Problems with three-column distillation

The pre-tower is primarily used to remove some light components, such as dimethyl ether, methyl formate, and syngas dissolved in crude methanol, among others. Setting up three-column distillation is mainly to make rational use of energy.

In our process, a recovery tower is installed after three-stage distillation; the liquid from the bottom of this recovery tower is sent to a partial oxidation stripping tower. The steam generated in this stripping process can carry away some waste, which is then added to the feed gas and sent to the conversion furnace.

The purpose of methanol distillation is to separate methanol from impurities such as water and organic substances, in order to produce high-quality purified methanol. A two-column process refers to a plant that consists only of a pre-column and a main distillation column, while a three-column process involves a pre-column, a pressurized column, and a atmospheric column. The three-column process essentially divides the main distillation column in the two-column process into a pressurized column and an atmospheric column. In both two-column and three-column processes, the role of the pre-column is to remove gases and low-boiling-point impurities dissolved in crude methanol, while the function of the other columns is to remove water and higher-boiling components from methanol. The key to the process design of the methanol pressurized tower and atmospheric tower is the integration of material and heat. In the methanol three-column distillation process, energy is made full use of by using the methanol vapor drawn from the top of the pressurized column as a heat source for the reboiler of the atmospheric pressure column. The wastewater from the atmospheric pressure tower depends on what is used as raw material for methanol production.

Yes, that’s correct. The pre-tower is used to remove light components, and it operates in full reflux mode. The pressure tower is used to remove heavy components such as ethanol, and the atmospheric pressure tower also serves to remove heavy components

In addition to removing light components, the pre-column can also separate heavier components such as alkanes that form azeotropes with methanol, but extraction water must be added.

Wastewater discharge requirements specify that the methanol content must be less than 100 PPm

The overhead distillates from the demethanization tower mainly include dimethyl ether, formaldehyde, methylamines, acetaldehyde, etc. Use a pressure tower to extract some of the qualified products ； Use an atmospheric pressure column to remove the heavy components and obtain qualified products ； Make full use of heat sources to reduce production cost expenses. The emission standard is generally not higher than 100 ppm

The pre-tower is used to remove light components, mainly including dimethyl ether, formaldehyde, methylamines, acetaldehyde, etc. The pressure tower is used to remove heavy components, while also obtaining some qualified product ； Using a atmospheric pressure column also enables the removal of Reorganization components and the production of qualified products ； It is divided into a pressurized tower and an atmospheric pressure tower, primarily to make full use of heat sources and reduce production costs. Wastewater contains trace amounts of methanol, with standards generally not exceeding 100 ppm

The pre-tower is used to remove light components, mainly including dimethyl ether, formaldehyde, methylamines, acetaldehyde, etc. The pressurized tower is primarily used to make full use of heat sources in order to reduce production costs, while also obtaining some qualified products ； Using a atmospheric pressure column also allows for the recovery of some products, along with some heavy components or fusel oils. The recovery tower is primarily used to recover organic substances from the tower liquid, ensuring that the emissions meet the required standards.

1. What substances in crude methanol are mainly removed at the top of the pre-distillation tower? The main purpose is to remove light components, most of which are alkanes. 2. What are the functions of the pressurized tower and the atmospheric pressure tower, and why are they necessary? Function ； Produce high-purity methanol, remove heavy components, and bring the wastewater up to standard. The purpose of installing a pressurized tower and an atmospheric tower is to save energy, increase production, and improve product quality, as the heat source for the atmospheric tower comes from the overhead product of the pressurized tower. 3. What substances are contained in the wastewater from the bottom of an atmospheric pressure tower? What are the main substances it contains, and what are their approximate concentrations? **What are the discharge standards required for this water? It mainly contains water, methanol, and fusel oils; the water content is 99.8%, while the alcohol content is less than 0.2%. **There are no specific regulations regarding emissions, and the standards should be those for ammonia nitrogen and COD as stipulated by environmental protection rules.**

The impurities in crude methanol can be divided into two main categories: one category includes dimethyl ether, methyl formate, etc., which have boiling points lower than that of methanol； Another category includes ethanol, propanol, water, butanol, etc., whose boiling points are higher than that of methanol. Substances with a boiling point lower than that of methanol are removed in the pre-tower, while substances with a boiling point higher than that of methanol are removed in the pressurized tower and the atmospheric pressure tower.

1. At the top of the pre-distillation tower, the light components in crude methanol are primarily removed; these components mainly include alkanes, dimethyl ether, methyl formate, as well as syngas dissolved in the crude methanol. 2. The functions of the pressurized tower and the atmospheric tower are ； Produce high-purity methanol, remove heavy components, and bring the wastewater up to standard. The purpose of installing a pressurized tower and an atmospheric tower is to save energy, increase production, and improve product quality, as the heat source for the atmospheric tower comes from the overhead product of the pressurized tower. 3. Bottom wastewater from atmospheric pressure tower ； It mainly contains water, methanol, and fusel oils; the water content is 99.8%, while the alcohol content is less than 0.2%. **There are no specific regulations regarding emissions, and the standards should be those for ammonia nitrogen and COD as stipulated by environmental protection rules.**