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Gas cryogenic separation – Level 1: True or False Questions 1. Under normal circumstances, the temperature drop of the gas in the compressor is greater than the temperature rise of the cooling water. (×) 2. When moist air is compressed by a compressor and cooled by a water cooler, the moisture content in the air increases. (×) 3. The compression of gas by a compressor can be divided into three processes: intake, compression, and exhaust. (×) 4. When it is not convenient to use nitrogen or oil-free air, the oxygen compressor can first be tested under low-pressure oxygen conditions. (×) 5. In the event of a fire in the oxygen compressor, it is necessary to shut down the machine immediately, cut off the gas supply at the same time, and trigger an alarm signal. (√) 6. If the nameplate of an asynchronous motor indicates a rated power of 7.5 KW, then the input power of this motor should also be 7.5 KW. (×) 7. Before starting the compressor, check the safety protection devices, instruments, and gauges, and confirm the open and closed status of the valves. (√) 8. A filter made of copper wire or stainless steel wire should be installed at the inlet of the oxygen compressor. (√) 9. The air compressor cooler not only serves to cool but also to separate water. (√) 10. The head of a centrifugal pump increases as the flow rate increases. (×) 11. Water-lubricated oxygen compressors can also compress nitrogen or carbon dioxide. (√) 12. All types of adsorbers must be regenerated according to the specified usage cycle; there is no need to replace them in advance even if the impurity level exceeds the allowed limits. (×) 13. There is no need to specify a regeneration schedule for molecular sieve adsorbers; as long as they are operating properly, the adsorption cycle can be determined independently. (×) 14. The dust removal filter in the air separation unit is primarily used to remove solid impurity particles with a diameter greater than 100 μm. (×) 15. When the water vapor content in the air exceeds the saturated water content, water will condense. (√) 16. The adsorption method used to remove carbon dioxide and water from air is called chemical adsorption. (×) 17. The surface area per gram of silica gel is greater than that per gram of molecular sieve. (×) 18. The phenomenon in which the molecules of a certain substance accumulate on the surface of a porous solid is called adsorption. (√) 19. The substance that is adsorbed is called the adsorbate, while the porous solid surface that carries out adsorption is referred to as the adsorbent. (√) 20. After adsorbing air, molecular sieves can reduce the dew point of the air to below –70°C. (√) 21. Molecular sieves possess thermal stability such that they do not melt even when heated to 700°C. (√) 22. The higher the regeneration temperature of the adsorbent, the more thorough the regeneration, and it does not affect the lifespan of the adsorbent. (×) 23. When the adsorbent and adsorbate remain constant, the static adsorption capacity is independent of temperature and pressure. (×) 24. The higher the flow rate of the adsorbate through the adsorbent bed, the better the adsorption effect. (×) 25. The heating desorption method for adsorbents utilizes the principle that the adsorption capacity decreases as temperature rises, by supplying energy to the adsorbed molecules to cause their desorption. (√) 26. The air entering the heat storage unit (or reversible heat exchanger) has already passed through the final cooler of the air compressor and the nitrogen-water pre-cooler, and its moisture content has not yet reached saturation. (×) 27. The nitrogen gas returning from the distillation tower to the heat storage tank (or reversible heat exchanger) contains very little moisture and carbon dioxide; it is an unsaturated gas. (√) 28. The process of removing the adsorbate from the surface of the adsorbent when adsorption reaches saturation, thereby restoring the adsorbent’s capacity for use, is called desorption (or regeneration). (√) 29. The vacuum desorption method for adsorbents utilizes the principle that as the pressure of the adsorbate decreases, its adsorption capacity also decreases, allowing the adsorbate to detach from the adsorbent and thereby undergo desorption. (√) 30. The absolute humidity of air indicates the amount of moisture present in the air as well as its ability to absorb more moisture. (×) 31. The relative humidity of air refers to the ratio of the moisture content in the air to the saturated moisture content in the air at that temperature. (√) 32. For convenience, tap water can be used as the lubricating water for the cylinders of oxygen compressors with water lubrication. (×) 33. Currently, the only structure available for centrifugal compressors used in air