Effects of nitrogen oxides, sulfur dioxide, and ferric ions on the corrosion of mild steel in concentrated sulfuric acid

1980 ◽  
Vol 11 (8) ◽  
pp. 1421-1428 ◽  
Author(s):  
Terrell N. Andersen ◽  
Naola Vanorden ◽  
W. Joseph Schlitt
Keyword(s):  
Sulfuric Acid ◽  
Sulfur Dioxide ◽  
Nitrogen Oxides ◽  
Mild Steel ◽  
Ferric Ions ◽  
Concentrated Sulfuric Acid

scholarly journals Process features of neutralization of technical sulfuric acid with natural limestone

2019 ◽  
Vol 58 (4) ◽  
pp. 110-118
Author(s):  
Sergey A. Vzorodov ◽  
◽  
Anton M. Klyushnikov ◽  
Keyword(s):  
Sulfuric Acid ◽  
Sulfur Dioxide ◽  
Ph Value ◽  
Continuous Process ◽  
Pulp Density ◽  
Internal Diffusion ◽  
Sulfur Dioxide Emissions ◽  
Sulfuric Acid Plant ◽  
Concentrated Sulfuric Acid ◽  
Neutralization Time

The work was devoted to the solution of the environmental problem associated with the disposal of sulfur dioxide emissions from metallurgical production at the Nadezhda Metallurgical Plant (Norilsk, Norilsk Nickel PJSC). For utilization of sulfur dioxide it is planned to build a sulfuric acid plant. Concentrated sulfuric acid produced at plant is planned to be neutralized with natural limestone. This work presents the results of the study on the neutralization of concentrated sulfuric acid with limestone pulp from the Mokulay deposit (Norilsk). The influence of the following parameters was investigated: limestone consumption, acid dosing rate, limestone pulp density. It is established that the process is limited by the internal diffusion of acid through the layer of gypsum. In order to eliminate internal diffusion process it is advisable to carry out neutralization in a periodic mode by introducing a strictly measured amount of acid into an excess amount of limestone pulp. This process allows one to speed up the process of neutralization in 3-3.5 times and achieve a higher value of the final pH of the pulp comparing with continuous process. Carrying out the process in the periodic way also makes it possible to achieve the complete absence of the release of acidic off-gas during neutralization. The optimal values of neutralization parameters were determined as the following: limestone pulp density was 11-12%, acid delivery time was 40 minutes, neutralization time was 20 minutes, and final pH value was at least 6.5, while the limestone feeding was an excessive by 22-28% from stoichiometry. It was shown that an increase in the limestone pulp density is impractical because it will lead to an increase in the duration of neutralization, as well as to a sharp increase in the viscosity of the gypsum pulp. That, in its turn, makes gypsum pulp difficult to flow from the neutralization apparatus. It was recommended to filter the resulting pulp in order to obtain a gypsum cake with a moisture content of about 55%. It was recommended to store cake on a special site. A flowsheet has been developed and process schedules have been implemented for the design of a neutralization plant with a capacity of up to 2 million tons technical sulfuric acid per year.

Trapping nitrous gases during nitric acid leaching of sulfide concentrates

2021 ◽  
pp. 29-36
Author(s):  
E. Yu. Meshkov ◽  
N. A. Bobyrenko ◽  
I. A. Parygin ◽  
A. A. Soloviev
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Nitrogen Oxides ◽  
Nitrogen Oxide ◽  
Acid Leaching ◽  
Process Water ◽  
Nitric Acid Leaching ◽  
Concentrated Sulfuric Acid ◽  
Sulfide Concentrates ◽  
Nitrous Gases

