CN1292016C - Treatment method of organic silicon waste slurry - Google Patents

Abstract

A method for treating waste residue slurry in the synthetic process of an organic silicon monomer. Most of high-boiling-point substances (recovered) are separated by centrifugal gravity settling, and the hydrolysate obtained by hydrolyzing the residual slurry is easy to extract and free of reducing copper, so that potential safety hazards are eliminated; copper in the slurry is enriched in the hydrolysis solution in the form of copper sulfate and can be recovered by a reduction method, and the recovery rate of the copper reaches more than 95 percent; the solid hydrolysate meets the requirement of environmental protection and can be buried in a heap.

Description

Treatment method of organic silicon waste slurry

technical field

The invention relates to a treatment method for waste residue slurry formed in the synthesis process of organosilicon monomers.

Background technique

The waste slurry generated during the synthesis of organosilicon monomer accounts for about 3% of the monomer output. The device with an annual output of 50,000 tons will produce 1,500 tons of waste slurry, resulting in a large amount of chlorine loss. The liquid composition of organic silicon waste slurry has a boiling point greater than 75°C (mainly disilane, disiloxane, silylane, etc.), and there are suspended silicon powder, copper, tin and other metals, which are easy to burn and form when exposed to air. Acid mist. If the stacking method is used for processing, the pollution will be serious and there will be potential safety hazards. However, there is still a blank in domestic waste slurry treatment technology. At present, only the backlog is blocked or the copper is simply recovered, which does not fundamentally solve the environmental protection problem and causes waste of chlorine. Hydrolysis technology is mainly used abroad.

US Pat 4 221 691 provides a method for treating waste slurry: adding a small amount of mineral oil to the slurry to improve the treatment characteristics of the hydrolyzate. However, the disadvantages of this method are: the contact between the slurry and the hydrolysis medium is not sufficient, the hydrolysis rate is relatively slow, and the obtained hydrolyzate is in a viscous state, which is difficult to separate from the system; in addition, this method requires the organosilicon monomer in the slurry In the molecule, there are no less than 3 chlorine groups connected to each silicon atom, but most of the monomers in the slurry do not meet its requirements, so this method cannot be used to treat most of the slurry; and in the hydrolysis process Adding mineral oil will increase waste disposal costs and increase new sources of pollution, which does not meet environmental protection requirements.

US 4 408 030 provides a waste treatment process for multi-streams containing chlorosilanes, comprising the steps of: (A) determining the average SICL functionality of the streams; (B) mixing at least two streams so that the SICL functionality of the mixed streams greater than or equal to 2.8; (C) between 50°C and the boiling point of the hydrolysis medium, hydrolyze it with a mixture flow of the hydrolysis medium, and (D) separate the hydrolysis medium to obtain colloidal particles, which are easy to handle in the subsequent treatment process, Easy transport and further processing operations. Wherein the hydrolysis medium is selected from water, calcium chloride solution, and concentrated hydrochloric acid solution. The hydrolysis temperature is preferably 60-90°C. HCL produced during hydrolysis can be recovered. The colloidal particles in this method can be washed with water to further reduce the chlorine content in the colloidal particles. If the hydrolysis solution contains only water at first, hydrochloric acid will be formed as the hydrolysis progresses, and when the hydrochloric acid in the water is saturated, hydrogen chloride will be resolved. Hydrochloric acid and inorganic chloride can be added to the hydrolysis medium to make the hydrolysis solution saturated, so that hydrogen chloride can be resolved at the beginning of hydrolysis. The hydrolyzate is separated from the liquid by filtration or centrifugation, and the resulting solid hydrolyzate particles are non-adherent, easy to handle, convenient for transportation and further processing operations, and the hydrolyzate can also be washed with water one or more times to further reduce the chlorine content in the hydrolyzate. The disadvantages of this method are as follows: first, water, calcium chloride solution, or concentrated hydrochloric acid solution are used as the hydrolysis medium, and the hydrolyzed particles are small and difficult to extract from the reactor; second, the chlorine radicals adsorbed on the surface of the hydrolyzate The ion concentration reaches more than 10%. If you want to reduce it to a lower concentration, you need a lot of water to wash, and the discharge of waste acid is large.

