MBOU Secondary school No. 2
Made by a 2nd grade student
Mandrikova Margarita
Africa.
Africa is the second largest continent after Eurasia.
The name Africa, as some scholars believe, comes from the name of a tribe that used to live in the north of the mainland, and was called Afrigs.
In Africa, there is the longest river in the world - the Nile, its length is 6,671 kilometers.
There are more large wild animals on the African continent than on any other. There are such species as: elephants, hippos, giraffes, lions, antelopes, ostriches, etc.
Africa is very famous for its rich deposits of gold and diamonds. Half of the gold and diamonds mined in the world falls on this continent.
In Africa, there is Lake Malawi, which is home to the most species of fish.
In Africa, there is one of the wonders of the world - the pyramid of Cheops, the only one that has survived to this day.
In Africa, Lake Chad, which was the 4th largest, has practically disappeared. Over the past 38 years, it has decreased by 95%.
In Africa, namely in Ancient Egypt, the first toilets and sewer systems arose. The Egyptians were very sensitive to cleanliness.
The area of only one Sahara desert in Africa is slightly smaller than the United States of America. Previously, this place was very fertile, but with the passage of time and changing weather conditions, it turned into a desert.
Africa is the motherland of all languages in the world. This conclusion was reached by scientists after numerous studies.
Among the inhabitants of Africa there are the smallest and tallest peoples in the world.
In Africa, or rather in Benin, a wall was built, the length of which is almost 2 times greater than the Great Chinese wall- 16,000 kilometers.
The African continent is the oldest inhabited region on earth.
The total area of Africa is 16 million square kilometers.
Australia.
Australia is the driest inhabited continent in the world. No more than 50 centimeters of precipitation falls there annually.
Australia occupies the 6th place in the world in terms of area, and the population there is only 20 million people.
Australia was originally called New South Wales.
The longest fence in the world was built in Australia. It was built in order to fence off dingoes from sheep, which are very numerous on the continent.
The Australian continent is home to emus, kangaroos and koalas. From there they were shipped all over the world.
Australia was the third country in the world to launch a satellite into Earth's orbit.
Australia is the first country in the world in terms of sheep and wool production. For a relatively small population of 20 million sheep there are about 150 million.
Australia has 3 time zones.
In one state in Australia, only qualified electricians can replace light bulbs.
In Australia, it is legally enforced that you cannot appear in a public place with your face smeared with shoe polish.
Australia is the lowest continent in the world. The average height above the sea is only 330 meters.
Australia is the continent with the most high level literacy throughout the world.
In Australia, namely in Sydney, there is the world's largest arch bridge. It's called the Sydney Harbor Bridge. And the Sydney television tower is the tallest in the entire southern hemisphere.
It is noteworthy that more snow falls in the mountains of Australia than in all of Switzerland combined.
Colored seas of planet Earth.
Red sea.
The Red Sea belongs to the Indian Ocean basin. Located between Asia and Africa. This sea is warm and crystal clear. The history of the name consists of several versions. It is said that the name comes from the red algae with which it is so rich. Algae give the water a reddish tint. However, most likely the name comes from the color of the water, which reflects the dark red rocks. The Red Sea has a high salinity, since no river flows into it.
Yellow Sea.
The Yellow Sea belongs to the waters of the Pacific Ocean. The sea got its name due to the fact that it changes its color to yellow-brown. This is due to dust storms on the Yellow River. They also make the water cloudy. Therefore, the sea is not suitable for swimming everywhere.
Black Sea.
It is very difficult to say why the sea is pleasant of blue color called black in many languages of the world. There are several versions. They say that the sea is called black because for many centuries battles were fought on it, and many people died. In memory of those times, the sea is called black. Another legend says that before a storm, the sea changes its color to dark gray. Because the sailors called him black.
White Sea.
Refers to the basin of the Northern Arctic Ocean. Its depth is only 340 meters. The sea is unusually cold. Even in summer the temperature does not rise above 16 degrees. However, here you can see northern birds, whales, seals. It is easy to guess why the sea was called white! Most days the sea is covered with white, dazzling ice!
Marble sea.
The Sea of Marmara is located on the border of two parts of the world Europe and Asia in Turkey, washing its shores. It is connected to the Black Sea by the Bosphorus Strait, and to the Aegean Sea by the Dardanelles Strait. The Sea of Marmara is the smallest sea on Earth.
There is an island in this sea, where from ancient times beautiful marble was mined and transported by ship to different cities along the sea, which was called the Marble Sea. The Sea of Marmara was formed as a result of a break in the earth's crust that divided Europe, Asia and Africa. The territory of the Marmara Sea is located in a seismically active region, therefore, there are often earthquakes and, as a result, tsunamis.
The physical properties of chlorine are considered: the density of chlorine, its thermal conductivity, specific heat capacity and dynamic viscosity at various temperatures. The physical properties of Cl 2 are presented in the form of tables for the liquid, solid and gaseous state of this halogen.
Basic physical properties of chlorine
Chlorine is included in group VII of the third period of the periodic system of elements at number 17. It belongs to the halogen subgroup, has relative atomic and molecular weights of 35.453 and 70.906, respectively. At temperatures above -30°C, chlorine is a greenish-yellow gas with a characteristic pungent, irritating odor. It liquefies easily under ordinary pressure (1.013·10 5 Pa) when cooled to -34°C and forms a clear amber liquid that solidifies at -101°C.
Due to its high reactivity, free chlorine does not occur in nature, but exists only in the form of compounds. It is found mainly in the mineral halite (), it is also part of such minerals as: sylvin (KCl), carnallite (KCl MgCl 2 6H 2 O) and sylvinite (KCl NaCl). The content of chlorine in the earth's crust approaches 0.02% of the total number of atoms in the earth's crust, where it is in the form of two isotopes 35 Cl and 37 Cl in a percentage of 75.77% 35 Cl and 24.23% 37 Cl.
| Property | Meaning |
|---|---|
| Melting point, °С | -100,5 |
| Boiling point, °С | -30,04 |
| Critical temperature, °C | 144 |
| Critical pressure, Pa | 77.1 10 5 |
| Critical density, kg / m 3 | 573 |
| Gas density (at 0°С and 1.013 10 5 Pa), kg/m 3 | 3,214 |
| Density of saturated steam (at 0°С and 3.664 10 5 Pa), kg/m 3 | 12,08 |
| Density of liquid chlorine (at 0 ° C and 3.664 10 5 Pa), kg / m 3 | 1468 |
| Density of liquid chlorine (at 15.6 ° C and 6.08 10 5 Pa), kg / m 3 | 1422 |
| Density of solid chlorine (at -102°С), kg/m 3 | 1900 |
| Relative density in air of gas (at 0°C and 1.013 10 5 Pa) | 2,482 |
| Relative air density of saturated steam (at 0°C and 3.664 10 5 Pa) | 9,337 |
| Relative density of liquid chlorine at 0°С (for water at 4°С) | 1,468 |
| Specific volume of gas (at 0°С and 1.013 10 5 Pa), m 3 /kg | 0,3116 |
| Specific volume of saturated steam (at 0°C and 3.664 10 5 Pa), m 3 /kg | 0,0828 |
| Specific volume of liquid chlorine (at 0°C and 3.664 10 5 Pa), m 3 /kg | 0,00068 |
| Chlorine vapor pressure at 0°C, Pa | 3.664 10 5 |
| Dynamic viscosity of gas at 20°C, 10 -3 Pa s | 0,013 |
| Dynamic viscosity of liquid chlorine at 20°C, 10 -3 Pa s | 0,345 |
| Melting heat of solid chlorine (at the melting point), kJ/kg | 90,3 |
| Heat of vaporization (at boiling point), kJ/kg | 288 |
| Heat of sublimation (at melting point), kJ/mol | 29,16 |
| Molar heat capacity C p of gas (at -73…5727°C), J/(mol K) | 31,7…40,6 |
| Molar heat capacity C p of liquid chlorine (at -101…-34°C), J/(mol K) | 67,1…65,7 |
| Gas thermal conductivity coefficient at 0°C, W/(m K) | 0,008 |
| Thermal conductivity coefficient of liquid chlorine at 30°C, W/(m K) | 0,62 |
| Gas enthalpy, kJ/kg | 1,377 |
| Saturated steam enthalpy, kJ/kg | 1,306 |
| Enthalpy of liquid chlorine, kJ/kg | 0,879 |
| Refractive index at 14°C | 1,367 |
| Specific conductivity at -70°C, Sm/m | 10 -18 |
| Electron affinity, kJ/mol | 357 |
| Ionization energy, kJ/mol | 1260 |
Density of chlorine
Under normal conditions, chlorine is a heavy gas with a density approximately 2.5 times greater than . Density of gaseous and liquid chlorine under normal conditions (at 0 ° C) is equal to 3.214 and 1468 kg / m 3, respectively. When liquid or gaseous chlorine is heated, its density decreases due to an increase in volume due to thermal expansion.
