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[Display omitted] • A novel coal-fired power plant coupling with waste incineration scheme is proposed. • The PCDD/Fs emission could be suppressed by a three stages controlling method. • The flue gas circulation can also suppress the emission of PCDD/Fs effectively. The production of organic solid waste is increasing as the development of society. However, the investment of waste incineration power plant is very high and the thermal efficiency is very low. At the same time, the load of coal-fired power plant is suppressed due to the carbon neutralization policy. Therefore, using the existed coal-fired power plant to co-process the organic solid waste is a feasible method. In this paper, a coal-fired power plant indirect coupling with waste incineration technology based on flue gas circulation was proposed and studied on a 100 kW pilot-test bench. In this technology, the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) was reduced by a three stages controlling method, which adopts the blending of multi-source organic wastes, high-temperature decomposition and selective catalytic reduction (SCR) catalyst decomposition, simultaneously. The effects of waste incineration coupling, replacement ratio of coal, and flue gas circulation on the combustion and pollutant emission characteristics of the system were studied. The experimental results indicate that the waste incineration coupling has minor influence on the temperature distribution and the toxicity of fly ash of the coal-fired furnace. The NO, HCl, and PCDD/Fs concentrations of flue gas of coal-fired furnace generally decrease as the replacement ratio of coal increases, while the SO 2 concentration increases. With the help of three stages controlling method or the flue gas circulation, the PCDDFs concentration of the flue gas of coal-fired furnace can be much lower than 0.1 TEQ ng/Nm3. [ABSTRACT FROM AUTHOR]

• The NO emission characteristics of co-combustion of pulverized coal and NH 3 at O 2 /N 2 and O 2 /CO 2 atmospheres were studied. • The effects of temperature, NH 3 blending ratio and combustion atmosphere on NO emission during co-combustion were investigated. • The molecular dynamics simulation was used to study the migration pathways of N in NH 3. The use of ammonia as a co-combustion fuel instead of fossil fuel combustion is an important way to reduce carbon emissions from coal-fired power plants. This paper investigates the NO emission characteristics of coal/NH 3 co-combustion at O 2 /N 2 and O 2 /CO 2 atmospheres through experiments and molecular dynamics studies. The results demonstrate that increasing the combustion temperature enhances the formation of NO with the NH 3 blending ratio is 0–60 %. When coal and NH 3 are burned together, the emission of NO is lower at O 2 /CO 2 atmosphere compared to that at O 2 /N 2 atmosphere. Reactive force field molecular dynamics (ReaxFF MD) simulation results show that the effect of high concentration of CO 2 on nitrogen conversion is mainly related to temperature. When the temperature is low, the physical characteristics of CO 2 with large specific heat capacity inhibits the conversion of NH 3 to NO. However, at high temperature, CO 2 participates in the reaction in large amounts, which increases the number of OH radicals in the combustion process and promotes the conversion of NH 3 to NO. The results show that with the increase of combustion temperature, the conversion of nitrogen-containing intermediates to NO is promoted. Furthermore, the reactive molecular dynamics simulation revealed the transfer pathway of N atoms in NH 3 during co-combustion process at two atmospheres. [ABSTRACT FROM AUTHOR]

• Studied the effects of NH 3 cofiring ratio, injection mode and OFA on NO x emission. • NO x exhibited a variety of trends under different injection modes and OFA rates. • Revealed all the different NO x trends are governed by the same NO mechanism. • Found air-staging is not always effective in the NO x reduction of NH 3 cofiring. Ammonia (NH 3) cofiring is a promising approach to reduce the CO 2 emissions from coal-fired power plants. However, the potential drastic increase of NO x emissions may inhibit the wide implementation of NH 3 cofiring. To explore the potential NO x control strategies, the effects of NH 3 cofiring ratio (R N H 3 ), NH 3 injection mode and overfire air (OFA) rates on the NO x emission characteristics of NH 3 /coal cofiring are studied in a test furnace that allow for flexible control of the injection positions and combustion environment of NH 3. The results show that when NH 3 is injected with coal stream (top mixing mode), the NO x emissions increase and then decrease with the increase of R N H 3 under all OFA rates. However, when NH 3 is fed through the side port of furnace separately (side mixing mode), the NO x emissions exhibit distinct trends under different OFA rates. Under lower OFA rates, the NO x emissions show monotonical decrease with the increase of R N H 3 , while under higher OFA rates the NO x emissions first decrease and then increase with the increase of R N H 3 . Consequently, higher OFA rates could produce higher NO x emissions than lower OFA rates. This indicates that air-staging is not always effective in the NO x reduction of NH 3 cofiring. Thus, although the side mixing mode of NH 3 cofiring exhibits overall better performance in NO x control, caution is needed to accommodate the OFA rate with NH 3 cofiring ratio. Although a variety of trends of NO x emissions were observed in this study, the results demonstrate that all these trends are in fact governed by the same mechanism – the competition between the NO-formation and NO-reduction reactions of NH 3 in the varying O 2 environment in the furnace. By creating appropriate O 2 environment in the furnace, the NO x emissions of NH 3 /coal cofiring could be substantially lower than that of pure coal combustion. The findings of these paper are instrumental in the design and operation of NH 3 cofiring system in full scale coal-fired boilers to achieve effective NO x control. [ABSTRACT FROM AUTHOR]