New technologies bloom like a hundred flowers, giving the sulfuric acid industry confidence in reducing emissions

At the 2014 annual conference of the sulfuric acid industry, discussions on sulfuric acid catalysts, exhaust gas treatment, energy-saving technologies, acid washing purification, and wastewater treatment were the most popular topics. The reporter noticed that whether it is the enthusiastic promotion of new technologies and products by enterprises, or the calm analysis of industry dynamics and trends by experts, all involve energy conservation, emission reduction, and clean production.

Wu Xuemei, Vice Chairman of the China Sulfuric Acid Industry Association, introduced that technological innovation is the focus of the annual meeting. By summarizing and exchanging technical experience, paying attention to and discussing new technological achievements, helping enterprises grasp industry technology trends, and promoting clean production and sustainable development in the industry.

Catalyst: Achieving New Breakthroughs

Catalysts are the core of the contact method for producing sulfuric acid, directly related to the conversion rate of sulfur dioxide and exhaust emissions. The vanadium catalyst jointly developed by Kaifeng Sanfeng Catalyst Co., Ltd., Henan University, and Zhengzhou University innovatively adopts microwave drying and medium frequency calcination processes to achieve continuous production of drying and calcination, improve drying efficiency and catalytic activity, extend service life, and significantly reduce sulfuric acid production conversion rate and emissions. This product has been used by Guangxi Daxin Guinan Chemical Co., Ltd., Jiangsu Luling Chemical Co., Ltd., Shandong Heavy Oil Chemical Co., Ltd., Yingkou Shenghai Chemical Co., Ltd., Shandong Mingrui Chemical Group Co., Ltd., and has achieved good results.

In October 2012, we started using this vanadium catalyst in a 200000 ton/year sulfuric acid plant, and it has been in use for 18 months now. The effect is very significant, with a sulfur dioxide conversion rate of 99.9%, an increase of 2-3 percentage points compared to before; the average sulfur dioxide content in the exhaust gas is only 288 milligrams/cubic meter, far lower than the original 1000 milligrams/cubic meter. The catalyst used to be replaced every year, but now it is estimated that it can be replaced every 2-3 years without any problem. Guo Hongbin, the chief engineer of Guangxi Daxin Guinan Chemical Co., Ltd., happily told a reporter from China Chemical News that the company was forced to replace the catalyst during a major maintenance opportunity due to the high sulfur dioxide content in the exhaust gas emissions, and boldly tried to use Kaifeng Sanfeng catalyst.

In mid May of this year, Kaifeng Sanfeng Catalyst Company's new method for manufacturing vanadium catalysts with independent intellectual property rights passed the scientific and technological achievement appraisal organized by the China Petroleum and Chemical Corporation in Guangxi Daxin, reaching the international advanced level.

Exhaust gas desulfurization: adapting to new standards

On October 1, 2013, the "Emission Standards for Pollutants in the Sulfuric Acid Industry" were officially implemented, with a limit of 400 milligrams per cubic meter for sulfur dioxide emissions from exhaust gas, and a special limit of 200 milligrams per cubic meter for sulfuric acid enterprises in key control areas. This new standard encourages sulfuric acid enterprises to accelerate the transformation of exhaust gas treatment technology, achieve standard emissions, and adapt to the new situation of energy conservation and emission reduction.

Jinchuan Group Co., Ltd. has built 7 sets of sulfuric acid plants to support its smelting system. Due to the large number of smelting furnaces, it is not possible to achieve "one-to-one" with the acid production system, resulting in fluctuations in flue gas emissions and concentrations, which leads to the inability to meet emission standards for tail gas. The company adopts the sodium alkali method for acid tail gas desulfurization, which achieves desulfurization through caustic soda absorption. Jia Xiaojun, Director of the Technical Office of Jinchuan Chemical Plant, introduced that the operational practice results show that the caustic soda absorption method has the advantages of high desulfurization efficiency and a wide range of tail gas adaptability. At present, Jinchuan Company is using its 530000 ton, 300000 ton, 480000 ton, and 700000 ton sulfuric acid production systems, with sulfur dioxide content in the exhaust maintained at 100-200 milligrams per cubic meter.

