JPS6246920A - Production of ammonium sulfate - Google Patents

Abstract

PURPOSE:To lower the tar base content in ammonium sulfate as a product and to make the ammonium sulfate odorless by sprinkling a satd. soln. of ammonia-rich ammonium sulfate on ammonium sulfate crystals produced as a by-product by the dry distillation of coal. CONSTITUTION:Ammonium sulfate crystals contg. mother liquor produced as a by-product by the dry-distillation of coal are fed from a tank 1 to a centrifu gal separator 3. The crystals are sent to a drier 8 and the filtrate is sent to a mother liquor neutralizing tower 7 through a tank 5. In the tower 7, the filtrate absorbs coke oven gas 13 contg. ammonia. The filtrate adjusted to 7-8pH is allowed to stand in a separation tank 6 to form an upper layer of a pyridine rich oily substance and a lower layer of base-free mother liquor. This mother liquor is sprinkled on ammonium sulfate crystals in the centrifugal separator 3 as a washing liq. through a washing tank 2. The tar base content in the crystals is lowered and ammonium sulfate 12 obtd. as a product does not emit an offensive odor due to tar base.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing ammonium sulfate, which is a by-product of coal carbonization.

<Prior art and its problems> Ammonium sulfate produced by coal carbonization contains sulfates of tar bases (pyridine, picoline, lutidine and their congeners) as impurities on the surface of ammonium sulfate crystals. Among them,
Pyridine has a strong unpleasant odor, which affects the commercial value of the product.

Conventionally, such impurities have been classified as
By adding aqueous ammonia to ammonium sulfate crystals, it is decomposed and liberated and removed.

That is, as shown in FIG. 3, aqueous ammonia is supplied as a cleaning liquid from the cleaning liquid tank 2 to the ammonium sulfate crystals supplied from the crystal supply M1, and the sulfate of the tar base is removed in the centrifuge 3. In this method, the crystals are transported by a belt conveyor 10 and dried.

However, in this method, aqueous ammonia is added as a cleaning liquid in the centrifuge, which not only decomposes the tar base sulfate adhering to the ammonium sulfate surface, but also dissolves the ammonium sulfate crystals themselves, resulting in a decrease in yield. Furthermore, since the tar base dissolves in the crystal-adhering water, it may volatilize on the belt conveyor and emit an odor. Furthermore, introducing ammonia water from outside is disadvantageous in terms of costs such as the cost of materials.

<Purpose of the Invention> Therefore, the object of the present invention is the power aspect of the by-produced by-product of coal carbonization.
We would like to provide a method for producing ammonium sulfate that decomposes the sulfate of ``pyridine'', reduces the tar base content in the ammonium sulfate product, makes it odorless, has a good yield, and is advantageous in terms of cost. There it is.

<Structure of the invention> The above objects are achieved by the following invention.

That is, the present invention provides a method for producing odorless crystals of ammonium sulfate produced as a by-product by carbonization of coal.
The present invention provides a method for producing ammonium sulfate, which is characterized by treating an ammonia-rich ammonium sulfate saturated solution. That is, when tar base is mixed into ammonium sulfate crystals, especially when pyridine is mixed in, it emits an unpleasant odor to the human body, so the problem is how to remove the tar base.

To that end, I will clarify the following two points.

■Tar base of ammonium sulfate (pyridine) odorless limit content t ■Pyridine concentration in crystals when spraying cleaning solution (ammonia-rich mother liquor) It is something to be measured.

Specifically, (1) tar salt in ammonium sulfate], (with respect to the odorless limit of 4F:Ii), a visual sensory test was conducted using samples of ammonium sulfate crystals adjusted with various salts and (concentrations). As described below, it was determined that the content of 60 ppI11 (containing pyridine: IY) or less was odorless.

(2) Also, spray the cleaning solution (ammonia rich I sl&): 1 (and for the concentration of pyridine in the crystals, the centrifuge of the actual device should be equipped with cleaning solution output piping, and the washing solution should be set in the sequence of the centrifuge's automatic timer. and incorporate the circuit,
The relationship was investigated through experiments.

The present invention will now be described in detail.

In preparing the free ammonia-rich solution A to be used as a washing solution in the ammonium sulfate manufacturing method of the present invention, the solution is prepared using a centrifugal separator 3 in the mother liquor neutralization tower 7 according to the steps shown in FIG.
The ammonia-containing coke oven gas 13 is absorbed into the filtrate. In this case, at the beginning of absorption, ammonia is consumed to neutralize the free acids in the solution, and after p115, tar salt J, (sulfate) is decomposed and liberated, and the basicity of pll7 and later In this region, decomposition and liberation become predominant, and when left to stand still in this state, it separates into two layers: a black oily substance rich in tar bases in the upper layer and an ammonium sulfate mother liquor containing detarred bases in the lower layer.

