Thermodynamic Analysis of Post-combustion Inertial CO2 Extraction System

Pilot scale testing and modeling of enzymatic reactive absorption in packed columns for CO2 capture

Role of CCS for Emission Reduction from Fertiliser and Cement Industry

Almost all coal based thermal power plants (CTPP) in India use electrostatic precipitator (ESP) for reduction of particulate matter (PM) in flue gas generated due to the combustion of Indian coal. This coal is characterized by high ash content, low calorific value and low sulfur content resulting in the generation of a very large amount of highly electrically‐resistive fly‐ash; thereby requiring a very large size ESP to minimize the fly‐ash emissions. However, the flue‐gas particle size distribution analysis showed that 60% of the particles are above 15 μm size, which can be conveniently removed using a low‐cost inertial separator such as a cyclone separator. It is proposed that a cyclone be used, as a pre‐cleaner to ESP so that the large size fraction of fly‐ash can be removed in the pre‐cleaning and the remaining flue‐gas entering the ESP will then contain only small size particles with low dust loading, thereby requiring a small ESP, and improving overall efficiency of dust removal. A low efficiency (65%), high throughput cyclone is considered for pre‐cleaning flue gas and the ESP is designed for removal of the remaining 35% fly‐ ash from the flue gas. It is observed that with 100% dust load, the ESP requires six fields per pass, whereas with cyclone as a pre‐cleaner, it requires only five fields per pass. Introducing cyclone into the flue gas path results in additional head loss, which needs to be overcome by providing additional power to induced draft (ID) fan. The permissible head loss due to the cyclone is estimated by comparing the power requirement in the bag filter control unit and cyclone‐ESP combined unit. It is estimated that a head loss of 10 cm of water can be permitted across the cyclone so as to design the same for 65% efficiency.

Beyond the big picture: Characterizaton of CO2-laden streams and implications for capture technologies

Flue gas from power plants can promote algal cultivation and reduce greenhouse gas emissions(1). Microalgae not only capture solar energy more efficiently than plants(3), but also synthesize advanced biofuels(2-4). Generally, atmospheric CO2 is not a sufficient source for supporting maximal algal growth(5). On the other hand, the high concentrations of CO2 in industrial exhaust gases have adverse effects on algal physiology. Consequently, both cultivation conditions (such as nutrients and light) and the control of the flue gas flow into the photo-bioreactors are important to develop an efficient "flue gas to algae" system. Researchers have proposed different photobioreactor configurations(4,6) and cultivation strategies(7,8) with flue gas. Here, we present a protocol that demonstrates how to use models to predict the microalgal growth in response to flue gas settings. We perform both experimental illustration and model simulations to determine the favorable conditions for algal growth with flue gas. We develop a Monod-based model coupled with mass transfer and light intensity equations to simulate the microalgal growth in a homogenous photo-bioreactor. The model simulation compares algal growth and flue gas consumptions under different flue-gas settings. The model illustrates: 1) how algal growth is influenced by different volumetric mass transfer coefficients of CO2; 2) how we can find optimal CO2 concentration for algal growth via the dynamic optimization approach (DOA); 3) how we can design a rectangular on-off flue gas pulse to promote algal biomass growth and to reduce the usage of flue gas. On the experimental side, we present a protocol for growing Chlorella under the flue gas (generated by natural gas combustion). The experimental results qualitatively validate the model predictions that the high frequency flue gas pulses can significantly improve algal cultivation.

The moisture content was a key factor affecting the permeability of the sintering granulation and the bed layer, and it promoted denitrification and combustion. This study investigated the influence of moisture content on denitrification, bed permeability, and the emissions of O2 and CO in the sintering process through industrial trials on-site. By analyzing sintering reaction mechanisms and SPSS data, and combining CHEMKIN simulation, the mechanism of moisture content on NO emissions during sintering was obtained. The results showed that the moisture content of the sintering mixture could affect the emission of NO in the sintering flue gas by influencing the permeability of the bed and the O2 and CO in the flue gas. As the moisture content of the mixture increased, the NO content in the sintering flue gas first decreased and then increased, while the permeability and CO content showed an initial increase followed by a decrease, and the volume fraction of O2 in the flue gas gradually decreased. Eight factors, including permeability index, O2 concentration, CO concentration, negative pressure, water vapor volume fraction, flue gas temperature, sintering trolley speed, and dust concentration, were significantly correlated with NO emissions, and a generalized linear model with NO emissions as the dependent variable was established. For a specific sintering industrial production, the moisture content of the sintering mixture determined the permeability. Apart from O2 concentration, permeability had the greatest impact and was negatively correlated with NO emissions. Water vapor in the flue gas could promote the CO-NO reaction, and the higher the water vapor volume fraction, the higher the reduction rate of NO, but excessively high levels were detrimental to permeability. Taking into account the permeability of the sintering bed, O2 and CO in the flue gas, the optimal moisture content (mass fraction) of the sintering mixture for denitrification during the sintering process ranged between 6.71% and 8.04%. In actual industrial sintering production, a water vapor volume fraction in the flue gas between 16% and 18% was most favorable for denitrification during the sintering process. These findings provided theoretical references for denitrification processes during sintering.

