Waste tyre pyrolysis: modelling of a moving bed reactor

This paper describes the development of a new model for waste tyre pyrolysis in a moving bed reactor. This model comprises three different sub-models: a kinetic sub-model that predicts solid conversion in terms of reaction time and temperature, a heat transfer sub-model that calculates the temperature profile inside the particle and the energy flux from the surroundings to the tyre particles and, finally, a hydrodynamic model that predicts the solid flow pattern inside the reactor. These three sub-models have been integrated in order to develop a comprehensive reactor model. Experimental results were obtained in a continuous moving bed reactor and used to validate model predictions, with good approximation achieved between the experimental and simulated results. In addition, a parametric study of the model was carried out, which showed that tyre particle heating is clearly faster than average particle residence time inside the reactor. Therefore, this fast particle heating together with fast reaction kinetics enables total solid conversion to be achieved in this system in accordance with the predictive model.

New CO2 capture process for hydrogen production combining Ca and Cu chemical loops

This paper presents a new solids looping process for capturing CO2 while generating hydrogen and/or electricity from natural gas. The process is based on the sorption enhanced reforming of CH4, employing CaO as a high temperature CO2 sorbent, combined with a second chemical loop of CuO/Cu. The exothermic reduction of CuO with CH4 is used to obtain the heat necessary for the decomposition of the CaCO3 formed in the reforming step. The main part of the process is completed by the oxidation of Cu to CuO, which is carried out with air diluted with a product gas recycle of this reactor at sufficiently low temperatures and high pressures to avoid the decomposition of a substantial fraction of CaCO3.

Procedural results of coronary angioplasty but not late mortality have improved in patients with depressed left ventricular function

BACKGROUND

Published experience with coronary angioplasty in patients with severely depressed left ventricular (LV) ejection fraction indicates that procedural complications are more frequent in such patients than in those with normal or near normal LV function. Although the immediate outcomes of transcatheter revascularization in unselected populations have improved substantially since the procedures upon which these reports were based were performed, outcomes with this subset of patients has not been recently reviewed.

HYPOTHESIS

This study was undertaken to document the results of the application of current transcatheter technology to this patient subset.

METHODS

We analyzed data from 194 consecutive patients with a visually estimated LV ejection fraction < 30%, who underwent coronary angioplasty in this institution between January 1, 1995, and April 30, 1996, and compared their outcomes with those of 1,390 patients with normal LV function treated concurrently.

RESULTS

Angiographic success in the two groups was similar. The hospital mortality of the patients with low ejection fraction was higher (2.6 vs. 0.6%, p = 0.02) than in concurrently treated patients with normal LV function. Other procedural complications were no more frequent than in such patients. Late mortality in patients with low ejection fraction was 16%, a similar value to that in older reports.

CONCLUSION

Compared with older reports, current hospital outcomes of coronary angioplasty are improved in patients with severely depressed LV function. Unfortunately, late outcomes are not demonstrably better.

Process for capturing CO2 arising from the calcination of the CaCO3 used in cement manufacture

This paper outlines a new CaCO3 calcination method for producing a stream of CO2 (suitable for permanent geological storage after purification and compression). The process is based on the use of very hot CaO particles (T >1000 degrees C) to transfer heat from a circulating fluidized bed combustor (CFBC) to a calciner (fluidized with CO2 and/or steam). Since the fluidized bed combustor and calciner have separate atmospheres, the CO2 resulting from the decomposition of CaCO3 can be captured, while the CO2 generated in the combustion of the fuel in air is emitted to the atmosphere. We demonstrate that with this system it is possible to reduce the CO2 emissions of a cement plant by around 60%. Furthermore, since the key pieces of equipment are similar to the commercial CFBCs used in power generation plants, it is possible to establish the additional investment required for the system and to estimate the cost per ton of CO2 avoided for this process to be about 19 $/tCO2 avoided.

Cost structure of a postcombustion CO2 capture system using CaO

This paper presents the basic economics of an emerging concept for CO2 capture from flue gases in power plants. The complete system includes three key cost components: a full combustion power plant, a second power plant working as an oxy-fired fluidized bed calciner, and a fluidized bed carbonator interconnected with the calciner and capturing CO2 from the combustion power plant. The simplicity in the economic analysis is possible because the key cost data for the two major first components are well established in the open literature. It is shown that there is clear scope for a breakthrough in capture cost to around 15 $/t of CO2 avoided with this system. This is mainly because the capture system is generating additional power (from the additional coal fed to the calciner) and because the avoided CO2 comes from the capture of the CO2 generated by the coal fed to the calciner and the CO2 captured (as CaCO3) from the flue gases of the existing power plant, that is also released in the calciner.