Clean Ash Research Articles

Quality of edible bird’s nest treated by keratinolytic enzymes-based cleaning solution

Edible bird's nest (EBN) is one of the luxury foods that is widely used as a healthy food due to its nutritional value and therapeutic benefits. The traditional EBN washing process causes a reduction in weight and nutrient content and an increase in pollutants due to the use of hydrogen peroxide. An exploratory observation method was used to examine the quality of EBN from Collocalia fuciphaga before and after washing using a washing solution based on keratinolytic enzymes. There are four stages of EBN cleaning i.e. cleaning by tap water, ethanol solution, enzyme solution at room temperature and 50oC and drying at 40oC for 42 hrs. A total of 60 EBN (unclean, n = 30) and clean, n = 30) were analyzed using the AOAC method. The mineral content of Ca, Fe, K and Mg using atomic absorption spectrophotometry (AAS) except that P was measured by spectrophotometer. A carbohydrate estimation kit was used to measure glycoprotein content and the amino acid content was determined using the HPLC method. Evaluation of the cleanliness was carried out using a scoring system by semi-trained panelists. The results obtained showed that the clean EBNs were slightly yellowish-white in color, and the cleanliness of EBN before and after cleaning increased from 2.35 to 3.84. Clean EBN protein content decreased by 7.2% while total amino acids decreased from 38.51% to 32.71%. Clean EBN contains eight essential amino acids of 17.93% with high levels of leucine, valine, arginine, and threonine (2.42-2.96%). EBN's clean ash content increased from 3.7% to 7.8%. Carbohydrate content and iron in clean EBN were 39.19±0.76% and 14.35 mg/100 g dry matter, respectively. The high levels of carbohydrates and iron appear to be good sources of glycoprotein to support health and have the potential as an alternative source of iron for people with anemia. The stepwise EBN washing method using tapwater, ethanol and a washing solution based on keratinolytic enzymes can be applied to reduce weight loss and improve the quality of EBN.

Flotation response of coal washery reject fines: Characteristics, process optimization, and oxidation

AbstractThe present paper outlines the characterization, electrokinetic behaviour, and flotation response of rejected coking coal fines with 32.5% ash generated in a coal washery in Eastern India. The response methodology and central composite rotatable design (RSM‐CCRD) were used for the process modelling and optimization of the flotation process using diesel, methyl isobutyl carbinol (MIBC), and sodium hexametaphosphate as a collector, frother, and depressant to maximize ash reduction, yield, and combustible recovery. At optimum condition, a 9.7% clean ash coal was achieved with a 63% yield at collector, frother, and depressant dosages of 0.78, 0.31, and 0.80 kg/ton, respectively. The model prediction and experimental data corroborated sufficiently. Subsequently, within 1 year, the fines oxidized and did not float with the collector. Fourier‐transform infrared spectroscopy (FTIR) confirmed surface oxidation on oxidized coal. The oxidized coal responded favourably to acid oil, a vegetable oil refinery waste. With acid oil as a collector, the oxidized coal can upgrade to 12% clean ash coal with a 60% yield; the combustible recovered is 80%. The work indicates successful upgradation of fresh and oxidized coal using the froth flotation process.

Influence of particle size range on coal fly ash triboelectrostatic separation

ABSTRACT Triboelectrostatic beneficiation, a dry separation technology recurred to electrification properties between carbon and ash, is employed to remove unburned carbon from coal fly ash effectively. Previous works showed that the efficiency of triboelectrostatic separation was influenced by particle size of fly ash. However, the effect of specific particle size range on triboelectric separation efficiency has not received appropriate academic attention. In this paper, a model of charge-to-mass ratio (CMR) which varied with particle sizes was established by Engineering Discrete Element Method (EDEM); on this basis, the effect of particle size range on triboelectric separation of fly ash was studied via screening before and after separation. Based on the Change rule of high loss-on-ignition (LOI), yield, CMR, LOI decrease rate of clean ash (LDC) and LOI increase rate of tailing (LIT), the results were obtained and shown as follows: carbon and ash can be separated efficiently when the particle size is between 38 ~ 74 μm; separation effect is deficient when the particle size is smaller than 38 μm due to insufficient depolymerization of the particles and CMR decrease. This indicates that the separation effect of triboelectric separation is not negatively correlated with particle size. Instead, there is an appropriate optimal separation range. Triboelectrostatic separation efficiency can be improved by screening fly ash in the narrow particle size under 74 μm, and the separation effect of narrow size grain samples obtained after screening is better than the full-size grain ones. Therefore, the fly ash should be screened properly before separation.