Density of chlorine gas
The table shows the density of chlorine in the gaseous state at various temperatures (in the range from -30 to 140°C) and normal atmospheric pressure (1.013·10 5 Pa). The density of chlorine changes with temperature - when heated, it decreases. For example, at 20 ° C, the density of chlorine is 2.985 kg / m 3, and when the temperature of this gas rises to 100 ° C, the density value decreases to a value of 2.328 kg / m 3.
| t, °С | ρ, kg / m 3 | t, °С | ρ, kg / m 3 |
|---|---|---|---|
| -30 | 3,722 | 60 | 2,616 |
| -20 | 3,502 | 70 | 2,538 |
| -10 | 3,347 | 80 | 2,464 |
| 0 | 3,214 | 90 | 2,394 |
| 10 | 3,095 | 100 | 2,328 |
| 20 | 2,985 | 110 | 2,266 |
| 30 | 2,884 | 120 | 2,207 |
| 40 | 2,789 | 130 | 2,15 |
| 50 | 2,7 | 140 | 2,097 |
With increasing pressure, the density of chlorine increases. The tables below show the density of gaseous chlorine in the temperature range from -40 to 140°C and pressure from 26.6·10 5 to 213·10 5 Pa. With increasing pressure, the density of chlorine in the gaseous state increases proportionally. For example, an increase in the pressure of chlorine from 53.2·10 5 to 106.4·10 5 Pa at a temperature of 10°C leads to a twofold increase in the density of this gas.
| ↓ t, °C | P, kPa → | 26,6 | 53,2 | 79,8 | 101,3 |
|---|---|---|---|---|
| -40 | 0,9819 | 1,996 | — | — |
| -30 | 0,9402 | 1,896 | 2,885 | 3,722 |
| -20 | 0,9024 | 1,815 | 2,743 | 3,502 |
| -10 | 0,8678 | 1,743 | 2,629 | 3,347 |
| 0 | 0,8358 | 1,678 | 2,528 | 3,214 |
| 10 | 0,8061 | 1,618 | 2,435 | 3,095 |
| 20 | 0,7783 | 1,563 | 2,35 | 2,985 |
| 30 | 0,7524 | 1,509 | 2,271 | 2,884 |
| 40 | 0,7282 | 1,46 | 2,197 | 2,789 |
| 50 | 0,7055 | 1,415 | 2,127 | 2,7 |
| 60 | 0,6842 | 1,371 | 2,062 | 2,616 |
| 70 | 0,6641 | 1,331 | 2 | 2,538 |
| 80 | 0,6451 | 1,292 | 1,942 | 2,464 |
| 90 | 0,6272 | 1,256 | 1,888 | 2,394 |
| 100 | 0,6103 | 1,222 | 1,836 | 2,328 |
| 110 | 0,5943 | 1,19 | 1,787 | 2,266 |
| 120 | 0,579 | 1,159 | 1,741 | 2,207 |
| 130 | 0,5646 | 1,13 | 1,697 | 2,15 |
| 140 | 0,5508 | 1,102 | 1,655 | 2,097 |
| ↓ t, °C | P, kPa → | 133 | 160 | 186 | 213 |
|---|---|---|---|---|
| -20 | 4,695 | 5,768 | — | — |
| -10 | 4,446 | 5,389 | 6,366 | 7,389 |
| 0 | 4,255 | 5,138 | 6,036 | 6,954 |
| 10 | 4,092 | 4,933 | 5,783 | 6,645 |
| 20 | 3,945 | 4,751 | 5,565 | 6,385 |
| 30 | 3,809 | 4,585 | 5,367 | 6,154 |
| 40 | 3,682 | 4,431 | 5,184 | 5,942 |
| 50 | 3,563 | 4,287 | 5,014 | 5,745 |
| 60 | 3,452 | 4,151 | 4,855 | 5,561 |
| 70 | 3,347 | 4,025 | 4,705 | 5,388 |
| 80 | 3,248 | 3,905 | 4,564 | 5,225 |
| 90 | 3,156 | 3,793 | 4,432 | 5,073 |
| 100 | 3,068 | 3,687 | 4,307 | 4,929 |
| 110 | 2,985 | 3,587 | 4,189 | 4,793 |
| 120 | 2,907 | 3,492 | 4,078 | 4,665 |
| 130 | 2,832 | 3,397 | 3,972 | 4,543 |
| 140 | 2,761 | 3,319 | 3,87 | 4,426 |
Density of liquid chlorine
Liquid chlorine can exist in a relatively narrow temperature range, the boundaries of which lie from minus 100.5 to plus 144°C (that is, from the melting point to the critical temperature). Above a temperature of 144 ° C, chlorine will not go into a liquid state at any pressure. The density of liquid chlorine in this temperature range varies from 1717 to 573 kg/m 3 .
| t, °С | ρ, kg / m 3 | t, °С | ρ, kg / m 3 |
|---|---|---|---|
| -100 | 1717 | 30 | 1377 |
| -90 | 1694 | 40 | 1344 |
| -80 | 1673 | 50 | 1310 |
| -70 | 1646 | 60 | 1275 |
| -60 | 1622 | 70 | 1240 |
| -50 | 1598 | 80 | 1199 |
| -40 | 1574 | 90 | 1156 |
| -30 | 1550 | 100 | 1109 |
| -20 | 1524 | 110 | 1059 |
| -10 | 1496 | 120 | 998 |
| 0 | 1468 | 130 | 920 |
| 10 | 1438 | 140 | 750 |
| 20 | 1408 | 144 | 573 |
Specific heat capacity of chlorine
The specific heat capacity of gaseous chlorine C p in kJ / (kg K) in the temperature range from 0 to 1200 ° C and normal atmospheric pressure can be calculated by the formula:
where T is the absolute temperature of chlorine in degrees Kelvin.
