JPS61151086A - Solidification prevention for substance for hygroscopic fertilizer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention 1 relates to prevention of caking of hygroscopic fertilizer substances used in bulk blends and the like.

Specifically, the present invention relates to a method for preventing caking of hygroscopic fertilizer substances, which comprises treating an aqueous solution of a specific condensation product of urea and formaldehyde with a hardening agent added thereto.

(Prior art) Hygroscopic fertilizer substances, such as large-grain urea with a particle size of 2 mm or more (usually 2 to 5 mm), are in demand due to customer demands such as high component ratio of bulk blend fertilizer and reduction in manufacturing cost. is increasing.

However, particulate urea has the problem of caking over time during storage, and many methods for preventing caking have been proposed for a long time.

Methods of changing the physical properties of caking substances, such as reducing moisture content, adjusting particle shape, and reducing crystal bridges on particle surfaces; diatomaceous earth, silica gel, talc, calcium sulfate,
There is a method using viscosity, etc.

These additives need to be added in large quantities, which increases hygroscopicity and also causes dust to form, which is undesirable in terms of the working environment as it causes significant dust to form and leak when discharging from sachets or flexible container banks. Otherwise, it can cause major problems such as clogging of the sieve and adhesion inside the equipment. Also, the anti-caking effect is insufficient.

Additionally, methods of treatment with surfactants (such as sulfonates or amines) have been proposed, but they are not at all (or insufficiently) effective.

On the other hand, a method of treating with formaldehyde or a urine-formaldehyde condensate is also known; for example, British Patent No. 875,730 describes a method of uniformly distributing an aqueous solution containing formaldehyde;
No. 0-34536 proposes a method of treatment with an aqueous solution of a urea-formaldehyde condensation product.

(Problems to be Solved by the Invention) The latter two methods are excellent methods that have a large caking prevention effect. However, in the method of British Patent W, 875,730, formaldehyde and urea are reacted for a certain period of time, or long processing times, drying steps, and exhaust gas cleaning equipment are required, requiring a large amount of equipment. There are costly problems. Also, special public service Sho 50-3453
Method No. 6 contains 2 to 5 moles of bound and free formaldehyde per mole of urea, and because the excess of formaldehyde is high, free formaldehyde or formaldehyde produced by hydrolysis of methylol groups is used as exhaust gas. Because the gas is generated and causes environmental pollution, exhaust gas treatment equipment is required, and the mixing process takes a long time.
For example, the rotating drum for mixing becomes larger. Furthermore, there are many industrial problems, such as the need for cooling to a temperature no higher than 35"C after treatment.

(Another Means to Solve the Problems) That is, the present invention provides a method for converting a hygroscopic fertilizer substance such as particulate urea into an aqueous solution of a condensation product of urea and formaldehyde containing 1.2 to 6 moles of formaldehyde per mole of urea. This is a method for preventing caking of hygroscopic fertilizer substances, which is characterized by treating with an aqueous solution containing a hardening agent.

In the present invention, there are no particular restrictions on the method for producing the absorbent fertilizer substance such as particulate urea, and for example, the method of granulating molten urea in a granulation tower (JP-A-50-N'
43so), or spray granulation of molten urea in a fluidized state using small urea lumps and grilled urea (Japanese Patent Laid-Open No. 56-7
6236) or particles having a particle diameter of 2 to 5 mm obtained by granulation with a dish-type granulator are preferably used.

In the method of the present invention, the temperature of particulate urea etc. is 40 to 80 °C,
Preferably, the treatment is performed at 60-70°C.

If the temperature of particles such as particulate urea is lower than a predetermined temperature, hot air may be fed into the coating device to heat the particles while processing.

Although the treatment time varies depending on the particle temperature, the reaction is completed in 3 to 11 minutes, preferably 5 to 8 minutes, with uniform coating.

The amount of the treatment liquid obtained by adding a curing agent to an aqueous solution of urea-formaldehyde condensation product to particulate urea, etc. varies depending on the hygroscopic fertilizer substance, but in the case of particulate urea, the amount of particulate urea to be treated is 005-0.4% by weight per urea,
Preferably about 0.1-0.2% by weight is sufficient.

Increasing the amount added is not a good idea unless there is something special about it; this is because moisture brought in from the processing solution remains in the urea particles (・, this may cause a decrease in the hardness of the particulate urea or a decrease in the hardness of the processed product). It also causes quality to change over time.

The aqueous solution of the urea-formaldehyde condensation product used in the method of the present invention is one containing 1.2 to 6 moles of formaldehyde per mole of urea, and is described, for example, in Plastic Materials Course 11 "Urea Melamine Resin" P-318. It can be easily produced by the following method.Additionally, a dilute aqueous alkali hydroxide solution is added to a formaldehyde aqueous solution to make it weakly alkaline, and then react by adding 1 part of urea. It may also be produced by reacting with an aqueous alkali hydroxide solution, adding the remaining urea and reacting, and finally adding a pH buffer.The reaction temperature is about 50 to 70°C. The amount of urea added is adjusted so that the molar ratio of total formaldehyde per mole of urea in the urea-formaldehyde condensation product produced in this manner is 1.2 to 6.

In the present invention, the number of moles of formaldehyde per mole of urea in the aqueous solution of the urea-formaldehyde condensation product can be 1°2 to 6, but as the number of moles of formaldehyde increases, the concentration of free formalin increases.
In addition, there are disadvantages such as faster curing speed, so 1, 2
Preference is given to using aqueous solutions of up to 5 to 2 molar ratios. or,
The solid content of this aqueous solution is generally 40 to 80% by weight.

