Client: Sinopec Qilu Petrochemical Company
Location: Shandong, China
Project type: Retrofit, Boiler desulfurization
Capacity: 4 X 470 t/hr boilers
Time of completion: June, 2012
The flue desulfurization units for the 4 boilers were originally designed and built with a competitor’s ammonia-based desulfurization technology in 2009. The original single-column design similar to limestone/gypsum technologies brought high liquid-to-air ratio, resulting in high power consumption for circulating a large amount of absorption liquid. The generation of aerosol, which mainly consists of airborne ammonium sulfate particles, was also not properly addressed by this technology. High emission of ammonium sulfate aerosol out of the stack (see table below) led to a series of severe environmental issues to surrounding communities, as shown in the photos below, and a loss of more than 25% ammonium sulfate product.
|Pollutant||Design value (mg/Nm3)||Testing value (mg/Nm3)|
|Solid particulates||≤ 50||~800|
Retrofit with JNEP’s EADS technology
In 2011, after several unsuccessful attempts to resolve the aerosol problem by modifications and improvements to the existing devices, the client chose JNEP to retrofit the flue gas desulfurization unit with the commercially proven EADS technology. After the EPC contract was signed in October 2011, JNEP only spent 9 months to complete all four desulfurization units in June 2012 . Equipment and parts from the old units were also fully utilized in the project to minimize capital cost.
In the EADS technology, unlike the empty tower design of the original absorber, the main absorber consists of multiple separate sections to isolate the processes of flue gas cooling, SO2 absorption, ammonium sulfite oxidation and demisting, along with precise control of reaction parameters such as temperature and pressure in each section, to eliminate aerosol generation. The successful application of the improved demisting technology further enhanced the controls to aerosol and ammonia emissions. The picture below shows the plume out of the stacks after retrofit. Accord to the emission test performed by a third-party testing institute, the total ammonia recovery has been improved from 74.9% to 99.2%, and total ammonia slip is less than 4 ppmv compared an average of 82 ppmv before retrofit. In operating costs, the retrofit saves Qilu Petrochemical 1.9 MW∙hr in power consumption and 1900 ton in ammonia consumption, and the new units produces 28,000 ton more ammonium sulfate per year. The total annual cost saving is estimated to be 3.7 million dollars.
Inlet flue gas
|Flow rate（Dry basis, actual O2）||2×1,000,000 Nm3/hr|
|SO2 content（Standard condition, wet basis, actual O2）||4000 mg/ Nm3|
|S% in Fuel||1.8%|
|Design Desulfurization efficiency||≥ 99％|
|Design SO2 emission (dry basis，6%O2)||≤ 50 mg/Nm3|
|Design Ammonia slip (dry basis，6%O2)||≤ 5 mg/Nm3|
|Ammonia recovery||≥ 97％|
|Pressure drop||≤ 1800 Pa|