Here, we see a belt conveyor transporting coal to the furnace where it is burned on a
traveling grate stoker. Air for combustion is supplied by a bellows.
Remember, when you burn coal you are really promoting a chemical reaction – a chain
reaction. When coal is heated to a high enough temperature in the presence of air, the
carbon in the coal combines with oxygen of the air to form either carbon dioxide (CO2) or
carbon monoxide (CO). These, of course, are both gases. Which gas is formed depends
upon the quantity of oxygen present. The CO means that the coal is only partially burned;
the CO can be combined with more oxygen to form CO2.
In burning coal we do not want CO because that means the coal is only partially burned:
there is still energy left in the gas, energy that we can recover if we can burn it to CO2.
It is desirable, in the operation of our boiler furnaces, always to get as much CO2 as we
can because in that way we get all the heat out of the fuel.
Now we can obtain the CO2 by supplying more air to the fuel as it is burning. But, we do
not want to supply too much air because if we do, we will be supplying more oxygen than
is actually needed to combine with carbon, and this excess oxygen will play no part in the
combustion process. Not only will it play no part but it will actually detract from the
efficiency by absorbing heat that otherwise could be used to heat the water in the boiler.
In actual practice it is not possible to supply exactly the required amount of air, so somewhat
more than enough is supplied. This is commonly referred to, as excess air.
So, in the process of combustion, we are dealing with chemistry. Thus, it involves knowledge
of the composition of the coal, its physical condition, its behavior under various
conditions of temperature, moisture, etc. Actually, the combustion of coal is a very complex
process requiring a good knowledge of both physics and chemistry. In a large plant it
involves a major problem in materials handling – fuel, ashes, air and flue gas. Remember,
in burning coal, you have to supply about 17 pounds of air for each pound of coal used
Here, we see a belt conveyor transporting coal to the furnace where it is burned on atraveling grate stoker. Air for combustion is supplied by a bellows.Remember, when you burn coal you are really promoting a chemical reaction – a chainreaction. When coal is heated to a high enough temperature in the presence of air, thecarbon in the coal combines with oxygen of the air to form either carbon dioxide (CO2) orcarbon monoxide (CO). These, of course, are both gases. Which gas is formed dependsupon the quantity of oxygen present. The CO means that the coal is only partially burned;the CO can be combined with more oxygen to form CO2.In burning coal we do not want CO because that means the coal is only partially burned:there is still energy left in the gas, energy that we can recover if we can burn it to CO2.It is desirable, in the operation of our boiler furnaces, always to get as much CO2 as wecan because in that way we get all the heat out of the fuel.Now we can obtain the CO2 by supplying more air to the fuel as it is burning. But, we donot want to supply too much air because if we do, we will be supplying more oxygen thanis actually needed to combine with carbon, and this excess oxygen will play no part in thecombustion process. Not only will it play no part but it will actually detract from theefficiency by absorbing heat that otherwise could be used to heat the water in the boiler.ในทางปฏิบัติจริง มันไม่สามารถจัดหาว่าจำนวนเงินที่ต้องของอากาศ ค่อนข้างมากมากกว่าพอมา ซึ่งโดยทั่วไปเรียกว่า อากาศส่วนเกินดังนั้น ในกระบวนการเผาไหม้ เรากำลังเผชิญกับเคมี ดังนั้น มันเกี่ยวข้องกับความรู้ขององค์ประกอบของถ่านหิน สภาพทางกายภาพ การทำงานต่าง ๆ ภายใต้เงื่อนไขของอุณหภูมิ ความชื้น เป็นต้น จริง การเผาไหม้ของถ่านหินจะซับซ้อนมากกระบวนการที่ต้องใช้ความรู้ฟิสิกส์และเคมี ในการปลูกมันปัญหาสำคัญในวัสดุที่เกี่ยวข้องกับการจัดการ – ก๊าซเชื้อเพลิง ขี้เถ้า อากาศ และชำระล้างกรด จำในการเผาไหม้ถ่านหิน คุณจะต้องใส่ประมาณ 17 ปอนด์ อากาศสำหรับแต่ละปอนด์ที่ใช้ถ่านหิน
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