Methanol, production reactors

Figure 2.7 Two alternative reactor designs for methanol production give quite different thermal profiles.

After peroxide injection, conversion of methane increases fix)m -4% to -10%, methanol production increases 17 fold, and carbon dioxide increases 5 fold, along with modest increases in hydrogen and carbon monoxide. Introduction of hydroxyl radicals to the reactor leads to a greater fi action of product going to methanol as evidenced by methane conversion increasing 2.5 times, whereas methanol production increases 17 times. The increase in carbon dioxide is fiom "deep" oxidation of... 

Three-phase reactor systems are ideally suited for methanol production because of the ability to provide intimate contact between the gaseous phase reactants and the solid phase catalysts and to remove the large amounts of heat created by the high heats of reaction. In the three-phase system, an inert liquid phase circulates between the reactor and an external... 

A glass tube fixed-bed reactor was used as a closed static reactor. The cyclotron produced nC-radioisotope (Ti/2=20.4 min) was used for nC-labeled methanol production by radiochemical process. The nC-labeled methanol (shortly nC-methanol, - 3pmol, -600 MBq) was then introduced into 250 mg of zeolite at ambient temperature by He gas flow. Afterwards, equivalent volume of liquid methyl iodide was injected into nC-methanol to have mixture of methanol and methyl iodide and introduced into catalyst for investigation of methyl iodide influence. After adsorption (2 min), the catalyst was heated up to the required temperature. 

The above reaction can be carried out in the presence of a variety of catalysts including Ni, Cu/Zn, Cu/SiO, Pd/SiO, and Pd/ZnO. In the case of coal, it is first pulverized and cleaned, then fed to a gasifier bed where it is reacted with oxygen and steam to produce the syngas. A 2 1 mole ratio of hydrogen to carbon monoxide is fed to a fixed-catalyst bed reactor for methanol production. Also, the technology for making methanol from natural gas is already in place and in wide use. Ciurent natural gas feedstocks are so inexpensive that even with tax incentives renewable methanol has not been able to compete economically. 

It is of interest to assess the process potential of methanol production by a direct partial oxidation of methane. This way the steam reformer and the shift reactor can be saved, and the catalytic methanol reactor can be replaced by a noncatalytic partial oxidation reactor. It is estimated that direct partial oxidation is competitive if a conversion of methane of at least 5.5% can be obtained with a methanol selectivity of at least 80%. 

Schuth s group developed in the past a number of reactors similar to conventional testing methods with different degrees of sample integration. For multiphase reactions a 25-fold stirrer vessel reactor was developed [70] and for heterogeneous gas-phase reactions a 16-fold fixed-bed reactor was presented [71], which was later followed by a 49-fold parallel reactor [135], The reactor in Figure 3.42 was used for methanol production from Syngas at up to 50 bar and was essentially an improved version of the 49-fold reactor described in [135],... 

Methanol synthesis plants utilizing the low-pressure process currently operate at capacities of 2 x 105 to 2 x 106 metric tons per year [15]. Such installations are composed of a synthesis gas production unit, the actual methanol synthesis reactor, and a separation and purification section. The production and purification of synthesis gas accounts for 50%-80% of the total cost of methanol production, with the remaining cost associated with the actual synthesis and purification of methanol [2, 8], Although a variety of carbonaceous feedstocks can be transformed into synthesis gas, the steam reforming of natural gas (Equation [4]) is by far the most common option, especially for large plants [2, 15-16] ... 

With adjustment of the steam/methane ratio, the reactor can produce a synthesis gas with CO/H2 = 1/2, the stoichiometric proportions needed for methanol production. This mixture at approximately 200 atm pressure is fed to the methanol unit where the reaction then proceeds at 350°C. Per pass conversions range from 30 to 50 over the catalyst— typically a supported copper oxide with a zinc, chromium, or manganese oxide promoter 3... 

Application To produce methanol from natural or associated gas feedstocks using advanced tubular reforming followed by boiling water reactor synthesis. This technology is an option for capacities up to approximately 3,000 mtpd methanol for cases where carbon dioxide (C02) is available. Topsoe also offers technology for larger-scale methanol facilities up to 10,000 mtpd per production train and technology to modify ammonia capacity into methanol production. 

The feed to the reactor (not the fresh feed to the process) contains 28.0 mole% CO2, 70.0 mole% H2, and 2.00 moIe% inerts. The single-pass conversion of hydrogen is 60.0%. Calculate the molar flow rates and molar compositions of the fresh feed, the total feed to the reactor, the recycle stream, and the purge stream for a methanol production rate of 155 kmol CH OH/h. 

As a general rule, the combined feed to the reactor is a convenient stream to use as a basis of calculation for recycle problems when the stream composition is known. We will therefore temporarily ignore the specified methanol production rate, balance the flowchart for the assumed basis, and then scale the process to the required extent. In terms of the labeled variables, the problem statement will be solved by determining no, - oc, - sc, -Tsh. ip, and for the assumed basis, then scaling up no,... 

The solution procedure will therefore be to write balances on the reactor, then the condenser, then the fresh feed-recycle mixing point, and finally the purge-recycle splitting point. The flowchart may then be scaled up by the required amount to obtain a methanol production rate of 155 kmol/h. The calculations follow. 

For the assumed basis of 100 mol feed to the reactor, the production rate of methanol is n = 14.0 mol CH3OH. To scale the process to a methanol production rate of 155 kmol CH30H/h, we multiply each total and component molar flow rate by the factor... 

The fresh feed, which contains CO and H2 in stoichiometric proportion, enters the process at a rate of 2.2 m /s at 25°C and 6,0 MPa and combines adiabatically with a recycle stream. The combined stream is heated to 250°C and fed to the reactor. The reactor effluent emerges at the same temperature and is cooled to 0°C at P - 6.0 MPa, partially condensing the methanol product. The gas leaving the condenser is saturated with methanol 1% is taken off for process monitoring purposes and the remainder is recycled. An overall CO conversion of 98% is achieved. The ratio of H2 to CO is 2 mol H2/I mol CO everywhere in the process system. Ideal gas behavior may be assumed. 

After the condensed crude methanol is recovered in the high-pressure separator, it is sent to a methanol purification column. Typically, methanol purification requires two columns, one to remove the light ends (mainly by-products generated in the methanol synthesis reactor such as dimethyl ether and dissolved gases) and another to separate methanol and water and any other by-products with a lower volatility than methanol. Specification-grade methanol (greater than 99.85 wl% methanol) is recovered as the overhead product of the heavy ends column and sent to storage. 

In case methanol is used as an intermediate fuel (e.g. in mobile fuel cells), the cost of methanol production is of interest. Produced from fossil fuels, notably natural gas, at a price of 3 US GJ, reforming or series reactor schemes lead to a methanol production cost estimated around 5.5 US GJ (Lange, 1997). Advanced micro-structured string-reactors for this concept are under development (Homy et ah, 2004). 

We have made cost analysis for the solar methanol production for the system of Fig. 1. In this analysis, SCOT-solar farm (Solar Concentration Off-Tower central receiver beam-down configuration) is used for solar concentrating system(Fig.2). This solar concentrating system has an economical advantage, since the heavy chemical plant can be installed on the ground. Since the high temperature of 1000-1200°C is obtained by the SCOT-solar farm, chemical plant (or reactor) for solar-assisted coal gasification can be operated. Table 1 shows estimated investment cost... 

---