[0026] See figure 1 , An acidic water pretreatment system for an oil refinery is mainly composed of 3 sequentially connected acidic water storage tanks, 2 water-sealed tanks, 2 sets of impurity and oil removal equipment, and 1 set of acidic water top gas degassing and deodorizing equipment 6; The three acidic water storage tanks mentioned above include the impurity and oil removal tank 1, the stabilization tank 2 and the stripper feed tank 3; the 2 water sealing tanks include the positive pressure water sealing tank 4 and the safety water sealing tank 5; 2 sets of impurity removal tanks The degreasing equipment includes a tank-in-tank degreasing and impurity removal equipment 7 and a swirling fine degreasing equipment 8. The tank-in-tank degreasing and impurity removal is built in the impurity degreasing tank 1. The raw acid water is connected to the inlet of the impurity degreasing tank 1 through the degassing tank; the outlet of the impurity degreasing tank 1 and the inlet of the stabilizing tank 2 are both The outlet of the stabilization tank 2 and the inlet of the stripper feed tank 3 are respectively connected by an inverted U-shaped pipe 11; the outlet of the stripper feed tank 3 passes through the cyclone fine degreasing device 8 to remove impurities The inlet of the oil tank 1 is connected; the deacidified water discharged from the outlet of the cyclonic degreasing device 8 is connected to the sour water stripping system. The tops of the 3 sour water storage tanks are equipped with a unified nitrogen-filled pressure control system 9; after the top gas outlets of the 3 sour water storage tanks are merged, they are respectively connected to the inlets of the 2 water-sealed tanks; of which the positive pressure water-sealed tank The bottom outlet of 4 is connected to the impurity and oil removal tank 1, the top outlet of the positive pressure water sealing tank 4 is connected to the sour water top gas degassing and deodorizing device 6; the bottom outlet of the safety water sealing tank 5 is connected to the stabilizing tank 2.
[0027] After the raw material acid water passes through the degassing tank, it enters three acid water storage tanks A, B, and C in sequence. The three acid water storage tanks are operated in series and are connected by two inverted U-shaped pipes 11 of fixed height in sequence. Among them, tank A is the impurity and oil removal tank 1, which provides necessary places for the impurity and oil removal equipment installed in the tank. Tank B is stabilization tank 2. All oil-free sewage in the device (such as sideline three-stage condensate and other unqualified sewage, etc.) are directly returned to the tank, which not only has the effect of homogenization adjustment and stable operation, but also increases The residence time further stands still for deoiling. Tank C is the feed tank 3 of the stripper. Since it does not require a stable liquid level (only one liquid level range is required), the stability of the feed volume of the stripper can be ensured. The three tanks have their own unique functions, and they cooperate with each other to make their overall functions more complete.
[0028] In order to remove the floating oil from the upper part of the acid water storage tank in time, the middle of the three acid water storage tanks are connected to the dirty oil tank. The light oil outlets on the three acid water storage tanks are flush with the design liquid level of the pure water in the acid water storage tank. In order to remove the sludge deposited in the tank in time, a sludge discharge valve 10 is provided at the bottom of the impurity and oil removal tank 1. In order to ensure the safe and efficient operation of the present invention, the present invention also considers many details: connecting the top of the three tanks to each other in the gas phase, the broken siphon pipe at the top of the two inverted U-shaped tubes 11 and the top gas outlets of the three acid water storage tanks Connected; reasonable height of inlet and outlet of acidic water. When designing, an appropriate homogenizing distributor can also be set according to the needs; the inverted U-shaped tube 11 is set to an appropriate height and its height is sequentially reduced. In a preferred embodiment of the present invention, the installation position of the bottom of the inverted U-shaped tube 11 is on the same plane, and the height of the inverted U-shaped tube 11 between the impurity degreasing tank and the stabilization tank 2 is higher than that of the stabilization tank 2 and the stripping tower The height of the inverted U-shaped pipe 11 between the feed tank 3. By setting the height of the inverted U-shaped pipe 11, the liquid level of the three acidic water storage tanks is automatically controlled, so that the impurity and oil removal tank 1 and the stabilization tank 2 have fixed liquid level operations, and the stripper feed tank 3 has 30%~80% liquid level operation.
