Chapter 13 Xử lý chất thải rắn

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•Composting

•Incineration

•Landfill

•Recycling

Compost Organic matter that has been decomposed and recycled as a

fertilizer and soil amendment.

The process: simply piling up waste outdoors and waiting for the materials to break down between 5-6 weeks or even more.

Measured inputs of water, air and carbon- and nitrogen-rich materials.

Worms and fungi further break up the material.

Aerobic bacteria manage the chemical process by converting the inputs into heat, CO2 and NH4

+. The NH4+ is further converted by

bacteria into plant-nourishing NO2- and NO3

- through the process of nitrification.

Organic ingredients intended for composting can alternatively be used to generate biogas through anaerobic digestion.

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Anaerobic digestion Bacterial hydrolysis of the input materials to break down insoluble

organic polymers, such as carbohydrates.

Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids

Acetogenic bacteria then convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide.

Methanogens convert these products to methane and carbon dioxide

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Anaerobic digestion-Residence time

Single-stage thermophilic digestion, residence times may be in the region of 14 days

Two-stage mesophilic digestion, residence time may vary between 15 and 40 days

UASB digestion, hydraulic residence times can be 1 hour to 1 day, and solid retention times can be up to 90 days

Continuous digesters have mechanical or hydraulic devices, depending on the level of solids in the material, to mix the contents, enabling the bacteria and the food to be in contact

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Incineration

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low calorific value

high calorific value

High calorific waste

Medical waste incinerators

The medical waste incinerator is a high temperature kiln.

Biohasardous waste such as medical and hospital waste can only be totally desinfected by thermal treatment. To be sure of total desinfection, the temperature in the combustion chamber has to exceed 1000 degrees

Rotary kiln incinerator is the most used technology for the destruction of medical waste, because of its versatility,its continuous operation and because of its self cleaning properties (no need for inside cleaning)

Industrial and hazardous waste incinerators

Industrial wastes are mostly highly calorific and,as such, generate very high temperatures (> 1100 degr.C) while being oxidised.. Those high temperatures can only be safely handled in a rotary kiln incinerator.

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High caloric waste

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Rotary kiln

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Rotary kiln

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moving grate incinerator Primary combustion air is supplied through

the grate from below =>cooling the grate . Cooling is important for the mechanical strength of the grate, and many moving grates are also water-cooled internally.

Secondary combustion air is supplied into the boiler at high speed through nozzles over the grate. It facilitates complete combustion of the flue gases by introducing turbulence for better mixing and by ensuring a surplus of oxygen.

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Fluidized incinerator

Supplying the first air to the fourth airs (1,2,3,4) into the incinerator from optimal positions => oxidation of Fuel NOx is restrained

Long residence time of combustion gas in the temperature range of 800 to 900°

C => suppress NOx, CO, dioxine, and dissolution of dioxine is proceeded

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10. Fuel input

Đốt nhiệt phân

Nhiệt phân là quá trình phân hủy chất thải rắn do nung nóng trong điều kiện không có oxy

Nhiệt phân bằng hồ quang-plasma: thực hiện đốt ở nhiệt độ cao 10.0000C để tiêu hủy chất thải có tính độc cực mạnh. Sản phẩm là H2, CO, khí axit, tro

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Quá trình nhiệt phân được tiến hành trong buồng đốt sơ cấp của lò nhằm chuyển các thành phần ở thể rắn và lỏng của chất thải thành thể khí (HC, CO, H2…) nhờ nhiệt cung cấp từ mỏ đốt nhiên liệu. Quá trình nhiệt phân được thực hiện trong điều kiện thiếu oxy và ở nhiệt độ 500-600oC.

Buồng đốt thứ cấp phân huỷ các chát ô nhiễm ở nhiệt độ cao (trên 1100oC). Toàn bộ lượng không khí cấp bổ sung, những chất cháy thể khí từ buồng sơ cấp sang, kể cả các chất ô nhiễm hữu cơ mạch vòng như dioxin và furois sẽ bị đốt cháy hoàn tòan tạo thành CO2 và H2O.

Đốt nhiệt phân

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Gassification

Converting organic materials into CO, H, CO2, and CH4 through really high temperatures without combustion (burning)

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Landfill design

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Landfill

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