Application of energy-saving technology in double-effect alcohol distillation

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The last edit to this post was made by Desert Fish on 2016-3-21 at 12:48. Preliminary Plan for the Technical Upgrade Project of ****** Technology Co., Ltd. – Application of Energy-Saving Techniques in Double-Effect Alcohol Distillation 1. Introduction 1. Current status of the dirty alcohol recovery process in the CMC production workshops of ****** Technology Co., Ltd.: The company has three CMC production workshops, with 3 sets of recovery towers installed at the east end of each workshop to recover the dirty alcohol produced there; in total, 9 recovery towers are available across the entire factory； Each tower is equipped with a distillation vessel; steam is used to heat this vessel, thereby driving the recovery tower to carry out the distillation of dirty alcohol ； Circulating water is used at the top of the tower to condense the alcohol vapor. The process used is relatively simple, but it has significant drawbacks such as high steam energy consumption, large amounts of circulating water required, and high production costs. 2. Main features of the energy-saving technology for double-effect differential pressure distillation: An additional high-pressure tower is added to work in conjunction with the existing 3 recovery towers. The vapor produced at the top of the high-pressure tower is used to heat these 3 recovery towers, thereby saving the steam required for distillation in them. At the same time, this allows the vapor generated by the high-pressure tower to be effectively condensed, reducing the amount of circulating water needed for vapor condensation. This system not only recovers all the latent heat and most of the sensible heat within the system to fully preheat the feed, but more importantly, it also significantly improves distillation efficiency, thereby achieving energy savings, increased production, and reduced production costs. This system features only 1 tower (a high-pressure tower) for discharging residual liquid, which reduces the risk of that liquid containing alcohol escaping; the alcohol recovery rate reaches 99.95%, thereby minimizing alcohol losses. 3. Effects of the technical upgrade: After the dual-efficiency energy-saving renovation, the system’s capacity to handle contaminated alcohol reaches 20 tons per hour, with an overall processing capacity of 480 tons per day, which is sufficient to meet the processing needs of the three workshops currently in use. It is expected to save 50,000 tons of steam per year. The upgraded process system features a computer-based automation monitoring system that enables computer-controlled management of the production process. This not only significantly reduces the workload of operators but also greatly improves the system’s ability for precise adjustments, thereby ensuring the stability and reliability of its operation and enhancing the company’s technological level. 4. Preliminary technical renovation plan: Based on the principles of smooth processes and convenient operation management, as well as the need to make full use of existing conditions, a suitable location will be selected among the three existing workshops. A new high-pressure tower, along with equipment such as reboilers, condensers, preheaters, reflux tanks, and pumps, will be installed. In total, 23 sets of new equipment will be added, along with corresponding pipelines, valves, electrical systems, etc. The three existing recovery towers will be utilized together to form a double-effect energy-saving distillation system. A new set of DCS control operating systems, along with associated instruments and automatic valves, has been added to improve the stable operation and regulatory functions of the distillation system. 5. Remove the original equipment from the other two workshops to be used as spares for future expansions. 6. After conducting statistics on other equipment such as heat exchangers in the original system, these devices were taken fully into consideration during the design of this system, with an effort to reuse them based on their specifications. 2 Technical basis and rationale for the technical renovation project 2.1 Basis and standards for preparing technical design documents · Code for Design of Building Water Supply and Drainage Systems GBJ15-88 · Code for Structural Design of Water Supply and Drainage Projects GB50069-2002 · Code for Design of Concrete Structures GB50010-2002 · Code for Design of Building Foundation GB50007-2002 · Code for Fire Protection Design of Buildings GBJ16-87 · Code for Design of Low-Voltage Power Distribution GB50054-95 · Code for Design of Relay Protection and Automatic Devices in Electrical Installations GB50062-92 · Standard for Lighting Design in Civil Buildings GBJ133-90 · Code for Grounding Design of Industrial and Civil Electrical Installations GBJ65-83 · Standard for Lighting Design in Industrial Enterprises GB50034-92 · Standard for Noise Levels at the Boundaries of Industrial Enterprises GB12348-90 · General Principles for the Layout Design of Petrochemical Process Units (SH3011-2000) · Code for Fire Protection Design of Petrochemical Enterprises (GB50160-1992) · Regulations on Safety Supervision of Pressure Vessels issued by the Quality and Technical Supervision Department (2009) · Shell and Tube Heat Exchangers GB151-1999 · Technical Requirements for the Manufacture of Steel Chemical Vessels HG20584-1998 · Steel Tower-Type Vessels JB/T4710-2005 · Provisions for the Structural Design of Steel Chemical Vessels HG20583-1998 2.2 Principles for engineering design and implementation During the engineering design and project implementation phases, the following principles are strictly followed: The process technology must be advanced and reliable; it should be scientifically integrated with existing process conditions to ensure that all design objectives are met after the technical renovation is completed. During the renovation process, existing equipment and installations should be made full use of to minimize construction costs. Meanwhile, with reasonable investment, the double-effect distillation system should achieve significant energy savings and reduced consumption, resulting in a steady decline in production and operating costs. In terms of the new process design and equipment, efforts are made to achieve high quality at low costs, seeking the best cost-performance ratio; the goal is to obtain greater benefits with minimal investment, ensuring that the project has advanced technical and economic specifications. The n process enables simple operation management, reduces the workload for operation and maintenance, and lowers maintenance costs. By adopting advanced and mature automation control technologies, it is ensured that the treatment efficiency, as well as the stability and reliability of operation, of the system after the technical renovation are at an industry-leading level. 