Treatment plan for wastewater containing sulfuric acid an

Is it relatively pure sulfuric acid? How about considering ion exchange? Reduction and reuse of wastewater. Some experiments can be conducted, and then a plan can be evaluated.

There are many options available, such as ammonia evaporation with the addition of alkali, or multi-effect evaporation – alarm lights; at such high concentrations, it is better to carry out recovery. But the solution depends on the circumstances. What is the daily processing capacity? What’s the temperature? Does it contain sodium salts and other impurities? Furthermore, does your factory use concentrated ammonia water (or liquid ammonia)?

Lime is added, ammonia gas is distilled off, and calcium sulfate precipitates upon cooling.

It is highly discouraged to directly add (slaked) lime (milk) to ammonium-containing wastewater and then evaporate the ammonia. The solubility of calcium sulfate in water is very low, and it decreases as the temperature rises. Therefore, pre-treated ammonia water, even after the calcium sulfate precipitate has been removed and it is fed into the distillation column (ammonia distillation tower), will still cause scaling that is extremely difficult to remove at the bottom of the distillation column, and in severe cases the entire column can become clogged.

The treatment of this type of sulfuric acid an is a rather complicated issue. Simple treatments, such as the use of lime as mentioned above, result in the formation of ammonia, which cannot be discharged directly as it affects the ammonia nitrogen levels in the wastewater. It is recommended to consider using three-effect evaporation to concentrate and recover the sulfuric acid an; although the cost of steam used in this process is high, it allows for a complete elimination of ammonia nitrogen from the wastewater.

If there are impurities, consider first how to remove them

After treatment with lime, ammonia is recovered.

The sulfuric acid AN in our plant is treated using double-effect vacuum concentration crystallization, with a processing capacity of 40 tons per hour.

It is recommended to use the method of concentrating and recovering sulfuric acid. In our plant, the concentration of ammonium sulfate waste liquid is much lower than that specified in the document; nevertheless, we still concentrate it first before proceeding with crystallization to recover ammonium sulfate. It is important to pay attention to the further treatment of the waste liquid resulting from secondary condensation (which contains ammonia nitrogen and other impurities). Only in this way can environmental standards be met. If the sulfur-ammonium wet crystals can be reused, it is also possible to consider refining them after dissolving them in a solution by adding a filter aid – all of this is done to make things more economical. This post was last edited by eboy3065 on 2009-3-6 17:11]

Our former company also had such wastewater, several hundred tons per day; sulfuric acid an was recovered through distillation and concentration for resale, with very good results

If it contains only 10% sulfuric acid an, it can be evaporated and concentrated using an evaporator to be used as fertilizer……

This is a post with great value for discussion. It seems that everyone prefers multi-effect evaporation, and I agree as well, provided there are no other impurities that precipitate earlier than sulfuric acid. However, such high-salinity wastewater is often the mother liquor remaining after the crystallization of some high-value organic compounds. If multi-effect evaporation is carried out again, must the impurities (high-value organic compounds) be crystallized first, causing scaling on the surfaces of the heat exchangers and evaporators? Of course, the method of external circulation with seeding can be used to recover high-value organic substances. It would be great to be able to do that, but it would require a significant increase in energy consumption and investment. Another alternative is to make full use of the fact that the solubility of some high-value organic compounds (the target products) changes significantly with pH; by adjusting the pH of the solution, it is possible to prevent the target products from precipitating during concentration, after which multi-effect evaporation can be used for concentration. But for salts like sulfuric acid an, only acid can be added to lower the pH; alkali cannot be added to raise it. However, lowering the pH value may cause equipment corrosion. Furthermore, the heat utilization efficiency of multi-effect evaporation systems with fewer than six effects is very low, with a water production ratio ranging from 2 to 4. If our membrane-based multi-stage multi-effect evaporation technology is used, the concentration can be increased from 7–10% to 30–35%, with a water production ratio ranging between 4 and 8. Normal-pressure steam is utilized; there is no need for high temperature, high pressure, negative pressure, or vacuum conditions, and thus no corrosion issues arise. Then, the sulfuric acid an solid salt is produced using a conventional single-effect evaporation-crystallizer. The pH can be adjusted between membrane evaporation and conventional evaporators to crystallize and recover high-value organic compounds. It should be noted that the secondary steam from the single-effect evaporation-crystallizer can be used for a membrane-based multi-stage multi-effect evaporation process, thereby eliminating the need for an additional external heating source in such membrane processes.

In addition to the evaporation concentration method, membrane separation can be considered for the recovery of sulfuric acid an.

Generally, the recovery of sulfuric acid AN is mostly carried out through evaporation and crystallization, a method that results in low pollution. However, when considering ammonia nitrogen levels, separation by gas-liquid entrainment must be strictly controlled; some degree of entrainment usually occurs, leading to non-compliant levels that require further treatment. This means that the issue of ammonia nitrogen treatment needs to be taken into account during the evaporation process. Considering that energy conservation generally favors multi-effect systems, I personally highly recommend two-effect evaporation with a heat pump; a steam-jet heat pump is a specialized device used to increase the pressure of low-pressure steam. The principle involves using high-pressure steam (driving steam) to generate a high-speed steam stream through the nozzle of a steam-jet heat pump; this stream is used to draw in low-pressure steam or flash vapor, raising its pressure and temperature, while simultaneously reducing the pressure and temperature of the high-pressure steam. This increases the pressure and temperature of the low-pressure steam, thereby generating the parameters required for the process, which are then supplied from the heat pump for use. The low-pressure steam that could not be utilized before is now put to use, achieving energy savings. In fact, the energy-saving effect of a dual-effect system with a heat pump is almost on par with that of a triple-effect system, yet the investment required for the equipment is much lower, and its operation is also relatively stable. It's just my personal opinion; I hope we can exchange ideas

There is another relatively reasonable solution for your reference: Lime is converted into lime slurry using a slaking machine, and this slurry is added to sulfuric acid AN wastewater. The ammonia gas generated is absorbed by water to produce ammonia water for internal use. The resulting neutralization solution is then pumped into a steam ammoxidation tower for ammonia removal; the ammonia-rich liquid obtained from this process is further used for ammonia production. The slurry that has undergone successful ammonia removal is subjected to plate and frame filtration to yield gypsum, which can be sold. This process is continuous, has a high processing capacity, and is easy to operate. The ammonia produced can be used internally, while the gypsum can be sold externally; it is therefore more feasible than concentrating and recovering sulfuric acid AN. It should be noted that concentrating sulfuric acid AN requires high-quality materials for the equipment. Sulfuric acid An is not produced industrially by concentration.

Membrane separation for the recovery of sulfuric acid AN – what are the investment and operating costs? Could you provide more details, or include contact information? I’m facing this same issue right now

Will there be industrial applications for it?