Recovery from hydrates

The discussion in Section 7.6 is not intended to imply that the three methods of depressurization, thermal stimulation, and inhibitor injection are the only means of hydrate dissociation. Because the hydrate science is available as indicated in the earlier chapters of this book, the application of that science to recovery from hydrates is an exercise for the innovative engineer. Novel ideas such as fire flooding (Halleck et al., 1982), burial of nuclear wastes (Malone, 1985, p. 27), and the use of electromagnetic heating (Islam, 1994) are only three innovative ways of dissociating hydrates, but none have been tried. However, in this portion of the chapter, it is intended to describe trends for dissociating hydrates in several kinds of reservoirs, as an indication of the future. 

Titanium oxide (Ti02). This is produced from dmenite ore by mixing ore with carbon and heating in a rotary kiln. Also, the rotary lain is used in the process of recovery of titanium oxide from hydrated titanium precipitate at about 1250 K. 

Numerical assessment of CO2 enhanced CH4 recovery from the Mallik gas hydrate field, Beaufort-Mackenzie Basin, Canada... 

The combination of C02 injection and methane production over specific PT regimes allows the heat effects of C02 hydrate formation and methane hydrate decomposition to nullify each other resulting in a sustainable delivery process which both reduces C02 emissions to combat global warming and recovers methane to supplement the declining reserves of conventional natural gas (Fig. 4). This gas hydrate phase-behaviour in response to the dissociation and formation processes clearly demonstrates the potential of C02 enhanced CH4 recovery from the Mallik gas hydrate deposit. 

It is also of practical interests to control hydrate decomposition. The early studies were intended to understand the mechanism of hydrate decomposition when plugging in pipeline was encountered. The hydrate crystals generally decompose by de-pressurization (Kelkar et al., 1998, Peters et al., 2000 Hong et al., 2006). Thermal stimulation has also been considered in order to provide strategies for methane recovery from the natural hydrate by thermal stimulation (Selim and Sloan, 1989 Ji et al., 2001 Hong et al., 2003 Hong and Pooladi-Darvish, 2005). Hydrate decomposition studies may also be applicable to gas storage in hydrates. 

Figure 10. A hybrid hydrate-membrane process for C02 recovery from fuel gas.

In 1967, the Soviets discovered the first major hydrate deposit in the permafrost (Makogon, 1987). The hydrate deposit in the Messoyakha field has been estimated to involve at least one-third of the entire gas reservoir, with depths of hydrates as great as 900 m. During the decade beginning in 1969, more than 5 x 109 m3 of gas were produced from hydrates in the Messoyakha field. The information in the Soviet literature on the production of gas from the Messoyakha field is discussed in Chapter 7. Table 7.4 in Chapter 7 also lists other locations in Russia, including the Black Sea, Caspian Sea, and Lake Baikal, where evidence for hydrates has been provided from sample recovery or BSR (bottom simulating reflectors) data. 

Drilling results in the Blake Bahama Ridge have given promise for recovery of energy from hydrate reserves. Hydrate recovery results from ODP Leg 164 in the Blake Bahama Ridge seem to confirm the large resource estimation (Pauli et al., 1997, 2000 Lorenson and Collett, 2000). 

Along with the measurements of hydrate properties came several studies to determine the recoverability of gas from hydrates beneath the permafrost. Kamath and coworkers, in a research effort spanning over more than a decade, studied hydrate drilling and recovery in Alaska (Kamath, 1984 Kamath et al., 1984 Kamath and Godbole, 1987 Kamath and Holder, 1987 Roadifer et al., 1987a,b Godbole et al., 1988 Nadem et al., 1988 Sira et al., 1990 Kamath et al., 1991 Sharma et al., 1991, 1992). 

Due to this low pore filling and long formation times, hydrates should be considered a nonrenewable resource from which the recovery of gas is much more difficult than that from a normal gas reservoir. In addition, while an energy balance of the dissociation of pure hydrates is highly favorable, hydrates may be sparsely dispersed in sediment so economic recovery will be problematic. However, before turning to the production of gas from hydrates, consider first the locations of hydrate reserves, and requirements for formation. 

It can be argued that, if it is not possible to recover oceanic hydrates at high concentrations, it will be impossible to recover hydrates at lower concentrations in the ocean. Thus, success in the Gulf of Mexico, at Hydrate Ridge, or in a similar setting is vital to the energy recovery from more dispersed, deeper hydrates. 

An engineering breakthrough is required for the final step—recovery of hydrates in dispersed concentration (typically 3.5 vol% in 30% porosity) in the deep ocean (>500 m water depth) to use science and engineering, but most importantly previous experience, to produce hydrates efficiently from very dispersed resources in sediments. Probably not much new science will be needed for this step rather an engineering breakthrough will be necessary. 

