Independent technology ensures energy conservation and emission reduction standards in the sulfuric acid industry

The 12th Five Year Plan is a crucial period for energy conservation and emission reduction, elimination of outdated production capacity, promotion of clean production, and realization of circular economy in the sulfuric acid industry. Innovative measures such as tail gas treatment desulfurization, sulfuric acid catalysts, and low-temperature heat recovery will lay the foundation for this goal. This is the message conveyed at the 14th annual meeting of the National Chemical Sulfuric Acid and Phosphate Fertilizer Design Center held in Nanjing on July 11th.

Starting from October 1, 2013, the limit for sulfur dioxide emissions from sulfuric acid plant exhaust will be adjusted from the current 960 milligrams per cubic meter to 400 milligrams per cubic meter, which is the most significant indicator of the new national standard affecting the industry, "said Li Chong, Deputy Secretary General of the China Sulfuric Acid Industry Association. The association conducted a comprehensive survey on sulfur dioxide emissions in the entire industry last year, and the results showed that large-scale facilities were better than small and medium-sized facilities, and sulfur based acid production facilities were better than pyrite and smelting flue gas based acid production. Among them, the concentration of sulfur dioxide emissions from large-scale sulfuric acid production tail gas is 500 milligrams per cubic meter, while the concentration of sulfur dioxide emissions from small-scale pyrite acid production and smelting flue gas acid production is as high as 800 milligrams per cubic meter. Some enterprises even reach over 1000 milligrams per cubic meter. The industry's sulfur dioxide emissions from tail gas are not optimistic. In response to this situation, Zhang Yilin, consultant of the National Chemical Sulfuric Acid and Phosphate Fertilizer Design Technology Center, told reporters that choosing a suitable tail gas desulfurization scheme and considering technological transformation measures such as replacing catalysts have become the top priority for sulfuric acid enterprises.

The reporter learned at the meeting that the supergravity desulfurization technology of Beijing University of Chemical Technology has been industrially applied in Juhua Co., Ltd. and Tongling Huaxing Chemical Co., Ltd. Among them, the average concentration of sulfur dioxide in the exhaust emissions of Tongling Huaxing is 360.63 milligrams per cubic meter, which is nearly 40 milligrams lower than the new national standard. After the transformation of Juhua Corporation, the annual pollution discharge fee can be reduced by 280000 yuan. The absorbed sulfur dioxide can be used to increase the production of ammonium sulfite and ammonium bisulfite by about 1300 tons, achieving circular development while saving energy and reducing emissions.

In addition to Topso from Denmark, a group of domestic catalyst companies such as Shandong Aobao Chemical Group and Nanhua Group Research Institute are also actively promoting localized technologies to the market.

The AS series catalysts of Aobao Chemical Group Co., Ltd. have been added and used in sulfuric acid plants in Baotou, Inner Mongolia, Shouguang, Shandong, Anqiu and other places, successfully achieving the new target of sulfur dioxide emission concentration below 400 milligrams per cubic meter.

As the only wet process conversion catalyst in China with independent intellectual property rights, the vanadium catalyst developed by Nanhua Group Research Institute can replace expensive imported VK-WSA dedicated catalysts.

In addition, it is worth mentioning that the 980000 tons/year sulfuric acid flue gas treatment plant of Hubei Daye Nonferrous Metals Co., Ltd., which is supported by the National Engineering Technology Research Center for Flue Gas Desulfurization, was successfully put into operation in September 2011. The sulfur dioxide concentration in the export exhaust gas does not exceed 50 milligrams/cubic meter, and the direct cost of adding one ton of sulfuric acid is only 1 yuan. This project has been listed by the National Development and Reform Commission as a "demonstration project for flue gas desulfurization in non power industries

At present, sulfuric acid tail gas desulfurization technology mainly includes catalyst technology, ammonia acid method, supergravity method, sodium alkali method, new catalytic method, activated coke method, organic amine method, etc. The desulfurization efficiency of each technology is above 90%, and the sulfur dioxide in the exhaust gas can be less than 200 milligrams per cubic meter. The specific technical solution to be adopted by sulfuric acid enterprises needs to be tailored to local conditions, comprehensively considering economic issues such as technological maturity, sources of desulfurizers, outlets of by-products, and investment and operating costs, "said Zhang Yilin.

Not only has the work of reducing pollutants been carried out with great success, but the reporter found that sulfuric acid enterprises have also put a lot of effort into energy conservation and consumption reduction. The low-temperature heat recovery technology to improve the waste heat recovery rate has attracted the attention of many enterprises.

At present, there are more than 20 sets of equipment in China that adopt our company's low-temperature heat recovery technology. Among the 12 sets of equipment that have been put into operation, the concentration of acid mist is basically 30 milligrams per standard cubic meter, and the longest operating time has exceeded two years, "said Professor Zou Yushuang of Sinopec Nanjing Engineering Co., Ltd.

From the operation of the company's technical equipment, it can be seen that the domestic low-temperature heat recovery technology has matured. The equipment is easy to operate, the construction period is short, and the technical services are timely and thoughtful, which cannot be achieved by imported equipment. These are also the reasons why domestic technology has been rapidly promoted in China in the past two years, "said Bin Guangnian, Deputy General Manager of Shandong Bofeng Lizhong Chemical Co., Ltd.

Newly established enterprises need to make comprehensive comparisons, choose good conversion processes and catalysts, and also consider selecting suitable tail gas recovery equipment, striving to solve the problem of sulfuric acid tail gas emissions in one go. Existing enterprises need to develop renovation plans in a short period of time, otherwise they will face the consequences of being eliminated, "said Zhang Yilin. At present, the production of large sulfuric acid enterprises has dominated. Data shows that the top 10 enterprises in sulfuric acid production and smelting flue gas acid production account for 49.3% and 49% of their total production, respectively.

The upcoming "Energy Consumption Limit for Industrial Sulfuric Acid Unit Products" and the currently being formulated "Clean Production Standards for Sulfuric Acid Industry" will strictly control the production of sulfuric acid plants. By the end of the 12th Five Year Plan, China's sulfuric acid production capacity will leap to 100 million tons, and various new technologies and equipment will ensure that 90% to 95% of the production capacity meets energy-saving and emission reduction targets.