Research on low‐carbon system of biomass combustion and solar‐energy power generation based on MP‐PIC simulation

To vigorously reduce CO2 emission in the energy sector is an inevitable choice to achieve world's carbon emission reduction and to accelerate the construction of a modern energy system. The development of CO2 capture, utilization, and storage technology (CCUS) is of great significance for promoting low carbon utilization of traditional energy and realizing the low carbon transformation of coal power industry. The joint development of biomass combustion integrated with new energy technology and consideration of fuel conversion CO2 capture from the source is a technical solution with high efficiency and low energy consumption in coordination, which will bring new development opportunities for conventional thermal power industry. In this study, a low carbon system of collaborative renewable energy CO2 source capture is constructed. Numerical simulation method of multiphase flow coupled with thermal mass transfer and chemical reaction of the combustion mathematical model is employed to study the combustion characteristics in the biomass combustion system. The combustion efficiency, carbon conversion, and pollutant emissions are calculated compared with the conventional coal combustion system. Hydrogen production and CO2 emissions are analyzed based on life cycle assessment method. The energy integration full‐chain system of geological storage and CCUS is optimized, which is committed to achieving nearly zero carbon emission in the thermal power industry, contributing to the global low CO2 emission work.

Global coal consumption in 2022 increased to 8300 Mt with an average annual growth rate of 3.3% compared with the previous year.Coal consumption is slightly higher than the highest level since 2014, which ranks first among all kinds of energy sources. 1 In the face of CO 2 emissions problem for the thermal power industry, developing carbon capture and utilization technology by seeking renewable energy to take the place of traditional fossil energy has broad prospects.The joint development of biomass combustion and solar power generation technology as well as the coordinated consideration of the CO 2 capture issues from the source of fuel conversion is a technical solution with high efficiency and low energy consumption, which will bring new development opportunities for the thermal power industry.
Biomass energy is considered as one of the most promising green renewable energies in the 21st century due to its advantages of abundant resources, renewable, wide distribution, low CO 2 emission, and less emission of air pollutants. 2 Biomass and renewable energy coupled power generation technology provides a new way for renewable energy generation, and the demonstration and application of biomass and photothermal coupled power generation are the key directions of diversified energy utilization development. 3The complementarity of solar energy and biomass is an effective way to reduce the dependence on nonrenewable energy and pollutant emission from the raw material side.It mainly adopts concentrated solar power generation coupled with biomass power generation and solar energy as auxiliary to reduce the heat consumption rate and steam consumption rate of steam turbine as far as possible under the premise of ensuring the efficiency of solar power generation.The schematic diagram of its coupling system is shown in Figure 1.Most of the research on this technology is to establish the complementary power generation system combining biomass energy and solar energy based on the energy analysis and exergy analysis of the law of thermodynamics, and then to analyze the performance of the coupled system according to thermal economics. 4It is found that this technology can theoretically improve the power of the generator set, and solve the serious problems such as a poor economy of biomass power generation, too long purchase, storage radius, insufficient scale, and seasonal impact of fuel acquisition.There are a number of biomass and solar complementary projects that have been built or started around the world.However, the key problems of biomass and solar coupling power generation need to be solved in the high proportion coupling principle and design method of solar thermal, system integration, regulation strategy, and flexible peak regulation of power stations.The research on the coupling of the industrial-scale biomass combustion system and solar power generation is still in the blank, and the interaction influences regularity and the coupling correlation mechanism between the two systems are still unclear.
One of the most widely used reactors in industry is the circulating fluidized bed (CFB).For biomass CFB combustion power generation technology research mainly focuses on the construction of the conventional steam dynamic circulation system and the modular construction of combustion system, [5][6][7] and cold gas-solid hydrodynamic numerical simulation study for the industrial scale and combustion simulation for laboratory scale and pilot scale.The research on combustion characteristics, system efficiency, and carbon conversion of industrial-scale CFB is still lacking.The F I G U R E 1 Schematic diagram of the coupling system of biomass combustion and solar power generation.
technology still has a very broad prospect, if can be improved, energy transfer will be greatly improved.
Carbon capture, utilization, and storage (CCUS) is a key technology to achieve the carbon neutrality target, which is expected to provide 1.1-2.7 billion tons of carbon emission reductions by 2050.The United States earlier used the traditional thermal power industry to apply CCUS technology combined with the carbon market.At present, there are 14 operational commercial CCUS projects, 8,9 which mainly use absorption method, sorption method, membrane method, low-temperature freezing method, and other methods for CO 2 capture. 10,11The CO 2 can be stored and used in two paths. 12,13One is geological storage and solidification, or strengthen the exploitation of oil and natural gas resources, and the other is the synthesis of valuable chemicals, such as beverages and food additives.Conventional thermal power unit combined with CCUS new technology to build a new thermal power industry chain is an opportunity to realize transformation and upgrading and move towards the road of low carbon.At present, it has great development prospects all over the world.From the perspective of capture technology, the CO 2 fraction of flue gas in power plants is minimal, and the amount of flue gas is huge and the composition is complex.Post-combustion capture based on the chemical solvent absorption method is a widely used choice. 14From the perspective of utilization technology, CO 2 in industrial waste gas is converted to high-value-added chemicals, which not only helps achieve carbon emission reduction, but also improves the resource recovery and utilization of CO 2 .At present, the research on the thermal power industry and CCUS coupling system are mainly focused on the laboratory exploration stage, and the research direction mainly focuses on the capture of CO 2 after combustion and realizes the reuse technology through further chemical means.There is little research on the capture and utilization of CO 2 from fuel conversion source and renewable energy.The CCUS system based on biomass combustion coupled with solar energy is an innovative proposed process.

