Production Of Caustic Soda Research Articles

Analysis of Influence of Impurities in Hydrogen on PEFC Performance, Based on Measurement of Current Distribution Using Electrochemical Impedance Distribution Analyzer

Polymer electrolyte fuel cells (PEFC) systems have attracted considerable attention in that they can be powered by the hydrogen that is produced as a by-product of various industrial processes, such as caustic soda production and petrochemical processes. Most of the by-product hydrogen is discarded as a waste stream or used for heat production. Therefore, such plants could realize significant energy savings by installing PEFC systems, allowing them to generate power with a high level of efficiency by using the by-product hydrogen to fuel PEFC systems. However, the by-product hydrogen produced by these plants typically contains impurities. Although most of these impurities can be removed, a small amount inevitably remains in the hydrogen and can cause the performance of a PEFC system to degrade. Therefore, the influence of these impurities must be clarified before installing a PEFC system. Given the above, we have been developing a means of quickly evaluating the influence of impurities on a PEFC. The measurement of the current distribution is an important analysis approach that provides information on the local electrochemical reaction conditions in each of the cells of a PEFC. These cells are composed of an electrolytic membrane, a catalyst layer, a diffusion layer, and a flow channel. We have devised a means of measuring the current distribution using current distribution measurement sensors (S++ Simulation Services, Germany) which are inserted between the gas flow channel and current collector of either electrode. This method of measuring the current distribution allows us to quickly analyze the influence of impurities on the PEFC performance, relative to conventional voltage measurements, and can clarify which areas in a cell have degraded because the voltage change is the average of the values for every area in a cell, whereas the current change appears as an absolute value in a local area. Electrochemical impedance spectroscopy (EIS) is a valuable electrochemical analysis tool that can be applied to many kinds of electrochemical devices, including fuel cells. EIS can provide much useful information on the electrolyte membrane, the catalyst layer, and the reactant transfer in a PEFC cell. Although the measurement of the electrochemical impedance distribution in a cell provides a useful means of analyzing the influence of impurities on the PEFC performance, to the best of our knowledge, no previous studies have attempted a high-resolution analysis of the distribution. Therefore, we have developed a new measurement system that enables us to measure both the electrochemical impedance distribution and current distribution. The measurement system is an improved current distribution measurement sensor, intended for application to a JARI-standard cell, with an active area of 25 cm2 and which has 81 segmented internal current shunt resistances for measuring DC current and 81 segmented external connectors for measuring AC current signals. In the present study, to simulate impurities in the hydrogen, we added NH3 (25 ppm) and analyzed its influence on the PEFC performance. We used the measurement system to measure the change in the electrochemical impedance distribution and current distribution over time. The operating temperature, humidification temperatures of the anode and cathode, and current density of the cell were set to 65 ºC, 65 ºC, and 0.3 A/cm2 respectively. The AC current for measuring the electrochemical impedance was 1 Ap-p and the frequency range was 100 mHz–100 kHz. The current distribution measurement (Fig. 1) revealed that the influence of the NH3 was greatest at the inlet to the cell. Furthermore, from the results of the electrochemical impedance distribution measurement, it was found that the current distribution and some aspects of the resistance distribution, as determined from the electrochemical impedance, were correlated. Meanwhile, the most significant factor influencing the effect of NH3 on the PEFC performance is the increase in the activation overvoltage at the inlet of the cell. In addition, it was also thought that the cathode reaction resistance of the cell increases, which is caused by the catalyst-specific surface area decreasing at the inlet of the cell. In conclusion, our new measurement method provides an effective means of determining the largest degraded area and the largest degradation factor affecting PEFC performance, as a result of the presence of impurities in hydrogen. Therefore, relative to conventional measurements, we can quickly evaluate the influence of impurities on the PEFC performance by focusing on and analyzing these areas and factors. In the future, we will apply our new measurement method to the evaluation of the influence of impurities on the PEFC performance by acquiring information on the influence of such impurities on PEFC performance. Figure 1

Evaluating the Thermodynamics and Kinetics of Production of Caustic Soda from Brine

This work is detailed towards ascertaining the thermodynamics and kinetics considerations for the production of caustic soda from brine and soda ash. The thermodynamics considers the Gibbs free energy; which is the minimum electrical work that must be supplied to an electric cell to drive the electrochemical reactions and its relationship with other thermodynamic parameters. The kinetics aspect of this research deduces the reaction rate equations and also predicts via feasible calculations the rate of the reaction, rate constant and order of the reaction. The examination of the thermodynamic analysis shows that the reaction is exothermic, positive value of entropy indicates that there is intrinsic energy which can be converted into work by a perfect electrolytic reaction process. The work determines the extent and the rate of the production process of caustic soda production and as such a pilot plant production of caustic soda from naturally occurring seawater via the diaphragm cell may be developed. The results obtained have shown that the cell potential using the Nerst equation for the production of optimum product caustic soda are: E = 0.5232 volt and the reaction is of second order. The rate of the reaction r=6.264×10−12 mol⋅cm−2⋅s−1 and the rate constant K2=9.2591×10−5cm⋅s−1.

