阅读说明：本技术 一种用于精馏经济优化的智能控制算法 (Intelligent control algorithm for economic optimization of rectification ) 是由 唐斌 宋太沧 于 2019-10-22 设计创作，主要内容包括：一种用于精馏经济优化的智能控制算法,包括如下步骤：(1)以年度总费用为目标函数,保持待优化变量外的其它变量不变,以待优化变量值为中心改变待优化变量值,模拟计算目标函数值；(2)通过T-xy相图确定两塔的操作压力；由简捷精馏设计的估算值作为初始值计算两塔回流比；使用“Design Specs/Vary”功能设计塔底物流流率直到满足两塔底产品质量的规定值；(3)在约束条件范围内找到使目标函数取得极小值的待优化变量值；(4)不断重复上述步骤依次迭代优化,直到取得使目标函数最小的设计变量组。本发明所述的用于精馏经济优化的智能控制算法,是基于序贯迭代软件法,应用到变压精馏的经济、准确优化过程中,可以精准精馏,提高了产品的质量与产量。(An intelligent control algorithm for economic optimization of rectification, comprising the steps of: (1) taking the total annual cost as an objective function, keeping other variables except the variable to be optimized unchanged, changing the variable value to be optimized by taking the variable value to be optimized as a center, and simulating and calculating the objective function value; (2) determining the operating pressure of the two towers through a T-xy phase diagram; calculating the reflux ratio of the two towers by taking the estimated value of the simple rectification design as an initial value; designing the flow rate of the tower bottom material flow by using a Design Specs/Vary function until the specified value of the quality of two tower bottom products is met; (3) finding a variable value to be optimized which enables the target function to obtain a minimum value within the range of the constraint condition; (4) and continuously repeating the steps and sequentially iterating and optimizing until a design variable group which minimizes the objective function is obtained. The intelligent control algorithm for the economic optimization of rectification is based on a sequential iteration software method, is applied to the economic and accurate optimization process of variable-pressure rectification, can accurately rectify and improve the quality and the yield of products.)

1. An intelligent control algorithm for economic optimization of rectification, comprising the steps of:

(1) taking the total annual cost as an objective function, keeping other variables except the variable to be optimized unchanged, changing the variable value to be optimized by taking the variable value to be optimized as a center, and simulating and calculating the objective function value;

(2) determining the operating pressure of the two towers through a T-xy phase diagram; calculating the reflux ratio of the two towers by taking the estimated value of the simple rectification design as an initial value; designing the flow rate of the tower bottom material flow by using a Design Specs/Vary function until the specified value of the quality of two tower bottom products is met;

(3) finding a variable value to be optimized which enables the target function to obtain a minimum value within the range of the constraint condition;

(4) and continuously repeating the steps and sequentially iterating and optimizing until a design variable group which minimizes the objective function is obtained.

2. The intelligent control algorithm for economic optimization of rectification according to claim 1, wherein the variable values to be optimized include the number of column one theoretical plates and the number of column two theoretical plates of the outermost iteration loop.

3. The intelligent control algorithm for economic optimization of rectification of claim 2, wherein the variable values to be optimized further comprise a column one feed position and a column two feed position of an inner iteration loop.

4. The intelligent control algorithm for economic optimization of rectification according to claim 3, wherein the variable values to be optimized further comprise a recycle stream feed position, a column reflux ratio, a column two reflux ratio.

5. The intelligent control algorithm for economic optimization of rectification according to claim 4, wherein the step (3) comprises: the recycle stream feed position, the column one feed position and the column two feed position of the inner iterative loop are changed until the objective function is minimum.

6. The intelligent control algorithm for economic optimization of rectification according to claim 4, wherein the step (3) comprises: and changing the number of the first theoretical plate and the second theoretical plate of the outermost iteration loop until the objective function is minimum.

