• 2021-10-31 15:19
• 2022-01-10 16:13

# 《大气污染防治原理》作业机翻

## 第1次作业

### Fundamentals of Air Pollution Engineering

##### 2.2

A high-volatile bituminous coal has the following characteristics:

 Proximate analysis近似分析 Fixed carbon 固定碳 54.3% Volatile matter 挥发性物质 32.6% Moisture 水分 1.4% Ash 灰分 11.7% Ultimate analysis终极分析 C 74.4% H 5.1% N 1.4% O 6.7% S 0.7% Heating value 热值 30.7 × 106 J kg-1

It is burned in air at an equivalence ratio of 0.85. 500 × 106 W of electric power is produced with an overall process efficiency (based on the input heating value of the fuel) of 37 %.

(a) Determine the fuel and air feed rates in kg s-1.

(b) Determine the product gas composition.

(c) Sulfur dioxide is removed from the flue gases with a mean efficiency of 80% and the average output of the plant is 75% of its rated capacity. What is the SO2 emission rate in metric tonnes (103 kg) per year?

##### 2.5

Methanol shows promise as an alternate fuel that could reduce nitrogen oxide emissions. The reduction is attributed to lower flame temperatures. Compare the adiabatic flame temperature for combustion of pure methanol at φ = 1 with that of methane (Problem 2.4). Initial fuel and air temperatures are 298 K. The enthalpy of formation of liquid methanol is $\Delta h_f^\circ$ (298 K) = -239,000 J mol-1.

##### 2.6

The bituminous coal of Problem 2.2 is burned in air that has been heated to 590 K. To estimate the maximum temperature in combustion, compute the adiabatic flame temperature for stoichiometric combustion assuming complete combustion. The specific heats of the coal carbon and ash may be taken as $\bar c_{pc}$ = 1810 and $\bar c_{pa}$ = 1100 J kg-1 K-1, respectively. The ash melts at 1500 K with a latent heat of melting of $\Delta \bar\hbar_m$ = 140 J kg-1.

##### 2.9

A fuel oil containing 87% C and 13% H has a specific gravity of 0.825 and a higher heating value of 3.82 × 1010 J m3. It is injected into a combustor at 298 K and burned at atmospheric pressure in stoichiometric air at 298 K. Determine the adiabatic flame temperature and the equilibrium mole fractions of CO, CO2, H2, H2O, O2, and N2.

### Air Pollution Control Engineering

##### P66, 1

The range of droplet sizes in a cloud was determined to be as follows:

Range of drop diameter -microns

Number of drops

5-84
8-116
11-1415
14-1724
17-2024
20-2312
23-264
26-294
29-324
32-383

a. Determine the number median diameter.

b. Determine the mass median diameter.

c. Determine the Sauter mean diameter.

d. What weight fraction of the sample is represented by drops greater than 20 μm in diameter?

e. What is the population density of the 20-23 μm grade?

20-23 μm等级的人口密度是多少？

f. Can the distribution be reasonably well described as log-normal? (Hint: try plotting Δn/Δln dp vs ln dp; also try the upper-limit function). If so, find the two constants for the distribution.

##### P66, 5

The spray from a certain nozzle gave a drop-size distribution which was log-normal, with an AMD of 240 microns and a standard geometric dispersion of 2.00. For this spray:

a. What fraction of the total surface would be on drops between 100 and 200 microns in diameter?

b. What is the value of the “surface to diameter” mean $\bar D_{1,1}$?

“表面对直径”的值是什么意思$\bar D_{1,1}$？

c. What is the value of the maximum population density?

d. At what size does this value occur?

##### P133, 1

The particle size distribution of a certain dust, as obtained by an analysis conducted partly by a Coulter Counter and partly by an Anderson Impactor, may be represented by two straight lines on a log-probability plot. These lines intersect at 5.5 μm and 19.5% finer-than, with the Coulter portion having a σg = 0.205, and the Anderson portion a σg = 11.1, with the Anderson covering the finer range. This dust is to be collected by a device which has a grade efficiency performance given by the following equation:

$n_{M} = 1 - \exp(-2(1.28 \times 10^{-2} d_p^2)^{0.315})$

where dp is in microns. For this operation, find:

a. the “cut diameter”;

“切割直径”；

b. the overall efficiency;

c. the particle size distribution of the dust emitted;

d. the rate of emission, per 100 kg of dust fed.

