Pressure live steam

Kehlhofer explains that the pre-heating loop must be designed so that the heat extracted is. sufficient to raise the temperature of the feed water flow from condenser temperature T to Ta (see Fig. 7.6). The available heat increases with live steam pressure Ipf), for selected 7 b(= Ta) and given gas turbine conditions, but the heat required to preheat the feed water is set by (Ta — T. ). The live steam pressure is thus determined from the heat balance in the pre-heater if the heating of the feed water by bled steam is to be avoided but the optimum (low) live steam pressure may not be achievable because of the requirement. set by this heat balance. 

Using Figure 14.12b in Volume 2, with a pressure of entrained vapour of 101.3 kN/m2, a live-steam pressure of 1135 kN/m2 and a discharge pressure of 170 kN/m2, then 1.5 kg live steam is required/kg of entrained vapour. 

These values represent only one solution to the problem and variation of the calandria and live-steam pressures may result in even lower requirements of high-pressure steam. 

Apart from increasing the efficiency of the ejector, the economy of the system might be improved by operating with a higher live-steam pressure, increasing the pressure in the vapour space, and by using the vapour not returned to the ejector to preheat the feed solution. 

Live steam pressure before high-pressure stage valves, MPa 6.03... 

Then, the newly installed coal fired plants had a typical live steam pressure of 24.1 MPa, though steam temperatures improved gradually. The most advanced steam condition currently in commercial operation is 24.1 MPa/566°C/593°C, which was applied to Nanao-Ohta No. 1 boiler of Hokuriku Electric Power Company supplied by BHK in 1995. This trend continues with Matsuura No. 2 Unit, the steam parameters of which were 24.1 MPa/593°C/593°C in 1997. 

Humidification. For wiater operation, or for special process requirements, humidification maybe required (see Simultaneous HEAT and mass transfer). Humidification can be effected by an air washer which employs direct water sprays (see Evaporation). Regulation is maintained by cycling the water sprays or by temperature control of the air or water. Where a large humidification capacity is required, an ejector which direcdy mixes air and water in a no22le may be employed. Steam may be used to power the no22le. Live low pressure steam can also be released directly into the air stream. Capillary-type humidifiers employ wetted porous media to provide extended air and water contact. Pan-type humidifiers are employed where the required capacity is small. A water filled pan is located on one side of the air duct. The water is heated electrically or by steam. The use of steam, however, necessitates additional boiler feed water treatment and may add odors to the air stream. Direct use of steam for humidification also requires careful attention to indoor air quahty. 

With a steam turbine, the turboeompressors ean be readily matehed to the different plant operating eonditions. Under eontinuous load, this type of installation is powered by the steam resulting from ammonia eombustion. Consequently, an outside steam supply is needed for startup. This may be a separate boiler or another external souree with live-steam properties not neeessarily eorresponding to those obtained from the nitrie aeid plant. The steam turbine must be of robust design beeause of the different pressure and temperature levels. 

The condensing turbine has several advantages and disadvantages over the back pressure turbine. The advantages are that it requires less change in the live steam for various turbine loads and is therefore easier to control. It also requires less steam because the enthalpy drop is larger. Finally, only one steam level is affected for a change in power requirements. 

Where high temperatures are required (e.g. for process work) and lower temperatures for space heating, it is desirable to use flash steam recovery from the high-temperature condensate to feed into the low-temperature system, augmented as required by reduced pressure live steam. 

Within any particular facility, steam is expected to be delivered to various points of use safely and at controlled temperatures and pressures through relatively long-lasting distribution networks. Where the steam is not excessively contaminated or directly consumed in a process as live steam, it should be condensed, collected, and returned to the boiler for reuse. Thus, the post-boiler section of a boiler plant essentially relates to the systems concerned with steam distribution and condensate return (CR). 

For smaller and lower pressure plants, sampling steam and condensate to obtain reliable information may be a problem. Careful inspection may reveal a point in a line where a live steam sample can be directly obtained. But this point may prove to be of little value unless there is a means of connecting a temporary sample cooler (such as a stainless steel coil in a bucket of cold water). 

In steam distillation, steam is introduced into the column to lower the partial pressure of the volatile components. It is used for the distillation of heat sensitive products and for compounds with a high boiling point. It is an alternative to vacuum distillation. The products must be immiscible with water. Some steam will normally be allowed to condense to provide the heat required for the distillation. Live steam can be injected... 

Crude oil distillation is carried out in a complex column sequence in which live steam is injected into the separation to provide the heat required and to reduce the partial pressure of the components to be distilled. The... 

Since the pressure of entrained vapour = 101.3 kN/m2 and the discharge pressure =135 kN/m2, the required flow of live steam = 0.5 kg/kg entrained vapour. 

The defuzed projs are placed vertically with open ends downward inside a long rectangular tank provided with a perforated false bottom. The ogival part of each proj should rest in one of the holes of false bottom. Then the tank is partly filled with water and live, low pressure steam is injected thru a perforated pipe located below the projs. This causes the water to boil and the heat melts the expl, thus emptying the projs. The molten material is accumulated at the bottom of the tank and then drained. The expl thus collected Is usually suitable for industrial uses... 

Some difficultly volatilized substances (such as those with boiling points above 100°) can be distilled under reduced pressure (or in vacuum), as is mentioned above. In some cases, however, the temperature of vaporization may be lowered if " live steam is introduced thru a pipe near the bottom of the still. As a result of this opera-... 

Separation of the oxide and the organic byproducts is accomplished by distillation in two towers. Feed from the saponifier contains oxide, aldehyde, dichloride, and water. In the first tower, oxide and aldehyde go overhead together with only small amounts of the other substances the dichloride and water go to the bottom and also contain small amounts of contaminants. Two phases will form in the lower section of this tower this is taken off as a partial side stream and separated into a dichloride phase which is sent to storage and a water phase which is sent to the saponifier as recycle near the top of that vessel. The bottoms are a waste product. Tower pressure is 20 psig. Live steam provides heat at the bottom of this column. 

The distillation of tetraethyllead from the reactive mixture is conducted by sending live steam through it. In the beginning of the distillation the steam pressure is 0.02-0.04 MPa then it increases and can be brought to 0.1-0.2 MPa. The temperature of the steam should not exceed 130 °C. The distilled vapours of tetraethyllead and water enter cooler 6, where they condense, and flow into separator 7. There, due to the difference in the densities, the aqueous condensate is separated from tetraethyllead and flows into trap 13, from where it is sent to biochemical purification. The distilled tetraethyllead is sucked into batch box 8 and sent to water flushing and air treatment. 

A batch of 35-wt-% NaOH solution in water at atmospheric pressure and 100(°F) is in an insulated tank by injedion of live steam drawn through a valve from a line containing l steam at 30(p ia). The process is stopped when the NaOH solution reaches a conceit 32.5 wt %. At what temperature does this occur ... 

As mentioned above, this process now serves mainly as an adjunct to enzymatic conversion of starch and is rarely used alone. A starch slurry containing 35-45 percent solids is acidified with hydrochloric acid to about pH 1.8-1.9. The suspension is pumped into an autoclave (converter) where live steam is gradually admitted to a pressure of 30-45 psi. The conversion time largely determines the DE of the hydrolyzate for example, eight min... 

---