FR2460991A1 - Combustible gas prodn. from calcium carbonate - by decomposing calcium carbonate and reacting decomposition prods. with water and carbon - Google Patents

Abstract

Combustible gas, suitable for use as an energy source, is produced by heating CaCO3 (e.g. as limestone or marble) and reacting its decomposition prods. (CO2 and CaO) with carbon and water to produce a mixt. of CO, H2 and hydrocarbons. Gas has a calorific value of 11416 Kcal/mole (i.e. greater than that of water gas or bottled gas such as propane). Reaction used to produce the gas is highly exothermic. It is more economical than petroleum fuels.

Description

 The present invention relates to a combustible gas and a method for its production, and its main purpose is to provide a combustible gas which is useful as an energy source and which has never been disposed hitherto, and a method for producing it.

 According to the invention, a combustible gas is produced which can be used as an energy source, by heating with calcium carbonate, for example in the form of limestone or marble, and by reacting its decomposition products, namely carbon dioxide and calcium oxide, with carbon and water to produce a mixture consisting mainly of carbon monoxide, hydrogen, and hydrocarbons.

 The invention further claims, of course, the combustible gas produced by said process.

 By implementing the invention, according to a practical embodiment, marble or any other suitable form of limestone (CaC03) is heated in an oven at 8500, at which the decomposition of CaC03 into CaO occurs. and in G02. When this decomposition has occurred, appropriate amounts of carbon and water are added. When the mixture of CaO, C02, C and H2O is then heated to a higher temperature, a gaseous mixture composed of CO, H2, aliphatic hydrocarbons (mainly CH4) and CaC2 is produced. This product, which is a combustible gas mixture which can be considered as "lime gas" can serve as a new and unprecedented source of energy. This is particularly important when considering the current global shortage of other energy sources, such as petroleum.

In more detail, we place the marble or other form of limestone in an oven and heat it to 8500, temperature at which the body decomposes to produce carbon dioxide and calcium oxide, as shown l following equation:

 This equation describes a classic reaction.

The novelty in the process of the invention lies in the subsequent reaction of the decomposition products with controlled amounts of carbon and water at higher temperatures, for example up to about 1000 C. As the equations show below, the gaseous products of this subsequent reaction are carbon monoxide (CO), hydrogen (H2), aliphatic hydrocarbons (mainly methane (CH4)) and the by-product, calcium carbide (CaC2).

The decomposition and separate reactions of the decomposition products of limestone can be represented by the following equations:
at. CaCO3 C02 + CaO
b. C02 + 5C + 3H2O 5CO + H2 + CH4
vs. CaO + 7C + 3H2O 4CO + H2 + CH4 + CaC2
The overall reaction can therefore be presented as follows:
CaC03 + 12C + 6H2O 9CO + 2H2 + 2CH4 + CaC2
Thus, as this equation for the global reaction shows, the new and economical process of the invention produces a gaseous fuel, mainly consisting of carbon manoxide (CO), hydrogen (H2) and hydrocarbons, such as methane. (CH4).

A comparison of the gas of the invention with other synthetic gaseous fuels is given below:
1. "Lime gas is different from water gas.

Gas with water is a well known gaseous fuel which is produced by heating carbon and water to a relatively high temperature to obtain the reaction represented by the following conventional equation:

Water gas, which consists of almost equal amounts of carbon monoxide (CO) and hydrogen (H2), is produced by heating a mixture of equal parts of water (H2O) and carbon (C ). By contrast
2 te, the "lime gas which consists of a mixture of carbon monoxide (CO), hydrogen (H2) and methane (CH4) in a 9: 2: 2 ratio is produced by heating stone lime (CaGO3), carbon (C), and water (H20) in a 1: 12: 6 ratio. Calcium carbide (CaC2) is also obtained as a by-product.

