Reuse options for coal fly ash and coal bottom ash are reviewed in this paper. Although, significant quantities of coal fly ash and coal bottom ash are produced worldwide every year, less than 30 % of coal ash produced is reused. Coal ash is mainly reused in civil engineering applications such as road construction, embankments, construction materials, geo-polymer applications and in cement production. Other potential reuse options for coal ash include applications such as glass ceramics, water and wastewater treatment, agriculture as well as for making high value products (e.g. telescope mirrors, break-liners, fire proof products etc.). Considering that only a small fraction of coal ash is reused, other reuse options for commercial applications need to be explored.

Reuse options for coal fired power plant bottom ash and fly ash

An investigation of bottom ash as a pozzolanic material

The utilization of coal bottom ash in civil engineering is one of the most promising options to reduce, or possibly eliminate, the environmental and social problems related to the disposal of bottom ash. This study reviews the traditional and state-of-the-art utilization technologies of bottom ash in the field of civil engineering. It covers the production and characteristics of bottom ash, case studies of its conventional applications as a simple replacement of natural resources and advanced applications for special purposes, and environmental considerations for both raw bottom ash and its applications. This review is intended to stimulate and promote the effective recycling of coal bottom ash in the civil engineering field.

Coal bottom ash in field of civil engineering: A review of advanced applications and environmental considerations

Reviewing the role of coal bottom ash as an alternative of cement

Flow, water absorption, and mechanical characteristics of normal- and high-strength mortar incorporating fine bottom ash aggregates

By-product generation from coal combustion in coal-fired thermal power plants has been increasing worldwide and reached to 125 million tons in the U.S. and 100 million tons in Europe. Coal-fired thermal power plants have a share of about 20% in Turkey's electricity production. Almost 57 million tons of coal with varying ash content of 20–55% was consumed in those plants. Uranium and thorium radioactivity of ashes of low rank coals limits the use of ashes. Consuming local bituminous coals, Catalagzi Thermal Power Station has been producing 0.65 million tons of ash including fly ash (80%) and bottom ash (20%), which have a potential use in civil engineering. The majority of the fly ash has already been used in cement or directly in concrete mortars. This study was aimed to evaluate the bottom ash of the CATES. For this purpose, bottom ash was ground in a pilot scale set including a vertical stirring mill. The set had the controlled feeding, separation, and collection facilities to represent industr...

Stirred Grinding of Coal Bottom Ash to Be Evaluated as a Cement Additive

The structure and particle size of solid fossil fuels have effects on linear or nonlinear movements encountered in breakage rate, besides petrography types, in-organic materials, extensive network of pores, macro chemical forms, etc. Nonlinear breakage behavior in mono size groups of −3,350 + 2,360 μm, −2,360 + 1,700 μm, and −1,180 + 850 μm was a result of heterogeneous structure of the material along with being coarser for grinding medium. The part having low-ash content (coal-like) in the heterogeneous structure was exposed to faster breakage than the part having high-ash content (shale-like). As a result, over-sieve material was composed of shale, which is more difficult to grind, breakage behavior slowed down, and there occurred a deviation in linear breakage behavior with increasing grinding period. Linear breakage behavior in mono size groups of −425 + 300 μm and −212 + 150 μm was considered as a result of homogeneity of the material along with its adequate fineness for grinding medium. Var...

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

The effect of the shape of grinding media on the breakage parameters of colemanite has been investigated in kinetic studies. In this present research, three different monosize fractions, i.e., – 425 + 300 μm, – 300 + 212 μm and – 212 + 150 μm, were used. The grinding media used for the tests were 36.5 × 36.5, 30.1 × 30.1, 25.4 × 25.4, 19.05 × 19.05 and 12.7 × 12.7 mm diameter cylinders, and 36.5, 30.1, 25.4, 19.05 and 12.7 mm diameter balls made from cast iron. The specific rate of breakage (Si) and model parameters (aT, α) were evaluated for the same quantity of cylinders, balls and feed material. The values of Si and the model parameters indicated that a faster breakage rate can be obtained by using cylinders as the grinding media. The size distributions of the products showed that the use of cylinders for grinding offers advantages for relatively coarse feeds. At shorter grinding periods, the product fineness from cylinder grinding was greater than that from ball grinding. However, after progressive grinding, the product fineness of ball grinding eventually exceeded that of cylinder grinding. The overall results indicated that the shape of the grinding media plays a determining role in the overall process.

The Effect of Grinding Media Shape on the Specific Rate of Breakage

The aim of this study was to investigate the grindability of solid fossil fuels from a thermal power plant by using a vertical stirred mill and conventional ball mill. The solid fossil fuel sample was obtained from the Zonguldak Catalagzi thermal power plant in Turkey. The sample below 3350 μm (d80 = 2100 μm) was ground in the laboratory scale stirred mill and ball mill. The d80 sizes of the products at the end of grinding periods of 0.25, 0.50, 1 and 4 min in the stirred mill were determined as 190, 102, 78 and 28 μm, respectively. For this purpose, the stirred mill was used at a stirring speed of 360 rpm and with a 6 mm diameter ball. In the ball mill, the d80 sizes of product after 1, 4, 8, 12 and 24 min of grinding were determined as 1802, 1130, 324, 167 and 81 μm, respectively. The results indicated that grinding by means of a stirred mill was much more efficient than grinding with a ball mill in terms of size distribution of the products. The energy consumption of the product with d80 = 78 μm was obtained as 10.53 kWh/t after 1 min of grinding time in the laboratory scale stirred mill. In the same manner, the energy consumption of product with d80 = 81 μm by using the laboratory scale ball mill was 72.73 kWh/t after 24 min of grinding. It can be clearly seen that the d80 size of the fossil fuel reduced from 2100 μm to 1130 μm after a 4 min grinding period in the ball mill grinding tests. However, the d80 size of the solid fossil fuel reduced to 28 μm after the same grinding time in the stirred mill and it was also possible to efficiently obtain size reduction below 100 μm. However, the ball mill grinding process cannot provide this efficient size reduction for longer grinding times. The ball mill grinding experimental results and simulation results showed that they were fairly consistent with each other. The simulation of higher speed mills such as pin type stirrers has been extensively investigated for relatively small-scale applications by JKSimMet. In this study, the JKSimMet software package was adapted for a stirred mill with the help of the base model of ball milling.

Selcuk Samanli

Papers

Stirred Grinding of Coal Bottom Ash to Be Evaluated as a Cement Additive

An Investigation of Particle Size Variation in Stirred Mills in Terms of Breakage Kinetics

The Effect of Grinding Media Shape on the Specific Rate of Breakage

A Simulation Study of Laboratory Scale Ball and Vertical Stirred Mills