Abstract
Abstract: As an important way of straw comprehensive utilization, straw bales combustion has the advantages of low cost, high efficiency, low pollution and better adaptability of raw materials. However, there still exist the problems such as low combustion efficiency, complex flue gas purification and low automation of straw bales combustion. Based on the combustion theory of raw material classification and air distribution classification technology, we designed the secondary air distribution device, which consists of two combustion chambers. In the first combustion chamber, a primary air was provided to ensure gasification reaction. In the second combustion chamber, a secondary air was provided to ensure gas combustion, which realized the full combustion of straw. At the same time, we developed a dust removal device and the intelligent control system, and built a straw bale boiler test platform, which realized real-time control of bale burning and data acquisition. The design power of the boiler was 230 kW, the fuel consumption was 60 kg/h, and the overall dimension of the trial boiler was 3 026 mm×2 178 mm×2 407 mm; the boiler could be filled with small square bundles and large round bundles, the overall dimension of small square bundles was 700 mm×450 mm×350 mm, 24 bundles could be filled at a time, and the overall dimension of large round bundles was 1 200 mm×1 300 mm, and one round bundle could be filled at a time. The boiler mainly included primary combustion chamber, primary air distribution chamber, secondary combustion chamber, secondary air distribution and baffle dust remover. The flue gas purification and dedusting device mainly included electrostatic dedusting, cyclone dedusting, circulating spray and sewage purification and reuse device. The intelligent control system mainly included human-computer interaction system, furnace pressure control system, furnace temperature control system, intelligent air distribution system and temperature warning system. When the equipment works, we could open the boiler control system and air distribution system after loading the raw materials, set the furnace temperature as 800 ℃, furnace pressure as 10 Pa, and the furnace temperature would reach a stable state about 15 minutes after manual ignition. At this time, the flue gas emission test and boiler heat balance test were carried out, and the test duration at the stable state was 3 hours. Tested with corn stalk as raw material, the result showed that the thermal efficiency of straw-fired boilers was 84.6%, the heat load was 230 kW, the average concentration of soot emissions was 19.8 mg/m3, the concentration of NOX was 133.6 mg/m3, and the concentration of SO2 was <3 mg/m3, which met the requirements of (GB13271-2014). Taking this boiler as an example, the annual heating fuel cost was 10.8-14.4 yuan/m2, which had an advantage in heating costs, and had a good benefit for environmental protection compared with coal heating and biomass pellet heating. The intelligent combustion platform also can carry out various process tests, and the next step is to carry out combustion tests under different working conditions and explore different combustion processes, which can provide a basis for further optimization.
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