RK-A202 Oxidation Ammonia Synthesis Catalyst and RK-A202H Pre-reduced Ammonia Synthesis Catalyst are new types of FeO-based ammonia synthesis catalyst invented and produced by Dalian Reak.
Compared with the existing industrial ammonia synthesis catalyst, RK-A202 Ferrous Oxide Based Ammonia Synthesis Catalyst has characteristics including easy restoration, high catalytic activity, find activity under low temperature and low pressure, wide applicable pressure and temperature range, excellent drug and heat resistance, high mechanical strength and so on.
RK-A202H Pre-reduced Ammonia Synthesis Catalyst is produced by highly active RK-A202 ferrous oxide based catalyst in a special pre-reduced production device after restoration and stabilization. It has high catalytic activity, fine activity under low temperature and low pressure, easy activation and relatively low activity temperature. Made by angle grinding technology, the bed resistance is lowered during application.
1.Physical and Chemical Properties of Basic Components
RK-A202 Chemical Components (Standard Value)：
Fe：≥69 wt.% ；
FeO / Fe2O3 ：4~9 wt.%；
RK-A202H Chemical Components (Standard Value)：
Fe：≥83 wt.% ；
FeO / Fe2O3 ：4~9 wt.%；
The oxygen content absorbed by the catalyst during stabilization (passivation) is about 2% of the catalyst weight.
RK-A202 Oxidation State Ammonia Synthesis Catalyst
Bulk Phase： Fe1-xO Wustite Ferrous Oxide
Auxiliary： Solid Solution in Bulk Phase
Crystal Structure：NaCl（rock salt）
Theoretical Oxygen Content：22.27%
RK-A202H Pre-reduced State Ammonia Synthesis Catalyst
Bulk Phase：Active and porous absence of a-Fe, a phase, F phase and auxiliary solid solution in bulk phase
Crystal Structure： (bcc) Body-centered cubic
Passivation Film Thickness：10nm
Catalyst Shape：The appearance of the catalyst is black and glossy irregular particles with no magnetism.
Catalyst Size：The product particle size has specifications including 1.5~3.0mm, 2.2~3.3mm, 3.3~4.7mm, 4.7~6.7mm, 6.7~9.4mm, 9.4~13.0mm and 3~6 mm, 4.5~8 mm, 6~10 mm, 8~12 mm and so on, special particle size can be provided as required by users.
RK-A202H Catalyst has the same product particle with RK-A202 Catalyst.
RK-A202：2.95-3.45，the bulk density increase slightly with particle size。
RK-A202H：2.45-2.85，the bulk density increase slightly with particle size。
Factor of Porosity：40-45%
Exposed to the air, catalyst is easy to become damp and cause precipitation of soluble potassium salts and decreased activity, oxygen, water vapor, carbon monoxide, carbon dioxide and sulfur, phosphorus, chlorine, arsenic components, oil and so on are toxic to catalyst by causing temporary or permanent poisoning of catalyst. RK-A202H Pre-reduced Catalyst is stable under 100℃, and will be oxidized and heated in air if the temperature is higher than 100℃.
The catalyst is only active after restoration and must be protected by nitrogen during parking. It must be passivated when it needs to be unloaded.
2.Scope of Application
RK-A202 and RK-A202H Pre-reduced Ammonia Synthesis Catalyst is mainly used in ammonia production by hydrogen nitrogen mixture in ammonia industry, and can also be used in making pure hydrogen nitrogen by ammonia decomposition.
RK-A202 Catalyst is only active after restoration by hydrogen nitrogen in the synthetic tower. RK-A202H Catalyst is Pre-reduced Catalyst and the restoration time is only 20%~30% of RK-A202.
RK-A202 and RK-A202H Catalysts are applicable for various types of synthetic towers in large or medium or small synthetic ammonia plants. RK-A202 and RK-A202H Catalysts can be sued for all pressure range with industrial significance, and are widely applicable to all kinds of high and low pressure flows, especially for medium and low pressure ammonia and the temperature should be reduced accordingly with reduction of the pressure. The minimum activity temperature of RK-A202/RK-A202H in industrial application is 260-280℃, the highest heat-resisting temperature of RK-A202/RK-A202H is 530℃, and the heat-resistant temperature in the short term is 550℃.
