scholarly journals Generation of sodium cyanide by coal gasification for gold recovery factories

2021 ◽  
Vol 25 (4) ◽  
pp. 488-497
Author(s):  
N. V. Vasyunina ◽  
I. V. Dubova ◽  
S. P. Baksheev ◽  
M. R. Kovel ◽  
V. V. Makarova
Keyword(s):  
Coal Gasification ◽  
Sodium Cyanide ◽  
Gold Recovery ◽  
Production Costs ◽  
Hydrocyanic Acid ◽  
Solution Ph ◽  
Laboratory Setup ◽  
Naoh Solution ◽  
Cylindrical Furnace ◽  
Cyanide Solutions

The aim was to assess the technological feasibility of generating sodium cyanide by coal gasification, to study the effects of the process parameters (temperature, experiment duration, coal type) on the concentration of sodium cyanide in the resulting solutions, as well as to identify optimal modes of the process. Experiments were carried out on a laboratory setup consisting of a tubular cylindrical furnace equipped with a working compartment in the form of a corundum tube. Lignite and charcoal, preliminarily crushed to increase the specific surface area, were investigated. A solution of sodium cyanide was produced by sorption of gaseous hydrocyanic acid (a syngas component) with a sodium carbonate solution. A NaOH solution (pH = 10) installed in an ice bath was used in the system of absorbers. The content of sodium cyanide in the solution was determined by the titrimetric method. The HSC Chemistry 5.1 software package was used for thermodynamic calculations. During the gasification of charcoal in the temperature range 600–800oC, sodium cyanide solutions with a concentration of 0.03–0.08 wt% were obtained. An increase in temperature from 600 to 900oC led to a 4-fold decrease in the concentration of sodium cyanide in an alkaline solution, under the same duration of the experiments. A regression equation was derived for the dependence of the NaCN concentration in solution on the temperature of coal gasification and the duration of the process. It was shown that the generation of sodium cyanide by coal gasification under laboratory conditions yields sodium cyanide concentrations in solution comparable to those used for gold cyanidation at gold recovery plants. The installation of sodium cyanide generation lines directly at the production areas of gold recovery plants will reduce the production costs by eliminating expenses for purchasing, transporting and storing reagents.

A GCC Power Plant With Methanol Storage for Intermediate-Load Duty

1991 ◽  
Vol 113 (1) ◽  
pp. 151-157 ◽  
Author(s):  
J. A. Paffenbarger
Keyword(s):  
Power Plant ◽  
Coal Gasification ◽  
Combined Cycle ◽  
Production Costs ◽  
Plant Performance ◽  
Electricity Production ◽  
Fuel Prices ◽  
Electrical Demand ◽  
Integrated Facility ◽  
Plant Configuration

This paper describes the design and performance of a coal gasification combined-cycle power plant with an integrated facility for producing and storing methanol (GCC/methanol power plant). The methanol is produced at a steady rate and is burned in the combined cycle to generate additional power during periods of peak electrical demand. The GCC/methanol plant provides electricity generation and energy storage in one coal-based facility. It is of potential interest to electric utilities seeking to meet intermediate-load electrical demand on their systems. The plant configuration is determined by means of an innovative economic screening methodology considering capital and fuel costs over a range of cycling duties (capacity factors). Estimated levelized electricity production costs indicate that a GCC/methanol plant could be of economic interest as premium fuel prices increase relative to coal. The plant could potentially be of interest for meeting daily peak demands for periods of eight hours or less. The conceptual plant configuration employs a Texaco gasifier and a Lurgi methanol synthesis plant. Plant performance is estimated at peak and baseload output levels. No unusual design or operational problems were identified.

scholarly journals An alternative low-cost adsorbent for gold recovery from cyanide-leached liquors: Adsorption isotherm and kinetic studies

2018 ◽  
Vol 37 (1-2) ◽  
pp. 3-23 ◽  
Author(s):  
Refiloe Tsolele ◽  
Fanyana Moses Mtunzi ◽  
Michael John Klink ◽  
Vusumzi Emmanuel Pakade
Keyword(s):  
Activated Carbons ◽  
Selective Adsorption ◽  
Low Cost ◽  
Kinetic Studies ◽  
Agitation Speed ◽  
Gold Recovery ◽  
Attractive Alternative ◽  
Solution Ph ◽  
Initial Concentration ◽  
Modified Activated Carbons