It should be noted that under normal conditions, the specific heat capacity of chlorine is 471 J/(kg K) and increases upon heating. The increase in heat capacity at temperatures above 500°C becomes insignificant, and at high temperatures the specific heat capacity of chlorine practically does not change.
The table shows the results of calculating the specific heat capacity of chlorine using the above formula (the calculation error is about 1%).
| t, °С | C p , J/(kg K) | t, °С | C p , J/(kg K) |
|---|---|---|---|
| 0 | 471 | 250 | 506 |
| 10 | 474 | 300 | 508 |
| 20 | 477 | 350 | 510 |
| 30 | 480 | 400 | 511 |
| 40 | 482 | 450 | 512 |
| 50 | 485 | 500 | 513 |
| 60 | 487 | 550 | 514 |
| 70 | 488 | 600 | 514 |
| 80 | 490 | 650 | 515 |
| 90 | 492 | 700 | 515 |
| 100 | 493 | 750 | 515 |
| 110 | 494 | 800 | 516 |
| 120 | 496 | 850 | 516 |
| 130 | 497 | 900 | 516 |
| 140 | 498 | 950 | 516 |
| 150 | 499 | 1000 | 517 |
| 200 | 503 | 1100 | 517 |
At a temperature close to absolute zero, chlorine is in a solid state and has a low specific heat capacity (19 J/(kg·K)). As the temperature of solid Cl 2 increases, its heat capacity increases and reaches 720 J/(kg K) at minus 143°C.
Liquid chlorine has a specific heat capacity of 918 ... 949 J / (kg K) in the range from 0 to -90 degrees Celsius. According to the table, it can be seen that the specific heat of liquid chlorine is higher than that of gaseous chlorine and decreases with increasing temperature.
Thermal conductivity of chlorine
The table shows the values of the thermal conductivity coefficients of gaseous chlorine at normal atmospheric pressure in the temperature range from -70 to 400°C.
The thermal conductivity coefficient of chlorine under normal conditions is 0.0079 W / (m deg), which is 3 times less than at the same temperature and pressure. Heating chlorine leads to an increase in its thermal conductivity. Thus, at a temperature of 100°C, the value of this physical property of chlorine increases to 0.0114 W/(m deg).
| t, °С | λ, W/(m deg) | t, °С | λ, W/(m deg) |
|---|---|---|---|
| -70 | 0,0054 | 50 | 0,0096 |
| -60 | 0,0058 | 60 | 0,01 |
| -50 | 0,0062 | 70 | 0,0104 |
| -40 | 0,0065 | 80 | 0,0107 |
| -30 | 0,0068 | 90 | 0,0111 |
| -20 | 0,0072 | 100 | 0,0114 |
| -10 | 0,0076 | 150 | 0,0133 |
| 0 | 0,0079 | 200 | 0,0149 |
| 10 | 0,0082 | 250 | 0,0165 |
| 20 | 0,0086 | 300 | 0,018 |
| 30 | 0,009 | 350 | 0,0195 |
| 40 | 0,0093 | 400 | 0,0207 |
Viscosity of chlorine
The coefficient of dynamic viscosity of gaseous chlorine in the temperature range of 20...500°C can be approximately calculated by the formula:
where η T is the coefficient of dynamic viscosity of chlorine at a given temperature T, K;
η T 0 is the coefficient of dynamic viscosity of chlorine at a temperature T 0 =273 K (at n.a.);
C is Sutherland's constant (for chlorine C=351).
Under normal conditions, the dynamic viscosity of chlorine is 0.0123·10 -3 Pa·s. When heated, such a physical property of chlorine as viscosity takes on higher values.
Liquid chlorine has an order of magnitude higher viscosity than gaseous chlorine. For example, at a temperature of 20°C, the dynamic viscosity of liquid chlorine has a value of 0.345·10 -3 Pa·s and decreases with increasing temperature.
Sources:
- Barkov S. A. Halogens and a subgroup of manganese. Elements of group VII of the periodic system of D. I. Mendeleev. Student aid. M .: Education, 1976 - 112 p.
- tables physical quantities. Directory. Ed. acad. I. K. Kikoina. Moscow: Atomizdat, 1976 - 1008 p.
- Yakimenko L. M., Pasmanik M. I. Reference book on the production of chlorine, caustic soda and basic chlorine products. Ed. 2nd, trans. etc. M.: Chemistry, 1976 - 440 p.
Kuzbass State Technical University
BJD subject
Characterization of chlorine as an emergency chemically hazardous substance
Kemerovo-2009
Introduction
1. Characteristics of AHOV (according to the issued task)
2. Ways to prevent an accident, protection from hazardous chemicals
3. Task
4. Calculation of the chemical situation (according to the issued task)
Conclusion
Literature
Introduction
In total, 3,300 economic facilities operate in Russia, which have significant reserves of hazardous chemical substances. More than 35% of them have choir stocks.
Chlorine (lat. Chlorum), Cl - a chemical element of the VII group of the periodic system of Mendeleev, atomic number 17, atomic mass 35.453; belongs to the halogen family.
Chlorine is also used for chlorination some oto ryh ores with the purpose and attraction of titanium, niobium, zirconium and others.
poisoning chlorine are possible in the chemical, pulp and paper, textile, pharmaceutical industries. Chlorine irritates the mucous membranes of the eyes and respiratory tract. Secondary infection usually joins the primary inflammatory changes. Acute poisoning develops almost immediately. When inhaling medium and low concentrations of chlorine, chest tightness and pain, dry cough, rapid breathing, pain in the eyes, lacrimation, increased levels of leukocytes in the blood, body temperature, etc. are noted. Bronchopneumonia, toxic pulmonary edema, depression, convulsions are possible. . In mild cases, recovery occurs in 3-7 days. As long-term consequences, catarrhs of the upper respiratory tract, recurrent bronchitis, pneumosclerosis are observed; possible activation of pulmonary tuberculosis. With prolonged inhalation of small concentrations of chlorine, similar, but slowly developing forms of the disease are observed. Prevention of poisoning, sealing of production facilities, equipment, effective ventilation, if necessary, the use of a gas mask. The maximum permissible concentration of chlorine in the air of production, premises is 1 mg/m 3 . The production of chlorine, bleach and other chlorine-containing compounds refers to industries with harmful working conditions.
Ministry of Education and Science of the RUSSIAN FEDERATION
Federal STATE EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL EDUCATION
IVANOVSK STATE CHEMICAL AND TECHNOLOGICAL UNIVERSITY
Department of TP and MET
Essay
Chlorine: properties, application, production
Head: Efremov A.M.
Ivanovo 2015
Introduction
General information for chlorine
Application of chlorine
Chemical methods for producing chlorine
Electrolysis. The concept and essence of the process
Industrial production of chlorine
Safety precautions in chlorine production and protection environment
Conclusion
Introduction
chlorine chemical element electrolysis
Due to the scale of the use of chlorine in various fields of science, industry, medicine and in everyday life, the demand for it in Lately increased catastrophically. There are many methods for obtaining chlorine by laboratory and industrial methods, but they all have more disadvantages than advantages. The production of chlorine, for example, from hydrochloric acid, which is a by-product and waste of many chemical and other industries, or table salt mined in salt deposits, is a rather energy-intensive process, environmentally harmful and very dangerous to life and health.
At present, the problem of developing a technology for the production of chlorine, which would eliminate all the above disadvantages, and also have a high yield of chlorine, is very urgent.