Core temperatures upon recovery on the catwalk were variable. Small areas of low temperatures (6-8°C versus other parts of the core at 11-13°C) were interpreted as indicating areas where endothermic hydrate decomposition decreased the core temperature. Cores evolved large amounts of gas, which was considered responsible for low core recovery—from a norm of > 80% to 20-60% in the hydrate region. 

On June 6, this patient developed severe loin pain after he participated in two 150-m sprints at a town athletics meeting. After 5 days, he was referred to the outpatient clinic of our department. His serum creatinine and uric acid levels and FEUA, were 2.9mg/dl, 2.1 mg/dl, and 49.7%, respectively. His creatine phosphokinase (CPK) level was normal. When his serum creatinine level decreased to 1.58 mg/dl, a contrast medium was administered. A delayed computed tomography (CT) scan after 24 and 48 h confirmed patchy wedge-shaped contrast enhancement (Fig. 58). Under a diagnosis of ALPE, his body water balance (hydration) was controlled. In this patient, recovery was achieved 4 weeks after onset, and his serum creatinine and uric acid levels were then 1.0 mg/dl and 0.6 mg/dl, respectively. Furthermore, load tests with a uric acid reabsorption inhibitor (benzbromarone) and a uric acid excretion inhibitor (pyrazinamide) suggested presecretory reabsorption defect-related renal hypouricemia. A kidney biopsy 16 days after onset confirmed the recovery from acute tubular necrosis. 

A related procedure is used in the Westvaco process, except that sulfur dioxide is catalytically oxidized to sulfur trioxide using activated carbon at 75-150°C. The sulfur trioxide is then hydrated to sulfuric acid which is absorbed onto the active carbon [36]. Sulfur recovery from the sulfuric acid is as sulfur dioxide, which is formed in a regenerator by raising the temperature of the carbon and adding hydrogen sulfide. 

Ethjdene can be converted by simple hydration into alcohol. The process is catatytic and occurs by way of the intermediate ethyl sulphuric add, C2H6HSO4, and given a large supply of eth.3dene, the conversion into alcohol does not offer great difficulties. Its recovery from coal gas in this way is therefore theoretically possible, and Bury, at Skinningrove Coke Oven Works, has obtained i-6 gallons per ton of coal carbonized from rims of 5800 tons of coal carbonized per week Chemical Age, 1919, i, 714). 

T. Loerting, R.T. Kroemer and K.R. Liedl (2000) Chemical Communications, p. 999 - On the competing hydrations of sulfur dioxide and sulfur trioxide in our atmosphere . J.L. Stoddard et al. (1999) Nature, vol. 401, p. 575 - Regional trends in aquatic recovery from acidification in North America and Europe . 

In recent years, the gas industry has developed an increasing interest in nonconventional gas reserves, such as coalbed methane, tight-gas sands and methane hydrates. Tight-gas sands and coalbed methane are already economically produced at certain locations, while energy recovery from methane hydrate is stiU far from being a commercial application. Coalbed methane is formed during the process of coalification and stored in the micropores of solid coal. It can be desorbed from the coal by lowering the pressure. However, only a minority of coalfields are suitable for commercial coalbed methane recovery, because economic production is only possible from coal beds with exceptional permeability [14]. 

This indicates that some kind of structure will be present in liquid water surrounding CH4 or alkane molecule, which would be indicative of hydrate structure (Tanford, 1980). These data are of current interest in the future (from nonconventional reservoirs) gas recovery from methane hydrate reservoirs. 

Solvents are used in the production of fibers and in their modification and recovery from wastes. Production of fibers with optoelectronic properties for optoelectronic modulators requires several steps. In the first step, a metal hydrate or a hydrated metal compound (based on Pb, La, Zr, Ti) is dispersed in solvent (ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-methoxyethanol, or 2-ethoxyethanol), the resulting dispersion is then heated to polymerize the material and stretched to gel the fiber. The final fiber formation is achieved by heating the gelatinized fiber. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

The chlorides, bromides, nitrates, bromates, and perchlorate salts ate soluble in water and, when the aqueous solutions evaporate, precipitate as hydrated crystalline salts. The acetates, iodates, and iodides ate somewhat less soluble. The sulfates ate sparingly soluble and ate unique in that they have a negative solubitity trend with increasing temperature. The oxides, sulfides, fluorides, carbonates, oxalates, and phosphates ate insoluble in water. The oxalate, which is important in the recovery of lanthanides from solutions, can be calcined directly to the oxide. This procedure is used both in analytical and industrial apptications. 

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