##### P133, 4

The grade efficiency of a certain gravity (settling chamber) collector was found to be 20% on particles of a certain size and 81% on particles twice as large. Assuming the particles obey Stokes Law, what type of model might represent this collector performance? Would your answer be the same if the grade efficiencies were 25% and 50% respectively?

##### P133, 5

The power consumption of a certain collector was measured as 15 kW. It was processing a stream of gas having an average molecular weight of 32, at 300 ℉ and 15.2 psia, through a duct 18’’ by 36’’ in cross-section at an inlet velocity of 50 ft/sec.

Find: (a) the pressure drop across the collector;

(b) the number of inlet velocity heads of frictional energy loss.

(b) 摩擦能损失的入口速度头数。

##### P133, 7

It has become necessary to control the emission of cement dust from the kiln of a Portland Cement plant in which the operating conditions are as follows: temperature = 250 ℉; pressure = 1 atm; feed rate to kiln = 5 tons/hr; emission rate of dust (uncontrolled) = 230 lb/ton of feed; air flow = 159,600 acf/ton of feed. The dust may be regarded as equivalent of Stairmand Fine. The emission regulations are given in Chapter 1.

a. Select some possible kinds of collection equipment which might be considered in order to meet this requirement. Indicate their relative costs and power consumption.

b. What will be the grain-loading in the feed to the collection system?

c. Could a cyclone collector be used in any way? If so, or if not, assuming the inlet duct to be 2.28 ft by 1.09 ft, and the value of N = 9 inlet velocity heads, estimate the pressure drop across the cyclone, and the power consumption for the operation.

## 第2次作业

### 旋风除尘器

##### 1

(a) A certain cyclone installation is collecting particles of sp.gr. = 2.5 using an inlet velocity of 50 ft/s. What inlet velocity would be required to collect particles of sp.gr. = 1.5 with the same grade-efficiency? How will the pressure drop compare with the original value?

(a) 某旋风分离器装置使用50 ft/s的入口速度收集sp.gr. = 2.5的颗粒。收集sp.gr. = 1.5且具有相同品位效率的颗粒所需的入口速度是多少？压降与原始值相比如何？

(b) The cut-diameter for a Swift high-efficiency design cyclone operating under a certain set of conditions is 2.0 μm and the pressure drop is 3.0'' H2O. What would be the cut-diameter and the pressure drop for a Stairmand design of the same diameter D, operating at the same flow rate, temperature, grain-loading, etc.?

(b) 在特定条件下运行的快速高效设计旋风分离器的切割直径为2.0 μm，压降为3.0'' H2O。在相同流速、温度、谷物负载等条件下，相同直径D的楼梯设计的切割直径和压降是多少？

##### 2

A cyclone designed to operate at 20 ℃ with a flow rate of 10,800 std. cu.ft./min of air, collecting solid particles of 1.5 gm/cm3 density, has a cut-diamter of 1.96 μm. Estimate the collection grade-efficiency of particles 1.96 μm if this same cyclone were operated at 200 ℃ at a flow rate of 5000 scfm, collecting the same material. The cyclone is of high-efficiency Stairmand configuration and is 5 ft in body diameter.

### 电除尘器

##### 1

Using the conditions and values specified for Eqn. (7.9), together with appropriate values for Ci calculate values of the size-dependent term Ciqi*/dpi in Eqn. (7.3) after 1 sec for particle sizes in the neighborhood of 0.2 μm. Show that this term goes through a minimun value. Compare the particle size at which this minimum occurs with that obtained from Eqn. (7.13).

##### 4

Refer to Example 1 in this chapter:

(a) What is the value of the effective migration velocity (or precipitation rate parameter)?

(b) What is the “cut” diameter?