Heating Rate during Restoration：50℃/h
3.Quality Standard of Catalyst Products
The quality of RK-A202 and RK-A202H Catalysts follows the HG/T3550-2013 standard.
Pressure: 15Mpa, Space Velocity: 30000h-1, 20 hours of heat resistance under 500℃, no less than 14.5% of exit ammonia.
All preparations must be done before filling. Specific requirements for various types of towers (furnaces) shall be strictly followed by operation manual of ammonia plants. Before filling of the tower, the model, specification size and quantity of the catalyst should be carefully checked barrel by barrel.
The catalyst should be sieved before filling to remove the powder and fine grain generated by careless handling during transportation. The sieving should be conducted during the filling of the tower as the catalyst should not be exposed in air for a long time to avoid moisture and contact with oil, dust and debris to keep clean.
The catalyst should be evenly distributed in the whole cross section of the bed layer and the surface of the catalyst bed should always remain basically horizontal during the filling.
The filling of the catalyst should be compact and uniform in order to facilitate equal distribution of airflow to improve the production capacity and prolong the service life. The filling should be stopped each time when the bed layer raises a certain height (300 mm) and should be vibrated or flattened. For Kellogg-synthetic tower with axial flow type gas, manual work of flattening is only needed, while for Topsoe radial synthetic tower, uneven up and down filling may cause the gas drifts, so the vibration is indispensable. Method of vibration is: insert the vibrator into the holes of specific template to vibrate in proper sequence by systematically selecting the vibration node with same vibration strength to acquire homogeneous catalyst bed layer and produce the least amount of dust.
Make the filling records carefully. During the filling, the bulk density should be checked as required to ensure the correct weight and volume is reached and the proper bulk density is reached.
As the oxide film of the surface of catalyst is easy to be damaged due to collision and friction, the sieving and filling process of pre-reduced catalyst should be carefully conducted. During the filling process, the temperature of the synthetic tower should be monitored for rising or not. If the temperature rises, the filling should be carried out under protection of nitrogen and after filling, the tower should be immediately sealed, purged and the temperature-increasing reduction of the catalyst should be carried out in time.
RK-A202 Catalyst does not have catalytic activity before restoration and it must be restored before use. The catalyst activity mainly depends on its chemical composition and preparation method, while whether the restoration is even and thorough or not and the control of parameters for restoration conditions including temperature, pressure, vapor concentration, space velocity, gas composition and so on is appropriate or not also greatly affect the activity and service life of the catalyst. Therefore, restoration of ammonia synthesis catalyst is one of the key factors in ammonia production and should be strictly controlled.
RK-A202 Catalyst has the characteristic of easy restoration by having low restoration temperature, fast restoration speed and fine activity under low temperature and low pressure. The initial restoration temperature of RK-A202H Catalyst is 320~330℃, water output is fast when the temperature is higher than 400℃, the restoration and water output main stage temperature is 400~430℃ and the final restoration temperature is 480~490℃.
The restoration process of RK-A202H Ammonia Synthesis Catalyst can also be divided into several stages and the temperatures of each stage are roughly as follows: normal temperature ~340℃ at temperature raising period, 340~400℃at initial restoration period, 400~430℃ at main earlier restoration period, 430~460℃at main later restoration period, 460~490℃ at the end of the restoration period and light duty production (~450℃).
The theoretical water output is about 250kg/ton of restoration of RK-A202H Catalyst.
RK-A202H Catalyst should be better restored by “two highs three lows method”, i.e. high hydrogen, high space velocity, low temperature, low pressure and low vapor concentration. The operation with high space velocity, low temperature and low pressure is beneficial to control and reduce the vapor concentration in restoration, avoid generation or eliminate coplanar temperature difference to make restoration even and thorough, and improve the restoration quality and shorten the restoration time.
Control of the hot spots of the whole restoration process is required to be stable and the temperature should be gradually promoted according to the predetermined plan. Pressure should be kept stable during the restoration process, as stability of pressure is the key of stability of the restoration process, and the stability of pressure is beneficial to the control of temperature.
