High cooling water

MONITOR cooling water flow rate to ensure water flow rate Is not too high. Cooling water flow rate is adjusted using vaive B4. if cooling water flow rate falls, supervisor must be notified. 

In the case of an oleum system, initial cooling is done by process water or by cooling tower water. The oleum is cooled to 47-48 °C in this manner. Further cooling to 42 3 °C is carried out by chilled water. This method is followed at sites where ambient temperatures are high (cooling water not available below 30 °C). 

Recognition of site conditions in some developing countries. Most of the SMPR designs presented incorporate a relatively high seismic design level, and would function satisfactorily with relatively high cooling water temperatures. 

The precondenser shown in Figure 13-6 removes the bulk of the mass of steam and hydrocarbons evolved from the vacuum tower. The purpose of the downstream intermediate condensers is to condense the motive steam used in the ejectors. Fouling of the condenser tubes and high cooling water temperature will increase the pounds per hour that the ejectors must handle. 

Increase in cooling water temperature (in vs. out) should be about 5-8°C. If too low this may indieate fouling or b5 assing. If too high cooling water rate may be too low. 

High cooling water return temperature. Above 130°F is considered excessive. 

High cooling water exit temperature override on condensate temperature control... 

Separation of low-molecular-weight materials. Low-molecular-weight materials are distilled at high pressure to increase their condensing temperature and to allow, if possible, the use of cooling water or air cooling in the column condenser. Very low... 

There are two esdsting steam mains. These are high-pressure steam at 41 bar superheated to 270°C and medium-pressure steam at 10 bar saturated at 180°C. Boiler feedwater is available at 80°C and cooling water at 25°C to be returned at 30°C. 

Following the pinch rules, there should be no heat transfer across either the process pinch or the utility pinch by process-to-process heat exchange. Also, there must be no use of inappropriate utilities. This means that above the utility pinch in Fig. 16.17a, high-pressure steam should be used and no low-pressure steam or cooling water. Between the utility pinch and the process pinch, low-pressure steam should be used and no high-pressure steam or cooling water. Below the process pinch in Fig. 16.17, only cooling water should be used. The appropriate utility streams have been included with the process streams in Fig. 16.17a. 

Given a network structure, it is possible to identify loops and paths for it, as discussed in Chap. 7. Within the context of optimization, it is only necessary to consider those paths which connect two different utilities. This could be a path from steam to cooling water or a path from high-pressure steam used as a hot utility to low-pressure steam also used as a hot utility. These paths between two different utilities will be designated utility paths. Loops and utility paths both provide degrees of freedom in the optimization. ... 

Steam-Jet Systems. Low pressure water vapor can be compressed by high pressure steam in a steam jet. In this way, a vacuum can be created over water with resultant evaporation and cooling water, therefore, serves as a refrigerant. This method frequently is used where moderate cooling (down to 2°C) is needed. The process is inefficient and usually is economically justified only when waste steam is available for the motive fluid in the steam jet. 

Both vapor-phase and Hquid-phase processes are employed to nitrate paraffins, using either HNO or NO2. The nitrations occur by means of free-radical steps, and sufftciendy high temperatures are required to produce free radicals to initiate the reaction steps. For Hquid-phase nitrations, temperatures of about 150—200°C are usually required, whereas gas-phase nitrations fall in the 200—440°C range. Sufficient pressures are needed for the Hquid-phase processes to maintain the reactants and products as Hquids. Residence times of several minutes are commonly required to obtain acceptable conversions. Gas-phase nitrations occur at atmospheric pressure, but pressures of 0.8—1.2 MPa (8—12 atm) are frequentiy employed in industrial units. The higher pressures expedite the condensation and recovery of the nitroparaffin products when cooling water is employed to cool the product gas stream leaving the reactor (see Nitroparaffins). 

Eig. 1. Monopressure process using catalytic NO abatement, where BEW = boiler feed water, CH = high level compression, CM = medium level compression, CW = cooling water, and D = makeup driver, EX = expander, and E = filter. 

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