Calculate the mass flow rate of liquid water being sprayed

Question

You may need to use a computer program (such as EES or Matlab) to solve simultaneous equations and develop plots.

Please provide detailed working out, show UNITS.

Question 1

200 kg/hr of an aqueous feed solution containing sodium acetate, water and soluble impurity enters an evaporative crystallizer which operates at 60°C. The mass fraction of soluble impurity in the feed solution is 0.007. On an impurity free basis the feed solution contains 12mol% sodium acetate and 78mo1% water. When the solution is exposed to the low pressure in the evaporator, pure water evaporates (i.e. boils &fir concentrating the remaining solution and causing sodium acetate trihydrate crystals to form. The resulting mixture of crystals and solution are then separated in a filter. The product from the filter contains crystals and 0.06lb solution per lb crystals. A saturated solution of sodium acetate also leaves the filter this is called filtrate). The concentration of impurity in the final product crystal s is 0.185%. The solubility of sodium acetate at 60°C is 51.5g sodium acetate per 100g solution.

a. What is the mass fraction of solium acetate a sodium acetate tri-hydrate crystal?

b. Calculate the Following;

- The mass flow rate of water evaporated.
- The total mass flow rates of the product and filtrate streams.
- The (free) moisture consent of the product Crystals.
- The % recovery of sodium acetate across the entire process.

Question 2

The diagram below illustrates a process for drying and pelletizing macro-algae in preparation for biofuel production. The output from the process is 240 kg/min of product pellets (including water). In order to improve the energy efficiency of the overall process, wet air that leaves the dryer is recycled back to the re-heater., where it is mixed with outside air. The outside air enters the re-heater at 29°C and 0.36 bar gauge pressure. Dry air can be assumed to consist of 21% O₂ and 79% N₂.

(a) What is the total mass flow rate of wet macro-algae fed to the process

(b) If there is no recycling of air, calculate the volumetric flow rate of outside air entering the re-heater.

(c) If 10% of the exiting air is recycled

- Calculate the volumetric flow rate of outside air entering the re-heater.
- Calculate the mass flow rate of dry air (in kg dry airimin) that enters the re-heater in the recycle stream.
- Calculate the mass fraction of water in the air that actually enters the dryer.

(d) Plot the percent exit air recycled (from 0% to 30%) versus!

- The volumetric flow rate of air entering the re-heater.
- The mole fraction of water in the air that actually enters the dryer,

(e) Explain the operational implications of increasing the recycle ratio (energy cost and dryer performance for examples).

Quesbion 3

a) Using a reliable source of climate related information (NASA Bohol,. or MET Office for example), obtain well-labelled graphs which illustrates the relationship between concentration of atmospheric CO₂ and global temperature. Provide the reference details for your graphs.

Make sure to obtain a graph describing this relationship over a relevant timeline i.e. relating to the timescale associated with increasing anthropogenic carbon emissions.

b) Use the graph or graphs to derive an equation relating CO₂ concentration in the atmosphere and atmospheric Temperature.

c) Provide data for the solubility of CO. in sea water (i.e. the ocean) as a function of temperature. This can be in either graphical tabular or in an equation based format.

d) Show the relevant chemical reaction equations, and explain the cause of ocean acidification as ocean temperature increases.

e) Estimate the following quantities (make sure to provide references/dates for your sources and explain your reasoning and calculations clearly).

-Total quantity of CO₂ stored in the ocean.
-Total quantity of CO₂ in the atmosphere.

f) Conceptualize and clearly explain your own well-labelled process diagram to describe the major planetary flows of CO₂ in and out of the atmosphere la photocopied diagram from a website or lecture slide will receive zero marks). Include the following key systems: atmosphere, ocean, anthropogenic sources of CO₂. Neglect ocean sedimentation processes, terrestrial systems (i.e. plants and algae, for example). Provide units for any flows in your diagram.

g) Use your model/process diagram to quantify the effect on atmospheric and ocean temperature over the next ten years given the following scenarios:

1. 5 % annual increase in anthropogenic CO₂ emissions.
2. 0% increase in anthropogenic CO2 emissions.
3. 5 % annual decrease in anthropogenic CO₂ emissions, DELI

h) According to your model, what increase or decrease in CO₂ emissions will keep the Global Temperature Anomaly to below 2^oC.

Question 4

A cogeneration plant connected to a raw sugar mill burns bagasse fibre in excess air to produce heat, which is used to produce steam and also electricity. The combustion process occurs inside a furnace and the combustion gases leaving the furnace are referred to as flue gas.
The wet bagasse fibre has 48.7wt% moisture (Le. water). The composition of dry bagasse fibre is shown in the table below:

Cellulose & Hemi-cellulose	C6H10O5	73.5 wt%
Lignin	C9H10O2	22 wt%
Wax, ash.....etc	Non-carbon	4.5 wt%

*The non-carbon component of dry bagasse fibre contains 16.5% elemental sulphur. The remainder is non-combustable and is referred to as ash.

• 1100 metric ton/hr of wet bagasse is burned in 30% excess air
• The mole ratio of CO, to CO in the furnace exhaust gases is 17.2.
• There is 100% conversion of the bagasse fibre in the furnace.
• 90% of the ash and non-combostables fall through a grate at the base of the furnace and 10% of the ash and non-combustables are entrained with the flue gases (this is called fly-ash).
• The furnace exhaust gas (Le. flue gas and fly ash) leaves the top of the furnace at 300°C.
• Air entering the furnace contains 0.013 kg H₂O per kg dry air. Dry air contains 21% 0, and 79% N2.

a) Calculate the total molar flow rate of air fed the furnace.
b) Calculate the total molar flow rate of the furnace exhaust gases.
c) Calculate the composition (mol%) of the furnace exhaust gases.

The furnace exhaust gas is fed to a wet scrubber to cool the gases and also to remove all of the remaining ash and non-combustables. Exhaust gas enters the wet scrubber were liquid water is sprayed into the exhaust gas. The cleaned and cooled exhaust gas emerges from the wet scrubber at SOE'C with 47.4mol% water vapour and no fly ash. A liquid slurry stream leaves the base of the scrubber containing water and 150ppm fly ash. 90% of the SO, in the exhaust gas that enters the scrubber reacts with liquid water to produce H₂SO₄ which leaves the scrubber in the liquid slurry stream.

d) Calculate the mass flow rate of liquid water being sprayed into the wet scrubber.

e) Calculate the ppm of SO₂in the cleaned exhaust gas.

What proportion of the exhaust gas must be split and bypassed around the scrubber for the cleaned/recombined exhaust gas to be 100 ppm SO₂?