A novel reactor configuration for packed bed chemical-looping combustion of syngas

Abstract

This study reports on the application of chemical looping combustion (CLC) in pressurized packed bed reactors using syngas as a fuel. High pressure operation of CLC in packed bed has a different set of challenges in terms of material properties, cycle and reactor design compared to fluidized bed operation. However, high pressure operation allows the use of inherently more efficient power cycles than low pressure fluidized bed solutions. This paper quantifies the challenges in high pressure operation and introduces a novel reactor concept with which those challenges can be addressed. Continuous cyclic operation of a packed bed CLC system is simulated in a 1D numerical reactor model. Importantly, it is demonstrated that the temperature profiles that can occur in a packed bed reactor as a result of the different process steps do not accumulate, and have a negligible effect on the overall performance of the system. Moreover, it has been shown that an even higher energy efficiency can be achieved by feeding the syngas from the opposite direction during the reduction step (i.e. countercurrent operation). Unfortunately, in this configuration mode, more severe temperature fluctuations occur in the reactor exhaust, which is disadvantageous for the operation of a downstream gas turbine. Finally, a novel reactor configuration is introduced in which the desired temperature rise for obtained hot pressured air suitable for a gas turbine is obtained by carrying out the process with two packed bed reactor in series (twostage CLC). This is shown to be a good alternative to the single bed configuration, and has the added advantage of decreasing the demands on both the oxygen carrier and the reactor materials and design specification.

Experimental Demonstration of Two-Stage Packed Bed Chemical-Looping Combustion Using Syngas with CuO/Al2O3 and NiO/CaAl2O4 as Oxygen Carriers

“…For this reason, Hamers et al investigated a system with two packed beds in series, the so-called two-stage CLC (TS-CLC) process. 6 The principle of the TS-CLC configuration is that the second bed is heated by the heat produced in the first bed. This makes it possible to divide the total temperature increase over two beds and reduces the demands on the oxygen carriers and reactor materials.…”

Energy analysis of two stage packed-bed chemical looping combustion configurations for integrated gasification combined cycles

“…For the case of the one stage CLC, a 19 wt% NiO/Al 2 O 3 was selected as oxygen carrier, because this is currently the only feasible oxygen carrier in a packed bed, if the reduction is carried out at low temperature [13]. In the TS-CLC cases, the first reactor contains CuO/Al 2 O 3 and the second reactor Mn 3 O 4 /Al 2 O 3 .…”

“…Considering the most studied oxygen carriers, only nickel oxide and ilmenite could be applied to achieve such DT, but both have some important drawbacks. Nickel is an expensive and toxic material [13], while ilmenite has a low reactivity at low temperatures [14]. The low reactivity of ilmenite can be circumvented by carrying out the reduction just after the oxidation when the bed is at high temperature and then performing the heat removal on the reduced bed by means of a N 2 stream [14].…”

“…To reduce the demands on the oxygen carriers and achieve the same overall DT, the novel Two Stage Chemical Looping Combustion (TS-CLC) configuration has been proposed in a previous work [13], where the heat is produced via two packed beds placed in series. A schematic overview of this configuration is shown in Fig.…”

“…1. Hence, CO 2 and H 2 O are produced at higher temperature and a slightly lower quantity of hot air is produced for the gas turbine [13]. This could affect the overall electrical efficiency and a more detailed energy analysis of the complete system is required to assess the energy efficiency of this system, which is the focus of the present paper.…”