 2. The process for producing "lime gas" differs from that used to produce acetylene. Acetylene (C2H2) is produced, in a conventional process, by adding water (H2O) to calcium carbide (CaC2) at ordinary temperatures. In contrast, "lime gas" does not contain acetylene, but consists of carbon monoxide (CO), hydrogen (H2) and methane (CH4) in a 9: 2: 2 ratio. The byproduct of the acetylene process is calcium hydroxide (Ca (OH2)) while that of the "lime gas" process is calcium carbide (CaC2) which is one of the reactants used for prepare acetylene.

3. As the following equation shows, the process for producing "lime gas" of the invention is completely different from that described in French Patent No. 694,459, that is to say:

While the classic French process shown in this equation produces carbon monoxide (CO) and calcium carbide (CaC2) by heating calcium carbonate or marble (CaC03) with carbon (C), this process is completely different of the "lime gas" process.

The latter also requires water which is not used in the French process and the products of the "lime gas" process comprising hydrogen (H2) and hydrocarbons, such as methane (CH4), as well as carbon monoxide (CO). The latter is the only gaseous product obtained in the French process.

The practical advantages of "lime gas" are:
a) It is an important source of energy:
The calorific value of "lime gas" is 11416 Kcal / mole or 488 190.8 Kcal / m3 higher than that of water gas. The calorific value of "lime gas" is also higher than that of bottled gas such as propane. The respective calorific values of "lime gas" and gas in water are 74,187.1 Kcal / mole or 3,028,068.1 Kcal / m3 and 62,771 Kcal / mole or 2,559,877.5
Kcal / m3
Thus, "lime gas" has a high energy value and will be a useful industrial fuel that can be used in place of the more expensive petroleum fuels.

b) Energy balance:
The exothermic reaction used to produce "lime gas" gives 1,028,046 Kcal / mole of calcium carbonate. The total energy production is 1,437,852 Kcal and the expenditure is 409,812 Kcal. "Lime gas" can therefore be used as a source of energy for economic growth and development.

c) Applications of the invention:
Since "lime gas" is a highly energy gaseous fuel, it can be used as an economical fuel in place of the more expensive petroleum fuels which are in short supply. Thus "lime gas" will be an important source of energy for all types of industry.

The steps leading to large-scale production of "lime gas" and its feasibility can be summarized as follows:
a) Creation of a pilot unit:
Lime gas has already been produced "without difficulty experimentally in moderate quantities in a pilot unit at Kuo-Fu Li, Hwa-Lian, Taiwan. This successful experimental production shows that the process can easily be extended to production large-scale industrial.

b) The production of "lime gas" is practical:
Experimental and confidential evaluation of the process by specialist engineers and technicians indicates that the process can be easily extended to large-scale commercial production.

c) Evaluation of the "lime gas" itself:
Many institutes, such as the National Taiwan University, the Chung Chong Institute of Technology and the Chung Shan Academy of Sciences have confidentially assessed samples of "lime gas" produced in our experimental pilot unit above. mentioned and stated that it is practical and new and has not been proposed as an energy source so far.

Claims (6)

 1. A method of producing a combustible gas which may be suitable for use as an energy source, characterized in that calcium carbonate is heated, for example in the form of limestone or marble, and one makes reacting its decomposition products, namely carbon dioxide and calcium oxide, with carbon and water to produce a mixture consisting mainly of carbon monoxide, hydrogen and hydrocarbons.  2. A method as claimed in claim 1, wherein the mixture comprises carbon monoxide, hydrogen, methane and calcium carbide.  3. Method as claimed in claim 2, in which the products of the decomposition of calcium carbonate are reacted according to the following equations:

 4. Method as claimed in one of claims 1, 2 and 3 wherein the limestone is made to decompose by indirect heating in an oven at a temperature equal to or greater than 8500 G.  5. Method as claimed in claim 4 wherein reacting the decomposition products of limestone in an oven at a temperature of 11000C.  6. Fuel gas obtained by a process according to one of the preceding claims.