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 40-43℃ under the scorching sun, so that the saturated vapor pressure of the semi-water gas at 40℃ is 880mmH 0 (8.63kPa). At 2 600mmH 0 (25.50kPa) (G), it exits the cleaning tower and enters the compressor section. Generally, the half-water gas main from the cleaning tower to the compressor section is 100m long, with a flow rate of 8 10m/s, and the temperature can reach before the compressor 44°C, so the compressor has a "weakness" phenomenon in summer.

In summer, high water temperature, “weakness” of the compressor, poor heat transfer effect, and high energy consumption 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 undergone repeated research 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, in addition to strong oxidizing acids and alkalis, impermeable graphite is 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 copper and aluminum, 2.5 times more than ordinary carbon steel, and it is usually made into heat exchangers based on 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 to 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 in 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 blockage of the tube. The allowable pressure of the new graphite heat exchanger can reach 1.0 MPa, and the operating temperature can reach 150 ℃.

2 Application in synthetic ammonia

In order to solve the problem of the compressor’s "powerlessness", some manufacturers used spray-type and jet-type hybrid heat exchangers in the past, 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. Considering the average gas temperature in summer is 46°C, a lower temperature one-time ground water (temperature l 6) is used to cool the gas.

The inlet temperature can be reduced by more than 10~C in summer, and the compressor can always be operated at full load.

(1) Application analysis

According to the Claberon equation: PV=MRT, it can be known that reducing the temperature of the first stage of the compressor can increase the compressor's air output. Calculated with 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 to ammonia output. After the new graphite cooler is put into production, the output can be increased by 280×2.3%=6.44 (). Increase the output by 6.44×l50=966(fa). According to the synthetic ammonia price of l800 yuan/t, the coal consumption per ton of ammonia is 700×1.3=900 yuan, other costs for ton of ammonia are 50 yuan, and the water consumption cost is about 500 yuan/day, which will increase the benefit every year: (1800-900-50) ×966一l50×500=746,100 yuan

From the above calculation, it can be seen that the use of a new type of graphite heat exchanger in the compressor section of the synthetic ammonia production device can effectively increase the operating load of the equipment, increase revenue and energy saving, and recover the equipment investment in less than one 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.