Energy Consumption Analysis Of Coal-fired Central Heating System And Experimental Study On CO₂ Fixation From Simulated Flue Gas By Microalgae

Because of lower efficiency and seriously energy wasted, it’s necessary to analyze the energy consumption of central heating system. As an important part of the central heating system, it’s of vital importance to improve the thermal efficiency of heat source. There are still some problems of heat source with circulating fluidized bed boiler which are widely used in heat source need to be further studied, such as the thermal efficiency can not reach the design value, the optimized analysis of circulating fluidized bed boiler is essential. The heat source mostly use the coal as fuel, but the coal-fired boiler would release pollutants and greenhouse gases. The globe warming caused by the elevated CO₂ levels in the atmosphere is of big concerns. Biological CO₂ mitigation by microalgae is an effective method for carbon sequestration.Around the above goals, taking the heating system of Chang’an heating company as an example, this paper summarized the theoretical equations of thermal efficiency in central heating system of Chang’an heating company and the each part（heat preparing, heat transfer, heat transport and heat usage）. The heat losses of boiler and pipe network are the mainly factors which affecting the thermal efficiency of central heating system. Through collecting the operating datas of 2 circulating fluidized bed boilers of 50t/h in 24 days, the thermal efficiency of boiler（3# and 4#） calculated by positive balance method with the measured datas were 80.76% and 79.38%, and they were lower than the design values. The thermal efficiency of boiler（3# and 4#） estimated by negative balance method with the measured datas（some of the dates were experience values） were 85.59% and 85.51%, and the heat losses of exhaust flue gas and solid incomplete combustion occupied the largest proportion in total losses. The factors affecting the heat losses of exhaust flue gas and solid incomplete combustion are mainly air flow, fuel particle, bed temperature, boiler load, etc.. Aiming at the potential capacity of boiler flue gas emission reduction by microalgae, Chlorella vulgaris（FACHB-1227） were cultured with SE medium in concentric-tube photobioreactor. Cultures in the photobioreactor were aerated intermittently with simulated flue gas which contains different concentration of CO₂（5%,10%, 15% and 20%）. After 17 days of cultivation, the cell concentration（8.76×106 cells·mL-1） and CO₂ fixation rate（30.18mg?L-1?d-1） of Chlorella vulgaris were highest in simulated flue gas with 10%CO₂.In conclusion, it’s efficient to improve the thermal efficiency of heating system by reducing the heat loss of boiler and pipe networks; the thermal efficiency of boiler would be increased through optimizing the operation parameters, such as the air flow、fuel particle、bed temperature、boiler load; the potential capacity of Chlorella vulgaris would be better when in simulated flue gas with 10%CO₂.