| NEW PROCESS ROUTE
On the basis of the above issues, this study puts forward "biomass combustion coupling solar power and CCUS" new process route, as shown in Figure 2. The inputs of this system are solar and biomass energy, both of which are clean, cheap, and easy to obtain in the nature.The outputs of this system are power energy and hydrogen energy, which are valuable and can be used in aerospace, new energy vehicles, building heating, and other industry fields.The CO 2 generated by the system reaches a closed loop through the utilization and storage process, and the nearzero emission target of CO 2 can be finally achieved.The system consists of three modules, namely, biomass combustion module, solar photovoltaic power generation module, and CO 2 utilization and storage module.The core of the system is the biomass combustion module, where the biomass and air enter the biomass boiler after the combustion process to release a large amount of heat.Steam-water mixture circulates continuously and regularly in the heat exchange tubes laid on the heating surfaces.The F I G U R E 2 Schematic diagram of the coupling system of biomass combustion and solar power generation.heat generated by the combustion is absorbed from the flame and makes high-temperature flue gas form hightemperature steam vapor.The high-temperature steam vapor drives the steam turbine to generate electricity.The flue gas generated by the boiler is sent to the flue gas and is recycled to the back to the boiler to continue to participate in combustion.In the solar photovoltaic power generation module, according to the principle of the photovoltaic effect, the solar cell is used to directly convert solar energy into electric energy.Biomass combustion module and solar photovoltaic module power generation module are used for catalytic electrolysis water to produce H 2 .In the CO 2 utilization and storage module, on the one hand, H 2 , which is produced by the above two modules and other industries, integrated with CO 2 from the flue gas purification device participate in CO 2 /H 2 reforming process to make chemicals like dry ice.On the other hand, the CO 2 after the flue gas purification device goes through the compression unit to finally realize geological storage.The output of the novel is two products which are not easy to obtain and expensive, namely, electricity and hydrogen energy.The electricity output generated by the biomass combustion power generation CCUS system is used to offset the energy required by itself, thus bringing considerable carbon reduction benefits.Hydrogen energy is easy to store and transport, and it can be used as an energy carrier to replace electric energy in transportation, power generation, energy storage, industry, and other fields.
According to the existing key problems, three research contents are formulated: (1) The efficiency of low carbon system of biomass combustion process collaborative renewable energy CO 2 source capture and conversion is calculated.(2) Combustion characteristics and combustion efficiency of the biomass combustion system are explored.
(3) Utilization and geological storage of CO 2 as well as CCUS full-chain system is integrated and optimized.The process route fully considers the existing energy industrial structure and geological conditions, and is expected to be applied in a short time to achieve nearly zero carbon emissions of thermal power industry, and contribute to the world's "carbon peak" and "carbon neutral" work.