Gas-air mixtures that form in nitric acid leaching of sulfide raw materials possess the following peculiarities making a negative impact on trapping of nitrogen oxides: elevated temperature, different oxidation level of nitrogen oxides, slow oxidation of NO in region of low concentrations, and instability of the resulting gas-air mixture flow. Therefore, well-known methods of trapping nitrous gases shall be adapted to specific sulfide raw material. We propose a process flow diagram for trapping nitrous gases formed during nitric acid leaching of sulfide concentrates at atmospheric pressure on the example of Zhezkazgan concentrate. The paper addresses theoretical aspects of the use of water-ore pulp, concentrated sulfuric acid, process water and alkaline agents for trapping nitrous gases, and typical reactions of interaction of the proposed absorbents with nitrogen oxides. The choice of water-ore pulp as an absorber was made because of similarity between the mechanism of absorption of nitrogen oxides for neutral and alkali ore suspensions and the one for alkali solutions: nitrogen dioxide and nitrous anhydride are absorbed with formation of a solution of nitrates and nitrites. Due to availability in a liquid phase of ferrous iron along with NO2 and N2O3, acidic suspensions are also capable to absorb nitric oxide, to some extent, with formation of Fe(NO)SО4 complex. Process water absorbs only nitrogen dioxide, with formation of nitric and nitrous acids. Nitrous acid is an unstable compound in acidic environments and decomposes with formation of water and nitrogen oxide. At the stages of trapping nitrogen oxides with water-ore pulp and process water (circulating solution), it is recommended conditioning of gas-air mixtures by choosing the volume of additionally introduced air, in an amount to provide the highest rate of nitrogen oxide oxidation. At the stages of sulfuric acid and alkaline trapping of nitrogen oxides, it is recommended conditioning of gas-air mixtures by selecting the volume of additionally introduced air and the oxidation time of nitrogen oxide that provide an equimolecular mixture of NO and NO2. A distinctive feature of the use of water-ore pulp, concentrated sulfuric acid, process water and alkaline agents for trapping nitrous gases is possibility to use the products of absorption at the stage of sulfide concentrate leaching. The extended tests of trapping nitrous gases have been conducted. The plant capacity by the gas-air mixture ranged 17–21 m3/h, and by leached concentrate — 12–15 kg/h. In this case, the degree of capturing nitrous gases reached 96.8%. Return of the products of absorption of nitrous gases in the form of condensate, water-ore pulp, nitrosyl sulfuric acid, nitric acid solution, nitritenitrate lye allows to reduce the nitric acid consumption by 7–10 times relative the values obtained without using the trapping system. In this case, the degree of copper extraction into the leaching solution was 97.7%. The extraction degree of silver, rhenium, zinc was respectively 98.0%, 99.0%; 98.5%.

Gallium Arsenide Integrated Circuits Decapsulation Technique Using Mixed Acid Chemistry For Die-Level Failure Analysis

2018 ◽  
Author(s):  
Harold Jeffrey M. Consigo ◽  
Ricardo S. Calanog ◽  
Melissa O. Caseria
Keyword(s):  
Gallium Arsenide ◽  
Sulfuric Acid ◽  
Nitric Acid ◽  
Integrated Circuits ◽  
Failure Analysis ◽  
Mixed Acid ◽  
Optimum Parameters ◽  
Plastic Package ◽  
Fuming Nitric Acid ◽  
Concentrated Sulfuric Acid

Abstract Gallium Arsenide (GaAs) integrated circuits have become popular these days with superior speed/power products that permit the development of systems that otherwise would have made it impossible or impractical to construct using silicon semiconductors. However, failure analysis remains to be very challenging as GaAs material is easily dissolved when it is reacted with fuming nitric acid used during standard decapsulation process. By utilizing enhanced chemical decapsulation technique with mixture of fuming nitric acid and concentrated sulfuric acid at a low temperature backed with statistical analysis, successful plastic package decapsulation happens to be reproducible mainly for die level failure analysis purposes. The paper aims to develop a chemical decapsulation process with optimum parameters needed to successfully decapsulate plastic molded GaAs integrated circuits for die level failure analysis.

PRODUCTION OF SULFOCATIONITE BY MODIFICATION OF NATURAL COAL WITH CONCENTRATED SULFURIC ACID

2020 ◽  
Vol 3 (441) ◽  
pp. 104-109
Author(s):  
N.A. Bektenov ◽  
◽  
N.C. Murzakassymova ◽  
M.A. Gavrilenko ◽  
А.N. Nurlybayeva ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Concentrated Sulfuric Acid ◽  
Natural Coal
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