Tanks, storage

We used a portable standard steel pancake pressure tank for our tests. For seasonal and experimental use it s good because it can be inspected and flushed easily, however for a full time system you would be well advised to use a stainless steel ASME code tank. A 316 stainless tank is the best with 304 the next best. 

Your choice will depend on your budget and whether you drain and clean the tank on a regular basis. 

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Clearly, the time chart shown in Fig. 4.14 indicates that individual items of equipment have a poor utilization i.e., they are in use for only a small fraction of the batch cycle time. To improve the equipment utilization, overlap batches as shown in the time-event chart in Fig. 4.15. Here, more than one batch, at difierent processing stages, resides in the process at any given time. Clearly, it is not possible to recycle directly from the separators to the reactor, since the reactor is fed at a time different from that at which the separation is carried out. A storage tank is needed to hold the recycle material. This material is then used to provide part of the feed for the next batch. The final flowsheet for batch operation is shown in Fig. 4.16. Equipment utilization might be improved further by various methods which are considered in Chap. 8 when economic tradeoffs are discussed. 

Figure 9.1 Storage tank fitted with a vapor treatment system. (From Smith and Petela, The Chemical Engineer, no. 517, 9 April, 1992 reproduced by permission of the Institution of Chemical Engineers.)...

In the 1950 s, crude oils were either corrosive (sour), or non-corrosive (sweet). Crudes containing more than 6 ppm of dissolved H2S were classed as sour because, beyond this limit, corrosion was observed on the walls of storage tanks by formation of scales of pyrophoric iron sulfides. 

Solids materials that are insoluble in hydrocarbon or water can be entrained in the crude. These are called bottom sediments and comprise fine particles of sand, drilling mud, rock such as feldspar and gypsum, metals in the form of minerals or in their free state such as iron, copper, lead, nickel, and vanadium. The latter can come from pipeline erosion, storage tanks, valves and piping systems, etc. whatever comes in contact with the crude oil. 

During storage, sediments decant with the water phase and deposit along with paraffins and asphalts in the bottoms of storage tanks as thick sludges or slurries (BS W). The interface between the water-sediment and the crude must be well monitored in order to avoid pumping the slurry into the refinery s operating units where it can cause serious upsets. 

If several widely spaced fields are feeding a single gathering and treatment centre it is common to perform primary separation of gas and oil (and possibly water) in the field. A field station may include a simple slug catcher, temporary storage tanks and pumps for getting the separated fluids to the main gathering and treatment centre. 

Figure 10.29 Fixed roof and floating roof storage tanks...

Storage tanks should always be closely surrounded by bund walls to contain crude in the event of a spillage incident, such as a ruptured pipe or tank, and to allow fire fighting personnel and equipment to be positioned reasonably close to the tanks by providing protected access. 

Johnston D Aboveground storage tank floor inspection using magnetic flux leakage Material Perform t.31 no 10 1990 p.36-39. 

Groundwater. Spkls of refined petroleum product on land, and leaking underground storage tanks, sometimes contaminate groundwater. Bioremediation is becoming an increasingly popular treatment for such situations. 

Storage tanks should have temperature monitoring with alarms to detect the onset of reactions. The design should comply with all appHcable industry, federal, and local codes for a class IB flammable Hquid. The storage temperature should be below 37.8°C. Storage should be under an atmosphere of dry nitrogen and should vent vapors from the tank to a scmbber or flare. 

Fig. 38. Caustic purification system a, 50% caustic feed tank b, 50% caustic feed pumps c, caustic feed preheater d, amonia feed pumps e, ammonia feed preheater f, extractor g, trim heater h, ammonia subcooler i, stripper condenser j, anhydrous ammonia storage tank k, primary flash tank 1, evaporator reboiler m, evaporator n, caustic product transfer pumps o, purified caustic product cooler p, purified caustic storage tank q, ammonia stripper r, purified caustic transfer pumps t, overheads condenser u, evaporator v, evaporator vacuum pump w, aqueous storage ammonia tank x, ammonia scmbber y, scmbber condenser 2, ammonia recirculating pump aa, ammonia recycle pump. CW stands for chilled water.

Storage. For receiving glycerol from standard 30.3-m (8000-gal) tank cars (36.3-t), a storage tank of 38—45-m ((10-12) x 10 — gal) capacity should be employed. Preferably it should be of stainless steel (304 or 316), of stainless- or nickel-clad steel, or of aluminum. Certain resin linings such as Lithcote have also been used. Glycerol does not seriously corrode steel tanks at room temperature but gradually absorbed moisture may have an effect. Therefore, tanks should be sealed with an air-breather trap. 

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