Detailed geologic and laboratory studies of 31 montmorillonite, bentonite, and fuller's earth deposits were included in a Nevada State publication.27 Each deposit was individually described and categorized as to end use. Data on selected fundamental aspects and industrial uses for the fuller's earth minerals, palygorskite, attapulgite, pilolite, and lassalite, were added to the technical literature. The work discussed the nomenclature, structure, chemical composition and analyses, X-ray analysis, differential thermal analysis and dehydration data, electron microscopy, occurrence, and origin and distribution.28

Union Carbide announced the development of a series of zeolite molecular adsorption sieves that reportedly can expectively control emissions of sulfur oxide and nitrogen oxide off-gases to below proposed Federal ceilings. Total operating costs for sieve units were reported to be around $1 per ton of acid produced.29

Papke, K. G. Montmorillonite, Bentonite, and Fuller's Earth Deposits in Nevada. Nevada Bureau of Mines Bull. 76, Reno, Nev., 1970, 47 pp.

28 Aneesuddin, M. The Clay Mineral Palygorskite. J. Mines, Metals and Fuels, v. 19, No. 6, June 1971, pp. 165-172.

25 Chemical Engineering. Chementator. V. 78, No. 27, Nov. 29, 1971, pp. 18-19.

Production of bituminous coal and lignite declined from 602.9 million tons in 1970 to 552.2 million tons in 1971. This was due principally to the work stoppage from October 1 to November 14 pending the negotiation of a new wage agreement in the industry. The strike was the longest industry interruption since 1950.

The strike had little impact on coal consumption at electric utility plants since most plants had stocked heavily in anticipation of the stoppage. Utility stockpiles reached the highest level in recent years, equaling 108 days supply by October 1, 1971. This compared very favorably with a 1970 high point of 81 days average inventory. By the time full production was resumed in mid-November, 60 of 350 power plant stockpiles had reached critically low levels. However, there was no significant shortage of electricity or fuel during the 44-day strike. On the other hand, exports declined from 70.9 million tons to 56.6 million tons. Consumption of coal at oven-coke plants declined from 94.6 million tons to 81.5 million tons, and all other manufacturing and industrial plants consumed only 68.7 million tons in 1971, compared with 82.9 million tons in 1970.

In all major coal producing States, underground production declined. The total output of 275.9 million tons was nearly 63 million tons lower than that of 1970. Strip mining production, although curtailed by the contract strike in October and November, was 15 million tons higher than that of 1970. Although production from auger mining declined nearly 3 million tons, strip and auger production combined accounted for one-half of total production in 1971.

Health and Safety Act of 1969. The total number of deep mines declined from 2,939 in 1970 to 2,268 in 1971, and the number of strip mines increased from 2,103 to 2,290.

In transportation, the rail cost of transporting coal increased substantially. The Interstate Commerce Commission imposed an 8-percent freight rate increase per ton in November 1970, and in March 1971 granted the railroads an additional 6-percent increase in the rate they could charge. As a result, the average rail freight rate per ton of coal increased 29 cents in 1971.

This chapter includes all bituminous coal and lignite produced in the United States except California and Texas lignite and bituminous coal and lignite from mines that produced less than 1,000 tons per year. Approximately 21⁄2 million tons of lignite were produced in Texas and about 25,000 tons in California. Details of the California and Texas mining operations are excluded from this survey in order that individual company operations are not revealed. All quantity figures represent net tons of marketable coal and exclude washery and other refuse. Statistics are final and are based upon detailed annual reports of production and mine operation furnished by producers. For production not directly reported (chiefly that of small mines), accurate data were obtained from the records of the various State mine departments, which have statutory authority to require such reports. Thus, complete coverage of all mines producing 1,000 tons per year or more is reported. Inclusion of many small mines that produce less than 1,000 tons per year was not attempted.

The monthly and weekly estimates of production, summarized in tables 4 and 9, are based upon railroad carloadings of coal reported daily and weekly by railroads, ship

1 Industry economist, Division of Fossil Fuels.

ments on the Allegheny and Monongahela Rivers reported by the U.S. Army Corps of Engineers, direct reports from mining com

panies, and monthly production statements compiled by certain local operators associations and State mine departments.

Shipments of bituminous coal and lignite, summarized by districts of origin, States of destination, type of consumer use, and by methods of transportation, show the participation of the bituminous coal and lignite industry in various local and national markets.

The distribution data by consumer use do not necessarily conform to the consumption data because the latter represent actual use at consumers' facilities, whereas the distribution data represent shipments from the mines, some of which were in transit or in consumers' storage.

Total shipments declined from 598.0 million tons in 1970 to 553.1 million tons in 1971. The largest decreases occurred in shipments overseas, to oven-coke plants, and to all other industrial markets. Receipts of coal by consumers in these categories were down 14.0, 15.8, and 13.5 million tons, respectively. Electric utilities, despite the 6-week work stoppage, increased their receipts by 2.3 million tons.

Shipments to retail dealers were down 3.6 million tons. Miscellaneous items such as railroad fuel, mine fuel, Canadian and United States Great Lakes dock storage accounts, and net changes in mine inventory decreased 0.3 million tons.

