CN1195020A - Technique for producing city coal gas by using water gas - Google Patents

Abstract

A process for producing civil gas by methanating water gas includes such steps as desulfurizing water gas, boosting, moistening by increasing water vapour to the amount needed by methanation, changing the ratio of C : H : O, further desulfurizing and methanating, and features high output of methane, long service life of catalyst, low cost and easy control. Obtained civil gas has high thermal value up to 13.9 MJ/Ncu.m, low CO content less than 1% and low S content less than 1 ppm, and features high safety and no environmental pollution.

Description

The technology of water gas production town gas

The present invention relates to the production method of town gas, particularly utilize the method for water-gas through methanation production city coal gas.

A kind of sophisticated technology is that the employing coke-oven gas is a raw material production in the town gas production, but this technology need be built the coke-oven plant so that coke-oven gas to be provided, therefore exist one-time investment big, small-scale production deficiency in economic performance and required coking raw coal are difficult for problems such as solution, especially in numerous, samll cities and towns.Adopting the intermittent type fixed bed coal gas producer to produce water-gas then is technology very ripe and that generally adopt, but because methane content is low in this coal gas, the carbon monoxide content height, so service requirements that leading indicators such as its calorific value and security do not reach town gas, so, how people generally are devoted to improve methane content in the gas by the methanation reaction of carbon monoxide, reduce the research of carbon monoxide content simultaneously.As the atmospheric operation of Dalian Chemiclophysics Inst., Chinese Academy of Sciences exploitation, with difunctional M348 type catalyzer, adopt the external-cooling type fixed-bed reactor, with the method for water gas methanation production city coal gas (" fuel and chemical industry " the 20th rolled up, the 3rd phase, P.44,1989); The common exploitation of Germany Lurgi company and South Africa SASOL company, with special nickel catalyzator, adopt and generate the gas circulation, improve the method for water-gas ratio and insulation fix bed reactor, water gas methanation after conversion is generated synthetic town gas (" Hydrocabon Processing ", 1974 the 4th phases, P.69); And the application number that proposes to Patent Office of the People's Republic of China on September 26th, 1991 of the applicant is 91106812.0 application.In this application, the applicant has proposed a kind of utilization methanation nickel catalyzator commonly used, with water gas methanation production city coal gas craft.This technology comprises following flow process, i.e. first grade desulfurizing, supercharging, no-load voltage ratio, smart desulfurization and methanation.Though this technology can realize the methanation production of water-gas under the condition of using methanation nickel catalyzator commonly used, there is the shortcoming of three aspects in it, the one, and catalyst life is short, and this is because methanation catalyst commonly used is not suitable for operation under the high water to steam ratio; The 2nd, heat utilization efficiency is low, and methanation reaction generates the high enthalpy of gas, high vapour quantity does not utilize; The 3rd, the calorific value that generates gas is not high, is about 3000kcal/m ³

The purpose of this invention is to provide a kind of methane production rate height, catalyst performance is good, price is low, saves steam, reacting balance, the technology of the water gas production town gas that is easy to control.

The technology of water gas production town gas provided by the present invention, it is a kind of no-load voltage ratio methanation combined process flow, specifically be through first grade desulfurizing with unstripped gas, enter saturated section of conditioning tower after the pressurization, enter the no-load voltage ratio reactor through the main heat exchanger shell side, the gas after the no-load voltage ratio enters methanator through smart thionizer, generate gas through the main heat exchanger tube side, conditioning tower hot water section generates the gas cooling tower, enters gas holder and stores; Wherein:

(1) the methanation reaction condition is as follows:

Reaction pressure: absolute pressure 0.4-0.8MPa

Temperature of reaction: 230-430 ℃

Being reacted into implication forms: butt CO 2-4%

Water-gas ratio: H ₂O/ dry gas 0.3-0.5

(2) catalyzer is the methanation nickel catalyzator of Design Inst. of Chemical Industry, Hunan Prov. and the common Development and Production of Sichuan chemical industry group company's catalyst plant;

(3) after saturated section of conditioning tower, steam reaches more than 0.8 with the dry gas ratio in the unstripped gas.

Below with reference to accompanying drawing the invention main points in the technical solution of the present invention are described.

Fig. 1 is a process flow sheet provided by the invention.

In the methanation process provided by the invention, the effect that conditioning Tower is saturated section is to increase steam in unstripped gas, C in the feed change gas, H, the ratio that the O ternary forms, make the gas component after the no-load voltage ratio enter the non-arbon chromatography area of analysing charcoal molecular balance isothermal curve, can prevent the deposition of charcoal on catalyst from thermodynamics. After transformationreation, carbon monoxide content declines to a great extent in the gas, and gas ingredients becomes: CO is 2-4%, CO₂About 29%, H₂43%, steam 28.6%. And the generation of the required steam of no-load voltage ratio is to utilize the heat that methanation reaction produces to generate. To generate gas among the present invention and pass into successively main heat exchanger shell side and conditioning Tower hot water section, and not only reduce the temperature of generation gas but also utilized its high enthalpy to produce enough steams. Methanator adopts outer cold calandria type fixed bed reactor, conduction oil is by the guide pipe on shell of reactor bottom and top, and by the distribution hole on the shell wall, equably from each position radially, by each section deflection plate in the shell side, flow into and flow out shell side, reach conduction oil radially equally distributed purpose in shell side. Regulate the conduction oil temperature with pressure controller, stable reaction ground is carried out. The employed catalyst of methanation reaction is the Alumina-Supported Nickel Methanation Catalysts of chemical design institute, Hunan Province and Sichuan Chemical Group company catalyst plant joint development among the present invention. This catalyst is produced commodity by catalyst plant. This catalyst price is not high, under methanation reaction condition disclosed in this invention, and the excellent catalytic effect long service life. After first grade desulfurizing and the smart desulfurization, make the content of sulphur in the reaction gas to 1PPM, guaranteed the safety of catalyst.