.General information on chlorine
Chlorine was obtained for the first time in 1774 by K. Scheele by the interaction of hydrochloric acid with pyrolusite MnO2. However, only in 1810, G. Davy established that chlorine is an element and named it chlorine (from the Greek chloros - yellow-green). In 1813, J. L. Gay-Lussac proposed the name "Chlorine" for this element.
Chlorine is an element of Group VII of the Periodic Table of Elements of D. I. Mendeleev. Molecular weight 70.906, atomic weight 35.453, atomic number 17, belongs to the halogen family. Under normal conditions, free chlorine, consisting of diatomic molecules, is a greenish-yellow non-flammable gas with a characteristic pungent and irritating odor. It is poisonous and causes suffocation. Compressed chlorine gas at atmospheric pressure turns into an amber liquid at -34.05 ° C, solidifies at -101.6 ° C and a pressure of 1 atm. Typically chlorine is a mixture of 75.53% 35Cl and 24.47% 37Cl. Under normal conditions, the density of chlorine gas is 3.214 kg/m3, which is about 2.5 times heavier than air.
Chemically, chlorine is very active, it combines directly with almost all metals (with some only in the presence of moisture or when heated) and with non-metals (except carbon, nitrogen, oxygen, inert gases), forming the corresponding chlorides, reacts with many compounds, replaces hydrogen in saturated hydrocarbons and joins unsaturated compounds. This is due to the wide variety of its application. Chlorine displaces bromine and iodine from their compounds with hydrogen and metals. Alkali metals in the presence of traces of moisture interact with chlorine with ignition, most metals react with dry chlorine only when heated. Steel, as well as some metals, is resistant to dry chlorine at low temperatures, so they are used for the manufacture of equipment and storage for dry chlorine. Phosphorus ignites in an atmosphere of chlorine, forming РCl3, and upon further chlorination - РCl5. Sulfur with chlorine, when heated, gives S2Cl2, SCl2 and other SnClm. Arsenic, antimony, bismuth, strontium, tellurium interact vigorously with chlorine. A mixture of chlorine and hydrogen burns with a colorless or yellow-green flame to form hydrogen chloride (this is a chain reaction). Maximum temperature hydrogen-chlorine flame 2200°C. Mixtures of chlorine with hydrogen, containing from 5.8 to 88.5% H2, are explosive and can explode from the action of light, an electric spark, heating, from the presence of certain substances, such as iron oxides.
With oxygen, chlorine forms oxides: Cl2O, ClO2, Cl2O6, Cl2O7, Cl2O8, as well as hypochlorites (salts of hypochlorous acid), chlorites, chlorates and perchlorates. All oxygen compounds of chlorine form explosive mixtures with easily oxidized substances. Chlorine oxides are unstable and can explode spontaneously, hypochlorites decompose slowly during storage, chlorates and perchlorates can explode under the influence of initiators. Chlorine in water is hydrolyzed, forming hypochlorous and hydrochloric acids: Cl2 + H2O? HClO + HCl. The resulting yellowish solution is often referred to as chlorine water. When chlorinating aqueous solutions of alkalis in the cold, hypochlorites and chlorides are formed: 2NaOH + Cl2 \u003d NaClO + NaCl + H2O, and when heated - chlorates. By chlorination of dry calcium hydroxide, bleach is obtained. When ammonia reacts with chlorine, nitrogen trichloride is formed. During chlorination of organic compounds, chlorine either replaces hydrogen or adds via multiple bonds, forming various chlorine-containing organic compounds. Chlorine forms interhalogen compounds with other halogens. Chlorine fluorides ClF, ClF3, ClF3 are very reactive; for example, in a ClF3 atmosphere, glass wool ignites spontaneously. Chlorine compounds with oxygen and fluorine are known - chlorine oxyfluorides: ClO3F, ClO2F3, ClOF, ClOF3 and fluorine perchlorate FClO4.
Chlorine occurs in nature only in the form of compounds. Its average content in the earth's crust is 1.7 10-2% by weight. Water migration plays a major role in the history of chlorine in the earth's crust. In the form of the Cl- ion, it is found in the World Ocean (1.93%), underground brines and salt lakes. The number of own minerals (mainly natural chlorides) is 97, the main one being halite NaCl (Rock salt). There are also large deposits of potassium and magnesium chlorides and mixed chlorides: sylvin KCl, sylvinite (Na,K)Cl, carnalite KCl MgCl2 6H2O, kainite KCl MgSO4 3H2O, bischofite MgCl2 6H2O. In the history of the Earth, the supply of HCl contained in volcanic gases to the upper parts of the earth's crust was of great importance.
Chlorine quality standards
Index name GOST 6718-93High gradeFirst gradeVolume fraction of chlorine, not less than, %99.899.6Mass fraction of water, not more than, %0.010.04Mass fraction of nitrogen trichloride, not more than, %0.0020.004Mass fraction of non-volatile residue, not more,%0 .0150.10
Storage and transportation of chlorine
Chlorine produced by various methods is stored in special "tanks" or pumped into steel cylindrical (volume 10-250 m3) and spherical (volume 600-2000 m3) cylinders under pressure of own vapors of 18 kgf/cm2. The maximum storage volumes are 150 tons. Cylinders with liquid chlorine under pressure have a special color - protective color. In the event of a depressurization of a chlorine cylinder, a sharp release of gas occurs with a concentration several times higher than the lethal one. It should be noted that during long-term use of chlorine cylinders, extremely explosive nitrogen trichloride accumulates in them, and therefore, from time to time, chlorine cylinders must be routinely flushed and cleaned from nitrogen chloride. Chlorine is transported in containers, railway tanks, cylinders, which are its temporary storage.
2.Application of chlorine
Chlorine is consumed primarily by the chemical industry for the production of various organic chlorine derivatives used to obtain plastics, synthetic rubbers, chemical fibers, solvents, insecticides, etc. Currently, over 60% of the world's chlorine production is used for organic synthesis. In addition, chlorine is used to produce hydrochloric acid, bleach, chlorates and other products. Significant amounts of chlorine are used in metallurgy for chlorination in the processing of polymetallic ores, the extraction of gold from ores, and it is also used in the oil refining industry, in agriculture, in medicine and sanitation, for the neutralization of drinking and waste water, in pyrotechnics and a number of other areas of the national economy. As a result of the development of chlorine uses, mainly due to the success of organic synthesis, the world production of chlorine is more than 20 million tons / year.
The main examples of the application and use of chlorine in various branches of science, industry and domestic needs:
1.in the production of polyvinyl chloride, plastic compounds, synthetic rubber, from which they are made: insulation for wires, window profile, packaging materials, clothing and footwear, linoleum and gramophone records, varnishes, equipment and foam plastics, toys, instrument parts, Construction Materials. Polyvinyl chloride is produced by the polymerization of vinyl chloride, which today is most commonly prepared from ethylene in a chlorine-balanced process through an intermediate 1,2-dichloroethane.
CH2=CH2+Cl2=>CH2Cl-CH2ClCl-CH2Cl=> CH2=CHCl+HCl
1)as a bleaching agent (although not chlorine itself “bleaches”, but atomic oxygen, which is formed during the decomposition of hypochlorous acid according to the reaction: Cl2 + H2O ? HCl + HClO ? 2HCl + O*).
2)in the production of organochlorine insecticides - substances that kill insects harmful to crops, but are safe for plants (aldrin, DDT, hexachloran). One of the most important insecticides is hexachlorocyclohexane (C6H6Cl6).