EP 867442A2 introduces a hydrolysis process of methyl chlorosilane by-products, the process obtains at least two phases, including adding an aqueous medium to the by-products for hydrolysis, the aqueous medium may contain surfactants, the pH is at least about 7, and the temperature higher than 0°C. One of the phases is an inert solid, and the second phase is an aqueous solution, substantially free of metals, which can be discharged with or without treatment. Solids can be separated by filtration, sedimentation, flotation or centrifugation techniques, and aqueous media can be separated for recovery of salts, silicates or discharge to wastewater treatment plants. Surfactants are anionic or nonionic surfactants, preferably non-surfactants. The advantages of this process are: First, this method reduces the concentration of heavy metals in the hydrolyzate and solves the problem of waste treatment. The product obtained by the hydrolysis process is inert, has a high flash point, no gas precipitation, is not viscous, and is dust-free and easy to digest. Flowy, easy to handle and transport. Second, copper is enriched in the solid hydrolyzate and can be fully recovered. The disadvantage is that hydrogen chloride, one of the reaction products, is neutralized by the alkali in the hydrolysis medium to become a salt, which wastes a part of resources; in addition, the reduced copper contained in the solid hydrolyzate is heated, exposed to sunlight for a long time or piled up. It is prone to spontaneous combustion and is an important safety hazard.

DE4 116925 A1 describes a process for the hydrolysis of methylchlorosilane by-products by preparing a raffinate consisting of direct mixtures of chloro- and/or organochlorosilanes at a temperature from 20 to 100 °C (main between 35°C and 60°C), mixed with sulfuric acid with a concentration of 20% to 70% (mainly 40% to 60%), and with the separated hydrolyzate - calcium hydroxide, calcium oxide, calcium carbonate or a mixture thereof for neutralization until a floating solid mainly composed of polysiloxane or alginic acid is produced. By mixing with calcium hydroxide, calcium oxide, calcium carbonate or mixtures thereof, a dry suspended solid is produced from the original wet hydrolyzate. This solid includes up to 5%wt residual chloride and a small amount of 20%wt water for a total waste specific gravity of 0.5-1 g/ml. The separated liquid phase is hydrolyzed again or used to wash and dry those conversion reactants, gaseous hydrogen chloride. The main disadvantage of this process is that the liquid phase of the slurry is completely hydrolyzed, resulting in waste.

Contents of the invention

The invention overcomes the above-mentioned shortcomings of the prior art, and provides a method for hydrolyzing waste residue slurry formed during the synthesis of organic silicon monomers.

The processing method of the waste residue slurry in the synthetic process of organosilicon monomer provided by the invention comprises the following steps:

(A) The waste residue slurry in the synthesis of organosilicon monomer is separated by a gravity settling centrifuge to 90% (weight percent) high boilers for cracking and other purposes;

(B) The high-viscosity waste residue slurry after centrifugation is hydrolyzed in a hydrolysis kettle, and the hydrolysis medium is 68.6% sulfuric acid solution;

(C) a small amount of hydrogen chloride gas containing siloxane is separated out from the liquid phase;

(D) The hydrolyzate is subjected to liquid-solid separation, the solid hydrolyzate is discharged, and the liquid phase is subjected to subsequent treatment to recover copper.

The raw material slurry processed in the method of the present invention is the solid-liquid mixed waste produced in the process of direct method synthesis of organosilicon monomer, and its main components are solid particles such as high boiling matter and silicon powder, and the content of solid particles is 20%. After gravity sedimentation and separation, most of the high boilers have been separated, and the solid content of the slurry that is about to be hydrolyzed will reach 70%. Another inventive point of the present invention is that the present invention directly uses 68.6% high-concentration sulfuric acid in the processing of the next step, and this is because most of the high boiling substances in the raw material have been separated, so the required hydrolysis medium—the amount of sulfuric acid Another important reason is that the use of high-concentration sulfuric acid is also conducive to the recovery of copper.

The hydrolysis temperature in this method is 30-90°C, preferably 55-65°C. The concentration of the hydrolysis medium sulfuric acid solution is 68.6%.

In the industrialized device, because the processed slurry is viscous and difficult to flow, a gravity sedimentation centrifuge with a screw pusher device can also be used to make the feeding process go smoothly.

A small amount of hydrogen chloride gas containing siloxane produced in this method can enter the alkali absorption tower for neutralization.

The hydrolyzate can overflow from the side wall of the hydrolysis tank and pass through the liquid-solid separator for liquid-solid separation (solid separation by filtration, precipitation, flotation or centrifugal technology), and the solid hydrolyzate is buried; the liquid phase enters the acid water storage tank and undergoes reduction and other methods to recover copper.

The slurry raw material is fed from the bottom of the tank to increase its contact time with the hydrolysis medium. Sulfuric acid is a commercially available product.