Chengdu Guohua Environmental Protection Technology Co., Ltd. has successfully developed a new catalytic flue gas desulfurization technology based on the technical advantages of the National Flue Gas Desulfurization Engineering Technology Research Center. Unlike traditional absorption methods, this technology uses porous materials as carriers to prepare catalysts by loading active components. Adsorption, catalysis, and regeneration are completed in the same device to convert sulfur dioxide in flue gas into sulfuric acid, achieving comprehensive resource utilization. At present, this desulfurization technology has been applied in sulfuric acid plants such as Zhonghua Fuling, Yunfu Jintai Chemical, and Sichuan Yingfeng Chemical. In late May, the technological achievements of the new catalytic method for sulfuric acid tail gas treatment and resource utilization passed the technical appraisal organized by the China Petroleum&Chemical Corporation, reaching the international advanced level.

In addition, the supergravity method for deep desulfurization technology developed by the Education Ministry's Supergravity Engineering Research Center at Beijing University of Chemical Technology is also an innovative achievement that has reached the international advanced level.

Circular Economy: Resource Reuse

The production of sulfuric acid is an exothermic reaction that produces a large amount of steam. In recent years, sulfuric acid enterprises have focused on the construction of circular economy, aiming for resource reuse and significantly improving energy efficiency. 75% of the total production capacity adopts low-temperature waste heat recovery and utilization, with a heat utilization rate of 60% to 90%. The recovery of steam from sulfuric acid is 1.6 to 1.7 tons per ton.

Our factory's pilot project for the standardization of circular economy in the production of sulfuric acid from mines just passed the assessment and acceptance organized by the National Standards Commission and the National Development and Reform Commission on June 8th, becoming the first enterprise in Zhejiang Province to pass the pilot project for circular economy standardization, "Chen Lijin, Executive Deputy Director of the sulfuric acid plant of Zhejiang Juhua Co., Ltd., told China Chemical News reporters. Since May 2011, the sulfuric acid plant has taken the pilot project of circular economy standardization as an opportunity to explore and establish a standardized model for mineral sulfuric acid circular economy, organize and implement relevant standards for circular economy, and build a standardized information platform for circular economy, achieving significant results. Over the past three years, a total of 579 standards have been established, with participation in the formulation of 2 national standards and 1 industry standard. Four large-scale technological upgrades have been implemented, including the use of supergravity tail gas desulfurization technology and thermal energy step recovery and utilization. This has resulted in an annual reduction of 1.12 tons of COD, 345.6 tons of sulfur dioxide, and 7.6 tons of wastewater, and an increase in economic benefits of 45.04 million yuan.

Mei Tongyou, Deputy Manager of the Equipment Energy Department of Guizhou Wengfu Group Chemical Company, introduced that the company produces and uses all 1.2 million tons/year of sulfuric acid independently, and the sewage has reached zero discharge. Among them, a low-temperature waste heat recovery and utilization device was newly installed in the 200000 ton/year sulfuric acid production plant last year. Subsequently, a self-developed phosphate slurry washing desulfurization treatment technology was adopted in the 800000 ton/year sulfuric acid production plant, which is currently under construction and installation. After being put into operation in July, the sulfur dioxide emission concentration in the tail gas will reach 80 milligrams per cubic meter.

At the annual meeting of the sulfuric acid industry, Yu Xiangdong, General Manager of Nanjing Hailu Energy saving Technology Co., Ltd., introduced the operation of China's first low-temperature heat recovery device for sulfuric acid production developed and implemented by the company. Since the 120000 tons/year sulfuric acid production in Mingrui, Shandong in February, the low-temperature heat recovery system has been running stably, directly producing 5-7 tons/hour of 0.8MPa low-pressure steam. The heat recovered from heating desalinated water and medium pressure boiler feedwater is equivalent to 1.2 tons/hour of low-pressure steam, and the total heat recovered is equivalent to 6-8 tons/hour of low-pressure steam. The steam recovery rate per ton of acid is 0.4-0.53 tons/ton.