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Units production chemical current sources

Branch of knowledge: 16 Chemical and bioengineering. Stender biennium. Presently the department is headed by Doctor of Technical Sciences, prof. Vladimir H. Over the period of the existence of the Department more than specialists who work in chemical, machine-building and metallurgical enterprises have been trained.

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Lithium: Sources, Production, Uses, and Recovery Outlook

VIDEO ON THE TOPIC: Electrochemistry: Crash Course Chemistry #36

When you forget to turn off your car lights, they slowly dim as the battery runs down. Their gradual dimming implies that battery output voltage decreases as the battery is depleted. Furthermore, if you connect an excessive number of V lights in parallel to a car battery, they will be dim even when the battery is fresh and even if the wires to the lights have very low resistance.

The reason for the decrease in output voltage for depleted or overloaded batteries is that all voltage sources have two fundamental parts—a source of electrical energy and an internal resistance. Let us examine both. You can think of many different types of voltage sources. Batteries themselves come in many varieties. Solar cells create voltages directly from light, while thermoelectric devices create voltage from temperature differences.

A few voltage sources are shown in [link]. All such devices create a potential difference and can supply current if connected to a resistance. On the small scale, the potential difference creates an electric field that exerts force on charges, causing current. We thus use the name electromotive force , abbreviated emf.

Emf is not a force at all; it is a special type of potential difference. To be precise, the electromotive force emf is the potential difference of a source when no current is flowing. Units of emf are volts. Electromotive force is directly related to the source of potential difference, such as the particular combination of chemicals in a battery. However, emf differs from the voltage output of the device when current flows. The voltage across the terminals of a battery, for example, is less than the emf when the battery supplies current, and it declines further as the battery is depleted or loaded down.

As noted before, a V truck battery is physically larger, contains more charge and energy, and can deliver a larger current than a V motorcycle battery. Both are lead-acid batteries with identical emf, but, because of its size, the truck battery has a smaller internal resistance.

Internal resistance is the inherent resistance to the flow of current within the source itself. The emf represented by a script E in the figure and internal resistance are in series. The smaller the internal resistance for a given emf, the more current and the more power the source can supply. The internal resistance can behave in complex ways. As noted, increases as a battery is depleted. But internal resistance may also depend on the magnitude and direction of the current through a voltage source, its temperature, and even its history.

The internal resistance of rechargeable nickel-cadmium cells, for example, depends on how many times and how deeply they have been depleted. Various types of batteries are available, with emfs determined by the combination of chemicals involved.

We can view this as a molecular reaction what much of chemistry is about that separates charge. The lead-acid battery used in cars and other vehicles is one of the most common types. A single cell one of six of this battery is seen in [link].

The cathode positive terminal of the cell is connected to a lead oxide plate, while the anode negative terminal is connected to a lead plate. Both plates are immersed in sulfuric acid, the electrolyte for the system.

The details of the chemical reaction are left to the reader to pursue in a chemistry text, but their results at the molecular level help explain the potential created by the battery.

Two electrons are placed on the anode, making it negative, provided that the cathode supplied two electrons. This leaves the cathode positively charged, because it has lost two electrons. In short, a separation of charge has been driven by a chemical reaction. Note that the reaction will not take place unless there is a complete circuit to allow two electrons to be supplied to the cathode.

Under many circumstances, these electrons come from the anode, flow through a resistance, and return to the cathode. Note also that since the chemical reactions involve substances with resistance, it is not possible to create the emf without an internal resistance.

Why are the chemicals able to produce a unique potential difference? Quantum mechanical descriptions of molecules, which take into account the types of atoms and numbers of electrons in them, are able to predict the energy states they can have and the energies of reactions between them. In the case of a lead-acid battery, an energy of 2 eV is given to each electron sent to the anode.

Voltage is defined as the electrical potential energy divided by charge:. An electron volt is the energy given to a single electron by a voltage of 1 V.

So the voltage here is 2 V, since 2 eV is given to each electron. It is the energy produced in each molecular reaction that produces the voltage. A different reaction produces a different energy and, hence, a different voltage. The voltage output of a device is measured across its terminals and, thus, is called its terminal voltage.

Terminal voltage is given by. You can see that the larger the current, the smaller the terminal voltage. And it is likewise true that the larger the internal resistance, the smaller the terminal voltage. Suppose a load resistance is connected to a voltage source, as in [link]. Since the resistances are in series, the total resistance in the circuit is.