| Solar-energy photovoltaic power generation efficiency
According to the basic data of photovoltaic modules (power, size, quantity, etc.) and power generation efficiency of the grid-connected photovoltaic system, the power generating efficiency of the system is according to Equation (1). 15

L W H
where L is the power generation, W is the total installed capacity, H is the annual peak sunshine hours, and § is the total efficiency of the grid-connected photovoltaic system.

| Hydrogen production efficiency of water electrolysis
In the actual electrolytic production process, the optimal solution is to generate an equal amount of hydrogen that consumes less electricity, so the electrolytic cell conversion efficiency equation ( 2) is defined as where Q H represents the volume flow rate of the generated hydrogen gas, p H represents the pressure of the generated hydrogen gas, I represents the current passing through the electrolytic cell, and V represents the interelectrode voltage of the electrolytic cell.
The physical significance of Equation ( 2) is that the more the amount of hydrogen produced by electrolysis of unit power, the higher the conversion efficiency of the electrolytic cell.According to Faraday's law of electrolysis, the water current effect is 100%.Equation ( 2) is further deformed as listed in Equation ( 3) where n represents the electronic stoichiometric number of the consumption of the hydrogen evolution reaction (n = 2), and F′ represents Faraday constant (96,485 C/mol).

| Test platform
On the basis of the advantages of Northwest China, solar energy and biomass resources are both rich, and light energy is used to realize biomass combustion power generation.Solar panels (Yingli YL330CELL × 5, 330W33V9A) and a photovoltaic controller (photosynthetic silicon energy, MPPT, universal, 40 A 12V24V36V48V, self-applicable 40 A) are adopted.The capacity of the biomass combustion power generation is 600 MW.The combustion process of one typical biomass component of corn straw is considered.A test platform for adjustable premagnetic polarized water electrolysis has been conducted.The electrolyte is distilled water with an initial conductivity of 0.4 μS/cm, and the intelligent peristalsis pump is used to control the flow rate of distilled water.The proton exchange membrane electrolytic cell is used to produce hydrogen, the voltage between the poles is detected by a high-precision desktop digital multimeter, and the change process of hydrogen production is recorded with a high-speed camera.The connection diagram of the actual test equipment is shown in Figure 3.The distilled water of each sample is maintained at a flow rate of 500 mL/min under the control of the intelligent peristaltic pump, and a high-speed camera is used to record the change data of hydrogen production in different samples in the first 100 s.Finally, the obtained test data is processed and analyzed, the hydrogen production efficiency of water electrolysis is calculated.The efficiency obtained by the water electrolysis experiment is finally extended to the efficiency of hydrogen production on the industrial scale.

| Biomass combustion power generation efficiency
[17] where W net represents the net power.Q LHV represents the low calorific value of biomass gas.ρ LHV represents the biomass gas density.α represents the residual gas coefficient.L 0 represents the theoretical air quantity required for gas combustion per unit mass.
The low calorific value of biomass gas (Q LHV ) is the main index to measure the quality of gas, which is shown in Equation ( 6), and the calculation formula of overall gasification efficiency (η CGE ) of biomass two-stage gasification system is shown in Equation (7).[17] F I G U R E 3 Schematic diagram of equipment for water electrolysis experiment.DC, direct current; PEM, proton exchange membrane.
where φ (CO) , φ (H ) 2 , and φ (CH ) represent the volume fraction of CO, H 2 , and CH 4 in gasification gas, respectively.Q ar represents the low calorific value of biomass raw material.Y g represents the biomass gasification gas yield.G b represents the biomass charge.

