Wojciech M. Budzianowski

Mitigating NH3 Vaporization from an Aqueous Ammonia Process for CO2 Capture

An aqueous ammonia process (AAP) offers several advantageous technological features over other existing reactive absorption-based CO2 capture processes such as increased CO2 absorption loading capacity, no oxidative solvent degradation, no corrosion problems, high CO2 absorption fluxes and low energy input needed for solvent regeneration. It has also the potential of capturing multiple flue gas components (SO2, NOX, and CO2) and producing value added chemicals, such as ammonium sulfate, ammonium nitrate and ammonium bicarbonate, which are commonly used as fertilizers. Unfortunately, a major drawback of the AAP is NH3 volatility resulting in NH3vaporization to the flue gas. Therefore, the current article presents the results of experimental and numerical investigations directed at in-depth understanding of the AAP and at developing of new methods for mitigating the unwanted NH3 vaporization. For this purpose three types of reactor configurations are studied: (i) packed bed, (ii) falling film and (iii) membrane. The bench-scale experiments realized in the counter-current packed bed reactor reveal, that NH3 vaporization can be minimized under the conditions of low temperature, pH, and flow rate of flue gas and under the conditions of high pressure and flow rate of aqueous ammonia. Further, from the detailed 2D modeling of the AAP realized in the falling film reactor it is found, that NH3 vaporization can be mitigated by making use of the mechanisms of negative enhancement of mass transfer and of migrative mass transport. Finally, the potential benefits of using membrane facilitated AAP reactors are discussed.

Superadiabatic Lean Catalytic Combustion in a High-Pressure Reactor

The isobaric lean catalytic combustion in a high-pressure recuperative reactor in view of gas turbine technologies is examined. A new type of the T/P bifurcation diagram is revealed and elucidated. It is found that the reactor thermally stabilizes at higher pressures. The elevated P to 0.5 MPa extends bifurcation isola for mfin, i.e. each fold is improved by approximately 15%. The thermal and concentration hysteresis bifurcation diagrams are also improved, i.e. the ignition temperature was decreased from 490 to 475 K and the extinction concentration from 177 to 157 ppmv, respectively. The pressure drops are alleviated by the factor of P/P0 slightly corrected for the gas thermal expansion effect. It is also revealed, that the intra-phase mass transfer resistances are reduced at elevated pressures. The fuel conversion pressure dependences are provided for some types of high-pressure reactors.

Experimental and Numerical Study of Recuperative Heat Recirculation

In many power-generating systems heat recirculation is needed in order to increase their thermal efficiency and ensure sufficiently high temperatures required in fuel processing. The current article investigates experimentally and numerically a heat recirculation phenomenon by using gas–gas recuperation. The systematized description of practicalities of heat recirculation is reported. The experimental characteristics of a heat recirculator are presented in terms of the effect of power of the heater at constant mass flow rate, effect of mass flow rate at constant power of the heater, and effect of mass flow rate at constant ratio power of the heater/mass flow rate on heat transferred, heat lost to the surroundings, and processing temperatures. The results show that heat recirculation is maximized at moderate mass flow rate, at large power, and in miniaturized channels. Further, a numerical model is used in order to interpret and extend the experimental data set. The simulations are focused on heat recirculation under conductive, dispersive, and convective regimes of heat transfer. Finally, the principles of thermal integration of power-generating systems by using heat recirculation are expounded.

Effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of CNG–biodiesel in a dual-fuel engine

The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines has led to an interest in finding alternative fuels to diesel. Emission control and engine efficiency are two of the most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V has forced research towards developing new technologies for combating engine emissions. This paper examines the effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of compressed natural gas (CNG) blended with Honge oil methyl esters (HOME) in a dual fuel engine. The present results show that the combustion of HOME and 15% ethanol blend with CNG induction in a dual-fuel engine operated in optimized parameters at an injection timing of 27° Before Top Dead Centre and a compression ratio of 17.5 resulted in acceptable combustion emissions and improved brake thermal efficiencies. The implementation of swirl augmentation techniques increased brake thermal efficiencies (BTEs) and considerably reduced combustion emissions such as smoke, HC, CO and NOx. The addition of ethanol also increased BTEs. However, at more than 15% of ethanol in HOME, NOx emissions increased dramatically.

Design of Dynamics of a Recuperative Catalytic Combustor: Enhancement in Operation and Control

The current contribution is aimed to describe and design the dynamics of the recuperative catalytic combustor. The step responses of the combustible concentration, fuel flow rate, fuel temperature and three manipulated variables are determined for the non-controlled combustor. The time delays, time constants and gains are determined for the temperatures measured in two points in the catalytic zone and its dependencies on the process and geometrical parameters are discussed. The frequency response analysis conducted shows that in the combustor with a higher time constant medium term input disturbances are effectively attenuated. In order to handle long term impulses of lean or rich fuels, the control strategy dedicated to the current combustor is proposed. It is verified in the example in which the frequently used control algorithm is applied to simulate the process control. The results show that the improvement is attained in combustor transient operation and control.

Predictions of biochar production and torrefaction performance from sugarcane bagasse using interpolation and regression analysis

This study focuses on the biochar formation and torrefaction performance of sugarcane bagasse, and they are predicted using the bilinear interpolation (BLI), inverse distance weighting (IDW) interpolation, and regression analysis. It is found that the biomass torrefied at 275°C for 60min or at 300°C for 30min or longer is appropriate to produce biochar as alternative fuel to coal with low carbon footprint, but the energy yield from the torrefaction at 300°C is too low. From the biochar yield, enhancement factor of HHV, and energy yield, the results suggest that the three methods are all feasible for predicting the performance, especially for the enhancement factor. The power parameter of unity in the IDW method provides the best predictions and the error is below 5%. The second order in regression analysis gives a more reasonable approach than the first order, and is recommended for the predictions.

Perspectives for low-carbon electricity production until 2030: Lessons learned from the comparison of local contexts in Poland and Portugal

ABSTRACT This paper compares perspectives for low-carbon electricity production in two EU member states – Poland and Portugal until 2030. Electricity production capacities, carbon emissions of electricity production, and production cost of electricity (COE) of Poland and Portugal are analyzed. The dilemmas of investments into low-carbon electricity production technologies relying on: (i) renewable energy sources (RES), (ii) nuclear fuel, and (iii) fossil fuels integrated with carbon capture and sequestration (CCS) are discussed. Roadmap 2050 recommends about 40% decarbonization of electricity generation by 2030 and 100% by 2050. Based on electricity production mix forecast for 2030, carbon emissions of electricity are estimated at 163 GgC TWhe−1 in Poland and at 93.2 GgC TWhe−1 in Portugal. Therefore, both compared countries must implement energy policies aimed at carbon emissions reduction through expanded utilization of RES (Poland – bioenergy, wind; Portugal – hydro, wind, solar), advanced CCS options (using local synergy opportunities), and optionally nuclear power (Poland).