Technology for reclaiming hydrogen chloride tail gas in chemical production

Abstract

The invention discloses technology for reclaiming hydrogen chloride tail gas in chemical production, which overcomes the defects of large transfer amount of absorbent between absorption towers, disadvantage of industrialized continuous production, poor effect of absorbing the hydrogen chloride tail gas, waste of time, energy and water resources, environment pollution, low byproduct gains and the like in the prior process for reclaiming the hydrogen chloride tail gas. The technology (attached drawing) achieves simple hydrogen chloride reclaiming process operation, low engineering manufacturingcost, little energy consumption, little industrial water, high hydrogen chloride reclaiming efficiency, high byproduct gains, environmental protection and advantage of industrialized continuous production by optimizing and combining exchange circulating technology in hydrogen chloride absorption sequence through a bubble absorption tower, technology for controlling the tower temperature to between10 and 30 DEG C according to the order of sequence, technology for matching and using dryer and deionized water and hydrogen chloride absorbent such as anhydrous ethanol, absolute alcohol and the like and series of technology for separating a neutralized product and a neutralizer such as volatile alkali ammonia water, pyridine and the like.

Description

1. Technical field [0001] This patent belongs to the field of fine chemical technology and relates to the recovery process technology of hydrogen chloride tail gas in chemical production. 2. Background technology [0002] At present, the recovery technology of hydrogen chloride tail gas in industry mainly adopts jet pump. The main working principle of the jet pump is to use water to spray out at a certain speed in the jet pump, and the jet flow forms a certain negative pressure in the jet pump, and the negative pressure sucks the hydrogen chloride gas to be treated to travel and contact with the jetted water. . During the contact process between water and hydrogen chloride gas, hydrogen chloride is dissolved in water to achieve the purpose of hydrogen chloride tail gas recovery. Two examples are given below to illustrate the current status of hydrogen chloride tail gas recovery technology. see the first example figure 1 , which is a flow chart of the treatment system for...

AI Technical Summary

Problems solved by technology

[0003] Can see by comprehensive analysis, existing hydrogen chloride tail gas recovery process mainly has the shortcoming of following four aspects: 1) dilute hydrochloric acid is transferred from an absorption tower to another absorption tower to absorb hydrogen chloride to produce concentrated hydrochloric acid with circulation pump, The transfer amount of dilute hydrochloric acid is very big like this, especially in the second case transfer needs long time, is unfavorable for suitability for industrialized continuous production, promptly wasted time, wasted energy and polluted environment again; The method of using the generated negative pressure to suck the hydrogen chloride tail gas not only needs a large amount of absorbent, but also when water or dilute hydrochloric acid is used as the absorbent, the hydrogen chloride gas is very weak during the high-speed jet movement. Difficult to contact with water or dilute hydrochloric acid in all directions, resulting in slow dissolution of hydrogen chloride gas and poor absorption of hydrogen chloride tail gas. In addition, the jet pump method is not suitable for absorbents with high vapor pressure, such as ethanol, etc. , easy to volatilize and generate mist, and the vacuum produced is small, so the amount of hydrogen chloride gas sucked is also small; 3) in the case of the hydrogen chloride waste gas treatment system shown in the first example ( figure 1 ), there are two unfavorable factors, one is to use the aqueous solution containing high concentration hydrogen chloride as the water absorbent of the last hydrogen chloride gas (wherein the hydrogen chloride content is very low), its absorption effect to the hydrogen chloride tail gas will be very poor, because when When the concentration of hydrochloric acid in the aqueous solution reaches near saturation, the ability to absorb hydrogen chloride will decrease, especially when the concentration of hydrogen chloride tail gas is relatively small, its absorption effect will be even worse. In fact, according to the principle of gas-liquid absorption equilibrium, it contains a small amount of hydrogen chloride Not only will the tail gas not be absorbed, but it may also take part of the hydrogen chloride gas from the high-concentration hydrochloric acid absorption liquid into the neutralization tower, which will cause waste of hydrogen chloride gas and sodium hydroxide in the neutralization tower; another After the hydrogen chloride tail gas enters the sodium hydroxide aqueous solution in the neutralization tower, sodium chloride will be generated. With the increase of the concentration of sodium chloride in the solution and the decrease of the concentration of sodium hydroxide, the ability of the neutralization liquid to absorb hydrogen chloride gas will decrease. The hydrogen chloride absorption system will have to face two choices of polluting the environment: one is to continue to use the neutralizing liquid, and a large amount of hydrogen chloride gas will leak into the atmosphere; the other is to discard the mixed liquid of sodium chloride and sodium hydroxide , replace with a new sodium hydroxide absorption solution, because sodium chloride and sodium hydroxide have a high solubility in water, it is difficult to separate the two, and the mixed sodium chloride and sodium hydroxide has no industrial application value 4) In the case of the second case of recycling hydrogen chloride process technology ( figure 2 ), the original process ( figure 2 Left) the kind of direct discharge of the acidic water in the packed tower, the water consumption is large, the hydrogen chloride gas is wasted, and the disadvantages of polluting the environment have been mentioned in this document, so I won’t go into details here, but in the improved process ( figure 2 Right), although the calcium hydroxide solution can be used as the hydrogen chloride tail gas absorbent to separate the generated calcium chloride precipitate, but the water solubility of calcium hydroxide is very small, the absorption capacity is low, and the by-product calcium chloride has low economic benefits, which is harmful to hydrogen chloride. gas is still a waste

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