In the synthetic ammonia production process, heat exchange is always accompanied, especially for fertilizer companies, the temperature rises in summer, and the phenomenon that the compressor is not working is common.

In summer, the temperature rises. After the desulfurization of the semi-water gas, the cleaning tower is cleaned. The temperature of the cleaning tower is as high as 40-43cc under the hot sun, so that the saturated vapor pressure of the semi-water gas at 40cc is 880mmH 0 (8.63kPa), and the semi-water gas at 2 600mmH 0(25.50kPa)(G) exits the cleaning tower and enters into the compressor section. Generally, the half-water gas main pipe from the cleaning tower to the compressor section is 100m long, with a flow rate of 8 10m/s, and the temperature can reach 44cc before the compressor reaches the compressor. There is a phenomenon of "weakness" in the aircraft in summer.

In summer, the water temperature is high, the compressor is “weak”, the heat transfer effect is poor, and the energy consumption is high. The main problems restricting the production of synthetic ammonia are the main problems that restrict the production of synthetic ammonia. For fertilizer companies, summer is the peak season for sales, and the production equipment needs to operate at full capacity. In response to the above problems, we have conducted repeated studies and decided to adopt a new type of tubular graphite heat exchanger, which is used before the first stage of the compressor, and has achieved good economic benefits.

1 New type graphite heat exchanger equipment

(1)Impermeable graphite material

Impermeable graphite is a new type of structural material made of artificial graphite and synthetic resin through impregnation, pressing, casting and other methods. The difference between it and all other non-metallic corrosion-resistant materials is that in addition to its high chemical stability, it also It has extremely high thermal conductivity, does not pollute the medium, and is not easy to scale, thus greatly expanding its application range.

In terms of chemical stability, except for strong oxidizing acids and alkalis, impermeable graphite is corrosion-resistant to most chemical media, especially media containing chloride ions. In terms of thermal conductivity, the thermal conductivity of impregnated graphite is

100～l10W/m·K, its thermal conductivity is similar to that of copper and aluminum, which is more than 2.5 times that of ordinary carbon steel. Usually, heat exchangers are made according to this feature.

In terms of thermal stability, phenolic impregnated graphite can generally withstand a temperature of about 170, and its thermal expansion coefficient is very small, about 0.4~0.45×10 /K.

(2) New heat exchange equipment

The two ends of the new-type tubular graphite heat exchanger are fixed tube plates. The tube plate and the heat exchange tube are connected with high elastic corrosion-resistant rubber materials, and three elastic sealings are implemented. The equipment has a simple structure, good shock resistance, and good heat transfer performance. Operation resistance is small, easy to maintain and clean. It completely eliminates the stress damage caused by the obvious difference between the linear expansion coefficient of the binder and the impregnated graphite block material on the traditional graphite heat exchanger structure, and eliminates the "differential elongation" and temperature uneven distribution of the graphite heat exchange tube under the effect of temperature. Destructive effects caused by factors. Even under the condition of large temperature difference, the operation is still stable and reliable. All the equipment adopts active connection, easy to change the tube, and the heat exchange area is not reduced, avoiding the scrapping of the whole machine caused by the blocked tube. The allowable pressure of the new graphite heat exchanger can reach 1.0 MPa, and the operating temperature can reach 150 cc.

2 Application in synthetic ammonia

In order to solve the problem of compressors "weakness in air", some manufacturers used spray-type and jet-type hybrid heat exchangers, and some directly used chilled water for cooling. The former has a series of problems such as high power consumption, loss of effective gas components, and gas-water separation, while the latter has large investment and higher energy consumption. A graphite tube gas cooler is added in front of the compressor. Taking into account the average gas temperature in summer is 46cC, a lower temperature disposable groundwater (temperature l 6) is used to cool the gas, so that the compressor is one-time

The temperature of the outlet can be reduced by more than 10~C in summer, which can always keep the compressor running at full load.

(1) Application analysis

According to the Claberon equation: PV=MRT, it can be known that reducing the air inlet temperature of the first stage of the compressor can increase the air output of the compressor. Calculated on the basis of 8×104t/a synthetic ammonia (investment about 500,000 yuan), the heat transfer area of its new graphite heat exchanger is 712mz. Calculated by reducing 10cc, the gas transmission can be increased by 2-3%.

(2) Economic benefits

Under normal circumstances, the original system produces 280t of ammonia per day, which is converted according to the ammonia output. After the new graphite cooler is put into production, the output can be increased by 280×2.3%=6.44 (). If the high temperature season is calculated based on 150 days per year, the annual output will increase by 6.44× l50=966(fa). According to the synthetic ammonia price of 1,800 yuan/t, the coal consumption per ton of ammonia is 700×1.3=900 yuan, the other costs for ton of ammonia are 50 yuan, and the water consumption is about 500 yuan/day, the annual benefit will increase: (1800—900—50)×966 One l50×500=746.1 million yuan

It can be seen from the above calculations that the use of a new type of graphite heat exchanger in the first stage of the compressor in the synthetic ammonia production device can effectively increase the operating load of the equipment, increase revenue and save energy, and recover the equipment investment in less than a year.

In short, from the use of several manufacturers such as Pingdu Tianzhu. The use of the new graphite heat exchanger has achieved satisfactory results. We believe that its use prospects will be better.