The distribution data in tables 36-39 are based on reports submitted quarterly to the Bureau of Mines voluntarily by producers, sales agents, distributors, and wholesalers, who normally produce or sell 100,000 tons or more annually; the unprecedented cooperation of these respondents resulted in their reporting about 94 percent of all coal produced or shipped. To account for total industry shipments, estimates for the remaining shipments are included, based on data from coal trade and other reliable coal statistical reporting agencies.

Additional details of bituminous coal and lignite distribution for 1970 are presented in a Bureau of Mines report.2

In 1971, the United States exported 56.6 million tons of coal, a decrease of 14.3 million tons from that of 1970. The drop in exports came as a result of lower demand abroad because of reduced requirements by the steel industry, rising coal prices, and an improvement in the world coking coal supply.

Japan maintained its position as the principal U.S. foreign market with a 34.8 percent share of total U.S. coal exports. Shipments of coal to Canada, Europe, and South America accounted for 31.5 percent, 28.9 percent, and 4.7 percent, respectively.

Although the United States was still the world's largest coal exporter in 1971 and exports are expected to grow, its share of the steadily expanding total international

trade in coal is expected to decline as consuming countries seek to diversify sources of supply and as additional competitive new coal mining capacity comes into production. The larger world market and the search for increasingly diversified supplies at the lowest cost has led to expansion of consumer large bulk carrier shipping units, which also points to a more stable international coal trade in the future. The larger fluctuations in demand and the buying of surplus coals for the immediate future are probably destined to account for a progressively smaller share of the market as more large-scale, long-term coal contracts from assured suppliers come on stream during the balance of the decade.

World production of bituminous coal and lignite in 1971 is estimated at 3,110 million tons, an increase of only four

2 Bureau of Mines. Bituminous Coal and Lignite Distribution, Calendar Year 1971. Mineral Industry Survey, Apr. 10, 1972, 39 pp.

tenths of one percent over the previous year. Except for the sharp decline in U.S. coal production, production in most major coal producing countries was higher in 1971 compared with 1970.

In Europe, production increased from 1,764 million tons to 1,803 million tons. Production of bituminous coal and lignite in the U.S.S.R., the largest coal producing

country in the world, was estimated at 615 million tons in 1971, an increase of 3.2 percent from the revised 1970 tonnage. Coal production in Asia increased 3.5 percent in 1971. Mainland China, the third largest coal producing country in the World, increased its production from 400 million tons in 1970 to 430 million tons in 1971.

Greater use was made of continuous miners in 1971. Nearly 56 percent of total underground production was achieved with these machines. A greater number of stationary rotary head units appeared in more powerful designs and contributed to new production records. Greater use was also made of battery-powered front-end loaders, which can load coal or haul men and supplies. In a new development, an ultrasmall front-end loader is being used in a clean-up and utility capacity. The unit is powered by a 15-horsepower electric motor, which receives power through a 500-foot trailing cable. The machine, because of its higher maneuverability, can get into corner and next to walls to pick up coal left by continuous miners.

During 1971, more mines were using bulk-handling techniques and pressurized systems for carrying and distributing rockdust. Most underground mining operations are finding that the use of trickle dusters is an effective means of insuring the incombustible content of return airways.

Continued efforts were expended in 1971 to improve methods of controlling dust and suppressing fires. A new foam generation method developed last year demonstrated its ability to suppress fires. The foam is thick and dry and its expansion reportedly lies between current low-and high-expansion types. A secondary use for this new foam is suppressing dust on beltlines and transfer points. Atomizing sprays (compressed air and water) have been tried and seem to offer promise for increased efficiency in dust suppression.

Emphasis in coal research by the Bureau of Mines in 1971 was placed on the production of clean-burning fuels from coal to help satisfy the rapidly expanding needs for energy while protecting the quality of the environment.

Design of a prototype plant to demonstrate the SYNTHANE coal gasification process was completed and plans were formulated for construction of the plant. The pilot plant will be capable of processing 70 tons of raw coal per day into pipelinequality gas. In another approach to produce a high-Btu gas from coal, the Hydrane Process was further developed. This process offers potential advantages over other advanced coal gasification schemes since no pretreatment of coal and less process hydrogen are required, and over 90 percent of the product methane results from the direct reaction of hydrogen with the coal. Construction of a 10 pound-per-hour reactor was completed and testing of the Hydrane process begun. In related work to produce a clean-burning low-Btu gas suitable for industrial fuel, run-of-mine bituminous coal was successfully processed for the first time in the fixed-bed gasifier. The Bureau's gasifier employs a stirrer to break up coke formations, which permits caking coals to be handled. Historically, the preferred feed for fixed-bed gasifiers has been coal particles no smaller than 3/4 inch and no larger than 2 inches. In the new tests, runof-mine coal containing up to 50 percent of particles smaller than 1/4 inch was successfully gasified. These findings are significant since the preparation costs involved in sizing the coal would be reduced substantially, as would the ultimate cost of the product fuel gas.

Two promising processes for producing low-ash, low-sulfur oil from coal were further developed. In the one process a mixture of 30 percent coal and 70 percent coal-derived oil, together with hydrogen, is passed through a fixed bed of pelleted catalyst at 450° C and 2000 to 4000 pounds