| Multiphase particle-in-cell (MP-PIC) simulation method
This study introduces a numerical calculation method based on the MP-PIC, which can effectively solve the coupling calculation problem of fluid and a large number of particles in the three-dimensional space of the biomass combustion system.The MP-PIC method, first proposed by Andrews and O'Rourke 18 and Snider, 19 is the most distinctive feature of this method is the ability to couple the momentum equations of particles and fluids in three dimensions.Specifically, the fluid phase is treated using the Euler method, the momentum equation is represented by the Navier-Stokes equation, while the particle phase is treated by the Lagrangian method and coupled to the fluid phase equation.In the calculation, the numerical particles used are not real particles in the physical sense, but are composed of a certain number of particles with the same properties (composition, size, density, and temperature, etc.).With such treatment, gas-solid systems containing hundreds of millions of particles, such as biomass combustion systems, can be simplified to systems containing only millions of particles, while the treatment of particle phases in the MP-PIC method can be still well utilized.Through this calculation mode, the simulation of the full-size distribution of any solid particles can be achieved. 20Simulations of particle concentration from very dilute to close packing can be achieved in a single calculation without prior determination of the particle concentration range.Information of particle mass, momentum, heat transfer, wear and other complete Lagrangian sense is obtained, which is suitable for gas-solid systems with simulated particle quantity over 1016.This provides a feasible means to quickly and accurately capture the dynamic characteristics of gas-solid flow in the biomass combustion system.
In the simulation process of the biomass combustion in the CFB boiler, the following assumptions are made: (1) The temperature of the biomass particles is uniform, and there is no heat conduction between the particles.(2) During volatilization, both the size and the density of biomass particles decrease.(3) During pyrolysis, the particle size remains unchanged, and the density reduces.(4) One calculated particle within each particle cluster represents one or more real particles and assumes that they have the same properties.
2][23] Governing equations mainly include the mass conservation equation, the momentum conservation equation, the energy conservation equation, and the constitutive equations for gas and solid with combustion and heat transfer models.The Wen-Yu-Ergun model represents the drag force between gas phase and solid phase.For the simulation of the combustion process in the biomass CFB boiler, complex heat transfer models were adopted including convection and radiation among particles, gases, cold wall and platen heating surfaces, and combustion models, including pyrolyzation, combustion, gasification, and pollutants emission.

| Life cycle assessment method
The life cycle assessment method can be well used to evaluate the environmental impact of different links throughout the life cycle of the energy conversion system.The life cycle assessment conducted in this study, which refers to the standard methods of ISO 14040, ISO 14044, and so forth, mainly includes four stages: (1) determination of objectives and scope, (2) determination of life cycle data list, (3) life cycle environmental impact assessment, and (4) interpretation of life cycle results.Taking the carbon emission of different stages in the whole life cycle of the biomass combustion power generation CCUS full-chain system transformation as the evaluation index, the process parameters used in the evaluation are taken from the operation data of the demonstration project, and the relevant characteristics and background parameters refer to the GaBi 7.0 life cycle evaluation software and database developed by Thinkstep Company and the literature data. 24,25

| Efficiency of low carbon system
The calculation of the efficiency of "biomass combustion coupled solar power generation and CO 2 utilization and storage low carbon system" is divided into two parts, which are the efficiency of solar photovoltaic power generation and biomass combustion power generation efficiency, respectively.The reduction of system capacity and CO 2 emissions is calculated on the basis of system efficiency calculation.
On the basis of the above polynomial fitting calculation model, solar photovoltaic power generation efficiency and biomass combustion power generation efficiency can be calculated.The photovoltaic module size for this system is 1650 and 992 mm, and the number of photovoltaic modules is 12,600 solar photovoltaic panels and 600 MW biomass combustion systems.With the system input value of 286 MJ/m 2 of solar energy and 100 tons of biomass, the system will produce 19.87 million kWh of electricity and 7.467 million tons of hydrogen.Through CCUS technology, utilization of CO 2 reaches 13,305 tons and the storage of CO 2 reaches 8870 tons.The specific capacity and CO 2 emission reduction of the system are given in Table 2.The system guarantees that 75% of new energy can replace thermal power.On the basis of the world's current thermal power generation, the thermal power industry can achieve an emission reduction of CO 2 to about 1.2 million tons per year.Thermal power units can reduce carbon deeply under harsh conditions and can reduce CO 2 by more than 2 million tons per year by reducing power generation coal consumption by 5 g/kWh.

| Characteristics of the biomass combustion system
Time-average temperature distribution of the gas phase and the solid phase in the furnace are obtained based on biomass combustion system numerical simulation, as shown in Figure 4.The biomass combustion system is essentially a CFB boiler with a capacity of 600 MW.The overall temperature distribution of the furnace is relatively uniform, and the gas phase temperature T A B L E 1 Governing equations.

