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We employ many millions of microorganisms for controlling the plant cooking odors. We house them in a medium of shredded trees and feed them lots of food laden air. They ask little and work hard. Two things they ask for are moist surroundings and a comfortable pH. We try to keep them happy. We spray water on them and have been sprinkling lime to raise the pH back up near 7-8 SU. To reduce our effort we decided to inject NaOH into the spray water.
We have learned some things which may interest you.
17Jan1 we piped up a diaphragm pump to pump sodium hydroxide. After
pumping about 90 gallons over a week, the level in the tank quit
dropping. Flooded suction. 50% NaOH. Checked the pump: check valves
in correctly and free. Diaphragm OK and strokes as expected. Discharge
pipe clear. Ran pump with discharge pipe disconnected -- pump produced
a pulsing fountain about 3/4" high. Still, after hooking discharge pipe
back up, no indication of pumping.
The identical sulfuric acid pump is working just fine.
Is viscosity the problem? What have I overlooked? Intend to insert a
pressure gage and maybe a drawdown and maybe some clear tubing.Installed gage in discharge line. Zero. New spare pump arrived. Swapped
it. Gage read up to 6 psi, then dropped to zero.
Washed suction piping with safety rinse water and pressure went up to 8
and fluctuated 1 psi as pulsed by pump.
Seems like some fitting is leaking. No indication of NaOH dripping.
Pump seems to lose suction. Too many symptoms.
Applied pressure [some] at injection point (increasing back pressure).
Gage now reads over 20 ... pulsing in time with pump.
Level in storage tank has dropped.We had pumped the tank down to install a cutoff valve in order to work
on the pump. So when I refilled the tank to near "flooded suction
level' the new pump began working much like I expected the pump to
work. I guess the other pump has a problem?
Tried again. While pumping to an open pipe, noticed an inch to one and a
half inch long slivers of glass looking shards oozing out. Flexible.
Maybe when the NaOH under went a freezing episode something happened.
Will attempt to install Y strainer. Maybe mixer. Maybe circulation
pump. Maybe heater.
20Fe1 Added enough water to dilute to about 25% NaOH. Mixed for an hour by immersing a sump pump in the tank. Heater unnecessary because of the exothermic reaction. Removed gage. Started pump. Thick, viscous liquid for about 10 seconds. Pumping fine now.Hope this episode heads off your problems.
BIOFILTER (Air Quality Permit No. 2077-120-9884)
(no expiration date)
A biofilter is any filter in which the primary means of treatment is a result of bacteriological action by organisms growing on the filtration medium. This may take a variety of forms.
SPRAY TOWER FAN
PLANT AIR
SPRAY TIMER
Set for 1 hour per day maximum.
(Sprinkler system on top of Biofilter).
SCRUBBERS (Georgia Feed Products: Ceilcoat Scrubbers)
THEORY, DESIGN, AND OPERATION OF AIRBORNE ODOR CONTROL
SCRUBBERS.
The beneficial effect of bringing air into contact with water has been recognized since the days of the Roman aqueducts when the sides were intentionally left rough in order to increase the turbulence and increase the purifying effect of air.
Removing cooking odors from Plant air is accomplished by pulling the air through a 'shower'. A horizontal arrangement eases construction and maintenance requirements. The shower is a cascading waterfall of oxidant treated water. (One could make a fair comparison with the 'old' swamp cooler). We use tellerettes (Pall rings in scrubber #4) as packing material and dose the liquid with a surfactant to increase air to liquid contact area and time. The horizontal airflow enhances the gravity effect aiding reduction of unwanted particles. Much of the theory of cleaning the air is very similar to cleaning water ( just change the decimal point in a couple of variables).
In fact, several devices developed for water treatment have been adapted (easily) as air pollution control devices. The term "air stripping" (used in water treatment) could be read "water stripping". Dust sized particles transported by the air are trapped by contact in the liquid waterfall. The oxidant in the water (we use chlorine dioxide) works on breaking down the undesirable molecules. Mathematical expressions describing the stripping process are available to predict the removal that a scrubber will achieve. This requires the use of mass balance expressions across the scrubber and the kinetic equations. When the amounts of materials are known, it should be possible to establish a mass balance around each production process. From the materials balance, the extent of solids and liquids waste characteristics may be determined. A materials balance for the entire plant will also indicate the amounts of wastes generated and may be obtained by subtracting the amounts of materials shipped from the amounts purchased. Sherwood and Holloway attempted to correlate mass transfer coefficients showing that the vectors of the liquid and gas are dependent and independent. (Another way of saying that is this: They really don't know what is going on - there are too many chaotic things going on to figure out what is happening).
The degree to which the gas-water system deviates from equilibrium provides the driving force for diffusion. Consider a situation where a gas is diffusing from air into water. For this to occur, a concentration gradient in the direction of transfer in each phase must exist.
Air stripping and aeration are processes used in water treatment to remove dissolved gases such as carbon dioxide, hydrogen sulfide, other taste- and odor-causing compounds, and volatile organic compounds. The same process is applied when air is treated using water.
NORMAL OPERATION
(Supposed to be kept running continuously)
Turn on suction fan.
Get water level in sump up to a level for the recirculation pump to function.
Turn on recirculation pumps for spray over tellerettes.
Pressure gauge should read about 20 psig.
Check "CL310" metering pump operation for sufficient dosing. Foam should be contained in the applied stage.
Check CHLORINE DIOXIDE dosing system.
Chlorine dioxide is a powerful oxidant that is always prepared on site most economically by the reaction of chlorine and sodium chlorite. One mole of chlorine gas plus 2 moles of sodium chlorite (2NaClO2) produces 2 moles of chlorine dioxide and 2 moles of NaCl (salt). Our operation typically is: 40 pounds/day (rate) of chlorine gas in 6 gallons per minute of well water and sodium chlorite metering pump set for 70/80 (strokes/rate). The end result is sampled, observed for color and pH (around 3 plus or minus .3 SU ).
Oxidation processes involve the exchange of electrons between chemical species so as to change the oxidation state (valence) of the species involved. Strictly speaking, oxidation processes should be referred to as reduction - oxidation (redox) processes because one species loses electrons or is oxidized while another gains electrons or is reduced.
Chlorine dioxide was first produced from the reaction of potassium chlorate and hydrochloric acid by Davy in 1811. Not until the industrial-scale preparation of sodium chlorite, from which chlorine dioxide may more readily be generated however, did its widespread use occur.