Mercury as a Global Pollutant and Mercury Exposure Assessment and Health Effects

Mercury and its compounds are classified into three main groups: metallic mercury (Hg0), inorganic mercury (Hg2+), and organic mercury (methyl mercury: CH3Hg+, etc.). Metallic mercury is the only metal that is liquid at ambient temperature and normal pressure, which readily forms an amalgam with other metals. Therefore, mercury has long been used for refining various metals, and mercury amalgam has been used for dental treatment. Mercury has also been used in measuring instruments such as thermometers, barometers and blood pressure monitors, as well as electric appliances such as lighting equipment and dry batteries. Large amounts of metallic mercury are still used in other countries as a catalyst in the production of caustic soda by electrolysis. In addition, mercury compounds have been used in various chemicals such as mercurochrome, agricultural chemicals, and mildew-proofing agents. However, the use of mercury has also caused health problems for people. Minamata disease in Japan is a typical example. Also, since mercury is highly volatile, it is discharged as a product of industrial activities or derived from volcanoes, and it has been concluded on the basis of the findings of the United Nations Environment Program (UNEP) that it is circulating globally. Therefore, with the aim of establishing an internationally legally binding treaty for the regulation of mercury use to reduce risk, an intergovernmental negotiating committee was established in 2009. Japan actively contributed to this negotiation owing to its experience with Minamata disease, which led to the Convention on the regulation of mercury use being discharged as the "Minamata Convention on Mercury" and the treaty came into force on August 16, 2017. In this review, we introduce 1) the Global Mercury Assessment by UNEP; 2) mercury kinetics, exposure assessment and toxicity of different chemical forms; 3) large-scale epidemics of methylmercury poisoning; 4) methylmercury exposure assessment and health survey in whale-eating populations; 5) elemental mercury exposure assessment and health survey of mercury mine workers in China.

Reduction of the Corrosiveness of Liquid Wastes of the Production of Chlorine and Caustic Soda

On the example of model solutions (simulators), we study the corrosiveness of hypochlorite-containing waste waters prior to and after their interaction with organic waste waters. It is established that, for low concentrations of hypochlorite, it has a higher corrosiveness than tap water. As a result of the addition of simulators of organic waste waters to hypochlorite-containing waters, their corrosiveness decreases to the level of tap water, most likely due to the neutralization of hypochlorite and the formation of the products of oxidation of organic substances with adsorption properties. For strengthening the interaction of hypochlorite with organic compounds and rapid reduction of the corrosiveness of hypochlorite wastes, it is reasonable to intensify the reactions of oxidation by using catalysts and ultrasonic treatment.

HSP70 (HSPA1) polymorphisms in former workers with chronic mercury vapor exposure.

To investigate 4 loci of 3 HSP70 genes in caustic soda production plant former workers, who have been exposed to metallic mercury vapors for a long time, and including numerous cases of chronic mercury intoxication (CMI). Polymorphisms in HSP70 gene family members (HSP1A1 (+190G/C, rs1043618), HSPA1B (+1267A/G and +2074G/C, rs1061581) and HSP1AL (+2437T/C, rs2227956)) genes were studied among 120 male workers involved in caustic soda production by mercury electrolysis at 2 plants in Eastern Siberia. These subjects had been chronically exposed to metallic mercury vapors for > 5 years and divided into 3 groups based on the occurrence and time of the CMI diagnosis, or absence of this disease. The Group 1 consisted of individuals (N = 46), who had had contact with mercury but were not diagnosed with the CMI. The Group 2 included workers (N = 56), who were diagnosed with the CMI longer than 14 years ago. The Group 3 consisted of the subjects (N = 18), who had been diagnosed with the CMI 3-5 years ago. The logistic regression analysis was used for 3 genetic models with and without adjustment for age and duration of mercury vapor exposure. We found that genotypes СС-HSPA1A (+190G/C) and GG-HSPA1B (+1267A/G) had a high predictive risk of the CMI development (adjusted odds ratio (ORadj) = 5.58, p = 0.026 and ORadj = 14.7, p = 0.0015, respectively). Twelve individuals with the CMI had a specific combination of СС-HSPA1A (+190G/C) and GG-HSPA1B (+1267A/G) genotypes, which strongly associated with the diagnosis (ORadj = 12.3, p = 0.0285). Moreover, significant association with the CMI was also obtained for the haplotype G-C of 1267A/G and 190G/C polymorphisms (OR = 2.1, p = 0.018). The association of СС-HSPA1A (+190G/C) and GG-HSPA1B (+1267A/G) genotypes and their combination for the CMI individuals suggests the role for HSPA1 genes in mercury-dependent mechanisms of the CMI development and progression. Int J Occup Med Environ Health 2017;30(1):77-85.

