Feasibility Analysis Of Large-Scale Popularization And Application Of Chrome Tanning Technology

Feasibility analysis of large-scale popularization and application of chrome tanning technology
The background of chrome free tanning technology is discussed.
(2) analysis of resources of non chrome major metal tanning agents and their influence on environmental factors.
(3) the economy of metal (chrome free) compound tanning technology and the characteristics and technical maturity of LTA 1 metal (chrome free) compound tanning agent are discussed.
(4) the large-scale application and popularization of LTA 1 metal (chrome free) compound tanning agent is proved to be feasible in many aspects.
Many substances have more or less binding action with collagen, but they are of industrial value and can not be used as tanning agents. Tanning agents can be divided into three categories: tanning agent, chrome tanning agent, titanium tanning agent, aluminum tanning agent, silicate, etc. the typical products are tanning agents based on aldehyde tanning. Typical products include (modified) glutaraldehyde, oxazole, four hydroxymethyl phosphine (organic phosphorus), and so on.
Although these types of tanning agents have been studied and applied, tanning agents and tanning gum are widely used in leather tanning process. Chrome tanning agent can give leather good moisture and heat stability. It is almost the main tanning agent in the production of light leather. Tannin extract (vegetable tanning agent) can give leather good formability and wear resistance, and become a main tanning agent which can not be replaced in the production process of heavy leather such as leather and leather. Especially in the modern leather making industry, the proportion of light leather occupies a relatively high proportion, and the proportion of heavy leather is relatively small. Therefore, the proportion of chrome tanning agents is greater in the main tanning agent.
Although Dennis invented the one bath chrome tanning method in 1893, chrome tanning agent has become the main tanning agent for leather (light leather) tanning, which is almost irreplaceable. However, tanning industry has been studying other tanning agents and their cooperation to tanning leather, such as aluminum tanning agent, zirconium tanning agent, titanium tanning agent, aldehyde tanning agent, zirconium aluminum combined tanning, etc. In recent years, with the development of the global economy and the progress of the society, the pollution of chromium, the safety of chrome tanned leather products and the disposal of waste chrome tanned leather products have attracted more and more attention. Therefore, the development of chrome free tanning products is very urgent. The large-scale popularization and Application of chrome free tanning technology has become a matter of expectation for the leather industry.
1. background of chrome free tanning technology
1.1 chromium pollution and harm accelerate the development of chrome free tanning technology.
In the tanning industry, chromium pollution to the environment generally comes from three aspects: first, the pollution of chrome tanning agents during production and processing; the current chrome tanning agents are basically spray dried, and the pollution has been effectively controlled; second, the pollution of sewage, sludge and chromium solid wastes in tanning process; and third, the two pollution to the environment after the consumption of chromium products. This pollution is often ignored by people, but it accounts for about 70% of the total chrome pollution in the tannery industry, and is quite dispersed, which is not conducive to management or recycling.
The chrome utilization rate of conventional chrome tanning is only 65% to 75%, and a large amount of chromium that has not been absorbed is discharged directly. The chromium content in the total sewage of tanning enterprises is about 60 ~ 140mg/L, far higher than the highest limit of 0.2 to 5mg/L stipulated by the emission standards of industrial wastewater in various countries, resulting in serious waste of resources and environmental pollution.
Chromium, which is difficult to degrade due to general biochemical methods, is usually accumulated in the environment for a long time. Long term uncontrolled emissions will also cause water pollution, affect the growth of aquatic organisms and microbes, destroy the ecological balance, and are not conducive to self purification of water bodies. Moreover, there is a potential danger of generating highly toxic six valent chromium. Finally, chromium may endanger human health through the food chain, and its environmental and human hazards have been scientifically verified repeatedly.
With the increasing awareness of chromium pollution and its environmental hazards and the increasing environmental pressure, especially the attention to the two pollution problems after the consumption of chromium products, the accelerated development of chrome free tanning technology has been promoted. The large-scale application and popularization of clean, environmental friendly and ecological chrome free tanning technology has become an inevitable trend.
1.2 shortage of chromium resources to promote the development of chrome free tanning technology in China
Chromium in the earth's reserves of 0.018%, is less abundant reserves of metal elements. Our country's chromite resources are relatively poor. According to the degree of meeting the demand, they are short of resources. Total reserves of ore 10 million 780 thousand tons, of which 53.6% of the rich ore. There are 56 producing areas of chromite, which are distributed in 13 provinces (regions), such as Tibet, Xinjiang, Inner Mongolia, Gansu, etc., with Tibet as the main factor, and the reserve accounts for about half of the country.
The raw material of chrome tanning agent in China is imported from South Africa, Kazakhstan, Zimbabwe, Finland, India, Turkey and Albana, which are rich in chromite resources. Its price fluctuates with the international market. In 70s, the friendship between China and Azerbaijan was deeper. Our country imported alunite mainly from Albany. After that, the relations between the two countries deteriorated. Albanian stopped exporting red sulfate to our country. At that time, some people began to look for tanning materials instead of chrome tanning agents. Therefore, the shortage of chromium resources in China also promotes the development of chrome free tanning technology in China.
2. resources of non chrome major Metal Tanning Agents
Lan Yunjun and others pointed out that chrome free tanning agents such as tanning agent, tannin extract and tanning based tanning agent, etc., are not only chrome tanning agents, such as tanning agents and aldehyde tanning agents, but also from three aspects: the shrinkage temperature of tanning leather, the matching of subsequent products and materials, the comprehensive properties of leather, and the consideration of ring protection and ecology. Metal (chrome free) compound tanning agent is most likely to become the mainstream product of chrome free tanning. Considering the tanning properties of tanning agents, compatibility of different tanning agents, solubility of compound tanning agents, and economy of tanning agents, the main tanning agents used in non chrome metal compound tanning agents may have zirconium tanning agents, titanium tanning agents and aluminum tanning agents. Especially, tetravalent zirconium ions can give leather a higher shrinkage temperature. Therefore, zirconium is a necessary component of metal (chrome free) compound tanning agent and even the first component [3]. Table 1 lists the contents of four tannin elements in the earth's crust.
