Steam superheaters

Superheating of steam can increase the power output of the turhine and minimises the condensation of steam on the blades. The superheater can be used to recover heat from hot gases. Considerations for the selection of the superheater. 

Pressure drop through the superheater shall be minimum on steam side as well as gas side. 

Provision of valves for steam inlet and outlet, safety, fitting of pressure gauges, vents, drain points for any condensate formed on gas side. 

Possibility of increasing the heat transfer area by addition of a few more mbes in future. 

Hot Process Gas (if available in plant) Composition and flow rate, temperature of gases at inlet and outlet, presence of any corrosive component in the gas mixture and the dew point (the temperature at which the corrosive component might condense and reduce the life of the superheater tubes if the gases get cooled to this temperature) or requirement of auxiliary fuel for superheating. Provision of C.I. gills on the tubes for protection against corrosion. 

Exclusions from scope of supply by vendor must be very clearly understood. 

Another option for consideration is reheat turbines HP steam turbine can exhaust medium pressure saturated steam, which can be reheated by hot process gases if available and more power can be generated. 

Pressure and temperature of the steam available/being generated. 

Maximum pressure drop allowed on steam side. 

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Is steam superheat maintained at the maximum level permitted by mechanical design ... 

Fig. 4. Manufacture of styrene by adiabatic dehydrogenation of ethylbenzene A, steam superheater B, reactor section C, feed—effluent exchanger D,...

SO2 gas is catalyticaHy oxidized to SO in a fixed bed reactor (converter) which operates adiabaticaHy in each catalyst pass. The heat of reaction raises the process gas temperature in the first pass to approximately 600°C (see Table 7). The temperature of hot gas exiting the first pass is then lowered to the desired second pass inlet temperature (430—450°C) by removing the heat of reaction in a steam superheater or second boiler. 

Wilhelm Schmidt Steam superheater for locomotives. and ALCO largest ever built (540 long tons). 

Steam superheaters dramatically improve the performance of railway engines. 

K,h = steam superheat correction factor from Table 7-7 Kn = Napier steam correction factor for set pressures between 1500 and 2900 psig from Table 7-6 K = Kj = coefficient of discharge ... 

Boiler Steam flow rate, design pressure, steam superheat... 

The flue gas tunnels are rectangular fire-brick structures at the reformer s bottom. They act as horizontal ducts for flue gas removal. The flue gas exits at 1,800°F to 1,900°F. A heat recovery unit is provided to recover heat from this gas. This unit contains a reformer feed preheat coil, steam superheat coil, steam generation coil and boiler feed water preheat coil. 

A combined cycle made of two cycles is shown in Fig. 5.2. The upstream topping cycle is a steam Rankine cycle and the downstream bottom cycle is an ammonia Rankine cycle. The following information is provided steam boiler pressure = 2 MPa, steam superheater temperature = 400° C, steam condenser (heat exchanger) pressure = 20 kPa, ammonia boiler (heat exchanger) pressure = 1200 kPa, ammonia condenser pressure = 800 kPa, and mass flow rate of steam = Ikg/sec. 

A Rankine/Rankine cycle (Fig. 5.16) uses steam as the working fluid with 1 kg/sec mass flow rate through the top Rankine cycle, and Freonl2 as the working fluid in the bottom Rankine cycle. The steam condenser (FIXl) pressure is 20 kPa, the boiler pressure is 3 MPa, and the steam superheater temperature is 400°C. The steam mass flow rate is 1 kg/sec. 

Steam superheater and an air heater installed on the pulse combustor flue gas (D13938S, p. 9-2)... 

The higher the motive-steam superheat temperature, the drier the exhaust steam. 

Steam superheater Cool reaction gases and superheat steam. 

Steam Superheater This unit superheats saturated steam from 250°C (and 4000kPa) to 380°C. The product steam is of medium pressure and suitable quality for in-house application and also for export. The superheater cools the reaction gases from the reactor exit temperature of 645°C to 595°C. Design pressure on the shell side is approximately 5000 kPa. The steam superheater is constructed from mild steel. 

The steam superheater is a clamp ring-type, floating-head, shell and tube, heat exchanger. It is able to produce up to 5775 kg/h of steam at 380°C and 4000 kPa. 

Absorption column Steam superheater Bleaching column delivery tank Nitric acid storage tank... 

CHAPTER 10 Case Study — Steam Superheater Design... 

The steam specification stipulates the need for superheated steam at 380°C and 4000 kPa. This medium-pressure product is of sufficient quality for the plant steam-turbine and ammonia superheater, with the remaining portion to be sold to another plant. A heat balance over the entire steam-production circuit concludes that this steam product may be produced at the rate of 5775 kg/h. This result determines the required heat duty for the steam superheater as 585 kW. 

Details of the calculations associated with the steam superheater design are presented in Appendix H. 

It is the second of these two areas that is of interest in this chapter. Heat is delivered for steam production in many separate stages. Preheat is first supplied to the low-pressure deionized water prior to deaeration. Higher pressure product (HP boiler feedwater) is further preheated to around 100°C for supply to the waste-heat boiler. The waste-heat boiler is then able to vapourize the high-pressure deionized and deaerated water for final delivery to the steam superheater. 

This chapter contains the specification for the steam superheater to achieve the required design. Aspects to be considered include the heat-transfer requirements from the unit, and the mechanical and construction aspects of the design. It is noted that the unit must conform to the appropriate design codes (Australian or equivalent). 

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