Steam requirements, actual

UK. = Light key component in volatile mixture L/V = Internal reflux ratio L/D = Actual external reflux ratio (L/D) ,in = Minimum external reflux ratio M = Molecular weight of compound Mg = Total mols steam required m = Number of sidestreams above feed, n N = Number of theoretical trays in distillation tower (not including reboiler) at operating finite reflux. For partial condenser system N includes condenser or number theoretical trays or transfer units for a packed tower (VOC calculations) Nb = Number of trays from tray, m, to bottom tray, but not including still or reboiler Nrain = Minimum number of theoretical trays in distillation tower (not including reboiler) at total or infinite reflux. For partial condenser system,... 

Figure 8 illustrates the performance of a system with three equilibrium stages in the absorber and six in the stripper. The actual steam requirement is 147 moles/mole SO2 (41.3 kg/kg). The use of a finite number of stages increases the steam requirement a factor of 2.5 from the case of infinite stages with a nonlinear equilibrium. 

Figure 8. Actual steam requirements, simple absorption/stripping with live steam, 3000 ppm SOi in at 55°C, 90% removal, 1.0M citrate, 2.0M Na...

Actual steam requirement with typical stack gas should be about 41 kg/kg S02 ... 

Following the absorption of ethylene oxide by water from a process stream, a 600-Ibmol/h water stream (prior to discharge) is steam-stripped of the ethylene oxide as part of the regeneration step. For a feed ethylene oxide concentration of 0.5 mol %, determine the actual amount of steam required for stripping ethylene oxide to a concentration of 0.03 mol %. 

Steam rate The mass flow rate of steam required to produce a unit of output, in pounds per kilowatthour (kilograms per kilowatthour) or pounds per horsepower hour. The theoretical steam rate (TSR) assumes a perfect expansion process between two conditions. An actual steam rate is based on the actual expansion, including the inefficiency of the turbine and generator. 

This section details the piping layout of circular and box-type furnaces. Although such special features as snuffing steam are actually required for both heaters, they are explained for one application only. 

The result of the calculation will be a feed to or a product discharge from the last effect that may not agree with actual requirements. The calciilation must then be repeated with a new assumption of steam flow to the first effect. 

The confusion matrix (NSAC-60) is a method that identifies potential operator errors lemming from incorrect diagnosis of an event. It can be used to identify the potential for an operator to conclude that a small LOCA has occurred, when it is actually a steam line break. This provides a method for identifying a wrong operator response to an off-normal plant condition. It is particularly useful in Step 5 of the. SHARP procedures, Documentation requirements are presented in Table 4.5-2. 

The process designer or mechanical engineer in a process plant is not expected to, nor should he, actually design a mechanical vacuum pump or steam jet, biit rather he should be knowledgeable enough to establish the process requirements for capacity, pressure drops, etc., and understand the operation and details of equipment available. 

In the previous discussion it has been assumed that the vapour is a pure material, such as steam or organic vapour. If it contains a proportion of non-condensable gas and is cooled below its dew point, a layer of condensate is formed on the surface with a mixture of non-condensable gas and vapour above it. The heat flow from the vapour to the surface then takes place in two ways. Firstly, sensible heat is passed to the surface because of the temperature difference. Secondly, since the concentration of vapour in the main stream is greater than that in the gas film at the condensate surface, vapour molecules diffuse to the surface and condense there, giving up their latent heat. The actual rate of condensation is then determined by the combination of these two effects, and its calculation requires a knowledge of mass transfer by diffusion, as discussed in Chapter 10. 

The volatility of ammonia at 80 and 120°C is about 5% higher than is now predicted by the SWEQ model. This means that the SWEQ model will predict slightly more steam for a given separation, all other effects being equal, than will actually be required. 

---