(1) Technical scope of application

This technology is mainly used for the optimization of production process systems in the chemical industry.

(2) Technical principles (transformation content)

① Technical introduction

Use the advanced process control optimization system (APC system for short) to embed the existing production device control system to optimize the operation of the device, control the flow of materials, and achieve accurate control, thereby achieving stable product quality. In addition to making full use of the existing production system, the system has newly installed some instruments and meters, such as flow meters and on-site sampling and analysis instruments and equipment for online monitoring of material compositions. The system covers advanced control systems for seven key systems including hydrogenation reactor, water separation column, TDA rectification column, phosgene synthesis reactor, phosgenation reaction system, chlorobenzene recovery column, and refrigerator.

② Energy saving principles

The APC system used in this project can comprehensively apply chemical engineering technology, computer application technology and automatic control technology to implement advanced computer control and optimization operations for the TDI production process, give full play to the inherent potential of the equipment, and achieve high economic benefits of the device with low energy consumption, low cost consumption and high output.

The TDI device adopts DMC control theory. The advanced control system consists of seven parts, of which the controller is the core, and the soft measurement instrument and Lims data input provide corresponding data support for the controller respectively.

The architecture of the entire control system can be divided into three levels: DCS layer, communication layer and upper computer layer. The DCS layer is the DeltaV system used by the device; the middle communication layer is composed of Emerson's OPC interface and Aspen's Cimio for OPC; the upper computer provides a running platform for the controller software and a monitoring interface for the engineer, and the operator monitors the entire device through the operating station.

According to the device's process characteristics, operators can use it to operate the controller through the controller operation interface developed on DCS. In order to provide continuous quality data to the controller, the project also developed multiple soft meters as controlled variables for the controller.

A DCS laboratory data entry window is also set up in the APC system to correct the accuracy of soft instruments in real time. In addition, on the basis of advanced control, an automatic lifting and lowering load system for the device has been developed. It can automatically change the setting values of relevant variables according to changes in the feed volume. The operator only needs to input the target load value to achieve smooth and accurate The purpose of lifting and lowering is achieved, with less fluctuations on the device, reduced uncertain factors for human operation, and reduced the work intensity of the operator.

(3) Application cases

Advanced control project of TDI unit of Shanghai BASF Polyurethane Co., Ltd.

1) Implementation content and cycle: The advanced control (APC) system comprehensively applies chemical engineering technology, computer application technology and automatic control technology, and the system is directly embedded in the DCS system to achieve seamless connection with the basic control loop. Advanced computer control and optimization operations are used in the production process to give full play to the inherent potential of the equipment. After the advanced control (APC) system is put into use, steam consumption in TDI production has been significantly reduced, and energy use optimization has been achieved. The implementation cycle is 1 year and August.

2) Energy conservation and emission reduction effect and investment payback period: According to the unit consumption method, before the project implementation (taking the average values of 2017, 2018 and 2019), the unit consumption and output were 458kgce/t and 165576t respectively.

Then the energy saving amount of this project =(458kgce/t-441kgce/t)*165576t=2815tce。

Therefore, the energy saving amount of this project is 2815 tons of standard coal.

According to the audit results, the project investment amount is 9.2082 million yuan. The project reviewed the energy conservation amount is 2815tce, and the energy involved includes multiple types such as steam, electricity, desalted water, compressed air and nitrogen. The temporary calculation is based on 2000 yuan per ton of standard coal, and the annual cost savings are 5.63 million yuan.

Therefore, the investment payback period of this project =920.82/563=1.6 years.

(4) Potential for replication and promotion, energy-saving potential (payback period)

This technology is applied to energy-saving technical transformation of TDI units in the chemical industry. The technical transformation method is safe and reliable, and can optimize the process to a certain extent. The energy-saving and emission reduction effect is relatively obvious, and it has certain promotion and application prospects and replication potential.