Condensate dumping

In small boiler systems, the use of CR system strainers and high-temperature-resistant bag filters are highly recommended to prevent this corrosion debris from entering the FW system. In larger plants, condensate polishers or electromagnetic separators may be employed. Condensate dumping may even take place, although this is a wasteful and expensive process because both water and heat are lost. 

The gas, condensate, and free water are then discharged from the ncs scl through backpressure and liquid dump valves. The gas leaving the separator is saturated with water vapor at the temperature and pressure of the top of the low temperature separator. If this temperature is low enough, the gas may be sufficiently dehydrated to meet sales specifications. Dehydration is discussed in greater detail in Chapter 8. 

When steam pressures in the chest are near atmospheric, condensate can rise in the shell and drastically reduce avail-ahle surface—if the trap is too small to dump steam into the condensate return system or if the condensate return pressure is greater than the calculated chest pressure required. In these cases, the steam pressure will have to rise in the chest to overcome this error, if steam pressure is available. If not, the rehoiler will not deliver design flux. 

This process steam flow will dictate output generated by the turbo-alternator and excess or deficiency is made up by export or import to the supply utility, as appropriate. The alternative to the system in Figure 15.15 is to use a back-pressure turbine with bypass reducing valve and dump condenser, as shown in Figure 15.16. 

On this system, the turbine is speed controlled and passes steam, depending on the electrical demand. The bypass-reducing valve with integral desuperheater makes up any deficiency in the steam requirements and creates an exhaust steam pressure control. Alternatively, any surplus steam can be bypassed to a dump condenser, either water or air cooled, and returned to the boiler as clear condensate. 

Figure 15.16 A back-pressure turbine with PRDs valve and dump condenser...

As with the electrical load profile, it is also necessary to analyze the heat load over the daily and annual cycles. Ideally, the heat load will match the available heat from the electrical generator (however, this is rarely the case). There will be periods when supplementary output will be necessary which can be achieved by, say, supplementary firing the waste heat gases of a gas turbine, or heat output reduction is necessary by the introduction of bypass stacks. For a steam turbine installation bypass pressure-reducing valves will be necessary to supplement steam output, while a dump condenser may be needed at low-process steam demands. The nature of the electrical and heat load will obviously have significant influence in the development of the scheme and scope of equipment. 

The electrical and heat analysis, as discussed in Section 15.3, will show the relationship between power and heat and how this varies over time. It may be necessary to use steam bypass and stations or dump condenser, as discussed in Section 15.2. The uses of dump condensers for meeting part-load requirement is inefficient and should be avoided. It is more acceptable to reduce turbine power output accordingly and import or top-up from an alternative supply. 

Where condensate is severely contaminated due to excessive iron content, high pH levels, or alkalinity, carryover, or process intermediaries, it is common practice to consider dumping the condensate. This obviously is not a particularly sensitive course of action in an era of high-profile environmental issues and is additionally expensive because of disposal costs and the loss of valuable heat content. 

Today, there is almost always a relatively low-cost, low-tech solution available as a viable alternative to dumping condensate. Most CR recovery or polishing solutions employ a fixed installation, but mobile retrofits increasingly are being provided by outsourced service providers. See Figure 9.4d for a schematic layout of a mobile boiler condensate conditioning plant. 

Where the rapid removal of corrosion debris occurs or where amine feed rates are initially kept low and the condensate still contains iron oxide, the dirty condensate should be polished or simply dumped until the condition improves. 

In systems where the steam and condensate systems are extensive, it is important that any contamination of returned condensate be controlled either by monitoring and dumping or by condensate polishing. 

Level, e.g. Overfilling Leakage from a dump valve Flooding of condensers (heat exchangers) ... 

The vapor flowing between trays was at its dew point. A sudden increase in tower pressure caused a rapid condensation of this vapor and a loss in vapor velocity through the tray deck holes. The resulting loss in vapor flow caused the tray decks to dump. 

Overhead from the first fractionator is condensed and charged to the second tower. There substantially pure propylene oxide is taken overhead. The bottoms is dumped. Tower pressure is 15 psig, and the overhead bubblepoint is 100°F. Reactions are... 

In nuclear propulsion, any thermodynamic device, such as a radiator or condenser, that is designed to absorb the excess heat energy of the working fluid. Also called heat dump. 

A correlation can be made between the measured magnitude of the waveguide signals and the vapor pressures of the condensed vapors sensed. Three of the five polymer films tested showed extremely large responses to the simulant dimethyl methyl phosphonate (DUMP), and one of these films could detect DUMP vapor concentrations below the 20 ppm level. 

Macromolecules such as exopolysaccharides and humic condensates affect the distribution of microorganisms and nutrients within the water column by adding microstructure. Many planktonic bacteria and algae secrete polysaccharides. In some circumstances, exopolysaccharide production is a substantial portion of gross production. The adaptive significance of this activity is unclear. Possibilities include the dumping of excess photosynthate,... 

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