CN102757324B

CN102757324B - Method for producing formaldehyde from methanol under oxygen-rich condition and utilizing formaldehyde exhaust gas

Info

Publication number: CN102757324B
Application number: CN201210159750.4A
Authority: CN
Inventors: 王琳
Original assignee: Shanxi Yangmei Fengxi Fertilizer Industry (Group) Co Ltd
Current assignee: Shanxi Yangmei Fengxi Fertilizer Industry (Group) Co Ltd
Priority date: 2012-05-22
Filing date: 2012-05-22
Publication date: 2014-07-16
Anticipated expiration: 2032-05-22
Also published as: CN102757324A

Abstract

The invention discloses a method for producing formaldehyde from methanol under oxygen-rich conditions and utilizing a formaldehyde exhaust gas, belongs to the technical field of chemical production and relates to a formaldehyde production method. The method comprises the following steps: feeding gasified methanol into a mixer; mixing air and oxygen (volume concentration of 35%) and then preheating to obtain oxygen-rich air which is fed into the mixer, wherein the oxygen (volume concentration of 35%) is obtained by producing oxygen through air separation and mixing with the air or obtained by mixing the air with the gas resulting from nitrogen removal through pressure-variable adsorption; feeding steam into the mixer, wherein the volume ratio of methanol gas to oxygen-rich air to steam is 3:4.4:1; and allowing the reaction to take place among the gases, cooling the gases and feeding into an absorption tower where a formaldehyde finished product and a formaldehyde exhaust gas are produced, feeding a part of the formaldehyde exhaust gas into the mixer for recycling use, feeding another part of the formaldehyde exhaust gas into a synthetic ammonia gas making furnace where the formaldehyde exhaust gas is mixed with water gas and the mixture serves as a raw gas of synthetic ammonia. The method is simple, reduces the quantity of the produced exhaust gases, reduces the energy consumption of the whole process, and has significant economic benefits.

Description

A kind of methyl alcohol oxygen enrichment is produced formaldehyde and formaldehyde waste gas utilization method

Technical field

The invention belongs to chemical production technical field, relate to prepn. of formaldehyde, be specifically related to a kind of methyl alcohol oxygen enrichment and produce formaldehyde and formaldehyde waste gas utilization method.

Background technology

Industrial production formaldehyde mainly adopts methyl alcohol air oxidation process, is divided into silver-colored Catalytic processes and iron-molybdenum oxide Catalytic processes, referred to as Yin Fa and iron molybdenum method by its catalyzer used difference.

1, silver catalyst method

Silver method is the main method of producing in early days formaldehyde, the method is to make catalyzer with silver, the mixture of methyl alcohol and air is raw material, under the situation higher than the limits of explosion upper limit (>37%), in fixed-bed reactor, carry out catalytic oxidation and generate formaldehyde, temperature of reaction is between 550～650 ℃, and reaction gas makes 37% formaldehyde solution after absorbing processing.

Its main chemical reactions has:

Oxidizing reaction:

CH ₃OH + 0.5 O ₂ → CH ₂O + H2O △H=-157.2kJ/mol

Dehydrogenation reaction:

CH ₃OH → CH ₂O + H ₂ △H=85kJ/mol

Except occurring above-mentioned methanol oxidation and dehydrogenation reaction, also have a small amount of side reaction generations such as methane, carbon monoxide, carbonic acid gas, formic acid that generate.

Because the catalyzer manufacture method adopting is different with form, can be divided into again silver gauze, float stone is silver-colored, crystallization is silver-colored and the method such as electrolytic silver, wherein, best with the performance of catalyst for electrolytic silver, the yield of formaldehyde can reach 87%.

2, iron-molybdic catalyst method

Iron molybdenum method is a kind of novel method of producing formaldehyde growing up nearly decades, the method is to make catalyzer with metal oxides such as molybdenum-irons, under the condition of methanol concentration lower than lower explosive limit, methyl alcohol and excess air are at 280～340 ℃, by calandria type fixed bed oxidation of catalyzer is housed, generate formaldehyde, reaction mixture gas can make more than 50% concentrated formaldehyde solution after absorbing.

