Use of ore smelting flue gas to eliminate smoke

1. The waste heat contains the CO-containing gas produced by the reduction and melting. It is self-evident that most of it can be used as a fuel. However, the flue gas of the smelting furnace generally leaves the furnace at a high temperature, so the recovery of sensible heat is an important The problem is that there is generally the use of heat exchange to preheat the air and the Shanghai material, and there is also the generation of Yanqi through the waste heat boiler. The air preheating method can be divided into two types: a heat exchanger and a regenerator. A flue gas heat exchanger and the air via the wall (refractory or metal) on one side flows through the respective passage side heat exchanger. The regenerator is a substance that uses high-heat flue gas (brick wall, etc.) as a heat transfer medium to heat the air or the emblem gas with its sensible heat. The flue gas alternates with the air through the same road. The waste heat boiler is used to generate superheated steam, and is used for power generation, process heating, and heating. If the smelting gas contains smoke, the water pipe type is used, but the dust and slag are not allowed to be troubled. Therefore, dust removal equipment should be installed as needed. The figure below shows an example of a flash furnace waste heat boiler. Copper reverberatory furnaces are usually equipped with two boilers, one of which is used to clean the smoke.

Figure 3-65 Flash Surplus Heat Boiler

2. Recovery of SO2 gas The flue gas of the sulfide ore smelting furnace contains SO2, thus causing smoke damage. Under normal circumstances, it is necessary to eliminate the damage and try to recover S02. Although it also produces sulfurous acid or monomeric sulfur, it is more weighted by SO2 + 1/2O2 -> SO3 by means of a catalyst to produce sulfuric acid. The method of producing dilute sulfuric acid by using NO2 as an oxidation catalyst is called a nitric acid method. In the past, the nitric acid method has been applied because the smelting flue gas is impure, the SO2 concentration is also low, and the composition and amount vary greatly. However, due to the problems of quality and transportation, and the danger of nitrogen oxide gas, people are not satisfied with the law. In recent years, sulfuric acid has been produced by a contact method using v2O5 as a solid catalyst. Contact 祛 requires strict purification of gas, so the construction cost is high, and the minimum economic concentration of SO2 is required to be 4% or more (2% by nitric acid method), although the difficulty exists, the purity of sulfuric acid produced by this method is high, and the price is also high. High, in addition to the production of fuming sulfuric acid. Figure 3-66 shows an example of a process for making a sulphuric acid plant by contact. In order to maintain the function of the solid catalyst, in addition to thorough dust removal, arsenic , bake, etc., which are easily poisoned by the catalyst, should be removed. Further, since SO3 and water to form sulfuric acid mist, not only the corrosion of iron and generation of FeSO4 wall mass, resulting in loss of active catalyst surface, so these

An example of a process for contacting a sulfuric acid process.

1-electrostatic dust collector, 2-rushing scrubber, 3-electric mist eliminator.. dry operation tower. 5-absorption tower, 6.7-heat exchanger. 8-converter, C-cooler. T-storage Bad

As a corresponding measure, the smelting furnace flue gas is cooled by the residual heat pot in the temperature range generated by the SO3, to prevent the increase of the useless SO3, after the dry dust removal, as shown in Figure 3-66. The leeches are cooled and dedusted to remove the so3 acid mist generated and passed through the acid mist electrostatic precipitator. Further, the water vapor is removed from the dry operation column having a concentrated sulfuric acid cycle, and the water is equilibrated to obtain a concentrated sulfuric acid of a suitable concentration, and then heated by a heat exchanger to pass through a V2O5 catalyst layer maintaining 700-750 K. The SO2 is converted to SO3, and then absorbed by concentrated sulfuric acid having a slightly lower concentration to obtain a concentrated sulfuric acid product. The method in which the absorbed gas is again passed through the converter is called a two-stage contact method, and a conversion rate of 99.5% or more can be obtained. When a higher concentration of SO2 gas is used, the production capacity is also high, and the final discharge can be also reduced. The concentration of SO2 in the gas.

On the other hand, in order to effectively utilize a low-concentration SO2 gas which cannot produce sulfuric acid, and to eliminate the smoke, various detoxification methods have been used. Generally referred to as flue gas desulfurization, the most common is the wet absorption process using a scrubber. Absorption is carried out using Ca(OH)2, or a CaCO3 slurry. Gypsum (CaSO4 - 2H20) is inexpensive and practical as a by-product. There is also a method of absorbing an aqueous solution of NaOH to produce by-products such as sodium sulfate or sodium sulfite, and a method of washing with nitrogen water to produce sulfuric acid, and further, using ZnO slurry, reduced aluminum sulfate, and citric acid as an absorbent. Method, etc., all of which are selected according to the actual situation.

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