The table below compares
Hi-Chem Mag-50 with lime and soda ash.
Since lime is insoluble and does not slurry easily, handling
becomes quite difficult. Solids handling and slaking require
costly specialized equipment. And, because lime is highly abrasive,
this equipment requires constant maintenance and frequent replacement.
Hi-Chem Mag-50, by contrast, comes as a non abrasive slurry
which can be handled very inexpensively with little attention.
Consider also that any sulfuric acid or other sulfate present
in the waste effluent will react with lime to form insoluble
gypsum at the rate of 1.75 tons per each ton of sulfuric acid.
This unwanted precipitate further complicates the issue of solids
disposal.
Hi-Chem Mag-50 produces only harmless soluble salts which are
carried away in the effluent.
A 15% solution of soda ash crystallizes (freezes) at an unbelievable
80oF. This inescapable fact makes soda ash very expensive
to handle. When handled in solution, tanks, pipes and valves
must be heated. When handled as a solid, expensive solids handling
equipment is called for. In either case, regular and costly maintenance
is necessary, because soda ash is highly abrasive.
As mentioned, Hi-Chem Mag-50 is non-abrasive and will not freeze
above 32oF. It is truly an easy and inexpensive material
to handle.
If your effluent contains dissolved heavy metals, both soda
ash and Hi-Chem Mag-50 will form a precipitate sludge. However,
the sludge produced by soda ash is gelatinous, slow to settle,
and difficult to filter.
Sludge produced by Hi-Chem Mag-50, by contrast, is dense, fast
settling, and easy to dewater, thereby producing a smaller volume
and weight of sludge.
Neutralizers |
Lime |
Magnesium Hydroxide |
Soda Ash |
Equipment Costs |
Equipment costs higher than for magnesium hydroxide. Equipment
maintenace also higher because lime is abrasive. |
Less than for either lime or soda ash even with agitator
for storage tanks. |
Greater than for magnesium hydroxide because it requires
either expensive solids-handling equipment or heaters for
handling a solution that freezes at 800F. |
Residence Time (Reaction Speed) |
Fast acting to full neutralization. |
Moderately fast acting to 95% of neutral. Slower above
pH 6, resulting in more controllable process conditions and
enhancing flocculant performance in solids settling. |
Fast - acting to full neutralization with most acids. Difficult
process control conditions and inefficient solids removal
frequently occur when neutralization takes place very rapidly. |
Dissolved Solids Effluent* |
1.52 tons per ton HCl. 1.75 tons of insoluble salt per
ton of sulfuric acid. |
1.31 tons tons per ton of sulfuric acid. Generates only
soluble salts. |
1.61 tons per ton of HCl. 1.45 tons per ton of sulfuric
acid. |
Maximum pH if overtreated |
Can reach a pH of 12. |
Usually no higher than pH 9, the limit set by the Clean
Water Act. |
Can reach pH of 11. |
Sludge |
With heavy metals and sulfuric acid, lime creates large
quantities of calcium sulfate dihydrate, a sludge that settles
very slowly, and is difficult to filter and dewater. |
With a wide range of acids and metals, creates a sludge
that is very dense, fast-settling, and quite manageable. |
If effluent contains heavy metals, creates large quantities
of gel-like slow-settling sludge. |
Safety |
Hazardous to handle. Contact with eye can cause permanent
loss of vision. Repeated and prolonged contact with skin
may cause severe irritation, mild burns and - in extreme
cases - systemic injuries due to absorption. Breathing dust
or mist may cause intolerable discomfort to nose and throat. |
Comparatively safe to handle. Contact with eye may cause
temporary injury to cornea. Contact with skin rarely causes
irritation. |
Moderately hazardous to handle. Contact with eye may cause
temporary injury to the cornea. Contact with skin may cause
slight irritation. Breathing dust may cause painful irritation
to the nose and throat, and prolonged exposure may cause
systemic injury. |
Environmental Effects |
Limestone (CaCO3) is a naturally occuring mineral
that poses no threat to the environment. Lime (CaO) and hydrated
lime however are highly caustic and can cause immediate damage
to the environment. |
Relatively harmless. Magnesium Hydroxide is a natural mineral
that poses no unusual threat to the environment. |
A by-product of neutralization is a sodium salt which,
in high concentrations, may harm animals and vegetation. |
Ease of Handling |
Expensive solids - handling equipment is required. To maximise
effectiveness, lime is often slaked into a hydrated slurry.
A large storage hopper is needed. A slurry with the maximum
30% solids content will contain grit that causes rapid wear
to costly valves and pumps. |
Supplied as a ready-to-use slurry. Requires no special
equipment except an agitator in the slurry storage tank to
prevent setting. |
Very difficult to handle. Requires special solids - handling
equipment. If used in solution, usually required heated pipes
and valves, because it freezes at 800F. Generated
carbon dioxide, which may cause foaming and various process
problems. |
Availability |
Availability is no problem. |
Available in abundance from several locations in the U.S.A.
It's not produced as a by-product but by a "primary process." |
In the U.S.A. the raw material is mined almost exclusively
at one location, Green River, Wyoming. |
*Based upon Stoichiometric
ratios. Actual
usage may vary.
Hi-Chem Mag-50 Vs. Lime
| Neutralizing One Ton Of Sulfuric Acid |
|
|
| Pounds of Neutralizer Required |
Pounds of Dissolved Solids in Effluent |
|
| Neutralizing One Ton Of Hydrochloric
Acid |
|
|
| Pounds of Neutralizer Required |
Pounds of Dissolved Solids in Effluent |
|
Hi-Chem Mag-50 Vs. Soda Ash
| Neutralizing One Ton Of Hydrochloric
Acid |
|
|
| Pounds of Neutralizer Required |
Pounds of Dissolved Solids in Effluent |
|
| Neutralizing One Ton Of Sulfuric Acid |
|
|
| Pounds of Neutralizer Required |
Pounds of Dissolved Solids in Effluent |
|
|