Molten carbonate fuel cells for CO2 separation and segregation by retrofitting existing plants – An analysis of feasible operating windows and first experimental findings

A low-temperature process employing activated carbon-based catalysts and operating downstream of the electrostatic precipitator (ESP) was evaluated jointly by Research Triangle Institute (RTI) and the University of Waterloo (Waterloo). The RTI-Waterloo process was projected to be capable of removing more than 95% SO{sub 2} and 75% NO{sub x }from coal combustion flue gas. In the process, the flue gas leaving the ESP is first cooled to approximately 100{degree}C. The SO{sub 2} is then catalytically oxidized to SO{sub 3} which is removed as medium-strength sulfuric acid in a series of periodically flushed trickle-bed reactors containing an activated carbon-based catalyst. The SO{sub 2}-free gas is then reheated to approximately 150{degree}C and NH{sub 3} is injected into the gas stream. It is then passed over a fixed bed of another activated carbon-based catalyst to reduce the NO{sub x} to N{sub 2} and H{sub 2}O. The clean flue gas is then vented to the stack. The feasibility of the process has been demonstrated in laboratory-scale experiments using simulated flue gas. Catalysts have been identified that gave the required performance for SO{sub 2} and NO{sub x} removal with <25 ppM NH{sub 3} slip. Potential for producing up to 10 N sulfuric acid by periodically flushing the SO{sub 2} removal reactor and further concentration to industrial strength 93.17% sulfuric acid was also demonstrated. Using the results of the experimental work, an engineering evaluation was conducted. Cost for the RTI-Waterloo process was competitive with conventional selective catalytic reduction (SCR) -- flue gas desulfurization (FGD) process and other emerging combined SO{sub 2}/NO{sub x} removal processes.

Particulate fouling is the process of deposition of extraneous particulate matter on other surfaces. In particular, particulate fouling is a major cause of concern in energy-intensive heat recovery systems like biomass gasifiers, coal fired boiler and waste incinerators. The thermal energy is extracted from the flue gas using a system of heat exchangers. The flue gas is however contaminated with particulate matter, tar, nitrogen, sulphur and alkali compounds. The contaminants are transported by the flue gas and interact with the heat exchanger surface eventually forming a deposit layer. The deposit layers have very low thermal conductivity and leads to drastic loss in thermal efficiency apart from maintenance problems and capital losses. The focus of this research is to understand the process of particulate fouling from a fundamental view point based on particle surface interactions and the global effects associated with process conditions by experiments. A numerical model to capture the deposition and removal of particles over heat exchanger surfaces is aimed at. Particles which arrive at the heat exchanger surface and undergo inertial impaction can stick to the surface, rebound and might remove other previously deposited particles. In order to model the process, a sticking criterion is necessary. The interaction of a particle with other particles on the heat exchanger surface can be either in a dry state or in the presence of a thin liquid film due to condensation of alkali compounds. Detailed experiments were performed to evaluate the sticking criterion for particle impaction over a liquid coated surface under elastic and elastic-plastic deformation conditions. An empirical relation in terms of Stokes number was evaluated to determine the energy loss in the thin interstitial liquid film. A critical Stokes number range between 3 and 8 was observed below which particles do not rebound from the surface. In the Stokes number range of 8 to 20, the particles were observed to rebound but do not overcome the viscous effects of the liquid layer. A high-temperature closed-loop vertical wind tunnel was designed and constructed to perform fouling experiments under controlled conditions. The effect of gas velocity, particle concentration, particle size distribution, gas temperature, heat exchanger tube orientation and geometry was studied. A measurement technique that allowed the evaluation of temporal evolution of the fouling layer thickness was used. The experimental investigations revealed that the shear induced by the gas flowing around the tube has a major effect on the overall deposit growth dynamics. The geometry and orientation of the tube indicated that deposition and removal of particles is strongly coupled to the flow dynamics and particle surface interactions. A numerical model was implemented in a commercial software package to capture the deposition and removal of particles. The deposition model was based on particle-surface interactions including elastic-plastic deformations and the removal model was based on the rolling moment induced by the flow and on the energy transferred by other impacting particles. The fundamental impaction experiments along with the controlled experiments have provided better insight into the process of particulate fouling and resulted in the development of a numerical model which can be used to devise mitigation strategies for particulate fouling.

