(1) Technical scope of application

This technology is mainly used for steam ejector transformation in the petrochemical industry.

(2) Technical principles (transformation content)

① Technical introduction

Roots blower is a positive displacement blower with impeller end faces and front and rear end covers of the blower. The principle is a rotary compressor that uses two lobed rotors to move relative to each other in the cylinder to compress and transport gas. This blower has a simple structure and is easy to manufacture. It is widely used in aquaculture aeration, sewage treatment aeration, and cement transportation. It is more suitable for gas transportation and pressurization systems in low-pressure occasions, and can also be used as a vacuum pump.

The steam ejector was eliminated and replaced with a dry Roots blower, which eliminated this part of steam usage, saved energy, and reduced wastewater generation.

① Power saving principle

The vacuum system adopts the operation mode of steam jet water supply ring pump to achieve the vacuum pressure required by the production process. At the beginning of the operation of the polycondensation process, the water ring vacuum pump is operated. When the reaction kettle pressure is lower than 15kPa, the primary steam jet pump is started, and when the reaction kettle pressure is lower than 10kPa, the secondary steam jet pump is started. The inside of the kettle and the tail gas system are in a negative pressure state at this time. The organic gas in the production process is extracted through the steam ejector, and the steam used is condensed and eventually becomes organic wastewater, which needs to be incinerated.

Steam use has been reduced by adding dry Roots blowers instead of steam injectors that use steam. In addition, the dry Roots vacuum pump eliminates the use of steam injection to achieve the vacuum required by the production process, and also reduces the amount of wastewater.

(3) Application cases

Through project optimization, Evonik Specialty Chemicals (Shanghai) Co., Ltd. eliminated two steam injectors and replaced them with two dry Roots blowers with a total power of 26KW.

1) Implementation content and cycle: Steam usage has been reduced by adding two dry roots blowers with a total power of 26kW to replace two steam ejectors that use steam. In addition, the two dry-type Roots vacuum pumps eliminate the use of steam injection to achieve the vacuum required by the production process, and also reduce the amount of wastewater. The implementation cycle is 9 months.

2) Energy conservation and emission reduction effect and investment payback period: Calculate the unit price of steam external supply at 250 yuan/ton, and the income from steam saving is 1,963.1t *250 yuan/ton = 491,000 yuan; the expenditure for increasing power consumption is 50,700 yuan; therefore, the total project income is 243,800 yuan, and the investment payback period is 116.67/ 44.03 = 2 years and 8 months.

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

This technology is widely used to replace steam injectors. The technical transformation method is safe and reliable, can maximize the steam energy of the replaced steam injector itself, and has obvious energy conservation and emission reduction effects.