separation is the horizontally split type. (×) 34. In a centrifugal compressor, the greater the gas flow velocity at the outlet of the working wheel, the greater the diffusing effect exerted by the diffuser. (√) 35. The viscosity of lubricating oil is the internal frictional resistance that occurs between the oil molecules when the oil is moved by an external force. (√) 36. When lubricant vapor mixes with air, it will undergo brief combustion (flash ignition) when exposed to a flame; the lowest temperature at which this flash ignition occurs is known as the flash point of the lubricant. (√) 37. The consumption of compressor lubricating oil per square meter is independent of the pressure difference across the compressor piston. (×) 38. The mathematical expression for work is: Work = Force × Distance. (√) 39. The lubricant consumption per square meter at the packing in the high-pressure section of the compressor is much lower than that in the cylinders. (×) 40. The head of a cryogenic liquid centrifugal pump is equal to the head obtained when water is used as the working medium, multiplied by the ratio of the density of water to the density of the cryogenic fluid. (√) 41. A centrifugal compressor imparts velocity to the gas as the high-speed impeller rotates, and increases its pressure through diffuser flow. (√) 42. The gas-liquid phase change is an irreversible process. (×) 43. Phase change between gas and liquid is a chemical change. (×) 44. There are no gases that cannot be liquefied. (√) 45. Gases with a critical temperature of –10°C or higher, but 70°C or lower, are referred to as low-pressure liquefied gases. (×) 46. Gases with a critical temperature higher than 70°C are called high-pressure liquefied gases. (×) 47. Gases with a critical temperature below –10°C belong to low-pressure liquefied gases. (×) 48. Permanent gases cannot be liquefied. (×) 49. Gases are always in a gaseous state above their critical temperature. (√) 50. The mutual transformation between the gas, liquid, and solid states of a substance is a phase transition process. (√) 51. By increasing the pressure on a gas, all gases can be liquefied at room temperature. (×) 52. At a temperature of 0K, the molecules of a substance still keep moving. (×) 53. Objects are made up of matter. (√) 54. Matter is composed of molecules. (√) 55. Matter is composed of atoms. (×) 56. Molecules are composed of atoms. (√) 57. An atom is composed of a nucleus and electrons outside the nucleus. (√) 58. The amount of substance and mass are different. (√) 59. The weight and mass of a substance are different names for the same thing. (×) 60. A liquid substance has a certain volume as well as a certain shape. (×) 61. Gases have a low density, but high compressibility. (√) 62. A substance that contains no impurities is called a pure substance. (√) 63. Material changes are divided into two main categories, namely physical changes and chemical changes. (√) 64. There are as many chemical elements as there are types of atoms in a substance. (√) 65. Compounds are composed of different elements. (√) 66. There are no gaps between the molecules of a solid. (×) 67. Common metal materials are all composed of crystals. (√) 68. Air is a compound composed of various substances. (×) 69. Gases have the properties of compressibility and thermal expansion and contraction. (√) 70. The relationship between thermodynamic temperature and Celsius temperature is: t = T – T0 (where t is the value in Celsius temperature) ； T is the thermodynamic temperature ； T0 is the freezing point temperature of pure water, T0≈273K). (√) 71. The unit symbol for thermodynamic temperature is “℃”. (×) 72. When using bottled oxygen, nitrogen, hydrogen, etc., try to use them up completely to avoid waste. (×) 73. It is strictly prohibited for operators to throw, slide, roll, or collide with gas cylinders when moving them. (√) 74. Gas cylinders do not need to be protected from sunlight in summer. (×) 75. Large amounts of nitrogen and argon gases, which are non-toxic and non-flammable, can be released indoors. (×) 76. Liquid oxygen or liquid nitrogen can also be filled into containers made of carbon steel. (×) 77. New operators, who have not undergone assessment and lack a certification, can occasionally operate independently when there is a shortage of staff. (×) 78. Small cylinders with a nominal volume of 5L do not require a cylinder cap or protective cover. (×) 79. The inspection color code on gas cylinders indicates the year of their regular inspection, with a cycle of 10 years. (√) 80. A loose collar does not affect the filling of seamless gas cylinders. (×) 81. The outlet threads of valves for flammable gas cylinders are left-handed, while those of valves for non-flammable gas cylinders are right-handed. (√) 82. Before starting rotating