Waste heat recovery boilers

Dual pressure For comparison, a combined cycle scheme with dual pressure is shown in Figure 15.13. In this case, the waste heat recovery boiler also incorporates a low-pressure steam generator, with evaporator and superheater. The LP steam is fed to the turbine at an intermediate stage. As the LP steam boils at a lower temperature than the HP steam, there exists two pinch points between the exhaust gas and the saturated steam temperatures. The addition of the LP circuit gives much higher combined cycle efficiencies with typically 15 per cent more steam turbine output than the single pressure for the same gas turbine. 

The Oregon installation uses a 25 tire per hour unit manufactured by Nippo in Japan and marketed in the U.S. by Tsurusaki Sealand. The unit has been in operation since 1987 with moderate success, but no U.S. company has yet decided to purchase another one. The draft configuration in the unit allows it to bum at 2,000 degrees Fahrenheit and produce 100 psig process steam. The unit has a Cleaver Brooks waste heat recovery boiler and a bag filter. Whole tires are automatically fed into the unit-both automobile tires and light truck tires. The State of Oregon Department of Environmental Quality has approved the operation of the unit. 

R.G.I. Leferink and W.M.M. Huijbregts, Nitrate Stress Corrosion Cracking in Waste-Heat Recovery Boilers, Anti-Corrosion Methods and Materials, 49(2), 118-126 (2002). 

Fig. 12-22 Use of heat pipes to dnVe waste heat recovery boiler. (Courtesy Dr, M.A. Ruch. Q-Dot Corporation, Dallas. Texas.) ...

Heat pipes are particularly useful in energy-conservation equipment. One example is shown in Fig. 12-22 where hot exhaust gases are used to drive a waste heat recovery boiler. The hot gases from a combustion process, which... 

The diverter valve operation is controlled by the waste heat recovery boiler (WHRB) and directs the exhaust gas to the WHRB boiler or out of the bypass stack to maintain the required steam pressure. The ABCO WHRB is rated at 30,000 Ib/hr and has two firing modes. In the turbine-firing mode, a 5.8MMBtu duct burner is available to supplement the turbine exhaust stream. In the direct-fire mode, used when the turbine is offline, the direct fresh-air Are at 41.5MMBtu is available. 

It is almost always necessary to make an economic calculation to justify a waste heat recovery boiler. One of the most common refinery applications is the recovery of available heat in a catalytic cracking unit regenerator flue gas to generate steam. The flue gas is rich in CO which not only is hot, but also bums well in a boiler. 

When waste heat recovery boilers are used with process heating furnaces, they fail to get prime attention from their owners and operators. It may be that the plant managers have no training in boiler operation or hazards, and they try to operate the waste heat boiler with no licensed fireman or engineers. That can lead to a catastrophic steam explosion. 

The SOa-containing gas leaving the furnace is cooled in a WHRB (waste heat recovery boiler), cleaned, and then admitted to the converter of the sulfuric acid plant. 

Earlier designs of sulfuric acid plants preferred minimizing initial capital cost and hence heat recovery equipment was not common. For example, these designs had atmospheric cooling ducts, air cooled heat exchangers, or air injection facilities instead of waste heat recovery boilers and economisers. 

These are used to convey the SO2- and SOs-bearing—generally hot—gases from the waste heat recovery boiler to the converter system (including connections to the hot... 

Waste Heat Recovery Boilers, Economisers,and Boiler Feed Water Pump... 

Waste heat recovery system design (provision of waste heat recovery boilers and economisers). 

Residue or ash removal and handling systems Waste heat recovery boiler systems Emissions control systems Breeching, stacks and dampers Controls and instrumentation... 

SOs vapours for subsequent production of 65 % oleum or liquid SO3 with some more equipments. Expansion of production capacity can be planned in the beginning by installing sufficiently big sulphur burning furnace, waste heat recovery boiler, converter, air blower, etc. These can be used as such in future. 

Start circulation of alkali solution in scrubbers. Sulphur feeding to be started only when converter passes have been heated up to their ignition temperatures by suitable means (oil firing or other means). Start with low air and sulphur feed rates only. Bypass the waste heat recovery boilers partially in the first few hours tiU all the system temperatures have been normalised. Gradually increase the air flow and sulphur feeding to increase the production rate. Operate the oleum and SO3 systems to produce them as per demanded by customers/as advised by marketing department. 

Boilers are operated in many industries for generating steam required for process heating of reactors, evaporators, and distillation columns which may need steam at a pressure of 4-6 kg/cm only. However, the boilers are generally operated at 10-15 kg/cm or even higher pressures. Steam is also available from waste heat recovery boilers in many chemical industries at such pressures. 

Captive power generators may be therefore installed in many chemical plants which are to be run by steam turbines. These can get the steam supply from coal-fired boilers or from waste heat recovery boilers operating on hot process gases. They can reduce dependence on supply of power from external grid. They... 

Cogeneration of Power Through Waste Heat Recovery Boilers and Economisers... 

Hot gas streams at 900-1000 °C are generated in sulphuric acid plants by bmning sulphur. These gases are cooled by waste heat recovery boiler before further processing. High-pressure steam at pressures of 45 kg/cm and temperatures of 410 °C is generated as a by-product which is supplied to a condensing turbine to produce power (which can be more than what is required to mn the plant). This surplus can be exported to other industries. 

Waste Heat Recovery Boiler is bypassed occasionally to maintain temperature In downstream units... 

It can be generated by coal-fired boilers/or will be available from waste heat recovery boilers (WHRBs) which are heated by hot process gases, hot exit gases from the plant. 

Sulphur is melted in melters by steam coils. It is then pumped to the relractory-lined furnace to produce SO2 by burning. Air blower suppfies diy air to the furnace through the drying tower. The hot gases from exit of furnace are cooled in a waste heat recovery boiler 1 and then passed through a multistage converter having... 

Waste heat recovery boilers Maintaining gas temperatures at converter passes and for steam generation Less conversion of SO2 to SO3 and less steam generation Critical units... 

Waste heat recovery boiler (WHRB) Heat generated during oxidation of ammonia is recovered to generate steam If water flow gets intermpted the boiler will be in danger Water-level controller is a must stop gas feed if water level is too low... 

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