Vessel Operations

Creep of Thick-walled Cylinders. The design of relatively thick-walled pressure vessels for operation at elevated temperatures where creep caimot be ignored is of interest to the oil, chemical, and power industries. In steam power plants, pressures of 35 MPa (5000 psi) and 650°C are used. Quart2 crystals are grown hydrothermaHy, using a batch process, in vessels operating at a temperature of 340—400°C and a pressure of 170 MPa (25,000 psi). In general, in the chemical industry creep is not a problem provided the wall temperature of vessels made of Ni—Cr—Mo steel is below 350°C. 

Pressure Vessels. High pressure tanks are vessels operating above 15 psig. These are reaHy pressure vessels and the term high pressure tank is basicaHy never used. Pressure vessels are a speciali2ed form of container treated separately from tanks by aH codes, standards, and regulations. 

Butyl slurry at 25—35 wt % mbber continuously overflows from the reactor through a transferline to an agitated flash dmm operating at 140—160 kPa (1.4—1.6 atm) and 55—70°C. Steam and hot water are mixed with the slurry in a nozzle as it enters the dmm to vaporize methyl chloride and unreacted monomers that pass overhead to a recovery system. The vapor stream is compressed, dried over alumina, and fractionated to yield a recycle stream of methyl chloride and isobutylene. Pure methyl chloride is recovered for the coinitiator (AlCl ) preparation. In the flash dmm, the polymer agglomerates as a coarse cmmb in water. Metal stearate, eg, aluminum, calcium, or zinc stearate, is added to control the cmmb size. Other additives, such as antioxidants, can also be introduced at this point. The polymer cmmb at 8—12 wt % in water flows from the flash dmm to a stripping vessel operated under high vacuum to... 

Rotating equipment, except brick-hned vessels, operated above ambient temperatures is usually insulated to reduce heat losses. Exceptions are direct-heat units of bare metal construction operating at high temperatures, on which heat losses from the shell are neces-saiy to prevent overheating of the metal. Insulation is particularly necessary on cocurrent direct-heat units. It is not unusual for product cooling or condensation on the shell to occur in the last 10 to 50 percent of the cylinder length if it is not well insulated. 

Carbon steel piping, valves, structurals and vessels operating at cryogenic and ambient temperatures. 

Aerobic reactor A reaction vessel operating under aerobic conditions with sterile air being used as the source of oxygen in dissolved state. 

The potential for interference with the normal operation and maintenance of a process vessel is high. A major design effort is required to overcome this disadvantage. All aspects of the process vessel operation must be considered. Lines of sight for process vessel and crane operators, access for crane-held ladles and buckets, process vessel movements, and maintenance access must be accommodated by the enclosure design. This is more easily achieved in a new installation. 

Enclosure design on retrofit cases becomes very difficult and may require a compromise between process vessel operation and fume capture performance. 

Vessel operates at atmospheric pressure and has an adequate vent sy.stem. 

For the larger diameter storage vessels operating with a few ounces water to 1 psig, the selection of a design pressure must also consider the system surges in relation to the normal conditions. For example, a storage tank 20... 

Vessels operating below atmospheric pressure are designed for full vacuum regardless of the actual vacuum. 

MAWP is calculated using nominal standard steel plates (but could be other metal—use code stresses) thickness, using maximum vessel operating temperature for metal stress determinations. See Ref [1] Par. UG-98. 

Vessels operating completely filled with liquid must be equipped with liquid relief valves, unless otherwise protected (Par. UG-125-3(g). 

A small hole has been deliberately placed in a vessel near the top to provide a controlled vent for a nitrogen purge/blankeL The hole is 0.2-inch diameter witli the vessel operating at 150 psig at 100°F. Determine the flow through this vent hole. Assume it acts as a sharp edged orifice. 

The calculation of heat transfer film coefficients in an air-lift bioreactor is more complex, as small reactors may operate under laminar flow conditions whereas large-scale vessels operate under turbulent flow conditions. It has been found that under laminar flow conditions, the fermentation broths show non-Newtonian behaviour, so the heat transfer coefficient can be evaluated with a modified form of the equation known as the Graetz-Leveque equation 9... 

Design pressures of vessels operating at 0-10 psig and 600- 1000°F are 40 psig. 

Assume that the pilot-scale and full-scale vessels operate with the same inlet density. Then p cancels in Equation (1.57) and... 

The correlation of Norwood and Metzner shows to be a complex function of the Reynolds number, the Froude number, the ratio of tank-to-impeller diameter, and the ratio of tank diameter to liquid level. However, to a reasonable first approximation for geometrically similar vessels operating at high Reynolds numbers. 

Vessel mptures can also occur when a higher-temperature liquid or solid is combined with a cooler low boiling liquid, transferring sufficient heat from the hotter material to the colder material such that the colder material rapidly vaporizes. No chemical reactions are involved instead, the explosion occurs because the cooler liquid expands as it is converted to vapor, creating high pressures. These are called physical explosions. A common example is a steam explosion, which occurs when liquid water is accidentally introduced into a process vessel operating at an elevated temperature. If the hotter material is above the superheat limit temperature of the evaporating liquid, initial confinement by a vessel is not required to create an explosion pressure wave. 

A formed section would normally be used for the transition between a cylindrical section and conical section except for vessels operating at low pressures, or under hydrostatic pressure only. The transition section would be made thicker than the conical or cylindrical section and formed with a knuckle radius to reduce the stress concentration at the transition, Figure 13.11. The thickness at the knuckle can be calculated using equation 13.46, and that for the conical section away from the transition from equation 13.45. 

The resulting schedule is shown in Fig. 9.3. The bold numbers in Fig. 9.3 represent freshwater used and the normal numbers wastewater reused. One would notice in the figure that operation 2 sends 500 kg of wastewater to the central storage vessel. Operation 1 uses all of the 500 kg of water. Operation 4 directly reuses 500 kg of wastewater from operation 2. 

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