According to statistics from the national environmental protection department, the total amount of industrial solid waste nationwide (excluding township and village enterprises)
is 650 million tons per year, and the comprehensive utilization rate is only about 29. The cumulative accumulation amount It was 6.64 billion tons, 5.5 tons per capita, covering an area of ??about 55,000 hectares. In 1989, the country discharged 16.97 million tons of chemical waste residues and 900,000 tons of radioactive waste residues. Most of them have not been harmlessly treated and scientifically disposed of, and the growing amount of toxic
hazardous waste has constituted a potential danger. According to statistics, urban domestic waste across the country accounts for 6 to 7 per year
has grown at a rate of 60 million tons in 1996, but the average harmless treatment rate of garbage is less than 5. A large amount of untreated industrial waste and urban garbage are piled in suburban areas and other places, forming a The siege situation has become a serious source of secondary pollution. In 2000, the total amount of industrial solid waste in my country will increase to about 700 million tons.
Urban life is currently widely used at home and abroad The main garbage disposal methods include sanitary landfill, high-temperature composting and incineration. The proportions of these three main garbage disposal methods vary depending on factors such as geographical environment, garbage composition, and economic development level. Table 2-1 shows the three types. Comparison of treatment methods.
Table 2-1 Comparison of three garbage treatment methods
Same as left
The pre-treatment process can recycle some raw materials, but it depends on the content of the garbage. The proportion of recyclable materials.
There are no examples of on-site sorting and recycling, but it is potentially possible.
Resource recovery
Moderate
Relatively High
Low
Construction investment
It is difficult to establish a stable compost market.
Can generate heat or electricity.
Recyclable biogas power generation.
Product market
Non-compost materials need to be landfilled, which is 20~25% of the initial amount.
Only The residue needs to be landfilled, which is 10. of the initial amount.
None
Final disposal
From the perspective of harmlessness, the biodegradable organic matter in the garbage ≥ 10. From the perspective of fertilizer efficiency, it should be gt; 40.
When the low calorific value of garbage is 3300kJ/kg, there is no need to add auxiliary fuel.
Inorganic matter gt; 60
Moisture content 0.5t/d
Applicable conditions
Easy, only need to avoid densely populated areas, the odor influence radius is less than 200m, and the transportation distance is moderate.
Easy, can be built close to the urban area, and the transportation distance is relatively short
More difficult, the terrain and geological conditions must be considered, and surface water and groundwater pollution must be prevented. Generally, it is far away from the urban area and the transportation distance is long.
p>Site selection
Medium
Small
Large
Occupied area
Reliable, domestic Have considerable experience
Reliable
Reliable
Technical reliability
Good
Good
Better, pay attention to fire prevention
Operation safety
Composting
Incineration
Sanitary landfill
Content
Influence of three methods
Continued Table 2-1
The content of heavy metals in compost products needs to be controlled.
None
p>Limited to the landfill area.
Soil pollution
There is a slight smell, and the possibility of pollution indicators is unlikely.
It can be controlled, but the second Measures must be taken to control trace amounts of highly toxic substances such as Doxlin.
Yes, but measures such as covering and compaction can be used to control them
Air pollution
Heavy metals, etc. It is possible to contaminate groundwater with compost products
There are no organic matter and other pollutants in the ash, and only solidification and other measures need to be taken during landfill to prevent pollution.
It is possible, although anti-seepage can be taken measures, but leakage may still occur.
Groundwater contamination
>
The landfill of non-compost materials is similar to the sanitary landfill.
There is no such thing in the treatment plant area. When the furnace ash is landfilled, the possibility of surface water pollution is smaller than that of landfill.
Possible, but measures can be taken to reduce the possibility.
Surface water pollution
Composting
Incineration
Sanitary Landfill
Contents
Technical Countermeasures
The current technical countermeasures for urban waste treatment in my country are: focusing on sanitary landfill and high-temperature composting technology, and promoting Cities, especially economically developed coastal areas, have developed incineration technology according to the conditions. In recent years, cities have begun to carry out basic and applied research on waste incineration treatment, and have developed NF series reverse combustion type, RF series pyrolysis type, and HL series rotary type. Small garbage incinerators and a number of special incinerators for hospital garbage, and a number of small and medium-sized urban simple incineration plants (stations) were built. In 1985, Shenzhen introduced a complete set of incineration technology and equipment from Japan's Mitsubishi Company and built my country's first large ( 300t/d) modern integrated waste incineration and power generation treatment plant, laying the foundation for the localization of urban waste incineration equipment in China.
Shanghai Pudong Waste Incineration Plant
1000TD bag dust collector
The largest waste incineration plant under construction in my country
Waste incineration plant
Waste recycling process
Future outlook
my country Municipal waste treatment technology has achieved new breakthroughs
The Solid Waste Treatment and Utilization Committee of the China Environmental Protection Industry Association recently conducted a research on the medical waste and domestic waste heat treatment technology developed by Longde Environmental Protection Technology Co., Ltd.
in Baotou City. The solution and related equipment underwent a technical review. Experts from Tsinghua University, Chinese Academy of Sciences and other units unanimously positioned this technological achievement as "the first in China".
