Two-Stage Chemical Absorption–Biological Reduction System for NO Removal: System Start-up and Optimal Operation Mode

Abstract

A novel chemical absorption–biological reduction (CABR) integrated process, employing Fe­(II)­EDTA as an enhanced absorbent, is a promising technology for nitrogen oxides removal. In this work, we developed a new two-stage CABR system applying a mixed cultivation model of denitrifying bacteria and iron-reducing bacteria, which consists of a sieve-plate tower and a bioreduction tower to separate the absorption and reduction processes. The start-up period of the two-stage system was shortened to 19 days, while that of the one-stage CABR system was 46 days. In addition, the two-stage CABR system featured a better oxygen-resistance ability and a higher NO removal loading. In effort to optimize system operation, we compared different modes of system operation and found that (1) continuous addition of glucose was better than the batch-type addition and that (2) the NO removal efficiency could be maintained at >90% while the FeEDTA concentration was higher than 4 mmol/L; however, reducing the initial concentration of ferric iron complex could inhibit the loss rate of Na2EDTA. Furthermore, the optimized operating mode parameters were 4 mmol/L initial Fe­(III)­EDTA, 0.6 mg/min Na2EDTA, and 5 mg/min glucose with a 2 L/min gas flow rate under a 400 ppm of NO condition, while the NO removal efficiency was kept >90%; the corresponding operating cost in terms of glucose was 8.4 g of glucose/g of NO. The purpose of this work was to provide preliminary data to support future industrial application for NO x removal, as well as sufficient technological insights on the process configuration and reactor operation of the two-stage CABR system.

Performance and Microbial Community Analysis of an Electrobiofilm Reactor Enhanced by Ferrous-EDTA

“…For decades, the main anthropogenic source of NO x has been emissions from industrial boilers (kilns). , Some technologies have been introduced for controlling flue gas from boilers (kilns) and reducing the release of NO x , such as selective catalytic reduction (SCR), low-NO x burners, absorption, adsorption, and selective noncatalytic reduction (SNCR). , However, these methods can have a high cost, low removal efficiency, and cause secondary pollution . The biological treatment of industrial flue gas for NO x removal was proposed in the 1980s as a low-cost and environmentally sustainable approach, and related studies have focused mainly on isolating denitrifying bacteria and improving biological reactors. , Wang et al studied denitrifying bacteria in bioreactors for landfill leachate treatment and found that the main bacteria in the bioreactor varied with changes in the hydraulic loading.…”

“…Xing et al studied the microorganisms involved in the micro-electrolysis and autotrophic denitrification processes by high-throughput sequencing and found that β-, γ-, and α- Proteobacteria were the dominant genera. However, biological approaches have been limited by their low efficiency, which is caused by the low solubility of NO in liquid and the higher proportion of NO in NO x from flue gas. , Therefore, a new integrated technology has been developed that combines complex absorption processes with biological reduction. , Ferrous ethylenediaminetetraacetic acid (EDTA-Fe II ) had been reported to rapidly form complexes with NO, which resolves the issues associated with the low gas–liquid mass transfer efficiency of NO . An electrobiofilm was subsequently introduced and has been demonstrated to further strengthen the regeneration rate of EDTA-Fe II , as it not only forms complexes with NO to generate EDTA-Fe II -NO but also oxidizes into EDTA-Fe III by oxygen in the flue gas (approximately 9% content in the flue gas in industrial boilers) …”

“…For decades, the main anthropogenic source of NO x has been emissions from industrial boilers (kilns). 5,6 Some technologies have been introduced for controlling flue gas from boilers (kilns) and reducing the release of NO x , such as selective catalytic reduction (SCR), low-NO x burners, absorption, adsorption, and selective noncatalytic reduction (SNCR). 7,8 However, these methods can have a high cost, low removal efficiency, and cause secondary pollution.…”

Effects of cobalt-histidine absorbent on aerobic denitrification by Paracoccus versutus LYM

“…As a cost-effective and eco-friendly process for nitric oxide (NO) removal, the chemical absorption-biological reduction (CABR) flue gas denitrification technology is based on wet absorption of NO using ferrous complexes, especially ferrous ethylenediaminetetraacetate [Fe(II)EDTA], to improve the NO absorption into scrubbing liquid, and biological reduction regeneration of chelate agent to reduce operation costs (Zhang et al 2014, 2018; Zhao et al 2016). However, typical flue gas after the traditional flue gas desulfurization process is estimated to contain 3–8% (v/v) O 2 (Zhang et al 2008).…”

Experimental Investigation and Process Simulation of Oxy-fuel Flue Gas Denitrification in CO2 Compression Process

“…Currently, selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are conventional technologies for postcombustion NO x control, and several novel solid or liquid sorbents and catalysts have been developed for NO x reduction. − Assuming that the emission of NO x from oxy-fuel flue gas is controlled using traditional SCR or SNCR technology, this will add to the investment and operation costs because an additional flue gas denitrification device is required in an oxy-fuel plant. There is the possibility of using the existing CO 2 compression and purification units (CPUs) as a cleaning step for NO x removal instead of the traditional flue gas denitrification device.…”