A field test of paper mill sludge and coal co-firing was conducted on a 600 MW unit boiler to explore the effect of mix-firing sludge on the formation and emission of dioxins (PCDD/Fs). Under the conditions with and without sludge co-firing, flue gas samples at the inlet and outlet of drying-charring machine, the inlet of selective catalytic reduction (SCR) equipment, the outlet of air preheater and chimney as well as solid samples including raw sludge, dried and partly charred sludge, slag and fly ash were collected, and the PCDD/Fs were analyzed by a high-resolution gas chromatograph combined with high-resolution mass spectrometer. The obtained results indicated that, co-firing sludge (accounted for about 1% (weight percent) of pulverized coal) did not result in the formation of PCDD/Fs via high-temperature gas-phase homogeneous formation mechanism and medium- and low-temperature catalytic formation mechanism, and did not increase the emission of PCDD/Fs to atmosphere. The international toxic equivalence quantity (I-TEQ) concentrations of 6 chimney gas samples collected under the condition with sludge co-firing were in the range of 0.008~0.013 ng/m³ (average value: 0.010 ng/m³), which did not significantly differ from that (0.008~0.015 ng/m³, average value: 0.012 ng/m³) of the 6 chimney gas samples collected under the condition without sludge co-firing. It was found that, a small quantity of PCDD/Fs was formed during sludge drying-charring process. The newly-formed and original PCDD/Fs in sludge could be completely destroyed by high temperature in coal combustor. The SCR catalyst induced the catalytic degradation of PCDD/Fs, especially the highly-chlorinated dioxins. The concentration of the PCDD/Fs in fly ash samples were lower than 0.2 ng/m³, indicating its resource utilization could not pose dioxin pollution risk to ambient environment.

In the context of Europe's vision of achieving carbon neutrality by 2050, carbon capture, utilization and storage (CCUS) technology, as an important means to achieve carbon emission reduction goals, has embraced a major development opportunity. This paper summarizes the development status of CCUS in Europe, including the financial incentive policies, carbon tax and policies, laws and regulations, and technology innovation policy for the development of CCUS technology in Europe, and the challenges in the process of developing CCUS technology in Europe, including the implementation of public funds, the comprehensive development of CCUS policies, and clear definition of responsibilities for CCUS projects. It points out that up to now, the development of CCUS technology in Europe is relatively mature. Relevant laws and regulations, financial incentives, tax support policies, and technology innovation policies have come into effect. Bioenergy with carbon capture and storage (BECCS) and direct air capture with carbon storage (DACCS) are important means to achieve negative emissions in the future. CO₂ industrial clusters and the development of transportation network can greatly reduce the transportation cost of CO₂, create profits at scale, and thus promote the application of CCUS. In 2020, China made the pledge to achieve carbon peaking by 2030 and achieve carbon neutrality by 2060. Combining the development status and relevant policies of European CCUS with basic national conditions of China, it puts forward the urgent need for current development of CCUS technology in China, and the problems that need to be solved.

Under the policy of peak shaving and carbon trading, cogeneration units face a more complex background. In order to obtain the carbon emission characteristics, income distribution and carbon trading economy of the traditional extraction condensing cogeneration unit under all operating conditions, and provide a reference for the unit to deal with carbon market fluctuations when participating in carbon trading. Using EBSILON simulation software combined with python program, the carbon emission distribution and income composition of the unit under all operating conditions are obtained. The research results show that the carbon emission kilowatt hour is inversely proportional to the load. Taking 325 MW and 150 MW as examples, the carbon emission intensity of power supply increases from 903.54 g/(kW·h) to 1 015.28 g/(kW·h), and the total carbon emission is proportional to the load; The highest proportion of peak shaving income can reach 55%; The highest proportion of carbon trading income can reach 8%, and the peak shaving income accounts for a large proportion in the low load, while the carbon trading income accounts for a large proportion in the high load. Comparing the change of carbon price from 40 yuan/t to 90 yuan/t and the change of power supply carbon emission standard from 0.9 times to 1.3 times, it is found that the change of power supply carbon emission standard has a greater impact on the proportion of carbon trading income. The formulation of power supply carbon emission standard should be combined with the unit emission level. Too high or too low will affect the enthusiasm of cogeneration power plants to participate in carbon trading.

