The issue of industrial grade sulfuric acid disposal has not been well resolved. Every year, 100 million tons of waste sulfuric acid are produced, and many of them are discharged illegally or directly, which must be of concern to all parties. Why does the problem of unauthorized discharge and untreated dumping of waste sulfuric acid occur repeatedly? What is the difficulty of recycling?

After investigation, it was found that the exposed problem of waste sulfuric acid is only the tip of the iceberg. To properly solve it, it is not only necessary to strictly enforce the law, but also to understand the emission situation of enterprises, prevent enterprises from falsifying, and find feasible methods for treatment and reuse.

According to relevant research and statistics, China produces as much as 100 million tons of waste sulfuric acid annually, which is far from the 5 million tons of waste sulfuric acid produced annually according to some statistical data. Where has such a huge amount of waste sulfuric acid gone? If you search for "illegally discharging waste sulfuric acid" on Baidu, you can see over 20000 pieces of information.

Just this summer, the case of Jinghang Xudong Technology Company illegally discharging over 1500 tons of waste sulfuric acid to pollute the Jinghang Grand Canal entered the public prosecution stage. This is the first case in China where the Grand Canal was sentenced for polluting its water quality after being listed as a World Heritage Site. Almost simultaneously, the Environmental Protection Bureau of Jimo City, Shandong Province investigated and punished a local enterprise for discharging waste acid generated by pickling steel plates into a sewage pipeline.

In the "illegal sewage discharge event in Tengger Desert" that attracted wide attention last year, the main component of the sewage secretly discharged by Ningxia Mingsheng Dyeing and Chemical Co., Ltd. is highly concentrated waste acid. According to reports, there are also enterprises that use methods such as laying concealed pipes to discharge untreated waste acid into municipal pipelines, ditches, rivers, and ponds, which can be said to be groundbreaking in terms of illegal discharge.

Why are there so many incidents involving the illegal discharge of waste sulfuric acid? Why do companies take risks even when they know it's illegal? China is a major producer and user of sulfuric acid. It is predicted that the consumption of sulfuric acid in China will reach 110 million tons by 2018. Faced with such a huge consumption, it is not only necessary to pay attention to the safe use of sulfuric acid, but also to solve the problem of disposing of waste sulfuric acid.

Chemical industry: the most serious problem is the illegal discharge of waste sulfuric acid

In the north, there seems to be some organization, while in the south, there seems to be some petty commotion

It is understood that sulfuric acid is used in the production of industries such as fertilizers, chemicals, metal processing, and fiber industry. In the consumption industry of sulfuric acid, the fertilizer industry accounts for the largest proportion of usage, accounting for 61.5% of the total amount of sulfuric acid in China in 2013. However, this industry does not produce waste sulfuric acid. On the contrary, it is the chemical industry that follows closely in terms of usage.

According to Wang Zaijun, the chairman of Qingdao Aogaike Chemical Co., Ltd., the chemical industry is the most serious industry in which waste sulfuric acid is illegally discharged. Among them, the problem of disorderly discharge and disposal of oil refining, battery disposal, and other enterprises and small pits is serious. According to statistics, China's chemical industry consumed approximately 23 million tons of sulfuric acid in 2013. If 40% -50% of sulfuric acid (about 10 million tons) participates in the reaction to generate new substances, and about 13 million tons of other sulfuric acid forms waste sulfuric acid with a concentration of 20% -60%, it is preliminarily estimated that various concentrations of waste sulfuric acid can form over 40 million tons.

According to statistical analysis of recent incidents of waste sulfuric acid pollution, it has been found that chemical enterprises account for a significant portion. Through comparison, it was found that there are significant differences in the illegal discharge of waste sulfuric acid between the north and south, but there are also some patterns. From the perspective of the location of waste sulfuric acid discharge, the main types of waste sulfuric acid discharge occurring in northern provinces and cities are infiltration pits or small ditches and rivers; In the pollution incidents that occurred in southern provinces and cities, waste sulfuric acid was mainly illegally discharged into rivers, ponds, and other areas, with an astonishing amount of illegal discharge, with major cases involving hundreds or even tens of thousands of tons occurring.

This is related to the large rivers in the south, and the waste sulfuric acid can be easily diluted after being illegally discharged, thus eliminating the traces of illegal discharge. Industry insiders have revealed that most of the waste sulfuric acid illegally discharged in northern provinces and cities are entrusted by enterprises to others to illegally discharge from other places. The illegal discharge is a temporary initiative for profit, not an organized crime. We often describe the illegal discharge method in the north as' small and petty '. However, in southern provinces and cities, there is organized illegal discharge, which has even become an' industry '. For example, the Suzhou Xudong Technology Development Co., Ltd. mentioned earlier illegally discharged 1500 tons of dilute sulfuric acid to pollute the Beijing Hangzhou Grand Canal

However, this industry insider also stated that these discovered illegal cases of waste acid discharge are only the tip of the iceberg, as many were discovered only after public reports or environmental protection departments discovered abnormal water quality. There are also more covert methods of discharge, such as laying hidden pipes.

From January 2012 to February 2013, six companies, including Jiangsu Changlong Agrochemical Co., Ltd., violated legal regulations by providing subsidies ranging from 20 to 100 yuan per ton to over 25000 tons of waste hydrochloric acid and sulfuric acid generated in the production process of the enterprise, to 14 individuals without hazardous waste treatment qualifications, including Dai Weiguo. These waste acids were directly discharged into the Rutai Canal in Taixing City and the Gumagan River in Gaogang District of Taizhou City without any treatment, resulting in serious water pollution. Last December, the Jiangsu Provincial High People's Court made a final judgment, and the six chemical enterprises involved were awarded compensation of over 160 million yuan for environmental restoration costs. However, in the eyes of industry insiders, simply using legal means and economic penalties to restrain polluting enterprises is not enough.

