Two local firms say they expect major sales to result from their participation in a U.S. trade and investment mission to Africa in January.

Representatives of T-CAS America, an engineering and construction firm located in Falls Church, and Gateway International Holdings Inc. were among 70 American businessmen and government officials who visited the Ivory Coast, Nigeria, Cameroon and Morocco on a trip headed by Secretary of Commerce Malcolm Baldrige and Secretary of Agriculture John R. Block.

James S. Stotsky, chief executive officer of T-CAS America, has reported consulting with Nigerian officials on several projects, including a weather radar system. He said the firm expects over the next few years to conclude contracts with Nigeria worth several million dollars.

Gateway International says its representatives began consultations with Ivory Coast government officials about providing oil pollution equipment to the west African country. Gateway officials have returned to the Ivory Coast to continue the discussions.

The executives who took part in the mission represented the agribusiness, agricultural commodities, construction engineering, telecommunications and mining industries.

Recent agreements by international lending and financial institutions:

Inter-American Development Bank

* A $500,000 financing to help Haiti establish a food processing plant designed to help raise the nutritional level of an estimated 15,000 low-income families in the Les Cayes region. The financing will be used by La Minoterie d'Haiti, a government agency established in 1969 to produce and market wheat flour. The proposed plant will produce a high-protein food called AK1000, or Acamil, which is composed of a combination of corn and beans. Acamil has been produced commercially in small quantities in Haiti for several years. The plant will provide jobs for 34 people and will purchase its supply of corn and beans from about 7,000 farm families in the area. The bank also approved a $153,000 technical cooperation grant to support organization of the plant, agricultural assistance for small farmers and to control contamination in the Acamil food processing. La Minoterie d'Haiti will provide 58 percent of the financing for the project.

World Bank

* A $5.8 million loan to the Bahamas to improve living conditions in Nassau city's Grants Town area, the poorest neighborhood in the country. Despite its success as a tourism center, the Bahamas suffers from high unemployment in its cities. The bank-assisted project will attempt to provide better housing and employment through slum improvement and industrial promotion. In addition to urban amenities and housing assistance, the project will provide expertise to the Bahamas Agricultural and Industrial Corp., a public agency, to help it promote the country as an attractive site for industrial investment.

* An International Development Association credit of $8 million to Benin to hire technical experts to strengthen the government agency responsible for petroleum exploration. Development of Benin's Seme field, located about 15 kilometers offshore, is already underway. The government decided to develop the field on its own in 1979, mostly with funds from abroad, because oil prices did not provide sufficient incentive to private oil companies. Beninese technicians will be trained to take over operation of the Seme field, and consultants will assist the government with a petroleum exploration program to attract private companies. In addition, the European Investment Bank will provide up to $350,000 for a reservoir engineering study.

* A $17 million loan to Cameroon to increase fuelwood and pulpwood production. A plantation to supply raw material for the pulp industry will be established and a total of 11,000 hectares will be planted with pine and eucalyptus, both rapidly growing species. The government agencies responsible for forestry taxes and royalties will be provided with transport and operating funds. Specialists in plantation management will assist reforestation programs.

* A $77 million loan will be used by the Colombian National Railways for rehabilitation work and to strengthen its operations. The loan will help finance a $176.7 million project covering the first four years of a five-year rehabilitation program. In addition, the United Nations Development Program will provide $1 million in technical assistance.

Export-Import Bank

* A loan of $75.7 million to support a $116.5 million purchase of U.S. equipment for modernization of a copper mine in the Mexican state Sonora. Parsons International of California is expected to be the construction manager for the project. Other U.S. suppliers will provide heavy duty mining equipment and crushing and grinding equipment.

* A $10.5 million credit to support expansion of a sugar mill complex owned by a Colombian sugar producer. Emhart Corp.'s Farrel Connecticut Division, of Ansonia, Conn. will be the major U.S. supplier. Other American manufacturers and suppliers will provide ancillary and field equipment.

* An $8.25 million credit to support an $11 million contract between the Fuller Co., of Bethlehem, Pa. and Century Spinning & Manufacturing Co., of Bombay, India. The Fuller Co. will provide cement equipment and services to be used in construction of a dry process cement plant.International Monetary Fund

* The IMF has agreed to a purchase equivalent of 60 million special drawing rights by the government of Bangladesh to compensate for a shortfall in export earnings experienced by the country in the 12-month period ending in March, 1982. The shortfall derives mainly from lower prices of raw jute and jute products, which account for almost 70 percent of Bangladesh's total exports.

Asian Development Bank

* Consultant services will be provided to help formulate and prepare a smallholder livestock development project in Thailand. The project is aimed at increasing beef and dairy cattle production, including quality beef, for domestic and export markets, and at providing support to milk production and animal health improvement.

A technical assistance grant for the preparation of a rural development project in the Kushtia, Rajshahi and Pabna districts in northwestern Bangladesh. The study will focus on agriculture, fisheries, livestock, rural industries and institutional development including cooperatives and related support services and minor irrigation.

* A technical assistance grant for conducting the sixth regional program on development banking in collaboration with the Development Banking Centre of India's Management Development Institute, to be held in New Delhi, March 5 to April 23. Professional staff from 28 development finance institutions in 12 developing member countries will be invited to take part. The aim of the program is to strengthen the analytical skills of staff directly engaged in project appraisal, follow-up and supervision.