Hrvoje Mikulčić

Numerical study of co-firing pulverized coal and biomass inside a cement calciner

The use of waste wood biomass as fuel is increasingly gaining significance in the cement industry. The combustion of biomass and particularly co-firing of biomass and coal in existing pulverized-fuel burners still faces significant challenges. One possibility for the ex ante control and investigation of the co-firing process are computational fluid dynamics (CFD) simulations. The purpose of this paper is to present a numerical analysis of co-firing pulverized coal and biomass in a cement calciner. Numerical models of pulverized coal and biomass combustion were developed and implemented into a commercial CFD code FIRE, which was then used for the analysis. Three-dimensional geometry of a real industrial cement calciner was used for the analysis. Three different co-firing cases were analysed. The results obtained from this study can be used for assessing different co-firing cases, and for improving the understanding of the co-firing process inside the calculated calciner.

Numerical analysis of cement calciner fuel efficiency and pollutant emissions

Efficient mixing of pulverized fuel and limestone particles inside cement calciners is important due to the reason that the calcination process directly affects the final fuel consumption. The focus of this paper is on the numerical analysis of cement calciner’s operating conditions and pollutant emissions. The paper analyzes the influence of different amounts of fuel, mass flow of the tertiary air and the adiabatic wall condition on the decomposition rate of limestone particles, burnout rate of coal particles, and pollutant emissions of a newly designed cement calciner. Numerical models of calcination process and pulverized coal combustion were developed and implemented into a commercial computational fluid dynamics code, which was then used for the analysis. This code was used to simulate turbulent flow field, interaction of particles with the gas phase, temperature field, and concentrations of the reactants and products, by solving the set of conservation equations for mass, momentum, and enthalpy that govern these processes. A three-dimensional geometry of a real industrial cement calciner was used for numerical simulations. The results gained by these numerical simulations can be used for the optimization of cement calciner’s operating conditions, and for the reducing of its pollutant emissions.

CO2 emission reduction in the cement industry

The cement industry is one of the largest carbon emitting industrial sectors in the European Union (EU)and in the world. In line with the EU commitment to combat climate change, the cement industry needs to decrease significantly carbon emission. The cement manufacturing process is not only a source of combustion related CO2 emissions, but it is also a large source of industrial process related CO2 emissions. There are several effective measures which can be applied in cement manufacturing processes to achieve emissions reduction targets. Simultaneously, these measures can reduce the local environmental impacts and improve the competitiveness of the cement industry. In this paper, the following measures for CO2 emission reduction were analyzed in order to identify their environmental effectiveness: use of alternative fuels, more efficient kiln process, and co-production of synthetic fuels. The study was done on the case of a Macedonian cement plant. It was confirmed that the implementation of the selected mitigation measures results in substantial CO2 emission reduction.

Environmental management as a pillar for sustainable development

There is a growing concern about how to minimize the impact of human activities on the environment. Already nowadays, in some places adaptation efforts are needed in order to avoid the irreversibility of negative human activities. Due to climate changes, and corresponding environmental and social changes, there is a great need for a more sustainable development of mankind. Over the years, research studies that analyzed the sustainable development of different communities with a multi-disciplinary approach, stressed the necessity of preserving the environment for next generations. Therefore, responsible and conscientious management of the environment is a pillar of the sustainable development concept. This review introduction article provides an overview of the recent top scientific publications related to sustainable development that mostly originated from previous SDEWES conferences.

CFD analysis of a cement calciner for a cleaner cement production

Cement calciners are pyroprocessing units found in modern cement plants. Inside of them occurs a strong endothermic reaction known as the calcination process, and the combustion of pulverized solid fuels. Controlling the mixing of limestone and pulverized fuel particles is of particular importance because it directly affects the energy consumption. The paper analyzes the impact of an axial and a swirl burner on the mixing of the particles, pollutant emissions and the operating conditions of a newly designed cement calciner. All necessary numerical models were developed and implemented into a commercial computational fluid dynamics code FIRE, which is then used for the analysis. This code is used to simulate turbulent flow field, temperature field, concentrations of the reactants and products as well as the interaction of particles with the gas phase, by solving the set of conservation equations for mass, momentum and enthalpy governing these processes. The results gained by these simulations can be used for the optimization of cement calciner’s operating conditions.

Shaping sustainable development to support human welfare

Due to increased environmental awareness and social responsibility, social and human welfare have been increasingly viewed through the prism of sustainable development. As sustainable development is a highly multi-disciplinary field of research, a considerable number of studies have been devoted to this issue. The studies show that sustainable development has become an urgent task for the international community, academia, industry experts, policy makers and the general public, due to the rapidly growing social challenges of mankind. This review article provides a short assessment of the current state-of-the art papers related to sustainable development covered in the recent publications mostly originated from previous SDEWES conferences.

