Dong Jinning. Li Mao Dong, Zhang top, You Zhidong, Zhong Zhiqiang, Wang Peng
Abstract: In order to study the environmental impact and energy consumption of biomass industrial boiler system, this paper adopts the research method of life cycle (LCA), from the raw material production of this system to the establishment and operation of the system to conduct a comprehensive analysis.The results show that: Biomass particles, the total impact load on the environment is 16434.47 milliequivalents, the resource depletion coefficient is 2.547 milliters, the environmental impact of the combustion biomass biomass boiler system on the environment is mainly 95.36%, and the operation of the boiler system in each process is affected 98.55%, straw planting absorbs CO from the environment 22136.24kg, biomass-fired industrial boiler systems can play a positive role in reducing greenhouse gas emissions and biomass boilers are environmentally friendly and reduce fossil fuel consumption compared to coal-fired boilers.
0 Preface
At present, the fossil resources are gradually depleted, and the industrial boilers, which are high-energy consuming devices, have an important impact on energy and environment. China is a country that uses coal as its main energy source, and coal-fired industrial boilers account for over 80% of the total industrial boilers. The large amount of industrial boilers, large average capacity, large energy consumption, serious pollution, to find new environmentally friendly alternative energy sources to solve the pollution and energy consumption of high-energy coal-fired industrial boilers now become an urgent problem facing our country. Therefore, making full use of biomass straw resources and developing biomass boilers have become a good way to solve the problem of waste of straw resources and high energy consumption and high pollution of industrial boilers in our country, and provide the large-scale production of biomass forming fuels The necessary conditions.Previous studies on the manufacturing process of biomass pellets and biomass boilers have more research and development, but nowadays, more mature biomass boiler products have been applied and produced, and less research has been done on the whole life cycle of their systems. In order to grasp the comprehensive data of resource consumption and environmental impact of biomass-fired particulate industrial boiler system, Material shaped particles industrial boiler systems life cycle assessment.
A life-cycle inventory analysis of a biomass-fired particulate industrial boiler system
1.1 research objectives and scope of the study
In this paper, the biomass-formed granular industrial boiler system with the model number of DZIA-1.25-BMF is studied, the design efficiency of the boiler is 81%, the rated evaporation is 4t / h and the fuel consumption is 701kg / h.In this paper, The impact of burning 1t biomass shaped particles on the environment was analyzed and calculated, that is, the functional unit of environmental impact assessment was 1t biomass particles.
Due to the rather complex nature of biomass-formed particle industrial boiler systems, minor factors are ignored in life-cycle analysis, taking into account the major factors, neglecting straw harvesting and stacking during system operation, and the impact of industrial production on the steam quality fluctuations that produce steam Since the system has a long service life, assuming the service life of the system is 20 years, ignoring the influence of other factors on the assumption of the system of raw materials needed for the production and scrap the impact of the uniform distribution of the system runtime The main process includes five sub-processes of straw planting, transportation, biological particle production, system construction and system operation, etc. The five sub-processes are mainly analyzed from the aspects of environmental impact and energy consumption.
Among them, the straw needed in the process of planting CO 2Is taken from the life cycle system to supplement the life cycle system boundary analysis of the biomass-formed pellet industrial boiler system (Figure 1).
1.2 system material calculation
In this paper, corn stalks to obtain biomass particles for the system of raw materials for analysis, elemental analysis of biomass particles are shown in Table 1. Straw is an annual crop, corn yield 5154kg / hm 2· A, corn stover yield coefficient of 1: 1.2, corn C absorption is 5.08t / (hm 2Assuming that the C absorbed by the crop is evenly absorbed by the grain seed and its straw, the fuel required for the drying of the biomass pellet produced by the straw is the biomass pellet J, the amount of fertilizer required for straw growth and the amount of nutrients in the soil The fertilizer is ammonia, calcium and potassium sulfate. According to the design information of the biomass boiler, the required steel is 28.1t. Suppose the building materials required for system construction are 3: 1 for steel and cement, and the system is constructed and operated for 20 years. The amount of biomass consumed is 1000 T. The amount of each substance required and produced per 1 ton of biomass particles can be calculated by analysis and calculation as shown in Table 2.
1.3 list analysis
The main process of the impact of corn stalks planting process on the environment and consumption is straw photosynthesis absorption of CO 2And the process of fertilizer production of NPK.The transportation process assumes that the distance between the straw production site and the biomass particle production plant and the transportation radius of the biomass particle and biomass boiler system are both 100km and 25t transport trucks, The main environmental impact of the transport phase of the system is the production and consumption of diesel emissions.The biomass pellet preparation stage is the process of straw crushing, straw granulation and particle drying etc. The system construction phase mainly involves the consumption of building materials such as steel and cement, etc. The system The operation phase includes the combustion of the main unit and the consumption of auxiliary machinery.
