Knowledge about liquefied gas and dimethyl ether

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Comparison of the heat values of 1 kilogram of liquefied gas, 1 unit of electricity, and 1 cubic meter of natural gas: The heat value of 1 kilogram of liquefied gas when burned is 10,800–11,000 kcal; the heat value of 1 cubic meter of natural gas is 9,227 kcal; the heat value of 1 unit of electricity is 860 kcal. Note: 1,000 calories equal 1 kcal, and kcal is an informal term equivalent to kilocalories； 1 calorie (cal) = 4.1868 joules (J); 1 kilocalorie = 4186.75 joules (J). The main methods for producing liquefied gas are as follows: 1. Production from oil and gas fields – During oil extraction, hydrocarbon gases contained in the crude oil are obtained, and during gas extraction, other hydrocarbons present in natural gas are extracted. After preliminary separation and processing, these gases are sent to gas separation plants for further treatment, resulting in the production of propane and butane. Propane and butane are liquefied under certain pressures or by freezing them to specific temperatures, and then stored in separate tanks. Producers can sell propane and butane separately, or, as per the customer’s request, mix them in certain proportions to create LPG that meets quality standards for sale. 2. LPG produced in refineries is a by-product of the petroleum refining process. Typically, during the processing of crude oil in units such as atmospheric and vacuum distillation, thermal cracking (a process that has been largely phased out in China), catalytic cracking, catalytic reforming, hydrocracking, and delayed coking, hydrocarbon gases are generated. After passing through absorption and stabilization processes, these gases are separated into dry gas (lean gas) and rich gas at a certain pressure. The main components of dry gas are methane and non-hydrocarbon gases, with small amounts of ethane, ethylene, etc. as well. Typically, such gases are sent directly to gas tanks for collection, and then distributed to the heating furnaces in refineries as fuel ； The main components of rich gas are propane, propylene, butane, and butenes, along with small amounts of pentenes and non-hydrocarbon compounds; under certain pressures, this gas becomes LPG, which is primarily composed of propane, propylene, butane, and butenes. LPG in our country’s refineries is mainly obtained from catalytic cracking units. 3. Produced in ethylene plants: During the process of producing ethylene through the cracking of light oil or light hydrocarbons, LPG components are also generated. Due to the production objectives of ethylene plants, the quality of LPG produced in such plants is relatively poor, with generally high levels of C4 components. If the refinery and the ethylene plant are part of the same organization, it is usually possible to properly blend these two types of LPG with different origins in order to obtain LPG that meets **the standards. Comparative experiments on the combustion of liquefied petroleum gas (LPG) and LPG containing dimethyl ether (DME). I. Experimental equipment: Two sets of LPG cylinders and stoves, a stopwatch, and an electronic scale. II. Experimental Methods (1) Two gas cylinders were sequentially filled with pure LPG and LPG containing 22% DME, and their weights were measured respectively. (2) Fill two kettles with 3000 grams of water each, and weigh them separately ； (3) Measure the water temperature separately ； (4) Measure the temperature when water boils, using as a reference the sound emitted by the kettle, or the fact that the temperature reaches 100°C at that point. (5) Weigh the liquefied gas cylinder again. Calculate the LPG usage and the LPG usage containing DME. III. Experimental Results (water temperature: 28.5°C)
Number of experiments | Burning time (seconds) | LPG containing 22% DME (kg) | LPG (kg) | Remarks
---|---|---|---|---
First experiment | 512 (DME) | 552 (LPG) | 9.88–9.82 = 0.06 | 9.75–9.70 = 0.05 | Two identical stoves
Second experiment | 643 (DME) | 465 (LPG) | 9.82–9.78 = 0.04 | 9.70–9.66 = 0.04 | Two identical stoves
Third experiment | 493 (DME) | 454 (LPG) | 9.78–9.74 = 0.04 | 9.66–9.62 = 0.04 | Same stove

IV. Conclusion
At a water temperature of 28.5°C, the amount of liquefied gas required to boil one kilogram of water is 14.44 g, while the amount of liquefied gas containing 22% DME required is 15.55 g. The results for the second and third experiments were identical, indicating that liquefied gas containing 22% DME has a combustion effect similar to that of pure liquefied gas.