Application of PHE in the Purification of Industrial Gas

To meet the quality requirements in industrial gas usage, transportation, storage and downstream process, reduce the pollution of the atmosphere, generally adopt the alcohol amine method to purify and recycle most of by-product in industrial gas like SO2 (Sulfur Dioxide) and CO2 (Carbon Dioxide). On the basis of many years of experiences in heat exchange technology, combined with the customer's usage parameters and conditions, ACCESSEN puts forward to adopt the plate heat exchanger as lean&rich amine heat exchanger, lean&rich amine cooler, regeneration tower top condenser method to replace the low efficiency, large occupied area tube&shell heat exchanger, in the processing of alkanolamine gas purification.

Let’s study the case of lean&rich amine heat exchanger application in the project of "Shanxi Yulin Qingjian Yuanchang 1 million Nm³/d liquid nature gas project". Lean amine working temperature: 120.3℃/ 83℃(in/out),capacity: 63T/h. Rich amine working temperature: 45.8℃/85℃(in/out),capacity: 63T/h. Heat load: 2455.0KW. Logarithmic temperature: 36.24 ℃

Heat transfer coefficient（W/m2.k）   Heating area(m2)

Plate type    956.1                70.85

Tube&shell type 174                  384

PHE has following characters compare with tube type HE: saving heating area, required less installation area, low energy consumption, low cleaning frequency required, easily maintenance, low investment. 

Parts of reference:

Gansu Petrochina Kunlun Gas Co., Ltd.Lanzhou 0.3 million Nm3/d liquid nature gas peak regulation project.

Chengdu Deep Cold Liquefaction Equipment Co. Ltd.Xingjiang Qinghua Energy 0.33 million Nm3/d liquid nature gas project.

Sichuan Air Fractionation Equipment (Group) Co.Ltd. Inner Mongolia Xingshen Nature Gas Co.,Ltd. 2 million Nm3/d liquid nature gas project.

Natural gas in industrial gases (including oil field gas, gas field gas, coal bed gas, shale gas, etc.), coke oven gas, water gas, syngas, power plant gas, etc., contains SO2 and CO2 and other acidic gases. To use these gases rational and scientifically, it is necessary to purify and dispose of these gases to separate and recycle SO2 and CO2. At present, the most widely used and mature purification method in industry is alkanolamine method. The following is the process flow diagram of alkanolamine method to remove the CO2 (if the gas contains SO2 exceeds the standard, can be removed with CO2) in the pipeline gas liquefaction project. The process flow to remove other acidic gases is nearly the same.

37℃ raw nature gas enter into the bottom of absorption tower, counter flow with 40℃ lean amine solution sprayed from the top of absorption tower. The SO2 and CO2 are absorbed by the amine solution. The purified nature gas temperature is about 55℃,go from top of absorption tower and enter into the absorption tower overhead condenser, and then flow to the dewatering system to dewater. 

The lean amine which absorb the SO2 and CO2 becomes the rich amine, temperature rise to 64℃,go from absorption tower bottom. After heated by the lean &rich amine heat exchanger, temperature rise to 98℃. It enters into the regeneration tower from the top of alkylol amine solution regeneration tower, counter flow with rising gases from bottom of regeneration tower. Under the high temperature steam flow blows, SO2 and CO2 in alkylol amine solution are parsed, condensed by the regeneration tower overhead condenser, it becomes to 40 ℃ gas to the next working procedures. 

After separation of SO2 and CO2, 122 ℃ regeneration alkanolamine solution is called the lean fluid. It is cooled down to 88℃ by the lean&rich amine heat exchanger, and then go through the air cooler and lean liquid cooler, the temperature dropped to 40 ℃. And then it enters into the absorption tower from top of tower, counter flow with rising nature gas from absorption tower bottom. It absorb the SO2 and CO2 from nature gas, and then goes to re-generator regeneration tower to regenerate, to repeat the processing to purify the gas.

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Ethan Wang Foreign Trade Manager at SHANGHAI ACCESSEN GROUP CO., LTD