Pristine Macadamia nutshell-based activated carbons were chemically oxidized with different concentrations of H3PO4 and HNO3 to increase their surface adsorption properties and further explore if they could be an attractive alternative low-cost adsorbent for gold recovery from cyanide-leached liquors. The modified activated carbons were labeled MACN20, MACN40 and MACN55 to signify the materials prepared from 20%, 40% and 55% (v/v) HNO3, respectively. Similar nomenclature was followed for H3PO4-modified activated carbons. Brunauer-Emmet-Teller, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, elemental analysis and X-ray diffraction spectroscopy were used to characterize the prepared activated carbons. The physical properties were attained through determining attrition, ash content, volatile matter and moisture content of all the activated carbons. Various parameters that affect selective adsorption such as the effect of initial concentration, time, agitation speed, interfering species and the dose of the adsorbent were investigated. Optimal parameters for gold ion adsorption were as follows: solution pH, 10; contact time, 6 h; agitation speed, 150 r/min; sorbent amount, 4 g and initial concentration, 5.5 mg/L. The observed selectivity order was not the same for all the adsorbents, but the adsorption of gold was found to be mostly influenced in the presence of nickel and least influenced by copper. MACN55 was found to be the most efficient adsorbent with 74% of gold adsorption from a real-world sample and displayed a similar performance to coconut-based activated carbons.

A GCC Power Plant With Methanol Storage for Intermediate-Load Duty

1990 ◽  
Author(s):  
John A. Paffenbarger
Keyword(s):  
Power Plant ◽  
Coal Gasification ◽  
Combined Cycle ◽  
Production Costs ◽  
Plant Performance ◽  
Electricity Production ◽  
Fuel Prices ◽  
Electrical Demand ◽  
Integrated Facility ◽  
Plant Configuration

This paper describes the design and performance of a coal gasification combined-cycle power plant with an integrated facility for producing and storing methanol (GCC/methanol power plant). The methanol is produced at a steady rate and is burned in the combined-cycle to generate additional power during periods of peak electrical demand. The GCC/methanol plant provides electricity generation and energy storage in one coal-based facility. It is of potential interest to electric utilities seeking to meet intermediate-load electrical demand on their systems. The plant configuration is determined by means of an economic screening study considering capital and fuel costs over a range of cycling duties (load factors). Estimated levelized electricity production costs indicate that a GCC/methanol plant could be of economic interest as premium fuel prices increase relative to coal. The plant could potentially be of interest for meeting daily peak demands for periods of eight hours or less. The conceptual plant configuration employs a Texaco gasifier and a Lurgi methanol synthesis plant. Plant performance is estimated at peak and baseload output levels. No unusual design or operational problems were identified.

Biological gold recovery from gold–cyanide solutions

2005 ◽  
Vol 76 (1-2) ◽  
pp. 33-42 ◽  
Author(s):  
Timur Aitimbetov ◽  
Daniel M. White ◽  
Indranil Seth
Keyword(s):  
Gold Recovery ◽  
Gold Cyanide ◽  
Cyanide Solutions

Gold Recovery from Aqueous Solutions Using Bioadsorbent Synthesized from Rambutan Peel

2012 ◽  
Vol 506 ◽  
pp. 405-408 ◽  
Author(s):  
T. Rubcumintara ◽  
A. Aksornpan ◽  
W. Jonglertjunya ◽  
W. Koo-Amornpattana ◽  
P. Tasaso
Keyword(s):  
Gold Recovery ◽  
Hydroxyl Groups ◽  
Loading Capacity ◽  
Order Kinetic ◽  
Gold Concentration ◽  
Solution Ph ◽  
Adsorbent Surface ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Ft Ir

The recovery of gold from chloride solutions using bioadsorbent synthesized from waste rambutan peel was studied. The initial gold concentration 25-900 mg/L, solution pH 1-4, temperature 25-60 °C and the amount of adsorbent 1-25 mg were found to affect the efficiency for gold recovery as well as loading capacity. The 99.8 % gold recovery was accomplished in 1 h with loading capacity of 100 mg Au/g adsorbent at the following conditions: adsorbent 25 mg, initial gold concentration 100 mg/L, pH 2 and temperature 60 °C. The decrease of adsorbent from 25 to 1 mg resulted in the highest loading capacity of 2530 mg Au/g adsorbent and 100 % gold recovery within 100 h. The adsorption isotherm as well as mechanism were also elucidated. The Langmuir isotherm and the pseudo second-order kinetic model were fitted well with the experimental results. The activation energy of reaction was calculated to be 31.07 kJ/mol. The mechanism of adsorption is clarified to be the oxidation of hydroxyl groups and reduction of trivalent gold ions to metallic gold on the adsorbent surface which were supported by FT-IR, XRF and SEM.