7. The intelligent control algorithm for economic optimization of rectification according to claim 4, wherein the step (4) comprises: if the objective function can be continuously reduced by changing a certain variable to be optimized, returning to the second step to continuously circulate and iterate optimization; and if the objective function cannot be reduced continuously, obtaining the optimal number of the theoretical plates of the first tower and the second tower of the outermost layer iterative cycle, the feeding positions of the first tower and the second tower of the inner layer iterative cycle, the feeding position of the recycle stream, the reflux ratio of the first tower and the reflux ratio of the second tower.

Technical Field

The invention belongs to the technical field of intelligent control algorithms, and particularly relates to an intelligent control algorithm for economic optimization of rectification.

Background

In the industrial process of chemical industry, pharmacy, petroleum processing and the like, azeotropic mixtures which are difficult to separate by using common rectification technology are easy to generate. Such as: methanol-dimethyl carbonate azeotropic mixture is generated in the process of producing dimethyl carbonate; ethanol and water azeotropic mixtures are often produced in biofuel production and wine brewing processes; methanol-tetrahydrofuran azeotrope is produced during the production of steroid drugs. In recent years, problems of environment, resources, energy sources and the like are continuously developed, and the efficient separation of the azeotrope not only saves energy and reduces emission, but also can realize the resource recycling of valuable organic matters. The pressure swing distillation is widely applied to the separation of a pressure sensitive azeotropic system due to the advantages that the third component is not introduced, the high-purity product is easy to obtain, the energy conservation is easy to realize by heat integration, and the like.

According to statistics, the energy consumption of the rectification process accounts for 10-15% of the total energy consumption of a factory, and the energy conservation, the reinforcement, the optimization and the design of the rectification related process are concerned. The pressure swing distillation adopts the combined operation of two distillation towers under different pressures, and the steam at the top of the high-pressure tower can be used as the heat source of a reboiler of the low-pressure tower, thereby realizing the design of the heat integration process scheme. In recent years, the selection and economic optimization of the energy-saving scheme of the pressure swing distillation process become research hotspots.

The economic optimization of the pressure swing distillation relates to optimization variables such as the number of tower plates, the feeding position, the reflux ratio, the pressure and the like of a distillation tower, and the process design and optimization are usually realized by adopting a sequential iteration method and a heuristic optimization method based on a flow simulator. The heuristic optimization method has a simpler optimization process, but has stronger randomness and is difficult to ensure better optimization and design. The sequential iteration method is characterized in that TAC (total annual cost) is calculated by operating a process simulator Aspen Plus by continuously changing variables to be optimized, the workload is large, and the iterative optimization process is particularly complicated.

The Chinese patent application No. CN201020671302.9 discloses a methanol thermal coupling multi-effect rectification method and a device, which aim at rectification in methanol chemical separation engineering and solve the problems of reducing energy consumption and reducing three-waste emission, and do not optimize and design an intelligent control algorithm for rectification economic optimization.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects, the invention aims to provide an intelligent control algorithm for rectifying economic optimization, which is based on a sequential iteration software method, is applied to the economic and accurate optimization process of variable-pressure rectification, can be used for rectifying accurately, improves the quality and the yield of products, obtains good economic benefit, can reduce energy consumption, obtains better environmental protection benefit and has wide application prospect.

The purpose of the invention is realized by the following technical scheme:

an intelligent control algorithm for economic optimization of rectification, comprising the steps of:

(1) taking the total annual cost as an objective function, keeping other variables except the variable to be optimized unchanged, changing the variable value to be optimized by taking the variable value to be optimized as a center, and simulating and calculating the objective function value;

(2) determining the operating pressure of the two towers through a T-xy phase diagram; calculating the reflux ratio of the two towers by taking the estimated value of the simple rectification design as an initial value; designing the flow rate of the tower bottom material flow by using a Design Specs/Vary function until the specified value of the quality of two tower bottom products is met;

(3) finding a variable value to be optimized which enables the target function to obtain a minimum value within the range of the constraint condition;

(4) and continuously repeating the steps and sequentially iterating and optimizing until a design variable group which minimizes the objective function is obtained.

