Deodorization batch

Figure 4.9 Batch deodorization process. (Source Courtesy of DeSmet Group, Antwerp, Belgium.)...

Today, even for small capacity plants (10-50 TPD), semicontinuous deodorizers are clearly more suitable than conventional batch deodorizers. The shorter hold-up time in a semicontinuous deodorizer is a good argument in its favor, even in cases when small capacities with very frequent feedstock changes are required. Compared with continuous systems, the main advantages of semicontinuous deodoriza-tion are its shorter time for feedstock change as well as its much lower cross contamination. Heat recovery is, however, less efficient than in continuous operation. 

Batch deodorizing is still operated in some plants, the main advantage being somewhat lower capital investment and simplicity of operation in-... 

The mathematics for batch deodorization were developed by Bailey (1951) and modified by Szabo Sakardi (1958) by the introduction of an activity coefficient A to allow for the deviation of fatty acid solutions from the ideal, thus producing the following equations ... 

The batch deodorizer is a very useful vessel for a refiner. It can be used for small parcels of oil which, if introduced into the programme of a semi-continuous or particularly a continuous deodorizer, would reduce the latter s efficiency. Further, the chance of contamination can virtually be eliminated, which is of value in a plant processing oils whose special properties would be affected by very low levels of contamination. 

The modern batch deodorizer has a capacity from 5 to 30 tonnes. It is still frequently constructed of mild steel, though stainless steel is preferred. It is heated by high-pressure steam or, in some cases, by Dowtherm or thermal oil, and its vaporization efficiency has been improved by the inclusion of mammoth pumps and effective head space insulation to prevent refluxing. A vapour scrubber can be installed to recover oil and fatty acids from the distillate vapour. The complete batch cycle time is between 6 and 10 h depending on the feedstock. The unit is not, however, suitable for physical refining and it is expensive to operate compared with continuous and semi-continuous plant. 

The treatment given to the oil is primarily dependent on the type of deodorizer installed in the plant. In plants using relatively low-temperature (180-200 C) batch deodorizers, the oil is neutralized with caustic soda, washed, dried, bleached and... 

Both batch and continuous deodorization processes are used. The batch deodorizer is the earliest and most simple type of process. It generally... 

Hence as the interfacial area or the length of contact time between the bubble and the oil is increased, the vaporization efficiency increases and the vapor-phase partial pressure of the volatile component approaches the value in equilibrium with the liquid phase. Batch deodorizer studies [3] have suggested that practical values for the vaporization efficiency are in the range of 0.7-0.9, which is consistent with values for steam distillation in other industries. 

The temperature of the oii during steaming is the most critical process parameter during deodorization, and if the temperature falls below 340°F (170°C) very little deodorization actually occurs. For batch deodorization the typical operating temperature ranges from 360 to 465°F (180-240°C). For semicontinuous deodorizers... 

Batch deodorization is best suited to low capacity plants where the flexibility of the process can be exploited to handle a multiplicity of oil products with minimal cross-contamination. Vessel oil capacities range from 25,000 to 50,000 lb, and overall refinery throughput will typically be on the order of 250,000 Ib/day. The typical issues associated with this type of installation are the high steam usage occasioned by the continual need to reheat the equipment, the poor opportunities for heat recovery, and the peak demands on services that operating a number of batch units in parallel can develop. 

Heating and cooling of a batch deodorizer are normally achieved by way of either internal coils or external forced circulation heat exchangers. The latter... 

In general, batch deodorizers have a typical turnaround time of approximately 8 h, with the oil being subjected to approximately 4 h of stripping. 

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