Carbonate looping or calcium looping (CaL) is an efficient post-combustion CO2-capture technology particularly suited for retrofitting existing power plants. Limestone, an inexpensive and highly available natural product, is utilized for the CaL process. A new concept with an indirectly heated calciner is presented, where the heat for calcination is transferred by means of heat pipes from an external combustor. This process modification offers higher plant efficiencies and lower CO2 avoidance costs than an oxy-fired CaL process. The worldwide first indirectly heated CaL pilot plant with a nominal power of 300 kWth has been erected at Technische Universitat Darmstadt. This paper presents the layout of the pilot plant and first operational results using a natural limestone as sorbent and propane as fuel for the external combustor. The calciner was fluidized with air to support self-fluidization of the sorbent during calcination and to lower the partial CO2 pressure and therewith the calcination temperature. Proof of concept was demonstrated within more than 400 h continuous testing. The reactor system showed good hydrodynamic stability, and the heat pipe heat exchanger an excellent performance. CO2 capture rates up to 90% in the carbonator were reached. (C) 2016 Elsevier Ltd. All rights reserved.

Carbonate looping promises low energy penalties for postcombustion CO2-capture and is particularly suited for retrofitting existing power plants. To further improve the process, a new concept with an indirectly heated calciner using heat pipes was developed, offering even higher plant efficiencies and lower CO2 avoidance costs than the oxy-fired standard carbonate looping process. The concept of the indirectly heated carbonate looping (IHCL) process was tested at sufficient scale in a 300 kWth pilot plant at Technische Universitat Darmstadt. The paper presents a technical overview of the process and shows first test results of the pilot plant. Furthermore, the concept is economically evaluated and compared to other carbon capture processes.

Standard carbonate looping promises low energy penalties for post-combustion CO2-capture and is particularly suited for retrofitting existing power plants. The heat for calcination can be provided by supplementary coal firing with oxygen leading to energy penalties and additional investment costs for air separation. To further increase the process efficiency, a new concept is considered where the heat for calcination is transferred from an external combustor to the calciner by means of heat pipes. This process modification offers even higher plant efficiencies and lower CO2 avoidance costs than the oxy-fired standard carbonate looping process. The concept of the indirectly heated carbonate looping process is tested at sufficient scale in a 300 kWth test facility at Technische Universität Darmstadt. The main focus of this paper is on the design and erection of the very innovative pilot plant that is currently being commissioned.

Carbonate looping is an efficient post-combustion CO2 capture technology using limestone based sorbents. A carbonate looping pilot plant consisting of two interconnected circulating fluidized bed (CFB) reactors with a thermal capacity of 1 MWth has been designed and erected at Technische Universitat Darmstadt. The pilot plant has been operated for >1500 h in fluidized bed mode, thereof >400 h with CO2 capture. The heat for the endothermic regeneration of CaO in the calciner was provided by combustion of either propane or pulverised coal with O-2 enriched air. High CO2 absorption efficiencies of up to 85% in the carbonator were achieved for long periods. Taking the CO2 produced by oxyfuel-combustion in the calciner into account, the pilot plant was operated with total CO2 capture rates above 90%. A process model for the carbonate looping pilot plant has been developed with ASPEN PLUS (TM). A 1D CFB model has been implemented in the process model to determine the effect of hydrodynamics within a fast fluidized bed on the CO2 absorption rate in the carbonator. Operating conditions of a selected test campaign where used as boundary conditions. The results of process simulations show good agreement of calculated CO2 absorption rate with experimental data. Hence, this process model can be considered as a reliable tool for scale-up of the process. (C) 2013 Elsevier Ltd. All rights reserved.

The feasibility of the post combustion process Carbonate Looping has been confirmed through operation of various test rigs at different scales worldwide. This work describes the development of a 1 MWth test rig to a 20 MWth pilot plant, shows some important and essential test results of the 1 MWth plant and presents a basic design study with a final setup of the 20 MWth pilot. The erection and operation of a pilot plant in a scale of 20 MWth is considered as a further milestone with regard to a large scale application of this technology.

Carbon capture with subsequent compression and storage is a promising possibility for the reduction of CO2 emissions from coal-fired power generation. A very efficient post-combustion CO2 capture technology is the carbonate looping process. To further increase the process efficiency, a new concept is considered where the heat for calcination is transferred from an external combustor to the calciner by means of heat pipes. Some thermodynamic evaluations for a retrofit of a coal-fired host plant with the indirectly heated carbonate looping process and cold flow model tests of a 300-kW(th) test facility that will be erected in 2013 in Darmstadt are presented.