Ammonia distillation treatment process for residual ammonia water

Abstract

The invention discloses an ammonia distillation treatment process for residual ammonia water. The process aims at an ammonia distillation section, 20% concentrated ammonia water can be produced, and the problem of liquid expansion during desulfurization is solved. An alkali liquor inlet is arranged under a gas phase side sampling port of an ammonia still, so that the content of sulfide in the tower kettle wastewater can be greatly reduced by adding the alkali liquor, and the biochemical treatment cost is reduced. A tar discharge pipe of a bottom seal head of the ammonia still is designed to be inclined, a structure that the tar discharge pipe is vertically downward and then horizontally out of a skirt is not adopted, and steam sleeve heat tracing is added while the tar discharge pipe is inclined. The flowability is increased through inclined discharge, low-temperature solidification is prevented through sleeve heat tracing, and the problem that the tar discharge pipe is blocked is thoroughly solved. The shell side of a dephlegmator adopts a two-section type design, the two sections of shell sides operate in full load, and only one section of shell side operates in low load, so that the overlarge area allowance can be reduced. Cooling water is changed into steam condensate, and the steam condensate is desalted water and is not easy to scale; and through an indirect heat exchange mode, the operation time and the service life of the dephlegmator are obviously prolonged.

Description

technical field [0001] The invention relates to the field of excess ammonia water treatment, in particular to an ammonia distillation process for excess ammonia water. Background technique [0002] Most of the ammonia water formed during the initial cooling of coke oven gas is used as circulating ammonia water, and the excess part is discharged outside, and the discharged part is called residual ammonia water. The remaining ammonia water contains harmful impurities such as coal steam oil, phenol, ammonia, carbon dioxide and hydrogen sulfide, as well as a small amount of germanium-containing compounds, and is the main source of coking industrial sewage. The remaining ammonia water needs to be treated in three stages: oil removal, ammonia steaming and biochemical treatment, and it will be discharged after reaching the standard. [0003] In the prior art, the disadvantage of the ammonia distillation section is that the 8% to 12% ammonia water produced is discharged to the solu...

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Problems solved by technology

[0003] In the prior art, the disadvantage of the ammonia distillation section is that the 8% to 12% ammonia water produced is discharged to the solution circulation tank for a long time, and the desulfurization solution is supplemented with ammonia, which causes the desulfurization solution circulation tank to swell, and the excess desulfurization solution needs to be desulfurized. Outflow treatment, the treatment cost is very high, and the reason for the increase of liquid is that the concentration of ammonia water is too low and the output of ammonia water is too high. Further reducing the temperature of ammonia water after the condensing cooler can obtain concentrated ammonia water with more than 20% ammonia, and the output of ammonia water can be reduced by 50% % or more, but the gas phase after the splitter contains not only ammonia, but also a certain amount of H 2 S and CO 2 , while H 2 S, CO 2 And ammonia in the presence of water, the lower the temperature, the easier it is to form ammonia crystals. According to production experience, when the temperature of ammonia water after the condensing cooler is lower than 40°C, crystallization will occur. During production, the condensing cooler will be strictly controlled. The temperature of ammonia, so the existing technology cannot produce 20% ammonia

[0004] The remaining ammonia contains H 2 S, the remaining ammonia enters the tower and will be fully mixed with sodium hydroxide lye, and sodium hydroxide is a strong base, H 2 S is a weak acid, and when the two meet, an acid-base reaction will occur to form sulfides such as sodium sulfide, and a certain amount of H 2 The solidification of S causes the sulfide content in the tower kettle wastewater to exceed the standard, which is not conducive to biochemical treatment and increases the cost of biochemical treatment

[0005] The existing ammonia distillation tower discharges tar through the tar discharge protruding from the bottom of the head. In actual use, the tar discharge pipe is very easy to block. Tar is denser than water and will be deposited at the bottom of the head. During production, the tar discharge pipe is at the lowest surface, and tar will be deposited preferentially. However, the insulation measures of the tar discharge pipe are not very good. When the temperature is too low, the tar discharge pipe The tar in the pipe will solidify, and it will not have fluidity, resulting in the blockage of the tar discharge pipe, which needs to be unblocked by direct steam blowing, which has brought many problems to the production

[0006] The splitter at the top of the tower uses circulating water to cool down the tube-side medium. It is generally designed to enter at 32°C and exit at 40°C. The design of the heat exchanger generally considers a certain margin (20% to 40% more than the actual demand) ), the area of ​​the shrinker also has a margin, the area is rich, and the temperature of the circulating water outlet will be higher than the design when the load remains unchanged. The temperature of the circulating water outlet is generally 45°C during full-load production, but the coking plant often Reduced production or half-load production, when half-load production, the margin of the shrinker area is larger, the circulating water outlet temperature can reach above 70°C, and the structure speed is accelerated at this temperature, according to experience, half-load During production, there is no temperature difference between the inlet and outlet of the shell-side circulating water of the splitter for half a year. The structure inside the shell side is very serious. The tube side of the splitter is made of titanium, and the cost is very high. Only the shell side can be cleaned to increase production. Management Difficulty and Maintenance Cost

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