Investigation of anthropogenic greenhouse gas emissions generated through the production of Portland cement and a comparison of mitigation strategies

The purpose of this project investigates the projected anthropogenic C⁰² emissions generated through the production of Portland cement at three manufacturing facilities in southern California. Research consisted of projecting annual greenhouse gas emission inventories for three case studies pursuant to Assembly Bill 32, The Global Warming Solution Act of 2006, which requires mandatory reporting of large producers of greenhouse gas emissions in California

Rotary kiln incineration of hazardous wastes: pilot-scale studies at Louisiana State University

Studies of incineration of surrogates for hazardous wastes are conducted in the pilot-scale rotary kiln incinerator (RKI) at Louisiana State University (LSU) in Baton Rouge, Louisiana. The purpose of the research is to investigate methods of treating and destroying hazardous wastes in a cost-effective and environmentally sound way. The objective is to provide process data that will contribute to increased knowledge for RKI design and operation. The LSU facility is a College of Engineering Combustion Laboratory that is unique in its large size as a university laboratory. It is equipped with individual instruments for analysis of O2, CO, CO2, HCl, SOx and NOx and a mass spectrometer to continuously monitor products of combustion for rigorous evaluation of efficiencies of operation. Experiments conducted to investigate parameters and variables affecting the design and operation of the kiln substantiate mathematical treatment of material and energy balances. These investigations add new and useful data to be used in design of rotary kilns, a major objective of this research. One of the principal contributions of this dissertation relates to the effects of batch feeding on instability of the combustion process. Surges in temperature, pressure, and their effects on products of incomplete combustion are discussed. Other activities of the combustion laboratory are described: Incineration of still bottoms to recover byproduct potash produced by the Audubon Sugar Institute; burning of synthetic fireplace logs; study of incinerator stack gases; and determination of rates of fugitive emissions from flanges and valves. Economics of operation and maintenance of the facility are calculated, tabulated, and related to contract charges for combustion studies on behalf of industrial clients. Future prospects for the laboratory as a research and teaching facility are discussed

Numerical modelling of thermochemical processes inside a cement calciner for a cleaner cement production