This lower layer of the detarred base ammonium sulfate solution is saturated with ammonium sulfate, and its basicity is due to ammonia.

In the present invention, this upper layer detarred base ammonium sulfate solution is used as a cleaning solution.

That is, as shown below, I: Ammonia-containing coke oven gas in the upper liquid neutralization tower 7! After absorbing 3 and adjusting the pH to 7 to 7, tar salts J and t are separated in a separate tank 6, and the removed product is used as a cleaning solution.

This cleaning solution can be applied to the 4 centrifugal machines 3 in the sequence of human → detachment → scraping, fX, and iiQ /++ as a purified culm↓
Sea urchins, charging → dehydration → washing - 1 - Remove the ridges and grate. In this case, sprinkle 4. i and i are 5 to 40%, preferably 20 to 30%, based on the ammonium sulfate mole charged into the centrifugal separator 3.

Next, the manufacturing process of ammonium sulfate in the present invention will be explained with reference to FIG.

Crystals containing LJ liquid are supplied to the centrifuge 3 from the crystal supply tank]. The crystals are transported to a dryer 8 via a belt conveyor 4. The filtrate passes through a filtrate tank 5 1; an upper liquid neutralization tower 7 absorbs ammonia-containing coke oven gas 13;

Then, as in the case of 1111 letters, the pll is controlled to 7 to 8, and the liquid is allowed to stand in a separate tank 6 to separate the pyridine-rich oily substance in the upper layer and the abasic CJ liquid in the upper layer.

This debasic L1 liquid is sprayed into the centrifuge 3 through the washing tank 2 as a washing liquid. In addition, the hot air used in the dryer 8 is transferred to a cyclone QJj and a Held Conhair 10.
It is dissipated through

In this way, the product obtained from ammonium sulfate 12 has no bad odor due to tar bases (especially pyridine), and the tar base content in the crystals is sufficiently low, that is, the pyridine content is 60 ppm or less. It is.

The limit concentration for insensitivity to odor is based on an odor sensory test regarding the concentration of pyridine in dry crystals. That is, when an odor sensory test was conducted on three panelists with odor present -1 and no odor +1, results as shown in FIG. 2 were obtained. That is, it was found that the critical concentration for insensitivity to odor was 60 ppm.

<Example> According to the process shown in FIG. 1, the addition conditions (amount of washing liquid and washing p11) were as shown in Table 1, and the relationship between the addition conditions and the lysine content of dry crystals of ammonium sulfate was investigated.

The results are shown in Table-1.

The amount of cleaning liquid is shown in the table as the amount of spraying, and is expressed as the ratio (%) of the amount of cleaning liquid to the amount of ammonium sulfate charged into the centrifuge.

Table 1 From Table 1, it can be seen that lysine is contained in the crystals by the method of the present invention!
It was found that only U was within the odorless limit white concentration. Also,
It has been found that ammonia in the cleaning solution is sufficiently effective for cleaning as long as the pH is controlled to 7 to 8.

<Effects of the Invention> In the present invention, since the ammonium sulfate crystal is sprayed with an ammonia-rich ammonium sulfate saturated solution with p117 to 8, tar bases (especially pyridine) attached to the surface of the ammonium sulfate by-produced by coal carbonization are removed. The sulfate can be decomposed and liberated, the tar base content in the ammonium sulfate product can be reduced, and the quality of the product can be stabilized. In this case, the content can be easily brought to 60 ppm or less, which is the limit concentration at which odor is insensible in the odor sensory test. In addition, the yield is good, and there is no need to newly introduce washing water from outside, which is advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the method for producing ammonium sulfate of the present invention. FIG. 2 is a graph showing the results of the odor sensory test. FIG. 3 is a process diagram showing a conventional method for producing ammonium sulfate. Explanation of symbols 1...Crystal supply tank, 2--Washing liquid tank, 3--Centrifugal separator, 4--Belt conhair, 5--Filtrate tank, 6-
- Separate tank, 7-fjJ liquid neutralization tower, 8... dryer, 9- cyclone, 10... belt conveyor,
11-・Sulfur wrapper, 12…Product ammonium sulfate, 13-・
Ammonia-containing coke oven gas, 14.-Hot stove, 15.
...Flash drying tube, 16-...Blower FIG, 1 FIG, 2 10

Claims (1)

[Claims] A method for producing odorless crystals of ammonium sulfate produced as a by-product by carbonization of coal, the method comprising spraying ammonium sulfate crystals with an ammonia-rich saturated ammonium sulfate solution having a pH of 7 to 8.