(1) Technical scope of application

This technology is mainly used in the chemical industry.

(2) Technical principles (transformation content)

① Technical introduction

Most heat exchangers are made of stainless steel. If the temperature of the heat exchange wall of the heat exchanger is too high and the flow rate on the circulating water side is small, once the chloride ion concentration in the circulating water is increased, the risk of stress corrosion cracking may be caused. Several heat exchangers were renovated and measures were taken to reduce their heat exchange area or replace their types.

② Energy saving principles

1) Build an operating model of the circulating water system, finely control the operating costs of the system, and avoid the impact of factors such as operating load changes, environmental factors and raw water quality.

2) Through the transformation of key heat exchangers, measures to reduce their heat exchange area or replace the type are taken to increase the flow rate on the circulating water side and avoid corrosion problems caused by the increase in chloride ion concentration.

3) By improving the control of chloride ion concentration in circulating water, the amount of desalted water replenishment and sewage discharge are reduced.

(3) Application cases

The chloride ion concentration optimization project of the circulating water system of Evonik Special Chemicals (Shanghai) Co., Ltd.

1) Implementation content and cycle: Based on on-site operation and environmental factors, a system model is built to finely control the amount of drainage and water. The chloride ion concentration in circulating water is increased from the originally controlled 150mg/L to 250mg/L, thereby reducing the amount of desalted water replenishment. The implementation cycle is 1 year and 7 months.

2) Energy conservation and emission reduction effect and investment payback period: Save desalinated water replenishment =(percentage of desalinated water replenishment before transformation to circulating water volume-percentage of desalinated water replenishment after transformation to circulating water volume)* Circulating water volume before transformation =(0.62%-0.31%)* 122944197t=381127t。In addition, the increase in industrial water consumption =(percentage of industrial water replenishment before transformation to circulating water volume-percentage of industrial water replenishment after transformation to circulating water volume)* Circulating water volume before transformation =(0.55%-0.29%)*122944197t=319655t。

Considering that the conversion coefficient between desalinated water and industrial water is 0.65, the annual amount of water can be saved =381127t÷0.65-319655t=266694t.

Taking into account the increase in industrial water replenishment, the decrease in desalinated water replenishment, the decrease in sewage discharge and the decrease in pharmaceutical costs, the project saved a total of 2.101 million yuan, so the investment payback period is 175.16 million yuan/2.101 million yuan*December = 1 (month).

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

This technology is applied to energy-saving technical transformation of chloride ions in the circulating water system in the chemical industry. The technical transformation method is safe and reliable, the energy-saving and emission reduction effect is relatively obvious, and the potential for promotion, application and replication is relatively large.