Accompanying drawing 1 is process flow diagram of the present invention, wherein:

1. Water pipeline 2. Sulfuric acid pipeline

3. High viscosity slurry pipeline 4. Solid-liquid separator

5. Discharge of solid hydrolyzate after separation 6. Acid hydrolysis solution storage tank

7. Alkali absorption tank 8. Slurry raw material

9. Separated high boilers

Compared with the prior art, the present invention has the advantages that: first, the present invention separates most of the high boiling matter and 70% of the high-viscosity slurry from the slurry with a solid content of 20% through centrifugal gravity sedimentation, and the obtained high-boiling The product can be further cracked to recover dimethyl and other useful monomers. Then 70% of the high-viscosity slurry is hydrolyzed to enrich the copper in the slurry and be further recovered in the hydrolysis solution. The recovery rate of copper reaches more than 95%. The formed solid hydrolyzate can meet environmental protection requirements and can be landfilled. .

Detailed ways

Example 1

The raw material slurry is a liquid-solid mixture with a solid content of 20%, which can flow when stirred. The solid content of the high-viscosity slurry obtained after separation by gravity sedimentation is 66%, and its fluidity is very poor. It is used as the raw material for the following experiment. A gravity settling centrifuge with a screw pusher can be used.

Add 300g of water and 700g of 98% H ₂ SO ₄ to a three-necked flask with a stirring condenser and a thermometer, and add 210g of slurry to the reactor within 30 minutes at 60°C, and HCl gas is precipitated from the upper part of the reactor , a suspension of _H2SO4 containing HCl and solid hydrolyzate (mainly in _the form of silicic acid), overflows from the side wall into the filter, where the hydrolyzate is separated, and the wet weight of the hydrolyzate is 285g, and the filtrate is 925g , chlorine content 4.55%. The analyzed hydrogen chloride is absorbed by the lye, and the hydrolyzed solution recovers copper and recovers 96% of chlorine.

Example 2

Water 700g, 98% sulfuric acid 300g, other conditions are with example 1. The obtained hydrolyzate had a wet weight of 280 g, a filtrate of 930 g, and a chlorine content of 3.24%. The recovery rate of the solution copper after hydrolysis reaches 90%, which can meet the requirements.

Example 3

Water 400g, 98% sulfuric acid 600g, other conditions are with example 1. The obtained hydrolyzate had a wet weight of 295 g, a filtrate of 940 g, and a chlorine content of 4.65%. The recovery rate of the solution copper after hydrolysis reaches 93%, which can meet the requirement.

Comparative example 1

The obtained hydrolyzate has fine particles, and because the concentration of sulfuric acid becomes smaller, the liquid and solid are mixed together to form a turbid liquid, which is difficult to separate. The chlorine content of the obtained hydrolyzate was 5.24%.

Comparative example 2

The hydrolysis medium uses 1000 grams of water instead, and other conditions are with example 1. The resulting wet hydrolyzate was difficult to separate, had a chlorine content of 11.8%, the wet paste contained 50% water by weight, and had a residual chlorine content of 14.1%.

Comparative example 3

Reaction temperature is 20 ℃, and other conditions are with example 1. The obtained hydrolyzate particles are fine, viscous and not suitable for separation.

Comparative example 4

The hydrolysis medium is 27% hydrogen chloride solution, and the addition amount is 1000 g. Parameters such as reaction device, condition are with example 1. The resulting hydrolyzate is mixed with the solution and cannot be separated.

Comparative example 5

The raw material for hydrolysis is slag slurry with a solid content of 20%. The parameters such as the reaction device and conditions are the same as in Example 1. All high boiling substances contained in the slurry are hydrolyzed, which wastes a lot of resources. The main products obtained by hydrolysis are hydrogen chloride gas and recovered copper.

Claims (4)

1. the treatment process of the waste residue slurry in the organosilane monomer building-up process comprises the steps:

(A) to isolate weight percentage through the centrifugal gravity settling centrifuge be 90% high boiling material to the waste residue slurry of organosilane monomer in synthetic, is used for cracking and other purposes;

(B) the full-bodied waste residue slurry after centrifugal is hydrolyzed in hydrolysis kettle, and hydrolysis medium is 68.6% sulphuric acid soln, and hydrolysis temperature is 30-90 ℃

(C) hydrogen chloride gas that contains siloxanes is on a small quantity separated out from liquid phase;

(D) hydrolyzate is through liquid-solid separation, and the solid hydrolyzate discharges, and liquid phase reclaims copper through subsequent disposal.

2. method according to claim 1 is characterized in that hydrolysis temperature is 55-65 ℃.

3. method according to claim 1 is characterized in that gravity settling separating centrifuge wherein has the spiral pusher device.

4. method according to claim 1 is characterized in that wherein hydrolyzate from the overflow of hydrolysis kettle sidewall, obtains solid product by liquid-solid separation.