Analysis of treatment measures for oily wastewater in refining edible oil
The crude oil purchased from degumming and alkaline refining processes enters the filter through storage tanks, removes various impurities in the crude oil, and then feeds into the heater. After heating to a certain temperature, the crude oil enters the mixer together with the quantitative phosphoric acid. After full mixing, it enters the hydration reactor, and then neutralizes the mixture by adding alkali. After reaction, the oil and soap foot are separated by centrifuge. The light phase oil enters the mixer and is washed twice by adding hot water. Then the soap water is removed by centrifuge. The soap foot pumps the soap foot tank, and finally the clean oil comes out. The air dryer is dehydrated and enters the next stage.
1.2 The degummed alkali refinery oil dried in the decolorization process is heated and mixed with clay into the decolorization tower for decolorization treatment. After bleaching, the oil pump is filtered into the leaf edible oil filter (three alternately filtered). The filtered turbid oil is beaten back to the decolorization tower and then filtered. The decolorized oil is filtered by a safety filter and sent to the deodorization process. 1.3 After deodorization, the oil enters the heat exchanger for heat transfer. The heat exchanged oil is heated by the heater to the required temperature for deodorization and then goes into the pre-deodorization tower for deodorization and thermal decolorization. In the pre-stripping tower, most free fatty acids are rectified. After heat exchange with decolorized cold oil, they are cooled to safe temperature by cooler, polished, filtered and measured, and then sent to the product tank for storage.
At present, the most important and stable method to treat vegetable oil wastewater in China is biological method, which can degrade oil effectively. Compared with physical method, it has obvious treatment effect and less secondary pollution. At present, the utilization rate of biological method in China has reached 80%. Biological treatment includes anaerobic biological treatment process and aerobic biological treatment process [2-4]. The comparison of biological treatment processes is shown in Table 2. According to the advantages and disadvantages of bio-treatment process of oily wastewater and the characteristics of refinery process oily wastewater, combined with its own economic benefits, the enterprise ultimately plans to adopt SBR method.
The so-called sequential batch has two meanings: one is that the operation is carried out in a sequential and intermittent manner in space. Because most of the sewage is discharged continuously and the flow fluctuates greatly, at this time SBR is at least two or more pools, and the sewage enters each reactor sequentially, and the relative relationship between them is secondary. Secondly, the operation time of each SBR reactor is also intermittent, which can be divided into five stages according to the order of operation. Among them, from the influent, reaction, sedimentation, drainage and sludge discharge to idle end is a running cycle.
In a running cycle, the running time of each stage, the change of the volume of mixed liquid in the reactor and the running state can be flexibly controlled according to the characteristics of the specific sewage, the quality of the effluent and the requirements of the operation function. For a single SBR, there is no obstacle to control in space, only effective control and transformation in time, that is to say, it can meet the requirements of multiple functions, and its operation is very flexible. Because SBR has at least two or more pools, the effluent from this project can be considered as continuous discharge.