[0029] The above-mentioned two water-sealing tank technologies are equipped with two water-sealing tanks with different pressure-bearing capacity and functioning independently of each other. Both water-sealing tanks are equipped with demineralized water and purified water inlets. The above-mentioned positive pressure water sealing tank 4 has a design water sealing pressure of 100 mm water column. The top gas of the acid water storage tank goes through a water absorption process in the water sealing tank before the deodorization system: some of the toxic and easily soluble components (such as NH 3 And H 2 S, etc.) is absorbed by the water and returns to the acid water storage tank with the absorbed water (the return line is inserted below the liquid level of the tank); the water seal can be used to maintain a stable positive pressure operation in the acid water storage tank, which is the continuation of the tank top gas Stable deodorization creates the necessary conditions. The above-mentioned safe water sealing tank 5 is breathable, with a design pressure range of -50 to 150 mm water column (specifically, it can be determined by the design pressure of the tank, and it is required to be within the load pressure range of the tank). It can ensure the safety of the acid water storage tank.
[0030] Under normal operating conditions, the pressure of the acid water storage tank is controlled by a unified nitrogen filling pressure control system 9 on the top of the 3 acid water storage tanks. The nitrogen filling pressure control system 9 is matched with 2 water sealing tanks. When the breaking pressure of the safe water seal is lower than that of the positive pressure water seal, it can not only ensure the safety of the acid water storage tank, but also ensure the deodorization effect and the stable operation of the deodorization process. When the positive pressure water seal and the subsequent deodorization system fails, or the pressure of the acid water storage tank is excessively high (or too low) due to the interruption of nitrogen or the failure of the tank top pressure control nitrogen supplement system, independent safety The water seal will work automatically to ensure the safety of the acid water storage tank.
[0031] The present invention is provided with two sets of degreasing and impurity removal facilities that act in layers in sequence, namely, a tank-in-tank degreasing and impurity removal equipment 7 and a cyclone fine deoiling equipment 8. The tank-in-tank degreasing and impurity removal equipment 7 can apply the existing, mature and reliable tank-in-tank impurity degreasing technology. The facility can quickly suspend large particles of dirty oil and settle solid impurities (and concentrate in a certain area in the tank) The function; the facility is installed in the raw material water tank in addition to impurities and oil tank 1. The cyclonic degreasing equipment 8 can also apply the existing, mature and reliable small cyclone tube integration technology to further remove the small particles of sludge that are difficult to separate in the acidic water to ensure the degreasing effect of the acidic water entering the tower; the facility is installed in Raw material pump outlet. Only according to the distribution law of the oily and impurity particles in the acid water, the best effect can be achieved by using the cyclone separation technology to classify and remove the large and small particles; therefore, according to the nature of the source of the acidic water in specific practical applications, determine whether the cyclone fine deoiling is required Equipment 8. In the preferred embodiment of the present invention, the cyclone fine degreasing equipment 8 is mainly composed of an acidic water feed pump and a cyclone fine remover. The outlet of the stripper feed tank 3 passes through the acid water feed pump and the cyclone fine remover. The inlet of the cyclone is connected, the deacidified water outlet of the cyclone fine remover is connected with the acidic water stripping system, and the acid water outlet of the cyclone fine remover is connected with the inlet of the impurity degreasing tank 1.
[0032] The acidic water top gas degassing and deodorizing equipment 6 used in the present invention is mainly a deodorizing tower. The outlet of the amine liquid regeneration device installed in the refinery communicates with the inlet of the deodorizing tower, and the outlet of the deodorizing tower is provided in the refinery. The rich amine liquid pump communicates with the inlet of the amine liquid regeneration device. The amine liquid absorption and deodorization technology is to deodorize the tank top gas through a deodorization tower, and use the solvent regeneration device N-methyldiethanolamine lean liquid as the absorbent to remove H2S and other sulfur-containing odorous gases in the tank top gas. The deodorization effect can be It is guaranteed by reasonable calculation of process design and reasonable selection of operating conditions. The deodorized tank top gas (which has been diluted by nitrogen) mainly contains nitrogen and light hydrocarbons (containing a very small amount of organic sulfur), which can be directly discharged through the top vent of the deodorization tower to meet environmental protection requirements.