Its main chemical reactions formula is as follows:

CH3OH + 0.5 O ₂ → CH ₂O + H2O △H=-157.2KJ/mol

CH ₃OH + O ₂ → CO + 2 H ₂O △H=-383.8KJ/mol

Adopt iron molybdenum method can obtain 97% transformation efficiency and higher selectivity, produce the high-concentration formaldehyde containing low alcohol.

For method 1, adopt circulation of tail gas can produce high-concentration formaldehyde, by methanol loop method, can produce the formaldehyde of low alcohol content, owing to adopting air to originate as oxygen, cause in the large and tail gas of circulation of tail gas amount nitrogen content too high and cannot effectively utilize.For method 2, compare the investment of silver-colored method be twice above, long flow path, power consumption is high, hydrogen not in tail gas, cannot fully utilize.

Summary of the invention

The present invention is the problem existing in order to solve above-mentioned prior art, and provides a kind of methyl alcohol oxygen enrichment to produce formaldehyde and formaldehyde waste gas utilization method.

The present invention is achieved by the following technical solutions:

Methyl alcohol oxygen enrichment is produced formaldehyde and a formaldehyde waste gas utilization method, comprises the following steps:

(1) methanol gasifying: methyl alcohol is sent into mixing tank after reboiler gasification, and the methanol solution pump around circuit of reboiler bottom is to reboiler bottom;

(2) preheating oxygen-rich air: be preheating to 110 ℃ of temperature after the oxygen mix that the air after filtering and volumetric concentration are 35% concentration, obtain oxygen-rich air, then send into mixing tank, wherein the volume ratio of the oxygen of air and 35% concentration is 3:1, wherein 35% concentration oxygen is joined air by making oxygen by air separation and is produced, or is allocated in air and produced by the gas after pressure-variable adsorption is carried nitrogen;

(3) gas mixes: steam after filtering, vapour distributor is entered to mixing tank by variable valve adjust flux, and the gas that obtains mixing, wherein in mixing tank, the volume ratio of methanol gas, oxygen-rich air, steam is 3:4.4:1;

(4) filter oxidation: the gas mixing is sent in the oxidizer that catalyzer is housed by spark arrester after filter elimination impurity again, gas is from top to bottom by the catalyst layer in oxidizer, under the effect of high temperature and catalyzer, there is oxidation and the dehydrogenation reaction of methyl alcohol, generate formaldehyde gas and other hot gass, wherein temperature is 580 ~ 650 ℃, and catalyzer is silver catalyst;

(5) absorb: the gas generating in oxidizer is carried out to quenching by the quench zone being close to oxidizer rapidly, be cooled to below 90 ℃, then send in absorption tower and absorb, generate formaldehyde finished product and formaldehyde tail gas, a formaldehyde tail gas part is sent into mixing tank and is recycled, and a part is sent into ammonia stove and mixed as syngas for synthetic ammonia with water-gas.

The 60000 tons/year of formaldehyde plants of take adopt pressure-variable adsorptions to carry gas after nitrogen and allocate air into and do raw material as example, implement this inventive method, wherein:

1, by improving into the concentration of oxygen, reduce air flow quantity, it is 5000 Nm that traditional technology needs air flow quantity ³/ h, the present invention is owing to having adopted oxygen-rich air to do raw material, and total gas flow is 4000 Nm ³/ h, compares traditional technology and has reduced by 1000 Nm ³/ h, through measuring and calculating, reduces blower fan power consumption more than 10%;

2, air flow quantity minimizing causes producing the minimizing of tail gas amount, and loop tail tolerance also reduces, and reduces the energy consumption of whole technique; Adopt tail gas amount and composition and conventional silver method after this method to produce formaldehyde contrast, in Table 1;

The traditional prepn. of formaldehyde of table 1 and this technique prepn. of formaldehyde tail gas synopsis

3, in formaldehyde tail gas, the content of nitrogen reduces, total available gas CO+H ₂content increases to 19.95%, than the CO+H of traditional technology ₂content is high by 3.75%, and the combustion heat value of unit volume increases;

4, adopt fixed-bed intermittent gasifying process to produce syngas for synthetic ammonia, the unstripped gas of this technique is called again semi-water gas, and the mixing of water-gas and air gas (recovery gas during blowing) is semi-water gas, and the composition of water-gas is in Table 2,