As the curing agent added to the aqueous solution of the urea-formaldehyde condensation product in the present invention, silanic acid, formic acid, ammonium chloride, ammonium sulfate, ammonium phosphate, ammonium acetate, etc. can be used, but ammonium chloride is preferred. The appropriate amount to add is 1 to 2% by weight, and the method for adding it is to dissolve it in water in advance and use it as a 20% by weight aqueous solution. It is preferable to supply the components from separate storage tanks and mix them in a pipe.

As a device for coating particulate urea, it is sufficient as long as the particle surface can be coated uniformly, for example, a rotating drum type or a plate type rolling device is preferable, and the device can continuously coat particulate urea, etc. It is possible.

Preferably, good results can be obtained by blowing air into the coating processing apparatus so that the moisture brought in from the coating solution and evaporated can be quickly removed from the system.

In this case, the amount of airflow may be small and formaldehyde is substantially contained in the exhaust gas and can be discharged as is.

(Function) When the method of the present invention is applied to particulate urea, for example, by coating particulate urea with an aqueous solution of a condensation product of urea and formaldehyde, crystal bridges on the particle surface are reduced and smoothness is imparted. By reducing the surface area, the sensitivity of urea to moisture can be reduced and cake formation of particulate urea can be prevented, and the hardness of particulate urea can be increased to prevent caking of particulate urea. It is estimated to be.

(Example) ' Hereinafter, the present invention will be specifically explained with reference to Examples.

Examples 1 to 11 Using a rotating mixing drum with a capacity of 51 °C, the temperature was 40 °C in batch mode.
Three types of treatment liquids were used to spray large particles of urea at ~80°C, each in a predetermined amount, and the treatment time in the drum was approximately 3 minutes to 11 minutes.
Processed within minutes.

At this time, the drum was sealed while mixing in the drum, and the formaldehyde concentration in the gas phase was measured immediately after the treatment.

The caking properties of the large urea particles treated in this manner were tested.

In addition, formaldehyde was measured using the north type detection tube.

On the other hand, the consolidation test was conducted using a cylinder type 10CrrLφ SU.
Sample 3509- was charged into a container made of S, and the load was 0.55 kg/, ffl under the conditions of room temperature 40°C and humidity 40%.
Stored for days.

The load was removed and the consolidation hardness was measured using a Yamanaka soil hardness meter. For comparison, examples 1 to 1 are shown in which no aqueous condensation product solution is added.
Shown in 1. The results are shown in Table-1.

Comparative Examples 1 to 4 In order to examine the effect of adding the curing agent of the present invention, tests similar to those in Example 1 were conducted except that no curing agent was used. The results are shown in Table-1.

As is clear from the above results, Comparative Example 2
The concentration of formaldehyde in the gas phase inside the rotating mixing drum is extremely high, and the particle surface of the treated product is sticky, and in the consolidation test, it was observed that there was some adhesion to the inner wall of the cylinder, and the consolidation strength was low. It is also high and inferior.

Examples 12 to 18 Large urea particles granulated using a fluidized bed method were sized to the product size using a sieve machine. This material had a particle temperature of 70°C and was continuously fed to a rotating mixing drum. An aqueous solution II CI+ of the urea-formaldehyde condensation product mixed with 1% by weight of NH4Cl as a curing agent was sprayed and treated for about 5 minutes while rolling.

At this time, a small amount of air was pumped into the drum to remove evaporated moisture from the system. At this time, formaldehyde in the gas phase was not detected (2 ppm or less).

Consolidation tests were conducted on the products treated in this way. The results are shown in Table 2.

Comparative Examples 5-8 The procedure was the same as in Examples 13-18, except that the aqueous solution of the urea-formaldehyde condensation product was sprayed without adding a curing agent.

As a result, the formaldehyde concentration in the drum exhaust was 6.
ppm and high (loss is greater than in the example).

The results are shown in Table-2.

The above results show that the method of the present invention has a low formaldehyde concentration in the exhaust gas from the mixing drum, and is an excellent method. Especially with regard to caking properties, IT
In the F/132 stack, there is a large change over time, and some sort of handling is required for ejection.

Table 2) FL120kg polyethylene bag deposition test method Note: No-bin polyethylene bag, load 4T/m' after 1m deposition test
After opening the bag, it was sieved for 10 minutes.
The weight of the lumps of m/'m or more is weighed and this is taken as the solid lump ratio.

Consolidation strength was determined by measuring the strength of the lumps using a Yamanaka soil hardness meter.

(2) In the I T Fl two-tier stacking test (two tiers of 1-ton flexible container bags were stacked), the discharge status of the lower tier was checked, and the consolidation strength of the discharged solids was measured in the same manner as above.

(Effects of the Invention) According to the present invention, by coating a hygroscopic fertilizer substance such as particulate urea with a hardening agent added to an aqueous solution of a urea-formaldehyde condensation product, the particulate urea and the processing agent are combined. The processing time is short, in particular, no heating drying equipment is required, and the concentration of formaldehyde in the exhaust gas is significantly lower than that of conventionally known methods. becomes possible.

Particulate urea, etc. treated by the method of the present invention has many features such as improved caking property and improved mechanical strength, and the product remains free for a long time. It exhibits fluidity, has the ability to be stored in warehouses, moved, transported in flexible container bags and plastic bags, and can be transported and stored without any difficulty even in areas with highly variable climatic conditions. becomes.

Claims (1)

[Claims] 1) A hygroscopic fertilizer product characterized in that a hygroscopic fertilizer material is treated with an aqueous solution of a condensation product of urea and formaldehyde containing 1.2 to 6 moles of formaldehyde per 1 mole of urea and a hardening agent added thereto. Method of preventing caking of substances.