“切割”直径是多少？

(c) What value of a “mean” particle size could be used to represent the overall performance? Does this correspond to any of the “means” defined in Chapter 2? How does it compare with Cooperman's tmean given by (7.22) and (7.23)?

“平均”粒径的什么值可以用来表示总体性能？这是否符合第2章中定义的任何“方法”？它与（7.22）和（7.23）给出的库伯曼tmean相比如何？

(d) Estimate the value of the overall collection efficiency if the rate of gas flow were to double during operation.

##### 7

The fly-ash from a pulverized coal fired furnace has a particle-size-distribution such as given in Feldman's table just below Eqn. (7.19), and a density of 2.5 gm/cm3, It is emitted at the rate of 170 lb/ton of coal fired in a flue gas stream (Mol. Wt. = 28.1) of 14.7 × 106 cu.ft./hr at 300 ℉ and 1 atm. A collection system is to be designed to meet the emission regulation of 0.10 lb/million BTU. The coal used has a heating value of 12,800 BTU/lbm and is fired at the rate of 35 tons/hr. Consider the use of an electrostatic precipitator (either with or without a primary collector ahead of it) for this purpose. Estimate the collecting surface required and propose an arrangement for the plates: number in parallel, spacing, height, length and number of compartments.

### 过滤器

##### 1

(a) Repeat the calculations for the conditions of the example of fiber-bed filtration given in the text, except use velocities of 60 fpm, and of 80 fpm. Note the interplay between the face velocity values and L, A, and ΔP for each filter.

(b) For the conditions of this same example, assume that there is also present an image force brought about by the presence of 90 electronic charges per particle, and that the dielectric constant of the fibers is rather large. Estimate what effect this would have upon the filter dimensions for the case of 40 fpm face velocity.

(c) Again with reference to the same example, how would the results of the original case for 100 fpm be affected if the required efficiency were to be 95%?

##### 2

A dust-laden air stream of 10,000 acfm at 70 ℉ and dust concentration of 2.3 gm/m3 is passed through a fabric filter consisting of 49 bags in parallel, each bag 20 ft long and 1 ft in diameter. Cleaning is by mechanical shaking of all the bags at the same time. Tests indicate that the pressure drop is 3.28'' H2O twenty minutes after shaking, and 3.53'' H2O forty minutes after shaking. Determine:

(a) air/cloth ratio in use during filtration;

(b) the values of SE and K2;

SE和K2的值；

(c) time required to reach a ΔP = 4.0'' H2O；

(d) amount of dust collected when ΔP reaches 4.0'';

ΔP达到4.0''时收集的粉尘量；

(e) the time required to reach ΔP of 4.0'', if an identical arrangement of 49 bags is added in parallel with the present arrangement.

##### 4

Refer to Problem 7 of Chapter 7. For the conditions stated there, consider the design of a baghouse filter system to collect the fly-ash. Assume that the fabric will be fiberglass. Make a preliminary design and compare it with that for the electrostatic precipitator design done for that problem.

### 湿式洗涤器

##### 2

A gravity spray tower 3 m high is operating at a liquid-to-gas ratio of 1 l/m3 with a drop diameter of 400 μm. The gas velocity is 0.1 of the drop terminal velocity which is 157 cm/s. The operation is at 20 ℃. What is the grade efficiency for particles of 1 μm diameter, having a density of 2.0 gm/cm3?

3米高的重力喷雾塔以1 l/m3的液气比运行，液滴直径为400 μm。气体流速为滴头流速的0.1，即157 cm/s。操作温度为20 ℃。直径为1 μm、密度为2.0 gm/cm3的颗粒的分级效率是多少？

##### 4

A Venturi scrubber is to be designed to collect dust from an asphalt stone drier. The dust has a mass median diameter of 1.8 μm and a density of 2.6 gm/cm3. The uncontrolled emission rate is 2310 kg/hr, but state regulations require that this be reduced to a maximum of 25 kg/hr. The air flow is 20,000 acfm at 250 ℉. No additional data are available. Assuming a throat velocity of 150 ft/s, make a preliminary determination of the necessary L/G value, and of the maximum pressure loss in the throat. Discuss the additional data and calculations which would be required to make a final design of the Venturi.