Cooling flow diagram

A typical flow diagram for pentaerythritol production is shown in Figure 2. The main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive by-product formation and/or reduced yields of pentaerythritol (55,58,59). The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 h at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the Hquors by subsequent filtration. 

Fig. 11. Spheripol process flow diagram (131). CW = cooling water. Courtesy of Gulf PubHshing Co.

Eigure 3 is a flow diagram which gives an example of the commercial practice of the Dynamit Nobel process (73). -Xylene, air, and catalyst are fed continuously to the oxidation reactor where they are joined with recycle methyl -toluate. Typically, the catalyst is a cobalt salt, but cobalt and manganese are also used in combination. Titanium or other expensive metallurgy is not required because bromine and acetic acid are not used. The oxidation reactor is maintained at 140—180°C and 500—800 kPa (5—8 atm). The heat of reaction is removed by vaporization of water and excess -xylene these are condensed, water is separated, and -xylene is returned continuously (72,74). Cooling coils can also be used (70). 

Urea reacts with himing sulfuric acid in an exothermic reaction that needs agitation and cooling. After completion of the reaction, excess sulfur trioxide is removed by dilution or by other methods (45,46). A flow diagram of the process is shown in Figure 1. 

Fig. 9. Pyroform process flow diagram (38). Ref = refrigeration, CW = cooling water, and BFW = boiling feedwater.

Fig. 51eft. Schematic flow diagram of an ethylene plant using naphtha feedstock. CW = cooling water QW = quench water QO = quench oil LPS = low pressure steam MPS = medium pressure steam SPS = super high pressure steam C3R = propylene refrigerant and...

Figure 3.4.4-6 presents a flow diagram of a simplified emergency cooling injection system. It is activated by a safety injection signal (SIS) which... 

A reversible cycle with turbine expansion split into two steps (high pressure, HP, and low pressure, LP) is illustrated in the T, s diagram of Fig. 4.3. The mass flow through the heater is still unity and the temperature rises from T2 to Tt, = Tq hence the heat supplied (3b is unchanged, as is the overall isentropic temperature ratio (x). But cooling air of mass flow i//H is used at entry to the first HP turbine (of isentropic temperature ratio. xh) and additional cooling of mass flow is introduced subsequently into the LP turbine (of isentropic temperature ratio Xl)- The total cooling flow is then i/( = i/ h + >h.-... 

In planning a control system, a flow diagram is needed to indicate what may influence each item of plant. In many diagrams it will be seen that complexity arises and two items work in conflict. A typical instance is the cooling and dehumidifying of air, to a room condition lower than design, with concurrent operation of a humidifier. 

A schematic flow diagram of this process is presented in Figure 12 which depicts three catalyst beds operating in series. Fresh make-up gas is mixed with total recycle and fed to the first bed. The effluent from the first bed is partially cooled so that when it is combined with another portion of cold make-up, the mixture is at or above the initiating reaction temperature. The mixture is fed to the second bed. This procedure is continued to the third and subsequent beds. 

Energy balances are needed whenever temperature changes are important, as caused by reaction heating effects or by cooling and heating for temperature control. For example, such a balance is needed when the heat of reaction causes a change in reactor temperature. This is seen in the information flow diagram for a non-isothermal continuous reactor as shown in Fig. 1.19. 

Figure 21.11 Flow diagram and notation for three-stage FBCR with cold-shot cooling...

During the production of paint, it is important to keep control of the temperature. Due to the high shear forces a substantial amount of heat is produced especially in the pearl mill. Some ingredients in the paint are sensitive to heat, e.g. solvents which will have the risk to flash off. Therefore additional cooling is normally needed in this operation. Figure 9 shows a flow diagram of paint production in a factoiy. 

Figure 15.22. Batch cooling crystallisation of melts flow diagram for the Proabd refiner...

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