Boiler types waste-heat boilers

If the CO is not completely combusted to CO2 in the regenerator, a CO boiler is used to complete the combustion. The resulting heat of combustion and the sensible heat of the flue gas along with any heat from auxiUary fired fuel are recovered in the form of high pressure steam. When the regenerator is operated in total CO bum, the CO boiler is replaced with either a shell and tube exchanger or a box-type waste heat boiler (see Heat... 

The process gases enter a forced-circulation-type waste heat boiler at 800-1000 °C. Several changes have been made to the mechanical rapping equipment and cooling pipe bundles of the boiler to improve the performance and maintenance access. The gases exit the waste heat boilers at a temperature of 300-350 °C and pass through the hot cyclone separators and electrostatic precipitators into the mercury removal towers. Two electrostatic precipitators are installed simultaneously in both lines to ensure continuous processing. 

One manufacturer uses single-drum, watertube type waste heat boilers on incineration systems. Watertube bodets are also used by other manufacturers in installations where high steam pressures and flow rates are required. Another manufacturer offers heat recovery systems with water wall or radiant sections in the primary chamber. These water wall sections, which are usually installed in series with a convective type waste heat boiler, can increase overall heat recovery efficiencies by as much as 10 to 15%. 

Some beehive ovens, having various improvements and additions of waste heat boilers, thereby allowing heat recovery from the combustion products, may stiU be in operation. Generally, however, the beehive oven has been replaced by waH-heated, horizontal chamber, ie, slot, ovens in which higher temperatures can be achieved as well as a better control over the quality of the coke. Modem slot-type coke ovens are approximately 15 m long, approximately 6 m high, and the width is chosen to suit the carbonization behavior of the coal to be processed. For example, the most common widths are ca 0.5 m, but some ovens may be as narrow as 0.3 m, or as wide as 0.6 m. 

The latest installations incorporate a waste heat boiler in the off-gas cleaning system to recover sensible heat from the rotary kiln off-gas. There is sufficient sensible heat in the off-gas from the SL/RN process to generate 500 to 700 kWh/t of DRJ, depending on the type of reductant used. 

Waste-heat Boiler A shell and tube-type exchanger required to heat pressurized (4000 kPa) hot water from 117°C to a saturated vapour at 250°C. Design pressure on the tube side is approximately 5000 kPa. The waste-heat boiler cools reaction gases from 595°C to 280°C. It is made from mild steel. 

Application -Waste-heat boiler Heat-exchange area = 110 m2 Base cost = USS17 600 Design-type factor = 0.64 Design pressure factor =1.5 Materials factor = 1. 0... 

In the normal straight-through process, see Figure 1, the complete H2S stream is fed to a burner together with the amount of air required to bum one third of the H2S to SO2 to obtain the required gas mixture for the catalytic step of the process [2,5], The reaction temperature in this thermal step is about 1000-1400°C, and in this step 60 to 70% of the H2S in the gas is directly converted to elemental sulphur. The sulphur is condensed by cooling the gases first in a waste heat boiler, and after that in a sulphur condenser. After elemental sulphur removal the gas mixture is reheated to 250-300°C and fed to a catalytic converter. Three types of catalyst are currently used [5] ... 

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). 

Reforming-exchanger effluent is cooled in a waste-heat boiler, where high-pressure steam is generated, and delivered to the CO shift converters containing two catalyst types One (4) is a high-temper-ature catalyst and the other (5) is a low-temperature catalyst. 

The combustor off-gas corresponds to the throughput to the gas cooler (e.g., waste heat boiler) of a commercial plant. The gas analysis is given in Table VII, The values for the conventional stoker type incinerator are those in the case of large cities in Japan. They are average values with the exception of HC1, which is slightly higher. The amounts of particulate, SOx and HC1 contained in the off-gas of the Dry Process PUROX System are much less than those of the stoker incinerator. The reason is considered to be that the Cl", SO , etc. combine with alkali metals and shift into the slag in the converter. 

