Seeking advice on the processes for burning high-chlorine substances and recovering hydrochloric acid

What is your high-chlorine substance? ? At least give the ingredients or something; otherwise, who can answer you? ? When incinerating general medical waste, high levels of calcium and chlorine are often encountered; however, hydrochloric acid is not recovered. For the incineration of chlorine-containing waste, the choice of process depends largely on the metal elements present in those chlorides. After incineration, what remains are metal oxide powders, and the type of furnace to be used as well as the temperature control required are all related to these chlorides and oxides. Without knowing these details, no one can help you.

The components are mainly trichloroethylene, carbon tetrachloride, and trichloroethane, as well as some substances containing bromine and fluorine such as dibromoethane and bromofluorobenzene

The spray roasting process can be used for treatment. In terms of composition, the waste does not contain metal ions, which eliminates many complications. Halogenated organic compounds can be directly roasted at high temperatures, and hydrochloric acid can be recovered through water absorption; the organic compounds are burned away while the halogens can be completely absorbed by water. However, it should be noted that if the waste contains a small amount of metal ions and this is overlooked by the owner, it will have a significant impact on the process – the roasting furnace will suffer from scaling due to metal oxides, affecting its long-term stable operation. It can only be said that dealing with such waste is quite challenging. The difficulties lie in the process parameters and procedures, as well as in the selection of equipment and machinery. In other words, the challenges are related to mechanical components and equipment. The acid recovered from the product at the bottom of the absorption tower contains hydrochloric acid, hydrofluoric acid, and hydrobromic acid, and the temperature is as high as 80–90°C. Pumps, fans, and other equipment require special materials and are extremely expensive; thus, the investment involved is significant. To the best of my knowledge, there are no mature suppliers offering complete sets of such equipment in China, and it’s likely the same in other countries as well. The person asking this question might want to conduct some research. . Referencing the hydrochloric acid recovery processes used in carbon steel pickling lines of steel metallurgy enterprises, as well as the hydrofluoric acid recovery processes used in stainless steel pickling lines, for treating waste at a rate of ~5 tons per hour, the total investment for such facilities ranges from 60 million to 100 million yuan, while the operating cost is between 200 and 500 yuan per ton of waste liquid (depending on the owner’s costs for gaseous fuels such as coal gas or natural gas). Both the investment and operating costs are quite high; it is recommended to conduct a detailed feasibility study. . .

Hero! Could you provide specific process diagrams and temperature control parameters for each stage? ! I am extremely grateful!

I can’t provide it, as no company has a spray roasting process suitable for your type of material. There’s plenty of information available online on processes for recycling waste hydrochloric acid from pickling lines, including PPTs and drawings; you can use that as a reference.

{:3_55:} It contains fluorine. . . Nothing seems easy to handle, right?

May I ask, how should waste liquid containing metals such as Mo, Cu, and Cr be treated?

The metal ions in the waste liquid are oxidized to metal oxides in the oxidative atmosphere of the roasting furnace, and then discharged from the bottom of the furnace. The biggest challenge in this process is first and foremost controlling the oxidative atmosphere inside the furnace. Metal ion oxides exist in different oxidation states; for example, Fe2+ present in the acid waste from carbon steel pickling forms Fe2O3, which represents complete oxidation with Fe in the +3 state. If the degree of oxidation is insufficient, FeO or Fe3O4 is formed, with Fe in the +2 state. Other metal ions also have oxides in various oxidation states to varying degrees. Therefore, it is crucial to select an appropriate oxidative atmosphere, and this is a technical secret kept hidden by foreign patent holders. Secondly, different salts (such as NaCl and FeCl) have different melting points, and these differences make it easy for them to stick to the furnace walls. For example, the melting point of FeCl2 is 670°C, while that of NaCl is well over a thousand degrees. If the furnace temperature is not properly controlled, FeCl2 will melt before it can be converted into Fe2O3. Since there is a large amount of oxide powder in the furnace, this is similar to flour coming into contact with water vapor – wet substances sticking to dry ones, resulting in clumps that adhere to the furnace walls. If these clumps become too heavy, they may fall to the bottom of the furnace, potentially damaging something in their path. Therefore, the furnace temperature is set based on the salt with the lowest melting point in order to avoid clumping. However, if this temperature is too low, certain salts will not decompose, making the treatment of such waste liquids extremely difficult. A great deal of preliminary calculation and comparison are required; many factors can be calculated. For instance, if the furnace temperature is set at 650°C, then NaCl will not decompose at this temperature and thus will not turn into Na2O. The powdered products will then consist of Fe2O3 and NaCl. Controlling the proportions of oxides with different valence states is even more challenging; any mistake in calculations or carelessness in design and operation can lead to serious problems. . The common treatment process abroad is a combined approach, which involves preprocessing the waste liquid by adding flocculants and using sedimentation and filtration to remove certain metal ions first (all three ions you mentioned can be pre-treated in this way). After that, roasting is used for further treatment. A single treatment process may not always be effective, which is why such processes are often kept confidential, and it’s difficult to find technical information about them available publicly. Therefore, worldwide, there are few mature treatment processes for waste acid solutions containing multiple metal ions; such processes are limited to a few specific types of waste acids and liquids, and it has taken hundreds of industrial-scale installations to develop them to maturity.