scholarly journals Assessing possibility of technogenic raw material processing using ultra-low concentrations of sodium cyanide

2020 ◽  
Vol 24 (5) ◽  
pp. 1105-1112
Author(s):  
Anastasia Vasilkova ◽  
◽  
Alexander Byvaltsev ◽  
Olga Khmelnitskaya ◽  
Grigory Voiloshnikov ◽  
...  
Keyword(s):  
Raw Materials ◽  
Sodium Cyanide ◽  
Gold Recovery ◽  
Raw Material ◽  
Ferrous Metals ◽  
Low Concentrations ◽  
Reagent Consumption ◽  
Copper Zinc ◽  
Non Ferrous Metals ◽  
Technogenic Raw Materials

The purpose of the study is to conduct experiments in order to determine the possibility of technogenic gold-bearing raw material cyanidation using ultra-low concentrations of NaCN. Experiments are carried out on the cyanidation of three samples of technogenic raw materials of different composition. The first sample consists of pyrite cinders (Au - 1.8-2.3 g/t, Ag - 13-22 g/t, Fe - 48.52%, Cu - 0.15-0.30%, Zn - 0.3-0.6%). The second sample is represented by the aged tailings of copper-zinc flotation (sample I) with the content of Au - 0.8 g/t, Ag - 7.0 g/t, Fe - 17.2%, Cu - 0.212%, Zn - 0.207%. The next object is the copper-zinc flotation tailings of a concentration plant (sample II), with the following content of Au - 1.22 g/t, Ag - 15.2 g/t, Cu - 0.13%, Zn - 0.23%. It is recommended to use an aqueous wash from non-ferrous metals with subsequent lime treatment as a preliminary processing of pyrite cinders. Cyanidation is carried out at different consumptions of reagent: from 0.075 to 3 kg/t. The experiments have shown that gold recovery in this range of NaCN consumption varies from 42.9 to 44.2%; moreover, a decrease in the reagent consumption allows to reduce the concentration of non-ferrous metal ions in cyanidation solutions. Before cyanidation sample I has also been subjected to aqueous wash to remove acid and non-ferrous metals. NaCN consumption varies from 0.25 to 2.2 kg/t. In this case the extraction of gold amounts to 36.6-46.4%. Cyanidation of tailings (sample II) is carried out in the range of 0.15-1.2 kg/t of NaCN. Gold recovery varies from 24.1 to 30.9%. The cyanidation technology of technogenic raw materials in the field of ultra-low concentrations of sodium cyanide is promising, since it provides acceptable gold recovery under low reagent consumption. For further research in the field of development of an extraction technology of valuable components, the flotation tailings of copper-zinc production (sample II) are chosen as a promising object. It is planned to carry out semi-industrial tests, calculate technical and economic indicators and develop process regulations.

scholarly journals ADSORPTION OF CEFIXIME TRIHYDRATE ONTO CHITOSAN 10B FROM AQUEOUS SOLUTION: KINETIC, EQUILIBRIUM AND THERMODYNAMIC STUDIES

2021 ◽  
Vol 55 (7-8) ◽  
pp. 771-784
Author(s):  
GAZI SALAH UDDIN ◽  
SOMA SAHA ◽  
SUBARNA KARMAKER ◽  
TAPAN KUMAR SAHA
Keyword(s):  
Aqueous Solution ◽  
Aqueous Medium ◽  
Significant Loss ◽  
Solution Ph ◽  
Adsorption Ability ◽  
Naoh Solution ◽  
Pseudo Second Order ◽  
Solution Kinetic ◽  
Kinetic Equilibrium ◽  
Operational Aspects

