Design And Study Of The Pilot Reactor For Ammoxidation Of Brown Coal

Using the method of ammoxidation of brown coal can produce slow release and hign nitrogen content humic fertilizer. Ammoxidation of brown coal is a typical gas-liquid-solid three phase reaction and gas-liquid mass transfer has remarkable effect on the reaction rate. The reversed jet loop reactor, which has many advantages such as better dispersion effects, high mass transfer performance, a well defined pattern, simple construction and operation, is an ideal reactor for ammoxidation of brown coal.On the basis of the reaction characters of ammoxidation of brown coal, the author designs a set of pilot reversed jet loop reactor with DCS control. The cold model experiment and hot model experiment are carried out.In the cold model experiment, the variability rules of the inner liquid circulation velocity, gas holdup and gas-liquid mass transfer coefficient are discussed in the two phase system. In the three phase system, the variability rules of gas holdup and gas-liquid mass transfer coefficient are studied. The experiment results show that the inner liquid circulation velocity mainly depends on the jet velocity of nozzle and increases with superficial gas velocity. The gas holdup increases monotonously with the increase of jet velocity and inner liquid circulation velocity. There exists an optimum value of gas holdup with the effect of superficial gas velocity, which has a character of firstly increasing then decreaseng. The effect of solid holdup has the similar character. The gas-liquid mass transfer coefficient has a trend of increasing then decreasing with the superficial gas velocity. It increases with jet velocity and inner liquid circulation velocity. The position of outer nozzle has remarkable effect on the gas-liquid mass transfer coefficient and the effect of solid holdup on it is not evident.The gas-liquid mass transfer model and inner circulation flow model of the reactor are also set up in this article. On the basis of the characters of reversed jet loop reactor, the gas-liquid mass transfer model are divided into the mass transfer of the jet region and the main boby region of the reactor. The gas system and liquid system of the jet region (including the inner mix region of the nozzle) use the CSTR model and the main boby region of the reactor use the PFR model with circulation. Then the integrated dynamic mass transfer model is set up.On the basis of Bernoulli equation, the inner circulation flow model is set up below:Using partial experiment data, the relationship between the inner circulation flux and outer circulation flux is regressed:In the hot model experiment, the effects of the reaction temperature, reaction time and ammonia concentration on the ammoxidation of brown coal are primarily studied. The results show that during this experiment condition, the nitrogen content of the product increases with the reaction time, but there exists an optimum reaction time. With the increase of reaction temperature and the ammonia concentration, the nitrogen contents both increase, but are not evidence.This showes that the ammoxidation of brown coal is a typical transfer control process.The results of the cold model and hot model experiments can supply the theory basis for the industrial magnification.