In order to solve the problem of urban Regarding the garbage problem, Tianjin University has conducted in-depth research on garbage pyrolysis technology and obtained a number of national patents. On this basis, Longde Environmental Protection Technology Company has conducted further research on this technology and equipment. and development,
successfully integrated this technology with gasification technology, carbon dioxide reduction and related catalytic combustion technology,
more effectively controlled pollution and made organic Waste materials are fully converted into usable resources. In 2002, Baotou City Environmental Sanitation Industry
Company introduced this technology and related equipment, built a systematic garbage disposal site, and regenerated waste resources
Promising results have been achieved in terms of utilization. Experts participating in the review believe that using this pyrolysis method to treat medical and
domestic waste is in line with the principles of "reduction, harmlessness, and resource utilization" "The development direction of solid waste treatment has the advantages of high energy recovery rate, low secondary pollution, and good comprehensive economic benefits. It has broad development prospects. At the same time, related complete sets
The equipment has reasonable design, high automation level and small area, which meets the conditions for engineering application and market transformation.
Garbage treatment technology in French cities
France is developing new cities Garbage treatment technology to replace the incineration and landfilling of domestic waste. Using methanation to treat organic waste and sorting packaging materials using mechanized methods are beneficial to the environment and the environment. Economically speaking, they are all very promising methods. The characteristic of methanation treatment is to isolate organic matter from the air and accelerate degradation in an anaerobic environment. Before methanation treatment, the garbage must be treated p>
Carrying out sorting, methanation and finishing of compost. The characteristic of the process technology developed and patented by Valorga International Engineering Company is that during the operation of the reactor Ferment organic matter. There are 300 openings on the base of the reactor. Pressurized biogas (8 atmospheres) is injected from these openings. Biogas is produced by the fermentation of garbage. The reactor stirs the garbage and mixes it evenly.
During the day, the garbage is continuously transported to the bottom of the reactor. Driven by biogas, the garbage has to be bypassed
Made of cement The inner wall of the reactor, then
Only then can it reach the outlet. This process allows the garbage to stay in the reactor
for 3 weeks until it is completely degraded. The biogas produced during the bacterial fermentation
is at the outlet It is collected and stored everywhere and can be reused in the form of heat energy and power generation.
Smoke pollution in my country
my country is a country whose energy structure is dominated by coal burning, and air pollution is Soot pollution, dust
dust, sulfur dioxide (SO2), and nitrogen oxides (NOx) are the main pollutants in our country's atmosphere. In the initial development of industrialization in the 1950s, In the second stage of industrialization in the 1960s and 1970s, coal consumption in the country was 20-100 million tons, and sulfur oxide emissions were 500,000-2 million tons.
The amount is 10-450 million tons, and the emission of sulfur dioxide is 3-7 million tons; in the third stage of industrialization since the 1980s, the annual coal consumption has reached 800 million tons. The emission of sulfur dioxide is 900-1500
million tons; at the same time, a considerable amount of nitrogen oxide is produced during the coal burning process, such as the NOx emissions from my country's coal-fired power plants in 2000
The amount reached 2.9 million tons. Therefore, the characteristics of my country's energy structure have led to more heavy corrosion
situations, resulting in acid rain and other pollution situations, especially in coal-fired power plants, for sulfur dioxide or nitrogen
The prevention and control of oxides is imperative.
Traditional desulfurization technology
Currently, the application rate of various domestic flue gas desulfurization technologies is as high as 85%
is the wet limestone/gypsum method technology and equipment introduced from abroad. The lime-gypsum method uses limestone or lime slurry to absorb SO2 in the flue gas. It is a wet scrubbing method. The by-product of this method is gypsum (CaSO4·2H2O) .
The two steps of SO2 absorption and oxidation are completed in the main absorption tower, which are completed in the absorption tower and tower kettle respectively.
(1) Absorption (2) Oxidation
p>CaO H2O→Ca(OH)2
2 CaSO3·1/2H2O O2 3H2O→2 CaSO4·2H2O
Ca(OH)2 SO2→CaSO3·1 /2H2O 1/2H2O Ca(HSO3)2 1/2O2 H2O→CaSO4·2H2O SO2↑
CaCO3 SO2 1/2H2O→CaSO3·1/2H2O CO2↑
CaSO3·1 /2H2O SO2 1/2H2O→Ca(HSO3)2
Add organic additives to the absorption solution to prevent equipment from scaling. The final product of this method is gypsum. The simple limestone/gypsum method does not add any addition to the final product. Recycle and discard directly; post-processing can also be used to separate the finished gypsum for recycling.
