Deodorization continuous

Historically, the standard deodorizer held 60,000 lb of oil (one railroad tank car). Except for refineries making only a few kinds of oil, as for export, building of continuous deodorizers slowed with the advent of Just-In-Time (JIT) delivery, supplier self-certification, and customers buying on the basis of their projected production schedules. This has led to development of improved batch-continuous systems, which are designed to handle many batches of different oil blends per day, with minimum cross-contamination and delays for process. 

Fig 34.31. Cut-away drawing of DeSmet Qualistock Continuous Deodorizer. (Courtesy of Desmet Ballestra Oils and Fats, Brussels, Belgium.)... 

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

The continuous deodorizer performs the same basic functions but is deseed for a larger operation, requiring few feedstock changes (Fig. 4.10). It is generally the best choice for modem integrated refineries [4]. 

Direct heat recovery is the most efficient, with up to 85% of the heat recoverable. It is usually applied in continuous deodorizers, whereas the indirect heat recovery system is used preferentially in semi-continuous deodorizers with frequent feedstock changes. The efficiency of the indirect heat recovery depends largely on the type and design of the system (Figure 12). 

Continuous deodorizers are generally preferred for high-capacity plants with few stock changes. The main advantages are the moderate investment costs, the possibility of high heat recovery and the easy maintenance. 

There are several configurations of continuous deodorizers horizontal vessels, vertical tray-type deodorizers, and packed columns. 

Vertical tray-type deodorizers are probably the most commonly used type of continuous deodorizers. Their design is based on a series of trays or compartments stacked vertically in a cylindrical shell, with each tray designed for a specific task (e.g., De Smet—Figure 23). All operations, heating, deodorization, and heat... 

There are three types of deodorization operations. The batch process is the least common, due to its low efficiency and inconsistent product quality. Semi-continuous and continuous deodorizers have improved processing efficiency. There are several configurations of the continuous deodorizer, including singleshell cylindrical vessel type, vertically stacked tray type, and the thin-film packed column type. This last provides excellent fatty acid stripping with minimum use of steam, but it achieves neither desired heat bleaching nor effective deodorization due to the relatively short retention time. A retention vessel has to be used after the column distillation (De Greyt and Kellens 2000). 

With the advent of high energy costs, it has become attractive to recover some of the heat contained in the deodorized oil by cooling with incoming oil. Semicontinuous and continuous deodorizers can be easily equipped for this, and most recent installations include this feature. About 40-50% of the process heat required can be recovered in semicontinuous operations. 

Gavin (1978) derived an equation for the operation of continuous deodorization where... 

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. 

Plants are today available with capacities ranging from 5000 lb per h (about 50 tonnes per day) to 60 000 lb per h (over 600 tonnes per day) and are automated to a very high degree. All the semi-continuous and continuous deodorizers are available, suitably modified, for physical refining. 

Figure 4.10 Continuous deodorization process. (Source Courtesy of DeSmet Group, Antwerp, Belgium.)...

There are two basic configurations of continuous deodorizers. The first, shown in Figure 5, is very similar to the design of the semicontinuous units with a number of trays or compartments in which the oil is deodorized. As distinct from the semicontinuous deodorizers, the flow of oil through the unit is continuous, with the oil retention time on each tray or in each compartment simply being a function of the volume of the tray or compartment. Valve or sieve trays are most commonly employed in this deodorizer configuration. Typically tray or compartment residence times are comparable with those of semicontinuous units. 

The second configuration of the continuous deodorizer (Fig. 6) relies on the use of a packed column design to generate a thin film system. The packing... 

Both types of continuous deodorizers can be configured via external heat exchangers to readily achieve 75-80% heat recovery. 

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