Differential pressure double flange level meter applied to iron pentacarbonyl evaporator

Abstract: In the process of producing carbonyl iron powder by the carbonyl method, the liquid pentacarbonyl iron liquid is self-pressurized by the pressure of the storage tank and then enters the evaporator for evaporation. The pentacarbonyl iron gas formed by evaporation enters the decomposer connected to it. Decompose to produce carbonyl iron powder with various indicators. This article mainly discusses the key equipment in the production process of carbonyl iron powder - the control parameters of the pentacarbonyl iron evaporator. Among them, the control of the evaporator liquid level gauge is particularly important. During the production process, different forms of operating failures occurred in the liquid level gauge. According to Analyze the fault phenomenon and find corresponding solutions.

Carbonyl iron powder is one of the most widely used carbonyl metal powders and is widely used in metal injection molding, high specific gravity alloys and other fields. The ultra-fine structural characteristics make it have good electromagnetic wave absorption performance when used in the microwave frequency band higher than the centimeter band. It can be widely used in electronic components, microwave absorption, stealth materials, shielding materials, magnetorheology and magnetic shock absorption. liquid and other fields. At the same time, carbonyl iron powder can also be used instead of cobalt as the binder phase in the production of diamond tools and cemented carbide, reducing the use of expensive cobalt and reducing production costs. In addition, because carbonyl iron powder has excellent comprehensive magnetic properties at high and very high frequencies, it can be used to manufacture magnetic materials such as permeable dielectric iron cores and high-frequency iron powder cores.

Based on the broad market demand for carbonyl iron powder, Jilin Jien Nickel Co., Ltd. has built a new carbonyl iron powder production line. The production raw material is sponge iron, the end product is carbonyl iron powder, and the process product is carbonyl iron liquid. The process flow is shown in Figure 1.

It can be seen in Figure 1 that the key equipment for producing carbonyl iron powder is the evaporator and the decomposer. The key control points of the evaporator device are pressure, temperature and liquid level. Among these major Control indicators are maximized.

1 Test

1. 1 Selection of evaporator level gauge

1. 1. 1 Evaporator structure and physical properties of pentacarbonyl iron

The pentacarbonyl iron liquid evaporator used in this article is a vertical cylindrical structure with a stirring device. The structural diagram is shown in Figure 2.

The chemical formula of pentacarbonyl iron is Fe(CO)5, which is a yellow oily liquid with a melting point of -21 ℃, a boiling point of 102.8 ℃, a liquid density of 1. 457 g/cm3 (21 ℃), and decomposes at 250 ℃ Pure carbonyl iron powder is obtained. Carbonyl iron is insoluble in water and soluble in concentrated sulfuric acid, alcohol, benzene and petroleum ether. When Fe(CO)5 is irradiated by sunlight or ultraviolet rays, it undergoes dimerization to generate Fe2(CO)9 and carbon monoxide. When the pressure of Fe(CO)5 liquid changes, CO gas will be released from the liquid, generating bubbles.

1. 1. 2 Evaporator liquid level gauge selection

The evaporator is a device that continuously flows in and out of carbonyl iron liquid. Its operating pressure is 10 KPa, but due to the carbonyl iron liquid the particularity ofWhen the pressure changes, CO gas will precipitate, causing fluctuations in operating pressure. In addition, since the evaporator is equipped with a stirring device, ultrasonic and radar level gauges cannot be used normally here. After many considerations, the most important thing is to control the measured value of the liquid level gauge. If the measured value of the liquid level gauge is too high, it will cause pentacarbonyl The iron liquid flows into the decomposer, causing the carbonyl iron powder product to be scrapped. Moreover, the presence of liquid in the decomposer may cause explosion safety issues. If the measured value of the liquid level gauge is too low, the output of carbonyl iron powder will decrease. At the same time, due to excessive evaporation, an extremely hard carbonyl iron scab will be formed at the bottom of the evaporator, causing heat insulation problems in the evaporator. Forced to stop.

2. 2 Failure phenomenon of evaporator liquid level gauge

There are two single-loop controls in the evaporator control parameters. One single loop is the evaporator inlet regulating valve and the inlet carbonyl Iron liquid flow meter; the other single loop is the evaporator shell steam inlet regulating valve and evaporator liquid level meter. In the two-loop control, the liquid level control is more difficult and the stability is more difficult. Various problems have occurred during the use of the liquid level gauge, and there are also different liquid level control curves on the monitoring system. The fluctuation curve is shown in Figure 3, and the comparison between the normal curve and the fluctuation curve is shown in Figure 4.