Fix nitrogen

In enteric bacteria, expression of the nif genes is under general nitrogen regulation by the ntr system. This system consists of essentially a sensor-activator pair of proteins, encoded by ntrB and ntr(d. When fixed nitrogen is limiting, the sensor, NtrB, phosphorylates (and so activates) the activator,... 

A ruthenium-based catalyst is used but low yields resulting from unexpected side reactions are stiU a problem. Refinement of alternative route ammonia manufacture and advances in genetic engineering, allowing a wider range of plant life to fix nitrogen in situ should provide assurance for long term world food needs. 

Coatiauous kilns were first used ia Germany at Knapsack (20) and later at Trostberg (21). In the Knapsack process, calcium carbide (0.75—2 mm ia size) is fed to a rotary kiln, 3 m ia diameter and 12 m long with 1% slope 1—2% calcium chloride is added to promote the reaction. The kiln produces 12—13 t fixed nitrogen per day. The product is granular and can be sold without further processiag. 

The Sbddeutsche Kalkstickstoffwerke process at Trostberg uses powdered calcium carbide along with recycle product and calcium fluoride ia a rotary kiln at 1000—1100°C. The capacity of a unit is 25 t fixed nitrogen per day. The product passes to a rotary cooler and is granular (21). 

Prompt NO Hydrocarbon fragments (such as C, CH, CH9) may react with atmospheric nitrogen under fuel-rich conditions to yield fixed nitrogen species such as NH, HCN, H9CN, and CN. These, in turn, can be oxidized to NO in the lean zone of the flame. In most flames, especially those from nitrogen-containing fuels, the prompt... 

Fuel-Staged Burners Use of fuel-staged burners is the preferred combustion approach for NO control because gaseous fuels typically contain little or no fixed nitrogen. Figure 27-36 illustrates a fuel-staged natural draft refineiy process heater burner. The fuel is spht into primaiy (30 to 40 percent) and secondary (60 to 70 percent) streams. Furnace gas may be internally recirciJated by the primaiy... 

Leuna-salpeter, m. Leuna saltpeter (ammonium sulfate nitrate), -werk, n. Leuna (fixed-nitrogen) plant. 

The highest fixed nitrogen-containing fertilizer 46.7 wt %, urea is a white solid that is soluble in water and alcohol. It is usually sold in the form of crystals, prills, flakes, or granules. Urea is an active compound that reacts with many reagents. It forms adducts and clathrates with many... 

Because K is so small, the partial pressure of NO in equilibrium with N2 and 02, and hence the amount of NO, must be extremely small, approaching zero. Clearly, this would not be a suitable way to fix nitrogen, at least at 25°C. 

The Haber process, represented by this equation, is now the main source of fixed nitrogen. Its feasibility depends on choosing conditions under which nitrogen and hydrogen react rapidly to give a high yield of ammonia. At 25°C and atmospheric pressure, the position of the equilibrium favors the formation of NH3 (K= 6 x 105). Unfortunately. however, the rate of reaction is virtually zero. Equilibrium is reached more rapidly by raising the temperature. However, because... 

V.A. Kaijavin, Calculations in Technology of Fixed Nitrogen , ONT1 (USSR) (1935)... 

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