Improve the quality of crude ammonia gas a) Improve the stripping effect The sulfur-containing sewage stripping tower is transformed from the hydrogen sulfide stripping tower in the original double-tower process. The upper and lower towers of the side-line pumping outlet have the same diameter and the same opening ratio. However, due to the removal of 50% to 60% of the stripping steam on the side line, the gas phase load of the hydrogen sulfide stripping section is sharply reduced, the valve hole power factor is lowered, the tray efficiency is lowered, the stripping effect is not good, and a large amount of hydrogen sulfide gas is taken. To the side line system, the content of hydrogen sulfide in the crude ammonia gas is high. To this end, according to the calculation results, the hydrogen sulfide stripping section tray float valve is changed from 64 plugs to 38, so that the tray opening ratio is reduced from 9.74% to 5.78%, and the valve hole dynamic factor is increased from 4.4 to 9.5. The stripping effect of the hydrogen sulfide stripping section is greatly improved, the A/S molecular ratio in the side line gas is increased, and the ammonia content in the crude ammonia gas after the segregation is increased from 97% to over 99%, and the sulfurization in the crude ammonia gas is increased. The hydrogen content is reduced from 8000×10-6 (8000 ppm) to 5000×10-6 (5000 ppm), which provides high-purity crude ammonia gas for further purification, and greatly improves the quality of the purified ammonia gas.
b) Improving the temperature of the stripping tower to control the temperature of the stripping tower, especially whether the temperature in the stripping tower is stable or not, is an important parameter affecting the smooth operation, affecting the quality of ammonia. The original design is to use the cascade temperature adjustment of the tower top temperature and the cold feed amount to achieve stable temperature in the middle and upper parts of the tower. Due to the top temperature interference factors, the lag is serious and it is impossible to operate. In the actual production, the temperature of the cold feed is manually controlled by the operation experience to complete the control of the temperature in the middle and upper parts of the tower, which causes the temperature of the middle and upper parts to fluctuate within a large range, so that the operation fluctuates and the quality of the ammonia gas is unstable. The temperature of the packing section and the cold feed quantity which are sensitive to the change of cold feed amount are changed to cascade adjustment, so that the temperature control in the middle and upper part of the stripping tower is stable, the operation is stable, and the quality of ammonia gas is also stable.
Reconstruction device to ensure the quality of refining a) Switch to high-speed pump to ensure the refining effect The ammonia circulating pump is one of the important equipments to ensure the ammonia refining effect of concentrated ammonia washing. However, due to the saturated or supersaturated state of concentrated ammonia in the production process, the original The gear pump is not suitable for working conditions, it is easy to evacuate, and it is difficult to adjust the pump to re-upload after pumping out. It is often that the ammonia gas enters the ammonia compressor without refining, so that the refining effect cannot be guaranteed. For the characteristics of circulating fluid, GSBI high-speed pump with good corrosion resistance and suitable process conditions is selected. The high-speed pump adopts open radial straight blades, and an axial flow induction wheel is installed in front of the blades to effectively solve the problem of evacuation of the ammonia circulating pump, and the refining effect is ensured, so that the hydrogen sulfide content in the refined ammonia gas is controlled. 40 × 10-6 (40 ppm) or less.
b) After the ammonia is changed, the refiner is a crystallization tank. The ammonia refiner is originally ammonia gas bubbling through concentrated ammonia water, and the NH3/H2S molecular ratio is controlled to be greater than 30 to further remove hydrogen sulfide. However, it is difficult to control in actual operation, and the application effect is not good. According to the freeze crystallization process, the ammonia refiner is changed into a crystallization tank, and the liquid ammonia is replenished in the tank, and the ammonia gas is bubbled through the liquid ammonia to form hydrogen sulfide to form ammonium hydrogen sulfide or ammonium sulfide crystals to remove hydrogen sulfide. The method is easy to control, the operation is simple, the hydrogen sulfide content is controlled to be less than 10×10-6 (10ppm), and the operating temperature is lower (-10～0°C), so that the ammonia compressor suction temperature is controlled at -5 to 5 °C. .
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