Hongcang Zhou

Coal Gasification Characteristics in a 2MWth Second-Generation PFB Gasifier

Coal gasification process and equipment feasibility research were carried out in a 2 MW thermal input pressurized spout-fluid bed pilot-scale gasifier and a long-time-run test was performed to study the effects of operating parameters on coal partial gasification behaviors. The test results have demonstrated the feasibility of the gasifier to provide suitable fuel gas and residual char for downstream system of 2G PFBC-CC. The concentration of methane decreased at higher gasification temperature due to the secondary cracking of methane while the carbon conversion increased, and the concentration of hydrogen increased with an increase of steam flow rate. The main experimental results were compared with those of pilot-scale facilities in the world.© 2005 ASME

Study on Pollutants Emission Characteristic of Coal Gasification in a Fluidized Bed Test Rig

This paper presents the results of coal gasification in a fluidized bed test rig of Xuzhou bituminous coal. The diameter of the fluidized bed combustor is 0.1m and the height is 4.22m. The bed temperature is maintained by a method of high temperature flue gas interline heating to overcome high heat losses associated with a oil burner. Test results are reported for variations in the bed temperature, air to coal, steam to coal and Ca to S ratio and their influence on gas yields and desulphurization efficiency. The distribution of polycyclic aromatic hydrocarbons (PAHs) and heavy metal trace elements into the char and syngas are also presented. The molar contents for CH4 and H2 in the coal syngas are found to decrease with increasing air to coal feed ratio from 2.5 to 5, while the content of CO shows little variation. Increasing the steam to coal feed ratio from 0.4 to 0.65 results in all three of the main gas components measured to form a local maximum content at a steam/coal feed ratio of 0.55. The efficiency of desulphurization improves as the ratio of Ca to S, air to coal and the bed temperature are increased, while decreasing with increasing steam to coal feed ratios. The volatile trace element species in decreasing order of relative mass ratio released into the gas phase are Hg, Se, As, Co, Cr, Cd, Cu, and Zn. Besides Hg, Se, and As, for all other trace heavy metals the majority of their mass distribution remains within the char with the proportion contained within char always greater than their combined yields in the coal syngas and slag. The total PAHs in the coal syngas is greater than that contained in the original coal and this indicates that PAHs are formed during the coal gasification process.Copyright

Profiles and TEQ Concentrations of PAHs Emission From Fluidized Bed Coal Gasification

More growing particular attentions are being paid to polycyclic aromatic hydrocarbons (PAHs) generated from coal gasification due to their high mutagenic and carcinogenic. Fluidized bed air and steam gasification of three different rank coals were studied in a bench-scale atmospheric fluidized bed test facility. An extraction and high performance liquid chromatography (HPLC) technique was used to analyze the concentrations of the 16 PAHs specified by US EPA in raw coal, slag, bag house char, cyclone char and fuel gas. The profiles and TEQ concentrations of PAHs emission from fluidized bed coal gasification were discussed. The results indicated that there were mainly three- and four-ringed PAHs in raw coal and fuel gas, but the total PAHs in bag house char and cyclone char were dominated by three-, four- and five-ringed PAHs. The concentrations of three-ringed PAHs in fuel gas were higher than those of four-ringed PAHs, but a reverse phenomenon occurred in bag house char and cyclone char. No PAHs were measured in slag during coal gasification. The total TEQ concentration of five-ringed PAHs mainly dominated in raw coal, fuel gas, bag house char, and cyclone char, and their percentages were about 75–96% by weight. Benzo(a)pyrene (BaP) was the main contributor of TEQ concentration in raw coal and gasified products. In addition, the concentration of PAHs in raw coal increased with the rise of coal rank, and there was not an obvious variation about the concentration of PAHs in gasified products.Copyright

Effects of Solid Additives on the Control of Trace Elements During Coal Gasification

Based on the Modified Geo-chemical Enrichment Factor (MGEF), the contents of As, Cd, Co, Cr, Cu, Mn, Hg, Pb, V, Se, Sr, Zn in coal and coal char were analyzed by using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) and Inductively Couple Plasma-atomic Emission Spectroscopy (ICP-AES). Limestone, dolomite and sodium carbonate were studied to control trace elements during coal gasification. Different additives show different performances in the control of trace elements. The adsorbing capacity of coal char to all of trace elements enhances when coal is mixed with limestone and dolomite. Chemical adsorption and physical adsorption of lime, which is decomposition product of limestone under high gasification temperature, are both important for As, Co, Cr, Se and Zn. The effects of limestone on Cd, Cu, Hg, Pb, V and Sr are merely caused by physical adsorption of CaO and the adsorbing capacity to Cd, Cu, V is much stronger than those to Hg, Pb, Sr. Dolomite has stronger adsorbing capacity to most of elements (except Cu, Se, Sr) than limestone. Addition of Na2 CO3 decreases the MGEFs of As, Cd, Cr, Pb and Se while increases the MGEFs of Zn in coal char. Na2 CO3 has little effect on the MGEFs of Co, Cu, Hg, V and Sr in coal char.Copyright