Section Waste-Heat Steam Generation

Convective Section Waste-Heat Steam Generation 

It is probably best to consume steam generated in small waste-heat boilers, locally, in steam reboilers and preheaters. Turbine drivers are 

Betz Handbook of Industrial Water Conditioning, 8th ed., copyright 1980, Betz Laboratories, Inc., Trevose, PA 19047 (USA). 

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Convective Section Waste-Heat Steam Generation... 

Process Steam Generation. Steam generated in the process sections of the plant may be at the highest plant pressure level or an intermediate level. Also, the process area may have fired boilers, waste heat boilers, or both. There may be crossties between utility and process generated steam levels. Enough controls must be provided to balance far-ranging steam systems and protect the most critical units in the event of boiler feedwater shortage situations. 

Cast iron sectional boilers Steel boilers Electrode boilers Steam generators Vertical shell boilers Horizontal shell boilers Watertube boilers Waste heat boilers Fluid bed boilers... 

Process waste-heat boilers then cool the reformed gas to about 371°C while generating high-pressure steam. The cooled gas-stream mixture enters a two-stage shift converter. The purpose of shift conversion is to convert CO to C02 and produce an equivalent amount of H2 by the reaction CO+H20 C02 + H2. Since the reaction rate in the shift converter is favored by high temperatures, but equilibrium is favored by low temperatures, two conversion stages, each with a different catalyst provide the optimum conditions for maximum CO shift. Gas from the shift converter is rhe raw synthesis gas, which, after purification, becomes the feed to the NH3 synthesis section. 

Fig. 4.2. Waste heat boiler for a copper smelting flash furnace (Peippo et al, 1999). Note, left to right (i) flash furnace gas offtake (ii) boiler radiation section with water tubes in walls (iii) suspended water tube baffles in radiation section to evenly distribute gas flow (iv) convection section with hanging water tubes. Steam from the boiler is used to generate electricity, to power the acid plant s main blower and for general heating and drying.

Shell-side effluent from the reforming exchanger is cooled in a waste-heat boiler, where HP steam is generated, and then flows to the CO shift converters containing two catalyst types one (4) is a high-temperature catalyst and the other (5) is a low-temperature catalyst. Shift reactor effluent is cooled, condensed water separated (6) and then routed to the gas purification section. C02 is removed from synthesis gas using a wet-C02 scrubbing system such as hot potassium carbonate or MDEA (methyl diethanolamine) (7). 

When possibilities to export steam or power are limited, part of the secondary reformer waste heat is used, in addition to steam generation, for steam superheating, a feature in common with other modern concepts. Proprietary items in addition to the horizontal converter are the traditional Kellogg reformer, transfer line and secondary reformer arrangement, waste-heat boiler, and unitized chiller in the refrigeration section. 

For the operation of the process, the reactants are filtered from suspended scale, etc., mixed, and fed to the converter operating at about 1000°C. In order to prevent decomposition of the HCN, the gases flowing from the converter are cooled in a waste-heat boiler connected directly to the catalyst screen chamber. The steam generated is used in the recoveiy section. The... 

High-pressure steam is generated from three on-purpose boilers, together with the waste heat boiler (H-9001) in the hydrogen plant and the convection section of a... 

Reformer In a reformer furnace, shown in Exhibit 7-5, preheated process fluid flows through catalyst-filled tubes, which are usually located in the center of the radiant section. This type of furnace may have single or multiple compartments burners may be mounted in the roof, wall, or floor. Heat recovery systems may also be employed through the use of waste heat boilers or the convection section s steam generation coils. 

Figure 21.6 Convective section steam generation from waste heat.

The hot gases from this section of the process are passed through waste heat boilers to generate the large amount of steam necessary to supply the process and drive the compressors downstream in the plant. 

Solid fuels refer to any fuels, such as coals, wastes, biomass, etc., that are in a solid state when they are burned in a high-temperature furnace. Coals are the most abundant fossil fuel on Earth, and are the most commonly used solid fuels for power generation, in the metallurgical industry, for gasification, and for heat supply. The wastes sometimes are burned in incinerators, as discussed in Chapter 8, and the generated heat is recovered to produce steam and electricity. Biomass mainly refers to plant materials, which are rarely used as fuels in industry. In this section, we will... 

European Vinyls Corporation (formerly Stauffer) offers an innovation called the byproduct recycle process. It is a small catalytic reactor that can be used to oxidize chlorinated hydrocarbons and other hydrocarbon wastes with high purity oxygen. The products are CO2, HCl, and water. Steam is generated with the exothermic heat of reaction and the HCl is recycled to the oxychlorination section [21],... 

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