Chemical absorption method is an effective way to capture CO₂ from flue gas of coal burning. Compared with conventional organic amine absorbents, two-phase absorbent can significantly reduce the regenerative energy consumption and the capture cost. A new type of two-phase sorbent is developed, which uses the physical solvent diethylene glycol dimethyl ether as split-phase agent, ethanolamine and hydroxyethyl ethylenediamine as the main agent, and its absorption regeneration performance, viscosity, water phase proportion and phase separation interval is tested. Moreover, nuclear magnetic resonance (NMR) spectroscopy is carried out for the two phases in the sorbent to determine the composition and phase splitting mechanism. The organic amine composition in the formulation is optimized, and the results show that, the absorption and regeneration performance of the optimized absorbent is better than that of the conventional 5 mol/L ethanolamine absorbent. The cyclic absorption capacity can reach 2.086 mol/kg, more than 99% of CO₂ is enriched in water phase, and the flow of the absorbent entering into the regenerator can be reduced by about 40%. The viscosity of the water-rich phase is lower than 10 mPa∙s, the theoretical regeneration energy consumption is 2.688 GJ/t (calculated in CO₂), indicating the new two-phase sorbent has a good industrial application prospect.

To study the effect of decarbonization on thermal power units, a simulation model is established to analyze the performance changes of the conventional scheme of carbon capture retrofitting in thermal power units. Moreover, a zero-output scheme of a low-pressure turbine is further proposed to improve the flexibility of the units. The conventional method uses the exhaust steam of the intermediate-pressure cylinder as the reboiler heat source, and the zero-output scheme of the low-pressure cylinder cuts off the low-pressure cylinder inlet steam. On one hand, the two methods are analyzed separately by taking a 300 MW coal-fired power unit as an example. On the other hand, the effects of the two schemes on thermal power units of the whole province is predicted by taking a province in northwest China as a research object. The results show that, the unit output range under the conventional scheme is reduced from 87~300 MW to 147~217 MW, and the power supply efficiency under rated operating conditions decreases from 37.32% to 27.02%. The minimum unit load ratio increases to about 70%. The unit load range ise widened to 47~217 MW when the zero output scheme of the low-pressure cylinder is adopted, which is 2.44 times of that of the conventional scheme. For the discussed northwestern province, the thermal power output range is reduced from 1 103~3 940 MW to 1 875~2 793 MW under the conventional scheme, and the output range is widened to 550~2 793 MW under the low-pressure cylinder zero output scheme.

The implementation of carbon pricing policy will have an important impact on the low-carbon transformation of power industry. This paper constructs a power dynamic stochastic general equilibrium (DSGE) model with carbon pricing policy, and systematically investigates the different impacts of carbon trading and carbon tax on emission reduction of the power industry under the goal of carbon emission peak and carbon neutrality. The results show that, the overall impact of carbon trading policy is greater than that of carbon tax policy, and the impact of carbon trading policy on emission reduction is achieved by inhibiting thermal power output under the carbon peak scenario, while it is achieved by encouraging green power output under the carbon neutral scenario. Different mechanism designs of carbon pricing policies, such as carbon trading and carbon tax, will have different impacts on emission reduction in the power industry under the dual carbon target. In the carbon trading policy, especially in the carbon peak scenario, there is a certain upper limit to achieve emission reduction through the market mechanism, and when the upper limit is exceeded, a "back-forcing" mechanism will be formed. In the carbon tax policy, the rebate mechanism will achieve the goal of emission reduction and the expansion of the rebate proportion will strengthen the impact on electricity emission reduction. Based on the above conclusions, relevant policy recommendations are put forward.

