A Method of Calculation of Material and Thermal Balances of Gas Collectors

摘要

The material and heat calculations for a gas collecting main constitute an important part of the plans for condensation sections of byproduct coke plants. The material and thermal balances of gas collecting mains are used to determine starting data for calculating primary gas coolers, ammonia-dephenolization apparatus and other equipment of sections for the recovery of coal-derived chemicals.The methods of calculating the gas collectors known from the literature (1, 2) are based on certain, unjustified (in our opinion) assumptions and have a number of errors, which substantially distort the true picture of the process of cooling of coke-oven gas in the collecting main and also the values of the main parameters of the process. For example, the temperature of ammonia-tar liquor at the outlet of the collecting main is assumed in the literature sources indicated to be independent of the final gas temperature, whereas in the direct-flow motion of heat-carriers the final difference of their temperatures depends on the heat-exchange intensity and contact time. Moreover, in calculations (1, 2) it is assumed that at the outlet of the collecting main the coke-oven gas is saturated with water vapor. Meanwhile, from the analysis of the mechanism of heat-and-mass exchange between gas and water it follows that under conditions in which the water vaporizes the partial pressure of water vapor in the gas cannot be greater than the pressure of saturated water vapor at the temperature of ammonia-tar liquor in the collecting main, i.e., the dew point of the gas cannot be higher than the water temperature (3). The available information indicating that the dew point of the gas is usually higher by 3-5 deg C than the temperature of water flowing from the collecting main (4) may be accounted for by the presence in the gas of finely dispersed water; the pertinent data must be checked by detailed investigations in industrial conditions.