An ultimate analysis of a coal is a series of operations that yields the percentages by mass of carbon, hydrogen nitrogen, oxygen and sulfur in the coal. The heating value of a coal is best determined in a calorimeter, but it may be estimated with reasonable accuracy from the ultimate analysis using the Delong formula: HHV (kJ/kg) = 33,801 (C) + 144,158 [(H) – 0.125 (0)1 + 9413 (S) where (C), (H), (O), and (S) are the mass fractions of the corresponding elements. The 0.125 (O) term accounts for the hydrogen bound in the water contained in the coal. (a) Derive an expression for the higher heating value (HKV) of a coal in terms of C, H, O, and S. and compare your result with the Delong formula. Suggest a reason for the difference.
(b) A coal with an ultimate analysis of 75.8 wt% C, 5.1% H, 8.2% 0. 1.5% N, 1.6% S. and 7.8% ash (noncombustible) is burned in a power plant boiler furnace. All of the sulfur in the coal forms SO2. The gas leaving the furnace is fed through a (all stack and discharged to the atmosphere. The ratio F (kg SO2 in the stack gas/kJ heating value of the fuel) must be below a specified value for the power plant to be in compliance with Environmental Protection Agency regulations regarding sulfur emissions. Estimate 4, using the Delong formula for the heating value of the coal,
(c) An earlier version of the EPA regulation specified that the mole fraction of SO2 in the stack gas must be less than a specified amount to avoid a costly fine and the required installation of an expensive stack gas scrubbing Unit. When this regulation was in force, a few unethical plant operators blew clear air into the base of the stack while the furnace was operating. Briefly explain why they did so and why they stopped this practice when the new regulation was introduced.

Uit hard

Infrared sensor is most used sensor in wireless technology where remote controlling functions and detection of surrounding objects/ obstacles are involved. this post will discuss about what is infrared sensor, its working principle, how it works, types, applications, advantages and disadvantages. what is infrared sensor

ir sensor is a simple electronic device which emits and detects ir radiation in order to find out certain objects/obstacles in its range. some of its features are heat and motion sensing.

ir sensors use infrared radiation of wavelength between 0.75 to 1000µm which falls between visible and microwave regions of electromagnetic spectrum. ir region is not visible to human eyes. infrared spectrum is categorized into three regions based on its wavelength i.e. near infrared, mid infrared, far infrared.

wavelength regions of infrared spectrum

near ir – 0.75µm to 3 µm
mid ir – 3 µm to 6 µm
far ir – > 6 µm
1 introduction to infrared sensor

fig. 1 – introduction to infrared sensor

working principle of infrared sensor

infrared sensors works on three fundamental physics laws:

planck’s radiation law: any object whose temperature is not equal to absolute zero (0 kelvin) emits radiation.
stephan boltzmann law: the total energy emitted at all wavelengths by a black body is related to the absolute temperature.
wein’s displacement law: objects of different temperature emit spectra that peak at different wavelengths that is inversely proportional to temperature.
key elements of infrared detection system

the key elements of infrared detection system are:

ir transmitter

ir transmitter acts as source for ir radiation. according to plank’s radiation law, every object is a source of ir radiation at temp t above 0 kelvin. in most cases black body radiators, tungsten lamps, silicon carbide, infrared lasers, leds of infrared wavelength are used as sources.

transmission medium

as the name suggests, transmission medium provides passage for the radiation to reach from ir transmitter to ir receiver. vacuum, atmosphere and optical fibers are used as medium.

ir receiver

generally ir receivers are photo diode and photo transistors. they are capable of detecting infrared radiation. hence ir receiver is also called as ir detector. variety of receivers are available based on wavelength, voltage and package.

ir transmitter and receivers are selected with matching parameters. some of deciding specifications of receivers are photosensitivity or responsivity, noise equivalent power and detectivity.

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