Regeneration furnaces multiple hearth

PAG sludge can be regenerated by wet air oxidation (WAO) or by a multiple-hearth furnace. Capacity losses might be high in WAO, particulady with low molecular weight organics. Weight loss in a furnace may exceed 20%. 

Figure 16 Process flowsheet of a GAC system with regeneration. In this complete GAC adsorption and regeneration system, four GAC columns can be operated in parallel or in series. Spent carbon is transferred to a multiple-hearth furnace for thermal regeneration. Regenerated carbon is mixed with virgin makeup and pumped back to the GAC columns. The GAC columns are backwashed periodically. (From Ref. 27.)...

Figure 11 shows a typical flow diagram for a thermal regeneration system [11]. Thermal regeneration is conventionally carried out in a multiple hearth furnace or a rotary kiln at... 

The capacity of regeneration furnaces is selected so that they operate 80-90% of the time. In multiple-hearth furnaces the loading is 70-80 lb/(sqft)(day). In countercurrent direct fired rotary kilns, a 6% volumetric loading is used with 45 min at activation temperature. 

DuPont evaluated the PACT process for several months in a 75 gpm pilot facility and installed a 30 MGD PACT system to treat industrial wastewaters at its Deepwater, NJ, USA, plant. The carbon was regenerated in a multiple hearth furnace. Zimpro, Inc. has also evaluated the PACT process at the Rothschild, WI, USA, sewage treatment plant, using wet air oxidation to regenerate the carbon. 

Due to its high temperature, thermal regeneration is usually not conducted in situ but requires shipment of the spent activated carbon to special regeneration units such as multiple hearth furnaces or rotary kilns. The design of the reactivation system is dependent on the carbon loading, in mg g and on the carbon usage in the adsorber i.e. the mass of carbon exhausted per unit time, in kg d [43]. 

Thermal regeneration uses heat to combust binders and contaminants. All thermal processes need an initial mechanical step in order to bring the sand to the correct grain size and to screen out any metallic contaminants. This pretreatment may also involve a (partial) abrasion of bentonite and dust removal. The heating of the sand is usually achieved by means of a fluidised bed furnace, operating at temperatures mostly between 700 to 800 °C. Rotary kilns or multiple-hearth furnaces are also used. Heat may be provided by gas combustion, electric heaters or by short wave infra-red emitters. The throughput of these systems ranges from 250 kg/h to more than 5 t/h. 

Technique Multiple hearth furnace (500 °C) with sieving and classification Fluidised bed furnace (780 X ), mechanical size reduction and dedusting Fluidising combustion chamber with magnetic preseparation, simultaneous processing of sand and dust fiom mechanical furan sand regeneration... 

Cost the column as a pressure vessel, Section 10.1 and indude regeneration equipment as a heat exchanger. Section 3.3, or as a multiple hearth furnace. Section 6.21. 

Multiple hearth furnace for regeneration of adsorbent carbon furnace only including drive and motor, exit screw conveyor and inlet feeder. FOB cost = 6 325 000 at carbon feed rate = 1 kg/s with n = 0.60 for the range 0.02-10 kg/s. TM = 2.1-2.2. L/M = 0.3. 

Figure 2.8 Multiple hearth furnace for the thermal regeneration of granular activated carbon.

Figure 11 Carbon regeneration flow diagram. Exhausted carbon is sluiced from adsorbers, dewatered, and regenerated in a thermal furnace (multiple hearth, rotary kiln, infrared, or fluidized bed) the regenerated carbon is quenched and washed before returning to the adsorbers new carbon is washed and added to make up for the loss during regeneration (from Ref. 11).

Figure 1730. Kilns and hearth furnaces Walas, 1959). (a) Temperature profiles in a rotary cement kiln, (b) Space velocities in rotary kilns, (c) Continuous lime kiln for production of approximately 55tons/24hr. (d) Stirred salt cake furnace operating at 1000°F, 11-18 ft dia, 6-10 tons salt/24 hr. (e) Multiple-hearth reactor one with 9 trays, 16 ft dia and 35 ft high roasts 1250 lb/hr iron pyrite. (f) Siements-Martin furnace and heat regenerators a hearth 13 ft wide and 40 ft long makes 10 tons/hr of steel with a residence time of 10 hr.

This is one of the most frequent methods used in the regeneration of exhausted activated carbons. It consists in heating the carbon at temperatures between 873 - 1273 K in different types of furnace such as a rotary kiln, a multiple hearth, a fluidized bed, etc. so that... 

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