Zhenglun Shi

A preliminary study on zero solid waste generation from pulverised coal combustion (PCC)

How to completely utilise the solid residues from pulverised coal combustion (PCC) has been a hard problem so far. On the basis of a first feasibility analysis and a preliminary experimental research, this study creates an innovative idea how to realise zero generation of solid waste from PCC. By adding some quick lime as well as some other mineralisers to the coal and grinding together before combustion, the mineral composition and property of ashes could be changed significantly. The formation of some cement minerals, such as Belite, would convert the ashes from solid waste into a kind of product that is similar to cement clinker. And this technology would have great effect on energy utilisation as well as environmental protection.

Influence of acid leaching and calcination on iron removal of coal kaolin

Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) demonstrated that 900°C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin (RCK), whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin (CCK). The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using Mössbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900°C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.

Experimental study on cement clinker co-generation in pulverized coal combustion boilers of power plants.

The idea to co-generate cement clinker in pulverized coal combustion (PCC) boilers of power plants is introduced and discussed. An experimental study and theoretical analysis showed this idea to be feasible and promising. By adding quick lime as well as other mineralizers to the coal and grinding the mixture before combustion, sulfoaluminate cement clinker with a high content of silicate (SCCHS) could be generated. The main mineral phases in SCCHS are 2CaO · SiO2 (dicalcium-silicate), 3CaO · 3Al2O3 ·CaSO4 (calcium-sulfoaluminate) and 2CaO · Al2 O3 ·SiO2(gehlenite). Performance tests showed that the SCCHS met the requirements for utilization in common construction. Based on this idea, zero solid waste generation from PCC would be realized. Furthermore, thermal power production and cement production could be combined, and this would have a significant effect on both environmental protection and natural resource saving.

Development of Gas Steam and Power Multi-Generation System

A new system using combined coal gasification and combustion has been developed for clean and high efficient utilization of coal. The coal is first gasified by air/steam or recycle gas and the produced fuel gas is then used for industrial purpose or as a fuel for gas turbine. The char residue from the gasifier is burned in a circulating fluidized bed combustor to generate steam for power generation. A 1MW pilot plant test facility has been erected, which consists of a fluidized bed gasifier, a CFB combustor, flue gas and fuel gas clean and cool system, data acqisition and control system. The primary results show that the system can produce 12–14MJ/Nm3 middle heating value gas by using recycle gas or steam as gasification mediaand bed temperature and solid circulation rate are main parameters. On bases of this, a 25 MW gas steam and power multi-generation system has been designed. In this system, a fluidized bed gasifiers are combined with a 130t/h circulating bed boiler to realize gas and steam cogeneration. The system can produce 7800 M3/h gas with heating value 10–14 Mj/Nm3 and 25 MW Power.Copyright

Recycling Coal Gangue as Raw Material for Portland Cement Production in Dry Rotary Kiln

Coal gangue (CG) is one of industrial solid wastes with biggest discharging. The disposal of such a large quantity of this solid waste requires lots of land and many serious environmental problems have been occurred. In this paper, CG as one of cement raw materials, and production experiments were performed in a 5000t•d-1 dry process rotary kiln to calcinations Portland cement clinker. The thermo gravimetric analyses, ash melting point test, X-ray diffraction (XRD), chemical composition of CG were measured. Utilization CG as clay for cement raw meal preparations, and a study was done for calcinations clinkers and test their performance and so on. The results revealed that CG can replace clay for Portland cement. The average output of clinker per day was increased 8.23%, and the usage of the standard coal was decreased 3.94%. The technology reference provide for CG can widely use in cement industry.

The Physical and Chemical Properties of Fly Ash from Coal Gasification and Study on Its Recycling Utilization

Aiming at the difficulties in utilization of fly ash from coal gasification, the physical and chemical properties of fly ash were investigated. This research studied recycling utilization on using fly ash as one of cement raw materials for cement clinker. Results showed that fly ash belongs to ordinary solid waste of siliceous and aluminous materials. Cement clinker could be generated by substituting fly ash for shale with different type limestone. The study not only solves the environment pollution problem caused by piling of fly ash, but also realizes its recycling utilization.

Combustion Behavior and SO2, NOx Emissions of an Anthracite Coal in a Circulating Fluidized Bed

Combustion behavior and SO2 , NOx emissions of anthracite coal in a circulating fluidized bed are reported in this paper. Experimental researches were done on a 1 MWt circulating fluidized bed facility with a 0.31 m × 0.31 m cross section and 11.2 m height combustor. The anthracite coal with 6.28% volatile and 3.76% sulfur content burns steadily during the test. The bed was operated under different temperature, Ca/S ratio and excess air. A limestone containing 75% CaCO3 and 15% MgCO3 was used as the sulfur sorbent. Results show that the SO2 emission varies with operating bed temperature and more than 90% sulfur capture efficiency can be reached while Ca/S is about 3. With Rosemount Analytical NGA2000, N2 O, NO and NO2 were also measured in the test. It was found the majority content of NOx was NO and the least was NO2 . Those NOx emissions change highly with the excess air number.Copyright

Evaluation of coal gangue and ash for calcined kaolin preparation

For comprehensive utilization of solid waste, coal gangue, slag of CFB and washed fly ash provided by a coal mine were evaluated on their potential as calcined kaolin. Studies on these samples include the determination of chemical composition by ICP, the analysis of mineralogical construction by XRD, orthogonal experiments of iron leaching by acids and decarburization by calcination. Results show that the chemical compositions of three samples are very close to the kaolinite and their mass ratios of SiO2 to Al2O3 are all about 1.4:1. The major crystalline phase presented in the coal gangue is kaolinite, while an obvious band of amorphous materials are found in others since they are combustion products, but none of them is in exception of layer structure observed though SEM. Orthogonal experiments of iron leaching by acids reveal that the maximal iron leaching rate and product-calcined whiteness of the coal gangue are 63.59% and 68.54% respectively. For that of the slag of CFB, they are 39.74% and 40.55%, while for that of the washed fly ash, they are 31.58% and 45.92%. Thus, it can be inferred that this coal gangue can better fulfill the preparation of high-quality calcined kaolin.