Air pollution is a complex issue with numerous causes and effects and few remedies, which is exacerbated globally by environmental pollutants from automobiles, factories, and chemicals found in consumer goods. "Wet Scrubber" is one of the solutions utilised as a pollution control device. An apparatus called a wet scrubber eliminates impurities from flue gas and other gas streams. The scrubbing liquid and the dirty gas stream come into contact in a wet scrubber. To get rid of the impurities, the cleaning liquid is sprayed over the flue gas. The only air pollution management technology that can typically remove both gas pollutants and particulate matter is a wet scrubber. When a cleaning agent like lime or water is used, the big particles are easily caught since the dirty gases are soluble in the liquid. Although there are many different kinds of wet scrubbers, the design of Spray Towers is the focus of this paper. After tracking the air emissions with the intended parameters under varying conditions throughout time, the author of this work constructed the Spray Tower for a 100TPD cement factory using Vertical Shaft Technology (VSK). Over 95 percent of the Spray Tower's efficiency has been achieved through its design. Major Findings: It is a flexible solution in the battle against vehicle emissions because of its scalable architecture, which also permits possible uses across a range of vehicle types, from heavy-duty trucks to passenger cars. All things considered, the effective creation of such a system might greatly lessen the negative environmental effects of transportation, assisting international initiatives to lower carbon emissions and enhance air quality.

Activated carbon fiber derived from wasted coal liquefaction residual for CO2 capture

The article undertakes the very important topic of the long-term durability of concrete in a natural draft concrete cooling tower with flue gas injection. The corrosive conditions, including temperature, relative humidity, and CO2 and SO2 gas concentrations, near the inner wall of a cooling tower with flue gas injection were monitored in real time to obtain the long-term durability performance of concrete. The pH and chemical compositions of the condensed liquid that adhered to the tower’s inner face and the macromorphology, compressive strength, and neutralization depth of in situ specimens were tested periodically. In addition, a finite element numerical simulation was conducted to simulate and verify the concentration distributions of CO2 and SO2 in the flue gas in the cooling tower. The results showed that the cleaned flue gas was enveloped, diluted, and uplifted by hot vapor in the cooling tower, and its concentration decreased. Meanwhile, the effective diffusion radius increased gradually as the flue gas rose. With the same elevation in the cooling tower, the concentration of flue gas decreased rapidly from the central point to the surrounding area. The air near the inner surface of the cooling tower was merely dampened air with a low concentration of acidic gas due to the gigantic diameter of the cooling tower. As a result, the injection of cleaned flue gas will not evidently increase the corrosion risk in a natural draft concrete cooling tower.

The report de scribe s an automated system for sampling, analyzing and recording constituents of boiler flue gases. The system employs non-dispersive infrared spectrophotometers for analyzing CO2 and CO and a thermomagnetic sensor for analyzing 02. Each analyzer is supplied with a clean, dry stream of flue gas to ensure a high degree of analytical sensitivity, selectivity and accuracy. Response time between sample inlet and readout is less than 40 sec because the three analyzers require only about 2 per cent of the total sample flow. The system has been in operation for over three years and during this time it has been proved reliable, rugged and trouble-free.

The Kansai Electric Power Co., Inc. (KEPCO) and Mitsubishi Heavy Industries, Ltd. (MHI) have been developing flue gas CO_2 recovery technology in chemical absorption as a measure against global warming since 1990. New energy-efficient solvents and low pressure-loss packing were developed and the new solvents are less corrosive and cause less degradation. On the pilot plant in Osaka, evaluation of the flue gas CO_2 recovery technology and its applicability to power plant was studied as collaboration work by all utility companies in Japan, afterward KEPCO and MHI are still developing the technology continuously. CO_2 utilization technologies are also discussed because they have possibility to connect CO_2 recovery technology to quantitative CO_2 mitigation. The first flue gas CO_2 recovery commercial plant using the developed solvent is in operation in Malaysia since October 1999.

Recovery of CO 2 from power plant flue gases using amines