Development of a sorbent for carbon dioxide

The reversible absorption of CO2 by CaO at high temperature is a promising method for capturing and removing CO2 from a hot gas stream. The main challenge facing the use of this method is the deterioration of CO2 absorption capacity when the method is applied over a large number of CO2 absorption/desorption cycles. Although various techniques have been proposed for improving the cyclic stability and performance of calcium based sorbents, a cost effective method is still needed for industrial applications. Therefore, two promising methods for improving the cyclic stability were selected for further investigation. One method is to optimize the preparation conditions applied to various particle sizes of CaO precursors while the second method involves incorporating an inert material, MgO, in the sorbent. While applying the first method, it was discovered that the absorption capacity and stability of a sorbent derived from limestone is dependent on many factors including the initial calcination atmosphere, temperature and time as well as particle size. It was found that both the absorption capacity and stability were greater for a sorbent derived from 11 ym limestone particles than for one derived from a much coarser material. It was also found that by calcining the 11 ym limestone at 1000oC for 1 hr in 50 vol% CO2, the resulting sorbent had an initial absorption capacity of 7 mmol CO2/g sorbent which only declined to 6.3 mmol CO2/g sorbent over 80 cycles of CO2 absorption/regeneration. A sorbent prepared by calcining calcium acetate at 1000oC for 1 hr in an atmosphere containing from 50 to 100% CO2 exhibited the highest absorption capacity among the materials tested. It was also reasonably stable over 40 cycles tested. One of the most promising sorbents was prepared from plaster of Paris (calcium sulphate hemihydrate) by treating the material with a cyclic oxidation/reduction process at 1070oC. This sorbent exhibited an increasing trend in absorption capacity throughout a 200 cycle test of CO2 absorption and desorption. For the second method for improving the cyclic stability of the sorbent, small amounts of MgO were incorporated in a sorbent as an inert diluent and structural stabilizer. It appeared that addition of MgO improved the performance of the sorbent in some cases depending on both the source of MgO and calcination conditions. However, this method did not seem to offer an advantage over the use of dolomite (calcium magnesium carbonate) alone, especially when the particle size of the dolomite was reduced by grinding so that it was more nearly comparable to that of the 11 ym limestone. A sorbent prepared by calcining the ground dolomite at 1000oC for 1 hr in N2 had an absorption capacity in excess of 8 mmol CO2/g sorbent over 80 cycles of CO2 absorption/desorption

Techno-economic study of the calcium looping process for CO2 capture from cement and biomass power plants

The first detailed systematic investigation of a cement plant with various carbon capture technologies has been performed. The calcium looping (Ca-looping) process has emerged as a leading option for this purpose, since this process applied to a cement plant provides an opportunity to use the CaO purge for clinker production. The Ca-looping process is comprised of two interconnected reactors where the carbonator captures CO2 from flue gases and the calciner regenerates the CaCO3 into CaO by oxy-combustion. Fully integrated process flowsheets have been developed and simulated in UniSim Design Suite from Honeywell. The detailed carbonator model has been implemented using Matlab and incorporated into UniSim to provide a full flowsheet simulation for an exemplary dry-feed cement plant as a user-defined operation. The base cement plant simulation was also modified to integrate three different carbon capture processes: membrane; indirect calcination; and amine-scrubbing. Furthermore, an advanced configuration of Ca-looping process has been investigated where the energy intensive air separation unit was replaced with a chemical looping combustion (CLC) cycle. Each case has been optimised to minimise its energy consumption and compared in terms of levelised cost of cement and its resulting cost of CO2 avoided at the same CO2 avoidance rate. The proposed integration of the Ca-looping process is capable of achieving over 90% CO2 avoidance with additional fuel consumption of 2.5 to 3.0 GJth/ton CO2 avoided. By using an advanced configuration of the Ca-looping process with a CLC cycle, the additional fuel consumption can be reduced to 1.7 GJth/ton CO2 avoided, but the cost of the oxygen carrier is the major concern for this system. Among the other CO2 capture options, the membrane process is a promising alternative for the Ca-looping process since it has a potential of achieving the target CO2 avoidance rate and purity requiring lower energy consumption. The indirect calcination process provides moderate levels of CO2 avoidance (up to 56%) without a need of an external capture process whereas the integration of the amine process in a cement plant is challenging as a result of the requirement of steam for solvent regeneration. Furthermore, considering zero net CO2 emissions associated with biomass combustion systems, a novel concept has been analysed to capture of CO2 in-situ with the Ca-looping process while operating the combustor of a dedicated biomass power plant at sufficiently low temperature. This process is capable of achieving 84% overall CO2 capture rate with an energy penalty of 5.2% when a proper heat exchanger network is designed with the support of a pinch analysis. The techno-economic performance of the biomass power plant with in-situ Ca-looping CO2 capture process was compared with that of the alternative biomass-air-fired and biomass-oxy-fired power plants