Table 1 the contents of four tannin elements in the earth's crust [4]
According to table 1, the content of zirconium in the crust is relatively rich compared with that of chromium. Because zirconium and hafnium are very similar in chemical nature, zirconium and hafnium are symbiotic in nature, but hafnium coexisting with zirconium generally accounts for only 1% to 2% of the total mass of zirconium and hafnium. Table 2 lists the world's Zirconium reserves.
According to information, China's zirconium ore ranks the ninth largest in the world, mainly in Guangdong, Hainan, Guangxi and Shandong. Other provinces such as Hunan, Hubei, Anhui, Fujian, Jiangxi and Liaoning also have some zirconium resources [5].
Titanium is one of the most widely distributed and highly abundant (6320 * 10-6) elements in the earth's crust. It ranks ninth in terms of the weight of the earth's crust. There are more than 140 kinds of titanium minerals in the earth's crust, but it has more than ten kinds of mining value. Titanium resources rank only fourth after iron, aluminum and magnesium, and are important raw materials for the production of titanium slag, synthetic rutile, titanium dioxide, sponge titanium, titanium and titanium, and electrode coatings. Titanium is widely used in aviation, aerospace, naval ships, military industry, metallurgy, chemical industry, machinery, power, seawater desalination, transportation, light industry, environmental protection, medical devices and other fields, and plays an important role in the development of national economy.
Aluminum reserves are very abundant on the earth. At present, the proven world aluminum ore reserves are about 250 billion tons, but the distribution is very uneven around the world. The countries with reserves of more than 10 billion tons are Guinea, Australia, Brazil, China, Jamaica and India. The total reserves of these countries account for about 73% of the world's aluminum deposits. Australia, South America, Africa and other areas have good quality, large reserves and low cost. ?
In 2004, the proven bauxite reserves in China amounted to 5.3 billion tons. China's bauxite deposits are the most abundant in four provinces (regions) of Shanxi, Guizhou, Henan and Guangxi, accounting for 85.5% of the total national reserves.
From the above analysis, we can see that the main raw materials of chrome free tanning agents are rich in chromium, titanium and aluminum.
Analysis of environmental factors in 3. metal (chrome free) compound tanning agent tanning technology
According to the direction of sewage discharge, the People's Republic of China comprehensive wastewater discharge standard (GB8978-1996) provides the maximum permitted discharge concentration of 69 kinds of water pollutants. This standard applies to the discharge management of water pollutants in existing enterprises and institutions, as well as the environmental impact assessment of construction projects, the design of environmental protection facilities for construction projects, the completion acceptance and the discharge management after commissioning. The standard specifies mercury, cadmium, chromium, arsenic, lead, nickel, beryllium, silver, copper, zinc, manganese, phosphorus and so on. The total chromium content in wastewater should be lower than 1.5mg/l, and the six valence chromium content should be lower than 0.5mg/l. However, there is no limit to other non Chrome tanning metals such as zirconium, titanium, aluminum and iron. From the existing literature review, it has not been reported that these non chrome tanning metals have obvious environmental impact.
Economic analysis of 4. metal (chrome free) compound tanning agent tanning technology
Zirconium, titanium and aluminum, which are the main components of chrome free compound tanning agents, are rich in chromium, but zirconium and titanium salts are more complex than those of chrome. The zirconium salt and titanium salt are more complex and difficult to be economically prepared. Therefore, the price of zirconium tanning agents and Titanium Tanning Agents is much higher than that of chrome tanning agents. Although aluminum salt is of wide origin, easy processing and low price, aluminum salt tanned leather is not resistant to water washing, and it is easy to tanning after backwater, which makes leather become flat and rigid, and the leather is thin and thin. Therefore, the proportion of compound tanning agent is relatively small, and the cost of metal (chrome free) compound tanning agent can not be significantly reduced by three. It is possible to form metals.
In addition, the preparation of metal (chrome free) compound tanning agent requires the formulation and addition of special additives on the basis of the use of various single non chrome metal tanning agents. The manufacturing cost will be further improved. The chrome free tanning mate D8 will also be used during the use, and it will also increase the cost. According to preliminary calculations, the cost of tanning leather with metal (chrome free) compound tanning agent is certainly higher than that of chrome tanned leather. Taking sheep skin garment leather as an example, the cost per square foot is increased by 0.5~1.0 yuan at the current price level.
It is one of the dozens of processes in leather processing, and the effect of its proper cost increase on the cost or price of leather products is limited. Second, compared with chrome tanning, chrome tanning agent without chrome pollution can simplify the treatment of tannery sludge, reduce incineration cost, and reduce the pollution cost. Third, metal (chrome free) compound tanning agent is white and has better electrochromic properties than chrome tanned leather, and the processing of all kinds of leather is easier (especially coloured leather), which can reduce some cost. Fourth, metal (chrome free) compound tanning agent does not contain the two pollution problem after the consumption of leather products. But at the same time, we should see, first of all, tanning process is only
In general, tanning with metal (chrome free) compound tanning agent will slightly increase the cost of leather processing, but it will be beneficial to the treatment of tannery sludge and the processing of all kinds of leather, and there will not be two environmental pollution problems. At the same time, according to the current market situation, the price of chrome free tanning leather is 2 to 5 yuan per square foot than that of chrome tanned leather. Therefore, metal (chrome free) compound tanning agent is used for tanning.