Electrical preheater

During system start-up, an electric preheater and the isopropyl alcohol feed are used to heat the reactor to the desired operating temperature. When the reactor is at operating temperature, the preheater is turned off, hydrolysate flow is initiated, and auxiliary fuel and water flows are adjusted to control the temperature at the set point. 

The base price of the MMC-5 unit is 56,200 (1992 dollars). For the thermal oxidizer portion of the MMC-5 unit, maximum daily fuel cost for natural gas would be 60 (1992 dollars), and maximum daily fuel cost for propane would be 95 (1992 dollars). For the catalytic oxidizer portion of the MMC-5 unit, the maximum daily electrical cost would be 22 (1992 dollars), assuming an electric preheater rated for 36 kW at 480 V is used at 240 V. The daily cost to operate the vacuum/compression unit for the MMC-5 is 6 (1992 dollars), assuming a 3-hp electric motor drawing 2.3 kW is used. 

Weigh accurately about 200 mg of a dned, extracted wood meal (40-60 mesh) with known moisture and extractives contents or 50 mg of a dned, purified lignin preparation The specimen, 7ml of 2M NaOH, and 0 4ml of freshly distilled nitrobenzene are placed m a 10-ml stainless steel bomb (Note 1) The bomb is sealed tightly with a screw cap fitted with a Teflon gasket and heated at 170°C for 2 5h m an electrically preheated (170°C), thermostated aluminum block with six holes to accommodate the cylindrically shaped bombs or in a thermostated oil bath The bomb is shaken occasionally and, after the heating period, is removed from the heater and cooled with ice water The oxidation mixture is transferred to a liquid-liquid extractor, and extracted continuously with CHCI, for 4h to remove nitrobenzene reduction products and any excess nitrobenzene The oxidation mixture is acidified to pH 3-4 with cone HC1, and further extracted continuously with CHCI, for 48 h The solvent from the second CHCI, solution is removed at 40°C under reduced pressure to obtain the nitrobenzene oxidation mixture The mixture is then dissolved m 5 ml of CH2C12 and transferred to a 10-ml volumetric flask The solution is made up to 10 ml... 

Table 1 contains characteristic data and dimensions of the pilot plant. The reactor is manufactured with stainless steel and is insulated. The wann up is carried out with electrical preheating of all air streams and by combustion in both zones. The whole warm up lasts about 4 hours. An oil feeder was installed into the riser, which gives the possibility to change the temperature level of the system without varying other operation parameters. With this installation parameter studies can be carried out very easily. 

Catalytic combustor with electrical preheater for start up and additions of hydrogen to heat the catalyst. 

The non-reversing test furnace used combustion air electrically preheated to llOOC and conventional dual-impulse under port burners fired on natural gas. Water-cooled injectors (called Auxiliary Injectors) were used to allow the gas for auxiliaiy combustion to be injected in many locations and directions. 

Main origin of the start-up time demand was the subsequent heating of a consecutive chain of reactors. Electrical preheating of the inlet section of the reformer monolith reduced the time demand for preheating. The prototype fuel processor had a weight of 18 kg and a volume of 401 (without insulation). 

MM and Mazzoni prefer an electric preheater in a closed circuit. Dried process air is circulated through the converter tower, hot gas filter and electrical elements. Electrical heating offers the possibility of variable heat input. For example, during weekend stoppage (not recommended ) the electrical preheater can be set to maintain a high temperature in die converter tower and hot gas filter. This results in a quick start-up, which contributes to long catalyst life and consistendy high conversion. Moreover, a rapid start-up will increase the actual effective production time. 

Evaporator Condenser 0 Random packing Electric preheated (S> Flow control Alimentation pump Exchanger d> hydraulic keep shower... 

Fig. 3. Diagram of the electrical preheating stage of the Fiall-Fieroult electrolysis cell - from (Goulet, 2004).

Marceau, D., Pilote, S., et al. (2011). "Advanced numerical simulation of the thermo-electro-chemo-mechanical behaviour of Hall-Heroult cells xmder electrical preheating." Light Metals 2011 1041-1046. 

Resistance electrical preheating Short time High-temperatuie gradients during preheating, uneven temperature distribution at the surface of cathode... 

Fig. 2.13 Comparison of (a) resistance electrical preheating and (b) thermal preheating temperature regimes temperature gradients at the bottom—fi ont view, side view redrawn from [10]...

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