Waste disposal is a big problem in urban management. According to statistics, more than 600 cities in China have piled or buried 8 billion tons of all kinds of garbage, and about 1/3 of them are surrounded by garbage. With the rapid development of China's economy and the process of urbanization, this data is also increasing at an average annual rate of 8% - 10%. Can we find a way to swallow garbage and spit out energy to solve the "garbage siege"? Recently, a new device using microwave technology to decompose domestic waste into oil, gas, activated carbon and other products has emerged, and this technology may be used to achieve waste treatment and resource regeneration in the future.
A. Waste can be decomposed into oil and gas
People produce hundreds of millions of tons of domestic, industrial and construction waste every year. These organic solid wastes, such as plastic products, waste clothes, food waste, garden waste, medical waste, which are thrown away by us, are actually more useful in addition to being burned as waste products into coke.
Scientific research has found that garbage contains rich energy resources, and garbage can be used for power generation, composting and even oil refining. The United States calls garbage the second mineral, and the garbage disposal industry is also regarded as a sunrise industry. In China, some researchers estimate that the recyclable value of waste generated every year is up to 25 billion yuan. For China, which is plagued by energy shortages, rising oil prices and other problems, these garbage that can't be placed anywhere is actually a huge treasure house.
In 2011, Canada used microwave irradiation pyrolysis technology to recycle used tires Microwave pyrolysis The waste tire treatment facility is conducted at the molecular level. It does not melt tires, but degrades and breaks molecular bonds. Almost 100% of the waste tire resources are recycled, and 900000 liters of fuel are recycled annually.
Although there is no precedent in foreign countries for microwave irradiation pyrolysis technology to be applied to garbage treatment, it points out a direction for garbage treatment.
At present, our country has made some progress in the research of using microwave technology to decompose garbage. This technology first sorts the original garbage and processes it into garbage raw materials suitable for microwave pyrolysis. Garbage is cracked into gas, liquid and solid products under the reductive effect of microwave, and then the sorted garbage microwave cracking products can be processed into products using chemical and chemical technology. After the gas products are treated, they can be directly used for gas power generation. Liquid products are separated by oil-water separator, and the separated water is purified by wastewater treatment. The oil enters the distillation tower to separate fuel oil with different boiling points. The solid product can be used to prepare activated carbon, and the calcium silicate separated from it can also be sold as building materials, or processed into calcium silicate board and carbon containing decorative materials.
B. Realize harmless disposal of garbage
There are three traditional waste treatment methods: incineration, landfill and composting. However, in the process of garbage disposal, people found that although these methods can partially solve the problem of garbage disposal, there are problems of environmental pollution and low resource utilization.
As a key recommended project of the national environmental protection industry, the 23rd Institute of the Second Academy of China Aerospace Science and Industry Corporation has developed a device for cracking waste using microwave technology. This high-power microwave irradiation and pyrolysis waste equipment is like a super large "microwave oven", which will microwave heating Decomposition can not only make garbage harmless, but also make comprehensive energy utilization of garbage at different levels, so as to turn waste into treasure for multiple purposes. This is also an advanced technology that can simultaneously complete waste treatment and resource regeneration in China, which has been tested in the R&D and production base in Beijing.
"In the past, the scene of black smoke curling up when burning garbage will not exist, and the pyrolysis equipment will carry out harmless treatment for garbage in the furnace. Because there is no oxygen in the furnace, it will not produce toxic gas like the incineration of garbage. The treatment process will be carried out under reducing conditions, and will not produce nitrogen oxides, sulfur oxides, dioxins, high priced heavy metal oxides and other toxic gases Harmful substances, of which some carbon is fixed and activated carbon is produced, which greatly reduces CO2 emissions and meets the requirements of the low-carbon economy vigorously advocated at present. The treated wastewater meets the national emission standards and can be recycled. " Wei Shidong, a researcher at the 23rd Institute of the Second Academy of China Aerospace Science and Industry Corporation, said.
C. About 3000 cubic meters of natural gas will be produced every day
The key component for microwave pyrolysis of garbage is the microwave pyrolysis chamber, which is also the "belly" of the super microwave oven. As a reaction vessel for pyrolysis of waste materials under microwave irradiation, the performance of pyrolysis chamber directly determines the efficiency and product quality of waste pyrolysis. The development of microwave cracking chamber needs to solve such problems as microwave isolation, microwave distribution, material distribution, material flow and control, continuous feeding and discharging, coking treatment and continuous cracking under reduction conditions. It is a typical multidisciplinary integrated technology product.
