Type A110 ammonia synthesis catalyst
Type A110 ammonia synthesis catalyst is mainly used in chemical fertilizer industry in ammonia synthesis. It has high catalytic feature at a low temperature and holds excellent heat resistance，poison resistance and the characteristics of easy to restore. So it is an ideal of ammonia synthesis catalyst. This product can also be applied in metallurgy, vacuum tube industry. Ammonia is decomposed into pure nitrogen and hydrogen.
二、hysical and Chemical Properties and Main Component
Type A110 ammonia synthesis catalyst is black, with magnetic irregular solid particles with metallic luster. Particle size can be divided into: 1.5-3.0mm, 2.2-3.3mm, 3.3-4.7mm, 6.7-9.4mm, 9.4-13.0mm, Other size can according to user requirements for processing.
Type A110 ammonia synthesis catalyst bulk density is 2.7-3.0kg/L
Type A110 ammonia synthesis catalyst is easy to be affected with damp when it is exposed to the air. It can cause potassium precipitation decreases after reduction activity. Restored catalyst will quickly lose active spontaneous combustion when it is exposed to the air.
Compounds of sulfur, phosphorus and arsenic, copper liquid, the oil and the oxygen containing compounds all can cause temporary poisoning and permanent poisoning of the catalyst.
Type A110 ammonia synthesis catalyst is easy to restore. Ii starts out of the water when it is 300~330℃, water a lot of water when it is 380~420℃.The main phase of watering is 420~480℃. The highest reduction temperature is 500℃.
Detection of activity: In laboratory conditions, with the pressure of 15.0 MPa, Airspeed 3×104h-1, temperature 425 ℃, the percentage of export ammonia reactor volume is not less than 13.5%. When the temperature rise to 500 ℃ and after 20 hours of heat, the percentage of reactor outlet ammonia volume is still no less than 13.5% under the same conditions.
Main components of Type A110 ammonia synthesis catalyst include: Fe3O4, Al2O3, K2O, CaO.
三、The Loading of Catalyst
Type TA201-2 ammonia synthesis catalyst is packed in iron drums (or plastic). Because of shipping process will make a small amount of catalyst wear edges, there should be sieve catalyst before loading, to remove powder. At the time of loading we should choose the sunny weather, preventing moisture and avoiding contact with oil.
Before catalyst loading, we must carefully check installation quality requirements of synthesis tower internal parts. Sealing parts must to be ensured no leakage, the impurities to be cleaned up, and prepare for packing tools.
When loading, it is better to put a layer of big particle catalysts in the bottom and the upper and the bottom of the case. Relatively small size catalyst is loaded in tower in the upper boundary, relatively large particle catalyst is loaded in the central.
The choice of catalyst particle size can be decided according to tower model and process conditions. In the system pressure condition allowed, we try to use small particles in order to improve the synthesis tower production capacity. (shaft to the tower for the radial as far as possible small particles catalyst). In the process of loading Catalyst, we need keep consistent reasonable, and strive to even, all kinds of granularity theory loading. Don't allow poured out on point or cant together to flatten out again, otherwise the catalyst of small particles stay in the middle, larger particles on the rolls, which can cause gas flow deviation.
Loading can use tapered containers or funnel available from the mouth in uniform. When the axial section is loaded 50 centimeters, longitude section 30 centimeters, we should measure the corresponding value of volume and weight of the loading, and compact it using aluminum bars. Resolutely put an end to topple and fall on one side of the tower and cause nonuniform. When reloading, try to shortened the exposure duration of catalyst in the air and avoid pollution with other chemicals.
四、Temperature-rising Reduction of Catalyst
The main reduction reaction is as follows:Fe3O4+4H2=3Fe+4H2O
The theoretic hydraulic discharge of Type A110 ammonia synthesis catalyst holds 29% of its weight of catalyst.
Type A110 ammonia synthesis catalysts hold low catalytic activity in the oxidation state, but hold high catalytic activity when backing to a-Fe. So scientifically controlling the condition of temperature-rising reduction plays an important role in the service life of catalyst and the production of synthesis ammonia.
Reasonable control the pressure and space velocity in the process of reduction:
In the early reduction, it should be conducted at lower pressure, space velocity in order to make the upper tower catalyst can restore completely. During the middle and last period, we can gradually increase airspeed and pressure making full use of the heat of reaction to improve the bottom temperature and reduce the axial temperature difference.
In the reduction process, circulating hydrogen content should be controlled in more than 70%. The concentration of water vapor out of tower should less than 2.0g/Nm3.The concentration of water vapor can be adjusted according to temperature, pressure, space velocity.
In the process of reduction, ammonia cold temperature should be controlled below 15 ℃, especially in the production and reduction process of One Tower, in order to avoid trace moisture enter into the synthesis tower.
Reduction destination judgment:
①Continuous determination of water vapor concentration acuities were less 0.2 g/Nm3
②Hot spot temperature is 500 ℃,and the bottom temperature above 460 ℃ with 8-10 hours.
③the water yield attaches more than 90% of of theoretical water yield. When three conditions are set up at the same time, it can be produced in low temperature and light load.
Temperature and light load production process should be steady and slow, bewaring of over temperature phenomenon.
The normal production operation
Catalyst should produce by light load to for 1 to 2 days after the reduction，avoiding that immediately adding load makes the crystal structure of the catalyst have dramatic changes and influence the service life and activity of catalyst.
The early production hot spot temperature should be controlled in 460 + 5 ℃.
In the early period, the catalytic activity is high, and responsive to gas composition change, so H2/N2 should be controlled in 2.2-2.8, making the operation stability and avoiding overheating.
Control the operating temperature reasonably. It is not suitable to improve hot temperature too early and it is suitable to increase temperature with 5 ℃ one time.
In the process of operation，we must strictly control the content of CO+CO2 in the synthesis gas into the tower below 25PPM.