The content of naphthalene in raw gas is usually 10-15g / m3, and most of naphthalene is dissolved in the tar condensed in the gas collector and primary cooler. The naphthalene in the gas has a great influence on the ammonia washing operation. When the content of naphthalene in the gas is high, the naphthalene will deposit together with the scale in the ammonia washing process, which will cause the blockage of the ammonia washing equipment, thus destroying the normal operation of ammonia washing and reducing the ammonia recovery rate. More seriously, the corrosive gases such as ammonia, hydrogen sulfide and hydrogen cyanide enter the crude benzene section along with the gas Serious corrosion and clogging of the equipment for debinding. Therefore, naphthalene in gas must be cleaned according to the requirements of ammonia washing.
At present, the process of naphthalene washing with oil adopted by coking enterprises is generally divided into two types. One is the final cooling of naphthalene washing by oil at the same time of gas cooling and naphthalene washing, which is called cold oil naphthalene washing. The other is washing naphthalene with oil before final cooling, which is called hot oil washing naphthalene. The absorbent used for naphthalene washing is usually tar wash oil produced by our factory. The following is a brief introduction to the cold oil washing naphthalene process.
The gas after the blower enters into the final cold washing naphthalene tower composed of horizontal cooling tube bundle and float valve tray through electric tar precipitator, where the gas is cooled from about 45 ℃ to about 25 ℃, and most naphthalene in the gas is removed.
Since the cooling temperature is lower than the dew point of the gas after primary cooling, water vapor condenses into the naphthalene washing oil while washing naphthalene.
The lean oil from crude benzol section with temperature of 28 ℃ - 30 ℃ enters naphthalene washing section from a tray at the top of the tower. It is in close contact with the gas countercurrent through the float valve tray to absorb naphthalene in the gas, and then enters the cooling section with horizontal tube cooling tube bundle. While being cooled by gas, the oil and gas contact with each other again on the outer wall of the tube bundle, and the naphthalene condensed on the pipe wall is washed. The ammonia oil flows to the bottom of the tower and becomes rich oil with naphthalene and water. Then, it is heated to 85-90 ℃ by self flowing heater, and then sent to three dehydration tanks in series for dehydration. The separated water is directly or through the separation tank into the ammonia rich water tank. The dehydrated naphthalene rich oil is mixed into the benzene washing rich oil. The emulsion discharged from the dewatering tank is sent to the underground vent tank of crude benzene section through the emulsion tank. In order to improve the effect of oil-water separation, appropriate amount of water is added into the first and second dewatering tanks.
The features of cold oil naphthalene washing process are as follows: continuous naphthalene washing; continuous dehydration and regeneration of rich naphthalene washing oil; final cooling of gas and naphthalene washing are carried out in the same equipment; naphthalene washing operation is at a low temperature. Therefore, the effect of washing naphthalene is better.
Factors affecting the effect of naphthalene washing.
1、 The operating temperature of naphthalene washing. When the naphthalene content in the circulating oil is constant, the lower the temperature is, the less the naphthalene content in the balance gas is; when the naphthalene content in the gas is constant, the lower the temperature, the higher the allowable naphthalene concentration of the circulating oil is. Therefore, reducing the operating temperature of naphthalene washing can improve the efficiency of naphthalene washing. The operating temperature of naphthalene washing should not be too low. The temperature of circulating washing oil entering the tower is about 10 ℃ higher than that of gas dew point.
2、 Gas temperature. In order to reduce the load of naphthalene washing tower and reduce the naphthalene content of the gas entering the tower as much as possible, it is necessary to control the temperature of the gas entering the tower. First of all, the operation of the primary cooler should be controlled to make the gas collection temperature after the primary cooler lower than 25 ℃.
3、 Quality of naphthalene washing oil. The quality of naphthalene washing oil is an important factor affecting the effect of naphthalene washing. There are different requirements for the quality of naphthalene washing oil with different processes. Take naphthalene washing with cold oil as an example. According to the experience of many coking enterprises, a set of quality standards has been formed in China's coking enterprises. The details are as follows:
Quality standard of naphthalene in oil washing20℃时密度：≤1.07kg/g，黏度E25≤1.7，270℃前馏出量：≥50%，300℃前馏出量≥85%。
At 20 ℃, the density: ≤ 1.07kg/g, the viscosity e25 ≤ 1.7270 ℃, the distillation amount before 70 ℃ and the distillation amount before 300 ℃ are more than or equal to 85%.
The above content is about the removal method of naphthalene in gas, hope to help you, if you want to buy refined naphthalene, understand the specific refined naphthalene price, welcome to consult our website.