3 Scope of the technical improvement project 3.1 Design scale The production capacity designed for this project is 480 tons per day of dirty alcohol, which corresponds to an average rate of 20,000 kg/h. Parameters of the dirty alcohol: Average concentration: 60–65% (v/v); Density of dirty alcohol: 0.897 kg/L. Composition of dirty alcohol: EtOH 65% (v/v), NaCl 4.1%; HOCH2COONa 1.5%; Water 29.4% (v/v), along with small amounts of CMC fiber impurities. pH level: 8–9. Temperature of dirty alcohol: 20°C. Quality specifications for the distilled alcohol: Average concentration: 80% (v/v); Temperature: 30°C. Recovery efficiency of distilled ethanol (EtOH): >99.95%. Steam consumption: 5400 + 5% kg/h. Designed operating range: 50%–120%. 4 Selection of distillation process 4.1 Selection of feed method: Based on actual characteristics such as the concentration of dirty alcohol and salt content, the preferred feed method is determined through technical comparisons – namely, a series feed process. Its main advantages are: a) it can effectively reduce the feed concentration in the high-pressure tower, thereby facilitating the control and adjustment of the alcohol content at the top of the tower and ensuring a more stable and reliable production process ； b. Effectively reduce the alcohol content in the residual liquid discharged from the system. 4.2 Selection of distillation process scheme: This technology employs a four-column, double-effect differential pressure distillation process. Steam is introduced into the high-pressure column to drive its operation; the high-pressure alcohol vapor generated there is then sent to the reboilers of the three atmospheric-pressure columns, thereby enabling those columns to function as well. At the same time, this vapor cools the alcohol vapor produced in the high-pressure column, which subsequently flows into the reflux tank ； The feeding method is in series: the raw material is preheated multiple times before entering the three atmospheric pressure towers. After some alcohol is distilled in these towers, the low-concentration alcohol mixture at the bottom of the towers is collected in an intermediate tank; it is then pumped and preheated once more before being sent to the high-pressure tower for further distillation. The residual liquid is discharged from the bottom of the high-pressure tower, with products being obtained from both towers simultaneously. The advantages of this solution are as follows: 1. The process flow is smooth and straightforward, with low energy consumption for the equipment and minimal maintenance requirements ； 2. It reduces the steam consumption of the three atmospheric pressure towers, thereby effectively lowering the steam energy consumption of the entire system ； 3. The latent heat released by the condensation of alcohol vapor is absorbed and used for the operation of the atmospheric pressure tower and the preheating of feed, thereby also reducing the amount of circulating water required. 4. The non-condensable gases generated during the distillation process are collected and removed by the exhaust gas collection tank, thereby improving the quality of the finished liquor. 5 Production System and Staffing: Upon completion of the technical upgrades for this project, the production system will continue to operate in accordance with the company’s existing procedures. The DCS control system for the new installations requires one operator per shift, as well as one overall manager, as shown in the table below. Companies can make adjustments based on their current workforce quotas; through consolidation and optimization, it is possible to avoid increasing new employment targets. Division of labor, production shifts (shifts/day), number of workers per shift (persons/shift), total number of team members (persons). Production workers: 314; Administrative and technical management staff: 111. 6 Key technical specifications (main criteria for acceptance): 6.1 Requirements for process documents: Must comply with 2.1 – Basis for preparation and relevant standards and specifications. 6.2 Requirements for process data: Raw alcohol, finished alcohol; Steam consumption in kg/h; Processing capacity in kg/h; Concentration (v/v); Output in kg/h; Concentration (v/v): 20,000; 65%; 1624; 180%; 5,400 ± 5%. Remarks. 6.3 Requirements for equipment manufacturing: Must comply with relevant **standards and specifications, and a product qualification certificate recognized by the **relevant authorities must be provided. 6.4 Installation requirements: Relevant installation drawings must be provided, the installation must comply with relevant **installation specifications, and it must pass the installation inspection by the **relevant authorities. 6.5 Commissioning and training: Once the installation is complete and commissioning is possible, process operation manuals and procedures must be provided to the client, and technical training and briefings must be given to the company’s relevant personnel. 6.6 Project management objectives: Ensure compliance with the start and completion dates specified in the contract, and strengthen safety measures during the project construction process to prevent any safety incidents. 7 List of Main Process Equipment (Process Equipment Table)