Be in the purpose of desired ratio in order to reach in methanator porch control reaction gas CO and WGR, behind the conditioning Tower humidification, make that aqueous vapor reaches more than 0.8 with the dry gas ratio in the unstripped gas. In addition, generate thermoisopleth according to balance carbon, when carrying out methanation reaction, the non-carbon district scope of analysing of low reaction temperatures is greater than the non-carbon district of analysing under the high reaction temperature, although employed catalyst can work among the present invention, preferably control the methanation reaction temperature below 430 ℃ in higher temperature range.

During small-scale production, adopt this method to build a water gas methanation workshop, methanator diameter 1m processes water-gas 1800Nm³In/time, can produce calorific value 13.9MJ/Nm³Town gas 26000Nm³/ day, for 18000 families, supply approximately 60000 people and use. About 3,500,000 yuan of workshop construction investment, the about 0 .7 unit/Nm of town gas cost³(being pressed into 300 yuan/tons of calculating of stove coal price).

During large-scale production, adopt the workshop of amplifying the methanator diameter and increasing number of reactors, can supply the coal gas of 500,000 humans, about 2,000 ten thousand yuan of construction investment. Subregion is built, and can satisfy more metropolitan requirement.

Methanation process provided by the invention experimental results show that through technical grade: adopt humidification, and no-load voltage ratio and external-cooling type 2 in high-speed fixed bed methanator, bed temperature is evenly distributed, reacting balance, easy operating; Adopt by the Alumina-Supported Nickel Methanation Catalysts after the manufacturing condition improvement of this method, conversion ratio is high, and CO content is less than 1% in the generation gas, and sulfur content is used safety, environmentally safe less than 1ppm. The catalyst price is low; Heat utilization efficiency is high, does not consume steam, every generation 1000Nm³Town gas, 1 ton of byproduct steam; The calorific value that generates gas is higher, can reach 13.9MJ/Nm³ (3300kcal/m ³) more than, can replace liquefied petroleum gas and be used for industrial production as exotic fuels.

Embodiment

Methanator ingress unstripped gas is formed:

The composition butt is formed (%) wet basis and is formed (%)

H ₂????????60.6????????????43.3

CO?????????4.1?????????????2.9

CO ₂???????29.3????????????20.9

N ₂????????6.0?????????????4.3

H ₂O (steam) 28.6

Water/gas 0.4

Reaction pressure: 0.8MPa (absolute pressure) confluent: 0.67ml/min is in the catalyzer initial activity stage, and temperature of reactor distributes and works off one's feeling vent one's spleen to form and sees Table 1 and table 2.Methane content is 37.54% (butt) in working off one's feeling vent one's spleen, and calorific value reaches 14.54MJ/Nm ³In the catalyst activity steady stage, temperature of reactor distributes and works off one's feeling vent one's spleen to form and sees Table 3 and table 4.The methane content of working off one's feeling vent one's spleen is that calorific value reaches 13.9MJ/Nm about 34.81% (butt) ³

Table 1

Position mm (the full height of bed of %)	From bed 10	The bed inlet	Go into bed 14	Go into bed 28	Go into bed 42	Go into bed 56	Go into bed 70	Go into bed 84	Go into bed 98
										Temperature ℃	301	?336	387	432	432	407	377	432	316

Table 2

Table 3

Position mm (the full height of bed of %)	From bed 10	The bed inlet	Go into bed 14	Go into bed 28	Go into bed 42	Go into bed 56	Go into bed 70	Go into bed 84	Go into bed 98
										Temperature ℃	272	300	342	402	430	420	390	354	325

Table 4

Claims (1)

1. the technology of water gas production town gas, its flow process is a no-load voltage ratio methanation combined process flow, specifically be through first grade desulfurizing with unstripped gas, enter saturated section of conditioning tower after the pressurization, enter the no-load voltage ratio reactor through the main heat exchanger shell side, the gas after the no-load voltage ratio enters methanator through smart thionizer, generate gas through the main heat exchanger tube side, conditioning tower hot water section generates the gas cooling tower, enters gas holder and stores; Wherein:

(1) the methanation reaction condition is as follows:

Reaction pressure: absolute pressure 0.4-0.8MPa

Temperature of reaction: 230-430 ℃

Being reacted into implication forms: butt CO2-4%

Water-gas ratio: H ₂O/ dry gas 0.3-0.5

(2) catalyzer is the methanation nickel catalyzator of Design Inst. of Chemical Industry, Hunan Prov. and the common Development and Production of Sichuan chemical industry group company's catalyst plant;

(3) after saturated section of conditioning tower, steam reaches more than 0.8 with the dry gas ratio in the unstripped gas.