In-Furnace Control of Arsenic Vapor Emissions Using Kaolinite during Low-Rank Coal Combustion: Influence of Gaseous Sodium Compounds

Abstract

Using additives in the in-furnace control of arsenic emissions is promising for reducing the impact on the downstream selective catalytic reduction system and blocking the spread of arsenic pollutants into the environment. The study quantifies the arsenic adsorption capacity of kaolinite at high temperature and clarifies its fixation pathway with and without the existence of sodium vapor, which is easily adsorbed by kaolinite. Experiments about Al-coordination and acid sites of products, as well as calculations of thermodynamic equilibrium and the adsorption energy based on density functional theory were performed. During separated arsenic adsorption, nearly 40% of trivalent arsenic [As­(III)] is oxidized to pentavalent arsenic [As­(V)] and bonded to kaolinite, forming an As–O–Al structure. In this respect, the arsenic adsorption capacity of kaolinite is 200 μg g–1, with 24% of arsenic shown to be well-crystallized Al-bound. During the co-adsorption process, 82% of As­(III) is oxidized to As­(V) and connected to the Al surface of kaolinite, and the O–Na groups bond to As around the As–O–Al structure, thereby forming Na–O–As–O–Al. The arsenic adsorption capacity increased to 878 μg g–1 with well-crystallized Al-bound arsenic accounting for 56%. This study demonstrates the potential for the application of kaolinite as an arsenic adsorbent in the actual furnace.

In-Furnace Control of Arsenic Vapor Emissions Using Fe2O3 Microspheres with Good Sintering Resistance

“…This fact indicated that the designed hollow spherical structure could markedly improve the capture of Fe 2 O 3 for arsenic in the temperature region. Furthermore, the amount of arsenic captured by Fe 2 O 3 microspheres at 1300 °C was still comparable to those of CaO, kaolin, and Ca­(OH) 2 at 300–600 °C. ,− Thus, it can be inferred that Fe 2 O 3 hollow microspheres are suitable for arsenic capture at high temperatures.…”

A Critical Review on Removal of Gaseous Pollutants Using Sulfate Radical-based Advanced Oxidation Technologies

“…In the past few decades, many gaseous pollutants control technologies have been developed. In these technologies, wet flue gas desulfurization (WFGD) and selective catalytic reduction (SCR) denitration are the two most widely used SO 2 and NO x removal technologies. − Activated carbon adsorption is the main removal technology of heavy metals, Hg and As, from gas stream. − Alcohol amine absorption and catalytic oxidation are the most widely used treatment technologies of gaseous H 2 S. − The mainstream removal technologies of VOCs are rich due to huge types of VOCs and their different characteristics. Adsorption, absorption, condensation, and catalytic combustion are the common VOCs removal technologies. − Supporting Information (SI) Figure S1 shows the classification of these gaseous pollutants common removal technologies.…”

Insight into High Temperature Gas-Phase Arsenic Capture by a CaO–Ca12Al14O33 Synthetic Sorbent

“…1 Coal combustion is widely regarded as the main source of anthropogenic arsenic emission, which receives great environmental attention. 2,3 Due to the domestic enormous coal consumption, 4 the government has taken positive and stringent measures to control arsenic discharged from coal combustion in recent years, and the total amounts of atmospheric arsenic emission by coal-fired power plants were expected to reduce to 215.57 tons in 2020. 5,6 Arsenic mainly evaporates in the form of As 2 O 3 (g) during coal combustion 7−9 and tends to condense on fine-grained particles with a decrease in the flue gas temperature, 10,11 which is difficultly captured by cyclone separators, dust collectors, and other air pollution control devices.…”

“…As a volatile hazardous trace element, arsenic has attracted much attention due to its extreme toxicity to human health . Coal combustion is widely regarded as the main source of anthropogenic arsenic emission, which receives great environmental attention. , Due to the domestic enormous coal consumption, the government has taken positive and stringent measures to control arsenic discharged from coal combustion in recent years, and the total amounts of atmospheric arsenic emission by coal-fired power plants were expected to reduce to 215.57 tons in 2020. , Arsenic mainly evaporates in the form of As 2 O 3 (g) during coal combustion − and tends to condense on fine-grained particles with a decrease in the flue gas temperature, , which is difficultly captured by cyclone separators, dust collectors, and other air pollution control devices. Accordingly, it is essential to further develop arsenic removal technology, which aims to convert As 3+ vapor into less toxic As 5+ arsenate at high temperature and enrich in coarse particles as much as possible for subsequent removal by dedusting devices.…”