The effective volume of the microwave cracking chamber used for garbage treatment this time exceeds 1000 liters, which is currently known as the domestic zui large cracking reaction chamber. After calculation, one 20KW Microwave waste pyrolysis equipment One ton of garbage can produce 37.5 cubic meters of natural gas, 37-62 liters of fuel oil and a certain amount of activated carbon. The 150KW "super microwave oven" can process 80 tons of raw garbage every day, and is expected to produce 2964-4964L of fuel oil and about 3000 cubic meters of natural gas every day, which is equivalent to the use of nearly 600 natural gas tanks.
According to statistics, Beijing's domestic waste output in 2014 was 7.33 million tons, with a daily average of 20000 tons. If microwave pyrolysis treatment is carried out, 27.49 million cubic meters of natural gas and 27.16 million liters - 45.26 million liters of liquid fuel will be generated from waste treatment, production and reuse throughout Beijing, which can not only solve the dilemma of the current garbage siege, but also truly turn waste into treasure and achieve sustainable development of environment and resources.
At present, this device is in the stage of test and demonstration, and it is planned to process 20 tons of raw garbage per day. After the test is mature, the device will reach the capacity of processing nearly 100 tons of raw garbage per day. After multiple sets of devices are put into parallel operation, the treatment capacity and operation efficiency of the waste treatment plant can be greatly increased. A series of microwave irradiation cracking garbage devices with different treatment capacities can be formed through the subsequent serial development of microwave irradiation cracking garbage devices to meet the needs of various garbage treatment in urban and rural areas.
Germany: Avoiding garbage has become a public habit
In Germany, there will be a "please tear" sign on the yogurt package, which is not a lottery, but a reminder to separate the plastic cup and a circle of paper packaging outside, so as to better classify plastic waste and paper waste.
Garbage classification has become a part of German life. Most people will consciously classify and put garbage into corresponding dustbins according to paper garbage, biodegradable garbage, glass garbage, electronic garbage, domestic garbage, etc. The education of family, school and society makes children feel that garbage sorting is a natural thing.
Waste classification and recycling not only saves resources and protects the environment, but also promotes the emergence of new business models, such as waste management companies. For example, the garbage disposal fee of a certain community is 1000 euros per year, and the community manager can entrust the garbage management company to find ways to reduce this fee. As a result, the staff of the waste management company will often reclassify some wrongly classified garbage in the community, and regularly provide garbage classification consultation activities to popularize garbage recycling knowledge to residents in the community and help people classify garbage more accurately. Finally, the garbage treatment fee paid by the community as a whole may be reduced to 400 euros, and the resources will be better recycled.
While garbage classification is important, avoiding garbage is fundamental. To this end, the German government launched the "Waste Generation Avoidance Project" in 2013 to reduce waste and protect the environment by means of improving laws and regulations, strengthening scientific research and development, and focusing on publicity and education.
Specific measures for ordinary consumers include encouraging carpooling, reminding them not to buy over packaged products, using less disposable packaging, and not wasting food.
In fact, avoiding garbage generation and recycling are only part of saving and utilizing limited resources. In order to deal with the rising prices of global raw materials and the possible environmental problems caused by the use of raw materials, the German government introduced the "German Resource Efficiency Project" in 2012, with a view to improving the efficiency of resource use, reducing the use of raw materials, and strengthening Germany's economic competitiveness while saving resources and protecting the environment.
According to the document of "German Resource Efficiency Project", Germany has reduced the consumption of raw materials while maintaining economic growth. From 2000 to 2010, the German economy grew significantly, but the demand for raw materials decreased by 11.1%.
However, this is far from enough for Germany. The German government once proposed in the National Sustainable Development Strategy that the utilization rate of raw materials in Germany will double in 2020 compared with 1994. The "German Resource Efficiency Project" is a concrete step taken by Germany to achieve this ambitious goal.
(Author's unit: No. 23 Institute of China Aerospace Science and Industry Corporation) (according to Xinhua News Agency)