equipment, it should be turned manually and inspected; it can be started while turning it manually. (×) 83. An iron-carbon alloy with a carbon content of 0.02×10‑2 or greater and 2×10‑2 or less is called steel. (√) 84, 20 steel, and 45 steel all belong to low-carbon steels. (×) 85. Based on their chemical composition, steels can be divided into carbon steel and alloy steel. (√) 86. The harmful impurities in steel are sulfur and phosphorus. (√) 87. The weldability of low-carbon steel is better than that of medium-carbon and high-carbon steels. (√) II. Multiple-choice Questions 1. From the perspective of atomic structure, inert gas atoms have a stable configuration in which their outermost electrons form (A) electrons. A.8 B.6 C.4 D.2 2. From the perspective of atomic structure, the characteristic of metal atoms is that their outermost shell contains (B) electrons. A. 5–6 B. 1–2 C. 5–7 D. 7–8 3. From the perspective of atomic structure, the characteristic of non-metal atoms is that their outermost shell contains (C) electrons. A. 5～6 B. 1～2 C. 5～7 D. 8 4. When a substance undergoes a chemical reaction, (B) remains unchanged. A. Molecule B. Atom C. Ion D. Electron 5. The condition necessary for an atom to be electrically neutral is (C). A. The number of protons in the nucleus is equal to the number of neutrons. B. The number of neutrons in the nucleus is equal to the number of electrons outside the nucleus. C. The number of protons in the nucleus is equal to the number of electrons outside the nucleus. D. The numbers of protons, neutrons, and electrons are all equal. 6. Among the following substances, (D) is referred to as an element. A. Liquefied petroleum gas B. Carbon dioxide C. Oxygen D. Hydrogen 7. The following (A) is called a simple substance. A. Carbon, nitrogen, oxygen, iron, copper, argon B. Methane, acetylene, ethylene oxide, nitrous oxide C. Water, petroleum, liquefied petroleum gas, wood D. Hydrogen chloride, ammonia, hydrogen fluoride, carbon monoxide 8. (A) is a chemical reaction. A. Combustion of oxygen and acetylene B. Dissolution of acetylene in itself C. Separation of oxygen and nitrogen from air D. Conversion of liquid chlorine into chlorine gas 9. An oxidation reaction is a (B) reaction. A. Endothermic B. Exothermic C. Isothermal D. Isobaric 10. The following (B) is a compound. A. Carbon, aluminum, phosphorus, sulfur, copper B. Carbon dioxide, hydrogen sulfide, phosphine, propane C. Oxygen, nitrogen, argon, hydrogen D. Nickel, chromium, titanium 11. In the units of the legal unit system, the unit symbol for the unit whose legal name is “liter” should be written as (C). A. Shi sheng B. Li sheng C. L(1) D. Liter 12. Among the units in the legal unit system, the symbol for the unit of mass in the names of these legal units should be written as (D). A.M B.W C.Wt D.kg13. The unit symbol for thermodynamic temperature is represented by (A). A.K B.0K C.0C D.F14. The symbol for the legal unit of pressure, stress, and strain in our country is (B). A.kg/cm2 B.Pa C.bar D.water column 15. The unofficial unit symbol for pressure, which is kgf/cm2, represents (C). A. 1 standard atmosphere B. 1 physical atmosphere C. kilogram-force per square centimeter D. gauge pressure in kilograms 16. Under standard conditions, 1 L of liquid oxygen weighs (C) kg. A.0.8 B.1.37 C.1.14 D.217. Under standard conditions, 1 L of liquid argon weighs (B) kg. A.0.8 B.1.37 C.1.14 D.218. For an ideal gas, among the three physical parameters of state—pressure p, specific volume ν, and temperature T—it is assumed that the specific volume remains constant; the relationship between p and T is (A). A. The higher the gas temperature, the greater the pressure; temperature and pressure are directly proportional. B. The pressure decreases by the same factor by which the temperature increases. C. If the temperature increases by 10 times, the pressure also increases by 10 1/2 times. D. If the temperature increases by 10 times, the pressure decreases by 10 1/2 times. 19. The maximum value on the gauge scale of a manifold pressure gauge should be (B) times the maximum pressure of the gas cylinder. A.3 B.1.5～3 C.5 D.10 The dial of the pressure gauge on the gas filling busbar must be no smaller than (D) mm. A.25 B.150 C.50 D.10021. The oxygen content in air is (B)×10‑2 (by volume). A.0.93 B.21 C.78 D.1922. The nitrogen content in air is (C)×10－2 (by volume). A.0.93 B.21 C.78 D.1923. The volume fraction of argon in air is (A)×10－2. A.0.93 B.21 C.78 D.1924. The property of oxygen is (D). A. Flammable B. Toxic C. Asphyxiating D. Oxidizing 25. The property of nitrogen is (A). A. Its chemical properties are extremely inert. B. It is toxic. C. It is flammable. D. It acts as an oxidizer. 26. The Fahrenheit scale is represented by (D). A.°C B.K C.Ω D.