Could someone explain thermal coupled distillation in the process of alcohol distillation?

The question is rather general; to put it simply: the distillation system uses a three-tank heat integration setup, with tower C1 being the mash tower, tower C2 being the first distillation tower, and tower C3 being the second distillation tower. The process involves the mash flowing into the top of tower C1 after exchanging heat with the condenser at the top of that tower; some of the vapor containing aldehydes is condensed in the upper part of tower C1, while the liquid phase, containing about 48% alcohol, is sent to tower C3. Mash with a concentration of 8–10% is taken from a certain point and sent to tower C2 after exchanging heat with the liquid at the bottom of that tower; the waste mash is then removed from the bottom of tower C1； The C2 tower top yields an azeotropic mixture of alcohol, while the bottom of the tower contains water ； The top of Tower C3 yields an azeotropic mixture of alcohol, while the sampling line produces fusel oils; the bottom of the tower contains water, which exchanges heat with the material fed into the tower. The resulting azeotropic alcohol composition is fed into the dehydration unit to produce fuel ethanol. Operating pressure: C1 micro-vacuum, reboiler temperature around 80 degrees ； C2 at slightly positive pressure, tower top temperature around 93 degrees ； The pressure at the top of Tower C3 is 5.8 kg/cm2, and the temperature at the top is 128 degrees. Thermal integration flow: The bottom of tower C3 is heated by steam; the top of this tower is thermally integrated with the bottom of tower C2, and the top of tower C2 is thermally integrated with the bottom of tower C1. The feed is preheated at the top of tower C1 before being condensed. In several heat-integrated heat exchangers, due to low temperature differences and dirty fluids, forced circulation is used for heat exchange in the tube side. The above is a simplified process for fuel ethanol; if ethanol suitable for use is to be produced, aldehyde and methanol removal units need to be added. This is a brief description provided solely for informational purposes.

In the alcohol production process, the distillation step plays a crucial role; it not only determines the quality of the final product but also controls the yield and consumption of the product. In recent years, significant progress has been made in high-efficiency distillation technology. Alcohol manufacturers abroad have developed vacuum distillation techniques, which have improved product quality and reduced energy consumption, thereby greatly enhancing the level of alcohol production technology. Technical principles and process flow: This technology determines an appropriate number of distillation units, ensuring the effective removal of various impurities and achieving the highest possible product quality and yield. It utilizes multi-column variable-pressure operation to implement a heat-coupled distillation process, thereby minimizing the amount of steam and cooling water required ； By cleverly combining high-efficiency packed tower technology with specialized tray technology, the separation capacity of the distillation unit as well as the operability of the equipment used for side-stream extraction are greatly improved. The process flow of high-purity alcohol differential pressure distillation technology consists of the following unit equipment: 1. Crude distillation tower, 2. Distillation tower, 3. Aldehyde removal tower, 4. Methanol removal tower, 5. Recovery tower. The fermented mash is passed through a crude distillation column to remove solid particles, heavy components, and most of the water. The waste mash is sent to the DDGS production facility, while the crude liquor obtained at the top of the column is sent to an aldehyde removal column to eliminate aldehydes and esters. The light liquor obtained at the bottom of the column is then sent to the main distillation column to remove impurities such as fusel oils. The high-concentration alcohol obtained from the side streams is sent to a methanol removal column to remove impurities like methanol, resulting in a high-purity alcohol product. The fusel oil fraction is sent to a recovery column for purification and is sold as a by-product. This technology is the first of its kind in China and has reached international advanced levels. The technical specifications are as follows: Product standard: food-grade alcohol ； Product yield: Alcohol distillation yield is greater than 99%, with the yield of high-quality alcohol exceeding 96% ； Utilities consumption: Steam (0.4 MPa) 3.4 tons per ton of product ； Circulating water: 130 tons (circulation volume)/ton of product ； Electricity: 132 kWh per ton of product. Market feasibility: At present, with the **improvement of standards for the quality of edible alcohol products and increasing market competition, most alcohol manufacturers in China are in urgent need of technological upgrades and advancements in order to enhance product quality, reduce energy consumption, and thus boost the competitiveness of their alcohol products in the market. Furthermore, pure alcohol as a fuel boasts advantages such as a high calorific value and clean combustion; as a result, there will be strong market demand for gasoline-alcohol products, which will hold significant importance for environmental protection in our country. To improve the market and technical standards of China’s alcohol industry, the Petrochemical Technology Development Center at Tianjin University utilized advanced thermocouples and technologies, precision distillation techniques, as well as complex process simulation methods to develop a software package for differential pressure distillation of high-purity alcohol. This software package was successfully applied in the 140,000-ton per year production facility for high-purity alcohol operated by Jinyu Company of China Resources Group in Heilongjiang.

The book \"Modern Distillation Technology\" discusses coupled distillation, and it’s necessary to get in touch