)used as a chemical warfare agent, as well as for the production of other chemical warfare agents: mustard gas (C4H8Cl2S), phosgene (CCl2O).
)for water disinfection - "chlorination". The most common method of drinking water disinfection is based on the ability of free chlorine and its compounds to inhibit the enzyme systems of microorganisms that catalyze redox processes. For the disinfection of drinking water, chlorine (Cl2), chlorine dioxide (ClO2), chloramine (NH2Cl) and bleach (Ca(Cl)OCl) are used.
)V Food Industry registered as food additive E925.
)in the chemical production of caustic soda (NaOH) (used in the production of rayon, in the soap industry), hydrochloric acid (HCl), bleach, chlorine chloride (KClO3), metal chlorides, poisons, drugs, fertilizers.
)in metallurgy for the production of pure metals: titanium, tin, tantalum, niobium.
TiO2 + 2C + 2Cl2 => TiCl4 + 2CO;
TiCl4 + 2Mg => 2MgCl2 + Ti (at Т=850°С)
)as an indicator of solar neutrinos in chlorine-argon detectors (The idea of a "chlorine detector" for detecting solar neutrinos was proposed by the famous Soviet physicist Academician B. Pontecorvo and implemented by the American physicist R. Davis and his colleagues. Having caught the neutrino nucleus of the chlorine isotope with an atomic weight of 37, turns into a nucleus of the argon-37 isotope, with the formation of one electron that can be registered.).
Many developed countries are striving to limit the use of chlorine in everyday life, including because the burning of chlorine-containing garbage produces a significant amount of dioxins (global ecotoxicants with powerful mutagenic
3. Chemical methods for producing chlorine
Previously, the production of chlorine by chemical means according to the methods of Weldon and Deacon was widespread. In these processes, chlorine was produced by the oxidation of hydrogen chloride formed as a by-product in the production of sodium sulfate from sodium chloride by the action of sulfuric acid.
the reaction proceeding when using the Weldon method:
4HCl + MnO2 => MnCl2 + 2H2O + Cl2
the reaction proceeding when using the Deacon method:
HCl + O2 => 2H2O + 2Cl2
In the Deacon process, copper chloride was used as a catalyst, a 50% solution of which (sometimes with the addition of NaCl) was impregnated into a porous ceramic support. The optimum reaction temperature on such a catalyst was usually in the range of 430490°. This catalyst is easily poisoned by arsenic compounds, with which it forms inactive copper arsenate, as well as by sulfur dioxide and trioxide. The presence of even small amounts of sulfuric acid vapor in the gas causes a sharp decrease in the yield of chlorine as a result of successive reactions:
H2SO4 => SO2 + 1/2O2 + H2O+ С12 + 2Н2O => 2НCl + H2SO4
С12 + Н2O => 1/2O2 + 2НCl
Thus, sulfuric acid is a catalyst that promotes the reverse conversion of Cl2 to HCl. Therefore, before oxidation on a copper catalyst, hydrochloric gas must be thoroughly purified from impurities that reduce the yield of chlorine.
Deacon's installation consisted of a gas heater, gas filter and a contact device of a steel cylindrical casing, inside of which there were two concentrically arranged ceramic cylinders with holes; the annular space between them is filled with a catalyst. Hydrogen chloride was oxidized with air, so chlorine was diluted. A mixture containing 25 vol.% HCl and 75 vol.% air (~16% O2) was fed into the contact apparatus, and the gas leaving the apparatus contained about 8% C12, 9% HCl, 8% water vapor and 75% air . Such a gas, after washing out of it with HCl and drying with sulfuric acid, was usually used to obtain bleach.
Restoration of the Deacon process is currently based on the oxidation of hydrogen chloride not with air, but with oxygen, which makes it possible to obtain concentrated chlorine using highly active catalysts. The resulting chloro-oxygen mixture is washed from the residuals of HC1 successively with 36% and 20% hydrochloric acid and dried with sulfuric acid. The chlorine is then liquefied and oxygen is returned to the process. The separation of chlorine from oxygen is also carried out by absorbing chlorine under a pressure of 8 atm with sulfur chloride, which is then regenerated to obtain 100% chlorine:
Сl2 + S2CI2
Low-temperature catalysts are used, for example, copper dichloride activated with salts of rare earth metals, which makes it possible to carry out the process even at 100°C and, therefore, to sharply increase the degree of conversion of HCl to Cl2. On a chromium oxide catalyst, the combustion of HCl in oxygen is carried out at 340480°C. The use of a catalyst from a mixture of V2O5 with alkali metal pyrosulfates and activators on silica gel is described. The mechanism and kinetics of this process have been studied and optimal conditions its implementation, in particular in a fluidized bed.
The oxidation of hydrogen chloride with oxygen is also carried out using a molten mixture of FeCl3 + KCl in two stages, carried out in separate reactors. In the first reactor, ferric chloride is oxidized to form chlorine:
2FeCl3 + 1
In the second reactor, ferric chloride is regenerated from iron oxide with hydrogen chloride:
O3 + 6HCI = 2FeCl3 + 3H20
To reduce the vapor pressure of ferric chloride, potassium chloride is added. This process is also proposed to be carried out in one apparatus, in which the contact mass, consisting of Fe2O3, KC1 and copper, cobalt or nickel chloride deposited on an inert carrier, moves from top to bottom of the apparatus. At the top of the apparatus, it passes a hot zone of chlorination, where Fe2Oz is converted into FeCl3, interacting with HCl, which is in the flow of gas going from bottom to top. Then the contact mass descends into the cooling zone, where elemental chlorine is formed under the action of oxygen, and FeCl3 passes into Fe2O3. The oxidized contact mass returns to the chlorination zone again.
A similar indirect oxidation of HCl to Cl2 is carried out according to the scheme:
2HC1 + MgO = MgCl2 + H2O
It is proposed to simultaneously obtain chlorine and sulfuric acid by passing a gas containing HCl, O2 and a large excess of SO2 through a vanadium catalyst at 400-600°C. Then H2SO4 and HSO3Cl are condensed from the gas and SO3 is absorbed by sulfuric acid; chlorine remains in the gas phase. HSO3Cl is hydrolyzed and the released HC1 is returned to the process.
Even more efficient oxidation is carried out by such oxidizing agents as PbO2, KMnO4, KClO3, K2Cr2O7:
2KMnO4 + 16HCl => 2KCl + 2MnCl2 + 5Cl2^ +8H2O
Chlorine can also be obtained by the oxidation of chlorides. For example, when NaCl and SO3 interact, reactions occur:
NaCl + 2SO3 = 2NaSO3Cl
NaSO3Cl = Cl2 + SO2 + Na2SO4
The decomposition of NaSO3Cl occurs at 275°C. A mixture of SO2 and C12 gases can be separated by absorbing chlorine SO2Cl2 or CCl4 or subjecting it to rectification, which results in an azeotropic mixture containing 88 mol. % Cl2 and 12 mol. %SO2. The azeotropic mixture can be further separated by converting SO2 to SO2C12 and separating excess chlorine, and decomposing SO2Cl2 at 200° into SO2 and Cl2, which are added to the mixture sent for rectification.