A Hybrid Carbon Capture System of Indirect Calcination and Amine Absorption for a Cement Plant

AbstractHere we present the process integration of the indirect calcination process existing in the literature [1] into a cement plant. The indirect calcination process is composed of a circulating fluidized bed combustor and a fluidized bed calciner where hot solid particles are circulated between those reactors for heat transfer. It allows separation of CO2 from limestone calcination in a concentrated form. The process integration proposed in this study minimizes the total thermal energy requirement by using excess energy from high temperature flue gases for cement raw meal preheating as in the conventional cement manufacturing process. It also suggests a new hybrid carbon capture system where an additional CO2 capture unit is combined with the indirect calcination process, since the standalone indirect calcination application can only provide a moderate level of CO2 avoidance. The amine process is added to increase CO2 avoidance rate further. Full process flowsheets have been developed and analyzed using the commercial software UniSim Design R400 from Honeywell. The hybrid system can achieve more than 90% carbon capture rate thanks to the supplementary amine process while the indirect calcination can capture only 56% without the amine process. With the support of a simple and transparent economic analysis, the capture cost involved in the hybrid system was estimated to be higher than that of the indirect calcination only but significantly lower than that of the standalone amine process on a basis of unit CO2 avoided

Novel Strategy to Produce Ultrapure Hydrogen from Coal with Pre-combustion Carbon Capture

AbstractIntegrated Gasification Combined Cycles (IGCCs) are one of the emerging clean coal technologies which paves the way for producing power from coal with a higher net power efficiency than conventional PC-fired boiler power plants. It is also advantageous that in an IGCC power plant a carbon capture unit can be applied to a stream having a very high CO2 partial pressure upstream of gas combustion that would not be available in case of a PC-fired boiler power plant, leading to less energy penalty involved in the carbon capture. In this study it is aimed to design a cogeneration process where a Hydrogen Pressure Swing Adsorption (H2 PSA) unit is retrofitted to an IGCC power plant with pre-combustion capture for producing ultrapure hydrogen (99.99+ vol%). The ultrapure hydrogen is commonly utilised as feedstock for deep desulphurisation and hydrocracking units at refineries as well as H2 fuel cells. It is found that, at the same H2 purity of 99.99+%, the hydrogen recovery could be improved up to 93% with the increasing number of columns. Improving the H2 recovery at the H2 PSA to its maximum can contribute to reducing the power consumption for compressing the H2 PSA tail gas by minimizing the yield of the H2 PSA tail gas by-product. Furthermore, it is demonstrated that the H2 PSA can also be designed to achieve 90% H2 recovery even when a portion of the tail gas is recycled to the shift reactors in order to improve the overall advanced IGCC performance by increasing the H2 yield and by reducing the auxiliary power consumption at carbon capture unit

Process simulation of Ca-looping processes: review and guidelines☆

Abstract Ca-looping is one of the most promising processes for CO 2 capture in short to medium term plants, which can be applied for both post-combustion and pre-combustion layouts. The recent successful operations of MW-scale pilot plants are leading to an increased interest in this technology. In addition, the particularly advantageous applicability in cement plants, the main industrial contributors to CO 2 emissions worldwide, can further lead to a forthcoming development of the technology. Quite a large amount of scientific papers on reactors and process modeling has been published in the recent years and more studies are expected to be published in the future. According to the experience of the authors in this field and on the basis of a literature review, suggestions and modeling needs for next works are provided in this paper

