The factors that affect the material balance in the distillation system are

The reaction depth is expressed in terms of conversion rate: (Gas + Gasoline + Diesel + Coke) t/h ÷ Conversion Rate = -------------------------- × 100% Raw oil volume per hour. The products consist of four components: gas, gasoline, diesel, and coke. The denominator is the crude oil. With the denominator remaining constant, the greater the total amount of these four products, the higher the conversion rate, that is, the greater the degree of reaction. Among these four products, coke is definitely something we do not need; as for the other three, the choice between them depends on the production plan, which gives rise to the three different production plans mentioned earlier, namely the gasoline plan, the diesel plan, and the gas plan. Please note that, regardless of the production scheme, we aim to minimize the coke yield. The reaction depth essentially represents the severity of the chemical reaction. In our catalytic cracking reactions, the more severe the conditions, the more bonds break in the molecules of the feed oil. By analyzing the various chemical reactions that occur during catalytic cracking, it is possible to understand why the yields of the products vary at different reaction depths. However, these chemical reactions are extremely complex and difficult to understand, making them unsuitable for beginners to memorize by rote. Therefore, we try to simplify things by using a hypothetical 28-carbon straight-chain alkane molecule to represent our crude oil molecule, and to see how its bonds will break under three different levels of reaction intensity 1. The reaction depth is too small. In this case, the long carbon bonds break in the middle, which is reasonable as the bond energy in the middle is the lowest. At this point, this long carbon bond breaks apart to form two carbon-14 atoms; carbon-14 is a component of kerosene. Since we do not produce kerosene, it ends up being included in diesel. This indicates that when the reaction depth is relatively low, the yield of diesel is relatively higher. 2. Moderate reaction depth: At this stage, the long carbon bonds are still broken in the middle, but due to the increased severity of the reaction, the carbon-14 produced as a result of these breaks gets broken further, resulting in two carbon-7 molecules. Carbon-7 is a component of gasoline; this indicates that when the reaction depth is moderate, the yield of gasoline is relatively high. Do not forget that the main purpose of our catalytic cracking process is to produce gasoline with a high octane rating. 3. The reaction depth is too great; under such conditions the reaction becomes more intense. After the two bond breaks that occur in the previous scenario, one of the carbon atoms with seven bonds experiences bond breaks at two different positions on it. This results in the formation of one carbon atom with three bonds and two carbon atoms with two bonds each. The carbon atom with three bonds is a liquid hydrocarbon, while the carbon atoms with two bonds are gaseous substances, namely ethylene or ethane. This indicates that when the reaction depth is relatively large, the yields of liquid hydrocarbons and dry gas increase. It should be noted that coke is primarily formed by the condensation of polycyclic aromatic hydrocarbons, and its reaction mechanism has not yet been fully understood. We just need to remember that the greater the degree of reaction, the higher the yield of coke.

That makes sense; when the degree of reaction changes, the distribution of the products also changes. The role of distillation is merely to separate the various fractions, so the material balance in distillation still depends on the reaction