Chlorine can be obtained by oxidizing chloride or hydrogen chloride with nitric acid, as well as nitrogen dioxide:
ZHCl + HNO3 => Сl2 + NOCl + 2Н2O
Another way to obtain chlorine is the decomposition of nitrosyl chloride, which can be achieved by its oxidation:
NOCl + O2 = 2NO2 + Сl2
Also, to obtain chlorine, it is proposed, for example, to oxidize NOCl with 75% nitric acid:
2NOCl + 4HNO3 = Сl2 + 6NO2 + 2Н2O
A mixture of chlorine and nitrogen dioxide is separated by converting NO2 into weak nitric acid, which is then used to oxidize HCl in the first stage of the process to form Cl2 and NOCl. The main difficulty in the implementation of this process on an industrial scale is the elimination of corrosion. Ceramics, glass, lead, nickel, and plastics are used as materials for equipment. According to this method in the USA in 1952-1953. the plant was operating with a capacity of 75 tons of chlorine per day.
A cyclic method has been developed for the production of chlorine by the oxidation of hydrogen chloride with nitric acid without the formation of nitrosyl chloride according to the reaction:
2НCl + 2HNO3 = Сl2 + 2NO2 + 2Н2O
The process goes to liquid phase at 80°C, chlorine yield reaches 100%, NO2 is obtained in liquid form.
Subsequently, these methods were completely replaced by electrochemical ones, but at present chemical methods chlorine production is being revived on a new technical base. All of them are based on the direct or indirect oxidation of HCl (or chlorides), with the most common oxidizing agent being atmospheric oxygen.
Electrolysis. The concept and essence of the process
Electrolysis - a set of electrochemical redox processes that occur on the electrodes during the passage of a constant electric current through a melt or solution with electrodes immersed in it.
Rice. 4.1. Processes occurring during electrolysis. Scheme of the electrolysis bath: 1 - bath, 2 - electrolyte, 3 - anode, 4 - cathode, 5 - power supply
Electrodes can be any materials that conduct electricity. Metals and alloys are mainly used, from non-metals, for example, graphite rods (or carbon) can serve as electrodes. Less commonly, liquids are used as an electrode. A positively charged electrode is an anode. The negatively charged electrode is the cathode. During electrolysis, the anode is oxidized (it dissolves) and the cathode is reduced. That is why the anode should be taken in such a way that its dissolution does not affect the chemical process occurring in the solution or melt. Such an anode is called an inert electrode. As an inert anode, you can take graphite (carbon) or platinum. As a cathode, you can take a metal plate (it will not dissolve). Suitable copper, brass, carbon (or graphite), zinc, iron, aluminum, stainless steel.
Examples of electrolysis of melts:
Examples of electrolysis of salt solutions:
(Cl? anions are oxidized at the anode, and not oxygen O? II of water molecules, since the electronegativity of chlorine is less than that of oxygen, and therefore, chlorine gives off electrons more easily than oxygen)
The electrolysis of water is always carried out in the presence of an inert electrolyte (to increase the electrical conductivity of a very weak electrolyte - water):
Depending on the inert electrolyte, electrolysis is carried out in a neutral, acidic or alkaline environment. When choosing an inert electrolyte, it is necessary to take into account that metal cations that are typical reducing agents (for example, Li +, Cs +, K +, Ca2 +, Na +, Mg2 +, Al3 +) are never reduced at the cathode in an aqueous solution and oxygen O? II of oxo acid anions is never oxidized at the anode with an element in the highest oxidation state (for example, ClO4?, SO42?, NO3?, PO43?, CO32?, SiO44?, MnO4?), water is oxidized instead.
Electrolysis includes two processes: migration of reacting particles under the action of electric field to the electrode surface and charge transfer from particle to electrode or from electrode to particle. The migration of ions is determined by their mobility and transfer numbers. The process of transfer of several electric charges is carried out, as a rule, in the form of a sequence of one-electron reactions, that is, in stages, with the formation of intermediate particles (ions or radicals), which sometimes exist for some time on the electrode in an adsorbed state.
The rates of electrode reactions depend on:
electrolyte composition
electrolyte concentration
electrode material
electrode potential
temperature
hydrodynamic conditions.
The measure of the reaction rate is the current density. This is a vector physical, the modulus of which is determined by the ratio of the current strength (the number of transferred electric charges per unit time) in the conductor to the cross-sectional area.
Faraday's laws of electrolysis are quantitative relationships based on electrochemical studies and help determine the mass of products formed during electrolysis. In the most general form, the laws are formulated as follows:
)Faraday's first law of electrolysis: The mass of a substance deposited on an electrode during electrolysis is directly proportional to the amount of electricity transferred to that electrode. The amount of electricity refers to the electric charge, usually measured in coulombs.
2)Faraday's Second Law of Electrolysis: For a given amount of electricity (electric charge), the mass of a chemical element deposited on an electrode is directly proportional to the equivalent mass of the element. The equivalent mass of a substance is its molar mass divided by an integer, depending on the chemical reaction in which the substance participates.
In mathematical form, Faraday's laws can be represented as follows:
where m is the mass of the substance deposited on the electrode in grams, is the total electric charge that has passed through the substance, = 96 485.33 (83) C mol? 1 is the Faraday constant, is the molar mass of the substance (For example, the molar mass of water H2O = 18 g / mol), - the valence number of ions of a substance (the number of electrons per ion).
Note that M/z is the equivalent mass of the deposited matter.
For Faraday's first law, M, F, and z are constants, so the larger the Q value, the larger the m value.
For Faraday's second law, Q, F, and z are constants, so the larger the value of M/z (equivalent mass), the greater the value of m.
In the simplest case, DC electrolysis results in:
In a more complex case of alternating electric current, the total charge Q of the current I( ?) is summed over time ? :
where t is the total electrolysis time.
In industry, the electrolysis process is carried out in special devices - electrolyzers.
Industrial production of chlorine
Currently, chlorine is mainly produced by electrolysis of aqueous solutions, namely one of
The raw materials for the electrolytic production of chlorine are mainly NaCl solutions obtained by dissolving solid salt, or natural brines. There are three types of salt deposits: fossil salt (about 99% of the reserves); salt lakes with bottom sediments of self-saddle salt (0.77%); the rest is underground splits. Salt solutions, regardless of the way they are obtained, contain impurities that worsen the electrolysis process. Calcium cations Ca2+, Mg2+ and SO42- anions have a particularly unfavorable effect during electrolysis with a solid cathode, and impurities of compounds containing heavy metals, such as chromium, vanadium, germanium and molybdenum, have an effect during electrolysis with a liquid cathode.
Crystalline salt for chlorine electrolysis should have the following composition (%): sodium chloride not less than 97.5; Mg2+ not more than 0.05; insoluble sediment not more than 0.5; Ca2+ not more than 0.4; K+ not more than 0.02; SO42 - no more than 0.84; humidity not more than 5; impurity of heavy metals (determined by amalgam sample cm3 H2) not more than 0.3. Cleaning of brines is carried out with a solution of soda (Na2CO3) and milk of lime (suspension of a suspension of Ca (OH) 2 in water). In addition to chemical purification, solutions are freed from mechanical impurities by sedimentation and filtration.
The electrolysis of common salt solutions is carried out in baths with a solid iron (or steel) cathode and with diaphragms and membranes, in baths with a liquid mercury cathode. Industrial electrolyzers used for the equipment of modern large chlorine plants must have high productivity, simple design, be compact, work reliably and stably.
Electrolysis proceeds according to the scheme:
MeCl + H2O => MeOH + Cl2 + H2,
where Me is an alkali metal.
