Calculation of focal length
Thread Content
1. Calculation of coking ratio: The coking ratio (i.e., coal-to-coke ratio) is the percentage of dry coke produced from dry coal fed into the furnace as a result of high-temperature carbonization, relative to the amount of coal fed in; generally, this ratio ranges from 72% to 78%. The coking rate mainly depends on the coal quality, and is also influenced by the coking conditions and the type of coke oven. There is a strong correlation between the volatility of coal fed into the furnace and its coking rate. Generally, the higher the volatiles in the coal fed into the furnace, the lower the coking rate (i.e., the coal-to-coke ratio is also higher), and vice versa. There are many methods for calculating the coking rate; it is necessary to take into account the actual circumstances, and the relationship between the volatiles and ash content of the coal fed into the furnace and the coke produced can be used to determine the coking rate. 2. Calculation method 1: The coking rate is determined using the relationship between the ash contents of coal and coke: KA = (Ad_coal/Ad_coke) × 100%. 3. Calculation method 2: The coking rate is calculated by utilizing the relationship between the volatile matter contents of coal and coke: KV = [(100 – V_coal)/(100 – V_coke) × 100%] + b. 4. Calculation method 3: K = 100 + b – Vd. Here, b is a correction factor that represents the increase in carbon content resulting from the secondary decomposition that occurs in the upper space of the coke oven’s carbonization chamber after the volatile matter in the coal escapes. This value is influenced by factors such as the volatile matter content of the coal fed into the oven, the structure of the coke oven, and the operating procedures used in the oven. Typically, b is set at 2.2%–3.9%; in this paper, the value of b is taken as 2.8%. 5. Analysis of the coking yield calculation results: Based on the laboratory analysis data of coal and coke from a certain company, it was found that in the first quarter of 2009, compared to the fourth quarter of 2008, the volatility of the coal fed into the furnace increased by about 4 percentage points, which resulted in a decrease in the coking yield by approximately 3.5 percentage points. In other words, for every ton of dry coal used for coking, about 35 kg less coke was produced.
The typical focal length ratio is 72% to 78%. It can also be more specific: for top-mounted coke ovens, the coke yield is generally between 75% and 78% ； For rammed coke ovens. The foci formation rate is between 72% and 75%. The reason is that rammed coke ovens can use more low-viscosity coal with high volatile matter compared to top-charged coke ovens. As the original poster said, the higher the volatile matter content of the coal fed into the oven, the lower the coking rate.
The first calculation method mentioned by the original poster is derived from the conservation of ash content during the coking process of coal； The second calculation method mentioned by the original poster is derived from the material balance of fixed carbon and ash during the coking process of coal ； I’m not familiar with Method 3; it’s the first time I’ve seen it. Could you explain it?
The coking rate can also be measured on-site. Some coke ovens can measure the mass of coal fed into the oven and that discharged from it (in tons, a). Once the carbonization chamber is emptied, the coke produced is not placed on the coke shelf; instead, it is transported to a weighing station by vehicle where its mass is determined (in tons, b). The coking rate of the dry coal is then calculated based on the moisture content of both the coal fed into the oven and the coke produced.
As Mr. “Wang Shaobo” on the second and third floors said, formula 2, formula 3, along with on-site measurement methods, can be used to determine the coking rate of coke with relatively high accuracy. But all of that requires coke specifications, such as the ash content in Equation 1. The volatile matter according to Formula 2, as well as the mass of coke measured on-site, etc. That seems a bit like hindsight. Since the coke has already been produced, what’s the point of calculating the coking ratio? Isn’t the daily output of coal and the production volume of coke quite obvious? And so, Formula 3 is born! Formula 3 is an empirical formula. It is derived from formulas one and two, as well as accurate measurement methods, and varies depending on the production conditions. Its advantage is that it allows for the prediction of coke production in advance. Thus, the coal blending cost is calculated during the coal blending process. Profits, etc.
I have two more formulas: 1. How to determine the coking degree using the relationship between the volatiles of coal and coke? K=99-5/6Vdcoal. In equation (3), Vdcoal represents the dry-base volatiles of the coal, while the dry-base volatiles of coke, Vdcoke, are assumed to be 1.2%. 2. How is the coking rate determined from coal quality and coking operation conditions? K=103.17-0.75Vdcoal-0.0067tJ. In the formula, Vdcoal represents the dry-base volatiles of the coal loaded ； tJ is the center temperature of the coke cake (°C, measured 15 minutes before coke pushing).
Is Formula 1 applicable to all furnace types and all coking methods? How is the center temperature of the coke cake determined using Formula 2?