A feasibility study of a novel electro-membrane based process to acidify Kraft black liquor and extract lignin

Abstract Lignin extraction from black liquor is of utmost importance for decreasing the load of the recovery boiler and consequently increasing the production capacity of Kraft process. A feasibility study of a novel acidification technique (acidification with electrodialysis using bipolar membrane (EDBM)) was carried out to drop the pH of Kraft black liquor and extract lignin. In order to evaluate the technical feasibility of the proposed method, the acidification of the Kraft black liquor was performed in two different pathways i.e. electrochemical acidification by means of EDBM process and chemical acidification using sulfuric acid. The results have indicated that the implementation of the proposed method resulting in use of less chemicals than the chemical acidification method and simultaneously production of caustic soda. The experiments performed in the course of this study addressed the advantages and challenges of this electro-membrane based process in the Kraft black liquor acidification application.

Electrochemical acidification of Kraft black liquor: Impacts of pulsed electric field application on bipolar membrane colloidal fouling and process intensification

Lately, interest has emerged in biorefineries that use non-food biomass residues. Lignin is a lignocellulosic biomass which can be extracted from a residual stream, called black liquor, in the Kraft pulping process and converted to a variety of value-added products. A recent study was carried out to acidify the black liquor and extract the lignin by means of electrodialysis with bipolar membrane (EDBM) method. Despite the fact that this green pathway enjoyed an in-situ production of caustic soda as a valuable byproduct and significantly reduced the chemical consumption than the chemical acidification approach, the occurrence of severe colloidal fouling on the cation exchange layer of the bipolar membrane impaired its productivity. To resolve this obstacle, this investigation was performed to determine, for the first time, the impact of the non-stationary pulsed electric field on mitigation of bipolar membrane colloidal fouling and improvement of the process performance in terms of current efficiency, energy consumption and membrane integrity.A comparison between the experimental results obtained from four pause lapses (6, 12, 18 and 24s) with a pulse lapse of 6s and a DC current indicated that application of a rigorous selected pulse/pause ratio can limit the growth of the colloidal particle, suppress the fouling on the bipolar membrane and intensify the EDBM process. The pulse/pause ratio of 6(s)/24(s) was found to be the most appropriate ratio which yielded a high current efficiency (≃80%), a low global system resistance and relative energy consumption (2.6Wh/g−NaOH) and a final pH value of 9.7 which would facilitate an efficient lignin extraction process.

Electrochemical acidification of Kraft black liquor by electrodialysis with bipolar membrane: Ion exchange membrane fouling identification and mechanisms

Integrated forest biorefinery offers promising pathways to sustainably diversify the revenue of pulp and paper industry. In this context, lignin can be extracted from a residual stream of Kraft pulping process, called black liquor, and subsequently converted into a wide spectrum of bio-based products. Electrochemical acidification of Kraft black liquor by electrodialysis with bipolar membrane results in lignin extraction and caustic soda production. Even though the implementation of this method requires less chemicals than the chemical acidification process, fouling of the ion exchange membranes and especially bipolar membrane impairs its productivity. Membrane thickness and ash content measurements along with scanning electron microscopy (SEM), elemental analysis (EDX) and X-ray photoelectron spectrometry (XPS) analysis were performed to identify the nature and mechanisms of the membrane fouling. The results revealed that the fouling layer mostly consisted of organic components and particularly lignin. Based on our proposed fouling mechanisms, throughout the electrodialysis process the pH of the black liquor gradually decreased and as a result more proton ions were available to trigger protonation reaction of lignin phenolic groups and decrease the lignin solubility. Due to the abundance of the proton ions on the surface of the cation exchange layers of the bipolar membrane, destabilized lignin macro-molecules started to self-aggregate and formed lignin clusters on its surface. Over the time, these lignin clusters covered the entire surface of the bipolar membrane and the spaces between the membranes and, eventually, attached to the surface of the cation exchange membrane.

