Tank blowdown

The impact of cold GR-S was quite pronounced. The U.S. government edicted that all of the emulsion SBR plants switch to the cold process. This required addition of refrigeration capacity in these plants as well as other significant changes, such as insulation of reactors, improved vacuum to reduce oxygen that retards polymerization, and the heating of latex in blowdown tanks to aid in the disengagement of butadiene when transferred to the flash tanks. 

Another example of an unsteady state condensible blowdown system is the design for a phenol condensible blowdown tank. A blowdown tank is used in phenol treating plants to handle streams containing phenol and heavy hydrocarbons (lubricating oil stocks). The blowdown tank is illustrated in Figure 4. The design basis is as rollows ... 

Figure 4. Condensible blowdown tank - phenol service.

A condensible blowdown tank, designed on a similar basis to that described above for phenol, may be provided in other services where a conventional condensible blowdown drum would not be acceptable (e.g., due to effluent water pollution considerations). Examples of such cases are methyl ethyl ketone (MEK) and dimethyl formamide (DMF). A suitable absorbing material is specified (e.g., a lube oil stock for MEK water for DMF), and the design must include consideration of maximum permissible operating temperatures to prevent excessive vapor evolution or the boiling of water. 

It is important to note that in some installations where local pollution regulations would not permit venting a condensible blowdown tank in toxic service to the atmosphere, a pressure drum or sphere, vented to a flare, may be necessary. 

Blowdown and drains may be taken to either a sump or blowdown tank prior to discharging into the drains. The purpose of this is to reduce the temperature by dilution and dissipate the pressure to prevent damage to the drains. 

As another example, consider vessels that are under a positive pressure. For all pressure vessels, including storage tanks, a vent system must be installed to protect the vessel from rupturing. The vent goes to either a flare or a blowdown tank. These... 

Equipment that may spill inflammable materials Blowdown tanks Burning flares Settling ponds... 

The blowdown tank is located on the south side of the plant where winds will not generally carry any spills over the plant. 

A scrap rubber batch is cooked for up to 24 hours and then discharged into a blowdown tank where water is added to facilitate subsequent washing operations. Digester liquor is removed by a series of screen washings. The washed rubber is dewatered by a press and then dried in an oven. Two major sources of wastewater are the digester liquor and the washwater from the screen washings. 

Corrosion. The tubes in the LTV evaporator were installed with Swenson rubber grommet packing commonly used for Karbate tubes in acid evaporators. This both insulated the tubes from galvanic corrosion and allowed nondestructive removal for weighing. Corrosion rates were estimated both from weight loss of the tubes and from International Nickel Co. test spools located both in the vapor space and immersed in the liquid in the blowdown tank. 

Fig. 1. ASPEN-Plus PFD of carbonic acid pretreatment process as analyzed in this study. Bl, pretreatment reactor (Rstoic) B2, screw mixer B3, blowdown tank and screw conveyor B4, slurrying tank and tank agitator B5, cooler B6, reflux drum and condenser B7, feed pump B8, in-line C02 mixer B9, heater BIO, pneumapress filter Bll, heat exchanger B12, loading pump B13, C02 compressor B14, primary filtrate pump.

The PVC slurry and unreacted VCM from the polymerization reactors are fed to the blowdown tank—the intermediate buffer between the discontinuous polymerization and the continuous degassing and drying unit. 

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