Reducing the unburned combustible in the fly ash from a 45,000 Nm3/h Ende Pulverized-Coal Gasifier by applying steam-solid ejector

Abstract

Ejector is widely used in Industry areas. Ende pulverized-coal gasifiers (EPCG) as a type of atmospheric-pressure circulating fluidized bed (CFB) gasifier have been widely used in Gasification field; however, in these, the return conduit of the reactor was generally not equipped with a feedback control device, which led to a part of the flue gas flowing directly from the reactor to the cyclone separator through the return conduit. Such a structure reduced the efficiency of the cyclone separator and increased the unburned combustible in the fly ash and fly ash discharge, which reduced the economic efficiency of the EPCG and increased the generated environmental pollution. This paper presents a method of using steam-solid ejectors as the feedback device to provide a stable pressure barrier. The steam-solid ejector was installed on the return conduit of a 45,000 Nm3/h EPCG. The steam mass flow rate was varied, and the corresponding pressure barrier of the ejector, the temperature and pressure of the reactor, the effective syngas concentration (CO, H2), and the amount of unburned combustible in the fly ash were measured. For a steam pressure of 0.5 MPa and mass flow rate greater than 383 kg/h, the outlet pressure of the Ejector was higher than that at the bottom part of the reactor. In this manner, the pressure sealing of the flue gas flowing directly from the reactor to the cyclone separator through the return conduit could be realized. With an increase in the steam mass flow rate, the pressure barrier and the outlet pressure of the ejector continuously increased; the steam mass flow rate had a linear relationship with the pressure barrier. Compared with the original EPCG, when the steam pressure was 0.5 MPa, the mass flow rate was 617 kg/h, effective syngas concentration increased from 73.3% to 74.5%, and the unburned combustible content in the fly ash decreased from 26.9% to 19.9%.