Ca–Cu looping process for CO2 capture from a power plant and its comparison with Ca-looping, oxy-combustion and amine-based CO2 capture processes

Carbon capture for fossil fuel power generation draws an increasing attention because of significant challenges of global climate change. This study aims to explore the integration of a 453 MWe natural gas combined cycle (NGCC) power plant with an MEA-based post-combustion carbon capture (PCC) process and CO₂ compression train. The steady state models of the NGCC power plant, the PCC process and compression train were developed using Aspen Plus® and were validated with the published data and experimental data. The interfaces between NGCC and PCC were discussed. Exhaust gas recirculation (EGR) was also investigated. With EGR, a great size reduction of the absorber and the stripper was achieved. An advanced supersonic shock wave compressor was adopted for the CO₂ compression and its heat integration was studied. The case study shows net efficiency based on low heating value (LHV) decreases from 58.74% to 49.76% when the NGCC power plant is integrated with the PCC process and compression. Addition of EGR improves the net efficiency to 49.93% and two compression heat integration options help to improve the net efficiency to 50.25% and 50.47% respectively. This study indicates NGCC including EGR integrated with PCC and supersonic shock wave compression with new heat integration opportunity would be the future direction of carbon capture deployment for NGCC power plant

Comparison of the clinical parameters of benign prostate hyperplasia in diabetic and non diabetic patients

Objective: We evaluated the correlation between benign prostate hyperplasia (BPH) measures and diabetes mellitus in men with benign prostate hyperplasia in a prospective study. Materials and methods: Between 2008-2012, 100 diabetic and 200 non diabetic patients undergoing surgery due to benign prostate hyperplasia were enrolled in the study. The parameters evaluated for each patients included prostate volume, fasting blood glucose, HbA1c, total testosterone, total prostatic specific antigen (T-PSA), triglicerides, total cholesterol and body mass index (BMI). A questionnaire including international prostate symptom score (IPSS) was sdministered and uroflow test measuring the peak urinary flow rate was performed to appreciate the complaints of the patients objectively. Results: Diabetic patients are more likely to have larger prostate volume. The symptom score evaluated by IPSS and post micturition residual volume were also significantly higher in diabetic groups. The other statistically significant different parameter between two groups was total testosterone that diabetic patients tend to have lower levels. Diabetic counterparts were established to have higher BMI. No statistically significant differentiation was observed about trigliceryde and total cholesterol levels and uroflow rates. Conclusions: Our study suggests a positive correlation between high prostate volume and diagnosis of diabetes mellitus in patients with benign prostatic hyperplasia. We also observed a positive correlation between symptom scores and post micturion residual volumes and diagnosis of diabetes mellitus suggesting that the presence of diabetes is related to both static and dynamic components of benign prostate hyperplasia. Additionally testosterone levels were lower in diabetic patients. Further studies need to confirm these relationship in a larger population

Palliative treatment of coronary “atherosclerotic cancer” by drug-eluting or bare-metal stents: From oculo-stenotic reflex period to age of precision medicine

Medications and treatments are said to have a palliative effect if they relieve symptoms without having a curative effect on the underlying disease such as atherosclerosis or cancer. Some authors speculated that atherosclerotic coronary artery disease (CAD) could be considered a “cancer of the coronary arterial wall”. Although the percutaneous coronary intervention (PCI) has proven to be effective in decreasing mortality rates among patients with acute coronary syndromes, the previous meta-analyses of PCI versus optimal medical therapy for stable CAD have not been able to demonstrate a reduction in major adverse cardiac outcomes. However, few cardiologists discussed the evidence-based benefits of angiogram and PCI for stable CAD, and some implicitly or explicitly overstated the benefits. Recently, the precision medicine is defined as an evidence-based approach that uses innovative tools and biological and data science to customize disease prevention, detection, and treatment, and improve the effectiveness and quality of patient care. Providing patients with accurate and complete information appears to be an effective way to combat the reliance on the oculostenotic reflex. The foundation of precision medicine is the ability to tailor therapy based upon the expected risks and benefits of treatment for each individual patient. As said by Doctor William Osler, “The good physician treats the disease; the great physician treats the patient who has the disease.