As usual in the conventional copper or lead smelter, none of the El Paso smelter gas streams has a sulfur dioxide concentration as high as 12%. In the pilot plant, then, the 12% sulfur dioxide gas stream is generated by burning molten sulfur in a spray-type sulfur burner to produce a gas stream containing 18% sulfur dioxide. This hot gas stream, at 1350°C (1623 K), is cooled to about 360°C (633 K) in a waste heat boiler. When the pilot plant is operating with this 18% gas, process tail gases are recycled to dilute the 18% head gas stream to 12%. In an alternate mode of operation, liquid sulfur dioxide is vaporized to generate the pure gas. 

Bayer operates a number of. similarly engineered waste combustion units. At the Dormagen plant, a further combustor for solid and liquid wastes has been placed in service. It consists of a rotary furnace, afterburner, waste-heat boiler, and gas scrubber. The plant incorporates a condensation-type electrostatic filter specially developed by Bayer [259] and an SCR unit for selective catalytic reduction of nitrogen oxides (with ammonia) and for degradation of dioxins in the tail gas (see Fig. 115). 

The afterburning reactions of zinc are more exothermic and a waste heat boiler type of offtake and roof system is recommended. This type of system is in successful use at Korea Zinc on zinc fuming plants. 

Figure 3 shows the outline of the process employed at the lijima Zinc Refinery. Two Dorco-type roasters with a set of waste heat boilers and cyclones are operating. The waste gases fix>m the boilers go through a hot fan to a Peabody scrubber to cool and wash the gases. The eooled gases fipm the two roasters are mixed and de-misted in two stages of mist precipitators. 

Modem converter systems have cesium promoted ring type vanadium pentoxide as catalyst in the first and the last (fourth/fifth) passes and conventional vanadium pentoxide catalyst (also ring type) in the other two/three passes. A second waste heat boiler is provided to recover additional heat after the first pass of catalyst. A steam superheater can be provided in the waste heat recovery system, if required by the client in order to export the steam to nearby industry or to generate superheated steam for captive use. 

Process plants are for the most part dependent on electric power for motive purposes, to drive the process equipment and the materials transport systems. Other types of driver, in particular the steam turbine, have sometimes been employed, especially for major drives such as turbo-compressors (with which a turbine driver has a natural compatibility in terms of speed and speed variation), and in plants where steam is generated for process consumption or as a by-product in waste-heat boilers. Gas engine drivers (for reciprocating compressors) and gas turbines (for turbo-compressors) are also often employed for... 

The first reactor is the sulphur combustion furnace, and a common type is shown in Figure 7.6. Liquid sulphur is dispersed as a fine spray in order to ensure good contact with the air and hence efficient combustion. The furnace consists of a cylindrical steel shell lined with several layers of insulating and refractory bricks. The burner is at one end and the hot products of combustion at about 1000°C are passed directly into a waste heat boiler which produces high-pressure steam from the excess heat. The combustion gases, which contain 10-10.5 per cent by volume sulphur dioxide, are simultaneously cooled to around 425 C, the required temperature for the SO2 converter. 

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. 

The by-product stream can be divided into two types, according to their sites, the built-in form inside the catalyst bed and built-out form outside the catalyst bed. The built-in form is not to be used now because of its complicated structures and the low volumetric coefficient of the converter. The built-out form of by-product steam can be subdivided into three sorts Front-type, mid-type and back-type according to their sites in which the heat is recovered (shown in Fig. 9.23). In front-type boiler process, the reaction gas from the catalyst bed enters into waste heat boiler to recover the reaction heat, and then enters into the interchanger. It would produce high-pressure steam at 4 MPa-12.5 MPa. The mid-type waste heat boiler is located between the first and the second interchanger, the temperature of reaction gas is lower than that in front-type boiler, and can only produce steam at 0.9-1.6 MPa. The back-type boiler is applicable to outlet gas at low-temperatm-e of the converter. 

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