Disadvantages
Although it plays a certain role in reducing sulfur dioxide pollution in industrial flue gas, it also By-products such as sulfated gypsum are produced. For every ton of sulfur dioxide processed by wet limestone/gypsum desulfurization equipment, 2.7 tons of desulfurized gypsum are produced. As the installed capacity of my country's thermal power plants increases year by year, it is expected that by 2010, the accumulated desulfurized gypsum and other The by-product gypsum will exceed 100 million tons. Although relevant manufacturers of imported equipment are keen to promote the reuse of desulfurization gypsum, which can replace naturally mined mineral gypsum. In fact, the utilization of desulfurization gypsum is only a theoretical statement. my country’s mineral Gypsum resources are quite abundant. This kind of ore is easy to mine, cheap and high-quality. However, the compressive strength and tensile strength of desulfurization gypsum cannot compete with mineral gypsum. No one is willing to use it, and most of it is discarded. Abandoned desulfurization gypsum Like piles of "snowy mountains", the "acidic substances" that volatilize after being exposed to the sun have aggravated the threat of "acid rain." Moreover, the desulfurization gypsum washed by rain will pollute surface water and groundwater. Therefore, the old The sulfur dioxide pollution in the flue gas has produced new secondary pollution of desulfurized gypsum. Secondly, adjust the
Investigations have shown that if all the sulfur dioxide produced is treated by the wet limestone/gypsum method, tens of millions of tons of new carbon dioxide will be added to our country every year. The current total annual emissions of carbon dioxide in the world have far exceeded that of nature through plant photosynthesis. and the ability of seawater to absorb and dissolve. Excessive deposition of carbon dioxide in the atmosphere will cause the earth's surface temperature to continue to rise. Research shows that once carbon dioxide is emitted into the atmosphere, it can survive for up to 200 years. Long-term excess carbon dioxide accumulates at low altitudes It will increase the atmospheric concentration, hinder the dissipation of the earth's heat, cause reduced rainfall, dry up rivers, climate warming, environmental deterioration, destroy the balance pattern of the entire nature, and cause disasters such as droughts and floods. my country's total annual carbon dioxide emissions already account for the world's total. 13.2% of the total emissions. As early as 1997, my country participated in the Kyoto Protocol and committed that by 2010, the amount of carbon dioxide and other six greenhouse gases that our country would emit would not only not increase, but would also be reduced by 5.2% compared to 1990. This time limit requirement is quite urgent. The sulfur dioxide pollution in the old flue gas has been controlled, and the emission of carbon dioxide in the atmosphere has been added, resulting in new pollution.
Alkali liquor/spent alkali liquor flue gas desulfurization process
Alkali solution method is one of the more commonly used desulfurization methods. This method uses alkaline solution to absorb SO2 in the flue gas to generate HSO32-, SO32- and SO42-. The reaction equation is as follows:
SO2 OH-→HSO3-
HSO3- OH-→SO32- H2O
Oxidation part:
HSO3- 1/2O2→SO42- H
SO3- 1/2O2→SO42-
Alkaline solution can use sodium alkali (mainly sodium carbonate, sodium hydroxide, etc.; sodium alkali has high solubility and absorption rate and is not scale, not easy to block.), or there are various available waste alkali solutions in the factory, and the insufficient part is replenished (usually sodium alkali), which can make full use of the original resources in the factory to achieve the purpose of treating waste with waste.
Ammonia process
The ammonia process uses ammonia to wash waste gas containing SO2 to form an absorption liquid system of (NH4)2SO3-NH4HSO3-H2O. (NH4)2SO3 in this solution has a strong effect on SO2 It has good absorption capacity and is the main absorbent in the ammonia method. The ammonia method is a relatively mature method among flue gas desulfurization methods and was earlier used in industrial engineering. This method has low desulfurization costs and the ammonia can remain in the product. It is provided in the form of nitrogen fertilizer, so the use value of the product is high, but the source of ammonia is greatly restricted by region and production industry. Despite this, the ammonia method is still a promising method to control low-concentration SO2.
Integrated process of wet flue gas desulfurization and dust removal
The integrated process of wet flue gas desulfurization and dust removal is designed based on the unique excellent performance of the cyclone plate tower and combined with the actual situation of domestic enterprises. An efficient and economical FGD process. The dust removal efficiency is ≥98 and the desulfurization rate is 75-90, which meets the current domestic governance requirements; the specially designed combined mist removal device prevents the fan from carrying water.
This method generally uses lime As absorbent, or use carbide slag and other alkaline waste residues. The reaction principle is as follows:
CaO H2O→Ca(OH)2
Ca(OH)2 SO2→CaSO3· 1/2H2O 1/2H2O
CaCO3 SO2 1/2H2O→CaSO3·1/2H2O CO2↑
CaSO3·1/2H2O SO2 1/2H2O→Ca(HSO3)2
The desulfurization liquid is ash settled in the comprehensive circulation tank, replenished with alkali and then recycled.
The by-products obtained by this method can be recycled or discarded. Limestone sources are widely available, raw materials are easy to obtain, and the price is low , the governance effect is good, and it has been successfully implemented in many domestic enterprises.
Comparison of various processes