Modeling of the oxy-combustion calciner in the post-combustion calcium looping process

The calcium looping process is a fast-developing post-combustion CO2 capture technology in which combustion flue gases are treated in two interconnected fluidized beds. CO2 is absorbed from the flue gases with calcium oxide in the carbonator operating at 650 ºC. The resulting CaCO3 product is regenerated into CaO and CO2 in the calciner producing a pure stream of CO2. In order to produce a suitable gas stream for CO2 compression, oxy-combustion of a fuel, such as coal, is required to keep the temperature of the calciner within the optimal operation range of 880-920°C. Studies have shown that the calcium looping process CO2 capture efficiencies are between 70 % and 97 %. The calciner reactor is a critical component in the calcium looping process. The operation of the calciner determines the purity of gases entering the CO2 compression. The optimal design of the calciner will lower the expenses of the calcium looping process significantly. Achieving full calcination at the lowest possible temperature reduces the cost of oxygen and fuel consumption. In this work, a 1.7 MW pilot plant calciner was studied with two modeling approaches: 3-D calciner model and 1-D process model. The 3-D model solves fundamental balance equations for a fluidized bed reactor operating under steady-state condition by applying the control volume method. In addition to the balance equations, semiempirical models are used to describe chemical reactions, solid entrainment and heat transfer to reduce computation effort. The input values of the 3-D-model were adjusted based on the 1-D-model results, in order to model the behavior of the carbonator reactor realistically. Both models indicated that the calcination is very fast in oxy-fuel conditions when the appropriate temperature conditions are met. The 3-D model was used to study the sulfur capture mechanisms in the oxy-fired calciner. As expected, very high sulfur capture efficiency was achieved. After confirming that the 1-D model with simplified descriptions for the sorbent reactions produces similar results to the more detailed 3-D model, the 1-D model was used to simulate calcium looping process with different recirculation ratios to find an optimal area where the fuel consumption is low and the capture efficiency is sufficiently high. It was confirmed that a large fraction of the solids can be recirculated to both reactors to achieve savings in fuel and oxygen consumption before the capture efficiency is affected in the pilot unit. With low recirculation ratios the temperature difference between the reactors becomes too low for the cyclic carbonation and calcination. As a general observation, the small particle size creates high solid fluxes in the calcium looping process that should be taken into account in the design of the system

Mobiilisovelluksen kehittäminen verkkotekniikoilla

Opinnäytetyön tavoitteena on kehittää mobiilisovellus ja ratkaista mobiilisovelluksen kehityksen vaiheet Android- ja iOS-laitteille siten, että opinnäytetyöraportissa käsitellään vaihtoehdot erilaisille toteutustavoille. Opinnäytetyöraportissa esitellään yleisimmät verkkotekniikat, kuten HTML5, CSS, JavaScript sekä jQuery. Tekniikoiden tarkastelussa käytetään apuna opinnäytetyön toiminnallisen osuuden tulosta eli Hygipassi-mobiilisovellusta. Opinnäytetyössä mobiilisovellus luodaan käyttämällä verkkotekniikoita. Opinnäytetyö avaa lukijalle vaihtoehtoiset ratkaisut mobiilikehitykseen ohjelmistokehysten ulkopuolelta ja esittelee hybridisovelluksen teknisen kehittämisen vaiheet. Työssä esitellään myös sovelluksessa käytetyt jQuery-lisäosat siten, että sovelluksesta otetuilla esimerkeillä lukijalle avataan, kuinka koodi vaikuttaa rakenteeseen ja tulostuu sovelluksen graafiseen käyttöliittymään. Opinnäytetyö on rajattu siten, ettei tekstissä käsitellä sovelluksen lisäämistä mobiililaitteelle tai sen julkaisua sovelluskauppoihin. Opinnäytetyön tulos on mobiililaitteessa toimiva verkkotekniikoilla kehitetty sovellus, eli hybridisovellus.The objective of this thesis was to develop a mobile application and to solve the different stages of development for Android and iOS platforms. To that the report introduces different alternatives for implementation. The thesis demonstrated the most common web technologies such as HTML5, CSS, JavaScript and jQuery. To demonstrate these technologies, the thesis included a functional part, which is a mobile application called Hygipassi. This mobile application was developed using web technologies. The thesis provides the reader with alternative solutions to mobile development outside the frameworks and presents the technical stages of developing a hybrid application. The thesis also demonstrates the jQuery plugins used in the application by including examples from the application showing the reader how the code effects the structure and is printed on the graphic interface of the application. This thesis has been outlined not to include a preview on installing or uploading the application into a mobile device, or an application marketplace. The result of this thesis is a hybrid application, which is developed with web technologies and can be used in mobile device

Modelling a Calciner with High Inlet Oxygen Concentration for a Calcium Looping Process

13th International Conference on Greenhouse Gas Control Technologies, GHGT-13, 14-18 November 2016, Lausanne, SwitzerlandA calcium looping (CaL) process is a carbon capture technology which utilizes calcium oxide to remove carbon dioxide from the flue gas of a power plant. Like most capture technologies, CaL process has a high energy demand, which reduces power plant efficiency. The energy penalty and the operating and capital costs of the unit can be reduced by increasing the concentration of O2 in the oxidant flow to calciner. In this study, a calciner has been studied with a three dimensional, steady-state, CFB process model. First, the model was validated by test data of the calciner in la Pereda CaL pilot. Next, a 3D model was created for a 200 MWth commercial scale calciner, in which the inlet oxygen concentration was increased up to 75% to map the potentials of improving the heat balance of the system and to investigate how the calciner operates in these conditions. Based on the simulations, the CaL process is feasible even at very high inlet oxygen concentration.The work presented in this paper is being partially funded by the European Commission under the RFCS “CaO2” project.Peer reviewe

Review and research needs of Ca-Looping systems modelling for post-combustion CO2 capture applications

Ca-Looping technology has experienced a substantial development in the technical readiness level in the last years, especially in its application as post-combustion CO2 capture technology in power plants. Experimental results from MW-scale power plants worldwide have confirmed post-combustion Ca-Looping process using interconnected circulating fluidised bed reactors as a promising technology for CO2 capture. Among the different fields of research having contributed to this breakthrough, modelling activity aiming at assessing sorbent properties, interpreting results from experimental reactors or assessing technology scale-up through large-scale reactors and process integration have played a crucial role.This paper aims at reviewing and discussing findings obtained by different research groups worldwide about post-combustion Ca-Looping process modelling. Assumptions made with respect to sorbent performance, reactor operating conditions and process integration between different components are crucial when evaluating the performance of the Ca-Looping process as a post-combustion technology for CO2 capture. With the aim of understanding the importance of these assumptions, this paper covers particle reaction and reactor models for carbonation and calcination steps, assessing the impact of the conditions used for their determination into their reactivity predictions, as well as process modelling works that assess performance obtained when integrating a Ca-Looping process into a power plant. Indications on the research needs detected among the reviewed works have also been highlighted in this work to contribute to the advancement of the knowledge on the Ca-Looping technology