Waste heat utilisation of Croatian cement industry accounting Total Site demands

Abstract The cement industry sector as an energy intensive industrial sector, where energy cost represents approximately 40% of the total production cost per one ton of cement, and one of the highest greenhouse gases - GHG emitting industrial sectors, accounts for around 5% of global anthropogenic GHG emissions as reported (Mikulcic et al, 2015). Considering that, the cement is the most widely used material for construction needs, this paper analyses the potential of energy efficiency improvement of the cement production for a particular cement plant in Croatia. The heat recovery potential was determined and an amount of waste heat available for utilisation accounting site wide demands are identified with use of Process Integration technique. The results show huge potential for energy saving of cement production. Different scenarios for utilization of low potential heat are proposed accounting different site demands and energy prices. Implementation of paper results helps to the cement plant’s profitability and reduces environmental impact of the cement industry.

Mitigation of Climate Change by Reducing Carbon Dioxide Emissions in Cement Industry

The cement industry is an energy intensive industry, and one of the largest carbon emitting industrial sectors. It is emitting 5 % of global anthropogenic carbon dioxide emissions, with especially high growth in Asia. While the energy efficiency of cement production has been increased significantly, the emissions can be further reduced by replacing conventional fossil fuels with alternative ones, mostly of waste origin. Due to the lower heating value of waste derived fuels than of the standardly used coal, the use of such fuels is possible where there is no need for very high process temperatures, e.g. in cement calciners where the desirable operating temperature is around 950 °C. Using waste derived fuels in cement calciners does not only reduce combustion related CO2 emissions in cement production by 10-30 %, depending on the amount of used waste derived fuels and the biogenic fraction in the used waste derived fuel, but is also an environmentally beneficial alternative to waste landfill disposal. However, incineration of high share of waste derived fuels in cement calciners still faces significant challenges. A possibility for the ex-ante control and investigation of the incineration process are Computational Fluid Dynamics - CFD simulations. Early comprehensive information, parametric studies and initial conclusions that can be gained from CFD simulations are very important in handling modern combustion units. The purpose of this paper is to present the benefit of using waste derived fuels in the cement industry, and to give some preliminary results on waste incineration numerical modelling.

Low NOx combustion and SCR flow field optimization in a low volatile coal fired boiler

Low NOx burner redesign and deep air staging have been carried out to optimize the poor ignition and reduce the NOx emissions in a low volatile coal fired 330 MWe boiler. Residual swirling flow in the tangentially-fired furnace caused flue gas velocity deviations at furnace exit, leading to flow field unevenness in the SCR (selective catalytic reduction) system and poor denitrification efficiency. Numerical simulations on the velocity field in the SCR system were carried out to determine the optimal flow deflector arrangement to improve flow field uniformity of SCR system. Full-scale experiment was performed to investigate the effect of low NOx combustion and SCR flow field optimization. Compared with the results before the optimization, the NOx emissions at furnace exit decreased from 550 to 650 mg/Nm³ to 330-430 mg/Nm³. The sample standard deviation of the NOx emissions at the outlet section of SCR decreased from 34.8 mg/Nm³ to 7.8 mg/Nm³. The consumption of liquid ammonia reduced from 150 to 200 kg/h to 100-150 kg/h after optimization.

A kinetic study on the catalysis of KCl, K2SO4, and K2CO3 during oxy-biomass combustion

Biomass combustion under the oxy-fuel conditions (Oxy-biomass combustion) is one of the approaches achieving negative CO2 emissions. KCl, K2CO3 and K2SO4, as the major potassium species in biomass ash, can catalytically affect biomass combustion. In this paper, the catalysis of the representative potassium salts on oxy-biomass combustion was studied using a thermogravimetric analyzer (TGA). Effects of potassium salt types (KCl, K2CO3 and K2SO4), loading concentrations (0, 1, 3, 5, 8 wt%), replacing N2 by CO2, and O2 concentrations (5, 20, 30 vol%) on the catalysis degree were discussed. The comparison between TG-DTG curves of biomass combustion before and after water washing in both the 20%O2/80%N2 and 20%O2/80%CO2 atmospheres indicates that the water-soluble minerals in biomass play a role in promoting the devolatilization and accelerating the char-oxidation; and the replacement of N2 by CO2 inhibits the devolatilization and char-oxidation processes during oxy-biomass combustion. In the devolatilization stage, the catalysis degree of potassium monotonously increases with the increase of potassium salt loaded concentration. The catalysis degree order of the studied potassium salts is K2CO3 > KCl > K2SO4. In the char-oxidation stage, with the increase of loading concentration the three kinds of potassium salts present inconsistent change tendencies of the catalysis degree. In the studied loading concentrations from 0 to 8 wt%, there is an optimal loading concentration for KCl and K2CO3, at 3 and 5 wt%, respectively; while for K2SO4, the catalysis degree on char-oxidation monotonically increases with the loading potassium concentration. For most studied conditions, regardless of the potassium salt types or the loading concentrations or the combustion stages, the catalysis degree in the O2/CO2 atmosphere is stronger than that in the O2/N2 atmosphere. The catalysis degree is also affected by the O2 concentrations, and the lowest catalysis degree is generally around 20 vol% O2 concentration. The kinetic parameters under the different studied conditions are finally obtained.