Atmosphere reducing furnace
Preparation of controlled atmosphere in atmosphere reducing furnace
I. preparation principle and process of endothermic controllable atmosphere
1. Preparation principle
Endothermic atmosphere is an atmosphere formed by incomplete combustion of raw gas and air less than or equal to half of theoretical air requirements at high temperature and under the action of catalyst.
The preparation of endothermic atmosphere mixing is relatively low, because the mixture itself emits less heat, which is not enough to maintain the continuous combustion reaction. Therefore, the preparation of endothermic controllable atmosphere requires external heat supply.
The relative quantities of CO and CO2, H2 and H2O, H2 and CH4 in the atmosphere can be adjusted by reducing the mixing ratio of air and raw gas, that is, the carbon potential of the atmosphere can be adjusted. Therefore, this atmosphere is called controllable atmosphere.
2. The catalyst
Effect: 1) reduce the reaction temperature. Without catalyst, the reaction temperature must be raised to 1200℃. 2) accelerate the reaction speed and shorten the reaction time.
Catalyst: main ingredients: NiO, through the reaction tank produced by the reducing gas reduction to generate catalytic activity of nickel.
Catalyst support: porous alumina foam brick. Obtained by soaking catalyst solution and drying.
"Poisoning" of catalysts should be prevented in industry.
Poisoning is usually caused by the accumulation of carbon black. The catalytic function can be restored by removing carbon black from the catalyst by combustion.
Methods to restore the catalytic function of poisoned catalyst: 1) take it out and put it in a box-type furnace and heat it to about 850℃, then burn off the carbon black. 2) fill air into the reaction tank and control the temperature in the reaction tank. The temperature is adjusted according to the amount of carbon black in the reaction tank. When there is more carbon black in the reaction tank, the temperature in the reaction tank should be controlled at about 700-800℃. When the carbon black in the reaction tank is less, it is controlled at about 850℃. 3) the carbon black burning time is determined according to the amount of CO and CO2 discharged from the reaction tank. When the CO content in the discharged gas approaches zero and the CO2 content is less than 1%, the carbon black burning can be terminated.
Burning carbon black cycle: general 1 time/week.
3. Preparation process
Feed gas by the pressure reducing valve, flow meter and pressure regulating valve into the mixer, and air through the filter and flow meter into the mixer - gas mixture in the mixer drum into the reaction tank by pump - in 1000-1050 ℃ reaction tank under the effect of nickel-based catalysts for chemical reaction heat absorption type atmosphere - heat type atmosphere inside the cooler to pass through charging is used.
Exothermic controllable atmosphere
1. Preparation principle
Exothermic atmosphere is produced by incomplete combustion of raw gas (LPG, gas or other gas fuels) and more air (n=0.5-0.95).
According to the above equation, it can be seen that: 1) atmosphere with different CO/CO2 ratios can be obtained by changing the amount of air added. When the amount of air is low, the CO/CO2 ratio is high, and the atmosphere is weak in oxidation and decarbonization. On the contrary, if more air is added, the CO/CO2 ratio is small, and the atmosphere has strong oxidation and decarbonization. 2) the more air is added, the higher the proportion of complete combustion will be, and the more gas is produced per unit volume of propane gas, and vice versa.
2. Preparation process
Mixing of raw gas and air → roots pump to burner → combustion and cracking in combustion chamber; complete reaction of unburned part and raw gas through catalyst → reaction product passing into condenser to remove water → purification depending on the situation → exothermic atmosphere.
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