Heating reduction of ammonia synthesis catalyst

It is important to control the vapor concentration, and it is also necessary to work closely with the personnel from the catalyst manufacturer, following their procedures for heating and reduction. Generally, no problems arise, but sometimes company managers want to produce products as quickly as possible, which means that many steps are shortened. We have been using it for five years now, and its activity remains very good.

The quality of the catalyst heating and reduction process has a direct impact on subsequent normal production as well as the catalyst’s service life; it is necessary to follow the heating and reduction procedure provided by the catalyst manufacturer, controlling the heating rate at different stages； Try to increase the airspeed as much as possible ； Strictly control water vapor concentration ； The temperature difference within the same plane should not be too high ； After the reduction is complete, it is necessary to operate at low load for a period of time.

:Time: Follow the plan established by the manufacturer, with the principle of \"three highs and four lows\". The three highs refer to high air velocity, high electric heater power, and high hydrogen ratio. The four lows refer to low water vapor concentration, low temperatures with frequent condensation, low temperature differences at different levels, and a low condensation temperature. This post was last edited by Qingqing de Shui on 2008-12-19 11:15.]

The reduction of ammonia synthesis catalysts is a well-established process. The following points should be taken into consideration: 1. A suitable reduction plan must be developed based on the specific process flow and equipment characteristics, as well as the design of the components inside the synthesis tower and the type of catalyst used. 2. Prior to reduction, it is necessary to prepare the system properly – for example, the electric furnace should be in good working condition and ready for use, and there should be a backup unit for the circulation pump. The towers used for system maintenance should have been inspected and proven to be reliable in terms of quality. All steps involved in installing the components within the tower should proceed without issues. The parameters of the DCS control system should also be checked and adjusted to ensure they are functioning properly, and the system must be reliably isolated. 3. During the reduction process, the transition from the initial stage to the main stage should occur smoothly, with minimal temperature differences across different areas. The water output during the main stage should be uniform, and hydrogen and temperature controls must be stable. It is important to prevent water vapor levels from exceeding 2.5%, and the temperature used for cooling ammonia should be reduced as much as possible； The temperature at the bottom during the final stage should be raised to over 490 degrees to ensure complete reduction. 4. Sufficient time should be allowed during the light-load period to avoid reaching full load too early ； During the transition to normal production, it is necessary to pay attention to the control of the drum liquid level and the ammonia liquid level, in order to prevent faults from causing significant fluctuations in system operation or even accidents ； The process of increasing pressure and dosage should be carried out slowly in stages ； In short, the catalyst exhibits good activity after reduction, but it is not yet very stable; it is highly sensitive to changes in relevant process parameters. Operation should focus on stability, ensuring complete reduction of the catalyst and stability of its active crystal structure, so as to facilitate high-load production in the years to come. 5. Throughout the reduction process, low-pressure water discharge should be used as much as possible to suppress the impact of the ammonia synthesis reaction on the adsorption of reducing hydrogen and the desorption of water ； This post was last edited by FEIJING on 2008-12-19 08:59.]

The temperature rise and reduction process shall be carried out strictly in accordance with the procedure provided by the catalyst manufacturer. 1. At different stages, control the heating rate differently; maintain a high H2 content (favorable for reduction), a low pressure (favorable for reduction), and maximize the space velocity (favorable for reduction). 2. Strictly control the water vapor concentration (1. Adjust the circulation volume. 2. Adjust the heating rate. 3. Adjust pressure, etc.). 3. Keep the temperature difference within the same plane from being too large; if it is, maintain a constant temperature. 4. Strictly control the ammonia cooling temperature. 5. After the reduction process is complete, it is necessary to operate at a low load for a period of time, which helps to extend the service life of the catalyst.

The water vapor concentration must be strictly controlled. Furthermore, rising the temperature too quickly may cause uneven temperatures in the synthesis tower.

We control the water vapor concentration by regulating the temperature; as the temperature rises, the amount of water vapor in the gas phase increases.

That expert could post the synthetic catalyst reduction scheme for everyone to study*.

Catalytic reduction is a process that relies on time; it should be carried out strictly in accordance with the reduction protocol provided by the manufacturer. There’s no need to rush. The reduction process generally consists of 5 stages, including a heating phase, during which the rate of temperature increase needs to be carefully controlled； Early reduction stage ； Reduction main period ； late reduction stage ； During the low-load production phase, it is generally necessary to maintain this condition for 72 hours, after which the pressure and dosage are gradually increased. 2. During the reduction process, it is necessary to control the \"three highs and one low\": high gas velocity, high electric furnace load, high circulating hydrogen level, and low water vapor concentration (we generally keep this below 2.0; however, it shouldn’t be too low either, as that would prolong the reduction time). 3. It is important to ensure that during reduction, the temperature rises without an increase in pressure, and the pressure increases without a rise in temperature. Any changes in temperature or pressure should be done gradually, not too quickly. 4. During reduction, attention must also be paid to radial and axial temperature differences; these should not be too large. If they are, the process should be paused at constant temperature and pressure for a while, and appropriate measures taken depending on the situation, before continuing with the reduction process

①Selection of pressure. Although pressure levels do not change the equilibrium state of the reaction, they can increase the rate of the reduction reaction. When the reduction process enters its main phase, it is necessary to increase the space velocity in order to reduce the water vapor concentration; however, an increase in pressure leads to a greater temperature difference across the catalyst surface. ②Selection of temperature. Raising the temperature helps to increase the reduction rate of the reducing agent and shorten the reduction time, but high temperatures can easily cause the sintering of iron microcrystals in the reducing agent, while high water vapor concentrations also increase. ③Selection of space velocity. Increasing the air velocity can reduce the water vapor concentration on the catalyst surface; while maintaining the rate of temperature rise, the circulation volume should be increased as much as possible. ④Selection of water vapor concentration. The catalyst reaction initially starts from the outer surface of the particles and progresses gradually toward the interior. With a low concentration of water vapor, the moisture inside the catalyst pores can easily escape; therefore, certain requirements are imposed regarding the concentration of reducing water vapor