°F 27. The liquefaction temperature of oxygen is (A)°C below zero (at standard atmospheric pressure). A.183 B.196 C.78 D.18628. The liquefaction temperature of nitrogen is (B) °C below zero (at standard atmospheric pressure). A.183 B.196 C.78 D.186 At standard atmospheric pressure, the liquefaction temperature of argon is (D) °C below zero. A.183 B.196 C.78 D.18630. Under standard conditions, 1 L of liquid helium vaporizes to (C) L of gaseous helium. A.770 B.558 C.702 D.78931. Under standard conditions, 1 L of liquid methane vaporizes to (B) L of gaseous methane. A.770 B.558 C.702 D.78932. Under standard conditions, 1 L of liquid oxygen vaporizes to (B) L of gaseous oxygen. A.770 B.558 C.702 D.78933. Under standard conditions, 1 L of liquid nitrogen becomes (A) L of gaseous nitrogen. A.770 B.558 C.702 D.78934. Under standard conditions, 1 L of liquid argon corresponds to (A) L of gaseous argon. A.770 B.558 C.702 D.78935. The liquefaction temperature of methane is (C) °C at standard atmospheric pressure. A.196 B.183 C.161 D.252.736. The liquefaction temperature of hydrogen is (D) °C at standard atmospheric pressure. A.196 B.183 C.161 D.252.737. The liquefaction temperature of helium is (A) °C at standard atmospheric pressure. A.269 B.186 C.196 D.18338. The volume occupied per unit mass is called (B). A. Density B. Specific volume C. Pounds per square meter D. Specific gravity. 39. The non-standard pressure unit 1 bar = (D) Pa. A.0.5 B.0.07 C.108 D.10540. The illegal pressure unit 14.21 bf/ft2 equals (A) kgf/cm2. A.1 B.760 C.103 D.0.9841. The explosion range of hydrogen in air: the lower limit is (A)×10-2, and the upper limit is 75×10-2. A.4 B.14 C.5.3 D.3542. The explosion range of methane in air: the lower limit is (C)×10-2, and the upper limit is 14×10-2. A.4 B.3 C.5.3 D.7.543. Among the following four types of adsorbents, the one with the largest specific surface area is (D). A. Silica gel B. Activated alumina C. 5A molecular sieve D. 13X molecular sieve 44. The specific surface area per gram of molecular sieve is as high as (B) m2. A. 400～600 B. 800～1000 C. 1000～1500 D. 100～200 45. Regarding the critical temperatures and critical states of the following gases, statement (D) is incorrect. A. The highest temperature at which a gas can be liquefied is called the critical temperature of the gas. B. The critical temperature, critical pressure, and critical density of a gas all have fixed values. C. The higher the critical temperature of a gas, the easier it is for that gas to be liquefied. D. When a gas is in its critical state, there are still distinct differences between the gas phase and the liquid phase. 46. The temperature at which a gas turns into a liquid is called the (A) temperature. A. Liquification B. Exposure C. Melting D. Dissolution 47. The temperature at which a liquid turns into a gas is called the (B) temperature. A. Liquefaction B. Boiling C. Melting D. Dissolution 48. After 200 cycles of adsorption and regeneration, the adsorption capacity of the molecular sieve decreases by (C)%, and this level remains unchanged until 20 cycles of regeneration have been completed. A.10 B.20 C.30 D.60 49. The flash point of the lubricating oil used in the cylinders of piston compressors should be higher than the temperature of the gas compressed by the compressor by (D) °C. A.5 B.20～30 C.10 D.40. The temperature of the air compressor as it enters the adsorption air dryer should not exceed (D)°C. A.50 B.30 C.60 D.40 51. A compressor with a power of 100 KW requires approximately (D) hours of water for cooling when operating at full load (assuming a temperature rise of 10°C in the cooling water). A.12 B.15 C.3 D.8.652. In oxygen generators using the molecular sieve process, the nitrogen-water pre-cooler is of greater importance; the air cooling tower employs two stages of spraying – the first stage uses normal temperature water, while the temperature required for the cooling water in the second stage is around (C)°C. A.15 B.2 C.5 D.10 53. When regenerating a molecular sieve purifier, the temperature of the nitrogen gas exiting the heating furnace is generally controlled at (A). A. 280–320°C B. Around 240°C C. 180°C D. 450°C 54. In winter, open flames are strictly prohibited for heating the areas where empty cylinders and filled cylinders are stored; the temperature for centralized heating should be (B)°C. A.16 B.10 C.20 D.2255. When in use, gas cylinders must not come into contact with objects whose temperature exceeds (C)°C. A.70 B.50 C.60 D.80 56. An increase in sulfur content in steel leads to an increase in the （D） of the steel. A. Fluidity B. Weldability C. Cold brittleness D. Hot brittleness 57. An increase in the phosphorus content in steel leads to an increase in the steel’s (A). A. Cold brittleness B. Weldability C. Fluidity D. Hot brittleness (To be continued..............................)