Against the difficulty of optimal scheduling of integrated energy systems under the operating conditions of multiple energy complementary mechanisms, a multi-objective optimal scheduling study is carried out considering the reduction of system operation and maintenance costs, carbon dioxide emission and renewable energy abandonment. A mathematical model is established for all the equipments in the electric-gas-heat-cold energy system. The constraint conditions that can simulate the long-term operation scheduling of the integrated energy system are established to solve the modeling difficulties of energy storage equipment in the long-term operation simulation, and the comprehensive energy system is optimized by using low-carbon economic operation index. The results of the minimum operation cost scheduling and the minimum carbon emission scheduling are compared. Moreover, the influence of carbon price and operation and maintenance cost increase on scheduling results is simulated. The simulation results show that, using only the minimum operation and maintenance cost or the lowest carbon emission as the scheduling index will lead to high carbon emission or high operation and maintenance cost, and the low-carbon economic scheduling considering the consumption of renewable energy and carbon emission reduction index can reduce the low-carbon economic operation cost of the whole system.

Measuring the investment value and investment timing accurately is crucial for coal-fired power plants' carbon capture utilization and storage (CCUS) investment. Different from the existing studies on the CCUS decision making only considering the integration mode, this study establishes the decision-making model of the CCUS investment of coal-fired power plants under the integration mode and joint venture mode from the perspective of coal-fired power plants. The decision-making model is established based on the theory of real options, considering the uncertainties of carbon price and the decreasing CCUS investment cost, and the displayed solutions of the option value and investment timing of CCUS investment in coal-fired power plants under different modes are obtained by solving the model. Based on this model, the impact of different policy incentives such as additional power quota, electricity price subsidy, investment subsidy, and carbon price volatility on CCUS investment decisions are further analyzed through numerical examples. On this basis, some policy suggestions are provided finally.

In order to clarify the dynamic characteristics of bed temperature of biomass circulating fluidized bed (CFB) boiler, so as to establish a CFB combustion control system which is more suitable for biomass, a dynamic bed temperature model is established by analyzing the biomass combustion process and combustion mechanism. On the basis of the theory of instant burning carbon combustion, the correlation degree of temperature field in the furnace is calculated and analyzed. The results show that, the calculated bed temperature can be controlled basically stable near the filtering value of the actual bed temperature, and the variation trend of the bed temperature is similar to that of the actual filter bed temperature, which verifies the adaptability and effectiveness of the model. The temperature correlation difference of the upper and lower parts of the biomass CFB boiler is related to the oxygen content and the temperature of the furnace. The temperature difference of the left and right sides is greatly affected by the flue gas flow. In the upper part of the furnace, the material concentration and the uneven heating surface arrangement are also important reasons affecting the temperature characteristics.

A mathematical model of subcritical organic Rankine cycle (ORC) system is established for the flue gas waste heat of 120~150 ℃. Firstly, the thermal performance and economic performance of the system are analyzed at different heat source temperatures by taking R245fa as an example. Then, a multi-objective optimization study is conducted for six pure working fluids based on NSGA-Ⅱ algorithm. At last, working fluid selection and performance analysis of the ORC system with various heat source temperatures are carried out by TOPSIS method and gray correlation analysis. The results show that, in the temperature range of this study, the increase of superheat degree and evaporator pinch point temperature difference is not conducive to improve the system performance. The optimal working fluids are varied at different heat source temperatures, when the heat source temperature is 120 ℃, R601 has the best thermal performance, R245fa has the best economic performance and R1233zd has the best overall performance. The increase of heat source temperature is beneficial to improve the economic performance of the system. The optimal evaporation temperature of each working fluid increases with the heat source temperature. The gray correlation analysis indicates that the comprehensive performance of all six working fluids improves with the heat source temperature.