At present, China is a big country in tire production and a big country in tire consumption, but at the same time, China is also the world’s largest country in the number of used tires. In 2016, the amount of used tires in the country was around 300 million, and the weight reached more than 10 million tons. And the annual production of used tires is increasing at a rate of 8% to 10%. By 2020, the number of used tires in China will reach 20 million tons. With the increasing degree of pollution of waste rubber, waste rubber has become another major pollution after the white pollution – black pollution.
How to effectively recycle and prevent pollution to the environment is not only a worldwide problem, but also a new topic facing the recycling of renewable resources in China. With the continuous upgrading of environmental protection issues, the state has also successively issued a series of policies on used tires and waste rubber.
At present, the comprehensive utilization of waste tires mainly includes refurbishment, reclaimed rubber, rubber powder, thermal energy utilization and pyrolysis. With the development of technology, high-quality and low-cost synthetic rubber has made the market for tire retreading and reclaimed rubber smaller and smaller. The market growth rate has been declining since 2012, and it is limited by technical level and production equipment. The production of road asphalt by rubber powder is also too expensive to be used in large quantities. Waste tires and other wastes are burned together to recover energy in the form of steam or electricity. Although waste tires can be disposed of in large quantities, the resource utilization rate is not high and only about 42% of energy can be recovered. In addition, renovation, manufacturing of rubber powder and reclaimed rubber, as asphalt filler, direct treatment as a fuel incineration, etc., more or less will bring secondary pollution, waste of resources, and endanger the health of residents, is not the ultimate solution.
However, for thermal cracking, there are also relevant opinions from the relevant industry, calling for China not to promote the “thermal cracking” project of used tires. Cao Qingxin believes that waste tire thermal cracking is a project with no return on investment. At this stage, from the perspective of the economic return rate of the project, it does not conform to China’s national conditions and cannot be used as a waste tire utilization direction. It should not be promoted. Although the country has promoted the “thermal cracking” project of waste tires for many years, at present, in addition to the profits of enterprises producing “thermal cracking” equipment, enterprises investing in “thermal cracking” projects basically rely on national project funds to survive, and are unprofitable. .
4 kinds of products produced by “thermal cracking” of used tires:
01, the so-called “carbon black”, which is about 35% by weight, that is, “tire slag”, is currently not recognized by the market. Carbon black as a reinforcing material for the rubber industry has strict national standards, and the cracked carbon black is more serious than the carbon black of the reinforcing material used in the rubber industry. The appearance of carbon black is not the tire residue of carbon black. Its economic value is not high. The “tire slag” after the “thermal cracking” of the waste tire is powdered. If it is not treated in a timely and environmentally friendly manner, it will also cause harm to the environment.
02, is the “cracking oil” which accounts for 40% by weight. It is a black viscous oil with a pungent odor. The flash point is only 52° low, which is easy to cause an explosion under collision. Since the waste tire is catalyzed by a cracking furnace, The original 6500 kcal heat value is reduced to about 3800 ~ 4000 kcal, and the burning of odor continues to be filled in the air, which is inferior fuel oil. There are many unsafe factors and polluted environments in “cracking oil”. The market application is narrow and the economic value is not high.
03 , it is the fine steel wire of tires with a weight ratio of about 15%. The steel wire has been separated in the rubber powder crushing process, and there is still value in use. For example, the so-called low temperature cracking at 600 ° C ~ 750 ° C, the metallographic structure of the steel wire is destroyed. The body is basically lost in use value.
The fourth is that the non-liquefiable gas produced in the “thermal cracking” accounts for about 10%, and is consumed as a cracking self-use fuel.
In order to make waste rubber and waste tires that cannot be reused as renewable resources to be harmlessly treated, it is recommended that the state organize the development of internationally advanced utilization methods so that it can maintain the heat value of more than 6,500 kcal for thermal energy utilization. Avoiding the loss of calorific value of “thermal cracking” is undoubtedly the one-step scientific utilization measure of waste tires that are economical, energy-saving and environmentally friendly.
There are different legislations in various states in the United States, but the policies for disposing of used tires are basically similar, with a disposal fee of $3-5 for each tire; Canada requires a disposal fee of $60 for each ton of used tires; A disposal fee of 140 euros is paid; Hong Kong is given a disposal fee of HK$1,700 per ton by the Environmental Protection Agency. The expenses are paid by the collected waste tire recycling fees, and the subsidies are encouraged for the profitable enterprises.