Optimization of process parameter of tribo-electrostatic separator for high ash non-coking coal preparation using response surface methodology

ABSTRACT Tribo-electrostatic separation of low-grade non-coking coal with 39–41% ash was optimized using response surface methodology at 50 kg h−1 feed rate. The petrographic and SEM-EDAX analysis reveals that coal has difficult liberation characteristics. The optimum condition to minimize the ash content of the coal was 20% relative humidity, 120 s tribo charging time, and 24.75 kV DC voltage. It is possible to achieve 32.7% clean ash coal with 59% yield from a 41% feed ash coal. The combustible recovered at these conditions was 67.4%. The experiment results corroborated well with the estimated value of 9% ash reduction from the coal.

The Characterization of Flotation Selectivity of Different Size Coal Fractions

ABSTRACTTo investigate the selectivity of different size fractions in the flotation process, the Fuerstenau upgrading equation was used to fit the results of flotation kinetics of various size fractions and to evaluate the flotation selectivity. The hydrophobic and hydrophilic functional groups on the surface of coal of different size fractions were analyzed quantitatively by Fourier Transform Infrared (FTIR) Spectroscopy, and a hydrophilicity index (HI) was defined. The difference in the values of HI was also applied to assess the flotation selectivity. The results show that the fitting constant k from the Fuerstenau upgrading equation is positively correlated to the flotation selectivity. The constant k values of the three size fractions are as follows: 3.16 for 0.25–0.125 mm, 2.86 for 0.125–0.074 mm, and 2.03 for –0.074 mm. It reflected that the selectivity of the coarse size fraction was the best, followed by the medium size fraction, and the selectivity of fine size fraction was the worst. The required clean ash content of 12% was achieved at a separation density of about 1.6 g/cm3. The difference in the HI values between 1.4–1.6 g/cm3 and > 1.6 g/cm3 determine the selectivity. The greater the difference in the HI values is, the better the selectivity is. The difference in the HI values were 1.2195 for 0.25–0.125 mm, 0.8327 for 0.125–0.074 mm, and 0.5873 for –0.074 mm, which is consistent with the results obtained using the Fuerstenau upgrading equation to characterize the selectivity of coal slime.

Application of a Shewhart control chart to monitor clean ash during coal preparation

Abstract In coal preparation, clean coal ash content is a key indicator for evaluating the quality of clean coal. Online ash analysers are employed to rapidly measure the clean ash, and the resulting measurements are monitored for productive process control. However, the ash observations often fluctuate and are disorganized due to random errors and analyser measurement errors, local variations in coal flow, and changing equipment and processes. Thus, this paper attempts to use the Shewhart control chart method to monitor clean ash in a statistical and global manner. From investigations of the coal preparation process, three types of variability can occur in ash process data: random variability, special variability and systemic variability. An effective X − -Shewhart control chart can detect all abnormal variations under the condition that the control chart parameters (subgroup and control limits) are properly determined. To achieve this, an error analysis of an ash analyser and the influence of data autocorrelation were considered before structuring a clean ash control chart. In phase I, a preliminary dataset was collected from actual ash observations. After an autocorrelation analysis, which excluded abnormal variations, a sampling scheme comparison and the selection of a population standard deviation for the preliminary data, the control chart parameters were precisely estimated. In phase II, the phase I analysis procedure was broadly used to structure a X − chart with given standard values for monitoring clean ash. Therefore, an application example is presented, and the results are discussed to demonstrate the positive impact of this method on a coal preparation plant.

A New Technique for Removing Unburned Carbon from Coal Fly Ash at an Industrial Scale

Removal of unburned carbon from the high-carbon fly ash (HCFA) is essential when it is used as an admixture in cement concrete. This article deals with processing of the HCFA from the Guangdong province of China. A cyclonic-static microbubble flotation column (FCSMC), a novel device with the characteristics of internal recycling process and multiple mineralization steps, was used to separate unburned carbon from ash materials. A commercial flotation plant with a handling capacity of 110 ton coal fly ash (dry basis) per hour was set up. Using the optimum operational parameters, a clean ash with loss on ignition (LOI) of 3.08% and a removal rate of unburned carbon (RUC) of 80.41% was obtained. The calorific value of the unburned carbon products reached 3534 cal/g. Industrial-scale flotation tests on the circulation pulp pressure demonstrated that the energy input mode and internal recycling process of FCSMC separator was effective in removing unburned carbon from HCFA.