Trenutna proizvodnja cementa suočena je s dva značajna problema. Prvi je proizvodnja velike količine stakleničkih plinova, oko 5 % ukupnih globalnih CO2 emisija ljudskog podrijetla, a drugi je visoka cijena goriva, uglavnom ugljena. Proizvođači cementa su stoga pod sve većim pritiskom da smanje potrošnju fosilnih goriva i s njima povezanim emisijama stakleničkih plinova. Utvrđeno je da je djelomična zamjena ugljena alternativnim gorivima, poput biomase i goriva dobivenih obradom otpada, može imati važnu ulogu u smanjenju CO2 emisija. Kako je zbrinjavanje otpada na odlagalištima zadnja opcija u strategiji upravljanja otpadom, energetska oporaba goriva dobivenog obradom otpada, poznatijeg kao kruto gorivo iz otpada (engl. solid recovered fuel - SRF), ima veliki potencijal u cementnoj industriji. Spaljivanje visokog udjela SRF-a u cementnim kalcinatorima još se uvijek suočava sa značajnim izazovima, poglavito jer je dobro poznato da upotreba alternativnih goriva u postojećim plamenicima mijenja oblik plamena, profil temperatura unutar peći, te izgorenost samog goriva koje se koristi. Korištenjem računalne dinamike fluida (engl. computational fluid dynamics - CFD) moguće je prethodno ispitivati i kontrolirati proces izgaranja različitih vrsta goriva. CFD simulacije su se tokom godina pokazale kao moćan alat za razvoj i optimizaciju kemijskih procesa te samih uređaja unutar kojih se te kemijske reakcije odvijaju. One mogu pokazati neke važne karakteristike strujanja fluida i miješanja više faza koje je teško eksperimentalno istražiti i stoga je CFD, zajedno sa eksperimentima i teorijom, postao sastavni dio istraživanja procesa izgaranja goriva. Glavna tema ovog rada bila je postizanje fizički točne i numerički učinkovite metode za simuliranje termo-kemijskih procesa koji se odvijaju unutar cementnog kalcinatora. To je podrazumijevalo dobro poznavanje najmodernijih modela izgaranja krutih goriva kao što su modeli za izgaranje ugljena, biomase i goriva iz čvrstog otpada, kao i pravilno definiranje endotermnog procesa kalcinacije. Kako bi se ispravno numerički proučavala uloga i interakcija izgaranja krutih goriva i termičkog raspadanja vapnenca unutar cementnog kalcinatora, upotrijebljeni su novi i poboljšani fizikalni i kemijski modeli. Nadalje, kako bi se provjerila točnost numeričkog modeliranja, novi modeli su se opsežno analizirali, a numerički dobiveni rezultati svakog novog modela su bili uspoređeni s dostupnim eksperimentalnim podacima. Primjenjivost razvijenog numeričkog modeliranja prikazana je na tri različite trodimenzionalne geometrije realnih industrijskih cementnih kalcinatora, koje su se koristile za detaljne numeričke simulacije.The present cement production is facing two main problems. The first one is the production of large amount of greenhouse gases, around 5 % of world’s anthropogenic CO2 emissions, and second one is the high fuel prices, mainly coal. The cement producers are therefore under increasing pressure to reduce their fossil fuel consumption and associated greenhouse gases emissions. It was found that partial substitution of coal by alternative fuels like waste derived fuels and biomass may play a major role in the reduction of CO2 emissions. As waste disposal at landfills is the last option in the waste management strategy, energy recovery of waste derived fuels, commonly known as solid recovered fuels – SRF, in the cement industry has a high potential. Incineration of high share of SRF in cement calciners still faces significant challenges, mainly because it is well known that the use of alternative fuels in existing pulverized burners alters the flame shape, the temperature profile inside the furnace, and the burnout of the fuels used. A possibility for the ex-ante control and investigation of the incineration process are computational fluid dynamics - CFD simulations. CFD simulations have shown to be a powerful tool during the development and optimisation of chemical engineering processes and involved apparatuses. They can show some important flow characteristics and mixing phenomena, which cannot be experimentally investigated, and because of that CFD together with experiments and theory, has become an integral component of combustion research. The main focus of this work was to achieve a physically accurate and numerically efficient method for simulation of thermo-chemical processes occurring inside a cement calciner. This implied good knowledge of state-of-the-art solid fuel combustion models, such as coal, biomass and solid recovered fuel combustion model, as well as proper definition of the endothermic calcination process. In order to correctly numerically study the role and interaction of solid fuel combustion and limestone calcination within cement calciner, new and improved physical and chemical models were introduced. To verify the accuracy of the modelling approach, the new models were extensively analysed, and the numerical predictions of each new model was compared with experimental data. To represent the applicability of the modelling approach, three different three dimensional geometries of real industrial cement calciners were used for the numerical simulations

NOx formation in iron ore rotary kilns

Iron ore pellets are often produced using the so-called Grate-Kiln process, which is designed to oxidize the magnetite (Fe3O4) to hematite (Fe2O3) and to sinter the pellets so they can be used in steel manufacturing. The heat required for this process comes from the combustion of a pulverized fuel in a rotary kiln, involving the formation of a jet flame. To oxidize the pellets, large amounts of air are introduced into the kiln, and an air-to-fuel equivalence ratio of 4–6 is obtained. Furthermore, the air is pre-heated to >1000\ub0C. High temperatures and large amounts of excess air are known to promote NOx formation and NOx emissions from iron ore processing plants are in general high.This thesis describes the NOx formation in the rotary kiln and identifies the governing parameters, with the aim of reducing the emissions. The work involves experiments in a pilot-scale kiln, as well as modeling work based on the same experiments. Data from a full-scale iron ore pelletization plant are also provided.From the experiments and the modeling work in this thesis, thermal NO is deemed to be of low importance in iron ore rotary kilns when solid fuels are combusted. Instead, the conditions during char combustion contribute significantly to the overall NOx formation. These results explain why many of the primary measures used to date have failed to achieve reductions in NOx emissions. Suggested additional primary measures include: raising the pyrolysis temperature (e.g., through oxygen addition) to deplete the char of nitrogen; or switching to a fuel with a lower nitrogen content (e.g., wood pellets). These are interesting alternatives for the future, and the latter may be tested in the coming years