemik2nd International Conference on Accelerated Carbonation for Environmental and Materials Engineering : October 1-3, 2008, Rome, Italy : proceedings2008 / p. 421-430 : ill
• Developments in CO2 mineral carbonation of oil shale ashUibu, Mai; Velts, Olga; Kuusik, Rein, keemikJournal of hazardous materials2010 / p. 209-214 : ill
• Edusammud põlevkivituha uudsete rakenduste väljatöötamisesVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikXXXII Eesti Keemiapäevad : teaduskonverentsi teesid2011 / lk. 107 : ill
• Eesti põlevkivienergeetikas tekkivate tahkjäätmete märgkarboniseerimine SO2 emissiooni vähendamiseks ning SKK saamiseksUibu, Mai; Velts, Olga; Kuusik, Rein, keemikXXXII Eesti Keemiapäevad : teaduskonverentsi teesid2011 / lk. 103
• Efforts in oil shale ash indirect carbonation accompanied by PCC-type material formationVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikProceedings of the 4th International Conference on Accelerated Carbonation for Environmental and Materials Engineering : ACEME 2013 : April 9-12, 2013, Leuven, Belgium2013 / p. 341-348 : ill
• From waste to value : CaCO3 crystallization on the basis of waste oil shale ashVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikProceedings of the Air & Waste Management Association’s (A&WMA) 105th Annual Conference & Exhibition2012 / [10] p. : ill
• Kaltsiumi leostumine põlevkivituhast - protsessi modelleerimineVelts, Olga; Kallas, Juha; Kuusik, Rein, keemikXXXI Eesti keemiapäevad : [28. aprill 2010, Tallinn] : teaduskonverentsi teesid = 31st Estonian Chemistry Days : abstracts of scientific conference2010 / lk. 81
• Modeling calcium dissolution from oil shale ash. Part 1, Ca dissolution during ash washing in a batch reactorVelts, Olga; Hautaniemi, Marjaana; Kallas, Juha; Kuusik, Rein, keemikFuel processing technology2010 / 5, p. 486-490 : ill https://www.sciencedirect.com/science/article/abs/pii/S0378382009003567
• Modeling calcium dissolution from oil shale ash. Part 2, Continuous washing of the ash layerVelts, Olga; Hautaniemi, Marjaana; Kallas, Juha; Kuosa, Markku; Kuusik, Rein, keemikFuel processing technology2010 / 5, p. 491-495 : ill https://www.sciencedirect.com/science/article/pii/S0378382009003579
• Modeling of calcium leaching from lime-consisting oil shale combustion ashVelts, Olga; Kallas, Juha; Kuusik, Rein, keemikThird International Conference on Accelerated Carbonation for Environmental and Materials Engineering : ACEME10 : November 29 - December 1, 2010, Turku, Finland : proceedings2010 / p. 323-326 : ill https://www.sciencedirect.com/science/article/abs/pii/S0378382009003579
• Modelling of CO2 mass transfer and hydrodynamics in a semi-batch reactorVelts, Olga; Hautaniemi, Marjaana; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikJournal of international scientific publication : materials, methods & technologies2010 / 2, p. 68-79 : ill https://www.researchgate.net/publication/284688605_Modelling_of_CO2_mass_transfer_and_hydrodynamics_in_a_semi-batch_reactor
• Oil shale ash as a source of calcium for calcium carbonate : process feasibility, mechanism and modeling = Põlevkivituhk kaltsiumkarbonaadi toormena : protsessi teostatavus, mehhanism ja modelleerimineVelts, Olga2011
• Ozonation of lignin aqueous solutionsKamenev, Inna; Velts, Olga; Viiroja, Andres; Häkkinen, Antti; Kallas, JuhaExecutive summaries : 5th International Conference. 10th IOA-EA3G Berlin Conference on Oxidation Technologies for Water and Wastewater Treatment : Berlin, Germany, March 30 - April 2, 20092009 / p. 39-40/PC223(1-8)
• Prospects in waste oil shale ash sustainable valorizationVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikWorld Academy of Science, Engineering and Technology2011 / p. 451-455 : ill
• Reduction of CO2 emissions by carbonation of alkaline wastewaterUibu, Mai; Velts, Olga; Trikkel, Andres; Kuusik, Rein, keemikAir pollution XVI2008 / p. 311-320 : ill
• Utilization of oil shale ash to prepare PCC : leachibility dynamics and equilibrium in the ash-water systemVelts, Olga; Uibu, Mai; Rudjak, Irina; Kallas, Juha; Kuusik, Rein, keemikEnergy procedia2009 / p. 4843-4850 : ill https://www.sciencedirect.com/science/article/pii/S1876610209009552
• Waste oil shale ash as a novel source of calcium for precipitated calcium carbonate : carbonation mechanism, modeling, and product characterizationVelts, Olga; Uibu, Mai; Kallas, Juha; Kuusik, Rein, keemikJournal of hazardous materials2011 / p. 139-146 : ill