Compacted Non Cement Concrete Utilizing Fluidized Bed And Pulverized Coal Combustion By-Products

The two-part research study presented herein evaluates fresh and hardened properties of vibratory-placed noncement/partial-cement concretes, as well as impact-compacted noncement concretes, containing various dosages of pulverized coal combustion fly ash and fluidized bed combustion spent bed. The results of Part I of this study on vibratory-placed noncement/partial-cement concretes revealed lower early strengths than those of reference concrete, whereas their late strengths (90 and 180 days) were similar to or higher than those of reference concrete. The selected noncement/partial-cement concretes produced higher expansion and lower drying shrinkage than those of the reference concrete. Abrasion resistance of noncement and partial-cement mixtures under dry conditions were better than that of the reference concrete, whereas opposite results were obtained under wet conditions. Laboratory results of Part II on impact-compacted noncement concretes revealed higher compressive strength and resistance to internal sulfate attack with increasing coarse aggregate content. The strength, stiffness, and resistance to abrasion and freezing/thawing of impact-compacted concretes improved with decreases in fluidized bed combustion (FBC) spent bed to pulverized coal combustion (PCC) fly ash ratios, whereas opposite results were obtained for sulfate-induced expansions.

Compared with ordinary Pulverized Coal Combustion (PC) fly ashes, Fluidized Bed Combustion (FBC) ashes have some special properties. The effect of FBC ashes content on the strength of cement mortar was studied, and the physical properties of FBC ashes-cement mortar with 30% FBC ashes were also investigated. The results show that the flexural and compressive strength at 7 and 28 days of the mortar gradually decreases with the increase of FBC ashes content. Under the same dosage, the strength of FBC ashes-cement mortar is greater than that of PC fly ashes-cement mortar. The FBC ashes-cement system presents a normal setting time but poor soundness with more than 3.5% SO3. This work confirms that the properties of FBC ashes-cement system are superior to those of PC fly ashes-cement system when SO3 content is no more than 3.5%.

Comparative lung immunotoxicity of inhaled quartz and coal combustion fly ash

Circulating fluidized bed combustion (CFBC) ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash–cement pastes were studied, and ordinary pulverized coal combustion (PCC) fly ash–cement pastes were used as control. The water-adsorption and superplasticizer (SP)-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash–cement system has greater compressive strength as compared with PCC fly ash–cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash–cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash–cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash–cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.

Author index

Modelling and experimental validation of a fluidized-bed reactor freeboard region: Application to natural gas combustion

Production and characterization of geopolymers based on mixed compositions of metakaolin and coal ashes

Chapter 5 - Fluidized Bed Combustion and Coal Gasification

Limiting NO x and SO 2 emissions from an industrial-size fluidised-bed combustor

The 165 MWe circulating fluidized bed boiler at the Nova Scotia Power Inc. (NSPI) Point Aconi Generating Station, located in eastern Cape Breton Island, Nova Scotia, is Canada’s largest fluidized bed unit. Fluidized bed combustion (FBC) allows the burning of high sulphur (S) fuels with in situ capture of S (removal of SO2). The lower operating temperature of the FBC system (870 C versus 2000 C for pulverized coal boilers) permits the combustion of a wide range of ‘opportunity’ fuels (e.g., petroleum coke , low grade coals, tires, and wood waste sludge) in an environmentally acceptable manner. The use of large amounts of a limestone sorbent in FBC results in a high rate of sulphur capture (90%), however, the rate of residue production is approximately two-times higher than that from conventional pulverized coal-fired boilers. While the residue is currently disposed in a fully engineered residue management site, there are environmental, financial, and other incentives for NSPI to fmd beneficial uses for the residue to minimize placement of the by-product in the landfill.

Experiment and grey relational analysis of seaweed particle combustion in a fluidized bed

The relationship between the tendency of lignites to agglomerate and their fusion characteristics in a fluidized bed combustor

Circulating fluidized bed combustion (CFBC) fly ash has the potential as a precursor to making geopolymer concrete because of its rich silica and alumina content. However, there is a problem in utilizing CFBC fly ash caused by its chemical and physical properties that differ from the widely used pulverized coal combustion (PCC) fly ash. CFBC fly ash has a higher water requirement than PCC fly ash due to its angular particle shape, and higher sulfur and lime contained also caused a different reaction in the geopolymer system. Mechanical activation by milling the CFBC fly ash could decrease the water requirement in the mixture and make good quality CFBC fly sh-based geopolymer concrete. Three CFBC fly ash samples from different power plants in Indonesia with different chemical compositions were used in this research. The first had a low lime and no sulfur content, the second had high lime and no sulfur content, and the third had high lime and sulfur content. The milling process using a ball mill for two hours decreased the water requirement, as shown in the lower normal consistency of the fly ash. The reactivity also was increased, shown by the faster initial setting time. Besides its higher reactivity, lower water requirement increased the compressive strength of geopolymer mortar produced. This study also showed that the existence of calcium and sulfur content in the CFBC fly ash could cause unexpected results shown by the change of initial setting time, water requirement, and compressive strength.

Thermal remediation of oil polluted sands from black tides: The fluidized bed option

Influence of fly ash fineness and shape on the porosity and permeability of blended cement pastes