The quality and volume of supplementary gas must be guaranteed during the restoration period, and the trace of supplementary gas must be less than 20ppm, also, and the water vapor generated in the circulation gas restoration should be removed as much as possible.
The basis of determination of the end of restoration is mainly temperature and vapor concentration, as well as the water output for reference. When the hot port reaches 480~490℃, the bottom temperature reaches 460℃ and lasts for 6 hours, and the vapor concentration is lower than 200ppm for continuous 4 hours, the restoration can be regarded as ended.
After restoration, the synthetic circuit of RK-A202H Catalyst must be replaced clean before temperature rise to make the oxygen content in the circuit under normal pressure less than 1000ppm.
As pre-reduced catalyst absorbs oxygen content of about 2% of the weight of catalyst during the stabilization process, it requires activation by reduction before use. The restoration water output of pre-reduced catalyst product per ton is 20-30kg. The restoration activation method of RK-A202H Catalyst is basically the same with the temperature-increasing restoration method of oxidation state RK-A202 Catalyst, however, the oxygen absorbed in passivation of pre-reduced catalyst can be released at low temperature with initial restoration temperature of ~220℃, and due to low oxygen content and water output of pre-reduced catalyst, its restoration (activation) time can be greatly shortened.
Ferrous oxide based ammonia synthesis catalyst is extremely easy to be restored with relatively narrow water output peak temperature zone and fast restoration water output. With the existing industrial technology and equipment, the restoration is usually adopted with the method of suppressing the restoration speed so as to avoid serious excess of water vapor and serious loss of the activity. Part of whole tower (furnace) use of RK-A202H Pre-reduced Catalyst can not only greatly shorten the restoration time, save massive power and raw materials, put into production ahead of time, but also make the restoration activation simple and easy to control, eliminate the unreliability of success or failure of the restoration and improve the restoration quality.
According to the feature of extremely easy to be restored of ferrous oxide based ammonia synthesis catalyst and the user’s existing equipment conditions, we kindly recommend to users the above economic and application advantages of RK-A202H Pre-reduced Catalyst.
6.Normal Operation and Service Condition
The service temperature of RK-A202 and RK-A202H Catalysts is from 330 to 500℃ and can reach 510℃ in the later period. The hot-spot temperature in early use may be from 430 to 450℃ (the lower limit is advisable under low pressure for operation), and can be appropriately gradually raised with service time prolonging.
The operation strives to be steady by strictly following the regulations. The driving, parking, temperature raising and lowering and pressure raising and lowering should be strictly executed according to the regulations or targets, to prevent damage caused to the catalyst by intense fluctuation of temperature and pressure. Normal operation should control temperature, pressure, flow, ratio of hydrogen to nitrogen, ammonia cooling temperature and stability of other parameters, which is conducive to stable and high yields, as well as protecting the catalyst.
Infinitesimal oxycompound (oxygen, carbon monoxide, carbon dioxide, water vapor etc.), sulfur, phosphorus, chlorine, arsenic compounds, copper fluid, oil and so on can all cause temporary or permanent catalyst poisoning, and should be strictly controlled according to the regulations to prevent traces of poison from entering into the synthetic tower, otherwise, the activity and service life of the catalyst will be significantly reduced.
The service life of the catalyst is closely related to the temperature-increasing reduction, gas purification, operation conditions and so on. If the gas purification and operation conditions are strictly controlled, the service life of RK-A202 and RK-A202H Catalysts can reach 10-15 years.
7.Transport Storage and Maintenance
1）The catalyst is sealed with metal buckets.
2）During the transportation, tumbling impact should be avoided for fear of damage of the packing bucket, wearing and powdering of the catalyst, and heating and oxidation of pre-reduced catalyst due to damage of surface oxide film. The cover of the bucket should remain up when lifted.
3）The catalyst should be strictly on guard against moisture during transport and storage. The packaged products shall be stored in a dry warehouse and should be equipped with rainproof facilities during transport. Damaged buckets and slack barrelheads caused by severe impact during transport should be resealed to prevent the catalyst from being exposed to the sun and too high environmental temperature.
4）Noxious substance including oil, sulfur, phosphorus, chlorine, arsenic and so on and other chemical pollution is prohibited.
5）The packing marks should keep intact and clean during storage and transport for convenience in checking the model and specification size.