Prize-winning Quiz on Coal Chemical Engineering Knowledge 9

1. c 2. abcd 3. Reducing friction, cooling, preventing rust and corrosion, providing vibration damping, ensuring sealing to prevent leaks, serving a cleaning function, and transmitting power 4. Reciprocating pumps, shielded pumps, self-priming pumps, plunger pumps, metering pumps 5. Combustible substances (combustible gases, vapors, and dusts) must be evenly mixed with air (or oxygen) within a certain concentration range to form a premixed gas; an explosion will occur only when this mixture comes into contact with a fire source. This concentration range is known as the explosive limit

1. The safety devices for releasing pressure in pressure vessels in chemical enterprises include safety valves and (C), etc. A. Drain valve B. Check valve C. Explosion-proof membrane D. Throttle valve 2. Industrial pollution mainly refers to (A/B/C/D): A. Industrial waste gas B. Industrial wastewater C. Industrial waste residues D. Industrial noise 3. The functions of lubricants include: (cooling), (sealing), (corrosion prevention), (rust prevention), (insulation), (power transmission), (removing impurities). 4. Besides centrifugal pumps, what other types of pumps are commonly used in chemical production? There are also positive displacement pumps (such as diaphragm pumps, plunger pumps, gear pumps, screw pumps, metering pumps), as well as siphon pumps and jet pumps. 5. What is the explosion limit? When the vapor of flammable gases or liquids (or flammable dusts) mixes with air and reaches a certain concentration, an explosion occurs upon encountering a source of fire. This range of concentrations at which an explosion can occur is called the explosive limit, and it is usually expressed as a volume percentage of the flammable gas, vapor, or dust in the air. Within the “concentration range in which explosion occurs,” there is a minimum concentration at which an explosion takes place, known as the lower explosive limit ； There is also a highest explosion concentration known as the upper explosion limit. Only between these two concentrations is there a risk of explosion. If the concentration of flammable gases, vapors, or dust in the air is below the lower explosive limit, they will neither explode nor burn when exposed to an open flame ； Above the explosive limit, it will not explode when exposed to an open flame, but it can burn when in contact with air. Because below the explosion limit, air accounts for a large proportion, and the concentration of the combustible material is insufficient ； When it is above the upper limit, there is a large amount of combustible material, yet insufficient air volume. The degree of danger associated with flammable substances mainly depends on the width of their explosive range. The wider the amplitude, the greater the danger. For example: the explosive limit of acetylene is 2.5–80% ； The explosive limit of ethane is 3.22–12.45%. Comparing the two, acetylene is 8.4 times more dangerous than ethane. Therefore, when producing and using such substances, special attention must be paid to preventing leaks, spills, and other forms of loss of material; the airtightness of the equipment must be ensured to prevent air from entering, and safe operating procedures must also be followed

1. The safety devices for releasing pressure in pressure vessels in chemical enterprises include safety valves and (C), etc. A. Drain valve B. Check valve C. Explosion-proof membrane D. Throttle valve 2. Industrial pollution mainly refers to (A) A. Industrial waste gas B. Industrial wastewater C. Industrial waste residues D. Industrial noise 3. The functions of lubricants include: (reducing friction), (cooling), (preventing rust and corrosion), (absorbing vibrations), (sealing to prevent leaks), (purifying), and (transmitting power). 4. Besides centrifugal pumps, what other types of pumps are commonly used in chemical production? There are also mixed-flow pumps, axial flow pumps, vortex pumps, reciprocating pumps, rotor pumps, gear pumps, screw pumps, and more! 5. What is the explosion limit? When the vapor of flammable gases or liquids (or flammable dusts) mixes with air and reaches a certain concentration, an explosion occurs upon encountering a source of fire. This concentration range in which an explosion can occur is called the explosive limit.

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