We see from this expression that the smaller the internal resistance , the greater the current the voltage source supplies to its load. As batteries are depleted, increases. If becomes a significant fraction of the load resistance, then the current is significantly reduced, as the following example illustrates. A certain battery has a The analysis above gave an expression for current when internal resistance is taken into account. Once the current is found, the terminal voltage can be calculated using the equation.

Once current is found, the power dissipated by a resistor can also be found. Entering the given values for the emf, load resistance, and internal resistance into the expression above yields.

Enter the known values into the equation to get the terminal voltage:. The terminal voltage here is only slightly lower than the emf, implying that is a light load for this particular battery.

Similarly, with , the current is. This terminal voltage exhibits a more significant reduction compared with emf, implying is a heavy load for this battery. The power dissipated by the load can be found using the formula. Entering the known values gives. Note that this power can also be obtained using the expressions or , where is the terminal voltage Here the internal resistance has increased, perhaps due to the depletion of the battery, to the point where it is as great as the load resistance.

As before, we first find the current by entering the known values into the expression, yielding. We see that the increased internal resistance has significantly decreased terminal voltage, current, and power delivered to a load. Battery testers, such as those in [link] , use small load resistors to intentionally draw current to determine whether the terminal voltage drops below an acceptable level.

They really test the internal resistance of the battery. If internal resistance is high, the battery is weak, as evidenced by its low terminal voltage. Some batteries can be recharged by passing a current through them in the direction opposite to the current they supply to a resistance.

This is done routinely in cars and batteries for small electrical appliances and electronic devices, and is represented pictorially in [link]. The voltage output of the battery charger must be greater than the emf of the battery to reverse current through it. This will cause the terminal voltage of the battery to be greater than the emf, since , and is now negative. Multiple Voltage Sources There are two voltage sources when a battery charger is used.

Voltage sources connected in series are relatively simple. When voltage sources are in series, their internal resistances add and their emfs add algebraically. See [link]. Series connections of voltage sources are common—for example, in flashlights, toys, and other appliances. Usually, the cells are in series in order to produce a larger total emf. But if the cells oppose one another, such as when one is put into an appliance backward, the total emf is less, since it is the algebraic sum of the individual emfs.

A battery is a multiple connection of voltaic cells, as shown in [link]. The disadvantage of series connections of cells is that their internal resistances add.

One of the authors once owned a MGA that had two 6-V batteries in series, rather than a single V battery. This arrangement produced a large internal resistance that caused him many problems in starting the engine. Batteries are multiple connections of individual cells, as shown in this modern rendition of an old print.

Single cells, such as AA or C cells, are commonly called batteries, although this is technically incorrect. If the series connection of two voltage sources is made into a complete circuit with the emfs in opposition, then a current of magnitude flows. See [link] , for example, which shows a circuit exactly analogous to the battery charger discussed above. If two voltage sources in series with emfs in the same sense are connected to a load , as in [link] , then. This schematic represents a flashlight with two cells voltage sources and a single bulb load resistance in series.

The current that flows is. Note that each emf is represented by script E in the figure. Take-Home Experiment: Flashlight Batteries Find a flashlight that uses several batteries and find new and old batteries.

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In view of the importance of these publications, it is reasonable to view the IT calorie as being the preferred unit for discussions of energy production and use, but there is no universally adopted practice see also the discussion of Btu, below. Sometimes a capitalized version, Calorie, is used to denoted the kilocalorie kcal. In discussing food, the "calorie," capitalized or not, is always the kilocalorie. As for the calorie, there is a family of "Btu's" in relatively common use, including:. The relationship between the kWh and the Btu depends upon which "Btu" is used. It is common, although not universal, to use the equivalence:.

Electromotive Force: Terminal Voltage

Batteries are everywhere. The modern world is dependent on these portable sources of energy, which are found in everything from mobile devices to hearing aids to cars. But despite their prevalence in people's daily lives, batteries often go overlooked. Think about it: Do you really know how a battery works? Could you explain it to someone else?

Low-Carbon Heat Solutions for Heavy Industry: Sources, Options, and Costs Today

The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy , it converts raw materials oil , natural gas , air , water , metals , and minerals into more than 70, different products. The plastics industry contains some overlap, as most chemical companies produce plastic as well as other chemicals. Various professionals are deeply involved in the chemical industry including chemical engineers, scientists, lab chemists, technicians, etc. Although chemicals were made and used throughout history, the birth of the heavy chemical industry production of chemicals in large quantities for a variety of uses coincided with the beginnings of the Industrial Revolution in general. One of the first chemicals to be produced in large amounts through industrial processes was sulfuric acid. In , the pharmacist Joshua Ward developed a process for its production that involved heating saltpeter, allowing the sulfur to oxidize and combine with water.