A Techno-Economic Analysis Method to Determine Yield and Ash of Coal Preparation Products

A techno-economic optimization-oriented analysis method was proposed to determine the optimal yield and ash of coal flotation concentrate, thus maximizing the economic benefits. With the kerosene and No. 2 fuel oil used as flotation agents and lots of flotation tests done, the allowable dosage ranges of the two agents were determined, then two regression models were developed through orthogonal tests to determine the ash and yield of clean coal by using the software of MATLAB. According to the relation between price and concentrate ash, an optimization model was developed and, as a result, the software of LINGO was used to determine the optimal clean ash and yield, that is, 9.93% and 79.91%, respectively, by which the max income of per 100 t of raw fine coal came up to 106,221 RMB. Exemplification results showed that the method proposed is simple and practical.

Unburned carbon removal effect on compressive strength development in a honeycomb briquette ash-based geopolymer

The potential of honeycomb briquette ash as a new source material for the manufacture of geopolymers was examined. The successful geopolymerization of honeycomb briquette ash was attained by means of NaOH treatment. The concentrations of the major and minor elements of honeycomb briquette ash are in the normal range of the chemical composition of fly ash and appropriate for the synthesis of geopolymers. Honeycomb briquette ash contains 9.88 wt.% unburned carbon, however, all but 0.04% of the unburned carbon was removed in clean ash by means of a froth flotation process. The development of the compressive strength of the geopolymer bodies is affected by the unburned carbon content, the molar concentration of the NaOH solution, the curing temperature, and the curing time. With a few exceptions, a high compressive strength was achieved for the unburned carbon-free ash-based geopolymer bodies regardless of the curing temperature and the curing time. A geopolymer body was prepared by the dissolution of unburned carbon-free ash in 12 M of NaOH solution and curing at 80 °C for 7 days. Under these conditions, the compressive strength of the geopolymer body increased to 65.63 MPa. This value is almost double the highest value of a geopolymer body, prepared by the dissolution of as-received ash in 12 M of NaOH solution and curing at 80 °C for 28 days. In conclusion, unburned carbon-free honeycomb briquette ash could be an alternative to Portland cement as a prospective cementitious material.

Research and application of a new emulsified collector on flotation

Abstract Using a new type of emulsified flotation reagent ZFC for flotation research of Qianjiaying and Huaixiao coal samples, experimental results show that the reagent has excellent performance, good stability and high selectivity, which promotes the coal flotation. Compared with the flotation with diesel at the similar clean ash content, the ZFC can increase clean coal recovery and combustible material recovery of 0.39%-14.75% and 0.36%-17.52%, respectively. The dosage of ZFC is less than the used diesel oil and the oil saving rate reaches up 70%. The flotation mechanism of ZFC was also studied by measuring the wetting heat and Zeta potential.

Processed Low NO<sub>x</sub> Fly Ash as a Filler in Plastics

Fly ash generated from low NOx burners at American Electric Power's Glen Lyn facility was beneficiated to remove residual carbon, magnetic particles, and cenospheres. The clean fly ash had a mean particle size of about 30 microns, which is coarser than typical commercial fillers used in plastics. To obtain a finer sized fly ash, air classification was used to separate the clean fly ash into its coarse and fine fractions. The resulting fine fraction had a mean particle size of 4.13 microns and accounted for 16.7 wt% of the total clean ash. The brightness of the clean ash was also less than that of typical commercial fillers and efforts to improve the brightness proved unsuccessful. The resulting fine ash was then coated with a silane coupling agent and then added to polypropylene, low density polyethylene, and high density polyethylene at various levels. These mixtures were in turn used to make tensile test specimens by injection molding. For comparison, a commercial CaCO3 filler was also tested under the same conditions. The mechanical properties of these specimens were determined and the results show that the polymers containing fly ash as a filler have equivalent properties to those same polymers when commercial fillers are used in most cases.