ASSOCIATION OF POLYMORPHIC LOCI HSP1A GENES WITH THE DEVELOPMENT OF CHRONIC MERCURY INTOXICATION

The present study investigated the association between polymorphic variants of HSP1A genes (HSP70 gene family) and chronic mercury intoxication (CMI) development in 87 workers of caustic soda production plant, who have been chronically exposed to mercury vapor. The polymorphic loci HSPA1B (+1267A/G и +2074G/C) and HSP1AL (+2437T/C) were studied. Genotyping was performed using PCR-RFLP and logistic regression analysis was used for three genetic models for the investigation of the required associations. We found that frequency of genotype GG HSPA1B (+1267A/G) in group of patients with CMI (n = 45) was higher (p = 0.003) compared with the group of workers without the disease (n = 42). Recessive genetic model found a strong association of the homozygous GG genotype for rare allele with the development of CMI (OR = 13.26, p = 0.001). The obtained associations indicate that the HSPA1 could be important in mechanisms of CMI development and progression and help to develop the criteria for assessing individual's susceptibility to its development.

Investigation of the interaction of sodium hypochlorite with olefins in cavitation fields

The interaction of sodium hypochlorite as a component of wastewater production of caustic soda and chlorine compounds from olefinic C 4 -C 7 number contained in wastewater olefinic production was investigated. The processes of neutralization of sodium hypochlorite, which are implemented in the industry, are very energy-intensive or require large amounts of reagents. That is why it was suggested to intensify the interaction of sodium hypochlorite with olefins by using cavitation fields. Based on the experimental results the main kinetic parameters of the process was calculated: the rate constant, order of reaction temperature coefficient. It is assumed that the process is carried out for a radical mechanism. It was found out that as increasing temperature and power ultrasonic emitter rate constant of the reaction between sodium hypochlorite and olefins increases. In this case the duration of process and unit costs of energy for the decomposition of sodium hypochlorite was reduced. The results will be used to develop energy-efficient process simultaneous neutralization of hypochloritic and olefinic wastewater generated in related industries.

Life cycle assessment of caustic soda production: a case study in China

Abstract Life cycle assessment was conducted to estimate the environmental impact of caustic soda production. Electricity and raw salt production accounted for >90% of the overall environmental burden. These findings can be attributed to electrical consumption for bipolar electrolysis and brine extraction, diesel consumption for generating electricity during well production, and direct heavy metal emissions during drilling fluid loss and waste disposal. The key factors in reducing the overall environmental impact include optimizing raw salt production, electricity, and steam consumption efficiency, choosing drilling fluids with less toxic heavy metals (e.g., arsenic, barium, molybdenum, selenium, vanadium, beryllium, and nickel), minimizing brine leakage during brine transport, reducing the volume of drilling fluid lost, and decreasing the transport distance from brine buyers to suppliers.

Processes for working-up an aqueous fluosilicic acid solution

Aqueous fluosilicic acid solutions were once considered to be only adverse by-products of phosphoric acid production, which required treatment to prevent ecosystem destruction when discharged into the sea. However, a range of chemicals can be generated by the transformation of this industrial waste product. Through experiments undertaken in the laboratory, we have shown the possibility of caustic soda production. Volumetric analysis showed caustic soda to be present as a 6% – 7% solution with yields of about 70% – 80% by weight. Two processes were investigated for the caustification of sodium fluoride, using different precipitates: sodium chloride and ethanol and are described by modelling caustification curves. The activation energies of precipitation determined by semi-empirical correlations showed that precipitation by ethanol (E A = 933.536 J/mol) was more successful than precipitation by sodium chloride(E A = 7452.405 J/mol). Analyses performed on the precipitates highlighted compositions that are essential and useful constituents in the cement industry.