The demand for lithium has increased significantly during the last decade as it has become key for the development of industrial products, especially batteries for electronic devices and electric vehicles. This article reviews sources, extraction and production, uses, and recovery and recycling, all of which are important aspects when evaluating lithium as a key resource.

Skip navigation. PowerPoint Presentation. Recent studies indicate there is an urgent need to dramatically reduce the greenhouse gas emissions from heavy industrial applications including cement, steel, petrochemicals, glass and ceramics, and refining. Of these, roughly 40 percent about 10 percent of total emissions is the direct consequence of combustion to produce high-quality heat, almost entirely from the combustion of fossil fuels. This is chiefly because these fuels are relatively cheap, are widely available in large volumes, and produce high-temperature heat in great amounts. In addition, many commercial industrial facilities require continuous operation or operation on demand. The nature of industrial markets creates challenges to the decarbonization of industrial heat. In some cases e. Individual national action on the decarbonization of heavy industry can lead to trade disadvantage, which can be made acute for foundational domestic industries in some cases, with national security implications.

National Emission Standards for Hazardous Air Pollutants (NESHAP)

The demand for lithium has increased significantly during the last decade as it has become key for the development of industrial products, especially batteries for electronic devices and electric vehicles. This article reviews sources, extraction and production, uses, and recovery and recycling, all of which are important aspects when evaluating lithium as a key resource. First, it describes the estimated reserves and lithium production from brine and pegmatites, including the material and energy requirements.

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Although abundant on earth as an element, hydrogen is almost always found as part of another compound, such as water H 2 O , and must be separated from the compounds that contain it before it can be used in vehicles. Once separated, hydrogen can be used along with oxygen from the air in a fuel cell to create electricity through an electrochemical process. Hydrogen can be produced from diverse, domestic resources including fossil fuels, biomass, and water electrolysis with electricity. The environmental impact and energy efficiency of hydrogen depends on how it is produced. Several projects are under way to decrease costs associated with hydrogen production. The carbon monoxide is reacted with water to produce additional hydrogen. This method is the cheapest, most efficient, and most common. Natural gas reforming using steam accounts for the majority of hydrogen produced in the United States annually. A synthesis gas can also be created by reacting coal or biomass with high-temperature steam and oxygen in a pressurized gasifier, which is converted into gaseous components—a process called gasification.

Most of our current sources of energy are obtained from fossil fuels, such as coal, oil, and and economic costs of energy production drives green chemistry Voltage – electrical potential, or tendency of electrons to flow, measured in units of.

Chemical industry

NCBI Bookshelf. Chemistry and chemical engineering are intimately concerned with the generation and use of energy. We need energy for manufacturing, for transportation, for heating and cooling our homes, for lighting, and for cooking. Affordable supplies will become scarcer, and burning fossil fuels produces carbon dioxide that contributes to the greenhouse effect by which solar energy is trapped within the atmosphere and warms the planet. Burning fossil fuels, at least with current technology, also produces oxides of nitrogen and sulfur and other pollutants that affect plants and animals. The problem of having enough clean energy is related to population, standard of living, and the efficiency with which energy is used to provide a unit of economic output. Humans will always need energy, and chemists and chemical engineers will continue to play a central role in learning how to produce and use it. Chemists and chemical engineers will need to join with experts in other disciplines to invent new ways to generate and transport energy for human use and provide for the needs and aspirations of a growing population in a sustainable manner. New ways will also be needed to minimize the energy used for human activities, including manufacturing.

Electricity generation

Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry , it is the stage prior to its delivery to end users transmission , distribution , etc. A characteristic of electricity is that it is not freely available in nature in large amounts, so it must be "produced" that is, transforming other forms of energy to electricity. Production is carried out in power stations also called "power plants". Electricity is most often generated at a power plant by electromechanical generators , primarily driven by heat engines fueled by combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. Other energy sources include solar photovoltaics and geothermal power.

Electric current

When you forget to turn off your car lights, they slowly dim as the battery runs down. Their gradual dimming implies that battery output voltage decreases as the battery is depleted.

Electrical Safety Precautions and Basic Equipment

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How Do Batteries Work?

Research from the University of Illinois and the University of California, Davis has chemists one step closer to recreating nature's most efficient machinery for generating hydrogen gas. This new development may help clear the path for the hydrogen fuel industry to move into a larger role in the global push toward more environmentally friendly energy sources. The researchers report their findings in the Proceedings of the National Academy of Sciences.

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