An efficient and biodegradable adsorbent chitosan 10B was used to eliminate cefixime trihydrate from aqueous solution. The kinetic behavior of cefixime trihydrate adsorption onto chitosan 10B was studied in aqueous medium, from various operational aspects, such as contact time, solution pH, antibiotic concentrations, and temperatures. Cefixime adsorption onto chitosan 10B was confirmed by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). The antibiotic adsorption kinetics obeyed a pseudo-second-order model rather than pseudo-first-order and Elovich kinetic models. The best illustration of antibiotic adsorption equilibrium was made by the Langmuir model, with the highest adsorption ability qm: 37.04 μmol/g at 298 K. The activation energy (Ea) of the present adsorption system was computed to be 44.18 kJ/mol. The values of activation (ΔG‡, ΔH‡ and ΔS‡) and thermodynamic (ΔG, ΔH and ΔS) parameters confirmed that the cefixime trihydrate adsorption onto chitosan 10B in aqueous medium is an exothermic physisorption process. Cefixime desorption from antibiotic-loaded chitosan 10B was performed in 0.1 M NaOH solution and the recycled adsorbent was utilized for a second time without significant loss of its adsorption capacity.

scholarly journals Effect of Lignite Properties on Its Suitability for the Implementation of Underground Coal Gasification (UCG) in Selected Deposits

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5816
Author(s):  
Krzysztof Kapusta
Keyword(s):  
Moisture Content ◽  
Coal Gasification ◽  
Calorific Value ◽  
Process Efficiency ◽  
Average Moisture Content ◽  
Underground Coal Gasification ◽  
Gasification Process ◽  
Laboratory Setup ◽  
Large Bulk

Two experimental simulations of underground coal gasification (UCG) processes, using large bulk samples of lignites, were conducted in a surface laboratory setup. Two different lignite samples were used for the oxygen-blown experiments, i.e., “Velenje” meta-lignite (Slovenia) and “Oltenia” ortho-lignite (Romania). The average moisture content of the samples was 31.6wt.% and 45.6wt.% for the Velenje and Oltenia samples, respectively. The main aim of the study was to assess the suitability of the tested lignites for the underground coal gasification process. The gas composition and its production rates, as well as the temperatures in the artificial seams, were continuously monitored during the experiments. The average calorific value of gas produced during the Velenje lignite experiment (6.4 MJ/Nm3) was much higher compared to the result obtained for the experiment with Oltenia lignite (4.8 MJ/Nm3). The Velenje lignite test was also characterized by significantly higher energy efficiency, i.e., 44.6%, compared to the gasification of Oltenia lignite (33.4%). The gasification experiments carried out showed that the physicochemical properties of the lignite used considerably affect the in situ gasification process. Research also indicates that UCG can be considered as a viable option for the extraction of lignite deposits; however, lignites with a lower moisture content and higher energy density are preferred, due to their much higher process efficiency.

Removal of As, Cr and Cd by Absorptive Filtration

2013 ◽  
Vol 6 (1) ◽  
pp. 73-80 ◽  
Keyword(s):  
Environmental Protection Agency ◽  
Batch Adsorption ◽  
Solution Ph ◽  
Sand Filters ◽  
Bench Scale ◽  
Sand Surface ◽  
Iron Solution ◽  
The Us ◽  
Naoh Solution ◽  
In Series

The US Environmental Protection Agency (USEPA) recently introduced more stringent arsenic regulations by lowering the maximum contaminant level (MCL) to 10 ìg l-1 (ppb) arsenic in drinking water. During the present study, an iron solution injection sand filtration process was designed and tested to selectively remove arsenic (As(V)), chromate (Cr(VI)) and cadmium (Cd(II)) from aqueous solutions down to trace level. Bench scale sand columns with a chemical feeding system were used to conduct the filtration study. The filtration results demonstrate that As(V) could be removed by ferric solution-treated sand filters from 2,000 ìg l-1 (ppb) down to less than 5 ìg l-1 (ppb) using two sand filters connected in series (two stage filtration). During the filtration, ferric concentrations in the first and second filters were maintained at 5 and 2 ppm, respectively, through a continuous injection scheme. Bench scale filtration results suggest that Cr(VI) could also be effectively removed by injection of ferrous solution into the sand columns. Similar ferric treatment of the sand columns also significantly increased Cd(II) removal. Batch adsorption experimental results suggest that when solution pH is lower than 8, arsenate can be removed by iron-treated sand. Arsenate-saturated sand can be regenerated using a high pH (pH > 12) solution. Scanning Electron Microscope (SEM) and energy dispersive x-ray (EDX) studies suggest that very little amount of Fe on the sand surface was dissolved when the sand was regenerated using a dilute NaOH solution (pH = 13).

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