Experimental Study on Preheating and Combustion Characteristics of Semi-coke in 0.2MW Pilot Scale Test Rig

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Title Experimental Study on Preheating and Combustion Characteristics of Semi-coke in 0.2MW Pilot Scale Test Rig
Creator Zhu, J.
Contributor He, K., Ouyang, Z., Lu, Q.
Date 2015-09-11
Spatial Coverage Salt Lake City, Utah
Subject 2015 AFRC Industrial Combustion Symposium
Description Paper from the AFRC 2015 conference titled Experimental Study on Preheating and Combustion Characteristics of Semi-coke in 0.2MW Pilot Scale Test Rig
Abstract Low-rank coal accounts for more than 50% of coal resources in China. Its direct combustion or gasification is not economic to energy efficiency. Utilizing low rank coal in stages is an important way to improve the comprehensive benefits. It means that oil and gas products are firstly extracted through an efficient process and the resultant semi-cokes are then combusted. However, because the semi-coke, almost no volatile, has difficulties in ignition, stabilization, and burn out, realizing high efficient combustion for semi-coke is a difficult problem and become a key research direction. The Institute of engineering thermophysics (IET), CAS has put forward a new process to combust semi-coke in a high efficient way and worked a lot of experiments study in a 30 kW test rig. In order to further investigate the combustion characteristics of semi-coke in high thermal capacity, a 0.2MW pilot scale test rig was built in 2014 in IET, CAS. The test rig consists of preheating system, combustion system and auxiliary system. The preheating system is a circulating fluidized bed with the riser 260 mm in diameter and 1500mm high, and the combustion system is a down-flow combustor (DFC) with 700 mm in diameter and 7000mm high. The semi-coke was firstly preheated to over 800°C by a CFB with the primary air, accounted for 10-30% of the stoichiometric air requirement. In the process of preheating, primary air took reactions with semi-coke and was converted to syngas, including CO, H2 and CH4. The preheating fuel, together with syngas, flows into the the DFC via a nozzle. Air supply to the DFC was staged to optimize performance. The secondary air was supplied from the nozzle, while the tertiary air was introduced at a position 1000 mm below the nozzle to ensure complete combustion. A reducing zone was created between the secondary and tertiary air ports in order to reduce NOx formation. The results showed that the semi-coke can be preheated to 850℃ steadily with primary air ratio of 0.15, and the maximum combustion temperature is about 1200℃ with the temperature difference about 300℃. As a result, the combustion efficiency is 98.8%, and NOx emission is 140 mg/m3 (6% O2). The experimental results can provide a good support for the development and application of semi-coke combustion technology.
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ARK ark:/87278/s6fb9cwm
Setname uu_afrc
Date Created 2018-11-30
Date Modified 2018-11-30
ID 1387826
Reference URL https://collections.lib.utah.edu/ark:/87278/s6fb9cwm