Unburned Carbon from Fly Ash for Mercury Adsorption: I. Separation and Characterization of Unburned Carbon

In searching for a low cost adsorbent for mercury removal from flue gas, this study focuses on the utilization of unburned carbons from fly ash as the substitute material for the costly activated carbons. In this first paper of the series, various separation technologies are introduced for the extraction of unburned carbon from different sources of fly ash. The unburned carbons have been efficiently separated from clean ash, which is a value-added product for the concrete industry, with the separation technologies such as gravity separation, electrostatic separation, and froth flotation. Carbon concentrate with a LOI (Loss On Ignition) value of 67~80% has been generated from the processes. Characterization of the carbon products has been performed to determine the physical and chemical properties of the material. It has been found that the unburned carbon particles had a porous structure, which is similar to the activated carbon. The BET surface area of these materials was in a range of 25~58m2/g. The majority of the pores are in the range of macropore, and some parts of the surface were embedded with glass spheres. There is a linear relationship between the LOI value and the carbon and sulfur content in the carbon concentrate. Chemical analysis indicated that the mercury content in unburned carbon was much higher than the other separation products, which suggests that the carbon has certain ability to capture mercury from flue gas.

REMOVAL OF UNBURNED CARBON FROM COAL FLY ASH USING A PNEUMATIC TRIBOELECTROSTATIC SEPARATOR

A pneumatic triboelectrostatic beneficiation system of fly ash was studied using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests were conducted to evaluate the charge density and the separation efficiency at various operating conditions. It was found that the higher charge densities were obtained at [1] the air flow rate of 1.75 m3/min, [2] the feed rate of less than 50 kg/h, and [3] the relative humidity of less than 30% with use of a stainless ejector tribocharger. With these optimum conditions, the clean ash of less than LOI 3% was recovered with a yield over 75% when operated at the diffuser slit gap of 4 mm, the diffuser outlet velocity of 16.1–18.6 m/s, and the distance of 15 cm between diffuser slit and splitter. The optimum feed rate was found to be 740 kg/h per m2 of electrode surface area, which can be used as a scale-up factor of electroseparator.

Tribo-electrostatic beneficiation of fly ash for ash utilization

The study was conducted to obtain the scale-up factor and the optimum design criteria for the development of a commercial scale electrostatic separator using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests of the charge density and separation efficiency to study the removal possibility of unburned carbon from coal fly ash were evaluated under various operating conditions. It was found that the experimental conditions for obtaining the maximum charge density were an air flow rate of 1.75 m3/min and a feed rate of less than 50 kg/hr when operated at lower than 30% relative humidity using a SUS304 ejector tribocharger. Also, the optimum instrument conditions for recovering the clean ash with less than LOI3% at yield over 65% when operated at above experimental conditions were found to be a diffuser slit gap of 4 mm, and a distance between diffuser slit and splitter of 15 cm. Overall, the feed rate per unit electrode surface area was about 0.074 kg/cm2 hr, which can be used as a scale-up factor of the electroseparator.

97/01887 Artificial soil manufacture from fly ash and/or clean ash

97/01887 Artificial soil manufacture from fly ash and/or clean ash

Fine Coal Cleaning by Spiral and Water Washing Cyclone

The performance of three different types of spirals and a 200 mm diameter water washing cyclone have been assessed in open-circuit on-site testwork at the Norwich Park preparation plant on nominally 500 µ x 75 µm sized coal. The study is part of a program investigating alternative methods to heavy media cyclones and froth flotation for removing ash from fine coal from Central Queensland mines in the nominally 3 mm x 75 µm size range. The two spirals specifically developed for treating fine coal showed better cleaning efficiencies than the water washing cyclone on the +75 µm size fraction in the feed (essentially 1 mm top size). Their single start capacity was about half that of the water washing cyclone for the same clean coal ash content. The spirals readily produced a high ash reject (> 81%) in a single stage and, with the appropriate splitter configuration, a small middlings suitable for retreatment. Middlings splitter setting and vortex finder position (for the water washing cyclone) both provided reasonable control of clean ash at intermediate solids feed rates. For the spirals there was a strong correlation between solids feed rate and both clean coal ash content and yield at constant middlings splitter setting. For small cuts to middlings, separation efficiency remained relatively constant over the full range of feed rates. Relative density partition data indicated that less size classification took place in the spirals although the efficiency of both processes decreased sharply below about 125 µm. For a given clean coal ash the capacity and/or recovery of the spirals and water washing cyclone depended on tshe proportion of -75 µm high ash slimes in the feed.