In studying the system's resource consumption and environmental impact, it is assumed that the CO 2Is provided throughout the life cycle, so the system consumes 1t of life-cycle emissions of biomass particles in Table 3.
2 life cycle impact assessment
2.1 Environmental Impact Assessment
Environmental impact assessment includes both quantitative and qualitative evaluation. According to the IS014040 framework of the International Organization for Standardization, the impact assessment consists of three steps: classification, characterization and weighted assessment. The results of the above inventory analysis only show the relative value of various inputs and outputs Because of the contribution of various emission factors to ecosystem and environmental changes, life-cycle impact assessment needs to be carried out to translate the results of the inventory analysis into indicators that are both easy to understand and reflect the environmental impact potential.
Based on the results of the inventory analysis in Section 1.3, the possible resource depletion and potential environmental impacts of the biomass boiler system are shown in Table 4.
2.2 resource depletion coefficient
The resource depletion coefficient is characterized by a primary energy consumption, where energy is evaluated as a resource. Since the consumption in Table 3 only expresses the absolute consumption of resources and does not reflect its relative size, it is standardized using the resource consumption benchmark , And draw the potential consumption of resources such as coal and oil, as shown in Table 5. The unit is the equivalent of milligrams, which reflects the proportion of resources consumed by the biomass industrial boiler system in the per capita consumption of resources, based on 1990. After standardization The resource consumption reflects only the relative size of various resource consumption and does not reflect the scarcity of resources.The value of resource consumption after normalization weighted analysis is shown in Table 5. Table 5
After standardization, the consumption of coal is still the main part, accounting for 96.43%, the oil consumption is 3.57%, taking into account the scarcity of resources. After the standardized weighting, the proportion of coal consumption dropped to 87.24%, while that of oil rose to 12.76%. The consumption of coal occupies the main position in the energy structure, after the system of sludge treatment and utilization of resources, effectively curbing the consumption of coal resources.The biomass resource consumption coefficient of 1t biomass particle processing system is 2.547 × 10-3Human equivalent The resource consumption coefficient of 1t biomass particles per treatment is shown in Fig.2.
2.3 environmental impact load rating
2.3.1 Environmental Impact Calculation
In order to facilitate the visual display of the impact of various types of environmental impact potential, global warming with CO 2As a reference, empathy acidification, eutrophication, photochemical ozone were SO 2, NO 3-, C2H4As a reference.Effective equivalence factors of various emissions can be calculated for various substances in the process of environmental impact potential, as shown in Table 6.
2.3.2 Environmental Impact Standardization of potential
The corresponding standardized benchmarks are standardized and their relative sizes are compared for the various types of environmental impact potentials (global, regional and local) calculated above. Since standardization is based on 1990, weighting factors are used to normalize values Converted to 2000. Table 7 shows the standardized values and weighting factors for various types of environmental impacts.
Therefore, various environmental impact potential standardized and weighted values shown in Table 8.
2.3.3 Weighted Assessment and Environmental Impact Load
Weighed the impact potential standardized above and calculated the total environmental impact load per 1t of biomass particles to 16434.47 milli equivalent.Phase of the system relative contribution as shown in Figure 3. The results show that the biomass boiler system process The contribution of environmental impact is 98.55%, and straw planting process is -0.57%, which shows that the process can optimize and improve the environmental impact.By the relative contribution of various environmental impact types, it can be seen that the biomass boiler system has great influence on the environment The main effect is global warming (95.36%).
That is to say, in the biomass-fired boiler system, the global impact takes the first place, followed by the local effect, while the regional impact is the smallest.
3 Conclusion
In this paper, a comprehensive analysis of the environmental impact and resource consumption of biomass-fired biomass industrial boiler system is conducted with the method of life cycle. The following results are obtained through the analysis:
(1) The resource consumption coefficient of biomass industrial boiler system taking corn stover as 1t biomass particle as an example is 2.547 × 10-3The equivalent of manpower, after conversion, accounted for 87.24% of the coal consumed by the weighted resources and 12.76% of the oil, indicating that the consumption of coal in China's energy structure occupies a major position.
(2) The biomass boiler system has the largest contribution to the environmental impact of the whole life cycle, accounting for 98.55% of the total. The impact of global warming on the environment is 95.36% of the total.
(3) Although the global impact of a biomass-fired industrial boiler system is greater than that of local and regional influences, its impact is less than that of coal-fired industrial boiler systems and the system absorbs CO 22136.24kg, which can effectively curb the aggravation of global warming. Therefore, the system is environment-friendly and is an environment-friendly system project.