Gas phase mass conservative equation
Species conservation equation for the gas phase Transport equation for particle distribution function Equation for particle acceleration

CUI and WANG
| 1509 distribution is similar to the solid phase temperature distribution regularity.The primary air with a slightly lower temperature (763 K) and the circulating flue gas (1.5% O 2 , 23.2% CO 2 , 5.87% H 2 O, 69.23% N 2 , 1000 ppm CO, and 1000 ppm NO) with a temperature of 815 K enter the furnace evenly from the air plate at the bottom of the furnace, and a violent combustion reaction occurs after mixing with the fuel, which is quickly heated above 1178 K.The reaction continues to heat up, and the temperature continues to rise along the height of the furnace.The secondary air (763 K) is sent into the furnace from 14 secondary air outlets at the height of the outer ring wall of 7.5 m.The temperature of the corresponding secondary air outlets in the furnace is low.
Because the large amount of oxygen supplied by the secondary air promotes the combustion, the temperature between the height of 15 and 35 m increases significantly.
Due to the excellent heat transfer performance of the water cold wall and the platen heating surfaces, the temperature of the upper part of the furnace drops slightly.In addition, the gas phase temperature is slightly higher than the solid phase temperature, this is due to most particles in the solid phase being inert bed material, which does not produce chemical reaction, and the temperature rises from the combustion heat.Regardless of homogeneous reactions or heterogeneous reactions, the heat generated by the reactions needs to transfer part of the heat to the solid bed material through interphase or alternate-phase heat transfer, so the gas phase temperature in the area where biomass and volatile combustion occurs is higher than that of the solid phase.Due to the unique heat transfer conditions of S-CO 2 CFB boiler, the generated flue gas temperature is higher than  that of conventional water vapor.The temperature of flue gas produced by the boiler is about 880°C, but the final temperature is reduced to 120°C after the heat transfer devices, such as high condensate slag tube, superheater, economizer, air preheater, and the dust removal device.Figure 5 displays the concentration distribution of the three main gas components (including O 2 , CO 2 , and CO) producing from the combustion in the furnace.O 2 concentration drops rapidly above the height of 35 m, the concentration distribution of CO 2 is just opposite to O 2 , rises sharply at this height, and the two gases distribute symmetrically along the centerline.CO 2 and the carbon particles in biomass undergo a reduction reaction at high temperatures to produce CO gas.Incomplete combustion occurs and increases the produced CO significantly due to a large supply of fuel at the coal-feeding inlets, and the CO concentration decreases along the furnace height due to dilution.The CO 2 emission concentration of the biomass combustion system is 11.2% below the traditional level (around 12.5%), and the O 2 and CO emission concentrations are higher than that of conventional coal combustion system, [26][27][28][29] indicating that the biomass combustion system proposed in this study has higher carbon conversion and combustion efficiency than the traditional coal-fired system.
NO x concentration distribution along the combustion chamber is also displayed in Figure 5D,E volatile and very low ash, and the combustion intensity is very strong, so the fuel NO emission is concentrated within a short time.The ash of biomass leaves is higher than the biomass branch is relatively low, and the NO emission is slightly flat.In the case of accumulation combustion, the NO release peak occurs in the process of biomass branch burning.SO 2 concentration distribution along the combustion chamber is illustrated in Figure 5F, which shows the trend of increasing first and then declining.The sulfur in the biomass is mainly the organic sulfur in the body structure, such as amino acids, proteins, as well as the inorganic sulfur present in the form of sulfate.It is generally believed that organic sulfur tends to be oxidized during pyrolysis, while various sulfates may volatilize, decompose at high temperatures, or stay in ash according to the specific reaction environment.The outlet NO x and SO 2 concentrations are around 450 and 320 ppm, respectively.
The carbon conversion rate (ω C-CO 2 ) studied in this study refers to the share of carbon in coal into flue gas CO 2 through the combustion process, reflecting the proportion of solid carbon into gas CO 2 , which is closely related to the boiler combustion efficiency.Higher carbon conversion means more adequate combustion, while lower carbon conversion means more fuel is not fully burned.This chapter adopts carbon conversion rate calculation Equation (9) 30 calculates the carbon conversion rate of the biomass CFB boiler.Where M C CO -2 is the mass of carbon in CO 2 , f bio represents the biomass-feeding rate, and ω bio-c is the mass fraction of carbon in biomass.
Improving boiler combustion efficiency and reducing energy consumption are essential for improving boiler efficiency.In this study, the combustion efficiency (η) is calculated by Equations ( 10)-( 14), 31 and the incomplete heat loss of combustible gas (q 3 ) and the incomplete heat loss of solid fuel (q 4 ) are considered.The above two heat losses dominate the thermal equilibrium system, while the others are negligible.The calculation of combustion efficiency and heat loss refers to GB10184-88 32 and ASME PTC4-1998. 33q q = 1 − − , where q CO , q H 2 , and q CH 4 represent the calorific values of CO, H 2 , and CH 4 gas, respectively.Q net,ar is the thermal input of the fuel.The c p,CO and V CO represent the average constant pressure specific heat and CO gas volumes.The q 4 FA indicates incomplete combustion heat loss, but the simulation of the biomass combustion system does not include any slag discharge system, and the bottom slag heat loss can be omitted.Q B , G C-FA , G B-Fuel , G C-Gas , and G F-unburn represent the calorific value of the biomass, the carbon mass in the ash content, the fuel input, the carbon content of the generated gas, and the quality of the unburned fuel, respectively.On the basis of the above equation calculations, the carbon conversion rate (ω C-CO 2 ) and combustion efficiency (η) of the biomass combustion system are 96.45% and 97.98%, respectively.

