The external cooler is a device for cooling the mother liquor of ammonium chloride in the crystallizer, and the former external cooler is made of carbon steel. Although the inner tube of external cooler made of carbon steel has been treated with anticorrosion, its service life is only about 4 years because of the strong corrosiveness of ammonium chloride mother liquor. If the quality of the anti-corrosion layer is inferior, the service life is only about one year. After 5 years of operation, no corrosion was observed in the equipment, and only 5 tubes were damaged by the vibration of the separator due to vibration. After five years of operation, no corrosion was found in the equipment, and only five pipes were damaged due to vibration and wear of the partition.  It has been used for 14 years and the estimated service life is up to 30 years. See Table 3 for economic benefits. Titanium external coolers have a higher investment at a time. At that time, 140,000 yuan per ton of titanium pipes, but still earned 10,595 yuan per year. Steel external coolers are frequently repaired and must be equipped with spare equipment to ensure cleaning and overhaul. Therefore, 11 of the 14 external coolers in the plant have used titanium external coolers.

Project	Titanium external cooler	Steel external cooler
Whole equipment	9.6 million yuan	130,000 yuan
Service life	Expected for 30 years	4 years
Annual depreciation	32,000 yuan	32,500 yuan
Annual savings	500 yuan	0
Increase production throughout the year	336.5t ammonium chloride	0
Annual profit	100,095 yuan	0
Annual income	10,595 yuan

The ammonia-base heavy alkali workshop will use 13#, 18#, and use the domestic titanium umbrella plate cooler. The heat exchange plates are made of TA2 plates, each with a cooling area of 60 m2. A titanium umbrella plate cooler can replace 1.5 shower cooling pipes with a cooling area of ​​3602. The heat transfer efficiency can be increased by 6 times, and the environmental pollution and equipment corrosion caused by seawater vapor and seawater spraying can be eliminated. The economic benefits are compared in Table 4.

Project	Cast iron shower pipe	Titanium umbrella cooler
Whole equipment	13 yuan	150,000 yuan
Service life	3 years	Expected for 20 years
Annual depreciation	43333 yuan	7500 years
Annual savings	0	35,833 yuan
Whole equipment	7000h	7000h
Annual running time	15755000m3	525000m3
Seawater consumption	0	1050000m3
Saving sea water	0	262500kW·h
Save battery	0	13125 yuan
Saving value	7000h	7000h
Saving value throughout the year		48958 yuan