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Pressurized oxy-fuel combustion is a solution to achieve low-cost CO 2 capture and higher operating efficiency. The combination of pressurized oxy-fuel combustion technology and biomass combustion technology can achieve negative CO 2 emissions. However, pressurized oxy-fuel co-combustion of coal and biomass lacks mechanism understanding and the studies on pollutant emissions are scarce. To investigate SO 2 emission concentration, the conversion rate of fuel sulfur to SO 2 , sulfur mass balance, and sulfur content and forms in the fuel ash of pressurized oxy-fuel co-combustion of coal and biomass, a series of cocombustion experiments were carried out in a horizontal tube furnace. The experimental fuels were lignite and corn straw, and the experimental parameters were biomass blending ratio (M b = 0, 30, 50, 70, and 100%), combustion atmosphere (air, Oxy-21, Oxy-30, and Oxy-40), reaction pressure (0.1, 0.3, 0.5, and 0.7 MPa), and combustion temperature (800, 850, and 900 °C). The experimental results showed that SO 2 actual emissions decreased as M b increased while the conversion rate of fuel sulfur to SO 2 was lowest at 50% M b . Ash analysis indicated that more sulfur converted to CaSO 4 at 50% M b . SO 2 actual emissions was highest in the air atmosphere and lowest in the Oxy-21 atmosphere. Higher reaction pressure suppressed SO 2 actual emissions and promoted the sulfur converted to other forms of sulfide, and reaction pressure had no obvious effect on CaSO 4 and K 2 SO 4 in the fuel ash. Higher combustion temperature slightly promoted SO 2 actual emissions and conversion rate of fuel sulfur to SO 2 . Except for 100% M b , the three slagging indexes for all combustion experiments were in the criteria of low slagging trend. According to T-A, slagging caused by alkali metals may occur during 100% M b combustion.

The cofiring of coal and biomass waste is an important technological direction in oxy-fuel combustion for both CO2 capture and waste disposal. The emission of pollutants during cofiring in an oxy-fuel-fluidized bed is a complex process, and practical knowledge of this process is still very limited. In this work, experimental studies on the emission of gaseous pollutants in a 10 kWth oxy-fuel-fluidized bed (combustion temperatures T1 = 800 and 850 °C and inlet O2 concentration = 30%) were carried out. The effects of the biomass blending mass ratio (M b = 0, 10, 20, 30, 50, 70, and 100%), fuel property (fuel volatility and fuel O/N, Ca/S, and K2/S molar ratios), and excess oxygen ratio (α = 1.10, 1.25, and 1.40) on gaseous pollutants CO, CH4, NO, NOx (including NO and NO2), N2O, and SO2 were systematically investigated. The results show that both CO and CH4 increase with increasing M b, and an increase in α leads to a significant decrease in CO and a slight change in CH4. The emissions of NO and NOx decrease with increasing M b because of the dilution of fuel-N and the enhancement of reduction reactions. The generation rate of N2O is much higher than that of NOx, and it decreases with increasing M b. The total conversion rate of fuel-N to nitrogen oxides is lower than 50% when cofiring coal and biomass, which is promoted by α but not by M b. In addition, the ratio of the NOx generation rate to the N2O generation rate is larger at higher fuel O/N molar ratios, and the NOx emissions per unit calorific value decrease rapidly as the fuel volatility increases. Furthermore, the SO2 emissions per unit calorific value decrease with increasing M b and Ca/S and K2/S molar ratios in fuel. An increase in α promotes the generation and emission of SO2.

The carbon trading mechanism is proposed to remit global warming and it can be considered in a microgrid. There is a lack of continuous-time methods in a microgrid, so a continuous-time model is proposed and solved by differential evolution (DE) in this work. This research aims to create effective methods to obtain some useful results in a microgrid. Batteries, microturbines, and the exchange with the main grid are considered. Considering carbon trading, the objective function is the sum of a quadratic function and an absolute value function. In addition, a composite electricity price model has been put forward to conclude the common kinds of electricity prices. DE is utilized to solve the constrained optimization problems (COPs) proposed in this paper. A modified DE is raised in this work, which uses multiple mutation and selection strategies. In the case study, the proposed algorithm is compared with the other seven algorithms and the outperforming one is selected to compare two different types of electricity prices. The results show the proposed algorithm performs best. The Wilcoxon Signed Rank Test is also used to verify its significant superiority. The other result is that time-of-use pricing (ToUP) is economic in the off-peak period while inclining block rates (IBRs) are economic in the peak and shoulder periods. The composite electricity price model can be applied in social production and life. In addition, the proposed algorithm puts forward a new variety of DE and enriches the theory of DE.

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