| CCUS full-chain system energy integration
The full-chain system of biomass combustion power generation CCUS predicts its efficiency and CO 2 emission reduction through the life cycle evaluation method, and the boundary of its life cycle evaluation system is shown in Figure 6.The life cycle stage of the evaluation system mainly includes the raw material acquisition stage, the processing and transportation stage of materials and equipment, the demonstration project transformation stage, the use stage and the final waste treatment, and disposal stage.Resources, energy input, power, heat, direct environmental emission, and indirect environmental emission output of different life cycle stages are all considered in the evaluation process of this study.The output of the system is the power generated by the thermal power generation system, which is employed to offset the environmental emissions of generator power products with the same amount from the production process.The direct and indirect CO 2 emissions as well as related economic analysis are calculated.The list of input, output substances and energy of the CCUS system is shown in Table 3.The input material and energy of the system include power, temperature difference power generation materials, steel, collectors, water pipes, and so forth, and the output material and energy include power, heat and environmental emissions, and so forth.The CO 2 emission factor corresponding to the input and output material and energy evaluated by the CCUS system is shown in Table 4. Figure 7 illustrates a schematic diagram of the carbon emission footprint of the life cycle of the biomass combustion power generation CCUS full-chain system.From the perspective of carbon footprint in the system life cycle, the carbon emissions of the system mainly come from the acquisition stage and processing integrated with the transportation stage of raw materials, which account for 28.4% and 71.3% of the total carbon emissions in the life cycle, respectively.Among them, the carbon emissions generated in the raw material acquisition stage mainly include chemical, physical, and CO 2 emissions in various reactions.The carbon emissions generated in the processing and transportation phase are 0.11 t CO 2 e, mainly due to the large amount of energy consumption generated in biomass combustion and power generation CCUS systems.The carbon emissions generated in the optimization and transformation stage and the final waste disposal stage are 4.67 and 39.26 kg CO 2 e, respectively.It should be clear that, due to the lack of relevant data, after the end of the life cycle of the biomass combustion CCUS system, only the emissions of all the removal into the landfill during the F I G U R E 6 Biomass combustion power generation CCUS full-chain system life cycle assessment system boundary.CCUS, carbon capture, utilization, and storage; PV, photovoltaic.
T A B L E 3 Input energy data for biomass combustion power generation CCUS system assessment.