Trends of mercury emissions from the Chlor-Alkali industry in EECCA countries

The article presents an assessment of the trends of mercury emissions from the chIor-alkali industry in EECCA countries during the period 1990–2006. Factors contributing to the decrease in the atmospheric emissions of mercury, as well as uncertainties surrounding its sources and assessment, are analyzed. The assessment of mercury emissions is based on emission factors and on available data on mercury-cell caustic soda production. Previously developed emission factors for mercury-cell caustic soda production have been revised; high and low emission factors have been calculated taking into account technological advances since 1990. The results show that the range of mercury emissions from the chlor-alkali industry amounted to 22.9–91.8 tons in 1990, and 2.4–19.2 tons in 2006. The median value of mercury emissions has been estimated at 57.3 tons in 1990 and 5.9 tons in 2006. Although mercury emissions decreased by a factor of almost 10 during the period studied, the difference between the high and low values increased by a factor of roughly 2. Among the EECCA countries, Russia's share of total mercury emissions is the largest. Furthermore, its contribution to mercury emissions from the chlor-alkali industry is increasing: in the early 1990s it produced 74% of total mercury emissions in EECCA countries, in 2006 it produced 94%.

Global mercury emissions to the atmosphere from anthropogenic and natural sources

Abstract. This paper provides an up-to-date assessment of global mercury emissions from anthropogenic and natural sources. On an annual basis, natural sources account for 5207 Mg of mercury released to the global atmosphere, including the contribution from re-emission processes, which are emissions of previously deposited mercury originating from anthropogenic and natural sources, and primary emissions from natural reservoirs. Anthropogenic sources, which include a large number of industrial point sources, are estimated to account for 2320 Mg of mercury emitted annually. The major contributions are from fossil-fuel fired power plants (810 Mg yr−1), artisanal small scale gold mining (400 Mg yr−1), non-ferrous metals manufacturing (310 Mg yr−1), cement production (236 Mg yr−1), waste disposal (187 Mg yr−1) and caustic soda production (163 Mg yr−1). Therefore, our current estimate of global mercury emissions suggests that the overall contribution from natural sources (primary emissions + re-emissions) and anthropogenic sources is nearly 7527 Mg per year, the uncertainty associated with these estimates are related to the typology of emission sources and source regions.

Production of Caustic Soda, Sulfuric Acid, and Oxygen from Splitting Waste Sodium Sulfate from the ClO2 Generator Using the FM-21 Electrolytic Commercial Cell

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Production of Caustic Soda and Sulphuric Acid by Electrolysis of Waste Sodium Sulphate from Kraft Mill Operations. Part III: Sodium Sulphate Conversion Rate

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Production of Caustic Soda and Sulphuric Acid by Electrolysis of Waste Sodium Sulphate from Kraft Mill Operations. Part II: The Effects of Membrane Type, Initial Feed pH, Cell flow, and Temperature on Energy Performance

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Mercury emissions to the atmosphere from anthropogenic sources in Europe in 2000 and their scenarios until 2020

The paper reviews the current state of knowledge regarding European emissions of mercury and presents estimates of European emissions of mercury to the atmosphere from anthropogenic sources for the year 2000. This information was then used as a basis for Hg emission scenario development until the year 2020. Combustion of coal in power plants and residential heat furnaces generates about half of the European emissions being 239 tonnes. The coal combustion is followed by the production of caustic soda with the use of the Hg cell process (17%). Major points of mercury emission generation in the mercury cell process include: by-product hydrogen stream, end box ventilation air, and cell room ventilation air. This technology is now being changed to other caustic soda production technologies and further reduction of Hg emissions is expected in this connection. The third category on the list of the largest Hg emitters in Europe is cement production (about 13%). The largest emissions were estimated for Russia (the European part of the country), contributing with about 27% to the European emissions, followed by Poland, Germany, Spain, Ukraine, France, Italy and the United Kingdom. Most of these countries use coal as a major source of energy in order to meet the electricity and heat demands. In general, countries in the Central and Eastern Europe generated the main part of the European emissions in 2000. Emission reductions between 20% and 80% of the 2000 emission amounts can be obtained by the year 2020, as estimated by various scenarios.

VERONICA and TINOR 2000: New Technologies for Aluminum Production

The technology for the production of aluminum by the electrolysis of alumina, dissolved in molten cryolite at temperatures around 950°C, is more than one hundred years old. The process, conceived almost simultaneously by Hall and Héroult, which can be expressed 2Al2O3 + 3C → 4Al + 3CO2 has not undergone the same process evolution that other large electrochemical processes have, such as the electrochemical production of chlorine and caustic soda from brine.

Electrochemical Process for the Simultaneous and Chlorine Free Production of High Purity Hydrochloric Acid and Caustic Soda

Electrochemical Process for the Simultaneous and Chlorine Free Production of High Purity Hydrochloric Acid and Caustic Soda