The intelligent control algorithm for the economic optimization of the rectification is based on a sequential iteration method, is easy to operate, has high reliability of an optimization result, and is applied to the economic and accurate optimization process of the variable-pressure rectification. The core of the intelligent control algorithm for economic optimization of rectification is as follows: taking the total annual cost as an objective function, keeping other variables except the variable to be optimized unchanged, changing the variable value to be optimized by taking the variable value to be optimized as a center, simulating and calculating the objective function value, finding the variable value to be optimized which enables the objective function to obtain a minimum value within the range of constraint conditions, and continuously repeating the steps to sequentially perform iterative optimization until a design variable group which enables the objective function to be minimum is obtained.

Further, in the above intelligent control algorithm for economic optimization of rectification, the variable value to be optimized includes the number of first theoretical plates and the number of second theoretical plates of the outermost iteration loop.

Further, in the above intelligent control algorithm for economic optimization of rectification, the variable value to be optimized further includes a first feeding position and a second feeding position of the inner layer iterative loop.

Further, in the above intelligent control algorithm for economic optimization of rectification, the variable value to be optimized further includes a recycle stream feed position, a tower reflux ratio, and a tower two reflux ratio.

The total annual cost is taken as a target function, under the condition that other conditions are not changed, the increase of the first tower reflux ratio and the second tower reflux ratio is beneficial to the improvement of the precision and the purity of the product, but the larger the reflux ratio is, the larger the heat load of the tower kettle reboiler is, the higher the energy consumption is, and the lowest corresponding reflux ratio of the energy consumption is determined under the condition of meeting the requirements of the precision and the purity of the product. And determining the feeding positions of the two towers and the feeding position of the circulating material according to the minimum value of the objective function within the range of the constraint condition. Under other conditions, the separation effect is better when the number of the theoretical plates of the tower is larger, but the equipment investment cost is increased along with the increase of the number of the theoretical plates, and the number of the theoretical plates of the tower has larger influence on the optimal values of the feeding position and the reflux ratio, so that the number of the plates is the outermost optimization parameter of the circulation iteration. The operating pressure of the two towers is determined by changing the azeotropic composition, the steam temperature and the temperature requirement of a cooling medium and the like through a t-x-y phase diagram in the sequential iterative optimization process.

Further, the above intelligent control algorithm for economic optimization of rectification, said step (3) comprising: the recycle stream feed position, the column one feed position and the column two feed position of the inner iterative loop are changed until the objective function is minimum.

Further, the above intelligent control algorithm for economic optimization of rectification, said step (3) comprising: and changing the number of the first theoretical plate and the second theoretical plate of the outermost iteration loop until the objective function is minimum.

Further, the above intelligent control algorithm for economic optimization of rectification, said step (4) comprising: if the objective function can be continuously reduced by changing a certain variable to be optimized, returning to the second step to continuously circulate and iterate optimization; and if the objective function cannot be reduced continuously, obtaining the optimal number of the theoretical plates of the first tower and the second tower of the outermost layer iterative cycle, the feeding positions of the first tower and the second tower of the inner layer iterative cycle, the feeding position of the recycle stream, the reflux ratio of the first tower and the reflux ratio of the second tower.

Compared with the prior art, the invention has the following beneficial effects:

(1) the intelligent control algorithm for the economic optimization of the rectification is based on a sequential iteration method, is easy to operate, has high reliability of an optimization result, and is applied to the economic and accurate optimization process of the variable-pressure rectification;

(2) the intelligent control algorithm for economic optimization of rectification disclosed by the invention is reasonable in setting and good in effect, can be used for rectifying accurately, improving the quality and yield of products, obtaining good economic benefits, reducing energy consumption, obtaining good environmental protection benefits and having wide application prospect.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to specific embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The following embodiments provide an intelligent control algorithm for economic optimization of rectification, and the variable values to be optimized comprise the number of theoretical plates of the first tower and the second tower of the outermost iterative cycle, the feed positions of the first tower and the second tower of the inner iterative cycle, the feed positions of the recycle streams, the reflux ratio of the first tower and the reflux ratio of the second tower.