Unclear emissions

The industries that produce waste sulfuric acid are scattered, with varying concentrations of waste sulfuric acid and various harmful impurities.

Why is it difficult to effectively regulate the large amount of discharged waste sulfuric acid? This is related to the dispersed industry and extensive sources of waste sulfuric acid production.

It is understood that there are many industries and processes involved in the production of waste sulfuric acid in industrial production, including the nitration, sulfonation, esterification, alkylation of organic matter, and the production of other fine chemical products, steel pickling, battery waste liquid, and chlorine gas drying, as well as the petroleum refining industry and chemical fiber industry. However, except for industries such as titanium dioxide, petroleum processing, and steel pickling, which generate a large amount of waste sulfuric acid, the production of waste sulfuric acid by individual enterprises in other industries is not significant. Some enterprises produce between a few hundred to several thousand tons of waste sulfuric acid annually. The dispersion of sources exacerbates the difficulty of centralized collection and processing.

At the same time, the concentration of waste sulfuric acid generated by various industries and production processes varies, and the content of harmful impurities is generally high. The waste sulfuric acid produced by some enterprises also contains heavy metals, while the waste sulfuric acid produced in the fine chemical industry mostly contains organic substances, which makes disposal even more difficult.

Senior chemical expert Zhou Yue stated that many enterprises in China still use lime, calcium carbide slag, and hydrated lime to neutralize waste sulfuric acid. The pH value of the treated waste liquid can meet the requirements, but other indicators are difficult to meet. The sludge generated after treatment is basically stacked or buried, including some hazardous waste treatment plants that also use this method. They only temporarily seal up the pollutants, which does not meet the requirements of harmless treatment and is prone to secondary pollution.

At the same time, some companies also use alkali to neutralize waste sulfuric acid and discharge solutions that meet pH standards, but there is still a large amount of sulfate and organic matter in the solution, which still poses a serious threat to the environment after discharge, "Zhou Yue said.

When it comes to solving problems, Zhou Yue believes that the first step is to understand the current situation of emissions. Although many people have been subject to legal sanctions in recent years for illegally transporting or illegally discharging waste sulfuric acid, this is only the tip of the iceberg. Only by truly understanding the true amount of waste sulfuric acid produced by various production enterprises can we comprehensively control the destination and use of waste sulfuric acid

He suggested conducting a nationwide survey of the enterprises that produce waste sulfuric acid to determine the concentration, quantity, and impurities contained in the waste sulfuric acid, and categorizing them based on their different concentrations and impurities, in order to facilitate resource utilization and management. At the same time, stricter environmental approval procedures will be implemented for enterprises that produce waste sulfuric acid. Chemical experts will be invited to review material balance issues in enterprise production, strictly control enterprise fraud, and not report or underreport the amount of waste sulfuric acid produced.

High processing costs become a bottleneck

The cost of waste sulfuric acid treatment is much higher than the product price, and enterprises do not have the motivation for treatment and reuse.

It is reported that the concentration of waste sulfuric acid generated in China currently ranges from 6% to 90%, and the treatment methods are also different. Industry insiders admit that the current situation of difficult disposal of waste sulfuric acid is only a typical example of pollution control, with treatment costs far higher than product prices, which makes it difficult for enterprises to handle and reuse.

For example, the scale of enterprises in the petroleum refining industry is relatively large, and many refineries use waste sulfuric acid cracking to produce sulfuric acid. However, this method causes severe equipment corrosion and high production costs.

According to calculations, the cost of using waste sulfuric acid cracking to produce sulfuric acid is between 700-900 yuan/ton, much higher than the current market price of 300-400 yuan/ton for sulfuric acid. According to a survey conducted by China Chemical Information Network, by the end of 2013, only 8 sets of waste sulfuric acid cracking and sulfuric acid production plants had been put into operation in China. Although the production capacity can reach 140000 tons/year, it is far from the amount of waste sulfuric acid produced in this industry.

In other industries, the issue of high recycling costs also exists. According to Wang Zaijun, in the metal processing and pickling industry, ferrous sulfate and sulfuric acid can be recovered through concentrated crystallization. However, due to the current low prices of ferrous sulfate and sulfuric acid, the processing cost is much higher than the product price. Large steel mills recycle waste acid, but more small and medium-sized steel mills find it difficult to treat it.

Experts have stated that there are currently many waste acid treatment technologies in China, but if used, it will inevitably increase costs. For example, ion separator treatment technology utilizes a special semi permeable membrane to separate or concentrate solvents and solutes under external pressure, which greatly reduces pollution. However, the cost of treating waste acid is around 400 yuan/ton.

Generally speaking, the profit from selling one ton of finished products by steel rolling enterprises is only around one hundred yuan. In this case, some enterprises may sacrifice the environment for economic benefits in order to save costs, "said the expert.

It is worth noting that even with simple acid-base neutralization treatment, some enterprises are still unwilling to bear the treatment cost and choose to discharge the waste sulfuric acid secretly. Last year, Beijing Aoliyi Economic and Trade Co., Ltd.'s Mentougou Waste Oil Treatment Center, in order to save treatment costs, directly discharged wastewater containing sulfuric acid into the municipal pipeline network, and even privately built hidden pipes to secretly discharge production wastewater.

Of course, some companies have also found feasible ways to treat waste acid. For example, if the waste sulfuric acid discharged from the acyl pickling process at Nanjing Steel Rolling Plant contains a large amount of ferrous sulfate, the acid solution after removing ferrous sulfate can be returned to the steel pickling process for further use by using a concentration crystallization filtration process

Industrial grade sulfuric acid