During the electrochemical decomposition of table salt in electrolyzers with solid electrodes, the following main, reversible and irreversible ionic reactions occur:
dissociation of salt and water molecules (goes in the electrolyte)
NaCl-Na++Cl-
Chlorine ion oxidation (at the anode)
C1- - 2e- => C12
reduction of hydrogen ion and water molecules (at the cathode)
H+ - 2e- => H2
H2O - 2e - \u003d\u003e H2 + 2OH-
Association of ions into a sodium hydroxide molecule (in electrolyte)
Na+ + OH- - NaOH
Useful products are sodium hydroxide, chlorine and hydrogen. All of them are removed from the electrolyzer separately.
Rice. 5.1. Scheme of a diaphragm electrolyzer
The cavity of the cell with a solid cathode (Fig. 3) is divided by a porous
The first industrial electrolyzers operated in batch mode. The electrolysis products in them were separated by a cement diaphragm. Subsequently, electrolyzers were created, in which bell-shaped partitions served to separate the electrolysis products. At the next stage, electrolyzers with a flow diaphragm appeared. In them, the principle of counterflow was combined with the use of a separating diaphragm, which was made from asbestos cardboard. Further, a method was discovered for obtaining a diaphragm from asbestos pulp, borrowed from the technology of the paper industry. This method made it possible to develop designs of electrolyzers for a large current load with a non-separable compact finger cathode. To increase the service life of an asbestos diaphragm, it is proposed to introduce some synthetic materials into its composition as a coating or bond. It is also proposed to manufacture diaphragms entirely from new synthetic materials. There is evidence that such combined asbestos-synthetic or specially manufactured synthetic diaphragms have a service life of up to 500 days. Special ion-exchange diaphragms are also being developed, which make it possible to obtain pure caustic soda with a very low content of sodium chloride. The action of such diaphragms is based on the use of their selective properties for the passage of various ions.
The places of contacts of current leads to graphite anodes in early designs were taken out of the cell cavity. Later, methods were developed to protect the contact parts of the anodes immersed in the electrolyte. Using these techniques, industrial electrolyzers with a lower current supply were created, in which the anode contacts are located in the cavity of the electrolyzer. They are used everywhere at the present time for the production of chlorine and caustic on a solid cathode.
A stream of saturated sodium chloride solution (purified brine) continuously enters the anode space of the diaphragm cell. As a result of the electrochemical process, chlorine is released at the anode due to the decomposition of common salt, and hydrogen is released at the cathode due to the decomposition of water. Chlorine and hydrogen are removed from the electrolyzer, without mixing, separately. In this case, the near-cathode zone is enriched with sodium hydroxide. The solution from the cathode zone, called electrolytic liquor, containing undecomposed table salt (approximately half of the amount supplied with brine) and sodium hydroxide, is continuously removed from the electrolyzer. At the next stage, the electrolytic liquor is evaporated and the content of NaOH in it is adjusted to 42-50% in accordance with the standard. Table salt and sodium sulfate precipitate with increasing concentration of sodium hydroxide.
The NaOH solution is decanted from the crystals and transferred as a finished product to a warehouse or caustic smelting stage to obtain a solid product. Crystalline table salt (reverse salt) is returned to electrolysis, preparing from it the so-called reverse brine. From it, in order to avoid the accumulation of sulfate in solutions, sulfate is extracted before preparing the return brine. The loss of table salt is compensated by the addition of fresh brine obtained by underground leaching of salt layers or by dissolving solid table salt. Before mixing it with the reverse brine, fresh brine is cleaned of mechanical suspensions and a significant part of calcium and magnesium ions. The resulting chlorine is separated from water vapor, compressed and transferred either directly to consumers or to liquefy chlorine. Hydrogen is separated from water, compressed and transferred to consumers.
The same chemical reactions take place in a membrane electrolyzer as in a diaphragm electrolyzer. Instead of a porous diaphragm, a cationic membrane is used (Fig. 5).
Rice. 5.2. Scheme of a membrane electrolyzer
The membrane prevents the penetration of chlorine ions into the catholyte (electrolyte in the cathode space), due to which caustic soda can be obtained directly in the electrolyzer almost without salt, with a concentration of 30 to 35%. Because there is no need to separate the salt, evaporation makes it much easier to produce 50% commercial caustic soda at a lower investment and energy cost. Since the concentration of caustic soda in the membrane process is much higher, expensive nickel is used as a cathode.
Rice. 5.3. Scheme of a mercury electrolyzer
The total decomposition reaction of common salt in mercury electrolyzers is the same as in diaphragm cells:
NaCl + H2O => NaOH + 1/2Cl2 + 1/2H2
However, here it takes place in two stages, each in a separate apparatus: an electrolyzer and a decomposer. They are structurally interconnected and are called an electrolytic bath, and sometimes a mercury electrolyzer.
At the first stage of the process - in the electrolyzer - the electrolytic decomposition of table salt takes place (its saturated solution is fed into the electrolyzer) with the production of chlorine at the anode, and sodium amalgam at the mercury cathode, according to the following reaction:
NaCl + nHg => l/2Cl2 + NaHgn
In the decomposer, the second stage of the process takes place, in which, under the action of water, sodium amalgam passes into sodium hydroxide and mercury:
NaHgn + H2O => NaOH + 1/2H2 + nHg
Of all the salt supplied to the electrolyzer with brine, only 15-20% of the supplied amount enters into reaction (2), and the rest of the salt, together with water, leaves the electrolyzer in the form of a chloranolyte - a solution of table salt in water containing 250-270 kg / m3 NaCl saturated with chlorine. The “strong amalgam” leaving the electrolyzer and water are supplied to the decomposer.
The electrolyser in all available designs is made in the form of a long and relatively narrow, slightly inclined steel trough, along the bottom of which a thin layer of amalgam, which is the cathode, flows by gravity, and anolyte on top. Brine and weak amalgam are fed from the upper raised edge of the cell through the "inlet pocket".
The strong amalgam flows out from the lower end of the cell through the "outlet pocket". Chlorine and chloranolyte jointly exit through a branch pipe, also located at the lower end of the cell. Anodes are suspended above the entire amalgam flow mirror or cathode at a distance of 3–5 mm from the cathode. The top of the cell is covered with a lid.
Two types of decomposers are common: horizontal and vertical. The former are made in the form of a steel inclined chute of the same length as the electrolytic cell. An amalgam stream flows along the bottom of the decomposer, which is installed at a slight inclination. A decomposer made of graphite is immersed in this flow. Water moves in the opposite direction. As a result of the decomposition of the amalgam, the water is saturated with caustic. The caustic solution, together with hydrogen, exits the decomposer through a branch pipe in the bottom, and the poor amalgam or mercury is pumped into the cell pocket.
In addition to the electrolyzer, decomposer, pockets and overflow pipelines, the set of the electrolysis bath includes a mercury pump. Two types of pumps are used. In cases where the baths are equipped with a vertical decomposer or where the decomposer is installed below the electrolytic cell, submersible centrifugal pumps conventional type, lowered into the decomposer. In baths where the decomposer is installed next to the electrolyser, the amalgam is pumped over by a cone rotary pump of the original type.
All steel parts of the electrolyzer that come into contact with chlorine or chloranolyte are protected by a coating of special grade vulcanized rubber (gumming). The protective layer of rubber is not absolutely resistant. Over time, it chlorinates, becomes brittle and cracks from the action of temperature. Periodically, the protective layer is renewed. All other parts of the electrolysis bath: decomposer, pump, overflows - are made of unprotected steel, since neither hydrogen nor a caustic solution corrode it.