The composition of table 2 water-gas

Title	CO ₂	CO	H ₂	N ₂	O ₂, CH4 etc.
						Content %	6	36	52	6	On a small quantity

Air gas composition, in Table 3,

The composition of table 3 air gas

Title	CO ₂	CO	H ₂	N ₂	O ₂, CH4 etc.
						Content %	15	7	4	74	On a small quantity

According to table 3 data, reclaim the total effective constituent CO+H of gas in gas ₂be 11%, total available gas CO+H in formaldehyde tail gas ₂content 19.95%, the super available gas content 8.95% reclaiming in gas of this content, the calorific value of formaldehyde tail gas reclaims the calorific value of gas, CO higher than blowing ₂the invalid gas of synthetic ammonia, CO in formaldehyde tail gas ₂content only has 30% of recovery gas, therefore, replaces air gas (recovery gas) to mix with water-gas produce syngas for synthetic ammonia, will obviously improve the quality of unstripped gas with formaldehyde tail gas.

Compared with prior art, technique of the present invention is simple, by improving into the concentration of oxygen, reduces air flow quantity, air flow quantity minimizing causes producing tail gas amount and reduces, and loop tail tolerance also reduces, and reduces the energy consumption of whole technique, there is significant economic benefit, be applicable to promoting the use of.

Accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention.

Embodiment

Embodiment 1

(4) filter oxidation: the gas mixing is sent in the oxidizer that catalyzer is housed by spark arrester after filter elimination impurity again, gas is from top to bottom by the catalyst layer in oxidizer, under the effect of high temperature and catalyzer, there is oxidation and the dehydrogenation reaction of methyl alcohol, generate formaldehyde gas and other hot gass, wherein temperature is 580 ~ 600 ℃, and catalyzer is silver catalyst;

(5) absorb: the gas generating in oxidizer is carried out to quenching by the quench zone being close to oxidizer rapidly, be cooled to 90 ℃, then send in absorption tower and absorb, generate formaldehyde finished product and formaldehyde tail gas, a formaldehyde tail gas part is sent into mixing tank and is recycled, and a part is sent into ammonia stove and mixed as syngas for synthetic ammonia with water-gas.

Process flow sheet as shown in Figure 1.

Embodiment 2

(4) filter oxidation: the gas mixing is sent in the oxidizer that catalyzer is housed by spark arrester after filter elimination impurity again, gas is from top to bottom by the catalyst layer in oxidizer, under the effect of high temperature and catalyzer, there is oxidation and the dehydrogenation reaction of methyl alcohol, generate formaldehyde gas and other hot gass, wherein temperature is 600 ~ 630 ℃, and catalyzer is silver catalyst;

(5) absorb: the gas generating in oxidizer is carried out to quenching by the quench zone being close to oxidizer rapidly, be cooled to 85 ℃, then send in absorption tower and absorb, generate formaldehyde finished product and formaldehyde tail gas, a formaldehyde tail gas part is sent into mixing tank and is recycled, and a part is sent into ammonia stove and mixed as syngas for synthetic ammonia with water-gas.

Embodiment 3

(4) filter oxidation: the gas mixing is sent in the oxidizer that catalyzer is housed by spark arrester after filter elimination impurity again, gas is from top to bottom by the catalyst layer in oxidizer, under the effect of high temperature and catalyzer, there is oxidation and the dehydrogenation reaction of methyl alcohol, generate formaldehyde gas and other hot gass, wherein temperature is 590 ~ 610 ℃, and catalyzer is silver catalyst;

(5) absorb: the gas generating in oxidizer is carried out to quenching by the quench zone being close to oxidizer rapidly, be cooled to 70 ℃, then send in absorption tower and absorb, generate formaldehyde finished product and formaldehyde tail gas, a formaldehyde tail gas part is sent into mixing tank and is recycled, and a part is sent into ammonia stove and mixed as syngas for synthetic ammonia with water-gas.

Claims

1. methyl alcohol oxygen enrichment is produced formaldehyde and a formaldehyde waste gas utilization method, it is characterized in that comprising the following steps: