CHƯƠNG 13. XỬ LÝ CHẤT THẢI RẮN

High calorific waste Medical waste incinerators  The medical waste incinerator is a high temperature kiln.. To be sure of total desinfection, the temperature in the combustion chamber

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

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

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

High caloric waste

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Rotary kiln

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

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

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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