Currently, graphite anodes are the most common in a mercury cell. However, they are being replaced by ORTA.
6.Safety in chlorine production
and environmental protection
The danger to personnel in the production of chlorine is determined by the high toxicity of chlorine and mercury, the possibility of the formation of explosive gas mixtures of chlorine and hydrogen, hydrogen and air in the equipment, as well as solutions of nitrogen trichloride in liquid chlorine, the use in the production of electrolyzers - devices that are under an increased electrical potential relative to earth, the properties of caustic alkali produced in this production.
Inhalation of air containing 0.1 mg/l of chlorine for 30-60 minutes is life threatening. Inhalation of air containing more than 0.001 mg/l of chlorine irritates the respiratory tract. Maximum allowable concentration (MAC) of chlorine in the air of settlements: average daily 0.03 mg/m3, maximum single 0.1 mg/m3, in air working area industrial premises is 1 mg/m3, the odor perception threshold is 2 mg/m3. At a concentration of 3-6 mg/m3, a distinct smell is felt, irritation (redness) of the eyes and mucous membranes of the nose occurs, at 15 mg/m3 - irritation of the nasopharynx, at 90 mg/m3 - intense coughing attacks. Exposure to 120 - 180 mg/m3 for 30-60 minutes is life-threatening, at 300 mg/m3 a lethal outcome is possible, a concentration of 2500 mg/m3 leads to death within 5 minutes, at a concentration of 3000 mg/m3 a lethal outcome occurs after several breaths . The maximum allowable concentration of chlorine for filtering industrial and civil gas masks is 2500 mg/m3.
The presence of chlorine in the air is determined by chemical reconnaissance devices: VPKhR, PPKhR, PKhR-MV using indicator tubes IT-44 (pink color, sensitivity threshold 5 mg / m3), IT-45 (orange color), aspirators AM-5, AM- 0055, AM-0059, NP-3M with indicator tubes for chlorine, universal gas analyzer UG-2 with a measurement range of 0-80 mg/m3, gas detector "Kolion-701" in the range of 0-20 mg/m3. In open space - with SIP "KORSAR-X" devices. Indoors - with SIP "VEGA-M" devices. For protection against chlorine in the event of a malfunction or emergency situations all people in the workshops must have and use gas masks of grades “V” or “BKF” in a timely manner (except for mercury electrolysis workshops), as well as protective clothing: cloth or rubberized suits, rubber boots and mittens. Gas mask boxes against chlorine must be painted yellow.
Mercury is more poisonous than chlorine. The maximum permissible concentration of its vapors in the air is 0.00001 mg/l. It affects the human body when inhaled and when it comes into contact with the skin, as well as in contact with amalgamated objects. Its vapors and splashes are adsorbed (absorbed) by clothes, skin, teeth. At the same time, mercury easily evaporates at a temperature; available in the electrolysis shop, and the concentration of its vapors in the air is much higher than the maximum allowable. Therefore, electrolysis shops with a liquid cathode are equipped with powerful ventilation, which during normal operation ensures an acceptable level of mercury vapor concentration in the shop atmosphere. However, this is not enough for safe operation. It is also necessary to observe the so-called mercury discipline: follow the rules for handling mercury. Following them, before starting work, the personnel passes through the sanitary inspection room, in the clean section of which they leave their home clothes and put on freshly washed linen, which is workwear. At the end of the shift, overalls and dirty linen are left in the dirty section of the sanitary checkpoint, while the workers take a shower, brush their teeth and put on household items in the clean section of the sanitary checkpoint.
In workshops that work with chlorine and mercury, you should use a gas mask of brand "G" (the gas mask box is painted black and yellow colors) and rubber gloves., The rules of "mercury discipline" stipulate that work with mercury and amalgamated surfaces should be carried out only under a layer of water; spilled mercury should immediately be flushed down the drain, where there are mercury traps.
Emissions of chlorine and mercury vapor into the atmosphere, discharges of mercury salts and mercury droplets, compounds containing active chlorine into wastewater, and soil poisoning by mercury sludge pose a danger to the environment. Chlorine enters the atmosphere during accidents, with ventilation emissions and exhaust gases from various devices. Mercury vapor is carried out with air from ventilation systems. The norm of chlorine content in the air when released into the atmosphere is 0.03 mg/m3. This concentration can be achieved if an alkaline multi-stage off-gas washing is used. The norm of mercury content in the air when emitted into the atmosphere is 0.0003 mg/m3, and in wastewater when discharged into water bodies is 4 mg/m3.
Neutralize chlorine with the following solutions:
milk of lime, for which 1 weight part of slaked lime is poured into 3 parts of water, mixed thoroughly, then drained from above mortar(for example, 10 kg of slaked lime + 30 liters of water);
5% aqueous solution soda ash, for which 2 weight parts of soda ash are dissolved with stirring with 18 parts of water (for example, 5 kg of soda ash + 95 liters of water);
5% aqueous solution of caustic soda, for which 2 parts by weight of caustic soda are dissolved with stirring with 18 parts of water (for example, 5 kg of caustic soda + 95 liters of water).
When chlorine gas leaks, water is sprayed to extinguish the vapors. The rate of water consumption is not standardized.
When liquid chlorine is spilled, the spill site is fenced with an earthen rampart, filled with milk of lime, a solution of soda ash, caustic soda, or water. To neutralize 1 ton of liquid chlorine, 0.6-0.9 tons of water or 0.5-0.8 tons of solutions are needed. To neutralize 1 ton of liquid chlorine, 22-25 tons of solutions or 333-500 tons of water are needed.
To spray water or solutions, watering and fire trucks, auto-bottling stations (AC, PM-130, ARS-14, ARS-15), as well as hydrants and special systems available at chemically hazardous facilities are used.
Conclusion
Since the volumes of chlorine produced by laboratory methods are negligible in comparison with the ever-increasing demand for this product, it is necessary to carry out comparative analysis doesn't make sense.
Of the electrochemical production methods, liquid (mercury) cathode electrolysis is the easiest and most convenient, but this method is not without drawbacks. It causes significant environmental damage through evaporation and leakage of metallic mercury and chlorine gas.
Electrolyzers with a solid cathode eliminate the risk of environmental pollution by mercury. When choosing between diaphragm and membrane electrolyzers for new production facilities, the latter are preferred as they are more economical and provide a higher quality end product.
Bibliography
1.Zaretsky S. A., Suchkov V. N., Zhivotinsky P. B. Electrochemical technology of inorganic substances and chemical current sources: A textbook for students of technical schools. M ..: Higher. School, 1980. 423 p.
2.Mazanko A. F., Kamaryan G. M., Romashin O. P. Industrial membrane electrolysis. M.: publishing house "Chemistry", 1989. 240 p.
.Pozin M.E. Technology of mineral salts (fertilizers, pesticides, industrial salts, oxides and acids), part 1, ed. 4th, rev. L., Publishing House "Chemistry", 1974. 792 p.
.Fioshin M. Ya., Pavlov VN Electrolysis in inorganic chemistry. M.: publishing house "Nauka", 1976. 106 p.
.Yakimenko L. M. Production of chlorine, caustic soda and inorganic chlorine products. M.: publishing house "Chemistry", 1974. 600 p.
Internet sources
6.Safety rules for the production, storage, transportation and use of chlorine // URL: #"justify">7. Hazardous Substances // URL: #"justify">. Chlorine: application // URL: #"justify">.
