Experiment On A Circulating Fludized Bed Multi-Generation System

Coal is the main energy resource in China. The resources of bituminous and lignite with high volatile content comprise up to the main part of coal reserves. Circulating fluidized beds multi-generation technology can combine pyrolysis. gasification and combustion in a hybrid process according to different compositions of coal. But multi-generation system is in developing stage. The gas production rate is low and tar content is high in the multi-generation system on the basis of pyrolysis in the existing system. Although the multi-generation system on the basis of partial gasification can produce more gas, the gas calorific value is low.A new circulating fluidized bed multi-generation system is presented in the thesis. A combustor and a gasifier are connected in parallel and a little air is added into the gasifier as reagent. In the gasifier, the coal-air reaction can raise the gasifier temperatures and the gasification efficiencies, reduce the tar content in gas. The gas calorific value can keep high as the air is a little.Based on the concept of the multi-generation, a cold model with a combustor of 100 mm in diameter and 3000 mm in height, a gasifier of 200 mm in diameter and 900 mm in height is built. The experiment results show that the differential pressure between the inlet and outlet of the loop seal has effect on the sand returning characteristic. The differential pressure between combustor and gasifier is a key factor to the system stability and must be monitored in test. When inventory in the gasifier is fludized, the pressure drop can be used to monitor material level.Based on the cold tests, a hot test rig, which has the same size as the cold model, was built. Gasification tests on Shenhua bituminous, Longkou lignite and Datong bituminous were made. The results show that all the tests can keep stable. The effect of operation conditions, such as coal, coal feed rates, air/coal ratios, on gas composition, calorific value, carbon conversions and gasification efficiencies are analyzed. In the investigate range, the maximum gasification efficiency is 48 % and the calorific value is 10.7 MJ/Nm~3 for Longkou lignite, 31.7% and 10.1 MJ/Nm~3 for Shenhua bituminous, 31.4% and 7.9 MJ/Nm3 for Datong coal, respectively. In the gas from Longkou lignite and Datong bituminous, there is little tar. The tar production rate is about 1.5% for Shenhua bituminous.Analysis and calculation shows that pyrolysis gas is main part of the gas, the gasification efficiency is higher than a multi-generation system on the basis of pyrolysis and tar content of gas is less.