Energy input
Energy transportation process and landfill operation process are taken into consideration, while the recycling of metal materials or the CO 2 emission of the landfill are not taken into account.The power output generated by the biomass combustion power generation CCUS system is used to offset the energy required by itself, thus bringing considerable carbon reduction benefits.According to Gabi software database, the CO 2 emission factor of the biomass combustion power generation CCUS system is 0.96 kg/(kWh), and the total power output generated by the system is estimated to be 1.23105 kWh, thus bringing carbon reduction benefits of 117.85 t CO 2 e. F I G U R E 7 Schematic diagram of carbon emission footprint in the life cycle of biomass combustion power generation CCUS full-chain system.CCUS, carbon capture, utilization, and storage.

| Economic feasibility analysis
This study used the life cycle assessment method to analyze the construction, installation, operation, equipment update and scrap cost of the coupling system of biomass combustion and solar power generation.The life cycle of the evaluation system is designed for 20 years according to the working time of photovoltaic panels and the biomass combustion power generation CFB boiler.
The energy supply mode used in this study can save the investment cost by comparing the whole life cycle cost.Table 5 lists the construction and investment of the novel system.According to the whole life cycle cost evaluation, the sum of the construction cost, operation, and maintenance cost of the coupling system of biomass combustion and solar power generation within 20 years is $6340.95.Compared with the conventional independent coal-firing power generation system and solar electrical energy generation system, the novel system has low cost and good economy.

| CONCLUSIONS
This study puts forward a biomass combustion coupling solar power and CCUS low carbon system to accelerate the modern energy structure adjustment optimization and solve the thermal power industry CO 2 emission problem.The efficiency of the low carbon system, the biomass combustion system, and the CCUS full-chain system energy integration are analyzed comprehensively based on MP-PIC numerical simulation method and life cycle assessment method with the main conclusions listed as follows: (1) The novel system inputs 286 MJ/m 2 of solar energy and 100 tons of biomass, producing 19.87 million kWh of electricity and 7.467 million tons of hydrogen.Through CCUS technology, the amount of CO 2 utilization and storage reach 13,305 and 8870 tons, respectively.Thermal power units can reduce coal consumption and CO 2 by more than 5 g/kWh and 2 million tons per year, respectively.(2) The biomass combustion system is cleaner than the traditional coal-fired power generation system, with lower pollution and more energy saving.The CO 2 emission concentration of the biomass combustion system is 11.2% lower than that of the traditional coal combustion system with equal power, while the O 2 and CO emission concentrations are higher, indicating a higher carbon conversion rate (96.45%) and combustion efficiency (97.98%) of the novel biomass combustion system.(3) The power output generated by the biomass combustion power generation CCUS system is used to offset the energy required by itself, thus bringing considerable carbon reduction benefits.The CO 2 emission factor of the biomass combustion CCUS system is 0.96 kg/(kWh).
In the whole life cycle, the total power output generated by the system is estimated to be

4
Input and output of material or energy corresponding to the CO 2 emission factor in biomass combustion power generation CCUS system assessment.CCUS, carbon capture, utilization, and storage.
. NO x concentration distribution, especially NO, indicates two value peaks.This is because the generation of NO x mainly occurs in the early combustion stage of volatile emission and ignition.Since the biomass branch contains high F I G U R E 5 Distribution of gas components in the biomass combustion system: (A) O 2 , (B) CO 2 , (C) CO, (D) NO, (E) N 2 O, and (F) SO 2 .CUI and WANG | 1511 + Input energy data for biomass combustion power generation CCUS system assessment.
1.23105 kWh, bringing a carbon reduction benefit of 117.85 t CO 2 e. Life cycle assessment of the novel system.
T A B L E 5